Effects of the matrix metalloproteinase inhibitor GM6001 on the destruction and alteration of epithelial basement membrane during the healing of post-alkali burn in rabbit cornea

Purpose: To examine the alteration in structure and matrix composition of epithelial basement membrane (BM) during the healing of alkali-burned rabbit cornea. and the roles of matrix metalloproteinases (MMPs) in these alterations. Methods: The central cornea of one eye of 78 albino rabbits was exposed to IN NaOH for 180s under general and topical anesthesia and allowed to heal with or without subconjunctival injection of GM6001 (an MMP inhibitor). Cryosections of affected corneas were observed by H&E staining, immunohistochemistry for type IV collagen subtypes, or in situ zymography for detection of localization of MMP activity. Results: Uninjured corneal epithelial BM exhibited alpha 5 (IV)-immunoreactivity. but lacked the alpha 1/alpha 2-immunoreactivity of collagen IV. Epithelial BM in healing burned cornea transiently exhibited alpha 1/alpha 2-immunoreactivity. Examination by in situ zymography showed an upregulation of MMP activity in the regenerated central epithelium and anterior stroma of the burned corneas at days 7 and 14. GM6001 suppressed degradation of alpha 5-containing epithelial BM in vivo and also in organ culture. Conclusions: Epithelial BM was degraded by endogenous MMPs during healing following an alkali burn in rabbit cornea. GM6001 had an inhibitory effect on the degradation of the epithelial basement membrane in burned cornea in vivo.