LOCALIZATION OF INTEGRIN AND SYNDECAN INVIVO IN A CORNEAL EPITHELIAL ABRASION AND KERATECTOMY

We compared the localization of integrin, a glycoprotein adhesion receptor, and syndecan, a transmembrane proteoglycan receptor, in vivo during the process of corneal epithelial wound healing to determine if the contact between migrating epithelium and substrata influence the expression of these two adhesion proteins. The expression of three integrin subunits of the alpha/beta heterodimer complex, beta-1, alpha-5, and alpha-6, were examined over a 48 hr in response to an abrasion. We also examined their expression in a keratectomy and compared their two conditions. The beta-1 subunit, which is expressed basolaterally in a normal cornea, was localized during epithelial migration over the basal lamina and keratectomy. Negligible levels of the fibronectin binding receptor subunit, alpha-5, were detected in a normal cornea. The levels of staining between a normal cornea, an abrasion and a keratectomy did not differ. Detection of alpha-6, the laminin binding receptor subunit, was expressed most intensely along the basal side of basal cells in a normal cornea. During the course of wound healing, alpha-6 was only detected in the basal cells and by two days the localization resembled that seen in the normal. cornea. Epithelial staining for the alpha-6 subunit was also detected during the migration of cells over the keratectomy, more intensely than the other two subunits. Syndecan, which acts as a more permanent adhesion receptor in stratified epithelium, was only detected 48 hr post-abrasion, throughout all layers of epithelium, as was expected. These results indicate a predominance of alpha-6 expression by corneal epithelial cells at all times of in vivo wound healing and the presence of syndecan only upon restratification of the epithelium.