MATRIX METALLOPROTEINASES ARE EXPRESSED DURING WOUND-HEALING AFTER EXCIMER-LASER KERATECTOMY

To determine the expression of matrix metalloproteinases (MMPs) in cor nea following excimer laser keratectomy, two sets of experiments were performed. In the first experiment, disciform excimer keratectomy was performed on rat corneas. The central regenerating epithelium was harv ested at 3-96 h postwounding. MMP levels were assayed in the regenerat ed central epithelium and the stroma using zymography and immunoblot a ssays. In the second set of experiments, deep excimer annular keratect omy was performed on rabbit corneas to induce intrastromal epithelial migration, The effect of beta-mercaptomethyl tripeptide, a synthetic i nhibitor of metalloproteinase, on the presence and extent of intrastro mal epithelial migration was determined. In experiment I, MMP-2 and MM P-9 were expressed in the epithelium of excimer-ablated rat corneas 6- 24 h postwounding, but not in the debridement wounds and untreated con trols. Only excimer-treated stroma showed MMP-9 activity. In experimen t II, intrastromal epithelial migration was delayed by topical applica tion of beta-mercaptomethyl tripeptide, a synthetic inhibitor of MMPs (p < 0.05). After excimer wounds, MMPs are expressed in corneal epithe lium and stroma during wound closure. They may play an important role in wound healing after excimer laser keratectomy.