Expression of matrix metalloproteinases 2 and 9 and tissue inhibitors of metalloproteinase 1 and 2 in inflammation-induced corneal neovascularization

Purpose: Matrix metalloproteinases (MMPs) and tissue inhibitors of metallop roteinase (TIMPs) have been linked to the angiogenic process in general. In order to understand the potential roles of MMP-2, MMP-9 and TIMPs in the c orneal neovascularization process, we examined the expression and activitie s of MMP-2, MMP-9 and TIMPs during the course of cauterization-induced corn eal neovascularization in a rat model. Methods: Neovascularization of rat c orneas was induced by silver nitrate cauterization. The expression of MMP-2 , MMP-9, TIMP-1 and TIMP-2 was examined by immunohistochemistry and RT-PCR. The protein activities of MMPs and TIMPs were compared in pre- and postcau terization corneas by gelatin zymography and reverse zymography, respective ly. Results: MMP-2, TIMP-1 and TIMP-2 immunoreactivities were expressed in normal corneas, predominantly in the corneal epithelium. After injury, immu noreactivities of both MMPs and TIMPs were increased, notably in the healin g corneal epithelium, infiltrating inflammatory cells, stromal fibroblasts and ingrowing vascular endothelial cells. The increase in gross MMP-2 enzym atic activity paralleled the maximal vascular ingrowth on day 4, while the gross MMP-9 enzymatic activity rose immediately on day 1, then decreased st eadily, which paralleled the magnitude of inflammatory cell infiltration. T he immunoreactivity of MMPs/TIMPs decreased significantly 2 weeks after cau terization. On day 35, MMP-2, TIMP-1 and TIMP-2 staining was seen only in c orneal epithelium and vascular endothelial cells. Both the RT-PCR and rever se zymography results revealed a more constant expression of TIMP-2, while the TIMP-1 expression appeared to be more inducible. Conclusion: MMPs as we ll as TIMPs were upregulated in cauterization-induced corneal neovasculariz ation, suggesting that both may participate in extracellular matrix remodel ing in the corneal wound healing, inflammation and neovascularization proce sses. Copyright (C) 2001 S. Karger AG, Basel.