Immunolocalization of Matrix Metalloproteinase-2, -9 and Tissue Inhibitor of Metalloproteinase-1, -2 in Suture-induced Corneal Neovascularization

ABSTRACT

PURPOSE: Metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) have been linked to the angiogenic process in general. In order to understand the potential roles of MMPs and TIMPs in corneal neovascularization process, we examined the expression and activities of MMP-2, MMP-9, TIMP-1 and TIMP-2 during the course of suture-induced corneal neovascularization in rat model. METHODS: Corneal neovascularization of rat cornea was induced by suturing. The expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 in sutured corneas was examined by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The activities of MMP-2 and MMP-9 were measured before and after suture by gelatin zymography. RESULTS: MMP-2 proenzyme, and TIMP-1, -2 were expressed in normal corneas, predominantly in corneal epithelium. After injury, expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 increased, notably in healing corneal epithelium, infiltrating inflammatory cells, stromal fibroblasts, and ingrowing vascular endothelial cells. The intensity of immunostaining and enzymatic activities of MMP-2 and MMP-9 paralleled the magnitude of inflammatory cell infiltration, which peaked around day 7 after suture. Immunoreactivity of MMP/TIMP decreased significantly two weeks after suturing. At day 35 after suture, staining of MMP-2, TIMP-1, -2 remained visible only in corneal epithelium and vascular endothelial cells. CONCLUSIONS: MMPs as well as TIMPs were upregulated during suture-induced corneal neo-vascularization, suggesting that both may take part in extracellular matrix remodeling in the corneal wound healing, inflammatory, and neovascularization processes.