Inhibition of choroidal neovascularization by a peptide inhibitor of the urokinase plasminogen activator and receptor system in a mouse model.

OBJECTIVES To determine the role played by the urokinase plasminogen activator (uPA) and urokinase plasminogen activator receptor (uPAR) system in choroidal neovascularization (CNV) and whether inhibition of this system can suppress the extent of CNV in an animal model. METHODS Choroidal neovascularization was induced in mice by laser photocoagulation using the slitlamp delivery system. Reverse transcriptase-polymerase chain reaction and immunocytochemical analysis were performed on the retina choroids of these animals to examine the expression of uPAR. For 2 weeks following laser treatment, animals were injected intraperitoneally with a novel peptide inhibitor of the uPA-uPAR system (100 mg/kg twice a day every day, every other day, and once a week). Control laser-treated animals receive an intraperitoneal injection of phosphate-buffered saline every day. Following treatment, animals were perfused with fluorescein-labeled dextran, eyes were removed, and the areas of new vessels were examined in the retina-choroid whole mounts by fluorescence microscopy and quantitated using image analysis software. RESULTS In this study, uPAR was found to be up-regulated in the choroidal tissues of mice with laser-induced CNV. The uPAR was localized to the endothelial cells of the fibrovascular tissue within the CNV complex. Systemic administration of the peptide inhibitor of the uPA-uPAR system resulted in a significant reduction of CNV (up to 94%). The response was found to be frequency-of-dose dependent. No toxic effects or tissue destruction was noted following the peptide treatment. CONCLUSIONS Our results strongly suggest that up-regulation of the uPA-uPAR system is an important step during CNV, and significant inhibition of CNV was seen when cell surface-associated uPA-uPAR activity was prevented with the peptide inhibitor. Clinical Relevance Inhibition of the protease system (uPA-uPAR) may prove to be a potential novel antiangiogenic therapy for CNV as seen in age-related macular degeneration.