Activation of human keratinocyte fibronectin receptor function in relation to other ligand-receptor interactions

Previous studies have shown that the fibronectin receptor function of keratinocytes is activated during wound healing in vivo and during cell culture in vitro. In order to study the specificity of activation in culture, two series of experiments were carried out. First, freshly isolated human keratinocytes were tested in short-term assays to determine their adhesion to several different ligand-coated substrata including fibronectin, collagen, basement membrane, concanavalin A, and wheat germ agglutinin. Second, human keratinocytes were cultured on the above substrata, and after various times, the cultured cells were harvested and retested for adhesion. We found that, compared with freshly isolated cells, cultured keratinocytes were activated more than 30-fold in their attachment to fibronectin-coated substrata but unchanged in their attachment to other ligand-coated substrata. In addition, cultured keratinocytes were activated in their capacity to spread on all ligand-coated substrata. The cells that expressed enhanced adhesiveness were found to be mostly basal keratinocytes, based on immunofluorescence staining studies. Also, basal keratinocytes attached selectively on substrata coated with fibronectin, collagen, or HR-9 basement membrane, but not on substrata coated with lectins. We propose that the activation of keratinocyte adhesiveness is a novel feature of basal keratinocytes required for reepithelialization during wound repair.