Loss of FGF2 Retards Proliferation of Epithelial Cells in an Uninjured or a Penetrating Injured Cornea in Mice

Abstract

Abstract: : Purpose: To examine the roles of fibroblast growth factor 2 (FGF2) in regulating proliferation of corneal epithelial cells in vivo and in vitro. Methods: Experimental mice (34 Fgf2^+/+ and 42 Fgf2^–/–) were under both general and topical anesthesia. A penetrating wound was created with a hypodermic needle in one eye. At days 2, 5, and 10 post–injury the mice were sacrificed following a 2 hr–labeling period with bromo–deoxyuridine (BrdU). The number of BrdU–labeled cells and those positive in TUNEL staining in epithelium was determined. The effects of exogenous FGF2 and an inhibitor of MAP kinase, PD98059, on cell proliferation of SV40–immortalized human corneal epithelial cells (HCECs) were determined. Results: Penetrating injury in the central cornea did not stimulate nor inhibit cell proliferation of corneal epithelium. The number of BrdU–labeled corneal epithelial cells was statistically significantly less in Fgf2^–/– mice than in Fgf2^+/+ mice in both uninjured, and injured, conditions. There was no difference in number of cells undergoing apoptosis of epithelial cells between both groups as determined by TUNEL. In vitro studies showed that addition of 5.0 ng/ml FGF2 enhanced proliferation of HCECs and this growth–promoting effect was abolished by adding 50 µg/ml PD98059. Conclusions: FGF2 is required to support proliferating activity of corneal epithelium in mice. MAP kinase cascade is involved in FGF2’s cell proliferation–stimulating effect.

Keywords: cornea: epithelium • growth factors/growth factor receptors • wound healing