Stem Cells

stem cell terminology

Stem cells refer to the category of cells within an organism that are able to self-renew as well as differentiate into more specific cell fates. There are 2 major classes of naturally occurring stem cells in vertebrate animals: embryonic and adult. Another category of stem cells are derrived from differentiated tissues that are then induced to become "stem cell-like;" these are referred to as induced pluripotent stem cells (iPS cells).1

Common terminology within the field refers to the "potency" of the stem cell.

• Totipotency implies that a cell is capable of generating an entire organism. (ex. a fertilized egg)
• Pluripotancy implies that a cell is capable of differentiating into a cell belonging to any of the three major germ/tissue layers (ectoderm, mesoderm, endoderm ), but is not capable of generating an entire organism. (ex. embryonic stem cells)
• Multipotency implies that a cell is capable of differentiating into a variety of more specific cell types, however it is usually restrictd to only one or two of the germ layers. (ex. most adult stem cells).

references

1. Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell. 2006 Aug 25;126(4):663-76. Epub 2006 Aug 10. PMID: 16904174 [PubMed - indexed for MEDLINE]