Mutually exclusive expression of connexins and α-enolase in the rat limbo-cornkal epithelium during development and in the adult

Purpose. Cell-cell ionic and metabolic cooperation are critical for corneal epithelial (CT) functions, including wound healing (Matic et al. lOVS, 1997, in press) and differentiation (Matic et al. Differentiation. 1997. in press). CE gap junctions arc made of either connexm 50 (Cx50) or connexin43 (Cx43). This study sought (o characterize the expression of these connexins during early rat post natal stages in relationship to u-enolase, a preestahlished stem cell marker {IOVS. 22, 132, and 1OVS. 13. 2199). Methods. Neonatal and adult whole rat eyes were cryosectioned and immunostained for a-enolase. Cx43 and Cx50. Results. In the adult, a-enolase is circumscribed to the limbal epithelium (LE) which contains the stem and early precursor cells of the CE. Conversely, the connexins. which are present throughout the basal (Cx43) or ail of the layers (Cx50) of the CE. are excluded from the LE. Ai birlh u-enolase is present in all CE cells, from limbus to limbus whereas Cx50 is present in lev, isolated cells at the CE center. Cx43 is not detectable. "I'hrough day(si 3-10, CE a-enolase levels decrease gradually, while the number of Cx50 positive CE cells increases. After-wards, concurrent with epithelial stratification. α-enolasc disappears from the CE and Cx50 undergoes a dramatic increase, so that by day 17 the distribution of these two components is indistinguishible from that of the adult. {C\43. though, remains barely identifiable.) Conclusions. The Cx50 and α-enolasc distributions are mutually exclusive throughout CE development and in the jdult. It is proposed that the expression of the glycolytic enzyme is inhibited b> the establishment of metabolic cell-cell cooperation secondary to Cx50 expression.