The expression of integrin subunits alpha 6 and beta 4 by corneal epithelial cells on modified hydrogel surfaces

Our goal was to quantitate the expression and localization of integrin subunits alpha 6 and beta 4 by corneal epithelial cells on defined synthetic substrates. Previously we demonstrated that the cytoplasmic pH and translocation of the alpha 6 integrin subunit to the cell membrane was modified by ionic interactions. These results suggest that changes in the ionic interactions at the cell-substrate interface not only alter the intracellular milieu but ultimately affect the expression of adhesion proteins. To test this hypothesis, hydroxyethylmethacrylate (hema) hydrogels were modified by the addition of amines (N,N-dimethylaminoethylmethacrylate) or carboxyl moieties (methacrylic acid). Changes in the distribution of mRNA and protein were monitored using confocal laser scanning microscopy. The steady state level of integrin mRNA was evaluated, and the results indicate that while the plating efficiency was identical on all surfaces, the expression and localization of integrin subunits was surface dependent. Alpha 6 and beta 4 proteins were localized along the basal surface of nonpermeabilized cells cultured on laminin, on surfaces with amine moieties, and on those with amine and carboxyl moieties. The level of diffuse cytoplasmic staining increased with the presence of carboxyl moieties. Alpha 6 and beta 4 integrin subunits were negligible when the surfaces contained carboxyl moieties alone. The expression of alpha 6 and beta 4 mRNA was higher on surfaces containing amine moieties than on surfaces containing only carboxyl moieties. These results indicate that the characteristics of the substrate and the resulting cell-matrix interaction alter protein and mRNA expression of integrin subunits.