Concise review: culture mediated changes in fate and/or potency of stem cells.

Although Gurdon demonstrated already in 1958 that the nucleus of intestinal epithelial cells could be reprogrammed to give rise to adult frogs, the field of cellular reprogramming has only recently come of age with the description by Takahashi and Yamanaka in 2006, which defined transcription factors can reprogram fibroblasts to an embryonic stem cell-like fate. With the mounting interest in the use of human pluripotent stem cells and culture-expanded somatic stem/progenitor cells, such as mesenchymal stem cells, increasing attention has been given to the effect of changes in the in vitro microenvironment on the fate of stem cells. These studies have demonstrated that changes in culture conditions may change the potency of pluripotent stem cells or reprogram adult stem/progenitor cells to endow them with a broader differentiation potential. The mechanisms underlying these fate and potency changes by ex vivo culture should be further investigated and considered when designing clinical therapies with stem/progenitor cells.