Tear EGF Concentration Following Corneal Epithelial Wound Creation

The effect of corneal epithelial wound creation on epidermal growth factor (EGF) concentration in tears was evaluated in order to better understand the effects of EGF on the wound healing process. The tears of New Zealand white rabbits were sampled by micropipette one day prior to wounding, immediately prior to the creation of a 7.5 mm diameter anterior keratectomy wound, immediately following wound creation, and at 1, 2, 3, 7, and 14 days following wounding. A volume of 50 microL was taken at each sampling time, and all tear samples were assayed for EGF by an enzyme linked immunosorbent assay (ELISA). The results demonstrated that the concentration of EGF in the tear layer rises dramatically immediately following wound creation. The basal measured EGF concentration was approximately 600 pg/mL; immediately following wound creation, this rose to approximately 1600 pg/mL. By 1 day following creation of the wound, the concentration of EGF in the tears had returned to the basal level. A second, marginally significant increase in the tear concentration was noted at 3 days post wounding. The EGF concentration in the tears were not significantly different at any other time. The measured dramatic rise in EGF concentration in the tears in response to the creation of a corneal epithelial wound provides further evidence of the importance of tear EGF in the wound healing process. The concentrations in all cases were on the order of ng/mL, suggesting that the intercellular concentrations in this range result in optimal cell stimulation.