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Eunice Cheung, Ivan B. Lobov, Rajeevalochan Wudali, George D. Yancopoulos, Stanley J. Wiegand; Combined anti-PlGF and anti-VEGF Therapy Ameliorates Pathological Neovascularization and Improves Retinal Revascularization in the Murine Model of Oxygen Induced Ischemic Retinopathy (OIR). Invest. Ophthalmol. Vis. Sci. 2011;52(14):6064.
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Placental Growth Factor (PlGF) drives VEGF pathological angiogenesis through its affinity to and activation of VEGF Receptor 1 (Flt-1). [Luttun et al., Nature Med. 2002, 8:831-840]. Previously, we reported that the genetic deletion or pharmacological inhibition of PlGF reduced the extent of vasoobliteration and pathological neovascularization in OIR [IOVS 2009; 50:E-Abstract 2943; IOVS 2010; 51:E-Abstract 4486]. In these studies, we administered an anti(α)VEGF-A antibody alone or in combination with αPlGF antibody after vessel loss was complete, to evaluate the effects of dual VEGF and PlGF inhibition in the murine model of OIR.
Mice were place in a hyperoxic environment (75% O2) at P6 and returned to room air at P11. The left eyes were injected intravitreally (ITV) with Fc (control), αMouse Polyclonal VEGF-A (R&D systems), or 1:1 combination (αMouse VEGF-A and αMouse PlGF-2 Polyclonal Ab (R&D systems)) at P13. Retinal flatmounts were collected at P16 (Study 1) or P17 (Study 2) and stained with FITC-labeled Griffornia simplicifolia lectin I (Vector Laboratories). To analyze the potential contribution of VEGFR2 blockade to the effects of combined PlGF and VEGF inhibition, DC101, a VEGF Receptor 2 (Flk-1)-selective blocking antibody, was injected ITV at P13 and collected at P17 (Study 3).
The effects of αVEGF and combined αPlGF/αVEGF treatments were very similar in Study 1. Both groups exhibited similar residual avascular areas of similar size, and little to no neovascularization was evident. In Study 2, in which the duration of exposure was extended by 24 hours, αVEGF+αPlGF-treated retinas showed greater reductions in the residual avascular areas comparing to retinas treated with αVEGF alone, indicating the concomitant inhibition of PlGF enhanced normal blood vessel regrowth. Both single and combined treatment groups continued to display similar high reductions in the area of neovascularization at this latter time point. By contrast in Study 3, selective inhibition of VEGFR2 activity by administration of DC101 resulted in an increased avascular areas and more extensive retinal neovascularization compared to the Fc-treated control group.
This study demonstrates that pharmacological inhibition of both PlGF and VEGF can improve normal blood vessel regrowth, in addition to ameliorating pathological neovascularization. Moreover, inhibition of VEGFR1 activity appears to be an essential prerequisite for both effects.
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