Metaplastic induction of scales and feathers in the corneal anterior epithelium of the chick embryo

Abstract

The anterior epithelium of the embryonic chick cornea has differentiated by the fourth day of incubation, and has been engaged in the deposition of a subepithelial collagenous stroma for 24 hours or longer. To test whether the corneal epithelium can be induced to participate in the formation of other ectodermal derivatives at this early stage in its differentiation, we confronted it with mesenchyme taken from feather, scale, or hair-forming regions. The lenses of 5-day chick embryos were replaced with blocks of mesenchyme derived from suitable locations in donor animals of appropriate species and age and the host eyes were examined histologically at intervals ranging up to 12 days after surgery. Dermis from the scale-forming foot region of 13-day-old donor chick embryos promoted scale formation in the anterior epithelium of most of the hosts; in some cases feathers were associated with the scales. Prospective dermis from the periotocystal feather-forming area of 5-day-old chick embryos elicited the formation of feathers in the corneal anterior epithelium of most of the hosts. Dermis from the flanks of mouse embryos at 13.5–14.5 days of gestation also produced feather formation in host corneas. The anterior epithelium of the cornea of the 5-day-old chick embryo is one of the few metazoan tissues in which a change from one relatively advanced state of differentiation to another has been induced.