DISTRIBUTION OF ALPHA(6) AND BETA(4) INTEGRINS FOLLOWING EPITHELIAL ABRASION IN THE RABBIT CORNEA

Integrin complex alpha(6) beta(4) is a component of the hemidesmosome. In the unwounded cornea both the integrin subunits face the laminin-c ontaining basement membrane, but the alpha(6) subunit is also located between the basal cells. While the migrating epithelium is known to be without hemidesmosomes, we investigated the distribution of alpha(6) beta(4) during epithelial healing. Epithelial abrasion 7.5 mm in diame ter was mechanically created. The rabbits were killed 1-24 h or 2, 3, or 7 days later. Monoclonal antibodies against alpha(6), beta(4), and laminin A were used to detect their distributions by immunohistochemis try. Positive immunostaining for laminin A on the surface of the unepi thelialized stroma indicated that basement membrane was intact after t he epithelial abrasion. Three hours after corneal wounding, alpha(6) w as detectable around the entire cell up to the leading edge of the mig rating epithelium. In the peripheral wound, alpha(6) was also prominen tly present around the basal and suprabasal cells,vith only the superf icial cell layers being negative. The beta(4) subunit showed a dissimi lar distribution; it was not detectable subjacent to the leading edge. After 1 h the immunoreaction for the beta(4) subunit had faded 15-20 mu m peripheral to the,wound margin. Thereafter the subepithelial band was segmentally reassembled, starting from the periphery and progress ing toward the central area of the wound. One,week after epithelial wo unding, immunolabeling for both integrin subunits was indistinguishabl e from that of the control cornea. Our results indicate that in additi on to the beta(4) in the rabbit cornea, the alpha(6) subunit is also c omplexed with another beta subunit during the epithelial healing phase . The results also suggest that basal cells 15-20 mu m peripheral to t he wound margin disassemble their HDs prior to the migration process.