The SAGE Encyclopedia of Stem Cell Research (3 Volumes) [1-3, 2 ed.] 9781483347684

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The SAGE Encyclopedia of

STEM CELL RESEARCH

SAGE was founded in 1965 by Sara Miller McCune to support the dissemination of usable knowledge by publishing innovative and high-quality research and teaching content. Today, we publish more than 850 journals, including those of more than 300 learned societies, more than 800 new books per year, and a growing range of library products including archives, data, case studies, reports, conference highlights, and video. SAGE remains majority-owned by our founder, and after Sara’s lifetime will become owned by a charitable trust that secures our continued independence. L o s A n g e l e s | L o n d o n | N ew D e l h i | S i n g a p o r e | Wa s h i n g to n D C

2nd EDITION

The SAGE Encyclopedia of

STEM CELL RESEARCH Volume 1 Eric E. Bouhassira, PhD/Editor Albert Einstein College of Medicine

Krishna S. Vyas, MD/Associate Editor University of Kentucky College of Medicine

FOR INFORMATION: SAGE Publications, Inc. 2455 Teller Road Thousand Oaks, California 91320 E-mail: [email protected] SAGE Publications India Pvt. Ltd. B 1/I 1 Mohan Cooperative Industrial Area Mathura Road, New Delhi 110 044 India

Copyright © 2015 by SAGE Publications, Inc. All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher.

SAGE Publications Ltd. 1 Oliver’s Yard 55 City Road London EC1Y 1SP United Kingdom SAGE Publications Asia-Pacific Pte. Ltd. 3 Church Street #10-04 Samsung Hub Singapore 049483

Library of Congress Cataloging-in-Publication Data Encyclopedia of stem cell research. The SAGE encyclopedia of stem cell research / Eric Bouhassira, editor ; Krishna S. Vyas, associate editor. —2nd edition. p. ; cm. Preceded by Encyclopedia of stem cell research / general editors, Clive N. Svendsen, Allison D. Ebert. c2008. Includes bibliographical references and index.

Executive Editor:  Jim Brace-Thompson Production Editors: TLK Editing Services, Jane Haenel Reference Systems Manager:  Leticia Gutierrez Reference Systems Coordinator:  Anna Villasenor Author Manager:  Sarah Boslaugh Copyeditors: Terry Buck, Jim Corrick, Janet Ford, Julie Henderson, Rebecca Kuzins, Barbara Paris, Terri Paulsen Typesetter:  C&M Digitals (P) Ltd. Proofreaders:  Susan Schon, Pam Suwinsky Indexer:  J S Editorial Cover Designer:  Candice Harman Marketing Manager:  Teri Williams

ISBN 978-1-4833-4768-4 (hardcover : alk. paper) I. Bouhassira, Eric, editor. II. Vyas, Krishna S., editor. III. Title. [DNLM: 1. Stem Cells—Encyclopedias—English. QU 13] QH588.S83 616’.02774—dc23   2015011206

15 16 17 18 19 10 9 8 7 6 5 4 3 2 1

Contents Volume 1 List of Articles vii Reader’s Guide xv About the Editor xxii List of Contributors xxiii Introduction xxix Chronology xxxiii A 1 B 73 C 163 D 333

Articles E 369 F 405 G 429

Volume 2 List of Articles vii Articles H 497 I 553 J 613 K 625 L 657

M 719 N 809 O 881 P 897 R 965

Volume 3 List of Articles vii Articles S 993 T 1131 U 1167 V 1249

W 1269 X 1291 Y 1297 Z 1303

Glossary 1307 Resource Guide 1315 Appendix A. Executive Order 13435 Appendix B. Executive Order 13505 Appendix C. S. HRG. 111-942 Index 1403

1322 1326 1328

List of Articles A Aastrom Biosciences, Inc. Adipose: Cell Types Composing the Tissue Adipose: Current Research on Isolation or Production of Therapeutic Cells Adipose: Development and Regeneration Potential Adipose: Existing or Potential Regenerative Medicine Strategies Adipose: Major Pathologies Adipose: Stem and Progenitor Cells in Adults Adipose: Tissue Function Adult Stem Cells: Overview Advanced Cell Technology Advocacy Alabama Alaska Albert Einstein College of Medicine Alvarez-Buylla, Arturo Alzheimer’s Disease American Association for the Advancement of Science Amniotic Fluid Cells Animal Cloning Anversa, Piero Arizona Arkansas Athersys Australia Autism

Autonomous University of Barcelona Autonomous University of Madrid B Baylor University Beike Biotechnology Belgium Bioreactors Bladder: Cell Types Composing the Tissue Bladder: Current Research on Isolation or Production of Therapeutic Cells Bladder: Development and Regeneration Potential Bladder: Existing or Potential Regenerative Medicine Strategies Bladder: Major Pathologies Bladder: Stem and Progenitor Cells in Adults Blood Adult Stem Cell: Current Research on Isolation or Production of Therapeutic Cells Blood Adult Stem Cell: Development and Regeneration Potential Blood Adult Stem Cell: Existing or Potential Regenerative Medicine Strategies Blood Adult Stem Cell: Major Pathologies Blood Adult Stem Cell: Stem and Progenitor Cells in Adults Bone: Cell Types Composing the Tissue Bone: Current Research on Isolation or Production of Therapeutic Cells vii

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List of Articles

Bone: Development and Regeneration Potential Bone: Existing or Potential Regenerative Medicine Strategies Bone: Major Pathologies Bone: Stem and Progenitor Cells in Adults Bone Marrow Transplants Boston Children’s Hospital Brain Cancer Brazil Breast: Cell Types Composing the Tissue Breast: Current Research on Isolation or Production of Therapeutic Cells Breast: Development and Regeneration Potential Breast: Existing or Potential Regenerative Medicine Strategies Breast: Major Pathologies Breast: Stem and Progenitor Cells in Adults Breast Cancer Buddhism C C. elegans Models to Study Stem Cells California California Institute for Regenerative Medicine California Stem Cell, Inc. Canada: Stem Cell Network Cancer Stem Cells: Overview Cartilage, Tendons, and Ligaments: Cell Types Composing the Tissue Cartilage, Tendons, and Ligaments: Current Research on Isolation or Production of Therapeutic Cells Cartilage, Tendons, and Ligaments: Development and Regeneration Potential Cartilage, Tendons, and Ligaments: Existing or Potential Regenerative Medicine Strategies Cartilage, Tendons, and Ligaments: Major Pathologies Cartilage, Tendons, and Ligaments: Stem and Progenitor Cells in Adults Case Western Reserve University/Cleveland Clinic Catholicism Cellerant Therapeutics Charo, Alta Chimera Formation, Ethics of China Christianity

Christopher & Dana Reeve Foundation, The Clinical Trials, Ethics of Clinical Trials (Adult Cells), Ethics of Clinical Trials, U.S.: AIDS-Related Conditions Clinical Trials, U.S.: Amyotrophic Lateral Sclerosis Clinical Trials, U.S.: Batten Disease Clinical Trials, U.S.: Blood Deficiencies Clinical Trials, U.S.: Crohn’s Disease Clinical Trials, U.S.: Diabetes Clinical Trials, U.S.: Eye Conditions Clinical Trials, U.S.: Graft Failure, Graft-VersusHost Disease Clinical Trials, U.S.: Heart Disease Clinical Trials, U.S.: Hematological Cancers Clinical Trials, U.S.: Immunologic/Histiocytic Disorders Clinical Trials, U.S.: Kidney Disease Clinical Trials, U.S.: Multiple Sclerosis Clinical Trials, U.S.: Parkinson’s Disease Clinical Trials, U.S.: Peripheral Vascular Disease Clinical Trials, U.S.: Skin Transplants Clinical Trials, U.S.: Solid Tumors Clinical Trials, U.S.: Spinal Cord Injury Clinical Trials, U.S.: Stroke Clinical Trials, U.S.: Traumatic Brain Injury Clinical Trials Outside the United States Clinical Trials Outside the United States: Amyotrophic Lateral Sclerosis Clinical Trials Outside the United States: Cerebral Palsy Clinical Trials Outside the United States: Spinal Cord Injury Clinical Trials Outside the United States: Stroke Cloning, Ethics of Colon Cancer Colorado Columbia University Congress: Votes and Amendments Connecticut Cord Blood Banking Cord Blood Stem Cells Coriell Institute for Medical Research Cosmetic Surgery Cryo-Cell International Cryo-Save Cytori Therapeutics, Inc.



D Danish Stem Cell Center Delaware Denmark Dental: Current Research on Isolation or Production of Therapeutic Cells Dental: Development and Regeneration Potential Dental: Existing or Potential Regenerative Medicine Strategies Dental: Major Pathologies Dental: Stem and Progenitor Cells in Adults Direct Reprogramming of Adult Cells Into Other Cell Types Do No Harm: The Coalition of Americans for Research Ethics Drosophila Models to Study Stem Cells Drug Testing and Drug Development in Cell Culture Duke University E Egg Donation, Ethics of Embryonic Stem Cells, Methods to Produce Endothelial Blood Vessels Endothelial Cell Isolation ES Cell International ESC and iPSC Banking EuroStemCell Eyes: Cell Types Composing the Tissue Eyes: Current Research on Isolation or Production of Therapeutic Cells Eyes: Development and Regeneration Potential Eyes: Existing or Potential Regenerative Medicine Strategies Eyes: Major Pathologies Eyes: Stem and Progenitor Cells in Adults Eyes: Tissue Function F Fate Therapeutics Fertility Treatment Creation of Germ Cells From Adult Cells Fetal Stem Cells Florida Fluorescence-Activated Cell Sorting Food From Stem Cells France Frenette, Paul Fuchs, Elaine

List of Articles

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G Gene Patents Gene Therapy: Hemoglobinopathies Genetics Policy Institute Genome Sequencing Genome Sequencing, Ethics of Georgia Germ Cell Modifications (Gene Therapy), Ethics of Germany Geron Corporation Goldman, Steven A. Gonads, Female: Cell Types Composing the Tissue Gonads, Female: Current Research on Isolation or Production of Therapeutic Cells Gonads, Female: Development and Regeneration Potential Gonads, Female: Major Pathologies Gonads, Female: Stem and Progenitor Cells in Adults Gonads, Male: Cell Types Composing the Tissue Gonads, Male: Current Research on Isolation or Production of Therapeutic Cells Gonads, Male: Development and Regeneration Potential Gonads, Male: Existing or Potential Regenerative Medicine Strategies Gonads, Male: Major Pathologies Gonads, Male: Stem and Progenitor Cells in Adults Graft Failure: Graft-Versus-Host Disease Gut: Current Research on Isolation or Production of Therapeutic Cells Gut: Development and Regeneration Potential Gut: Existing or Potential Regenerative Medicine Strategies Gut: Major Pathologies Gut: Stem and Progenitor Cells in Adults H Harvard University Hawai‘i Head and Neck Cancer Hearing Disease Heart: Cell Types Composing the Tissue Heart: Current Research on Isolation or Production of Therapeutic Cells

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List of Articles

Heart: Development and Regeneration Potential Heart: Existing or Potential Regenerative Medicine Strategies Heart: Major Pathologies Heart: Stem and Progenitor Cells in Adults Heart: Tissue Function Heart Disease Hebrew University of Jerusalem Hematopoietic Transplantation: Cancer Hematopoietic Transplantation: Gene Therapy Hochedlinger, Konrad Howard Hughes Medical Institute Human ES Cell Isolation I Idaho Illinois Immune Disorders In Utero Treatment In Vitro Fertilization In Vitro Production of Germ Cells, Ethics of In Vitro Stem Cell Study Assays In Vivo Stem Cell Study Assays India Indiana Indiana University International Society for Stem Cell Research International Society for Stem Cell Research Guidelines International Stem Cell Corporation International Stem Cell Forum Iowa iPS, Methods to Produce iPS Tissue Sources iPSC From Animal Cells Iran Italy J Japan Japan Human Cell Society Johns Hopkins University Judaism K Kansas Karolinska Institute Kentucky Kidney: Cell Types Composing the Tissue

Kidney: Current Research on Isolation or Production of Therapeutic Cell Kidney: Development and Regeneration Potential Kidney: Existing or Potential Regenerative Medicine Strategies Kidney: Major Pathologies Kidney: Stem and Progenitor Cells in Adults Kidney Disease Korea Kyoto University L Langer, Robert Lasker Foundation Lentigen Corporation Leukemia and Lymphoma Cancer Stem Cells Lineage Tracing Liver: Cell Types Composing the Tissue Liver: Current Research on Isolation or Production of Therapeutic Cells Liver: Development and Regeneration Potential Liver: Existing or Potential Regenerative Medicine Strategies Liver: Major Pathologies Liver: Stem and Progenitor Cells in Adults Liver: Tissue Function Liver Cancer Losordo, Douglas Louisiana Lung: Cell Types Composing the Tissue Lung: Current Research on Isolation or Production of Therapeutic Cells Lung: Development and Regeneration Potential Lung: Existing or Potential Regenerative Medicine Strategies Lung: Major Pathologies Lung: Stem and Progenitor Cells in Adults Lung: Tissue Function Lung Cancer Lung Disease M Maine Martino, Gianvito Maryland Massachusetts Massachusetts General Hospital Massachusetts Institute of Technology Max Planck Society



Mayo Clinic McCulloch, Ernest McMaster University Medical Research Council (UK) Melanoma: Stem Cells Mesenchymal: Cell Types Composing the Tissue Mesenchymal: Current Research on Isolation or Production of Therapeutic Cells Mesenchymal: Development and Regeneration Potential Mesenchymal: Existing or Potential Regenerative Medicine Strategies Mesenchymal: Major Pathologies Mesenchymal: Stem and Progenitor Cells in Adults Mesenchymal Stem Cells Michael J. Fox Foundation Michigan Minnesota Mississippi Missouri Montana Moral Status of Embryos Mount Sinai School of Medicine Mouse ES Cell Isolation Mouse Models to Study Stem Cells MRI Tracking Muscle: Cell Types Composing the Tissue Muscle: Current Research on Isolation or Production of Therapeutic Cells Muscle: Development and Regeneration Potential Muscle: Existing or Potential Regenerative Medicine Strategies Muscle: Major Pathologies Muscle: Stem and Progenitor Cells in Adults Muslim N National Academy of Sciences National Institutes of Health National Right to Life Committee National Science Foundation National Stem Cell Bank Nebraska NeoStem, Inc. Netherlands Neural: Cell Types Composing the Tissue Neural: Current Research on Isolation or Production of Therapeutic Cells

List of Articles Neural: Development and Regeneration Potential Neural: Existing or Potential Regenerative Medicine Strategies Neural: Major Pathologies Neural: Stem and Progenitor Cells in Adults Neuralstem, Inc. Nevada New Biotech: Overview New Hampshire New Jersey New Mexico New York New York Stem Cell Foundation Non-Human Primate Embryonic Stem Cells North Carolina North Dakota Northwestern University Norway Nuclear Transfer, Altered Nuclear Transfer, Somatic Cell O Ohio Oklahoma Oregon Oregon Health & Science University Orkin, Stuart Ottawa Hospital Research Institute P Pancreas: Cell Types Composing the Tissue Pancreas: Current Research on Isolation or Production of Therapeutic Cells Pancreas: Development and Regeneration Potential Pancreas: Existing or Potential Regenerative Medicine Strategies Pancreas: Major Pathologies Pancreas: Stem and Progenitor Cells in Adults Pancreas: Tissue Function Pancreatic Cancer Pancreatic Islet Transplant Parcell Laboratories Parkinson’s Disease Parkinson’s Disease Foundation Parthenogenesis Pasteur Institute Pathfinder Cell Therapy Peking University

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List of Articles

Pennsylvania Pera, Martin Pluripotency Network Pluripotent Stem Cell Patents Pluripotent Stem Cells, Embryonic Pluripotent Stem Cells, Epi Pluripotent Stem Cells, Germ Pluripotent Stem Cells, Teratoma Preimplantation Genetic Diagnosis President’s Council on Bioethics Princeton University Profiling Study Methods R Radiation Injury Treatment Rafii, Shahin Rao, Mahendra Rat Models to Study Stem Cells Reeve-Irvine Research Center Reproductive and Therapeutic Cloning Retinal Stem Cells Reynolds, Brent A., and Samuel Weiss Rhode Island Robarts Research Institute Rockefeller University Rutgers University S Sanford-Burnham Medical Research Institute Saudi Arabia Scadden, David Schizophrenia Scripps Research Institute Scotland: Stem Cell Research and Regenerative Medicine Self-Renewal and Differentiation Singapore Skin: Cell Types Composing the Tissue Skin: Current Research on Isolation or Production of Therapeutic Cells Skin: Development and Regeneration Potential Skin: Existing or Potential Regenerative Medicine Strategies Skin: Major Pathologies Skin: Stem and Progenitor Cells in Adults Skin: Tissue Function Skin Cancer Skin Graft Sloan Kettering Institute Snyder, Evan

South Carolina South Dakota Spain Special Interest/Lobby Groups Spinal Cord Injury Stanford University Steindler, Dennis Stem Cell Aging Stem Cell Banking Stem Cell Companies: Overview Stem Cell Differentiation/Self-Organization Stem Cell DNA Repair Stem Cell Epigenetic: Chromatin Modification Stem Cell Epigenetic: DNA Methylation Stem Cell Epigenetic: DNA Replication Stem Cell Expression Profiling Stem Cell Genetic Modification Study Method Stem Cell Genome Anatomy Projects Stem Cell Ground State Stem Cell Histocompatibility Stem Cell Markers Stem Cell Network North Rhine Westphalia Stem Cell Niche Stem Cell Plasticity Stem Cell Potency Stem Cell Purification Stem Cells: Bush Ruling Stemagen Stematix Stowers Institute for Medical Research Studer, Lorenz Sweat Gland: Cell Types Composing the Tissue Sweat Gland: Current Research on Isolation or Production of Therapeutic Cells Sweat Gland: Development and Regeneration Potential Sweat Gland: Existing or Potential Regenerative Medicine Strategies Sweat Gland: Major Pathologies Sweat Gland: Stem and Progenitor Cells in Adults Sweden Swiss Stem Cells Network Switzerland T Taiwan Tennessee Texas Thomson, James

List of Articles



TiGenix/Cellerix Till, James Tissue Culture Study Methods Tissue Engineering (Scaffold) Tissue Printing Tissue Regeneration: Animals and Plants Tissue Regeneration: Humans Transfusion Product: NK Cells Transfusion Product: Platelets Transfusion Product: Red Blood Cells Transit Amplifying Cells U UK National Stem Cell Network Unapproved Therapy, Ethics of United Kingdom United States University of Bonn University of British Columbia University of California, Berkeley University of California, Davis University of California, Los Angeles University of California, San Diego University of California, San Francisco University of Cambridge University of Connecticut University of Heidelberg University of Melbourne University of Miami University of Michigan University of Milan University of Minnesota University of North Carolina at Chapel Hill University of Oxford University of Pittsburgh University of Southern California University of Strasbourg University of Texas Health Science Center at Houston University of Tokyo University of Toronto

University of Washington/Fred Hutchinson Cancer Research Center University of Wisconsin–Madison University Pierre et Marie Curie, Paris Utah V van der Kooy, Derek Vanderbilt University Vascular Stem Cell Vermont Vescovi, Angelo ViaCyte, Inc. Viral Vectors: Adenovirus Viral Vectors: Lentivirus Virginia W Wake Forest University Washington Weill Cornell Medical College Weissman, Irving Weizmann Institute of Science West Virginia Whitehead Institute for Biomedical Research WiCell Wisconsin Wound Repair Wyoming X Xenopus Models to Study Stem Cells Xenotransplantation Y Yale University Yamanaka, Shinya Z Zebrafish Models to Study Stem Cells

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Reader’s Guide Adult Stem Cells Adipose: Cell Types Composing the Tissue Adipose: Current Research on Isolation or Production of Therapeutic Cells Adipose: Development and Regeneration Potential Adipose: Existing or Potential Regenerative Medicine Strategies Adipose: Major Pathologies Adipose: Stem and Progenitor Cells in Adults Adipose: Tissue Function Adult Stem Cells: Overview Bladder: Cell Types Composing the Tissue Bladder: Current Research on Isolation or Production of Therapeutic Cells Bladder: Development and Regeneration Potential Bladder: Existing or Potential Regenerative Medicine Strategies Bladder: Major Pathologies Bladder: Stem and Progenitor Cells in Adults Blood Adult Stem Cell: Current Research on Isolation or Production of Therapeutic Cells Blood Adult Stem Cell: Development and Regeneration Potential Blood Adult Stem Cell: Existing or Potential Regenerative Medicine Strategies Blood Adult Stem Cell: Major Pathologies Blood Adult Stem Cell: Stem and Progenitor Cells in Adults

Bone: Cell Types Composing the Tissue Bone: Current Research on Isolation or Production of Therapeutic Cells Bone: Development and Regeneration Potential Bone: Existing or Potential Regenerative Medicine Strategies Bone: Major Pathologies Bone: Stem and Progenitor Cells in Adults Breast: Cell Types Composing the Tissue Breast: Current Research on Isolation or Production of Therapeutic Cells Breast: Development and Regeneration Potential Breast: Existing or Potential Regenerative Medicine Strategies Breast: Major Pathologies Breast: Stem and Progenitor Cells in Adults Cartilage, Tendons, and Ligaments: Cell Types Composing the Tissue Cartilage, Tendons, and Ligaments: Current Research on Isolation or Production of Therapeutic Cells Cartilage, Tendons, and Ligaments: Development and Regeneration Potential Cartilage, Tendons, and Ligaments: Existing or Potential Regenerative Medicine Strategies Cartilage, Tendons, and Ligaments: Major Pathologies Cartilage, Tendons, and Ligaments: Stem and Progenitor Cells in Adults xv

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Reader’s Guide

Dental: Current Research on Isolation or Production of Therapeutic Cells Dental: Development and Regeneration Potential Dental: Existing or Potential Regenerative Medicine Strategies Dental: Major Pathologies Dental: Stem and Progenitor Cells in Adults Eyes: Cell Types Composing the Tissue Eyes: Current Research on Isolation or Production of Therapeutic Cells Eyes: Development and Regeneration Potential Eyes: Existing or Potential Regenerative Medicine Strategies Eyes: Major Pathologies Eyes: Stem and Progenitor Cells in Adults Eyes: Tissue Function Gonads, Female: Cell Types Composing the Tissue Gonads, Female: Current Research on Isolation or Production of Therapeutic Cells Gonads, Female: Development and Regeneration Potential Gonads, Female: Major Pathologies Gonads, Female: Stem and Progenitor Cells in Adults Gonads, Male: Cell Types Composing the Tissue Gonads, Male: Current Research on Isolation or Production of Therapeutic Cells Gonads, Male: Development and Regeneration Potential Gonads, Male: Existing or Potential Regenerative Medicine Strategies Gonads, Male: Major Pathologies Gonads, Male: Stem and Progenitor Cells in Adults Graft Failure: Graft-Versus-Host Disease Gut: Current Research on Isolation or Production of Therapeutic Cells Gut: Development and Regeneration Potential Gut: Existing or Potential Regenerative Medicine Strategies Gut: Major Pathologies Gut: Stem and Progenitor Cells in Adults Heart: Cell Types Composing the Tissue Heart: Current Research on Isolation or Production of Therapeutic Cells Heart: Development and Regeneration Potential Heart: Existing or Potential Regenerative Medicine Strategies Heart: Major Pathologies

Heart: Stem and Progenitor Cells in Adults Heart: Tissue Function Kidney: Cell Types Composing the Tissue Kidney: Current Research on Isolation or Production of Therapeutic Cells Kidney: Development and Regeneration Potential Kidney: Existing or Potential Regenerative Medicine Strategies Kidney: Major Pathologies Kidney: Stem and Progenitor Cells in Adults Liver: Cell Types Composing the Tissue Liver: Current Research on Isolation or Production of Therapeutic Cells Liver: Development and Regeneration Potential Liver: Existing or Potential Regenerative Medicine Strategies Liver: Major Pathologies Liver: Stem and Progenitor Cells in Adults Liver: Tissue Function Lung: Cell Types Composing the Tissue Lung: Current Research on Isolation or Production of Therapeutic Cells Lung: Development and Regeneration Potential Lung: Existing or Potential Regenerative Medicine Strategies Lung: Major Pathologies Lung: Stem and Progenitor Cells in Adults Lung: Tissue Function Mesenchymal: Cell Types Composing the Tissue Mesenchymal: Current Research on Isolation or Production of Therapeutic Cells Mesenchymal: Development and Regeneration Potential Mesenchymal: Existing or Potential Regenerative Medicine Strategies Mesenchymal: Major Pathologies Mesenchymal: Stem and Progenitor Cells in Adults Muscle: Cell Types Composing the Tissue Muscle: Current Research on Isolation or Production of Therapeutic Cells Muscle: Development and Regeneration Potential Muscle: Existing or Potential Regenerative Medicine Strategies Muscle: Major Pathologies Muscle: Stem and Progenitor Cells in Adults



Neural: Cell Types Composing the Tissue Neural: Current Research on Isolation or Production of Therapeutic Cells Neural: Development and Regeneration Potential Neural: Existing or Potential Regenerative Medicine Strategies Neural: Major Pathologies Neural: Stem and Progenitor Cells in Adults Pancreas: Cell Types Composing the Tissue Pancreas: Current Research on Isolation or Production of Therapeutic Cells Pancreas: Development and Regeneration Potential Pancreas: Existing or Potential Regenerative Medicine Strategies Pancreas: Major Pathologies Pancreas: Stem and Progenitor Cells in Adults Pancreas: Tissue Function Skin: Cell Types Composing the Tissue Skin: Current Research on Isolation or Production of Therapeutic Cells Skin: Development and Regeneration Potential Skin: Existing or Potential Regenerative Medicine Strategies Skin: Major Pathologies Skin: Stem and Progenitor Cells in Adults Skin: Tissue Function Sweat Gland: Cell Types Composing the Tissue Sweat Gland: Current Research on Isolation or Production of Therapeutic Cells Sweat Gland: Development and Regeneration Potential Sweat Gland: Existing or Potential Regenerative Medicine Strategies Sweat Gland: Major Pathologies Sweat Gland: Stem and Progenitor Cells in Adults Vascular Stem Cell Animal Models to Study Stem Cells C. elegans Models to Study Stem Cells Drosophila Models to Study Stem Cells Mouse Models to Study Stem Cells Rat Models to Study Stem Cells Xenopus Models to Study Stem Cells Zebrafish Models to Study Stem Cells Cancer Stem Cells Brain Cancer Breast Cancer

Reader’s Guide Cancer Stem Cells: Overview Colon Cancer Head and Neck Cancer Leukemia and Lymphoma Cancer Stem Cells Liver Cancer Lung Cancer Melanoma: Stem Cells Pancreatic Cancer Skin Cancer Clinical Trials in the United States Clinical Trials, U.S.: AIDS-Related Conditions Clinical Trials, U.S.: Amyotrophic Lateral Sclerosis Clinical Trials, U.S.: Batten Disease Clinical Trials, U.S.: Blood Deficiencies Clinical Trials, U.S.: Crohn’s Disease Clinical Trials, U.S.: Diabetes Clinical Trials, U.S.: Eye Conditions Clinical Trials, U.S.: Graft Failure, Graft-Versus-Host Disease Clinical Trials, U.S.: Heart Disease Clinical Trials, U.S.: Hematological Cancers Clinical Trials, U.S.: Immunologic/Histiocytic Disorders Clinical Trials, U.S.: Kidney Disease Clinical Trials, U.S.: Multiple Sclerosis Clinical Trials, U.S.: Parkinson’s Disease Clinical Trials, U.S.: Peripheral Vascular Disease Clinical Trials, U.S.: Skin Transplants Clinical Trials, U.S.: Solid Tumors Clinical Trials, U.S.: Spinal Cord Injury Clinical Trials, U.S.: Stroke Clinical Trials, U.S.: Traumatic Brain Injury Clinical Trials Worldwide Clinical Trials Outside the United States Clinical Trials Outside the United States: Amyotrophic Lateral Sclerosis Clinical Trials Outside the United States: Cerebral Palsy Clinical Trials Outside the United States: Spinal Cord Injury Clinical Trials Outside the United States: Stroke

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Reader’s Guide

Cloning Animal Cloning Reproductive and Therapeutic Cloning Countries Australia Belgium Brazil China Denmark France Germany India Iran Italy Japan Korea Netherlands Norway Saudi Arabia Singapore Spain Sweden Switzerland Taiwan United Kingdom United States Ethics Chimera Formation, Ethics of Clinical Trials, Ethics of Clinical Trials (Adult Cells), Ethics of Cloning, Ethics of Egg Donation, Ethics of Genome Sequencing, Ethics of Germ Cell Modifications (Gene Therapy), Ethics of In Vitro Production of Germ Cells, Ethics of Moral Status of Embryos Unapproved Therapy, Ethics of In Vitro Organ Regeneration Tissue Engineering (Scaffold) Tissue Printing Industry Aastrom Biosciences, Inc. Advanced Cell Technology Athersys

Beike Biotechnology California Stem Cell, Inc. Cellerant Therapeutics Cryo-Cell International Cryo-Save Cytori Therapeutics, Inc. ES Cell International Fate Therapeutics Geron Corporation International Stem Cell Corporation Lentigen Corporation NeoStem, Inc. Neuralstem, Inc. New Biotech: Overview Parcell Laboratories Pathfinder Cell Therapy Stem Cell Companies: Overview Stemagen Stematix TiGenix/Cellerix ViaCyte, Inc. Institutions Albert Einstein College of Medicine Autonomous University of Barcelona Autonomous University of Madrid Baylor University Boston Children’s Hospital California Institute for Regenerative Medicine Case Western Reserve University/ Cleveland Clinic Columbia University Coriell Institute for Medical Research Duke University Genetics Policy Institute Harvard University Hebrew University of Jerusalem Howard Hughes Medical Institute Indiana University Johns Hopkins University Karolinska Institute Kyoto University Massachusetts General Hospital Massachusetts Institute of Technology Max Planck Society Mayo Clinic McMaster University Mount Sinai School of Medicine



National Academy of Sciences Northwestern University Oregon Health & Science University Ottawa Hospital Research Institute Pasteur Institute Peking University Princeton University Reeve-Irvine Research Center Robarts Research Institute Rockefeller University Rutgers University Sanford-Burnham Medical Research Institute Scripps Research Institute Sloan Kettering Institute Stanford University Stowers Institute for Medical Research University of Bonn University of British Columbia University of California, Berkeley University of California, Davis University of California, Los Angeles University of California, San Diego University of California, San Francisco University of Cambridge University of Connecticut University of Heidelberg University of Melbourne University of Miami University of Michigan University of Milan University of Minnesota University of North Carolina at Chapel Hill University of Oxford University of Pittsburgh University of Southern California University of Strasbourg University of Texas Health Science Center at Houston University of Tokyo University of Toronto University of Washington/Fred Hutchinson Cancer Research Center University of Wisconsin–Madison University Pierre et Marie Curie, Paris Vanderbilt of University Wake Forest University Weill Cornell Medical College Weizmann Institute of Science Whitehead Institute for Biomedical Research Yale University

Reader’s Guide

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Large-Scale Stem Cell Production for Clinical Application Bioreactors Xenotransplantation Legal Issues Gene Patents International Society for Stem Cell Research Guidelines Pluripotent Stem Cell Patents Methods to Study Stem Cells Bone Marrow Transplants Direct Reprogramming of Adult Cells Into Other Cell Types Endothelial Cell Isolation Fluorescence-Activated Cell Sorting Genome Sequencing Human ES Cell Isolation In Vitro Fertilization In Vitro Stem Cell Study Assays In Vivo Stem Cell Study Assays Lineage Tracing Mouse ES Cell Isolation MRI Tracking Non-Human Primate Embryonic Stem Cells Nuclear Transfer, Altered Nuclear Transfer, Somatic Cell Parthogenesis Preimplantation Genetic Diagnosis Profiling Study Methods Stem Cell Epigenetic: Chromatin Modification Stem Cell Epigenetic: DNA Methylation Stem Cell Epigenetic: DNA Replication Stem Cell Expression Profiling Stem Cell Genetic Modification Study Method Stem Cell Markers Stem Cell Purification Tissue Culture Study Methods Viral Vectors: Adeonvirus Viral Vectors: Lentivirus Non-Pluripotent, Non-Adult Stem Cells Amniotic Fluid Cells Cord Blood Stem Cells Fetal Stem Cells Mesenchymal Stem Cells

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Reader’s Guide

Organizations American Association for the Advancement of Science California Institute for Regenerative Medicine Canada: Stem Cell Network Christopher & Dana Reeve Foundation, The Danish Stem Cell Research EuroStemCell Howard Hughes Medical Institute International Society for Stem Cell Research International Stem Cell Forum Japan Human Cell Society Lasker Foundation Medical Research Council (UK) Michael J. Fox Foundation National Institutes of Health National Science Foundation National Stem Cell Bank New York Stem Cell Foundation Parkinson’s Disease Foundation Scotland: Stem Cell Research and Regenerative Medicine Stem Cell Genome Anatomy Projects Stem Cell Network North Rhine Westphalia Swiss Stem Cells Network UK National Stem Cell Network WiCell People Alvarez-Buylla, Arturo Anversa, Piero Charo, Alta Frenette, Paul Fuchs, Elaine Goldman, Steven A. Hochedlinger, Konrad Langer, Robert Losordo, Douglas Martino, Gianvito McCulloch, Ernest Orkin, Stuart Pera, Martin Rafii, Shahin Rao, Mahendra Reynolds, Brent A., and Samuel Weiss Scadden, David Snyder, Evan Steindler, Dennis Studer, Lorenz Thomson, James

Till, James van der Kooy, Derek Vescovi, Angelo Weissman, Irving Yamanaka, Shinya Pluripotent Stem Cells Embryonic Stem Cells, Methods to Produce iPS, Methods to Produce iPS Tissue Sources iPSC From Animal Cells Pluripotency Network Pluripotent Stem Cells, Embryonic Pluripotent Stem Cells, Epi Pluripotent Stem Cells, Germ Pluripotent Stem Cells, Teratoma Politics Advocacy Congress: Votes and Amendments Do No Harm: The Coalition of Americans for Research Ethics National Right to Life Committee President’s Council on Bioethics Special Interest/Lobby Groups Stem Cells: Bush Ruling Religion Buddhism Catholicism Christianity Judaism Muslim Stem Cell Applications Alzheimer’s Disease Animal Cloning Autism Cord Blood Banking Cosmetic Surgery Drug Testing and Drug Development in Cell Culture Endothelial Blood Vessels ESC and iPSC Banking Fertility Treatment Creation of Germ Cells From Adult Cells Food From Stem Cells Gene Therapy: Hemoglobinopathies Graft Failure: Graft-Versus-Host Disease Hearing Disease

Reader’s Guide



Heart Disease Hematopoietic Transplantation: Cancer Hematopoietic Transplantation: Gene Therapy Immune Disorders In Utero Treatment Kidney Disease Lung Disease Pancreatic Islet Transplant Parkinson’s Disease Radiation Injury Treatment Retinal Stem Cells Schizophrenia Skin Graft Spinal Cord Injury Stem Cell Banking Transfusion Product: NK Cells Transfusion Product: Platelets Transfusion Product: Red Blood Cells Wound Repair Stem Cell Biology Self-Renewal and Differentiation Stem Cell Aging Stem Cell Differentiation/Self-Organization Stem Cell DNA Repair Stem Cell Ground State Stem Cell Histocompatibility Stem Cell Niche Stem Cell Plasticity Stem Cell Potency Tissue Regeneration: Animals and Plants Tissue Regeneration: Humans Transit Amplifying Cells U.S. States Alabama Alaska Arizona Arkansas California Colorado Connecticut

Delaware Florida Georgia Hawai’i Idaho Illinois Indiana Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming

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About the Editor Eric E. Bouhassira, PhD, is a professor at the Albert Einstein College of Medicine in the Department of Cell Biology, the Department of Medicine (Hematology) and is also the Ingeborg and Ira Leon Rennert Professor of Stem Cell Biology and Regenerative Medicine. Dr. Bouhassira joined the Albert Einstein College of Medicine in 1990. He began studying human embryonic stem cells in 2001 and was the organizing force behind the three-year, $3 million grant for human embryonic stem cell r-research that Einstein received from the National Institutes of Health in 2005. He is

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director of the medical school’s Center for Human Embryonic Stem Cell Research and professor of medicine and of cell biology. Dr. Bouhassira’s research focuses on developing hematopoietic (blood forming) stem cells that can differentiate into red cells, T cells, platelets, and all other cell types that comprise blood. This work could potentially aid patients needing transfusions and also save lives by expanding the immunology diversity of hematopoietic stem cells available for transplant. Dr. Bouhassira received his BS, MS, and PhD degrees from the Université Pierre et Marie Curie in Paris, France, in 1989.

List of Contributors Amara Abid Staten Island University Sidrah Abid Independent Scholar Mohammad Zainul Abideen Independent Scholar Noor-ul-ain Ahmad Independent Scholar Mamoon Ahmed Army Medical College, National University of Sciences and Technology Syed Arsalan Ahmed Karachi Medical and Dental College Syed Feroj Ahmed CSIR–Indian Institute of Chemical Biology Talal Akbar University of Kentucky College of Medicine Subas Ali Dow Medical College Mahnoor Amin Army Medical College, National University of Sciences and Technology Anusha Ammu University of Nebraska Medical Center Chinedu Anthony Anene Bradford University School of Management Rahul Annabathula University of Kentucky

Sanam Anwer University of Alabama at Birmingham, Montgomery Baptist Medical Center South Jessica Arabski University of Nevada School of Medicine Christopher Areephanthu University of Kentucky College of Medicine David Asarnow Linkage Biosciences Inc. Babar Ashraf Army Medical College, National University of Sciences and Technology Maimoonah Asif Army Medical College, National University of Sciences and Technology Aamir Aslam Pakistan Medical and Dental Council Ifra Fahim Ata Dow University of Health Sciences Majid Atique Bronx Lebanon Hospital Brett Austin University of Kentucky College of Medicine Pablo Avalos Cedars-Sinai Medical Center Muhammad Azharuddin Independent Scholar Nishad Bahulekar Pune University xxiii

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John H. Barnhill Independent Scholar Elizabeth Baumann University of Kentucky Saleema Begum Independent Scholar William Bennett University of Kentucky College of Medicine Walisha Bland-Lemons University of Kentucky Amanda Blau University of Kentucky College of Medicine Himabindu Boja University of Louisville Madhav Bole University of Western Ontario Raevti Bole University of Kentucky College of Medicine Sarah E. Boslaugh Kennesaw State University Teresa Venezia Bowman Albert Einstein College of Medicine Kristin Boza Independent Scholar Kecia Brown Independent Scholar Frank Caso Independent Scholar Amit Chakraborty University of Kentucky College of Medicine Stacy Chambers Independent Scholar Astra I. Chang University of California, Davis Sana Asad Chaudhary National University of Sciences and Technology Haider Zafar Chaudhry Army Medical College, National University of Sciences and Technology Tess Chedsey Independent Scholar Fariha Cheema Army Medical College, National University of Sciences and Technology Nicholas Chien University of Kentucky College of Medicine Ian C. Clift Independent Scholar

Gordon Coleman Independent Scholar Michele Davidson George Mason University Inmaculada de Melo-Martín Weill Cornell Medical College Anna M. (Maria) Destro Eastern Piedmont University Medical School Joseph Dewey Broward College Doniel Drazin Cedars-Sinai Medical Center Collin Dubick University of Kentucky College of Medicine Amrita Duraiswamy Sri Ramachandra Medical College Shiza Khan Durrani Army Medical College, National University of Sciences and Technology Jason T. Eberl Marian University Karl Echiverri University of Kentucky College of Medicine Muhammad Ehtisham Memorial Hospital of Rhode Island Shady Elmaraghi University of Kentucky College of Medicine Reja Syed Emran Independent Scholar Dasom Eom Georgia Institute of Technology Arfa Faiz Army Medical College, National University of Sciences and Technology Muhammad Saad Faiz Army Medical College, National University of Sciences and Technology Warda Faridi Army Medical College, National University of Sciences and Technology Muhammad Farooq Pakistan Medical and Dental Council Mudassir Farooqui Aga Khan University Hospital Cindy Ferraino Independent Scholar Marxa L. Figueiredo University of Texas Medical Branch



Lluvia Frias Georgia State University Nicholas R. Fuggle St. George’s Hospital Sanniya Khan Ghauri Aga Khan University Hospital Abhijit Ghosh University of Michigan Marin Gillis Herbert Wertheim College of Medicine, Florida International University Jan Goldberg Independent Scholar Abdullah Hamid Gondal Army Medical College, National University of Sciences and Technology Tyler Guidugli University of Kentucky College of Medicine Onaizah Baqir Habib St. Luke’s Hospital Ahmed Hassan Army Medical College, National University of Sciences and Technology Tara Henriksen CASE Forensics Les Herbst University of Kentucky Linh Hoang University of North Texas Maruf Hoque Georgia State University Park Huff University of Kentucky Aaiza Iftikhar Pakistan Medical and Dental Council Ammara Iftikhar Pakistan Medical and Dental Council Anam Imtiaz Armed Forces Institute of Cardiology/ National Institute of Heart Diseases Ayesha Irum Army Medical College, National University of Sciences and Technology Saadia Noor Ishfaq Army Medical College, National University of Sciences and Technology

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Keisuke Ito Albert Einstein College of Medicine Noor Fatima Jamal Army Medical College, National University of Sciences and Technology Karima Jamil Army Medical College, National University of Sciences and Technology Prakash Janakiraman Independent Scholar Arslaan Javaeed Khyber Medical University Isma Nusrat Javed Rawalpindi Medical College Nazeeha Jawahir University of Kentucky College of Medicine Jangwook P. Jung University of Minnesota–Twin Cities Shalin Jyotishi University of Georgia Nuzhat N. Kabir KN Biomedical Research Institute Julhash U. Kazi Lund University Dasha Kenlan University of Kentucky College of Medicine Zahabia Khalid Army Medical College, National University of Sciences and Technology Daniya Khan Dow Medical College Ghulam Ishaq Khan Columbia University Ghulam Sajjad Khan Dow University of Health Sciences Komal Khan Army Medical College, National University of Sciences and Technology Muhammad Saim Khan Armed Forces Institute of Ophthalmology Muhammad Waqas Khan Aga Khan University Hospital Saad Akhtar Khan Aga Khan University Hospital Bill Kte’pi Independent Scholar Sharanya Kumar Independent Scholar

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Staci Lehman Independent Scholar Arthur Lemons III University of Kentucky Annarosa Leri Harvard Medical School/Brigham & Women’s Hospital Shulamit Levenberg Technion Oscar Lindblad Lund University L. L. Lundin Independent Scholar Irum Mahmood Army Medical College, National University of Sciences and Technology Sarah Mahmood National University of Sciences and Technology Ahmed Hassaan Malik Army Medical College, National University of Sciences and Technology Veeraswamy Manne Independent Scholar Quratulain Masood Army Medical College, National University of Sciences and Technology Francesco A. Mauri Imperial College London Mandy M. McBroom University of Texas Southwestern Medical Center Fahad Mehmood Dow University of Health Sciences Tej Ishaan Mehta University of Wisconsin–Madison Hema Mekala University of Missouri Trudy M. Mercadal Florida Atlantic University Andrew Micciche University of Kentucky College of Medicine Shari Parsons Miller Independent Scholar Mahnoor Mir Army Medical College, National University of Sciences and Technology Priya Mishra Independent Scholar

Nicholas Moore University of Kentucky College of Medicine Gift Kim Mushariwa Independent Scholar Sajid Mustafvi Army Medical College, National University of Sciences and Technology Yasser Nadeem Armed Forces Institute of Ophthalmology Arslan Naeem Rawalpindi Medical College Fatima Najeeb Independent Scholar Nasreen Najefi BioBank Center of Excellence Shariq Nawab Dow University of Health Sciences Manoel Figueiredo Neto Independent Scholar Muhammad Khizar Niazi Armed Forces Institute of Ophthalmology Brenda M. Ogle University of Minnesota–Twin Cities William Olmstadt LSU Health Sciences Center, Shreveport Michelle Park Georgia State University Nicholas Per University of Kentucky Lygia V. Pereira University of São Paulo David J. Pinato Imperial College London Smitha Prakash Independent Scholar Elizabeth Rholetter Purdy Independent Scholar Syed A. Quadri Desert Regional Medical Center, Palm Springs Sibi Rajendran University of Kentucky College of Medicine Jeannie Randall Aspen University Suganya Raphael University of Madras
 Muhammad Umer Rasool Combined Military Hospital Rawalpindi Wylene Rholetter Auburn University



Dante Ricci Stanford University Michael Rightmire Biocom Software Mark Rodgers University of Pittsburgh School of Medicine Lars Rönnstrand Lund University Shilpa Sachdeva University of Kentucky College of Medicine Fatima Sajid Army Medical College, National University of Sciences and Technology Nawal Saleh BioBank Center of Excellence Husein K. Salem BioBank Center of Excellence Stefan Scheding Lund University Stephen T. Schroth Towson University Brandon Schwarte University of Kentucky Vimal Selvaraj Cornell University
 Fariha Gul Sethi Independent Scholar Adeena Shahid Independent Scholar Seif Shahidain University of Kentucky College of Medicine Rohini Sharma Imperial College London Qiang Shi Texas Biomedical Research Institute Robert Shifko Independent Scholar Tara Shrout University of Kentucky College of Medicine Faris Shweikeh Cedars-Sinai Medical Center Wardah Siddiq National University of Sciences and Technology Rakshanda Najam Siddiqi Sind Medical College

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Waquar Idrees Siddiqui Independent Scholar Ruby A. Singh Independent Scholar Erin Monica Smith Independent Scholar Kelsey W. Snapp University of Kentucky College of Medicine Kristine Song University of Kentucky College of Medicine Mark O’Neal Speight Independent Scholar Kavitha Srinivasan University of Louisville Brad St. Martin University of Kentucky College of Medicine Avraham Steinberg Shaare Zedek Medical Center Kyle Stigall University of Kentucky College of Medicine Leslie Suen Cedars-Sinai Medical Center Javed Suleman Mount Sinai Hospital Jianmin Sun Lund University Arvind Suresh Independent Scholar Sajid S. Suriya Dow University of Health Sciences Richard Taing University of Kentucky College of Medicine Tetsuya S. Tanaka University of Notre Dame Ali Tariq Independent Scholar Areej Tariq Independent Scholar Muhammad Ali Tariq Sheikh Khalifa Bin Zayed Al Nahyan Medical and Dental College Akhilesh Tiwari University of Toronto Morenike Trenou Independent Scholar Zarish Umar Independent Scholar George C. Upper III Independent Scholar

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Atiq Ur-Rehman Independent Scholar Rhea U. Vallente Independent Scholar Nicole Van Hoey Independent Scholar John L. VandeBerg Texas Biomedical Research Institute Henry Vasconez University of Kentucky College of Medicine Krishna S. Vyas University of Kentucky College of Medicine Tracey Weiler Herbert Wertheim College of Medicine, Florida International University

Luke Williams University of Kentucky Amanda Wright University of Kentucky College of Medicine Wudan Yan Independent Scholar Atif Zafar University of Iowa Hospitals and Clinics Muhammad Junaid Uddin Zaheer Aga Khan University Hospital Quratulain Zamir Combined Military Hospital Rawalpindi Ferkhanda Zareen Army Medical College, National University of Sciences and Technology

Introduction The workings of the human body have mystified people for centuries. The search for answers took a whole new turn when cells were discovered. Cells were first observed in 1665 by Robert Hooke, an English natural philosopher, using a rudimentary microscope. More detailed observations were made a few years later by Anton Van Leeuwenhoek, a Dutch scientist who had handcrafted a more powerful microscope. These seminal observations, which had become possible because of technological progress, ignited a debate all over Europe. This debate culminated in the formulation by Schleiden and Schwann in 1838 of the cell theory that holds that all living organisms are composed of cells, the basic unit of life and, importantly, that all cells arise from other cells. Thus from the very beginning, progress in cell biology occurred through a combination of advances in technology which enabled novel experiments, and extensive theoretical debates to interpret the experiments. This pattern has repeated itself many times in the last three centuries and countless advances have led to our current wealth of knowledge about biology in general and stem cell biology in particular. Three hundred and fifty years after the first microscopic observation of cells and 170 years after the formulation of the cell theory, we now understand that while all cells arise from other

cells, not all cells are equal. Some cells are terminally differentiated, cannot be divided any further, and are destined for a programmed death; other cells can divide but only give rise to cells that are identical to themselves; and finally, a few cells that we call stem cells have the capacity to give rise either to cells that are identical to themselves or to cells that have acquired new properties. This choice between self-renewal and differentiation is the unique fundamental property of stem cells and is governed by environmental clues. There are two major types of stem cells, embryonic stem cells which are pluripotent stem cells and adult stem cells. Embryonic stem cells exist only transiently during development. Their function is to produce all of the cells that compose an adult organism. Adult stem cells reside in permanence in many organs. Their functions are to maintain homeostasis by replacing dying cells lost by normal wear and tear and to repair damages caused by injuries. The derivation of mouse embryonic stem cells in England in 1981 ushered in a new era in experimental biology. In combination with advances in molecular biology methods, the availability of these cells has allowed researchers to engineer mice carrying mutations with a very high degree of precision. In the last 30 years, the novel ability to modify the genetic material of mammals has led to considerable progress in our understanding xxix

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of the biology of higher organisms. In the United States in 1998, methods were developed to culture human embryonic stem cells that were harvested from very young, 4 to 5 day old, embryos that were left-over from in vitro fertilization. This important milestone has raised considerable hopes in the general public and in the press that a cure for many debilitating diseases might finally be at hand, but has also generated a firestorm of ethical and religious concerns because embryos had to be destroyed to derive these cells, and because these novel technologies give biologists unprecedented power over living organisms, including their own species. In the last 10 years, further technological progress has yielded another great leap forward for stem cell biology. Researchers in Scotland demonstrated that cellular differentiation in mammals could be reversed experimentally by injecting the nucleus of fully mature adult cells into an ovocyte. These experiments resulted in the birth of Dolly the sheep, the first cloned mammal. This important work demonstrated that the genetic material of an adult mature cell could be induced to return to a pluripotent stem cell form if the DNA was placed in the appropriate environment. Since this report, many clones have been produced including some for commercial purpose in the bovine industry. Even more recently, two Japanese researchers were able to genetically reprogram mature adult cells into cells which are virtually identical to embryonic stem cells by introducing into their genomes a few well-chosen genes. The remarkable production of induced pluripotent stem cells has raised the hopes of therapeutic fallout from stem cell research to new heights because this method can potentially be used to create custom stem cells for each patient. If researchers can learn how to transform custom induced-pluripotent stem cells into therapeutically useful cells, cellular therapy based on transplantation would be greatly facilitated because the therapeutic cells would be perfectly matched to the recipient, eliminating the need to search for compatible donors and greatly decreasing the potential for transplant complication. In addition, therapies based on such cells might be less controversial because the production of induced-pluripotent stem cells does not require the use of any embryos.

How Far Are We From the First Therapeutic Applications of Stem Cell Research? Both pluripotent and adult stem cells hold considerable promise for the treatment and prevention of human diseases. The realization of these promises will require a constant dialog between clinicians, translational and basic scientists. Adult stem cells have been in clinical use for over 40 years. One of the most successful therapeutic uses of adult stem cells is hematopoietic stem cell transplantation which is an effective way to treat a variety of leukemias and other disorders and is starting to be used in conjunction with gene therapy to cure a number of inherited diseases. However, the use of hematopoietic stem cell transplant is limited to only the most severe diseases by a shortage of donors and by the risks associated with the transplant procedures. A better understanding of the basic biology of stem cells is necessary to develop new culture and amplification methods that will eliminate the shortage. Generally, the intimate details of the biology of all stem cells found during development and in adults are progressively being deciphered by scientists all over the world. This massive effort will eventually yield a wealth of therapies for many ailments from the most benign to the most severe. Pluripotent stem cells hold a special place in stem cell biology because they are the source of all other cells; there are great hopes that it will eventually be possible to produce many cell types, including adult stem cells, that will be used in a wide range of therapies derived from pluripotent stem cells. Biology and pharmacology are experimental sciences which require access to experimental samples. Studies of human biology during development and in adulthood have long been hampered by the difficulties in obtaining experimental cells. In addition to potential transplantation applications, pluripotent stem cells are extremely useful as an unlimited, reproducible source of human cells that can be used experimentally to better understand the biology of many inherited and acquired diseases and to test and screen for new drugs using highly purified human target cells. These novel experimental models that can complement studies in animals are likely to speed up the development of novel diagnostic and prognostic tools, and of novel drugs and other therapeutic agents.



Differentiation of pluripotent stem cells recapitulates many aspects of human early development. The study of differentiating embryonic stem cells has already yielded novel insights in the development of the blood system and of many other organs. Such understanding is critical to understanding the pathophysiology and to eventually developing treatments for many developmental disorders. Over 100 years elapsed between the first observations of cells and microorganisms that were made possible by the invention of microscopes, and the development of vaccines and hygiene to protect from diseases caused by these microorganisms. Another 100 years passed before the discovery of the first antibiotics which eradicated many infectious diseases. Together, these discoveries revolutionized the world by causing an unprecedented demographic explosion. The benefits of these early studies continue to accrue since new antibiotics and new vaccines such as the vaccine against papilloma virus, which prevents cervical cancer, are regularly developed. As was the case for vaccines and antibiotics, it is likely that the benefit of stem cell research will slowly accumulate over many, many years. Hopes could first turn into reality in the fields of artificial transfusion products, an unlimited source of blood stem cells for transplantation, cures for some forms of diabetes and rare eye and liver diseases. More complex therapies involving artificial organs or the central nervous system will take longer to develop. New technologies and considerable theoretical progress in biology has led us to a new frontier in human history. Advances in stem cell biology, molecular biology, and the new science of genomics which was born after the sequencing of the human genome, will soon give biologists

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the ability to control and modify the biology and the reproduction of all living organisms, including members of their own species. This will likely result in healthier, longer lives for many of us but will also change and tax the environment to a considerable extent. How long will it take for these developments to occur? What kind of society will result from these new capabilities? How can we ascertain that these technologies be used to better the life of humankind? Will the benefits be shared by all, or reserved for a privileged few? There are no definite answers to any of these questions. In this encyclopedia we provide the readers with information about our current knowledge of basic stem cell biology, some of the current clinical trials and some of the major research institutions and companies that are engaged in stem cell research. We also highlighted a few past and current leaders in the field. We included a summary of the stem cell legislation regulating the research and discussions of the ethics of stem cell research according to various points of view. Thus, the readers can form their own opinion. Many important concepts, discoveries, people, institutions, and companies were not included in this encyclopedia. Given the increasing size and liveliness of the stem cell biology community and given the huge impact this novel scientific knowledge and technologies will have on society, providing a fully comprehensive view was not possible. We strived to provide answers to some important questions that might be asked by the general public. We apologize for all omissions and errors in advance. We thank Geoff Golson, Michele Chase, and their team for leading the effort to create this encyclopedia. Eric E. Bouhassira Editor

Chronology April 27, 1890: The Australian-born scientist Walter Heape performs the first embryonic transfer with mammals, successfully transferring an embryo from the womb of a mother rabbit to the womb of a surrogate rabbit. 1902: The German scientist Hans Spemann demonstrated that all the information necessary to create a new organism was contained within a single embryonic cell of a salamander, but as that development progressed and the cells became differentiated, the cells lost this ability. June 1, 1909: The Russian American scientist Alexander Maximow presents a lecture at the Hematological Society of Berlin introducing the concept of stem cells as the common ancestors of different cellular elements in the blood. 1935: The German scientist Hans Spemann receives the Nobel Prize for his work on the organizer effect, describing how embryonic induction allows cells to influence the development of nearby cells. 1951: Dr. George Gay grows the first HeLa cells, taken from a cancer patient named Henrietta Lacks. The HeLa cell line is notable for the fact that, unlike most cell lines that can be expected to die out within a limited period, the HeLa cell

line has continued to grow and divide for over 60 years. 1952: Robert Briggs and Thomas Joseph King successfully clone a tadpole, using nuclear transfer, a technique first proposed in 1928 by Hans Spemann. 1959: First successful use of stem cell transplants in humans, in three separate studies all involving hematopoietic stem cells (HSCs; immature blood cells through bone marrow grafting; E. Donnall Thomas and colleagues use syngeneic grafts (from identical twins) to treat two leukemia patients, George Mathé and colleagues perform allogeneic (from a separate individual who is not an identical twin) bone marrow transplants on five patients accidentally exposed to irradiation, and McGovern and colleagues treat a leukemia patient with autologous (from the patient) bone marrow cells. February 1961: Working at the Ontario Cancer Institute, James A. Hill and Ernest A. McCullough prove that stem cells exist in the bone marrow of mice and have the key properties of self-renewal and the potential to become any type of blood cell. June 1966: R. J. Cole, Robert G. Edwards, and John Paul isolate embryonic stem cells (ESCs) from the pre-implantation blastocysts of a rabbit. xxxiii

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1967: As a university student, Ian Wilmut spends a summer working in the laboratory of E. J. Chris Polge at the University of Cambridge, and becomes fascinated with the process by which an organism develops from a single cell. He later becomes famous when, working with Keith Campbell, his research leads to the birth of Dolly, a sheep born through cloning. 1968: First successful use of bone marrow transplantation to treat patients with leukemia or hereditary immunodeficiency: success due to presence of HSCs in the marrow graft, which can reconstitute blood and immune systems after myeloablation. 1974: The U.S. Congress imposes moratorium on federal funding for clinical research on embryonic tissue and embryos, which remains in place until 1993. 1974: The first transgenic mouse is created by Rudolf Jaenisch and Beatrice Mintz, who successfully change the DNA of lab mice by injecting DNA from a virus into mouse blastocysts. They observed that the genetic material from the virus becomes integrated into the mouse cells, thus preparing the way for the creation of animal models of human diseases using genetically modified mice. 1975: The British scientists Martin Evans and Gail Martin demonstrate that embryonal carcinoma cells are pluripotent and can differentiate into all three primary types of germ layer: ectoderm, endoderm, and mesoderm. 1978: The first human baby created by IVF (in vitro fertilization), Louise Brown, is born in the United Kingdom. The physiologist Robert Edwards, whose research played a key role in developing IVF, was awarded the Nobel Prize for Physiology or Medicine in 2010. June 23, 1980: Candice Reed, born at the Royal Women’s Hospital in Melbourne, becomes the first IVF baby born in Australia. 1981: Nature announces that two research groups, working independently, successfully

derived embryonic stem cells from the inner cell mass cells of the blastocyst in mice; one group is led by Martin Evans at the University of Cambridge (UK), the other by Gail Martin at the University of California, San Francisco. 1987: Peter Hollands demonstrates the first therapeutic in vivo (in a living animal) use of ESCs: injection of ESCs restores lost bone marrow stem cells in lethally irradiated mice. 1988: Bone Marrow Donors Worldwide, a collaborative network of stem cell donor registries and cord blood banks, founded in Leiden (The Netherlands) to facilitate sharing of HLA phenotype and other information to physicians of patients who need a hematopoietic stem cell transplant. 1989: Martin F. Pera and colleagues create a clonal line of human embryonic stem cells. Although the cells in this line include tissues from the three primary germ layers, the cells have different numbers of chromosomes (aneuploid) than do normal cells, and they also have limited ability to differentiate. 1992: Yasuko Matsui and colleagues announce successful isolation of mouse embryonic germ cells, which have properties similar to embryonic stem cells. January 1993: Newly elected president Bill Clinton instructs Donna Shalala, Secretary of the U.S. Department of Health and Human Services, to remove the ban on embryonic research. 1995: Congress bans federal funding for research on embryos, but leaves it unclear whether this ban applies to cells already derived from an embryo. November 1995: James A. Thomson and colleagues at the University of Wisconsin derive the first non-human embryonic stem cells, from rhesus monkeys, suggesting that embryonic stem cells could also be derived from humans. 1996: According to an April 2013 report by Euro­ StemCell, in 1996 only 0.4 percent of scientific publications (4,402 publications) concerned stem cells. Both the raw number and the proportion grew rapidly over the followings years, so that



in 2012, 12,193 publications about stem cell research were published (1 percent of all scientific publications). July 5, 1996: The first mammal clone, the sheep Dolly, is produced through the nuclear transfer of adult cells by the research team of Ian Wilmut and Keith Campbell. Critics of cloning note that Wilmut and Campbell required 277 nuclear transfers in order to produce one live sheep. 1998: M. J. Shamblott and colleagues announce successful derivation of pluripotent stem cells from cultured human primordial germ cells. November 5 and November 10, 1998: James A. Thomson at the University of Wisconsin, and John D. Gearhart at Johns Hopkins University report almost simultaneously that they have successfully isolated human embryonic stem cells (hESCs). Despite the therapeutic potential of hESCs, which can become any type of cell in the human body and thus offer hope for currently intractable conditions such as Parkinson’s Disease and spinal cord injury, the announcement is not without controversy due to the origins of the cells used in the research. Thomson’s team worked with cells from human embryos created in vitro (“in glass,” i.e., in the laboratory) while Gearhart’s team obtained their stem cells from human fetal tissue. 2000: Martin F. Pera, Alan Trounson, Ariff Bongso, and colleagues working in Singapore and Australia derive human embryonic stem cells from donated blastocysts. These cells have normal karyotypes, can proliferate in vitro for extended periods, and cause teratomas in immune-deficient mice. August 2000: The National Institutes of Health (NIH) legal department advises that NIH may fund research on cells derived from blastocysts, but may not fund the derivation of the cells themselves (which may be performed by private companies). December 2000: Mouse experiments by Timothy Brazelton and colleagues at Stanford University discover that HSCs can transform themselves to neuronal cells, demonstrating a plasticity (ability to become other types of cells than blood cells)

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which could have important therapeutic implications. This research has been challenged on several grounds but research continues because of the ready availability of HSCs (every person could serve as their own donor, making hESCs unnecessary). 2001: In Japan, the Ministry of Education, Culture, Sports, Science and Technology issues Human Embryonic Stem Cell Guidelines. Japan also passes a law regulating human cloning techniques. 2001: In Great Britain, Parliament amends the 1990 Human Fertilization and Embryology Act in order to allow some research on human embryos. The UK Stem Cell Bank is founded the following year, and in 2005, the UK Stem Cell Initiative is created to encourage both private and public funding of stem cell research. June 20, 2001: President George W. Bush vetoes, for the second time, a measure which would have lifted restrictions on hESC studies. This decision places him in opposition to most American voters and many members of the Republican party. In response to the Bush veto, Democratic presidential candidates Hillary Clinton and Barack Obama pledged to support federal funding for hESC studies if elected. July 2001: The Jones Institute, a private infertility clinic in Norfolk, Virginia, announces that it has created embryos from donated gametes (reproductive cells). August 9, 2001: President George W. Bush, in a speech on prime-time national television, announces federal research funding will be available for the first time for hESC research, but that such research would be limited to the estimated 60 pre-existing stem cell lines. November 2001: NIH invites proposals for stem cell research and releases a list of 74 acceptable stem cell lines; many of the lines are not suitable for human trials because they have been grown in mouse media. November 25, 2001: Advanced Cell Technology, a private company in Worcester, Massachusetts,

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announces that it has cloned human embryos from adult cells, creating cells which are a perfect genetic match for the donor. 2002: The United Kingdom announces that stem cell research is a scientific priority and allocates an additional 40 million pounds to support stem cell research. January 2003: Nine funding agencies form the International Stem Cell Forum (ISCF) to encourage international collaboration and promote increased funding for stem cell research; as of January 2004, 14 agencies from 13 countries have joined the ISCF. 2004: Annual report of the International Bone Marrow Transplant Registry reports that over 27,000 patients annually are treated by blood stem cell transplantation, for various cancers, hereditary diseases, and bone marrow failure. March 2004: Hwang Woo-Suk and colleagues at Seoul National University announce in the prestigious journal Science that they successfully cloned patent-specific stem cells using somatic nuclear transfer. Because the embryos were cloned in order to produce stem cells, rather than for reproduction, this reported success reopens the debate about therapeutic cloning (cloning cells for the purpose of treating human disease). Hwang’s previous research had been in genetically-modified livestock, and he claimed to have successfully cloned two cows in 1999, although he provided no scientific data to back up this claim. June 25, 2004: New Jersey becomes the first state to fund stem cell research, as legislators create the Stem Cell Institute of New Jersey and allocate it $9.5 million in state funding. Fall 2004: Prompted by the use of human embryos produced by in vitro fertilization (IVF), the Connecticut Law Review publishes a forum including contributions by Ann Kiessling, Julien I. Sirois, Keith E. Latham, and Christine Sapienza that attempts to clarify terminology regarding embryos as well as the ethical and moral issues relating to research using them.

November 2, 2004: Partly as a response to federal research funding restrictions, California becomes the second state to allocate funding for stem cell research, as voters approve Proposition 71. This bill creates the California Institute for Regenerative Medicine, which is allocated $3 billion in taxpayer funding over 10 years. January 1, 2005: Connecticut Governor M. Jodi Rell announces that she will recommend that the state budget include a special fund to support stem cell research in Connecticut. The state budget, passed in June, includes $100 million to support stem cell research over 10 years. May 23, 2005: The Starr Foundation announces awards of $50 million to support stem cell research at Weil Medical College of Cornell University, Rockefeller University, and Memorial Sloan-Kettering Cancer Center, all in New York City. May 31, 2005: The State of Connecticut Stem Cell Advisory Committee allocates $19.78 million in stem cell research funds to researchers from Yale, Wesleyan, and the University of Connecticut. These are the first grants from Connecticut’s Stem Cell Research Fund, which was created in 2005 and is charged with allocating approximately $100 million to support stem cell research by the year 2015. June 2005: Hwang Woo-Suk and colleagues publish an article in Science claiming that they have created 11 human embryos from somatic cells from different donors. He claims to have developed a more efficient process which uses fewer eggs to create more hESCs. July 13, 2005: Illinois Governor Rod Blagojevich issues an executive order which creates the Illinois Regenerative Institute for Stem Cell Research, which will award $10 million in state funds to support stem cell research. This makes Illinois the fourth state, and the first midwestern state, to allocate public funds to stem cell research. August 18, 2005: Colin McGuckin, Nico Forraz and colleagues at Kingston University (UK) announce discovery of cord-blood-derived



embryonic-like stem cells (CBEs, which appear to be more versatile than adult stem cells (found in bone marrow) although less versatile than hESCs. This discovery could skirt ethical objections to hESC research with cells derived from embryos, because umbilical cord blood can be acquired without destruction of human life. September 19, 2005: Brian Cummings, Aileen Anderson, and Colleagues at the University of California-Irvine announce that they successfully used adult neural stem cells to repair spinal cord damage in mice. The mice receiving neural stem cells showed improvement in coordination and walking ability, suggesting the research may lead to therapies to aid humans with spinal cord injuries. September 21, 2005: Floridians for Stem Cell Research and Cures, Inc., an advocacy group for stem cell research, propose a ballot initiative requiring the state of Florida to spend $200 million in state funds over the next 10 years in support of stem cell research. On September 23, Citizens for Science and Ethics, Inc., a group opposing stem cell research, files a petition which would amend Florida’s state constitution to prohibit embryonic stem-cell research. November 2005: Gerald Schatten a former colleague of Hwang Woo-Suk now at the University of Pennsylvania, announces there were ethical irregularities in Hwang’s procurement of oocyte (egg) donations used in his research. Roh Sungil, a close collaborator, announces at a press conference on November 21 that oocyte donors had been paid $1400 each for their eggs. On November 24, Hwang announces that he will resign from his post due to the scandal. December 16, 2005: New Jersey becomes the first state to allocate public funds for hESC research, as the State Commission on Science and Technology grants $5 million to 17 research projects, most located at the University of Medicine and Dentistry of New Jersey, Rutgers University, and Princeton University. December 29, 2005: A Seoul National University investigation of the work of Hwang Woo-Suk

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concludes that all 11 stem cell lines claimed in his 2005 paper were fabricated. 2006 (calendar year): Over 1100 articles on ESC research are published, a nearly 10-fold increase from 140 in 1997. January 11, 2006: Science retracts both of Hwang Woo-Suk’s papers due to scientific misconduct and fraud. On January 12, Hwang holds a press conference to apologize but does not take responsibility for the fraud claiming that members of his scientific team sabotaged his work. April 2006: Maryland allocates $15 million in state funding for ESC research, beginning in July 2006, through passage of the Stem Cell Research Act. May 12, 2006: South Korea indicts scientist Hwang Woo-Suk on charges of fraud, embezzlement, and bioethics violations. Three of his collaborators are also charged with fraud. June 21, 2006: Florida Governor Jeb Bush, speaking at the annual biotechnology Industry Organization meeting, announces his disapproval of hESC research. Bush further announces that no stem cell research will be performed at any Florida university, nor at the Scripps Research Institute in Palm Beach, Florida. July 2006: ES Cell International in Singapore becomes the first company to commercially produce hESCs which are suitable for clinical trials; vials of stems cells are offered for sale on the internet for $6,000. July 18, 2006: Senate Majority Leader Bill Frist (R-TN) publishes an editorial in the Washington Post announcing his support for federal funding of stem cell research, in opposition to President Bush’s policy. Frist also announces that he sees no contradiction between stem cell research and his pro-life beliefs. July 19, 2006: President Bush vetoes a bill, passed by the House in 2005 and the Senate in July 2006, which would expand federal funding for hESC research.

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August 2006: Working at Tokyo University, Shinya Yamanaka and Kazutoshi Takahashi create the first iPS cells (induced pluripotent stem cells) by introducing four genes into mouse skin cells; the resulting cells have properties similar to embryonic stem cells. In 2007, Yamanaka and Takahashi successfully produce iPS cells using human cells. August 23, 2006: Scientists from the private company Advanced Cell Technology announce they have developed a technique that allows them to remove a single cell from an embryo. The embryo is not harmed in the process and the cell can then be grown in the lab, circumventing ethical objections to hESC research which requires the destruction of embryos. November 7, 2006: Missouri voters pass Amendment 2, a constitutional amendment that states that any human embryonic stem cell research or treatment allowed by the federal government will also be allowed in Missouri. The narrow victory (51–49 percent) galvanizes opposition to the bill, much of which is centered on their contention that it would allow human cloning. November 28, 2006: In the wake of the Hwang Woo-Suk scandal, a panel led by John I. Brauman recommends changes in the procedures used to review papers submitted for publication in Science. The changes recommended include flagging high-visibility papers for further review, requiring authors to specify their individual contributions to a paper, and online publication of more of the raw data on which papers are based. 2007: The Nobel Prize in Physiology or Medicine is awarded to Mario R. Capecchi, Sir Martin J. Evans, and Oliver Smithies, for their work on altering mouse embryonic stem cells. January 7, 2007: Dr. Anthony Atala of Wake Forest University and colleagues from Wake Forest and Harvard Universities report the discovery of amniotic–fluid-derived stem cells (AFS), which seem to hold similar promise to hESCs. The researchers reported that AFS could be extracted without harm to mother or child, thus avoiding some of the moral controversies regarding hESCs.

February 28, 2007: Governor Chet Culver of Iowa signs the “Iowa Stem Cell Research and Cures Initiative,” a bill which ensures that Iowa researchers will be allowed to conduct stem cell research and that Iowa patients will have access to stem cures and therapies. The bill also prohibits human cloning. March 11, 2007: An article in the Baltimore Sun newspaper reports that wording had been changed in a bill before the Maryland legislature, replacing the word “embryo” with “certain material,” in an effort to get the bill to pass. March 31, 2007: New York passes a budget for the Fiscal Year 2008 which includes an appropriation of $100 million for stem cell and regenerative medicine research. The funds will be distributed through the Empire State Stem Cell Trust, which will be funded at $50 million per year for ten years after the initial appropriation of $100 million. April 11, 2007: Richard K. Burt and colleagues report success in treating Type I diabetics in Brazil with stem cells taken from their own blood. The experimental procedure, reported in the Journal of the American Medical Association, has allowed the diabetics to stop taking insulin for as long as three years. May 30, 2007: California governor Arnold Schwarzenegger and Canada’s Premier of Ontario Dalton McGuinty announce an agreement between Canada’s International Regulome Consortium and the Stem Cell Center at the University of California-Berkeley to coordinate research. McGuinty also announced the creation of the Cancer Stem Cell Consortium, which will coordinate and fund cancer stem cell research, and announced an initial donation of $30 million Canadian from the Ontario Institute of Cancer Research to fund the consortium. June 6, 2007: Rudolf Jaenisch and colleagues at the Whitehead Institute, affiliated with the Massachusetts Institute of Technology in Boston, announce in Nature that they have succeeded in manipulating mature mouse stem cells so they have the properties of ESCs. In the same issue



of Nature, Shinya Yamanaka and colleagues at Kyoto University announce that they have developed a method to reprogram stem cells in mice back to the embryonic state, so they may then develop into different body cells similarly to hESCs. If this technique is adaptable to human cells, it would allow researchers to bypass most of the controversy involved with the use of hESCs which are derived from human embryos. June 20, 2007: President Bush vetoes legislation that would have allowed federally funding ESC research using cells from embryos from fertility clinics which would be destroyed anyway. At the same time, Bush issued an executive order encouraging federal support of research aimed at creating stem cells without destroying embryos. August 3, 2007: Kitai Kim, George G. Daley, and their colleagues at Children’s Hospital, Boston, report in the journal Cell Stem Cell that Hwang Woo-Suk, the discredited Korean researcher, did have one significant research result which appears to be genuine. The Children’s researchers determined that Hwang’s purposed ESCs were produced by parthenogenesis (virgin birth) from unfertilized eggs, a result since achieved by other researchers as well. November 6, 2007: New Jersey voters reject a ballot measure which would have allowed the state to borrow $450 million to fund stem cell research. Defeat of the initiative is attributed to the state’s worsening fiscal condition and a vocal alliance of conservatives, anti-abortion activists, and representatives of the Catholic church who oppose stem cell research. November 14, 2007: Shoukhrat Mitalipov and colleagues at the Oregon Health and Science University’s national Primate Research Center announce in Nature that they have successfully derived ESCs by reprogramming genetic material from the skin cells of rhesus macaque monkeys. November 20, 2007: The journals Cell and Science carry reports of discoveries by two independent teams of scientists which reprogram human skin cells to have the characteristics of hESCs. One team is led by Shinya Yamanaka, who reported

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success for the same procedure in mouse experiments in 2006; the other is led by James Thomson of the University of Wisconsin–Madison. December 2007: Rudolf Jaenisch, working at the Whitehead Institute for Biomedical Research at MIT, demonstrates that iPS cells could be reprogrammed to treat sickle cell disease in mice. 2008: According to an April 2013 report by EuroStemCell, only 108 scientific publications regarding human embryonic stem cells were published in 2008; by 2012, this number increased to 1,071, a compounded growth rate of 77 percent. January 14, 2008: Doris Taylor and colleagues at the University of Minnesota report success in creating a beating rat heart by injecting cells from newborn rats into the valves and outer structure of a dead rat heart. January 17, 2008: Andrew J. French and colleagues report in Stem Cells that they have successfully used somatic cell nuclear transfer to produce cloned human embryos from adult skin cells. February 20, 2008: Scientists at Novocell, a private biotechnology company located in San Diego, announce that they have successfully used hESCs to control diabetes in mice whose own insulinproducing cells had been destroyed. April 2008: Rudolf Jaenisch, working at the Whitehead Institute for Biomedical Research at MIT, demonstrates that iPS cells reprogrammed to act as neurons could be used to treat Parkinson Disease symptoms in animal models. November 13, 2008: The United Kingdom passes the Human Fertilisation and Embryology Act 2008, amending the Human Fertilisation and Embryology Act 1990. Among its provisions are banning sex selection of embryos other than for medical reasons; recognizing the right of samesex couples to parent children through donated embryos, sperm, or eggs; and recognizing the state’s right to regulate the in vitro creation of human and human-admixed embryos, the latter referring to embryos created for research purposes using both human and animal genetic material.

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January 2010: Working at Stanford University, Marius Wernig creates functional neurons in vitro from converted mouse skin cells. February 2010: Rebecca Skloot publishes The Immortal Life of Henrietta Lacks, a biography of the woman whose cells produced the HeLa line commonly used in scientific research. Skloot’s book won numerous awards and sparked public discussion over informed consent and other ethical questions in scientific research. March 2010: The organization EuroStemCell is founded, with funding from the European Commission’s Seventh Framework Programme, as a partnership among stem cell researchers, clinicians, ethicists, journalists, and educators. August 2010: Working at the Gladstone Institutes in San Francisco, California, Deepak Srivastava creates mouse heart cells by reprogramming nonmuscle mouse cells. October 2011: In Bruestle vs. Greenpeace, the European Court of Justice rules that inventions and technologies based on human embryonic stem cells cannot be patented within the European Union. 2012: Sir John B. Gurdon and Shinya Yamanaka are jointly awarded the Nobel Prize in Physiology or Medicine for their work in creating induced pluripotent stem cells. April 2012: Deepak Srivastava demonstrates, in animal research, that heart function following a heart attack can be improved by reprogramming scar tissue from the heart attack into beating heart cells. June 2012: Steven Finkbeiner and members of the International Huntington’s Disease consortium develop the first human cell-culture model of Huntington’s Disease. October 4, 2012: Mitinori Saitou and colleagues at Kyoto University announce that they have successfully reprogrammed mouse stem cells to create egg precursor cells. When mixed with cells from female mice, these cells developed into eggs,

which were then fertilized by IVF and grew into normal baby mice. April 2013: According to a report by EuroStemCell, over the years 2008 through 2012, publications about stem cell research were cited 50 percent more often than the average for all scientific papers. In 2008, publications about embryonic stem cell research had an impact factor of 1.80 (meaning that on average each publication was cited in 1.80 other publications). Papers about human embryonic stem cells had an even higher impact factor, although it declined slightly over the years, from 2.35 in 2008 to 2.08 in 2012. Countries with the highest publication activity concerning stem cell research include Singapore (80 percent higher than the global average), Italy (65 percent higher), the United States (61 percent higher), Japan (53 percent higher), and Israel (52 percent higher). May 16, 2013: Shoukhrat Mitalipov and colleagues at Oregon Health and Science University report that they have produced human embryonic stem cells by reprogramming human skin cells. July 20, 2013: Robin Ali and colleagues at University College London demonstrate that lightsensitive retinal cells, created in the lab from stem cells, can be integrated into the eye cells of blind mice. This research suggests that similar treatments might be developed for humans who have become blind through retinal damage. August 5, 2013: In an event televised by the BBC, Mark Post, a physiologist at Maastricht University, presents the world’s first hamburger made from lab-grown beef. Post said his purpose was to create meat for human consumption while avoiding the global pollution caused by conventional beef production. January 29, 2014: Haruko Obokata and colleagues, working in Kobe, Japan, announce that they have developed a simple and quick way to create stem cells by treating animal cells with an acidic solution. However, other researchers were unable to duplicate her work and, in April 2014, Obokata is found guilty of misconduct due to discrepancies in her work.



February 1, 2014: Researchers working at the Gladstone Institutes in San Francisco announce in the journal Cell Stem Cell that they have successfully used transplants of stem cells in mice to replace damaged pancreas cells. If successfully translated to humans, this suggests that future stem cell research may be able to provide a cure for Type I diabetes. March 28, 2014: New Scientist reports that, in a survey of stem cell researchers from around the world, over half felt that they were subject to greater scrutiny than researchers in other scientific fields, but that most felt this did not affect their work. However, a minority (16 percent) said that they also felt pressure to publish results of their work too quickly, and a smaller minority (3 percent) said they felt pressure to behave unethically, for instance to falsity or augment data for a publication. May 2014: A team of researchers at ReNeuron, a company in Guildford, U.K., report that stroke patients treated by having stem cells injected into their brains show measurable improvements one year later, with higher quality of life, and lower disability, handicap, and dependency. July 2014: Two papers published in Nature, which claimed that the authors had produced

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embryonic-like stem cells by dipping adult cells into an acid bath, are retracted. The author, from the Riken Institute in Kobe, Japan, withdrew the papers after no independent team was able to reproduce their results, and after public scrutiny revealed many flaws including manipulated pictures and mislabeled images in the papers. November 2014: Foteini Hassiotou and colleagues report that stem cells in breast milk can be transmitted from mother to offspring in mouse models. Their results suggest that the stem cells in breast milk can enter the offspring’s blood via their stomach, and play a functional role in the offspring’s life. January 15, 2015: Researchers at Stanford University, led by Charles Chan and David Lo, publish an article in Cell reporting their discovery of the stem cell that gives rise to bone, cartilage, and stroma, the latter being part of the bone marrow. The team, working with mice, also charted the chemical signals that create skeletal stem cells and steer their development into different tissue types. March 2015: Timothy Kieffer and colleagues report successful results from an experiment combining human stem cell transplantation and antidiabetic drugs in treating Type 2 diabetes in a mouse model.

A Aastrom Biosciences, Inc. Aastrom Biosciences, Inc. is a leading U.S. manufacturer of patient-specific stem cell therapies that are designed to treat persistent, severe cardiovascular conditions such as congestive heart failure and peripheral arterial disease. The company’s research and development efforts are centered on creating an individualized multicellular therapy called ixmyelocel-T that is derived from stem cells originating in each patient’s own bone marrow. The bone marrow is extracted and subjected to Aastrom’s proprietary cell-processing technology, which stimulates natural production of various cell types that play key roles in tissue repair and healing. The processed marrow is delivered back into the patient’s damaged tissue by way of direct infusion, injection, or transplant to promote sustained restoration of tissues and organs. Aastrom expanded its cell therapy portfolio in 2014 with the acquisition of Sanofi’s Cell Therapy and Regenerative Medicine business. Proprietary Cell-Processing Technology Since its founding in 1989, Aastrom Biosciences, based in Ann Arbor, Michigan, has become a leader in the development of patient-specific multicellular therapies for the treatment of critical cardiac diseases. A key component of the company’s success is its proprietary, automated cell-processing system.

After a small amount of bone marrow is extracted from a patient’s hip during a brief outpatient procedure, the sample is subjected to Aastrom’s cell-processing technology to selectively and significantly expand naturally occurring populations of cell types that promote or facilitate healing. Through cell processing, the number of stem cells can be increased by as much as several hundred times more than the quantities found in the patient’s natural bone marrow. After 12 days of processing with the enhanced multicellular therapy (ixmyelocel-T), the cells are returned to the physician in a sterile bag to be administered within three days back into the same patient to stimulate regeneration of damaged cardiovascular tissue. Aastrom’s manufacturing process is carried out in a highly automated, sterile environment that is fully protected and rigorously controlled through company protocols and current Good Manufacturing Practices guidelines mandated by the U.S. Food and Drug Administration. The cellprocessing system operates in a 5,000-square-foot centralized manufacturing facility in Ann Arbor with an annual capacity to treat as many as 3,000 patients, as of May 2014. The system is designed to be easily reproduced and expanded based on future cell-processing production needs. The cutting-edge manufacturing process works solely with adult stem cells derived from, and 1

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returned to, the same patient. The individualized therapeutic approach increases the likelihood that the cell therapy will integrate with surrounding tissues and reduce or eliminate the need for the patient to take immunosuppressive drugs. Ixmyelocel-T Therapy Ixmyelocel-T is a patient-specific, expanded multicellular therapy created using Aastrom’s unique cell-processing system. The therapy offers a number of features that are important for the success of treating patients suffering from complex, chronic diseases such as dilated cardiomyopathy (DCM), which is a widespread form of heart failure, and critical limb ischemia (CLI), the most severe form of peripheral arterial disease. One of the most beneficial features of ixmyelocel-T is that it is autologous, meaning that it is specific to the individual patient. Starting with the patient’s own cells, which are already accepted by the patient’s immune system, enables the new healing-specific cells to integrate more seamlessly into existing tissues. As a result, the risk of rejection and the need for immunosuppressive therapy are virtually eliminated. Cell expansion is another key advantage of ixmyelocel-T. With a patient bone marrow sample of just 50 milliliters (ml), critical stem cell types (mesenchymal cells, monocytes, and alternatively activated macrophages) can be expanded up to 300 times their original number present in the starting bone marrow sample. The larger cell quantities of multiple cell types aid in the process of tissue remodeling, immune response, and blood vessel formation to support cell function. In addition to efficacy and safety evidence from U.S. clinical trials, ixmyelocel-T also offers the patient convenience because it is minimally invasive. Bone marrow can be extracted during an outpatient procedure lasting only about 15 minutes. The ixmyelocel-T therapy can be administered to the patient a few weeks later during a single outpatient procedure that can be completed in approximately 20 minutes. Ixmyelocel-T Clinical Trials Clinical trials of ixmyelocel-T have focused on therapies for DCM and CLI, which are two prevalent diseases associated with significant mortality and very limited treatment options.

Dilated cardiomyopathy is a progressive disease of the heart muscle in which the heart becomes enlarged. Heart enlargement causes poor function that often leads to progressive heart failure as the heart loses its ability to sufficiently contract and pump blood efficiently around the body. DCM is a leading cause of heart failure and heart transplantation. Some medication and medical devices can be used to help control DCM symptoms, but there is no cure for the disease. Aastrom has been working to develop ixmyelocel-T as a potential cell-based therapy option for patients with DCM. As of 2014, the company’s clinical trials have focused on assessing the efficacy and safety of ixmyelocel-T administered by catheter and transendocardial injection and on evaluating the safety and tolerability of surgically delivered ixmyelocel-T compared to the traditional standard of care for patients with DCM. Aastrom also has undertaken clinical trials for ixmyelocel-T as a treatment approach for critical limb ischemia, a severe form of peripheral arterial disease caused by chronic inflammatory processes in the arteries that hinder blood flow and reduce circulation to the legs, feet, and hands. Without sufficient blood supplies, the extremities become extremely painful, ulcers begin to form, and— without surgical revascularization procedures— tissue eventually begins to die. Sometimes amputation is the only way to stop the spread of tissue necrosis (tissue death), infection (from non-healing ulcers), or excruciating pain caused by CLI. The company’s clinical trials for CLI have sought to assess the efficacy and safety of ixmyelocel-T treatment versus placebo in CLI patients generally and in regard to amputation-free survival at 12 months post-injection. Cell Therapy Portfolio Expansion On April 21, 2014, Aastrom Biosciences announced a definitive agreement to acquire Sanofi’s Cell Therapy and Regenerative Medicine business for $6.5 million. The acquisition gives Aastrom global commercial rights to manufacture and market three existing patient-specific cell therapy products: Carticel®, an implant marketed in the United States for the treatment of joint cartilage defects; MACI®, a third-generation joint implant therapy marketed in the European Union; and Epicel®, a permanent skin replacement available globally for

Adipose: Cell Types Composing the Tissue



the treatment of full-thickness burns covering 30 percent or more of total body surface area. Under the deal, Aastrom acquires global manufacturing and production centers in both the United States and Denmark. Shari Parsons Miller Independent Scholar See Also: Clinical Trials, U.S.: Heart Disease; Clinical Trials, U.S.: Peripheral Vascular Disease; Heart Disease; Mesenchymal Stem Cells; Stem Cell Companies: Overview. Further Readings Johns Hopkins Medicine. “Stem Cell Therapy Safely Repairs Damaged Heart Muscle in Chronic Heart Failure Patients, Study Shows.” http://www .hopkinsmedicine.org/news/media/releases /stem_cell_therapy_safely_repairs_damaged_heart _muscle_in_chronic_heart_failure_patients_study _shows (Accessed May 2014). Langwith, Jacqueline. “Stem Cells.” Detroit, MI: Gale Group, 2011. Stein, Richard A. “ReGen Med: Straight Out of Mythology.” Genetic Engineering and Biotechnology News, v.3/12 (2013).

Adipose: Cell Types Composing the Tissue Adipose tissue is a loose connective tissue with the primary function of storing lipids that can be harvested for energy. This function is performed by adipocytes, which comprise the vast majority of cells in adipose tissue. However, multiple other cell types can be found in adipose tissue; these cells are grouped under the category of the stromal vascular fraction (SVF). Cells of the SVF include preadipocytes, fibroblasts, vascular endothelial and smooth muscle cells, mesenchymal stem cells, endothelial progenitor cells, and immune cells such as anti-inflammatory M2 macrophages and T regulatory cells. An understanding of the cell types in adipose tissue is crucial for many relevant clinical applications, such as approaches to dealing with obesity and also

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potential therapeutic uses of adipose stem cells for various disease processes. Function of Adipocytes “Adipose tissue” often refers to white adipose tissue, which generally comprises around 20 percent (with great variation) of human body mass. In many mammals, including human infants, brown adipose tissue is also present for thermogenic function in the absence of shivering. Human adults also have remnants of brown adipose tissue, generally in the neck or upper chest region, but white adipose tissue is the most prevalent and clinically relevant. White adipocytes. The majority of white adipose tissue is located either subcutaneously or viscerally, although small deposits can be found in a variety of locations, from within the bone marrow to around the epicardium, within joints and in craniofacial pads. Subcutaneous adipose tissue is located in the hypodermis throughout the body and especially in regions such as the hips, abdomen, or thighs. Visceral adipose tissue is packed in between organs of the abdomen, and is thought to be the most clinically relevant for disease processes such as obesity and type 2 diabetes mellitus. The primary cell type in white adipose tissue is the white adipocyte. White adipocytes have a distinctive histological appearance of a single (unilocular) large lipid droplet surrounded by a thin layer of cytoplasm with a flattened peripheral nucleus. Multiple hormone and other receptors are present on the surface of white adipocytes; this, coupled with endogenous adipocyte hormone production, gives white adipose tissue tremendous endocrine function in addition to its storage capacities. In particular, white adipocytes play key endocrine roles in energy metabolism and sex hormone levels. One way that energy metabolism is regulated is through white adipocytes’ synthesis and secretion of leptin, a peptide hormone that inhibits appetite in the hypothalamus. Circulating levels of leptin are proportional to the amount of white adipose tissue in the body, and leptin resistance has been implicated in obesity. Energy metabolism is also regulated by the presence of insulin receptors on white adipocytes, which inhibit lipolysis in the presence of sufficient glucose in the bloodstream.

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Adipose: Cell Types Composing the Tissue

Adipose tissue or body fat is loose connective tissue composed of adipocytes whose main function aside from insulating the body is to store energy in the form of lipids. The two types of adipose are white adipose tissue (WAT) and brown adipose tissue (BAT). (Wikiversity Journal of Medicine)

Sex hormone levels in the body are influenced by white adipocytes’ ability to synthesize estradiol, via their production of the enzyme aromatase that converts androgens into estrogen. However, the primary function of the white adipocyte overall is to store lipid. Lipid content of adipose tissue overall increases with age, due to hypertrophy of white adipocytes. Although excess energy intake can result in the formation of new adipocytes, weight loss results in merely shrinkage of existing adipocytes rather than a decrease in number. Brown adipocytes. Brown adipocytes have a greater ratio of cytoplasm to lipid content, and multiple smaller lipid droplets (multilocular) when compared to white adipocytes. The cytoplasm contains multiple mitochondria, which lend to the brown color of the cell and work to generate heat via lipid oxidation. Unlike white adipocytes, brown adipocytes express uncoupling-protein 1 (UCP-1), which drives the generation of heat by dissipating the mitochondrial proton gradient (leading to direct heat production rather than ATP production and storage). Brown adipose tissue in general also exhibits greater vascularization, due to a greater need for oxygen by the mitochondria. Recent research has looked into the possible expression of UCP-1 by white adipose tissue as a method of combating obesity.

Function of Stromal Vascular Fraction Preadipocytes. Preadipocytes are fibroblastlike cells derived from mesenchymal stem cells. Preadipocytes are committed to the adipocyte lineage and are regularly present in adipose tissue in small quantities, where they serve both to replenish dying adipocytes (adipocyte turnover is around 10 percent per year) and to increase existing adipocyte numbers when energy stores are plentiful. Preadipocytes often reside in close proximity to the vasculature of adipose tissue and express the transcription factor PPAR, which has been identified as essential to adipogenesis. Preadipocytes require a specific, highlipid microenvironment in order to differentiate into adipocytes; however, in the case of obesity, preadipocyte numbers actually decrease, perhaps as a compensatory mechanism to prevent excess irreversible adipocyte formation. One of the factors that allow preadipocytes to maintain stable reservoirs of adipogenesis is their expression of telomere reverse transcriptase, which prevents the shortening of telomeres and subsequent DNA degradation over generations of replication. Differing populations of preadipocytes give rise to brown and white adipocytes, and within white adipocytes, there are regional differences as well. For example, visceral preadipocytes take much longer than their subcutaneous counterparts to differentiate and mature into adipocytes; this may explain the hypertrophy and greater lipid accumulation of visceral adipocytes. A greater amount of lipids in each adipocyte in turn influences the adipokines (signaling proteins from adipose tissue) that are secreted, which can have profound clinical effects. For example, visceral adipocytes secrete much less of the adipokine adiponectin, and this has been shown to decrease insulin sensitivity and ramp up pro-inflammatory processes in visceral adipose tissue compared to subcutaneous. Research on how to alter preadipocyte gene expression, and thereby change adipocyte characteristics, has been relevant both for obesity and also in potential approaches to treating lipodystrophic disorders. Mesenchymal stem cells. From mesodermal origin, mesenchymal stem cells (MSCs) are present in many different connective tissues, such as



Adipose: Cell Types Composing the Tissue

within the bone marrow. In the microenvironment of adipose tissue, MSCs generally differentiate into preadipocytes. However, MSCs can still be induced to develop into osteogenic, chondrogenic, myogenic, and other lineages, and have been heralded for their great research potential. Harvested via liposuction, in vitro studies of processed lipoaspirate (PLA) have yielded MSCs that are being studied for their use in autologous stem cell transplant. Human adipose tissue shows great potential for potential stem cell use due to its availability, quantity, and ease of obtainment. Endothelial progenitor cells. Separate from mesenchymal stem cells, endothelial progenitor cells (EPCs) have been identified that give rise to adipose tissue vasculature. These EPCs are freecirculating and bone marrow derived, and usually present in the SVF in small quantities. They contain angiogenic and/or hematopoietic cell markers. It has been postulated that in obesity, there are greater numbers of EPCs trapped in the adipose tissue rather than free to circulate, and thus angiogenic ability overall is reduced in obese patients. EPCs have also been the subject of much research recently involving potential transplantation to rebuild vessels damaged by atherosclerosis and stenosis. Immune cells. Both T-regulatory immune cells and macrophages are resident to the SVF. The T-regulatory cells (T-regs) are immune suppressive cells formed from the activation of T cells in the absence of costimulatory signals, and their presence in adipose tissue has shown to be induced by markers generated from MSCs in adipose. T-regs in turn help promote the presence of macrophages. The macrophages present in adipose tissue are interesting in that they possess markers for both pro- and anti-inflammatory processes. On a surface level, adipose tissue macrophages (ATMs) express markers and receptors similar to M2-type macrophages, which promote tissue repair. ATMs, like M2 macrophages, can also be induced to secrete anti-inflammatory proteins like IL-10 and IL-1 receptor antagonist. However, these same ATMs also secrete inflammatory proteins such as TNF-α, IL-1, and IL-6 in quantities high enough to offset any

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anti-inflammatory activity by both the ATMs and T-regs. It is postulated that the ATM protein secretion is under the regulation of adipocytes, which also secrete these inflammatory proteins themselves, and both of these processes contribute to the low-grade inflammatory state often present in obesity. Other cells. Vascular and extracellular matrix cells that are present throughout the body are also found in adipose tissue. Similar to vasculature throughout the body, the vessels of adipose tissue consist of endothelial and smooth muscle cells. These endothelial cells include both ordinary endothelial cells like those found elsewhere and also specialized endothelial cells that appear to be able to induce preadipocyte generation. Fibroblasts also help secrete collagen and other extracellular matrix components that help form the structure of adipose tissue. Overall, many different cells in adipose tissue have vast potential for further research investigation. Especially with the rise of obesity, there has been a much greater international interest in learning more about the components of adipose tissue and how they can be altered. In particular, MSCs and preadipocytes show promise for future use both in treating obesity and a plethora of other disorders. Both adipocytes and components of the stromal vascular function are integral parts of adipose tissue, and understanding their functions will be a critical cornerstone of future learning. Krishna S. Vyas Nazeeha Jawahir University of Kentucky College of Medicine See Also: Adipose: Current Research on Isolation or Production of Therapeutic Cells; Adipose: Development and Regeneration Potential; Adipose: Existing or Potential Regenerative Medicine Strategies; Adipose: Major Pathologies; Adipose: Stem and Progenitor Cells in Adults; Adipose: Tissue Function. Further Readings Esteve, Ràfols M. “Adipose Tissue: Cell Heterogeneity and Functional Diversity.” Endocrinol Nutr (July 5, 2013).

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Majka, S. M., Y. Barak, and D. J. Klemm. “Concise Review: Adipocyte Origins: Weighing the Possibilities.” Stem Cells (July 2011). Riordan, N. H., T. E. Ichim, W. P. Min, H. Wang, F. Solano, F. Lara, M. Alfaro, J. P. Rodriguez, R. J. Harman, A. N. Patel, M. P. Murphy, R. R. Lee, and B. Minev. “Non-Expanded Adipose Stromal Vascular Fraction Cell Therapy for Multiple Sclerosis.” Journal of Translational Medicine (April 24, 2009). Rosen, E. D. and B. M. Spiegelman. “Adipocytes as Regulators of Energy Balance and Glucose Homeostasis.” Nature (December 14, 2006). Zeyda, M., D. Farmer, J. Todoric, O. Aszmann, M. Speiser, G. Györi, G. J. Zlabinger, and T. M. Stulnig. “Human Adipose Tissue Macrophages Are of an Anti-Inflammatory Phenotype but Capable of Excessive Pro-Inflammatory Mediator Production.” International Journal of Obesity (London) (September 2007).

Adipose: Current Research on Isolation or Production of Therapeutic Cells Adipose-derived stem cells, or ASCs, are a unique population of stem cells isolated from adipose tissue. These multipotent stem cells present an alternative to the widely used embryonic and hematopoietic stem cell lineages for laboratory and clinical applications in regenerative medicine. Adipose tissue is abundant in the body and exists in several forms, including bone marrow, mammary tissue, and mechanical, brown (multilocular), and white (unilocular) adipose tissues. Traditional methods of gathering stem cells include the controversial isolation of embryonic stem cells and the painful process of procuring stem cells from bone marrow. In contrast to these methods, an efficient manner of isolating and producing reliable stem cell populations from abundant, easily accessible adipose tissue presents an appealing alternative for clinical therapeutic applications. Thus far, adipose stem cells have

been shown capable of multipotent mesodermal differentiation, as well as potential endodermal and ectodermal lineages in vitro. Evidence for Adipocyte Precursor Cells Progressive osseous heteroplasia (POH), a pathologic condition that leads to heterotopic bone formation within subcutaneous adipose and, eventually, muscle tissue, demonstrates the presence of adipocytes, osteoblasts, and chondrocytes upon histologic examination of the resultant lesions. Pathologic evidence from this rare, autosomal-dominant, inherited genetic defect suggests that ADCs are at least capable of differentiation into the aforementioned mesodermal lineages. Along with POH, lupus and Paget disease are also known to present with calcification of subcutaneous adipose, providing further evidence for the presence of multipotent ASCs within adipose tissue. Additionally, research using ligand-induced adipogenesis for the chemotherapeutic treatment of liposarcomas suggests that these cancers may derive from a stem cell progenitor; stimulation by both long-chain fatty acids and synthetic steroid compounds induces adipocyte formation from liposarcoma-derived cells. Furthermore, radioactive tracing to measure adipocyte turnover rates in obese patients indicates a lifespan of six to 15 months for these fully differentiated adult adipocytes, a value that seems to indicate the presence of a controlled replacement mechanism of mature cells by resident stem cell–adipocyte precursors. Evaluation of individuals who have undergone rapid weight loss through either metabolic or procedural means also supports this concept: Not only do existing adipocytes increase in volume but new adipocytes emerge in a homeostatic process to maintain a relatively constant level of adipose tissue within the organism. Origin of ASCs Adipose tissue is abundant in the body and exists in several forms, including bone marrow, mammary tissue, and mechanical, brown, and white adipose tissues. It is speculated that ASCs arrive in adipose tissue via distribution of circulating fibroblasts derived from the bone marrow that then colonize the respective adipose tissues throughout the body. Transplanted bone marrow-derived fibroblasts similar to the ones already discussed have been shown capable of differentiating into



Adipose: Current Research on Isolation or Production of Therapeutic Cells

adipocytes upon proper chemical stimulation and in the presence of a lipid-rich diet; however, the exact origin and distribution of ASC populations remains unknown. Regarding the relative abundance of stem cell populations within the body’s various adipose depots, current evidence suggests that richer concentrations of progenitor cells exist in the arm and abdomen relative to samples taken from the thigh or breast. Further studies, along with effective isolation techniques, are still needed to optimize processes for procuring ASCs in the most efficient manner from donors. Cell Isolation From Adipose Tissue Older methods of isolating cells from adipose tissue involved thoroughly rinsing minced animal fat pads, digestion with collagenases, and centrifugation to separate the desired stromal vascular fraction (SVF) that contained the processed lipoaspirate cells within a heterogeneous mixture. Finally, the plastic-adherent cells within the isolated SVF were selectively purified on the surface of tissue-culture flasks to enrich the concentration of adipocyte precursors. Researchers are developing more efficient isolation methods that use advances in liposuction and reconstructive plastic surgery; in this process, plastic surgeons use a cannula to infuse subcutaneous adipose tissue with an anestheticcontaining saline solution. The procedure produces aspirations of adipose-tissue fragments containing viable adipocyte precursors within the SVF. Following collection of tissue samples, centrifugation at 1,200 G optimizes the ASC fraction recovered from the liposuction aspirate. However, surgical procedures involving ultrasound-assisted liposuction have shown adverse effects on the quantity of viable cells abstracted via the procedure. Once isolated, ASCs double in vitro within two to four days. Since massive quantities of tissue must be handled to isolate significant quantities of desired cells, methods such as rotating, temperature-controlled collagenase incubators, and bag-within-a-bag sieves are being tested to assist in procuring the desired cellular fraction from liposuction aspirate samples. Thanks to the development of these novel techniques for efficiently isolating ASCs, larger-scale commercial isolation methods are in development and becoming a realistic possibility for clinical application.

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Purification and Identification To identify a stem cell, researchers evaluate the presence and absence of various surface marker proteins, or antigens, which are important for immune recognition by leukocytes. Studies analyzing the immunophenotype of cells abstracted from liposuction aspirate find much consistency in the surface markers of these adipose-derived cells, indicating that there is, in fact, a unique population of adipocyte precursors present within the aspirate. Among the antigens used to identify stem cell populations, ASCs have been identified as positive for CD29, CD34, CD54, CD90, CD105, CD166, and human leukocyte antigen (HLA)-ABC markers; they are negative for CD31, CD45, CD106, CD146, and HLA-DR markers. Additionally, ASCs may be purified from the heterogeneous subcutaneous adipose and vascular fraction SC+VF by exploiting their plastic-adherent characteristic and their multipotent differentiation potential. Multipotency of ASCs It is now well known that adipose-derived stem cells can differentiate into adipocytes, chondrocytes, and osteoblasts. Not only are they capable of this multipotency, but their clonogenicity has been established as well. That is, a single ASC has been shown capable of cloning itself and then further differentiating into multiple lineages, eliminating the possibility of multiple precursors producing the respective observed lineages. Beyond the mesodermal tripotency seen in conditions of pathologic calcification, researchers have more recently successfully induced in vivo ASC differentiation into neurogenic ectodermal cells consistent with neurons, oligodendrocytes, and Schwann cells. Other confirmatory studies have elicited ASC commitment to hepatogenic, pancreaticogenic, myogenic, hematopoietic supporting, and endodermal lineages by targeting various chemical inductive factors to the cells. Both endogenous and synthetic chemicals have successfully induced differentiation into determinate cell lineages. Cardiomyocytes have been induced using the iron transporter, transferrin, interleukins 3 and 6, as well as vascular endothelial growth factor. Endothelial cells, on the other hand, result from ASC exposure to basic fibroblast growth factor, and epidermal growth factor.

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Adipose: Development and Regeneration Potential

Differentiation into many cell lineages indicates that ASCs contain vast potential, perhaps far wider than that initially suggested by pathological evidence; it is even theorized that these cells are pluripotent, much like embryonic stem cells. Clinical Trials With Therapeutic ASCs Compared to hematopoietic stem cells, ASCs exhibit greater long-term genetic stability and are more immunoprivileged (i.e., evidence suggests they are effective at preventing severe graftversus-host disease). Therefore, presently, these cells seem potentially safer and more effective than their adult stem cell counterparts. Currently, dozens of clinical trials are underway to evaluate their efficacy in various regenerative treatments. Immunosuppressive studies have shown that ASCs suppress T-cell–mediated immunity and inflammation while activating regulatory T cells, which downregulate inflammatory mediators and reduce the tissue response of inflammatory cells. Other clinical trials are investigating applications in cardiovascular and hepatic disease, type 1 and 2 diabetes, amyotrophic lateral sclerosis, multiple sclerosis, immunosuppression, limb ischemia, and bone reconstruction. Regenerative capacities for lumpectomy patients and perianal fistulas are also being investigated. Current theories on the mechanism of action for ASCs include the paracrine secretion of signaling molecules like cytokines or growth factors that would guide the differentiation of local cells to the necessary type to speed recovery; in the treatment of ischemia, ASCs may help remove toxins by producing antioxidants and free-radical scavengers to aid in tissue recovery. While many clinical trials are underway to address the safety and efficacy of ASCs, much remains to be seen regarding the potential these versatile cells have in therapeutic and regenerative settings. The vast array of possible treatments being explored will undoubtedly continue to revolutionize the management of disease. Krishna S. Vyas Brett Austin University of Kentucky College of Medicine See Also: Adipose: Development and Regeneration Potential; Adipose: Stem and Progenitor Cells in

Adults; Pluripotent Stem Cells, Embryonic; Stem Cell Potency. Further Readings Gimble, Jeffrey M., et al. “Adipose-Derived Stem Cells for Regenerative Medicine.” Circulation Research, v.100 (2007). Jurgens, W., et al. “Effect of Tissue-Harvesting Site on Yield of Stem Cells Derived From Adipose Tissue: Implications for Cell-Based Therapies.” Cell Tissue Research, v.332 (2008). Lindroos, B., et al. “The Potential of Adipose Stem Cells in Regenerative Medicine.” Stem Cell Reviews and Reports, v.7/2 (June 2011). Zuk, Patricia A. “The Adipose-Derived Stem Cell: Looking Back and Looking Ahead.” Molecular Biology of the Cell, v.21 (2010).

Adipose: Development and Regeneration Potential Human adipose tissue serves as an important endocrine and metabolic organ. Adipose tissue is a complex tissue composed mainly of mature adipocytes surrounded by a connective tissue matrix, in addition to stromovascular cells, nerve tissue, and immune cells. Together, these components play an important role in insulating the body, storing energy as lipids, and producing and metabolizing hormones. By secreting factors such as leptin, resistin, estrogen, and cytokines, adipocytes act as the major component of a highly active endocrine organ that targets various tissues in the body to maintain homeostasis. A lack or complete absence of adipose tissue (lipodystrophy) or overproduction of adipose tissue (obesity) can result in metabolic complications such as type 2 diabetes, insulin resistance, hepatic steatosis, and hypertriglyceridemia. The plastic nature of adipose tissue, with its regenerative properties and ability to expand and contract in response to shifts in energy balance, is most evident in the obesity epidemic. For many years, scientists and clinicians have investigated the development of adipose tissue at the cellular level; however,



Adipose: Development and Regeneration Potential

with modern biotechnological advances in stem cell research, the study of adipogenesis has been focused on the discovery and function of adiposederived stem cells (ASCs). Capable of differentiating into cells of nonmesodermal and mesodermal origin, ASCs serve as an important target for adipose tissue engineering and regenerative medicine. Adipose Tissue: A Source of Multipotent Stem Cells Stems cells are cell populations that possess multilineage potential, self-renewing capacity, and long-term viability. Originating from the stroma of bone marrow, mesenchymal stem cells (MSCs) have been widely studied as an example of adult stem cells that are capable of differentiating into chondrocytes, osteoblasts, adipocytes, and myoblasts in vivo and in vitro. While MSCs are promising candidates for disease management and mesenchymal defect repair, the use of MSCs in the clinic has been limited due to complications associated with morbidity, pain, and low cell count/tissue volume upon harvest. In recent years, researchers have focused attention to adipose tissue as an alternative source of adult stem cells. Much like bone marrow, adipose tissue is derived from mesenchymal origin and contains an easily isolated stroma. ASCs exhibit stable proliferation and growth kinetics in culture and in the presence of specific inducing factors can differentiate into chondrogenic, osteogenic, adipogenic, and myogenic lineages. Due to the ubiquitous nature of human adipose tissue, large quantities of ASCs can be easily obtained with little patient discomfort or donor site morbidity. The multipotent nature of ASCs is evident in various human pathologies. In children with progressive osseous heteroplasia (POH), an autosomal dominant genetic defect that causes ectopic bone formation within subcutaneous adipose depots, chondrocytes and osteoblasts can be found within colonies of adipocytes. Histologic analysis implies a tripotent capacity of ASCs to differentiate into cells of chondrogenic, osteogenic, and adipogenic origin. Obesity also presents additional evidence supporting the presence of stem cells in adipose tissue. Adipocytes have a turnover rate ranging between 6 and 15 months. While various behavioral, genetic, and epigenetic factors can contribute to obesity, in vivo studies

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have demonstrated the existence of stem cell populations that replace mature adipocytes throughout the lifetime of humans. Adipose-Derived Stem Cell Isolation Humans contain five major types of adipose tissue: bone marrow, mammary, mechanical, brown, and white. Each type of adipose depot serves a unique biological function and contains a distinct stem cell profile. White adipose tissue contains higher amounts of multipotent stem cells compared to brown adipose tissue, with subcutaneous depots providing higher yields of ASCs compared to visceral fat. Within subcutaneous white adipose tissue, greater numbers of stem cells have been harvested from arm regions compared to the abdomen, thigh, and breast. ASCs recovered from superficial abdominal regions were found to be the most resistant to apoptosis. Furthermore, ASCs from younger donors have demonstrated greater cell adhesion and proliferation compared to older donors. It has yet to be determined which adipose tissue depot serves as the optimal location for stem cell recovery. Samples of subcutaneous adipose tissue are often obtained from subjects under local anesthesia. Current methods for isolating ASCs depend on collagenase digestion of tissue followed by centrifugation to isolate primary adipocytes from the stromal vascular fraction (SVF). ASCs display morphology similar to fibroblasts, which makes phenotypic identification difficult, and do not exhibit the intercellular lipid droplets that are found in adipocytes. Isolated ASCs are grown in monolayer culture utilizing specific cell culture techniques. Regeneration, Repair, and Tissue Engineering Traditionally, rehabilitation of injured or diseased organs and tissues has required tissue replacement through the use of autologous tissues since the body rejects tissue transplants with foreign antigen. With advances in modern biotechnology, researchers have placed an emphasis on developing tissue-engineered substitutes that are better suited in restoring, maintaining, and improving tissue function. The technology of tissue engineering involves an interdisciplinary field of physicians, engineers, and scientists who utilize adult stem cells to be directly implanted into the host or expanded in culture. In the latter technique,

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Adipose: Development and Regeneration Potential

stem cells are differentiated and combined with tissue-engineered scaffolds and growth factors to develop tissue and organ systems. Tissue engineering can be used as a tool for transplantation, rehabilitation, and reconstructive surgery. ASCs have the potential to regenerate and repair different types of tissues through a variety of mechanisms. ASCs can provide a beneficial impact on diseased or injured tissues/organs by producing and secreting soluble factors. Some of the growth factors and cytokines secreted by ASCs include hepatocyte growth factor (HGF), insulin-like growth factor (IGF-1), vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF-α), fibroblast growth factor (FGF), adiponectin, transforming growth factor-β (TGF-β) and other angiogenic, anti-apoptotic, and anti-inflammatory factors. Certain soluble factors can also promote tissue repair and wound healing by recruiting endogenous stem cells. This newly formed stem cell population acts in a paracrine manner that can be stimulated to differentiate along the lineage pathway required for tissue repair. ASCs can act as a viable source of free-radical scavengers, antioxidant chemicals, and chaperone/heat shock proteins. In injured regions such as ischemic sites, ASCs act in such a manner to clear the local environment of toxic substances, thereby improving recovery of surviving cells. Recent studies have demonstrated the capacity for bone marrow–derived MSCs to deliver mitochondria to injured cells and rescue aerobic metabolism. Comparable studies on ASCs may uncover a similar potential to contribute mitochondria. Therapeutic benefits of ASCs also differ between autologous (derived from the same individual’s body) and allogenic (derived from genetically dissimilar individual) transplantation. While autologous ASCs can be beneficial from histocompatibility, infectious, and regulatory perspectives, it is rare for patients to provide their own therapeutic cells. Researchers have determined that a human’s ASCs that are passaged in cell culture, compared to freshly isolated cells, have reduced surface histocompatibility antigen expression and suppressed immune reactivity when cultured together with allogenic cells. While this implies that passaged ASCs may not produce a cytotoxic T-cell response when transplanted in vivo, comprehensive testing is required before clinical implementation. If proven correct, the use of allogenic ASCs in

regenerative medicine holds the potential to lower costs of cell therapies, to improve availability of stem cells, and to reduce complications associated with organ and tissue failure. Cardiac Disease and ASC Cardioplasty In the United States, cardiovascular disease is responsible for 38% of deaths each year and remains the leading cause of death. The development of an effective cell-based therapy holds the potential to reduce medical expenses and improve patient outcomes in the context of heart failure and cardiac dysfunction. Experimental findings suggest a potential use of ASCs in cellular replacement therapy related to chronic, progressive cardiac disease and acute myocardial infarction (AMI). Studies have identified the ability of ASCs to differentiate to the cardiomyocyte lineage using 5-azacytidine in rabbits. In addition, human ASCs have shown a similar capacity for cardiac differentiation by reversibly permeabilizing their membranes then exposing the cells to cardiomyocyte extract from rats. In both cases, the cardiomyocyte lineage was evaluated based on positive immunostaining for a-actinin, myosin heavy chain, and cardiac troponin-I, spontaneous beating, and cell morphology (binucleated, striated cells). While transplantation of ASCs may improve cardiac function by differentiating and replenishing injured or lost myocytes, no studies have been evaluated in vivo. The Future of ASCs Deriving stem cells from adipose tissue has proven to be an efficacious, safe, and simple process with little donor site morbidity. Furthermore, stem cell yields from adipose tissue are far greater than most stem cell reservoirs in the human body. While they may be suitable candidates in regenerative medicine, various limitations still remain. One of the major concerns with the use of ASCs is that very few in vivo clinical trials have been conducted compared to the large number of in vitro preclinical studies. In addition, many scientific questions remain unclear. Firstly, the specific transcription factors and key molecular events that allocate ASCs to a particular lineage have not been identified. Secondly, evidence implies that the ability for ASCs to differentiate may depend on the anatomic source and the donor’s age and gender. Furthermore,



Adipose: Existing or Potential Regenerative Medicine Strategies

methods for large-scale manufacturing with appropriate quality control and quality assurance have yet to be developed. To fulfill expectations and to determine if ASC-based therapies can be successfully implemented in treatment, further investigation is required. Krishna S. Vyas Nicholas Chien University of Kentucky College of Medicine See Also: Adipose: Current Research on Isolation or Production of Therapeutic Cell; Adipose: Existing or Potential Regenerative Medicine Strategies; Heart Disease; Tissue Engineering (Scaffold); Tissue Regeneration: Humans. Further Readings Agarwal, Anil K., and Abhimanyu Garg. “Genetic Disorders of Adipose Tissue Development, Differentiation, and Death.” Annual Review of Genomics and Human Genetics, v.7 (2006). Gimble, Jeffrey M., Adam J. Katz, and Bruce A. Bunnel. “Adipose-Derived Stem Cells for Regenerative Medicine.” Circulation Research, v.100 (2007). Mizuno, Hiroshi, Morkiuni Tobita, and Cagri Uysal. “Concise Review: Adipose-Derived Stem Cells as a Novel Tool for Future Regenerative Medicine.” Stem Cells, v.30 (2012). Zachar, Vladimir, Jeppe G. Rasmussen, and Trine Fink. “Isolation and Growth of Adipose TissueDerived Stem Cells.” Methods in Molecular Biology, v.698 (2011). Zuk, Patricia A., Min Zhu, Peter Ashjian, et al. “Human Adipose Tissue Is a Source of Multipotent Stem Cell.” Molecular Biology of the Cell, v.13 (2002).

Adipose: Existing or Potential Regenerative Medicine Strategies A stem cell is a cell that has the ability to selfrenew and differentiate into one or more types of cells. Therefore, stem cells hold great promise for regeneration and repair of tissues. Recent

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study has focused on their use for the treatment of Parkinson disease, Alzheimer disease, cancer, myocardial infarction injuries, breast reconstruction, diabetes mellitus, autoimmune diseases, and much more. Unlike the embryologic stem cells that aroused much controversy, adipose-derived stem cells (ASCs) are derived from adults and are noncontroversial. Furthermore, research suggests ASCs are a better stem cell source than the conventional mesenchymal stem cells—the bone marrow stem cells (BMSCs). Shift From BMSCs to the ASCs Historically, BMSCs were the most frequently used mesenchymal stem cell pool. However, ASCs are more advantageous in several respects. The pool of ASCs is larger than that of BMSCs. They can be collected by liposuction with local anesthesia, whereas bone marrow acquisition is more invasive, requires general anesthesia, and carries a greater risk for mortality. Furthermore, clinical data show that ASCs have a higher proliferation rate than BMSCs. ASCs can grow to 90 percent confluence within three days compared to BMSCs, which can take a week to reach the same mark. Potential of ASCs ASCs are multipotent and mesenchymal in origin. Initially, ASCs were studied for differentiation into chondrogenic, myogenic, and osteogenic cell types. However, further research showed transdifferentiation capacity extending beyond the traditional mesenchymal lineage. ASCs are now known to be capable of skeletal myogenesis, cardiac myogenesis, neurogenesis, and angiogenesis. ASC use in regenerative therapy involves redirection from normal reparative function to generation of new tissue in areas that are diseased or received trauma. In addition to their proliferative capacity, ASCs also decrease inflammation and release growth factors, allowing focused healing. Their anti-inflammatory nature suggests potential for treating autoimmune and inflammatory diseases, such as rheumatoid arthritis, inflammatory bowel disease, and graft-versus-host disease. Clinical Applications and Published Clinical Trials ASC therapy is gaining popularity. Most studies report no adverse effects and the majority of

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Adipose: Existing or Potential Regenerative Medicine Strategies

outcomes were beneficial. However, rigorous trials are lacking and most publications are case reports and noncontrolled studies. The clinical applications of ASCs discussed in this article are spinal cord injury; diabetes mellitus; breast reconstruction and augmentation; facial lipoatrophy; rheumatoid arthritis; multiple sclerosis; hematologic and immunologic disorders; complex perianal or enterocutaneous fistulas and tracheomediastinal fistula; bone tissue repair; cardiovascular disease; cancer; and musculoskeletal regeneration. Spinal Cord Injury Stem cells have been studied intensely for spinal cord injury because the damaged axons and neurotransmitter-producing neurons cannot be regenerated by the human body. As a result, individuals with spinal cord injury suffer loss of sensory and motor function below the site of injury. Scientists started working with stem cells with the hope that they would promote new regeneration of neurons to promote healing. Indeed, in 2011, eight patients with spinal cord injury who were treated with intravenous infusions of autologous ASCs were shown to have improved motor function after 12 weeks. Type 1 Diabetes Mellitus Type 1 diabetes mellitus occurs because of autoimmune attack on pancreatic cells. The number of beta islet cells is reduced as a result, leading to decrease in insulin and C-peptide production. ASCs were studied for their ability to regenerate pancreatic beta islet cells. In a study of ASC therapy administered to five patients with diabetes, results showed a 30% to 50% decrease in insulin requirements and increase in serum C-peptide levels during a follow-up period of 2.9 months. No adverse effects were noted. Breast Reconstruction and Augmentation and Facial Lipoatrophy It should come as no surprise that ASCs have the potential for adipose tissue regeneration. In 2008, ASCs were used successfully for breast augmentation. Normally, the body resorbs injections of unprocessed adipose tissues. However, when patients were injected with a mixture of ASCs and unprocessed adipose tissue, they retained the

volume over the next 12 months. Similar success was shown in facial lipoatrophy. Autoimmune Diseases ASCs have potential for treatment of autoimmune diseases. In 2010, there was a case report of ASC use in a 67-year-old woman with rheumatoid arthritis. She was treated with autologous ASCs isolated from liposuction; subsequently, she reported reduced joint pain and stiffness. Additionally, authors measured the levels of rheumatoid factor as a more objective measurement and noted a decrease after treatment. The patient had no side effects. ASCs have also been used for the treatment of multiple sclerosis, another autoimmune disease. Three patients with multiple sclerosis received intravenous infusions of ASCs, allogeneic CD34+ cells, and mesenchymal cells. Patients reported significant improvement of symptoms. Hematologic and Immunologic Disorders Researchers have also studied ASCs for the treatment of graft-versus-host disease, idiopathic thrombocytopenic purpura, and pure red-cell aplasia. Patients were given intravenous infusion of allogeneic ASCs. Treatment was successful in graft-versus-host disease and pure red-cell aplasia; in idiopathic thrombocytopenic purpura, remission was achieved. However, the effect of ASCs on alloreactivity in patients who have undergone solid-organ transplantation is not yet known. Fistulas Potential use of ASCs for fistulas has been demonstrated in treatment of perianal, enterocutaneous, and tracheomediastinal fistulas. To study the effect of ASCs on perianal and enterocutaneous fistulas, the fistulas of the patients were injected with autologous ASCs mixed with proteinaceous fibrin glue. Results of phase 1 and 2 clinical trials showed four times the healing compared to the control group. Again, no adverse effects were reported. To study the effect of ASCs on a patient with lung cancer-induced tracheomediastinal fistula, the patient’s fistula was injected with autologous ASCs mixed with fibrin glue. Epithelialization of the fistula was observed three months later and was completely closed one year after treatment. This case



Adipose: Major Pathologies

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is particularly encouraging, as fistula progression into blood vessels occurs frequently and is often fatal. No side effect was noted.

should be used for each procedure, and the safe number of stem cells that can be injected into different organs will have to be determined.

Bone Tissue Repair In 2004, there was a case report on a sevenyear-old girl who had a calvarial defect from a severe head injury. The first attempt at treatment, fixation of calvarial fragments via titanium miniplates, was unsuccessful. She was then treated with a mixture of autologous ASCs and autologous bone from the iliac crest. Three months after the surgery, computed tomography scan confirmed successful calvarial bone formation.

Krishna S. Vyas Kristine Song University of Kentucky College of Medicine

Cardiovascular Diseases and Cancer Not all studies with ASCs have shown positive results. Study of ASCs for treatment of acute myocardial infarction and cancer are two examples where results have been inconsistent. Musculoskeletal Regeneration (Clinical Study on Animal Models) Musculoskeletal regeneration is an area of intense research because there is a limited pool of muscle progenitor cells, called satellite cells. Therefore, ASCs were used as a potential therapy for muscular disorders. In 2006, intravenous injection of allogeneic ASCs was shown to restore muscle function in murine muscular dystrophy. Successful use of ASCs in intervertebral disc regeneration has been also reported. In addition, topical administration of adipose stem cells on rabbits’ tendons accelerated tendon repair rate and tensile strength was increased, supporting the transdifferentiation potential of the ASCs in vivo and in vitro. Conclusion Though their effectiveness is still unproven, treatment with ASCs in regenerative medicine appears promising. However, their benefit in the treatment of cancer is particularly weak and presents a major concern, since ASCs secrete cytokines that may affect cancer metastases. More research is needed for conclusive evidence, and further work will be required to determine the safety of ASCs. Likewise, standard protocols for ASC studies do not exist yet. The ideal procedure for acquiring ASCs, the optimal number of stem cells that

See Also: Adipose: Development and Regeneration Potential; Bone: Existing or Potential Regenerative Medicine Strategies; Pancreatic Islet Transplant; Spinal Cord Injury. Further Readings Gir, P., et al. “Human Adipose Stem Cells: Current Clinical Applications.” Plastic and Reconstructive Surgery, v.129/6 (2012). Lindroos, B., et al. “The Potential of Adipose Stem Cells in Regenerative Medicine.” Stem Cell Review, v.7/2 (2011). Tobita, M., et al. “Adipose-Derived Stem Cells: Current Findings and Future Perspectives.” Discovery Medicine, v.11/7 (2011). Zhu, Y., et al. “Adipose-Derived Stem Cell: A Better Stem Cell Than BMSC.” Cell Biochemistry and Function, v.26/6 (2008).

Adipose: Major Pathologies Adipose tissue consists of adipocytes, a dynamic and highly regulated population of cells, and a stromal vascular fraction, which includes preadipocytes. Adipogenesis results in the generation of adipocytes from preadipocytes, which arise from a multipotent stem cell of mesodermal origin. This article focuses on stem cells as they relate to adipogenesis and how the dysfunction of adipogenesis is responsible for the role of adipose cells in the development of pathology. Lipodystrophy Patients with lipodystrophy have a variable lack of adipose tissue, with the severity of the pathology being determined by the magnitude of fat absence. Lipodystrophies are categorized

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Adipose: Major Pathologies

as genetic or inherited. Genetic lipodystrophies are monogenetic disorders caused by mutations in a gene. Inherited lipodystrophies have several identified genes as a cause, with congenital generalized lipodystrophy and familial partial lipodystrophy being the two main subtypes. Some of these mutations responsible for these diseases code for genes in pathways involved in the development of multipotent mesodermal stem cells to preadipocytes, as well as for the differentiation of these preadipocytes to adipocytes. Consequently, failed adipogenesis from stem cells can be responsible for the development of this disease in some cases. This lack of adipose tissue, due to failure of adipogenesis or another cause, results in inadequate storage of free fatty acids (FFA), which results in increased circulation of FFA and lipotoxicity. Lipotoxicity is characterized by ectopic fat deposition in non-adipose cells, including the pancreas. Ectopic deposition contributes to insulin resistance and deposition in the pancreas creates beta cell dysfunction; these two conditions are necessary for the development of type 2 diabetes mellitus. Obesity During positive caloric balance, adipocytes initially undergo hypertrophy. The body’s appropriate response to this is to trigger adipogenesis, which allows for the generation of additional fat cells. This maintains normal adipose tissue physiologic function while increasing the body’s energy stores. However, if this adipogenesis is impaired, the hypertrophied adipocytes have pathogenic potential due to the resulting adipose tissue dysfunction. This leads to a state of hypersecretion of pro-artherogenic, pro-inflammatory, and  prodiabetic adipocytokines, which is accompanied by a decreased production of adiponectin, a protein involved in the regulation of glucose levels as well as fatty acid breakdown. Therefore, obesity can cause adipose tissue dysfunction, but not all obese individuals have a loss of adipose tissue architecture and function. The dysfunction depends on the failure of adipogenesis and the ensuing hypertrophy of the cells. Hypertrophied adipocytes tend to expand to have a diameter that is greater than the diffusion limit of oxygen. This leads to hypoxia-induced expression of transcription factors prompting

angiogenic factor expression. This decreases the adiponectin promoter and PPARg activity, reducing the stability of adiponectin mRNA, and decreasing adiponectin expression. At the same time, leptin and PA-1 gene transcription is induced in adipose tissue. Leptin is one of the most important adiposederived hormones, regulating appetite, hunger, behavior, and metabolism. Hence, it appears that adipocytokine dysfunction is a result of cellular mechanisms responding to local hypoxia created by hypertrophied adipocytes after the failure of adipogenesis to create more fat cells for storage from the positive caloric balance. The importance of this deregulation and the pathology it causes will be elucidated throughout the rest of this article. Hypertrophied adipocytes, as well as total body weight, correlate with the number of macrophages in the adipose tissue and this correlation becomes even stronger when the adipose tissue in discussion is visceral. This increase in macrophages in adipose tissue may be the sentinel event for much pathology. Adipocytes that are large tend to release more free fatty acids (FFAs), which bind to the toll-like receptor 4 (TLR-4) on macrophages, stimulating NF-KB activation. This leads to increased TNF-a secretion by these macrophages. TNF-a can then activate the hypertrophied adipocytes causing increased lipolysis and secretion of interleukin 6 (IL-6), intracellular adhesion molecule-1 (ICAM-1), and macrophage chemo attractant protein-1 (MCP-1). ICAM-1 and MCP-1 are signaling molecules that cause monocyte diapedesis from blood to adipose tissue, where the monocytes will differentiate into macrophages. This signaling process between adipocytes and macrophages creates a vicious cycle that is amplified by the fact that adiponectin, which is now low, normally inhibits TLR-activated NF-KB activity. This process as a whole leads to a proinflammatory state. Systemic inflammation leads to increased cardiovascular risk due to the development of atherosclerosis. This is supported by the fact that people with preexisting inflammatory diseases, such as rheumatoid arthritis or lupus, have a dramatically increased risk of cardiovascular disease at a younger age and accelerated rates of atherosclerosis.



Type 2 Diabetes When insulin resistance increases, insulin production by pancreatic beta cells also increases; however, if this adaption fails, diabetes will ensue. An environment of insulin resistance is created in a couple of ways due to adipocyte dysfunction. As discussed above, the adipose tissue dysfunction due to failure of adipogenesis and the resulting hypertrophy produces TNF-a, IL-6, and FFA. These all induce serine phosphorylation of the insulin receptor substrate-1 and insulin receptor substrate-2. This phosphorylation reduces the insulin receptor substrates’ abilities to be phosphorylated. This inhibits the cascade that is normally signaled when insulin binds to the receptor, resulting in insulin resistance. Another mechanism of dysfunction results due to the aforementioned increase in FFA. The presence of more than normal amounts of FFA inhibits insulin sensitivity. The presence of insulin normally inhibits hormone-sensitive lipase, but with this inhibition removed due to FFA, lipolysis is uncontrolled. This mechanism is augmented since TNF-a also upregulates triglyceride hydrolysis in adipose tissue. Adiponectin also plays a role in contributing to insulin resistance. Adiponectin inhibits hepatic glucose production and increases FA oxidation. Therefore, the decrease in adiponectin due to failure of adipogenesis, leads to insulin insensitivity. All of these factors together create an environment for insulin resistance, which aids in the development of type 2 diabetes. In most studies, low adiponectin and elevated levels of other adipocytokines, such as TNF-a and IL-6, are associated with an increased risk of diabetes. This relates not only to their effects on insulin sensitivity but also to their effects in the pancreas leading to beta cell failure. Adipose Tissue in Vascular Disease The dysfunction of adipocytes due to failure of adipogenesis contributes to the development of vascular disease. Leptin upregulates Na/K ATPase pumps in the renal cortex and medulla and thus creates a leptin-provoked hypertension. Additionally, leptin increases sympathetic nerve activity to the kidneys and peripheral vasculature, creating an increased heart rate and elevated blood pressure. Dysfunctional adipocytes, in addition to the adipocytokines already mentioned, also produce

Adipose: Major Pathologies

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angiotensinogen and angiotensin II, which are part of the renin-angiotensinogen-aldosterone system (RAS) that contributes to salt-fluid retention and vascular tone. This increase in RAS also contributes to the decrease in adiponectin. Adiponectin is solely produced by adipocytes, and low plasma levels of adiponectin are predictors of future vascular disease. This leads to an increase in systemic blood pressures due to vasoconstriction and salt retention. Angiotensin II also can act on the endothelium to induce expression of VACM-1, ICAM-1, and MCP-1, and create local inflammation. All of this together creates atheromatous and hypertensive changes. Due to adipocyte dysfunction, PAI-1, a regulatory protein of the coagulation cascade, is also upregulated and this increases the risk of vascular disease. With this increase, there is an increase in clotting factor levels and platelet activation, in combination with a decreased rate of fibrinolysis. This results in a change in the balance between fibrinolysis and thrombosis, favoring a hypercoaguable state and the creation of microthrombi. In addition to thrombosis, an increase in PAI-1 also increases atherogenesis due to an increase in deposition of platelets and fibrous products to plaques. Additionally, the increase inhibits migration of vascular smooth muscle cells into plaques, resulting in plaques more prone to rupture. Metabolic Syndrome Not only do a positive caloric balance and the failure of adipogenesis lead to dysfunction, but the location of these dysfunctional cells also plays a huge role in determining the pathologic outcome. Intra-abdominal fat pads lead to an increased risk for the development of cardiovascular disease due to what is known as metabolic syndrome. Abdominal obesity, dyslipidemia, hypertension, and insulin resistance characterize metabolic syndrome. The aforesaid molecules mentioned in this article that increase due to adipocyte dysregulation have already been shown to demonstrate the ability to cause dyslipidemia, hypertension, and insulin resistance. These factors increase significantly more if they are secreted from visceral tissue. Additionally, the adipocytokines go directly to the liver, resulting in a significant increase in inflammatory cytokines produced by the liver as well. This all creates a far greater risk for developing

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Adipose: Stem and Progenitor Cells in Adults

cardiovascular disease than any of the individual components of metabolic syndrome on their own. Conclusion Adipose is an active endocrine organ that regulates lipid and glucose metabolism, serves as a storage depot for free fatty acids, and produces many cytokines and hormones involved in normal physiologic metabolism and pathologies, including lipodystrophy, obesity, diabetes mellitus, vascular disease, and metabolic syndrome. Understanding adipose tissue function and pathology can help to advance research and development for the management and prevention of human disease. Krishna S. Vyas Amanda Blau University of Kentucky College of Medicine See Also: Adipose: Cell Types Composing the Tissue; Adipose: Development and Regeneration Potential; Adipose: Stem and Progenitor Cells in Adults; Adipose: Tissue Function. Further Readings Berg, A. H. and P. Scherer. “Adipose Tissue, Inflammation, and Cardiovascular Disease.” Circulation Research, v.96/9 (2005). Harjer, G. R., T. W. van Haeften, and F. L. J. Visseren. “Adipose Tissue Dysfunction in Obesity, Diabetes, and Vascular Disease.” European Heart Journal, v.29 (2008). Payne, V. A., N. Grimsey, A. Tuthill, S. Virtue, S. L. Gray, E. D. Nora, and J. J. Rochford. “The Human Lipodystrophy Gene BSCL2/Seipin May Be Essential for Normal Adipocyte Differentiation.” Diabetes, v.57 (2008).

Adipose: Stem and Progenitor Cells in Adults Adipose tissues play major roles in storage and active regulation of metabolism. In addition to these functions, adipose tissue has properties that give it potential application for tissue regeneration or transfer. Adipose may be a source of

unique, pluripotent (possessing the ability to form into cells originating from any of the three germ layers: ectoderm, mesoderm, endoderm) stem cells. The utilization of stem cells and cytokines can lead to tissue repair and the regeneration of damaged tissues. Other multipotent (possessing the ability to differentiate into multiple but limited cell types) progenitor cells can be drawn in an undifferentiated state. Progenitor cells are considered to have already committed to differentiation on a specific cellular pathway. There may be fewer political, legal, and ethical issues with adipose stem and progenitor cells as compared to embryonic stem cell use. Multi-Lineage Potential Stem cells must have the ability to continually divide (self-renewal), maintain viability long term, and have the potential to differentiate. Stem cells extracted from bone marrow (mesenchymal stem cells) have shown multi-lineage potential through extensive study and have been suggested as alternatives to embryonic stem cells in mesodermal defect repair and disease management. However, issues with pain, morbidity, and low cell number during extraction impede the practical use of bone marrow stem cells. Like stems cells derived from bone marrow, adipose tissue is of mesodermal origin. Adiposederived stem cells (ADSCs) can differentiate in vitro (isolated studies in experimental biology) toward osteogenic (bone), adipogenic (fat), myogenic (muscle), and chondrogenic (connective tissue) lineages when treated with established lineage-specific factors. Studies have shown that ADSCs show lineage-specific genes to distinctive cell lines such as osteocytes or myocytes when stimulated to develop into different cells. ADSCs can differentiate into adipocytes, chondrocytes, and osteoblasts, a feature known as multipotency. A single ADSC is also capable of cloning itself and then further differentiating into multiple lineages, a capacity known as clonogenicity. For example, human ADSCs show in vitro evidence of differentiation along myocyte lineage pathways. When cultured with myocyte lineage factors, adipocytes fuse and express protein markers of skeletal myocyte lineage. This suggests that these cells have the potential to repair damaged skeletal muscle. ADSCs can also differentiate into



Adipose: Stem and Progenitor Cells in Adults

osteoblast-like cells by depositing calcium phosphate mineral into their extracellular matrix and expressing osteogenic genes and proteins. Evidence suggests that these cells have the potential to accelerate repair at fracture sites. The range of differentiation that ADSCs possess extends beyond bone, muscle, and connective tissue. There may be possibility of repairing gastrointestinal and urinary tract smooth muscle defects with ADSCs. Factors can also differentiate these cells along the cardiac myocyte pathway and may be a source of regeneration for cardiac tissues damaged from infarction or ischemic injury. Preliminary studies have also implicated ADSCs in the regeneration of the central and peripheral nervous system following traumatic injury. Adhesion proteins associated with hematopoietic stem cells can form on ADSCs, which can also secrete cytokines (substances secreted by cells of the immune system) and promote differentiation along the B-cell, T-cell, and myeloid (white blood cell) lineages. This possible application can extend to conditions that weaken patients’ immune systems such as those patients undergoing high-dose chemotherapy or suffering from inborn errors of metabolisms. Harvesting Adipose-Derived Stem Cells Adipose tissue is an exciting resource for tissue regeneration and soft tissue repair because it houses one of the richest reservoirs of stem cells in the human body. Thus, stem cells collected from adipose tissue do not need to be cultured in order to obtain a therapeutically vital number of cells. Wellnourished humans store excess calories in adipose tissue that increase cell volume and expansion of the number of differentiated adipose cells, suggesting that adipose tissue progenitor cells exist within adult fat tissue. ADSCs can also be harvested easily with little harm to the patient through the process of liposuction, making adipose stem and progenitor cells much more accessible than bone marrow cells. ADSCs cultured in vitro have shown consistent profiles of cell-surface proteins, which include adhesion proteins, receptor molecules, surface enzymes, extra-cellular matrix proteins and glycoproteins, skeletal proteins, hematopoietic (involved in blood formation) cell markers, complement regulatory proteins, and histocompatibility antigens (immune system components).

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Diagram showing stem cells and progenitor cells. Stem cells are undifferentiated biological cells that can differentiate into specialized cells that can replicate indefinitely to produce more stem cells. A progenitor cell has a tendency to differentiate into a specific type of cell—its “target” cell. (Wikimedia Commons)

The immunophenotype of ADSCs resemble other adult stem cells from bone marrow and skeletal muscle. Methods of harvesting the tissue have dramatic effects on the ability of the cells to proliferate and differentiate in culture. Several studies report a negative correlation between patient age and the yield of donor cells and proliferation. Many concerns remain for the standardization and optimization of methods for cell isolation, culture, and application. Future Development ADSCs may prove to be an ideal option for tissue engineering in regenerative medicine since they are self-renewable, plentiful, and easily accessible through minimally invasive procedures. Studies suggest that ADSCs can be used in the treatment of type 1 diabetes mellitus, obesity, cardiovascular disease, lipodystrophy, and neurodegenerative diseases. For example, ADSCs have the ability to be carriers for gene delivery vehicles through transduction, the process by which foreign DNA is introduced into another cell through a viral vector. In surgical application, ADSCs can aid with

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Adipose: Tissue Function

neovascularization of free fat grafts (transplanted adipose tissue). Much more preclinical research and development must be dedicated to ADSCs before they can be used in treatment. Optimizing methods to harvest and preserve viable adipose tissue is of vital importance, but patient safety must be the priority. Krishna S. Vyas Richard Taing University of Kentucky College of Medicine See Also: Adipose: Cell Types Composing the Tissue; Adipose: Current Research on Isolation or Production of Therapeutic Cells; Adipose: Development and Regeneration Potential; Adipose: Existing or Potential Regenerative Medicine Strategies; Adipose: Major Pathologies; Adipose: Tissue Function. Further Readings Brayfield, C., K. Marra, and J. P. Rubin. “Adipose Stem Cells for Soft Tissue Regeneration.” Handchir Mikrochir Plast Chir, v.42 (2010). Gimble, J. M. and F. Guilak. “Adipose-Derived Adult Stem Cells: Isolation, Characterization, and Different Potential.” Cytotherapy, v.5/5 (2003) Shen, Jie-fei, Atsunori Sugawara, Joe Yamashita, Hideo Ogura, and Soh Sato. “Dedifferentiated Fat Cells: An Alternative Source of Adult Multipotent Cells From the Adipose Tissue.” International Journal of Oral Science, v.3 (2011). Yarak, Samira. “Human Adipose-Derived Stem Cells: Current Challenges and Clinical Perspectives.” Anais Brasileiros de Dermatologia, v.85/5 (2010). Zuk, Patricia A., et al. “Human Adipose Tissue Is a Source of Multipotent Stem Cells.” Molecular Biology of the Cell, v.13 (2002).

generation, while white adipose tissue (WAT) is present in adults and is a highly metabolic, endocrine organ. Pathology can occur both from adipose tissue deficiency as well as excess. Brown Adipose Tissue (BAT) Non-shivering thermogenesis. Brown adipocytes utilize oxygen and lipids as substrates to produce heat. The functional thermogenic unit consists of a brown adipocyte maintained within a structural network of connective tissue with access to a rich blood supply and innervation. The vascular network serves the BAT by both delivering substrate and signaling molecules to the organ as well as carrying away the heat product to the body. Therefore, access to an ample vascular network is necessary in order to achieve maximal generation and distribution of the BATgenerated heat. Heat generation is achieved by a mitochondrial protein known as uncoupling protein-1 (UCP1) or thermogenin. It allows for combustion of fatty acids in the respiratory chain without the production of ATP; instead, heat is the form of energy that is released. Signal transmission. The ventromedial (VML) hypothalamic nucleus of the brain coordinates information regarding body energy reserves and body temperature. When a thermogenic demand is sensed by the VML, the information is relayed via the sympathetic nervous system. The neurotransmitter norepinephrine (NE) is released and binds β-3 adrenergic receptors in the BAT to trigger an intracellular cascade that eventually leads to the generation of heat and an increased body temperature.

Adipose: Tissue Function

Thermogenic demand. Pre-adipocytes represent a rapidly accessible stem cell population that can replicate and differentiate into mature BAT under situations of increased thermogenic demand.

The parenchyma of adipose tissue consists of adipocytes suspended in a connective tissue matrix, which functions as both a crucial endocrine organ as well as a site for metabolic activity. Two types of adipose tissue have been identified: brown and white. Brown adipose tissue (BAT) in humans is present at birth and provides non-shivering heat

White Adipose Tissue (WAT) Steroid hormone metabolism. Adipose tissue serves a crucial role in processing steroid hormones produced in the adrenal glands and gonads. This processing is referred to as “tissue-specific pre-receptor steroid hormone metabolism” and is necessary for full activation or inactivation of



the circulating steroid hormones. The enzymes required to perform this process are extensive and include cytochrome P450-dependent aromatase, 3β-hydroxysteroid dehydrogenase (HSD), 3αHSD, 11βHSD1, 17βHSD, 17α-hydroxylase, 5α-reductase, and UDP-glucuronosyltransferase 2B15. Aromatase is an especially important adipose enzyme in that it converts androgens into estrogens. In postmenopausal women, gonadal synthesis of estrogens becomes diminished and adipose tissue accounts for all of the circulating estrogen. Reservoir for energy storage. Despite the large capacity of adipose tissue to secrete proteins and metabolize steroid hormones, the major secretory product of WAT is fatty acids. Adipocytes store triglycerides internally as a lipid droplet through an enzymatic process. First, triacylglycerides absorbed from the diet or synthesized in the liver reach their storage site (adipose tissue) and are converted into fatty acids via the enzyme lipoprotein lipase (LPL). They are then combined with the metabolic glucose product glycerol phosphate to reform triacylglyceride inside the adipocyte. When the cell receives signals that the body requires use of the free fatty acids for energy, they are then broken down via an enzyme called hormone sensitive lipase (HSL) that breaks apart the stored triglycerides to release free fatty acids. HSL responds to hormones such as catecholamines and glucagon to increase the free fatty acid concentration in the plasma so that it can be utilized for energy. Therefore, the sympathetic nervous system is a primary modulator of triacylglycerol breakdown. Endocrine functions. Adipose tissue as an organ consists of several different tissue types including adipocytes, connective tissue, nerves, stromovascular cells, and immune cells. These tissues function in synchrony to express and secrete several hormonal and non-hormonal products including leptin, angiotensinogen, adipsin, acylationstimulating protein, retinol-binding protein, tumor necrosis factor alpha (TNFα), interlukin-6, plasminogen activator inhibitor-1, adiponectin, complement components, and resistin. Several of these mediators are discussed below.

Adipose: Tissue Function Secreted proteins. 1. Leptin is a polypeptide (16-kDa) containing 167 amino acids and has a structural configuration similar to that of cytokines. Although leptin can be synthesized in several sites of the body including the stomach, placenta, and mammary glands, the predominant site of its synthesis is in WAT. The primary role of leptin is to serve as a messenger to the body that the level of energy is at a sufficient state. Therefore, adipose tissue mass and nutritional status are the main mediators of leptin and directly correlate to circulating levels. These levels rapidly decline with caloric restriction and weight loss. Leptin can also be modulated by other chemical mediators: it is increased by insulin, steroids, and TNFα, and is decreased by β3-adrenergic activity, androgens, free fatty acids, growth hormone (GH), and peroxisome proliferator-activated receptor-ϒ agonists. 2. Genetically modified mice that have a recessive knockout of the leptin gene are referred to as ob/ob mice and are profoundly obese. The lack of circulating leptin leads to an absent detection of energy sufficiency and causes the mice to eat to excess. Therefore these mice are often applied as research models for type 2 diabetes. 3. TNFα is a transmembrane protein (26-kDa) that becomes biologically active after cleavage. Levels of TNFα positively correlate with obesity and insulin resistance. Induction of insulin resistance can be achieved in vitro and in vivo via chronic TNFα exposure. 4. Interleukin-6 (IL-6) is similar to TNFα in that it is a cytokine produced by adipose tissue that also is associated with obesity and insulin resistance, and circulating levels have been shown to decrease with weight loss. It also serves as a predictor of type 2 diabetes as well as cardiovascular disease.

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Adult Stem Cells: Overview

Adipose tissue excess (obesity). Associations of obesity are referred to as metabolic syndrome and are characterized by insulin resistance, hyperglycemia, dyslipidemia, hypertension, and prothrombotic and proinflammatory states. Adipose tissue deficiency (lipodystrophy). A deficiency of adipose is also associated with characteristics of metabolic syndrome. Krishna S. Vyas Christopher Areephanthu University of Kentucky College of Medicine See Also: Adipose: Cells Types Composing the Tissue; Adipose: Current Research on Isolation or Production of Therapeutic Cells; Adipose: Development and Regeneration Potential; Adipose: Existing or Potential Regenerative Medicine Strategies; Adipose: Major Pathologies; Adipose: Stem and Progenitor Cells in Adults. Further Readings Cannon, B. and Jan Nedergaard. “Brown Adipose Tissue: Function and Physiological Significance.” Physiological Reviews, v.84/1 (January 1, 2004). Kershaw, E. E. and J. S. Flier. “Adipose Tissue as an Endocrine Organ.” Journal of Clinical Endocrinology and Metabolism, v.89 (2004). Trayhurn, P. and J. H. Beattie. “Physiological Role of Adipose Tissue: White Adipose Tissue as an Endocrine and Secretory Organ.” Proceedings of the Nutrition Society, v.14/3 (2001).

Adult Stem Cells: Overview About 65 years ago, a team of researchers discovered that red bone marrow was composed of two types of stem cells: hematopoietic stem cells (HSCs) described as mesoderm-derived blood cells, and stromal stem cells. Cells of the mesoderm form one of the three primary germ cell layers of an embryo in its early stages of development, and give rise to other blood cells. Stromal stem cells, on the other hand, constitute the so-called skeletal or mesenchymal layer. The role of these stem cells,

which only make up a fraction of all stromal cells, is to generate cartilage, bone, and fat cells able to support the formation of fibrous connective tissue and blood. Despite these findings, most scientists remained convinced for a long time that the adult human brain was unable to produce new nerve cells. In the 1990s, however, researchers reached the conclusion that the matured brain did contain stem cells, capable of generating star-shaped glial cells called astrocytes, located in the spinal cord and the brain, and oligodendrocytes, which provide insulation and support to axons, long nerve fiber extensions present in the central nervous system (CNS) of some vertebrates. While hematopoietic stem cells only produce white blood cells, red blood cells, and platelets, adult stem cells, in contrast, mutate into different kinds of cells susceptible of dividing and reproducing indefinitely. What are adult stem cells (ASCs) all about? And more specifically, how do they differ from pluripotent stem cells, or rapidly dividing progenitor transit amplifying cells (TACs)? Why are they so important to science and regenerative medicine? What are the challenges, if any, associated to their use? By definition, “adult stem cells are undifferentiated cells, found throughout the body after embryonic development, that multiply by cell division to replenish dying cells and regenerate damaged tissue.” They are also known as somatic stem cells, found in young and adult animals, and humans. Many different types of stem cells arise at different locations in the human body, from adult or tissue-specific stem cells, to embryonic stem cells that exist only briefly in the early stages of tissue development. In addition to these, researchers have recently created induced pluripotent stem cells, or iPSCs. These are undifferentiated cells engineered from specialized cells, with characteristics almost identical to those of embryonic stem cells. Adult or tissue-specific stem cells are deemed to be multipotent, that is, capable of giving rise to a few mature cell types. Adult stem cells are present in many different tissues and organs, including brain, blood, vessels, skin, skeletal muscle, heart, testis, ovarian epithelium, and bone marrow. In the bone marrow, several millions of new blood cells arise every day from blood-forming stem cells. Scientists



have not been able to determine whether every mature organ includes stem cells. Tissue-specific stem cells are rare and often difficult to grow in culture and isolate. Of those, the blood-forming and hematopoietic stem cells residing in the bone marrow are the most studied. Induced pluripotent stem cells (iPSCs) are cells engineered to become pluripotent, that is, capable of forming multiple types of cell types. Although human iPSCs open up an exciting window into stem cell research, this technology is still in its infancy, and many related crucial questions remain unanswered. A promising avenue of stem cell research resides in the replacement of affected or damaged cells with healthy ones, an approach defined as regenerative medicine. This field has prompted scientists to investigate the use of fetal, embryonic, and adult stem cells derived from various specialized cell types—muscle, nerve, blood, and skin cells—to assess their use as potential treatment for various conditions. However, it is important to keep in mind that in some instances, the immune system itself may be the source of so-called autoimmune diseases that damage vital cells, such as the ones producing insulin in type 1 diabetes patients. The end goal of stem cell–based regenerative medicine—the restoration of the function of damaged or lost tissues and organs—can be achieved through different means such as the injection of stem cells engineered in the laboratory, or the administration of drugs susceptible of coaxing existing stem cells into carrying out a more efficient repair. However, in spite of the encouraging prospects presented by potential stem cell therapies, there are challenges in the use of stem cells for regenerative purposes. In adult individuals, tissue-specific stem cells are rare and tend to be difficult to isolate. Additionally, while adult stem cells hold the promise of self-regeneration in animals and humans, the fact that they only exist in minute quantities creates some hurdles in the sense that they must be identified in sufficient numbers in order to be usable for therapy. All this makes it harder to conduct effective clinical studies. Researchers from various laboratories are currently attempting to find ways to grow and collect large enough quantities of adult stem cells susceptible to generate specific cell types.

Adult Stem Cells: Overview

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Blood-forming stem cells make up only a tiny fraction of the bone marrow. Although, they can be isolated in the laboratory, these cells cannot be conserved for a long time. Some cells, such as skin stem cells, offer better expansion capabilities in the laboratory and are used for specific treatments like burns. Other types of stem cells, such as bone marrow cells, can be infused in the blood stream. Mesenchymal muscle and neural stem cells, on the other hand, present more challenging routes for administration. Another obstacle is the potential rejection by the immune system of stem cells originating from donors other than the patient. This sometimes leads to the need to harvest stem cells from the intended recipient of the related therapy. Finally, an added drawback of adult stem cells is their relative age compared to embryonic stem cells, which makes them more susceptible to DNA abnormalities caused by toxins, random errors, or environmental factors. All embryonic stem cells arise from young embryos and are usually genetically different from those of any potential recipient. They can therefore be rejected by the immune system, the reason why iPSCs collected from the patient’s cells through reprogramming constitutes such a major breakthrough. A major advantage of pluripotent cells is that they can be grown and expanded indefinitely in the laboratory. Therefore, in contrast to adult stem cells, sheer quantity will be less of a limiting factor. Another advantage of these cells is the large number of different cell types present in a given organ that they can generate. This enables the development of a multitude of tissue-engineering approaches aimed at reconstructing a variety of organs in the lab. Scientists are using many different methods of identification of adult stem cells. One of them is their labeling within a living tissue by means of molecular markers enabling the determination of the types of specialized cell they are susceptible to generate. Another procedure involves the extraction of cells from a living animal, their labeling in cell culture, and their transplantation into another animal to see whether these cells are restored inside their original tissue. One of the major tasks confronting researchers is to demonstrate that a single adult stem cell is able to produce a series of genetically identical cells

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Adult Stem Cells: Overview

which, in turn, would give rise to differentiated cell types. What do we currently know about stem cell differentiation? What are the pathways leading to such a process? In living animals, and as needed, adult stem cells have the ability to divide and give rise to mature cell types that feature the functions, shapes, and specialized structures of a given tissue. For instance, hematopoietic stem cells (HSCs) are known to produce all kinds of blood cells, including B or T lymphocytes, natural killer or red blood cells, basophils, neutrophils, eosinophils, macrophages, and monocytes. On the other hand, neural stem cells located in the brain generate three major cell types: oligodendrocytes, astrocytes, and nerve cells, while skin stem cells that line up the base of hair follicles and the basal layer of the epidermis give rise to keratinocytes. In the lining of the digestive tract, epithelial stem cells are embedded in crypts and produce goblet, absorptive, entero-endocrine, and paneth cells. Mesenchymal stem cells (MSCs)—multipotent skeletal stem cells, or stromal cells susceptible to differentiate into a variety of cell types—can give rise to a certain number of cell types, including bone cells (osteocytes and osteoblasts), fat cells (adipocytes), cartilage cells (chondrocytes), and stromal cells that are in support of blood formation. Transdifferentiation is generally defined as “lineage reprogramming,” a process during which a mature somatic cell transmutes into another without going through an intermediate pluripotent state. The adult stem cell types involved may then differentiate into other types of cells located in tissues or organs, differing from those expected to derive from the original cells’ anticipated pedigree. One such example is blood-forming cells, capable of differentiating into cardiac muscle cells. Isolated occurrences of transdifferentiation have been witnessed in some vertebrates, but, according to the scientific community, none has yet been observed in humans. In cases where certain adult stem cells could be “reprogrammed” into other types of cells, such capability provides a way to repair damaged cell types in the aftermath of a disease. It has been proven quite recently

through experimentation that insulin-producing cells damaged or lost due to diabetes can possibly regain functionality through the reprogramming of other pancreatic cells. In addition to “lineage reprogramming,” adult somatic cells can be reengineered to behave like embryonic stem cells (ESCs) through the insertion of pluripotency genes. For many years now, research on adult stem cells has triggered a great deal of interest and excitement among the community of scientists and clinicians. This is certainly due to the capacity these cells demonstrate to self-renew indefinitely, thus constituting a renewable source of tissue and cell replacement in the treatment of a series of diseases, and the potential regeneration of entire organs from a few cells. For over 40 years, bone marrow transplants based on the use of adult stem cells have made it possible to successfully treat cancers such as lymphomas, myelomas, and leukemia and genetic diseases such as thalassemias. This progress has opened new doors to regenerative therapy and has led to a surge in clinical trials relying on the use of adult stem cells. These developments are providing great hope for the treatment of conditions such as diabetes, myocardial infarction, congestive heart failure, and so forth. A new trend in the field of stem cell biology is the adoption of all-inclusive concepts illustrated by the definition of a flurry of new scientific terms. Notwithstanding this tendency, recent studies suggest that functional differences do exist between stem and so-called progenitor cells. Stem cells are called progenitors when they do not have the capacity to self-renew. In the past, developmental biologists referred to ancestral embryonic cells as precursors. For any particular cell in the embryo, there exists an ancestor (progenitor or precursor) cell that gives rise to it. The notion of transit-amplifying cells (TAC) also needs to be clarified in this constantly shifting biological landscape. The difference between TACs and progenitors is not always clear. Transit-amplifying cells might be defined as dedicated progenitors among adult stem cells. Progenitor cells are known to have potential uses in medicine. Researchers from the Boston Children’s Hospital are currently reviewing the potential of muscle and blood progenitor cells



in building blood vessels and heart valves, for instance. Adult stem cells are located in a specific microenvironment known as a niche, in which both adult stem cells and TAC stay under control during their differentiation and self-renewing processes. If the differentiation of adult stem cells can be monitored in a laboratory environment, such cells may serve as a basis of transplantationbased therapies, especially since, unlike embryonic stem cells, the use of human adult stem cells in research is not considered controversial: the cells are extracted from adult tissue samples rather than young human embryos bound to have been destroyed. It is true that adult stem cells do not carry the same ethical concerns, or generate the same level of controversy, as embryonic stem cells. However, the practical challenges involved in their use are real. As scientists continue to explore ways to successfully harvest adult stem cells, the public awaits new therapies for some of the more severe afflictions. Looking at the potential clinical applications of stem cells, scientists have reached the conclusion that stem cell treatments have the potential to make great impact on the general well-being of populations and individuals, physically, psychologically, and economically. Approximately 130 million people suffer today from some kind of degenerative, chronic disease. In this context, stem cell therapies hold great promise, in particular in the treatment of many conditions affecting the nervous system that usually result from a loss of nerve cells. However, because mature nerve cells cannot divide, they cannot be relied on to replace lost cells. These types of conditions do not offer any therapeutic options outside of the regeneration of damaged or lost nerve tissue. This is true of Parkinson’s disease, in which nerve cells secreting dopamine die; Alzheimer’s disease cells, in which neurotransmitters are depleted; or amyotrophic sclerosis; in which motor nerve cells responsible to activate muscles are destroyed. In primary immunodeficiency diseases such as AIDS, adult stem cells offer the promise of treating such conditions through stem cell therapy. Pluripotent stem cells, the master cells capable of generating cells from the three basic body layers, such as adult stem cells, can self-renew.

Adult Stem Cells: Overview

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In so doing, they are able to regenerate the missing immune cells at the basis of nearly all primary immunodeficiency illnesses. The transplantation of reconstituted stem cells using normal genes could therefore restore the immune function and provide a new quality of life to affected individuals. What are the challenges to the use of adult stem cells? For many years, adult stem cells have been used therapeutically in the form of bone marrow transplants. Nevertheless, the scientific community is still facing today a series of challenges that need to be overcome before stem cells can be deemed ready to effectively treat a wider range of diseases. Researchers are still attempting to grasp the unique molecular and genetic basis for the phenomenon enabling these cells to replicate endlessly. As we can see, challenges pertaining to the immune system constitute a significant impediment to the reliable application of stem cell therapies. Cell therapy surely provides exceptional prospects to disease treatment, yet the value of these technological accomplishments will only be fully realized once the therapeutic techniques underway are carefully applied to patients through clinical programs capable of ensuring efficacious and tangible results at a reasonable cost. Morenike Trenou Independent Scholar See Also: Embryonic Stem Cells, Methods to Produce; Pluripotent Stem Cells, Embryonic; Pluripotent Stem Cells, Germ; Stem Cell Markers. Further Readings Abraham, E. J., C. A. Leech, J. C. Lin, et al. “Insulinotropic Hormone Glucagon-Like Peptide-1 Differentiation of Human Pancreatic Islet-Derived Progenitor Cells Into Insulin-Producing Cells.” Endocrinology, v.143 (2002). Alison, M. R., R. Poulsom, R. Jeffery, et al. “Hepatocytes From Non-Hepatic Adult Stem Cells.” Nature, v.406/6793 (2002). American Diabetes Association. “Economic Costs of Diabetes in the U.S. in 2007.” Diabetes Care, v.31 (2008). Audet, J., C. L. Miller, S. Rose-John, et al. “Distinct Role of gp130 Activation in Promoting SelfRenewal Divisions by Mitogenically Stimulated

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Murine Hematopoietic Stem Cells.” Proceedings of the National Academy of Sciences of the USA, v.98/4 (February 13, 2001). Baeyens, L., S. De Breuck, J. Lardon, et al. “In Vitro Generation of Insulin-Producing Beta Cells From Adult Exocrine Pancreatic Cells.” Diabetologia, v.48 (2005). Baum, C. M., I. L.Weissman, A. S. Tsukamoto, et al. “Isolation of a Candidate Human Hematopoietic Stem-Cell Population.” Proceedings of the National Academy of Sciences of the USA, v.89 (1992). Bittner, R. E., C. Schöfer, K. Weipoltshammer, et al. “Recruitment of Bone-Marrow-Derived Cells by Skeletal and Cardiac Muscle in Adult Dystrophic mdx Mice.” Anatomy and Embryology (Berl), v.199/5 (1999). Boiani, M., S. Eckardt, H. R. Schöler, et al. “Oct4 Distribution and Level in Mouse Clones: Consequences for Pluripotency.” Genes and Development, v.16/10 (2002). Centers for Disease Control and Prevention. “National Diabetes Fact Sheet: General Information and National Estimates on Diabetes in the United States, 2005.” http://www.cdc.gov/diabetes/pubs/ pdf/ndfs_2005.pdf (Accessed April 24, 2008). Chen, J., C. M. Astle, and D. E. Harrison. “Development and Aging of Primitive Hematopoietic Stem Cells in BALB/cBy Mice.” Experimental Hematology, v./5 (1999). Childs, R., A. Chernoff, N. Contentin, et al. “Regression of Metastatic Renal-Cell Carcinoma after Nonmyeloablative Allogeneic PeripheralBlood Stem-Cell Transplantation. New England Journal of Medicine, v.343 (2000). Cutler, C. and J. H. Antin. “Peripheral Blood Stem Cells for Allogeneic Transplantation: A Review.” Stem Cells, v.19 (2001). De Filippo, R. E., J. J. Yoo, and A. Atala. “Engineering of Vaginal Tissue in Vivo.” Tissue Engineering, v.9 (2003). de Miguel, M. P., S. Fuentes-Julián, and Y. Alcaina, “Pluripotent Stem Cells: Origin, Maintenance and Induction.” Stem Cell Reviews and Reports, v.6/4 (2010). Doetschman, T., H. Eistetter, M. Katz, et al. “The in Vitro Development of Blastocyst-Derived Embryonic Stem Cell Lines: Formation of Visceral Yolk Sac, Blood Islands and Myocardium.” Journal of Embryology and Experimental Morphology, v.87 (1985).

Domen, J. and I. L. Weissman. “Hematopoietic Stem Cells Need Two Signals to Prevent Apoptosis; BCL-2 Can Provide One of These, Kitl/c-Kit Signaling the Other.” Journal of Experimental Medicine, v.192/12 (2000). Dor, Y., J. Brown, O. I. Martinez, et al. “Adult Pancreatic Beta-Cells Are Formed by Self-duplication Rather Than Stem-Cell Differentiation.” Nature, v.429 (2004). Dzierzak, E. “Embryonic Beginnings of Definitive Hematopoietic Stem Cells.” Annals of the New York Academy of Sciences, v.872 (1999). Dzierzak, E., A. Medvinsky, and M. de Bruijn. “Qualitative and Quantitative Aspects of Hematopoietic Cell Development in the Mammalian Embryo.” Immunology Today, v.19/5 (1998). Ema, H., H. Takano, K. Sudo, et al. “In Vitro SelfRenewal Division of Hematopoietic Stem Cells.” Journal of Experimental Medicine, v.192/9 (2000). Evans, M. J. and M. H. Kaufman. “Establishment in Culture of Pluripotential Cells From Mouse Embryos.” Nature, v.292/5819 (1981). Ferranninni, E. “Insulin Resistance Versus Insulin Deficiency in Non-Insulin-Dependent Diabetes Mellitus: Problems and Prospects.” Endocrine Reviews, v.19. (1998). Gallacher, L., B. Murdoch, D. Wu, et al. “Identification of Novel Circulating Human Embryonic Blood Stem Cells.” Blood, v.96/5 (2000). Guz, Y., I. Nasir, and G. Teitelman. “Regeneration of Pancreatic Beta Cells From Intra-Islet Precursor Cells in an Experimental Model of Diabetes.” Endocrinology, v.142 (2001). Hill, J. O. and J. C. Peters. “Environmental Contributions to the Obesity Epidemic.” Science, v.280 (1998). Hull, M. G., C. M. Glazener, N. J. Kelly, et al. “Population Study of Causes, Treatment, and Outcome of Infertility.” British Medical Journal, v.291/6510 (1985). King, H., R. E. Aubert, and W. H. Herman. “Global Burden of Diabetes, 1995–2025: Prevalence, Numerical Estimates, and Projections.” Diabetes Care, v.21 (1998). Kolios, G. and Y. Moodley. “Introduction to Stem Cells and Regenerative Medicine.” Respiration, v.85/1 (2013). Lee, C. S., D. D. De Leon, K. H. Kaestner, et al. “Regeneration of Pancreatic Islets After Partial

Pancreatectomy in Mice Does Not Involve the Reactivation of Neurogenin-3.” Diabetes, v.55 (2006). Lipsett, M. and D. T. Finegood. “Beta-Cell Neogenesis during Prolonged Hyperglycemia in Rats.” Diabetes, v.51 (2001). Minami, K., M. Okuno, K. Miyawaki, et al. “Lineage Tracing and Characterization of Insulin-Secreting Cells Generated From Adult Pancreatic Acinar Cells.” Proceedings of the National Academy of Sciences of the USA, v.102/42 (2005). Narayan, K. M., J. P. Boyle, T. J. Thompson, et al. “Lifetime Risk for Diabetes Mellitus in the United States.” JAMA, v.290 (2003). Oshima, Y., A. Suzuki, K. Kawashimo, et al. “Isolation of Mouse Pancreatic Ductal Progenitor Cells Expressing CD133 and c-Met by Flow Cytometric Cell Sorting.” Gastroenterology, v.132 (2007). Raimya, V. K., M. Maraist, K. E. Arfors, et al. “Reversal of Insulin-Dependent Diabetes Using Islets Generated in Vitro From Pancreatic Stem Cells.” Nature Medicine, v.6/3 (2000). Ratajczak, M. Z., E. Zuba-Surma, M. Kucia, et al. “Pluripotent and Multipotent Stem Cells in Adult Tissues.” Advances in Medical Sciences, v.57/1 (2012). Rossant, J. “Stem Cells from the Mammalian Blastocyst.” Stem Cells, v.19/6 (2001). Ryan, E. A., J. R. Lakey, B. W. Paty, et al. “Successful Islet Transplantation: Continued Insulin Reserve Provides Long-Term Glycemic Control.” Diabetes, v.51 (2002). Ryan, E. A., J. R. Lakey, R. V. Rajotte, et al. “Clinical Outcomes and Insulin Secretion After Islet Transplantation With the Edmonton Protocol.” Diabetes, v.50 (2001). Ryan, E. A., B. W. Paty, P. A. Senior, et al. “Five-Year Follow-Up After Clinical Islet Transplantation.” Diabetes, v.54 (2005). Scharp, D. W., P. E. Lacy, J. V. Santiago, et al. “Insulin Independence After Islet Transplantation Into Patient.” Diabetes, v.39 (1990). Seaberg, R. M., S. R. Smukler, T. J. Kieffer, et al. “Clonal Identification of Multipotent Precursors From Adult Mouse Pancreas That Generate Neural and Pancreatic Lineages.” Nature Biotechnology, v.22/9 (2004). Shapiro, A. M., J. R. Lakey, E. A. Ryan, et al. “Islet Transplantation in Seven Patients With Type 1 Diabetes Mellitus Using a Glucocorticoid-Free Immunosuppressive Regimen.” New England Journal of Medicine, v.343 (2000).

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Soria, B., F. J. Bedoya, and F. Martin. “Gastrointestinal Stem Cells: I. Pancreatic Stem Cells.” American Journal of Physiology, Gastrointestinal and Liver Physiology, v./2 (2005). Tan, S.-L., P. Doyle, S. Campbell, et al. “Obstetric Outcome of in Vitro Fertilization Pregnancies Compared With Normally Conceived Pregnancies.” American Journal of Obstetrics and Gynecology, v.167/3 (1992). Tsang, W. G., T. Zheng, Y. Wang, et al. “Generation of Functional Islet-Like Clusters After Monolayer Culture and Intracapsular Aggregation of Adult Human Pancreatic Islet Tissue.” Transplantation, v.83 (2007). UK Prospective Diabetes Study Group. “Overview of 6 Years’ Therapy of Type II Diabetes: A Progressive Disease” (UKPDS 16). Diabetes, v.44 (1995). Volarevic, V., B. Ljujic, P. Stojkovic, et al. “Human Stem Cell Research and Regenerative Medicine—Present and Future.” British Medical Bulletin, v.99/1 (2011). Xu, X., J. D’Hoker, G. Stangé, et al. “Beta Cells Can Be Generated From Endogenous Progenitors in Injured Adult Mouse Pancreas.” Cell, v.132 (2008). Zimmet, P., K. G. Alberti, and J. Shaw. “Global and Societal Implications of the Diabetes Epidemic.” Nature, v.414 (2001). Zulewski, H. “Stem Cells With Potential to Generate Insulin-Producing Cells in Man.” Swiss Medical Weekly, v.136/41–42 (2006). Zulewski, H., E. J. Abraham, M. J. Gerlach, et al. “Multipotential Nestin-Positive Stem Cells Isolated From Adult Pancreatic Islets Differentiate Ex Vivo Into Pancreatic Endocrine, Exocrine, and Hepatic Phenotypes.” Diabetes, v.50 (2001).

Advanced Cell Technology Advanced Cell Technology (ACT) is a biotechnology company that specializes in developing cellular therapies to treat human diseases and was one of the first companies to run an FDA-approved clinical trial based on embryonic stem cells. The corporate offices and principal laboratory for ACT are located in Marlborough, Massachusetts, where the company is headed by Ted Myles (interim

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president, chief financial officer, and executive vice president of Corporate Development) who began at ACT in June 2013, and Robert Lanza, MD (chief scientific officer), who began working at ACT in 1999. Lanza is also an adjunct professor at the Wake Forest University School of Medicine in the Institute of Regenerative Medicine. ACT owns or licenses over 150 patents, including a broad patent for producing retinal pigment epithelial (RPE) cells for degenerative retinal disease. ACT began working in animal cloning in the mid-1990s, but shifted its research focus to human cells in 1998, shortly after the first isolation of human embryonic stem cells (hESC). Michael West became ACT’s chief executive in 1998, and in 1999 bought the company. West recruited Robert Lanza to ACT, and the company focused on therapeutic cloning, a method of developing stem cell lines from a patient’s own cell, thus avoiding the potential for rejection of cells created from unrelated embryos. In 2001, ACT scientists published a paper in the online journal Biomed describing a method for cloning a human embryo. Thereafter, West appeared on the television program Meet the Press to discuss the paper, bringing publicity to the company. However, according to Corie Lok in a 2012 article in Nature, that announcement may have backfired because the ACT scientists’ accomplishments were not considered significant by the scientific community (in part because the embryo they produced stopped dividing far short of what would be required to derive stem cells), but did trigger a public and political reaction that confused hESC research and cloning. In order to raise funds, ACT merged in 2005 with the Utah-based company Two Moons Kachina and became a publicly traded firm. The company expanded and, in August 2006, Lanza and colleagues announced in Nature that they had developed a method to derive stem cells from a single cell removed from an embryo. This method could potentially allow stem cells to be produced without harming the embryo, but the embryos used in the reported study were destroyed in the process. According to Lok, this distinction was not made clear in the study or in press releases regarding the study and many news outlets reported that the company had developed a method to derive stem cells without destroying

an embryo. If this claim had been true, ACT’s process would avoid some of the ethical concerns surrounding stem cell research. When it became clear that ACT did not have a method for deriving stem cells without destroying the embryo, it hurt the company’s reputation and made it difficult to attract investors. ACT’s current research and development process has four main focuses, two of which are based on hESC. The first hESC-based therapy, RPE therapy, is intended to treat degenerative retinal disease. RPE therapy is currently undergoing Phase I/II clinical trials for adults (over 18 years) in the United States and the European Union as a treatment for Stargardt’s Macular Dystrophy and atrophic (dry) AMD (age-related macular degeneration). This phase of testing is primarily to determine the safety and toleration of the treatment, which involves the transplantation of hESC-derived RPE cells. The second hESC-based therapy in development is the hemangioblast platform for treatment of diseases and disorders of the circulatory and vascular system; this therapy, which is currently in the preclinical phase, is being developed by ACT in partnership with the Korean company CHA Biotech. A third ACT project currently in the preclinical phase is a method of manufacturing mesenchymal stem cells (MSCs) from renewable sources of pluripotent stem cells, which may be useful to repair damaged tissue. A fourth project in the preclinical phase is an effort to develop methods to treat corneal blindness and glaucoma using corneal endothelial cells. Other research focuses of the company include those related to immune rejection and graft-versus-host disease. In March 2014, ACT announced a breakthrough in its MSC project, by reporting a new technique to regenerate a replenishable population of MSCs from pluripotent stem cells. In a paper in Stem Cells and Development, Kimbrel and colleagues report that the new method can produce far more MSCs than methods based on deriving MSCs from bone marrow, lowering the need to constantly replenish the supply by finding more donors. MSCs, which are currently being evaluated to treat human disease in over 300 clinical trials, have the advantage of evading detection by the recipient’s immune system, and hence do not require the use of immunosuppressive drugs.

Advocacy



As reported by Heidi Ledford in Nature in January 2014, ACT was experiencing financial difficulties and was seeking financing to continue its clinical trials. One source of the difficulties was the payment of $4 million to settle charges by the U.S. Securities and Exchange Commission that ACT had illegally sold billions of shares of stock. In January 2014, ACT was also sued by the Wisconsin Alumni Research Foundation, a company with which ACT has a licensing arrangement, for breach of contract. Sarah E. Boslaugh Kennesaw State University See Also: Clinical Trials, U.S.: Eye Conditions; Embryonic Stem Cells, Methods to Produce; Heart Disease; Mesenchymal Stem Cells; Moral Status of Embryos; Retinal Stem Cells. Further Readings Advanced Cell Technology: Company Overview [web page]. http://www.advancedcell.com/company/ (Accessed April 14, 2014). Kimbrel, Erin A., Nicholas A. Kouris, Gregory Yavanian, et al. “Mesenchymal Stem Cell Population Derived From Human Pluripotent Cells Displays Potent Immunomodulatory and Therapeutic Properties.” Stem Cells and Development. Advanced publication ahead of print (March 20, 2014). http://online.liebertpub.com/ doi/abs/10.1089/scd.2013.0554 (Accessed April 14, 2014). Klimanskaya, Irina, Young Chung, Sandy Becker, et al. “Human Embryonic Stem Cell Lines Derived From Single Blastomeres.” Nature, v.444 (November 23, 2006). Ledford, Heidi. “Stem-Cell Company in Crisis: Financial Woes Threaten Advanced Cell Technology.” Nature.com: News (January 25, 2014). http://www.nature.com/news/stem-cellcompany-in-crisis-1.14591 (Accessed April 14, 2014). Lock, Corie. “Stem-Cell Research: Never Say Die.” Nature.com: News Feature (January 11, 2012). http://www.nature.com/news/stem-cell-researchnever-say-die-1.9759 (Accessed April 14, 2014). Rockoff, Jonathan D. “Stem-Cell Trial Without Embryo Destruction.” The Wall Street Journal (December 13, 2012).

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Advocacy Advocacy is a term that refers to the action of speaking out for or defending a position or viewpoint, a right or series of rights, or a need for resolution. Advocacy is not only about having a voice or opinion heard; it also hopes to influence an event or resolution on the side for which it is advocating. The advocate may work on behalf of an individual, a group of people, or a community. Advocacy is considered today one of the key actions in the practice of conflict resolution. There are many ways in which conflict between two or several parties can be resolved, depending upon whether the action engaged falls within the model for advocacy, mediation, conciliation, or conflict negotiation. As such, advocacy has been largely used in the fields of social justice, policy decision making, and community empowerment. As long as there have been disempowered or vulnerable people in need of help and people willing to speak out on their behalf—be it as good Samaritans, religious representatives, intellectuals, or just concerned neighbors and citizens— the practice of advocacy has always existed. The concept of advocacy as a formal process with methods and systems, a series of established approaches, and even professional representation is relatively new. It started to develop in the late 19th century when ideas of people’s rights began to change, along with notions of community care and social justice. The history of advocacy has developed differently in diverse cultural contexts. Some experts, for example, explain that in societies where individuality does not carry the same value that it does in Western cultures, and where there is a stronger emphasis on family and trust, advocacy forms have developed in a more interdependent model. In the United States, advocacy historically has served social justice causes. Antislavery advocates existed long before the Civil War, as did individuals who spoke for the rights of women. A strong voting rights movement has existed from the 19th century to this day, in which American organizations work to protect and broaden voters’ rights through legal means and education. Advocates speak out not only on behalf of human rights but also of behalf of rights of

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nonhuman beings. Not even a century ago in the United States, for example, abusing an animal, such as beating it to death, was in most cases acceptable and even legal. Today, however, after more than 100 years of animal rights work by humane treatment advocates, laws mandating ethical treatment of pets, circus animals, laboratory animals, animals meant for food, and even wildlife exist at the state and federal levels. Steady activism begun in the early 19th century has ensured that today there is widespread acceptance that nonhuman animals have moral rights. Health advocacy also has a long history in the United States, beginning with advocates for dignified treatment for the mentally ill, who until the late 19th century used to have, in effect, very few rights. Health advocates work to represent patients’ rights as well as the community as a whole, striving for transformative change in the health care system, better access to care, protection and expansion of patients’ rights, health education and wellness, and other related issues. At the international level, human rights advocates have been remarkably successful in promoting the enactment of new international laws; ensuring changes in human rights awareness, policies, and practices; and changing the framework of public debate worldwide. Advocates today come from a wide array of occupations and institutions: the government; the legal, medical, and other professions; disease-specific voluntary organizations, such as the American Heart Association; grassroots organizations; national health policy organizations; environmental and scientific advocate organizations; human rights and all areas of social justice; education and academia; the arts; the media; and many other areas. Advocacy today also plays a significant and expanding role in the sciences. Among the issues debated in reference to science advocacy are the boundaries and contexts of advocacy as applied to science; science advice in policy decision making; the norms, responsibilities, and parameters of such advocacy; the benefits and risks of advocacy for scientists and society; the ethical implications of participating in different models of advocacy; and the need for resources and awareness of advocacy for organizations, science, and society at large. Forms of Advocacy There are many ways to categorize advocacy and not all of them are mutually exclusive. One of

the most common is along models that gauge a continuum—or progression—of influence and actions. For example, an individual or a coalition of individuals with the same predisposition may act to influence others with a differing predisposition. As an effect of this action, the inclination and decision making of the others becomes closer to the predisposition of the influencing individual or coalition than it was before. Advocacy is usually somewhere in the middle of the influence and action continuum, with protest at one end— usually the beginning—and lobbying at the other. Advocates may be paid professionals or they may be individuals who decide to represent or join others and advocate free of charge. They may also be organizations. Two basic types of advocacy exist: case advocacy and cause or systemic advocacy. Case advocacy, known sometimes also as individual advocacy, refers to an individual or coalition of individuals who engage in case advocacy as selfadvocates or by engaging other advocates who represent or support their case. Such advocates work defending the rights of another individual or group of individuals, as well as speaking for them or representing their interests. It may be because a particular group of people are not able to defend their rights or they may believe themselves better represented by somebody with more experience and connections. Occasions arise, also, in which an individual or an organization may decide to advocate for another individual or group. An example of case advocacy might be an organization deciding to take up the rights of a same-sex couple who are denied the right to marry and take their case to court. Cause or systemic advocacy, also known as public advocacy, takes place when an individual or group advocates the necessity of bringing about systemic, structural, legislative, and policy changes. It can cover an issue at the local, regional, or national level. Rather than focus on the individual, this type of advocacy represents the rights and interests of a group with similar issues and concerns. For example, cause advocates represent the interests or defend the rights of the general public or a general category of people. Case advocacy focuses on a particular case, individual, or specific group. Cause advocacy, on the other hand, concentrates on advocating for a general category of people or the general public, for example, the



advocacy of issues relating to public safety. Therefore, an organization working on cause advocacy could work on issues related to workers, children, the elderly, or the environment. Quite often, advocate work takes place in the political arena. Political advocates understand complex structures of power and influence. In general, political advocacy is most effective when the advocate or advocate organization has influence in the locations of power. At the end of the continuum is the work of lobbyists, who focus on influencing government policy and legislation at the local and national levels. There are other forms of advocacy, and it bears stressing that the boundaries between them are not mutually exclusive. All human beings have the right to their own advocates. For this reason, when individuals take responsibility for advocating on behalf of themselves, it is known as self-advocacy. Most cases of advocacy, however, involve an individual or organization representing someone else. Support or peer advocacy, for example, occurs when the individual providing advocate representation has shared experiences similar to the experience of the individual whom he or she represents. When an individual has been given legal responsibility to represent and decide for others who cannot legally speak for themselves, such as a warden or a guardian of a minor or of an adult who has been deemed incompetent to selfrepresent, it is known as statutory advocacy. Decisions and representation by an organization or individual considered to have the necessary knowledge or expertise to make an informed decision on behalf of the public—or who have the best interests of the public in mind—are engaging in what is known as best interest advocacy. The public may not—and often does not—take part in this decision making process. Such is the case, for example, of consumer interest groups. There are individuals and organizations that specialize in advocacy. Specialist or professional advocacy is also known as legal advocacy. These may work, for example, advocating on behalf of patients’ rights under health commissions. On the other hand, when advocacy refers to low-level community activism, it is often called grassroots advocacy. Coalitions of concerned parents, neighbors, or citizens often join forces in order to gain a position of strength when it comes to working for change. Such groups may become more

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established and turn into a political, education, or other sort of activist organization. Environmental organizations such as Greenpeace and the Sierra Club, born from the efforts of groups of environmentalists and conservationists, respectively, may serve as an example of this phenomenon. When a group becomes formalized, the advocacy has progressed beyond a grassroots advocacy into a more organized form, and arguably with more expertise, influence, and power. One of the most important roles of contemporary advocacy is the empowerment of an individual or group. Advocacy aimed at empowerment supports or represents an individual or group who seeks redress or to file a complaint. Rather than taking over or acting for the people they represent, the goals of an empowering advocate include helping individuals to see themselves as proactive, that is, to see themselves as people with rights who have the skills and strengths to find solutions to their own problems. These advocates share their knowledge and skills so that the people they aim to assist can use them, and rather than consider themselves as leaders, they act as partners in finding solutions and driving transformation and sustainable change. Advocacy Practice Successful advocates can achieve multiple goals. They can influence public policy, legislation, and budget allocations, for example, by the able use of relationships, knowledge, the media, and awareness projects. Among the skills that effective advocates develop are sharing their skills and knowledge with the people for whom they advocate, educating them in the topics of interest to their situation, improving their confidence and ability to find appropriate solutions, and connecting them to useful people and resources. There are many approaches used by advocates today, and one of the most common is participative and strength-based approaches. Participative approaches include consulting honestly and profoundly with their constituents in order to ensure their willing participation and consent to the changes proposed. It also means that the experiences and knowledge of the people to be assisted are valued, respected, and taken into account. A strength-based approach understands that people bring personal strengths to all situations. People are capable of autonomy and growth, of transformational change, and, with the right support, capable

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of being the best experts in their own cases and causes. A strength-based approach relies on respect for people’s essential rights, dignity, and capacities. It is also goal oriented and focuses on future outcomes. Within this perspective, then, practicing a strength-based approach validates the experience of the individual or group seeking change by helping them focus on the solution and using their lived experiences, capabilities, skills, and resources in order to reach their own solutions to problems. In order for advocacy to be sustainable, expert advocates understand that establishing realistic goals is of paramount importance. The final goal should include developing a solid understanding between the complainants, or people seeking change, and the decision makers with whom they are engaging. The advocate should ensure that the issues and procedures are laid out in such a manner that they offer a reasonable degree of clarity and stability. By making issues easier to comprehend, an advocate can help build confidence and reduce anxiety among those seeking help if they find the process confusing or difficult. Finally, it is important to always bear in mind and promote the belief that change is possible. Even though not all advocacy models and advocated cases and causes are concerned with participative approaches and social transformation, the field of advocacy is inherently rooted in social justice. Whatever the approach taken, one of the main roles of the advocate is to raise awareness of a problem or injustice, that is, to educate others— from constituent communities to government officials and/or the public—about the particular issues of interest for those on whose behalf the advocate works. As such, advocacy has long been considered to be a key tool in achieving social justice in all fields and at all levels where it is practiced. Advocacy Today Among the advocacy fields of note today, two stand out for their significant expansion and public importance: science and social media. Many crucial public policy decisions today have strong science imperatives, such as stem cell research, cloning, climate change, environmental depredation, food safety, and others. Policy decision makers often request and benefit from the research and expertise of science professionals. However, whether scientists ought to advocate

specific projects and policies is today a matter of heated debate among scientists, academics, and the public. Scientists are viewed, increasingly, as playing a larger role than solely offering expert opinions. Some, instead, are assuming advocacy roles in specific policy decision making. Such a role could have important outcomes for government and sometimes even corporate policy decisions, as in the case of projects in private research institutions. Science has traditionally been expected to meet ideal standards for unbiased objectivity, neutrality, and impartiality. However, scientists are human and therefore meet such standards imperfectly; yet, they are still expected to constantly work toward producing solidly neutral advice, because science opinions carry great weight in many decision-making arenas. When scientists and science advisers promote advocacy science, some experts argue, such advice loses credibility. They may be inclined to slant scientific research results or advice by using information selectively to support their case. Others argue that all of society benefits when experts participate in public debate on policy issues. Well-prepared scientists can provide solid information from their scientific expertise, which may point out questionable facts or support developing policy issues and legislation. Some argue that there is always the risk that those experts may place their desired policy outcomes ahead of the basic principles of sound, objective science. In such a case, public debate and information is damaged because the factual basis of knowledge is biased and thereby distorted. Even worse, these issues might become a risk to public safety if some scientists and researchers actively advocate policies that permit the distribution of products that may be harmful to public health. Others, who support the importance of advocacy in science, as is the case of some who work for environmental concerns, for example, explain that there are many ways to increase the impact of science  on policy decision making without perverting scientific knowledge. Standard practices such as peer review by various independent experts; the alignment of scientific information and outcomes with social, ecological, economic information and results; and multidisciplinary advice on risks and costs, among other measures, should be able to control for biased information



and outcomes. These measures, some experts argue, would allow science experts and scientists to be active and engaged participants in policy processes and decision making without unethically leaning toward preselected results. Nevertheless, the debate over the  boundaries between advocacy and science continues, as do concerns over how and in which contexts science experts should influence policy outcomes. Advocacy science today is discussed in many fields, such as environmental concerns, climate change, public health issues, and food safety standards. Among recent important issues that have caused advocates to debate for and against them are topics such as the stem cell research debate. Stem cell advocates have long worked to ease federal restrictions on stem cell research and pressure the federal government, through the National Institutes of Health and the Food and Drug Administration, to expand grant investment in stem cell research and establish safety guidelines for embryonic stem cell therapies, respectively. Advocates argue that stem cell treatments offer the possibility to bring affordable cures for many human diseases that are, to date, high in cost and suffering. There are many ways in which scientists can participate in policy making. For example, in order to deal ethically and appropriately with the many issues arising from new medical scientific technology, President Barack Obama instituted the Presidential Commission for the Study of Bioethical Issues (Bioethics Commission) in 2009. Presidential commissions have a long history and differ in topics of study and methodology, depending upon presidential appointment and the topics of importance of the day. The Bioethics Commission comprises a group of scientists and science experts in different fields, such as science, medicine, ethics, religion, engineering, and law. These experts advise the president on issues related to biomedicine and areas of science and technology associated with biomedicine. It provides a platform for scientists and experts to weigh in on policies meant to ensure that scientific research, health care practices, and related new technologies are developed in an ethically responsible and socially safe manner. Some of the issues up for debate in science advocacy today, besides the nature of advocacy in the science fields, for example, run along ethical imperatives, such as the borderline between patient

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protection and patient choice, patient information, genetic engineering and food safety, and euthanasia and cloning, among other issues. To date, advocates, science professionals, and ethics experts continue to build frameworks for debate that can be used in different fields to further these issues. Social media advocacy is a cutting-edge trend in the field of advocacy. It has not only transformed and globalized the practice but also interconnected advocates and advocate groups, vertically and horizontally, more than ever before. The phenomenon has transcended specific causes and language barriers, creating active cross-cultural and transnational global networks of activism and advocacy. These interconnections often include civil society and government contacts that emulate the development, outreach, and fundraising organizational work in the field. However, Internet speed and social media networks today allow advocate work to expand at a speed and to a reach never achieved before. When the digital phenomena of global social networks became widespread, their use as traditional publishing media platforms was still deemed mostly as a limited or negligible channel to engage with the public—and more specifically, interested stakeholders—in a meaningful way. The perceived incapability of social networks as a way of gaining respectful public attention through digital means made it unattractive to people interested in gaining the trust of their constituents and the public at large. Today, social media platforms comprise a profoundly different medium than it was at their inception. In effect, social media are more engaging, attractive, demanding, and harder to manage than traditional media. As the reach of traditional media channels declines, private and public institutions have opened up to the idea that they must engage differently with parties of interest and adopt innovative channels of communication to connect with their constituents and general public. This has given rise to the phenomenon of social media advocacy. Moreover, during the last decade, as advocate activists, professionals, and organizations increasingly try to satisfy the public preference for more authentic and personalized ways of reaching out, the role of personalized social media connections has become increasingly crucial. Many users have found that social media allow them to build

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connections and dialogue with other members of their social media networks, especially on topics of mutual interest. The fact that this can be managed both at the local level and worldwide, with access to free translation digital programs, greatly enhances its possibilities for advocacy. Another benefit of social media is that not only are they user friendly but they also offer the availability of multimedia convergence, and a measurable impact for very little money. Therefore, they constitute a tool that individuals and grassroots organizations can use as effectively as professional advocacy groups. Social media, however, bring with them new responsibilities. Users must be aware of the double-edged impact of publications if they become viral and must exercise extraordinary prudence and care in their publications and interactions. The expansion of social media has brought with it the realization that organizations own a limited amount of social capital, and an error in social media can cause exponential damage. Trudy M. Mercadal Florida Atlantic University See Also: Christopher & Dana Reeve Foundation, The; Cloning, Ethics of; Congress: Votes and Amendments. Further Readings Bhattacharya, D. Public Health Policy: Issues, Theories and Advocacy. Hoboken, NJ: Jossey-Bass, 2013. Hoefer, Richard. Advocacy Practice for Social Justice. Chicago, IL: Lyceum Books, 2011. Jansson, Bruce R. Improving Healthcare Through Advocacy. A Guide for the Health and Helping Professions. Hoboken, NJ: Wiley, 2011.

Alabama A 2012 Gallup poll found Alabama the most conservative state in the United States, with more than half of those polled self-identifying as conservative. This ideological bent is reflected in the state’s 2014 Healthcare Rights of Conscience Act that gives Alabama health care providers the right to refuse

to participate in abortions, human cloning, human embryonic stem cell research, and sterilizations if their objections are submitted in writing and placed on file prior to being asked.  Paradoxically, Alabama is also the site of exciting stem cell research and the home of the second-largest biotechnical research park in the nation. Highlighting the work done with adult stem cells has allowed the state’s research institutions to demonstrate that the conservative majority can support stem cell research without violating their principles. The Alabama Medical Institute, an independent, privately funded nonprofit organization, is committed to raising funds for politically riskier work in regenerative medicine and embryonic stem cell research. The University of Alabama at Birmingham (UAB) is the largest of the state’s seven research universities and the institution most heavily invested in stem cell research. Stem cell biology is a major division of UAB’s biochemistry and structural biology graduate program. Faculty members in the department have particular interests in stem cell self-renewal and lineage specification of adult and pluripotent stem cells. The stem cell biology group at UAB expanded in 2011 when the UAB Stem Cell Institute was established. Also in 2011, UAB acquired from SANYO (now Panasonic Healthcare) the first cell-processing workstation in the United States. The self-contained unit, which has been described as “a clean room in a box,” contains all the necessary equipment required to manufacture cells for cell therapy in a sterile environment. The unit is used in the stem cell biology group by researchers such as Tim Townes, professor and chair of the department of biochemistry and molecular genetics. Townes developed the first practical animal model for sickle cell disease in 1997. A decade later, he and his team, in collaboration with researchers at the Massachusetts Institute of Technology, took skin cells from mice with sickle cell disease and converted the cells into induced pluripotent stem cells (iPS) and genetically corrected the sickle mutation. They then transformed the corrected iPS cells into bone marrow cells and transplanted them into the diseased mice and cured sickle cell disease in the mouse model. Other researchers whose work has been enhanced by the cell-processing workstation include Lawrence Lamb, professor of medicine and director of the UAB cell therapy laboratory,



and Fred Goldman, professor of pediatrics at UAB and director of the Lowder Blood and Marrow Transplant Program at the Children’s Hospital of Alabama. Lamb’s research has shown that gamma delta T cells, a small component of the immune system, when present in large numbers, will increase survival for patients with leukemia. Goldman’s research uses iPS cells for dyskeratosis, a rare progressive bone marrow failure syndrome, and other nonmalignant blood disorders. Biotechnology in Alabama With $4.87 billion in annual research and development expenditures in 2012, Alabama ranks 12th in the nation for research revenue in life sciences and biotechnology, behind both Georgia and North Carolina. Accelerate Alabama, an economic development plan unveiled in January 2012 by the Alabama Department of Commerce, targeted the biosciences industry as an area for growth. According to BioAlabama, in 2014 Alabama had 557 biotech companies providing more than 10,000 jobs with an average salary of $56,000. The city of Birmingham is the home of 122 biotechnology companies as well as the University of Alabama at Birmingham, which includes the main campus of the School of Medicine. UAB conducted nearly 1,500 clinical trials in 2012. Huntsville, home to the world’s fourth-largest research center and the National Space and Aeronautics Administration’s (NASA) Marshall Space Flight Center, is another center of biotechnology in the state. In 1962, the city of Huntsville, with support from Brown Engineering and rocket pioneer Wernher von Braun, zoned 3,000 acres of land to serve as a research park. Cummings Research Park, with almost 3,500 acres and 285 companies— including aerospace, defense, biotechnology, software development, and information technology— is second only to the Research Triangle Park in North Carolina. HudsonAlpha, a nonprofit institute for biotechnology, anchors the 152-acre biotech campus within the park. The HudsonAlpha Institute for Biotechnology provides research space for the Genome Sequencing Center and Genomic Services Lab, as well as for tissue culture, cell culture, bioscience clean labs, and other projects. In 2012, researchers from HudsonAlpha and from Vanderbilt University identified a special population

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of intestinal stem cells that respond to damage and help prevent cancer. In 2013, the Biomedical and Life Sciences team of the CFD Research Corporation, located at the HudsonAlpha Institute for Biotechnology, received a $1 million, two-year Department of Defense contract through the Defense Health Program to fund stem cell detection and sorting research. Kapil Pant, director of biomedical technology for the company, explained that researchers will use induced pluripotent stem cells as a starting point. The hope is that noninvasively determining the differentiation state of stem cells will be a step in using stem cells for advances in treatment of burns and wounds and to increase cell growth speed to treat spinal cord injuries and neurodegenerative disorders. The T. J. Atchison Initiative and the Alabama Institute of Medicine T. J. Atchison was a 21-year-old former high school football player from Chatom, Alabama, when he sustained a complete T-7 spinal cord injury in an automobile accident. In October 2010, he became Patient A at Atlanta’s Shepherd Center, the first person with a spinal cord injury to be injected with human embryonic stem cells. In November 2011, Geron, the company that developed the stem cell therapy, stopped funding for the research, although Atchison and 14 others who received the therapy continue to be followed by doctors and researchers. The findings have been inconclusive. In 2012, the Alabama state legislature, with strong bipartisan support, passed the T. J. Atchison Initiative for Spinal Cord Injury Research and Funding, which appropriated $400,000 for UAB. The university created the T. J. Atchison Spinal Cord Injury Research Program to promote basic research on spinal cord injury and the T. J. Atchison Core Laboratories to conduct clinical research. Atchison created the T. J. Atchison Foundation to raise money to support the UAB programs. In 2013, Roman Reed, a California stem cell activist who spearheaded the passage of the Roman Reed Spinal Cord Injury Research Act, which provides up to $11 million a year in funding for spinal cord injury research in that state, and Tory Williams, a writer and Atchison family friend,

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founded the Alabama Institute of Medicine (AIM). With investors from China and Switzerland and a goal of raising $10 million in three years, AIM identified its ambitious plans: AIM grants to support scientists engaged in stem cell research, a state-of-the-art, privately funded laboratory that would not be as affected by political views as state and federally funded research, and hospital space where regenerative medicine treatments can be administered. Less than a year after its founding, AIM received a $1 million donation from an anonymous Birmingham resident. Wylene Rholetter Auburn University See Also: Adult Stem Cells: Overview; Mouse Models to Study Stem Cells; Spinal Cord Injury. Further Readings Berry, Lucy. “Huntsville’s CFDRC Developing NonInvasive Stem Cell Analyzer Technology.” AL.com. http://www.al.com/business/index.ssf/2013/07 /huntsvilles_cfdrc_wins_1_milli.html (Accessed May 2014). Christensen, John. “Passion to Find a Cure.” Shepherd Center Spinal Column (Spring 2013). http://www .shepherdcentermagazine.org/spring-2013/passionto-find-a-cure (Accessed May 2014). “Sickle Cell Gene Therapy.” Birmingham Medical News (February 15, 2012). http://www.birming hammedicalnews.com/news.php?viewStory=1637 (Accessed May 2014).

Alaska Stem cell research has drawn little attention in Alaska politics or in research within the state. Alaskans hold varying views on the topic, but the ethics of using fetal stem cells has rarely been a hotly contested issue. Since 2003, the governorship and the state legislature have been controlled by Republicans, but some Alaska Republicans appear to be more moderate on social issues, including stem cell research, than Sarah Palin’s much publicized views suggest. The record of Alaska’s congressional delegation reflects a more moderate

position. The lack of stem cell research in Alaska is more complicated than political opposition. Alaska has no stem cell research institute and no stem cell research laws. The state also lacks a full medical, dental, or veterinary college. Research in the state has focused on the physical environment and Alaska’s abundant natural resources rather than on biomedical studies. Beginning late in the 20th century, the state made a concerted effort to address the lag in biomedical research, and Alaska went from the state receiving the least amount of National Institutes of Health (NIH) funding in 2000 to receiving more than $51 million in 2011. However, funds have been distributed over a range of biomedical research projects, and, as of 2014, stem cell research has not been a priority. Moderation and Independence On paper at least, Alaska appears to be a staunchly Republican state. Alaska has not voted for a Democratic president since Lyndon B. Johnson in 1964, and until 2008 when Democrat Mark Begich became Alaska’s junior senator, the state had not sent a Democrat to Congress in almost three decades. Republicans have claimed the Governor’s Mansion since Frank Murkowski was elected in 2002. Sarah Palin, who succeeded Murkowski in 2006, went on record with her opposition to embryonic stem cell research when she was John McCain’s running mate in the Republican presidential election in 2008, despite McCain’s declared support for the research. Sean Parnell became Alaska’s 10th governor when Palin resigned in July 2009 and he was elected to a full term in 2010. Parnell is a social conservative in the mode of his predecessor; he opposes abortions even in cases of rape and incest, and he is against embryonic stem cell research. Marc Hellenthal, an Alaska-based pollster frequently employed by Republicans, describes stem cell research as not highly relevant in Alaskan campaigns, but he predicted that candidates will become more vocal on the issue since Parnell used a television ad to attack Don Young, his opponent in the 2008 contest for Alaska’s at-large congressional representative seat, for Young’s support of embryonic stem cell research. Young, the U.S. Representative for Alaska since 1973, is the senior Republican member of the House of Representatives. He has consistently



voted with his party on abortion issues but generally has broken with the party position on stem cell votes. Others among Alaska’s congressional delegation have taken similar stances. Ted Stevens, senator from Alaska for more than 40 years, voted with some inconsistency on abortion issues, but he supported embryonic stem cell research, serving as one of the 41 cosponsors of the Stem Cell Research Enhancement Act of 2007. His own experience as a survivor of prostate cancer may have contributed to this support. Mark Begich, who defeated Stevens in 2008 to become the first Democrat to represent Alaska in Congress since 1980, is a pro-choice advocate who votes with the Democratic leadership most of the time. In 2014, Begich and Republican Senator David Thune of South Dakota cosponsored a bill that required funding for embryonic stem cell research in the NIH budget be decreased by a constant amount each year for the next five years, after which time the bill will be reevaluated. The funds taken from embryonic stem cell research in the NIH will then be allocated to private adult stem cell research institutions in the form of grants from the federal government. Viewed as a compromise in that it pleased Democrats by allotting federal funds to stem cell research and pleased Republicans by shifting funds from embryonic stem cell research to adult stem cell research, the bill passed the Senate Committee of Science, Technology, and Transport by a vote of 20 to 1. Lisa Murkowski, Alaska’s senior senator, was appointed by her father, Frank Murkowski, to fill the seat he vacated when he was elected governor of Alaska. Elected to a full term in 2004, she gained national attention in 2010 when she lost the Republican primary to Tea Party candidate Joe Miller, who was endorsed by Sarah Palin. Murkowski held on to her seat by waging a battle as a write-in candidate in the general election. A member of Republicans for Choice, Murkowski has voted with her party only 61 percent of the time since her 2010 reelection. She has consistently voted for the enhancement of stem cell research and has stated her support for non– federally funded embryonic stem cell research. Focusing on Biomedical Research One month after retiring as a U.S. Army Major General in July 1998, Mark Hamilton was

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appointed the 12th president of the University of Alaska. Hamilton realized the need to improve biomedical research within the state. The University of Alaska hired new tenure-track faculty in biomedicine and related areas at the Anchorage and Fairbanks campuses, and improved undergraduate, graduate, and pre-professional programs in health and biomedicine. The new impetus coincided with the federal government’s efforts to address disparities in National Institutes of Health funding through the creation of programs such as the Institutional Development Awards (IDeA), which was designed to broaden the geographic distribution of NIH funding for biomedical and behavioral research, and the IDeA Network of Biomedical Research Excellence (INBRE), which provided grants to encourage collaborative research with undergraduate institutions, community colleges, and tribal colleges and universities in order to increase the biomedical research capacity within states. In 2004, Alaska received a $17.5 million award for the Alaska INBRE program, the largest NIH award received by the university in its nearly 100 years. Another $1.75 million grant continued funding for the Center for Alaska Native Health Research. The total NIH commitment to fund biomedical research at the University of Alaska was then more than $45 million. By 2013, the university reached more than $90 million in federal grants. That impressive achievement is for all biomedical research. The percentage, if any, that funded stem cell research, adult or embryonic, is unavailable. However, in May 2014, at the Alaska Republican Party biannual convention, moderates, in an effort to avoid a coup such as that waged by Tea Party activists in 2012, adopted rules that require a person to be a registered Republican for at least four years before seeking a top party leadership position. They also require all candidates for the party’s statewide offices to be approved by a special committee. Then they changed the party platform. One of the changes was the elimination of the opposition to embryonic stem cell research. Wylene Rholetter Auburn University See Also: Congress: Votes and Amendments; Fetal Stem Cells; University of British Columbia.

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Further Readings “Alaska Institutional Development Award Biomedical Excellence: Alaska INBRE.” Alaska INBRE. http://www.alaska.edu/inbre/about-alaska-inbre (Accessed May 2014). Gutierrez, Alexandra. “Alaska GOP Aims to Block Party Coups.” Alaska Public Media (May 4, 2014). http://www.alaskapublic.org/2014/05/04/alaska -gop-aims-to-block-party-coups (Accessed May 2014). Solo, Pam and Gail Pressberg. The Promise and Politics of Stem Cell Research. Westport, CT: Praeger, 2007.

Albert Einstein College of Medicine The Albert Einstein College of Medicine (Einstein) of Yeshiva University is a premier, researchintensive medical school, located at the Jack and Pearl Resnick Campus in the Morris Park neighborhood of the Bronx, New York City. Einstein also offers graduate biomedical degrees through the Sue Golding Graduate Division and is home to more than 2,000 full-time faculty members located at its Jack and Pearl Resnick Campus and its clinical affiliates. Einstein is committed to pursuing innovative biomedical investigation and to the development of ethical and compassionate physicians and scientists. Einstein has long been a national leader in biomedical research support from the federal government. In 2013, Einstein faculty received more than $155 million in funding from the National Institutes of Health (NIH). Additionally, the NIH funds major research centers at Einstein in stem cells, diabetes, cancer, liver disease, and acquired immunodeficiency syndrome (AIDS). Other areas of focus include developmental brain research, neuroscience, cardiac disease, and initiatives to reduce and eliminate ethnic and racial health disparities. Einstein is also the only New York City institution selected to participate in the federal government’s landmark Women’s Health Initiative, and is currently one of only four sites nationwide taking part

in a large-scale study of the health status of the Hispanic/Latino community in the Bronx, also supported by the NIH. Einstein’s partnership with Montefiore Medical Center, its University Hospital and academic medical center, includes four jointly run Centers of Excellence and is further strengthened by the dual appointments of faculty and physicians across both institutions—enhancing collaborative research, teaching, and patient care. This partnership allows for an increasing focus on bench-tobedside research, through which discoveries in Einstein’s laboratories lead to therapies and treatments for patients on an accelerated timetable. Through its affiliations with Montefiore; Jacobi Medical Center, its founding hospital; and five other hospital systems in the Bronx, Manhattan, Long Island, and Brooklyn, the College of Medicine runs one of the largest residency and fellowship training programs in the medical and dental professions in the United States. In addition to Montefiore and Jacobi, Einstein medical students rotate through clinical clerkships at BronxLebanon Hospital and St. Barnabas Hospital in the Bronx, Lennox Hill Hospital in Manhattan, North Shore–LIJ Health System on Long Island, and Maimonides Medical Center in Brooklyn. The broad geographical reach of Einstein’s residency programs is unique among New York City medical schools. Einstein also offers one of the nation’s largest programs for medical, graduate, and postdoctoral education. During the 2013 to 2014 academic year, the College of Medicine was home to 734 MD students, 236 PhD students, 106 students in the combined MD/PhD program, and 353 postdoctoral research fellows at the Belfer Institute for Advanced Biomedical Studies. The more than 8,000 Einstein alumni are among the nation’s foremost clinicians, biomedical scientists, and medical educators. The medical school opened its doors in 1955, and Einstein was one of the first major medical schools to integrate bedside experience into early medical education, bringing first-year students in contact with patients and linking classroom study to case experience. Einstein also led the way in the development of bioethics as an accepted academic discipline in medical school curricula, was the first private medical school in New York City to establish an



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Combination of two brain diagrams in one for comparison: in the left, normal brain, in the right, brain of a person with Alzheimer’s disease. In the Alzheimer’s brain the cortex shrivels up, damaging areas involved in thinking, planning, and remembering. Shrinkage is severe in the hippocampus, an area of the cortex that plays a key role in the formation of new memories. Ventricles (fluid-filled spaces within the brain) grow larger. The Albert Einstein College of Medicine receives national funding for brain research. (Wikimedia Commons)

academic department of family medicine, and was the first to create a residency program in internal medicine with an emphasis on women’s health. Einstein has embarked on a major expansion program that effectively has doubled the size of its campus. Central to this expansion, and a critical part of Einstein’s campus master plan, was the June 2008 opening of the Michael F. Price Center for Genetic and Translational Medicine/Harold and Muriel Block Research Pavilion, a 223,000 squarefoot biomedical research building that houses 40 laboratories. These new state-of-the-art facilities bring together world-class scientists and advanced, cutting-edge technology to facilitate the “translation” of discoveries at the molecular level to the actual treatment, cure, and prevention of disease. The College of Medicine has recently fostered a strong and growing team of stem cell investigators with particular expertise in hematopoietic, cancer and liver stem cell biology, and liver transplantation. In 2007, Einstein’s strategic research plan called for the creation of an institute that would bring Einstein to the forefront of stem cell and regenerative medicine research. In the subsequent five years, Einstein established the Ruth L. and David S. Gottesman Institute for Stem Cell Biology and Regenerative Medicine, following a large

philanthropic gift from the Gottesman family to provide individual investigators and multidisciplinary teams with the resources needed to realize the promise of this emerging field. The institute is led by its director and chair, Paul S. Frenette, MD—a leading stem cell and vascular biology researcher­—and is recognized for a number of significant research contributions pertaining to bone marrow biology, liver-directed therapies, neuronal stem cells in the brain, techniques for generating blood cells, and stem cell–based treatments for diabetes. The institute draws on the work of more than 25 Einstein faculty members whose research encompasses six themes: embryonic stem cell differentiation and modeling; hematopoietic and cancer stem cells; neuroscience; model organisms of stem cell biology; cardiovascular progenitors; and liver regeneration. The institute’s mission is (1) to advance the scientific knowledge in stem cell biology and breakthroughs in regenerative medicine through faculty interactions, research support, and education; (2) to foster collaborations and innovations by bridging scientific fields and overcome natural departmental barriers; (3) to translate basic science discoveries into novel stem cell–based therapies that impact clinical care.

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The Stem Cell Institute is housed on the first floor of the Price Center and in renovated space across four other research buildings, with the goal of establishing an institute that would set the standard in stem cell research and regenerative medicine, nationally and internationally. In addition to its generous endowment, the Institute for Stem Cell Biology and Regenerative Medicine at Einstein is supported by external sources, including the NIH and the NYSTEM. Created in 2007, NYSTEM has provided substantial funding for stem cell research over the decade since its founding. Notably, Einstein is among the highest-ranked institutions in New York competing for state support and, to date, has received more stem cell funding from NYSTEM than any other institution. Funding from NYSTEM supports the creation of the Einstein Comprehensive Pluripotent Stem Cell Center, which consists of three units: the Human Pluripotent Stem Cell Unit, the CellSorting and Xenotransplantation Unit, and the Stem Cell Genomic Unit. Stem cell research at Einstein also benefits from the College of Medicine’s long-standing commitment to research with model organisms, including C. elegans, Drosophila, zebrafish, and mice. Keisuke Ito Albert Einstein College of Medicine See Also: Adult Stem Cells: Overview; Blood Adult Stem Cell: Current Research on Isolation or Production of Therapeutic Cells; Embryonic Stem Cells, Methods to Produce. Further Readings Albert Einstein College of Medicine. http://www .aecom.yu.edu (Accessed January 2014). Eltayeb, Emil. Albert Einstein and Diseases. New York: Xlibris Corporation, 2008. Stem Cell Institute. http://www.einstein.yu.edu/ centers/stem-cell/research (Accessed January 2014).

Alvarez-Buylla, Arturo Dr. Alvarez-Buylla is one of the top experts of neurogenesis, the area of biological sciences that studies the development and population

of nervous tissue and neurons. His research focus is developmental stem cell biology, developmental neuroscience, molecular and cellular neurobiology, learning and plasticity, brain tumors, and behavior-related mechanisms. As an inventor, Alvarez-Buylla designed a variety of devices utilized for scientific research. Neurogenesis The discovery of adult neurogenesis, a term that refers to the generation of neural tissue and cells, is relatively recent. The observation that neurons continue to grow in some areas of the brain eliminated the idea that human beings are born with a fixed amount of neurons. The revelation was a paradigm shift in the biosciences and changed the course of neurobiology. Today, the discipline of adult neurogenesis is developing rapidly and has a great influence in the fields of brain development and brain-related issues such as aging, memory, learning, neuropsychiatric disorders, and brain injury and disease. Adult neurogenesis has been observed in the hippocampus, subventricular zone, olfactory bulb, and spinal cord. The hippocampus, located on both sides of the brain under the cerebral cortex, plays an important role in short- and long-term memory. The subventricular zone (SVZ) is the largest germinal niche in the adult mammalian brain. It contains numerous neural stem cells with the ability to generate new neurons and glial cells. The olfactory bulb is a neural structure located in the forebrain that functions to perceive odors. Neurogenesis was first observed in mice, followed by other vertebrate mammals such as cows, rabbits, monkeys, and, finally, humans. Although the significance of neurogenesis in humans remains unknown, it is important to study because of its potential application for therapy in neurological and neurogenerative injuries and pathologies. Alvarez-Buylla Research The Alvarez-Buylla Laboratory is located in the University of California, San Francisco Department of Neurological Surgery. The laboratory studies the mechanisms of neuron generation and migration, neural stem cells in the mammalian brain, the links between neural stem cells or their immediate progeny, and the role of stem cells in the treatment of neurogenerative disease. About two decades ago, the laboratory discovered that new neurons generated in the

Alzheimer’s Disease



SVZ reach the olfactory bulb in rodent brains, becoming completely integrated into functional circuits. This finding was influential in changing the conventional belief that young neurons could not be integrated into functioning circuits of adult brains. The Alvarez-Buylla Laboratory is also interested in researching the mechanisms of cell migration in the adult brain, as well as the ontogeny and proliferation of astrocytes functioning as stem cells in rodent and human brains. These studies include exploring how cells migrate through the complexities of the adult brain, the ways in which new neurons become integrated into already functioning neural circuits, the contributions of neurons to plasticity, and other related issues. Some of the most recent findings in the laboratory have been identifying the neural stem cells in the SVZ as a subpopulation of astrocytes, as well as the discoveries that adult neural stem cells are heterogeneous and that specific types of neurons are derived from progenitors in particular locations of the rodent SVZ. The lab also investigates the human SVZ as a potential source of stem cells to treat neurodegenerative disease. The goal of this line of research is to understand how it is organized, study and define its structures, identify the mechanisms of neuroblast migration, isolate SVZ stem cells, and determine the development of the germinal layer through several stages. The Alvarez-Buylla Laboratory also studies inhibitory interneuron progenitor cells that integrate in the postnatal cortex and increase local inhibition. Alvarez-Buylla’s current and future research includes proving that these processes can be used to treat neurodegenerative diseases in a safe manner. These results hold promise for therapies that may help patients suffering from epilepsy and Parkinson’s disease, to other types of pathologies such as mental illness. Trudy M. Mercadal Florida Atlantic University See Also: Embryonic Stem Cells, Methods to Produce; Neural: Cell Types Composing the Tissue; Neural: Current Research on Isolation or Production of Therapeutic Cells. Further Readings Gil-Perotin, Sara, Arturo Alvarez-Buylla, and Jose Manuel Garcia-Verdugo. Identification and Characterization of Neural Progenitor Cells in the

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Adult Mammalian Brain (Advances in Anatomy, Embriology and Cell Biology). New York: Springer, 2009. Kempermann, Gerd. Adult Neurogenesis. Oxford: Oxford University Press, 2011. Seki, Tatsunori, Kazunobu Sawamoto, Jack M. Parent, and Arturo Alvarez-Buylla (eds.). Neurogenesis in the Adult Brain I: Neurobiology. New York: Springer, 2011. Seki, Tatsunori, Kazunobu Sawamoto, Jack M. Parent, and Arturo Alvarez-Buylla (eds.). Neurogenesis in the Adult Brain II: Clinical Implications. New York: Springer, 2011.

Alzheimer’s Disease Alzheimer’s disease (AD) is the most common form of acquired cognitive behavioral impairment and dementia. The disease has a long progressive natural course that interferes with social and occupational functioning. To date, there are no cured cases. Hippocampal/cerebral plaques are most prominently known to impair memory encryption, thinking, and decision-making processes. It is still unclear if the plaques themselves cause the disease or are the result of an underlying pathology. The disease is named after Dr. Alois Alzheimer, a German psychiatrist who first observed short-term memory loss and anomalous behavioral changes in a 51-year-old female patient, Mrs. Auguste D., at a Frankfurt asylum in 1901. After her death in 1906, Dr. Alzheimer performed microscopic examination of brain sections that led to identification of the disease specific amyloid plaques and neurofibrillary tangles. The diagnosis of Alzheimer’s disease is mostly clinical, with only a limited number being diagnosed on brain biopsy. However, there have been reports that the specific pathological changes can exist without the concomitant clinical manifestations of the disease. Types Early onset (12 months) was significant, whereas there was no discernible effect on short-term mortality (50,000/uL

Minimal

20,000–50,000/uL

Minor bleeding after trauma