A chimeric epidermal growth factor with fibrin affinity promotes repair of injured keratinocyte sheets

The aim of the present study is to create a novel chimeric protein of epidermal growth factor (EGF) with fibrin affinity and demonstrate its potential for repairing injured tissues by immobilization to fibrin. The chimeric protein (FBD-EGF) was produced by the fusion of the fibronectin fibrin-binding domain (FBD) to EGF. It showed dose-dependent binding to fibrin and its binding was stable for at least 7days, while native EGF showed little affinity. FBD-EGF promoted the growth of fibroblasts and keratinocytes in the fibrin-bound state as well as in the soluble state. Its activity was further studied in a keratinocyte culture system in which fibrin was exposed upon injury of cell sheets. Fibrin-bound FBD-EGF promoted growth of the sheets over the injured area at a significantly faster rate (approximately eightfold) than native EGF (p<0.01). Wounds 2mm wide were closed in 7-9days. This repair process was inhibited by anti-EGF. Keratinocytes proliferated more extensively in the leading edges of sheets contacting fibrin with FBD-EGF, approximately 1.7-fold more than in the adjacent regions. These results imply that the stable binding of chimeric EGF to fibrin is effective for the repair of injured keratinocyte sheets, suggesting a potential use in tissue engineering.