An in vitro study of hair and vibrissae development in embryonic mouse skin.

The development of specialized epithelial derivatives in mammalian skin such as hair and vibrissae has not been subjected to detailed experimental analysis. Chase (1) and Rawles (2) suggested that the development of hair and of vibrissae involved an inductive interaction between the epidermis and dermis of developing skin. This suggestion was based mainly on certain similarities between the deVelopmental anatomy of hair and vibrissae, and that of feathers. In feather development the role of inductive interactions between condensations of dermal cells and the overlying epidermis has been well substantiated by a number of experimental studies (3—5). Also, in post-embryonic development feather formation depends on the dermal papilla, since regeneration of feathers does not occur in its absence (6). Similar condensations of dcrmal cells associated with the epidermis have been described in mammalian skin during the development of pelagc and vibrissal hair, in vivo and in vitro. Furthermore, the presence of a dermal component in pelage and vibrissal hairs is considered necessary for the maintenance and regeneration of these structures in the adult mammal (7, 8). These anatomical analogies between feathers and hair suggested that the basic mechanisms involved in hair development might also be dependent on cpidcrmal-dcrmal interactions. However, this assumption has not been experimentally tested or supported by unequivocal evidence (9). Some of the complications in earlier studies on this problem may have stemmed from technical difficulties of isolating and transplanting cleanly separated components of skin and hair follicles. In addition, in most previous studies on hair development adult tissues were used; such material may have attained a developmental state that would preclude expression of morphogenetie capabilities other than