Epidermal growth factor (EGF) promotes human keratinocyte locomotion on collagen by increasing the alpha 2 integrin subunit

Abstract

The migration of human keratinocytes across the would bed is an early and critical event in the reepithelialization of cutaneous wounds. Epidermal growth factor (EGF) has been shown to accelerate the healing of fresh, split-thickness cutaneous wounds when applied topically. The mechanism(s) by which this accelerated healing occurs remains unknown. Using an assay that directly evaluates human keratinocyte locomotion without confounding the possibility of cell proliferation, we examined the influence of EGF on human keratinocyte motility. Both recombinant epidermal growth factor (rEGF) and transforming growth factor-alpha (TGF-alpha) promoted human keratinocyte locomotion when the cells were apposed to connective tissue matrices of collagen or fibronectin, important components of the wound bed. Other growth factors studied did not enhance keratinocyte migration. Blocking the EGF/TGF-alpha receptor on the cell surface of keratinocytes with specific antibody inhibited the stimulation of keratinocyte locomotion by rEGF and TGF-alpha. Flow cytometry analysis of keratinocytes migrating on type I collagen in the presence of rEGF or TGF-alpha revealed increased expression of the alpha 2 integrin subunit on the keratinocyte surface. The alpha 2 beta 1 integrin mediates keratinocyte migration on collagens type I and IV, and inhibition of migration via antibody blockade of the alpha 2 beta 1 integrin can be partially overcome by increasing the concentration of rEGF present in the medium. Our study demonstrates that the growth-independent stimulation of keratinocyte locomotion via regulation of integrin expression may be one mechanism by which EGF accelerates the reepithelialization of human cutaneous wounds.