Involvement of integrins with adhesion-promoting, heparin-binding peptides of type IV collagen in cultured human corneal epithelial cells

Purpose. The aim of this work was to identify the integrin subunits present on the cell surface of human corneal epithelial cells. The authors determined to show whether type IV collagen. heparin-binding peptides of type IV collagen (Hep-I, Hep-II, and Hep-III), fibronectin, and GRGDSP promote cell adhesion of human corneal epithelial cells. Type IV collagen and heparin-binding peptides of type IV collagen may be important in corneal epithelial cell adhesion in normal and pathologic conditions and reepithelialization. The authors assess the role of cell surface integrins in mediating cell adhesion to these proteins and peptides. Methods. Fluorescence-activated cell sorter (FACS) analysis was used to determine the integrin subunits expressed at the cell surface of the cultured human corneal epithelial cells. Cell adhesion was assessed with type IV collagen, heparin- binding peptides of type IV collagen, fibronectin, and GRGDSP. Antibodies to the integrin subunits were used to determine the potential role of integrins in cell adhesion to the above proteins and peptides. Results. FAGS analysis identified the β1, β4, α2, α3, α5, α6, and αv integrin subunits on human corneal epithelial cells grown as primary cultures. The anti-β1 antibody inhibited cell adhesion to heparin-binding peptides of type IV collagen, type IV collagen, fibronectin, and GRGDSP. Antibodies to the α2 integrin subunit inhibited cell adhesion to the heparin-binding peptides of type IV collagen and slightly inhibited cell adhesion to intact type IV. Antibodies to the α3 integrin subunit exhibited a somewhat lesser effect compared to the anti-α2 integrin antibody. Conclusions. These data show that the α2β1 integrin of human corneal epithelial cells recognize heparin- binding peptide sequences derived from human type IV collagen. It seems likely that these sequences play an important role in integrin-mediated corneal epithelial cell adhesion. In addition, the α3β integrin may mediate similar events.