Dose-dependent effects of epidermal growth factor on corneal wound healing

The dose-dependent effect of epidermal growth factor (EGF) on the development of wound tensile strength following full-thickness corneal wounds was evaluated in 60 adult rabbits. One eye from each rabbit received a single 7-mm long corneal incision. After injury each rabbit was treated three times daily for 5 or 10 days with either EGF at 0.001 mg/ml (10 eyes), 0.01 mg/ml (10 eyes), 0.1 mg/ml (10 eyes), 1.0 mg/ml (15 eyes), or vehicle (15 eyes). The tensile strength of the wound was evaluated using a 5-mm wide strip of cornea mounted on a tensiometer. We found that EGF at 0.1 mg/ml and at 0.01 mg/ml increased wound strength by 100% at 5 days and by 60% at 10 days (P less than 0.05 and P less than 0.05). However, EGF at 0.001 mg/ml and 1.0 mg/ml appeared to have no effect on wound strength. Histologic examination of full-thickness wounds in a separate series showed an increase in wound fibroblastic response and a diminished fibrin clot at 5 days in rabbits treated with 0.1 mg/ml and 0.01 mg/ml. We conclude that EGF enhances the wound strength of full-thickness corneal wounds in a dose-dependent manner which may be explained in part by an increased fibroblastic response. Concentrations of EGF greater or less than an optimal dose may be less effective in enhancing corneal wound strength.