The Anti-angiogenic Effect of Recombinant Tissue Inhibitor of Metalloproteinase Type 2 (TIMP-2) in N-heptanol Induced Neovascularization of Rat Cornea

ABSTRACT

Corneal neovascularization is a challenging problem in ophthalmologic practice. We evaluated the anti-angiogenic effect of recombinant tissue inhibitor of metalloproteinase type 2 (rTIMP-2) which is an endogenous inhibitor of matrix metalloproteinases. Sprague-Dawley rats of 6 weeks of age were used in this study. N-heptanol was applied to the eyes of the rats to induce chemical injury and eventual neovascularization. The rats were divided into 4 groups, 5 rats for each. We instilled only the phosphate buffered solution once a day for 10 days to the eyes of rats in the control group. Rats in group 1 received subconjunctival injection of 0.05 mgof rTIMP-2, those in group 2 received intraperitoneal injection of 0.05 mg of rTIMP-2, and those in group 3 received intraperitoneal injection of 0.1 mg of rTIMP-2 once a day for 10 days respectively. After 4 weeks, photographs of corneas were taken with a built-in camera of the slit lamp, and the eyes were enucleated. We made histologic specimens of the corneas and examined them with a light microscope. The severity of the neovascularization was quantified with angiogenesis scoring system. The group 1, 2 and 3 showed significant suppression of angiogenesis compared with the control respectively, but there was no statistically significant difference among their angiogenesis scores. Under the light microscope, the corneas of control group showed much more severe infiltration of inflammatory cells and higher density of new vessels compared with group 1, 2 and 3. We hypothesize that TIMP-2 suppressed the angiogenesis in chemical injury of cornea and TIMP-2 might benefit those patients with corneal neo-vascularization, although careful further studies are required in humans.