Stem cells: shibboleths of development, part II: Toward a functional definition.
Our previous discourse on stem cell characteristics led to the conclusion that the qualities deemed essential for a cell to be considered a "stem cell" are neither firmly established nor universally accepted, and this we accept as editorial policy. In that study, self-renewal, asymmetric division, phenotypic markers, and other attributes touted as being indicative of cells being stem cells were critically questioned as fundamental to the definition of a stem cell, leading us to seek a functional definition instead. Here, we offer further considerations, and elaborate on the characteristics that diverse investigators feel are essential for a cell to function as a stem cell, either in development or body maintenance. We hope that this discourse will promote further reflection, culminating with a definition that is widely accepted and universally applicable. We confess this goal has not been reached, neither here nor elsewhere. The outstanding goal of understanding what stem cells are, a prerequisite of characterizing what stem cells do and how they do it, is still outstanding.
Parker
Graham C
GC
Children's Research Center of Michigan, the Carman and Ann Adams Department of Pediatrics, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Anastassova-Kristeva
Marlene
M
Eisenberg
Leonard M
LM
Rao
Mahendra S
MS
Williams
Marc A
MA
Sanberg
Paul R
PR
English
Denis
D
D000818:Animals; D002454:Cell Differentiation; D006801:Humans; D013234:Stem Cells / Q000145:classification / Q000166:cytology / Q000502:physiology