Adult reserve stem cells and their potential for tissue engineering.
Tissue restoration is the process whereby multiple damaged cell types are replaced to restore the histoarchitecture and function to the tissue. Several theories have been proposed to explain the phenomenon of tissue restoration in amphibians and in animals belonging to higher orders. These theories include dedifferentiation of damaged tissues, transdifferentiation of lineage-committed progenitor cells, and activation of reserve precursor cells. Studies by Young et al. and others demonstrated that connective tissue compartments throughout postnatal individuals contain reserve precursor cells. Subsequent repetitive single cell-cloning and cell-sorting studies revealed that these reserve precursor cells consisted of multiple populations of cells, including tissue-specific progenitor cells, germ-layer lineage stem cells, and pluripotent stem cells. Tissue-specific progenitor cells display various capacities for differentiation, ranging from unipotency (forming a single cell type) to multipotency (forming multiple cell types). However, all progenitor cells demonstrate a finite life span of 50 to 70 population doublings before programmed cell senescence and cell death occurs. Germ-layer lineage stem cells can form a wider range of cell types than a progenitor cell. An individual germ-layer lineage stem cell can form all cells types within its respective germ-layer lineage (i.e., ectoderm, mesoderm, or endoderm). Pluripotent stem cells can form a wider range of cell types than a single germ-layer lineage stem cell. A single pluripotent stem cell can form cells belonging to all three germ layer lineages. Both germ-layer lineage stem cells and pluripotent stem cells exhibit extended capabilities for self-renewal, far surpassing the limited life span of progenitor cells (50-70 population doublings). The authors propose that the activation of quiescent tissue-specific progenitor cells, germ-layer lineage stem cells, and/or pluripotent stem cells may be a potential explanation, along with dedifferentiation and transdifferentiation, for the process of tissue restoration. Several model systems are currently being investigated to determine the possibilities of using these adult quiescent reserve precursor cells for tissue engineering.
Division of Basic Medical Sciences, Mercer University School of Medicine, Macon, GA, USA. young_he@mercer.edu
Henry E
HE
Young
Cecile
C
Duplaa
Marina
M
Romero-Ramos
Marie-Francoise
MF
Chesselet
Patrick
P
Vourc'h
Michael J
MJ
Yost
Kurt
K
Ericson
Louis
L
Terracio
Takayuki
T
Asahara
Haruchika
H
Masuda
Sayaka
S
Tamura-Ninomiya
Kristina
K
Detmer
Robert A
RA
Bray
Timothy A
TA
Steele
Douglas
D
Hixson
Mohammad
M
el-Kalay
Brian W
BW
Tobin
Roy D
RD
Russ
Michael N
MN
Horst
Julie A
JA
Floyd
Nicholas L
NL
Henson
Kristina C
KC
Hawkins
Jaime
J
Groom
Amar
A
Parikh
Lisa
L
Blake
Laura J
LJ
Bland
Angela J
AJ
Thompson
Amy
A
Kirincich
Catherine
C
Moreau
John
J
Hudson
Frank P
FP
Bowyer
T J
TJ
Lin
Asa C
AC
Black
D000818:Animals; D000954:Antigens, Surface / Q000378:metabolism; D001842:Bone and Bones / Q000378:metabolism; D002417:Cattle; D002454:Cell Differentiation / Q000502:physiology*; D019070:Cell Lineage / Q000502:physiology; D016922:Cellular Senescence / Q000502:physiology; D003238:Connective Tissue / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D003920:Diabetes Mellitus / Q000628:therapy; D004622:Embryo, Mammalian; D004625:Embryo, Nonmammalian; D005121:Extremities / Q000502:physiology; D015316:Genetic Therapy; D005855:Germ Layers / Q000166:cytology*; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D018482:Muscle, Skeletal / Q000378:metabolism / Q000637:transplantation; D009203:Myocardial Infarction / Q000628:therapy; D018008:Myogenin / Q000378:metabolism; D019636:Neurodegenerative Diseases / Q000628:therapy; D050814:Octamer Transcription Factor-3; D039904:Pluripotent Stem Cells / Q000166:cytology* / Q000637:transplantation; D051381:Rats; D012038:Regeneration / Q000502:physiology*; D019098:Telomerase / Q000378:metabolism; D023822:Tissue Engineering; D014157:Transcription Factors; D014562:Caudata / Q000254:growth & development / Q000502:physiology
D000954:Antigens, Surface; D004268:DNA-Binding Proteins; C503799:MYOG protein, human; C503803:Myog protein, rat; D018008:Myogenin; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D014157:Transcription Factors; D019098:Telomerase