Matrix metalloproteinases in epithelia from human recurrent corneal erosion.

PURPOSE To assay for the presence of matrix metalloproteinases (MMPs) in human corneal epithelium affected by recurrent erosion compared with that in normal corneal epithelium. METHODS Corneal epithelial debridement samples were obtained from 13 patients with recurrent epithelial erosion. For control specimens, epithelia were obtained from healthy patients undergoing photorefractive keratectomy. Zymography was performed on all samples to identify MMPs. Immunolocalization of MMP-2, laminin, and collagen type VII was determined in two samples with human recurrent epithelial erosion and compared with that in control epithelium. RESULTS Twelve of 13 erosion samples showed MMP-2 enzymatic activity; one of the 12 also showed MMP-9 activity. Only one erosion sample showed no MMP enzymatic activity. All normal control specimens were negative for MMP. Immunohistochemical analysis of two recurrent erosion samples showed MMP-2 presence in basal cells, whereas, in normal epithelium it was not detected. One sample with epithelial erosion showed laminin localization in basal epithelial cells and basal lamina. Type VII collagen localized in basal epithelial cells only in this sample. A second erosion sample showed localization of laminin and type VII collagen in basal epithelial cells only. Normal corneal epithelium showed presence of laminin and type VII collagen in basal epithelium and basal lamina. CONCLUSIONS Matrix metalloproteinase-2 expression is upregulated in human epithelia affected by recurrent erosion compared with that in normal control samples. Immunolocalization studies suggest that this enzyme is concentrated in basal epithelial cells where it may play an important role in degradation of the epithelial anchoring system and the recurrent epithelial slippage and erosion observed in these patients.