Growth factor-induced epidermal invasion of the dermis in human skin organ culture: expression and role of matrix metalloproteinases.

Matrix metalloproteinase activity was assessed in culture fluids of organ-cultured human skin by gelatin zymography. Both the 92-kD gelatinase/type IV collagenase and the 72-kD gelatinase/type IV collagenase were detected. Production of the 92-kD enzyme was substantially increased in the presence of epidermal growth factor (EGF) and hepatocyte growth factor (HGF) as compared to control but not in the presence of insulin-like growth factor-1 (IGF-1) or keratinocyte growth factor (KGF). This is of interest because our recent studies have shown that EGF and HGF induce the epithelial cells to invade the underlying stroma while normal architecture is maintained in the presence of IGF-1 and KGF. Addition of tissue inhibitor of metalloproteinase-2 to the organ culture fluids blocked expression of the active forms of both enzymes and concomitantly blocked invasion. Epidermal keratinocytes, dermal fibroblasts and dermal endothelial cells were grown in monolayer culture and examined for matrix metalloproteinase production. The 92-kD enzyme accounted for most of the gelatinase activity in keratinocyte culture fluids while the 72-kD enzyme accounted for most of the activity in the dermal fibroblast and endothelial cell culture fluids. Increased production of the 92-kD enzyme was seen in keratinocytes upon exposure to the growth factors that induced invasion (EGF and HGF) while the two factors that did not induce invasion (IGF-1 and KGF) were much less effective. Production of the 72-kD enzyme in fibroblasts and endothelial cells was not upregulated by any of the four growth factors. Taken together, these data indicate that matrix metalloproteinase activity is increased in the epithelium under the influence of invasion-inducing growth factors and contributes to invasion.