Transdifferentiation of corneal epithelium: evidence for a linkage between the segregation of epidermal stem cells and the induction of hair follicles during embryogenesis.

The study demonstrated that corneal epithelium could transdifferentiate into hair-bearing epidermis, suggesting that transient amplifying (TA) cells could activate different genetic programs in response to changes in their fibroblast environment. Tissue recombination experiments showed that adult central corneal cells responded to embryonic dermis signals by decreasing K12 keratin expression, increasing K5 expression, proliferating, and forming hair follicles. This process involved reprogramming corneal TA cells to form epidermal cells, transitioning from a basal epithelial-type to hair pegs and potentially hair stem cells. The findings highlighted the hair's role as a primary reservoir of epidermal stem cells and raised questions about the dermal messages involved in hair induction and stem cell specification.