Integrins in the wounded and unwounded stratified squamous epithelium of the cornea.

PURPOSE The authors determined the synthesis, cell surface expression, and localization of integrins in the rat corneal epithelium to detect whether any changes in integrins occur during epithelial migration in response to simple debridement wounding. METHODS Immunoprecipitation analysis of extracts from either metabolically or surface-labeled rat epithelia was done to assess the synthesis and cell surface expression of integrins in the normal cornea. The localization of integrins was determined by indirect immunofluorescence of frozen sections obtained from control corneas and from those after debridement wounding. Immunoblotting of extracts from time course experiments was done on organ cultures of rat corneas after debridement to determine if any changes in the amounts of integrins occurred. The cell adhesion function of integrins on control and migrating epithelial cells was evaluated by cell adhesion assays. RESULTS The data indicated that the corneal epithelium has a variety of distinct integrin subunits including beta 1, beta 4, beta 5, alpha 2, alpha 3, alpha 5, alpha 6, and alpha v. Although beta 1, beta 5, alpha 2, alpha 3, and alpha v were localized to sites of apparent cell-cell contact, alpha 5, alpha 6, and beta 4 were localized specifically to the basal membrane of the basal cells. Little change occurred in the localization of integrins in the migrating epithelial sheets. At 3, 6, 9, 12, 18, and 24 hr after wounding, the amount of the beta 1, beta 4, alpha 3, alpha 5, and alpha 6 integrin subunits (as measured by immunoblots) was not altered relative to that of the control corneas. Adhesion assays also showed no differences in adhesion of stationary versus migrating corneal epithelial cells to fibronectin and laminin. CONCLUSIONS Integrin localization, production, and cell adhesion function in the stratified squamous epithelium of the cornea are not dramatically altered during epithelial cell migration over simple debridement wounds. Integrins in the cell membrane at sites of cell-cell interaction and as components of the hemidesmosomes in stationary epithelia may be available for rapid recruitment as epithelial cell migration proceeds.