Therapeutic Effects of Epidermal Growth Factor on Benzalkonium Chloride–Induced Dry Eye in a Mouse Model

Abstract

PURPOSE: To investigate the therapeutic effects and possible mechanisms of epidermal growth factor (EGF) on the mouse dry eye model induced by benzalkonium chloride (BAC). METHODS: The eye drop containing EGF was topically administered (3 ng per day) on a BAC-induced dry eye model. The following clinical indications of dry eye were evaluated on Days 2, 4, and 6: tear break-up time (BUT), corneal fluorescein staining, inflammatory index, and tear volume. Global specimens were collected on Day 6 and then the following examinations were performed: histologic investigation, TUNEL assay to measure the dead cells, periodic acid-schiff (PAS) assay to detect goblet cells, and immunostaining of antibodies of Ki-67, EGF receptor (EGFR), and MUC1 in the corneas. The levels of EGFR and p-ERK of the corneas were also measured by Western blot analysis. RESULTS: EGF resulted in longer BUTs on Days 2 and 6, lower fluorescein staining scores on Days 4 and 6, while no significant changes in inflammatory index or tear volume. EGF induced higher EGFR expression in corneal tissues by immunofluorescent staining and Western blot analysis. EGF also upregulated p-ERK, increased Ki-67 positive cells, and decreased TUNEL positive cells. In addition, EGF significantly increased the goblet cells number and MUC1 expression in the epithelium. CONCLUSIONS: Topical application of EGF presented clinical improvements on dry eye by stabilizing the tear film and maintaining the integrity of epithelium. The results indicate that EGF has potential as a therapeutic agent in clinical treatment of dry eye.