TRANSDIFFERENTIATION OF EMBRYONIC AND POSTNATAL RABBIT CORNEAL EPITHELIAL-CELLS

In order to study the determination of corneal epithelial cells, rabbi t corneal epithelium of 12- to 24-day embryos, newborn and 12-day-old offspring were recombined with mouse embryo upper-lip or dorsal dermis . Epithelial differentiation was analyzed using immunohistology with c orneal monospecific monoclonal antibody AK12 (anti-keratin K12). Recom binants involving 12-day embryo undifferentiated corneal ectoderm form ed a typical epidermis with hair follicles after 10 days of culture on the chick chorioallantoic membrane. Central corneal epithelium from 2 3- to 24-day embryos and newborn, which express suprabasally both K3 a nd K12 keratins and basally the K12 keratin alone, when grown in assoc iation with trichogenic dermis first failed to produce K12 in its new forming basal layer and then stratified after 11 days of culture above a differentiating epidermis with hair buds. When the culture period w as increased up to 21 days by grafting under the kidney capsule from a thymic mice, even the central corneal epithelium of 12-day-old offspri ng gave rise to a complete epidermis with emerging hairs. The vibrissa l- or pelage-type of hairs was in conformity with the regional origin of the mouse dermis. The species origin of the epithelial cells of the recombinants was discriminated incontestably using the Hoechst staini ng of interphase nuclei. Thus, the rabbit corneal epithelial cells can transdifferentiate into epidermal keratinocytes and trichocytes at le ast until 12 days after birth, despite the fact that from the fifth po stnatal day the cells of its basal layer express both the K3 and the K 12 keratins, a keratin pair marker of corneal cell-type terminal diffe rentiation.