ABSTRACT
Post-natal keratinocytes, ocular limbal cells and chondrocytes have been successfully used therapeutically, somatic stem cells of other tissues frequently cannot be grown in culture. For this reason many debilitating diseases that could conceivably benefit from cell-based therapy are not currently treatable. The prevalent idea that somatic cell types obtained from the differentiation of hES cells and proposed for human therapy are identical to the corresponding post-natal somatic cells formed by the normal process of embryogenesis is not well founded. Differentiation of hES cells in culture takes place in the absence of developmental cues such as are afforded by polarity and gradients and the differentiation takes place much more rapidly than that which occurs during embryogenesis. There are two ways of obtaining keratinocytes from hES cells. One is to form embryoid bodies in vitro, allow them to undergo differentiation and harvest the resulting keratinocytes.
