Inhibitory effects of plasminogen fragment on experimentally induced neovascularization of rat corneas

Background: Corneal neovascularization plays an important role in the pathogenesis of a number of corneal disorders. Recently a polypeptide was demonstrated, generated by the primary tumor, that inhibited angiogenesis and growth in metastases. This polypeptide is similar to a 38-kDa plasminogen fragment. Methods: We surgically implanted into rat corneal stroma a slow-release ethylene-vinyl-acetate (EVA) copolymer pellet containing basic fibroblast growth factor (bFGF) to induce corneal neovascularization. Then we applied aqueous solution containing plasminogen fragment to the rat cornea in order to observe the degree of inhibition of angiogenesis. Results: In the eyes of control rats, neovascularization from the limbus to the pellet occurred, graded 4+ in all five animals. In plasminogen fragment-treated rats, there was virtually complete inhibition of the neovascular response to the pellet. Of five treated rats, three showed no neovascularization and two demonstrated grade 1+ neovascularization. The difference in the degree of neovascularization between control and plasminogen fragment treatment was statistically significant (P < 0.05). Conclusion: Our studies provide the first direct evidence that rat corneal neovascularization is inhibited by instillation of plaminogen fragment. This agent may prove useful in the treatment of corneal angiogenic disorder.