Expression of matrix metalloproteinase-2 (MMP-2) and vascular endothelial growth factor (VEGF) in inflammation-associated corneal neovascularization

Matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-9 (MMP-9) and Vascular endothelial growth factor (VEGF) are all implicated in the develop ment of neovascularization. To investigate the possible role of these facto rs in corneal neovascularization we have analysed the expression of MMP-2, MMP-9 and VEGF in a rat model of inflammation-associated corneal neovascula rization. In this model, corneal neovascularization was induced in Long-Eva ns rats by krypton laser photocoagulation whereafter eyes were enucleated a t 1, 4, 7, 10 and 20 days. Slit-lamp biomicroscopy and histologic analysis revealed a gradual development of corneal neovascularization that peaked 7- 10 days after treatment when newly formed vessels could be seen throughout the corneal surface reaching deep into the stroma. Antisense and sense ribo probes were generated using DNA complementary to MMP-2, MMP-9 and VEGF, and mRNA expression was analysed using in situ hybridization. The expression o f MMP-2 and MMP-9 in untreated corneas was low or absent whereas VEGF was w eakly expressed in the corneal epithelium. MMP-2 expression was increased d uring corneal neovascularization and was mainly localized to the cells infi ltrating areas of new vessel formation. Many of these cells appeared to be inflammatory cells. VEGF expression had a similar overall distribution to M MP-2 during neovascularization with the exception that its expression in th e corneal epithelium remained and even increased slightly. MMP-9 was promin ently expressed at the border of regenerating corneal epithelium in areas w ith epithelial wounding but was not detected in the vascularized stroma. To gether, the results of the present study support a role for MMP-2 and VEGF in inflammation-associated corneal neovascularization whereas MMP-9 instead appears to be involved in corneal epithelial wound-healing. (C) 2000 Acade mic Press.