Abstract
Hypoxia-inducible factor-1 (HIF-1) plays an important role in retinal and subretinal neovascularization (NV). Increased levels of HIF-1 cause increased expression of vascular endothelial growth factor (VEGF-A) and current therapies for ocular NV focus on neutralizing VEGF-A, but there is mounting evidence that other HIF-1-responsive gene products may also participate. In this study, we tested the effect of a designed ankyrin repeat protein (DARPin) that selectively binds and antagonizes the hypoxia-regulated gene product PDGF-BB in three models of subretinal NV (relevant to neovascular age-related macular degeneration) and compared its effects to a DARPin that selectively antagonizes VEGF-A. Daily intraperitoneal injections of 10 mg/kg of the anti-PDGF-BB DARPin or 1 mg/kg of the anti-VEGF DARPin significantly suppressed subretinal NV from laser-induced rupture of Bruch's membrane. Injections of 1 mg/kg/day of the anti-PDGF-BB DARPin had no significant effect, but when combined with 1 mg/kg/day of the anti-VEGF-A DARPin there was greater suppression than injection of the anti-VEGF-A DARPin alone. In Vldlr (-/-) mice which spontaneously develop subretinal NV, intraocular injection of 1.85 μg of anti-PDGF-BB or anti-VEGF-A DARPin caused significant suppression of NV and when combined there was greater suppression than with either alone. The two DARPins also showed an additive effect in Tet/opsin/VEGF double transgenic mice, a particularly severe model of subretinal NV and exudative retinal detachment. In addition, intraocular injection of 1.85 μg of anti-PDGF-BB DARPin strongly suppressed ischemia-induced retinal NV, which is relevant to proliferative diabetic retinopathy and retinopathy of prematurity. These data demonstrate that PDGF-BB is another hypoxia-regulated gene product that along with VEGF-A contributes to ocular NV and suppression of both provides an additive effect.
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