Suppression of choroidal neovascularization by intramuscular polymer-based gene delivery of vasostatin

The purpose of this study was to evaluate the efficacy of gene delivery of angiogenesis inhibitor, vasostatin (VS), in suppressing experimental model of choroidal neovascularization (CNV). A mammalian expression vector carrying VS, pCMV3-VS, was constructed and evaluated for its ability to produce VS in transfected cells using western blot analysis and a cell viability assay. CNV was induced in Brown Norway rats by fundus argon laser photocoagulation and evaluated by fundus fluorescein angiography (FAG). Ten days post-laser treatment, gene delivery was achieved by intramuscular (IM) injection of poly-(N-vinyl pyrrolidone) (PVP) polymer conjugated with pCMV3-VS (PVP-VS) or a control vector (PVP-vector). Systemic VS expression was analysed by western blot analysis and enzyme linked immunosorbent assay (ELISA), and the extent of CNV was monitored by FAG analysis at different time intervals post-PVP treatment. Transfection of pCMV3-VS into muscle cells resulted in increased production and release of exogenous VS, which specifically inhibited the proliferation of endothelial cells. Besides, IM injection of PVP-VS, but not PVP-vector, led to elevated VS level in plasma for 30 days. After laser photocoagulation, rats injected with PVP-VS exhibited significantly lower incidence of CNV comparing with animals of control groups (P < 0.01) for at least 42 days. Moreover, rats treated with PVP-VS also showed a significant reduction in the CNV lesions compared with control groups (P < 0.001) for at least 42 days. Above all, no overt adverse effects were observed in rats received PVP-VS. These results demonstrate the potential of IM VS gene delivery for CNV treatment.