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Ruslana G. Tytarenko, Valeriy V. Lyzogubov, Liu Juan, Nalini S. Bora, Puran S. Bora; Intraocular Complement Activation by PEG-8 Induces Choroidal Neovascularization in Mice. Invest. Ophthalmol. Vis. Sci. 2011;52(14):949.
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Choroidal neovascularization (CNV) is the hallmark of wet age related macular degeneration (AMD). The role of complement activation in human AMD and animal models of AMD is well accepted. Low molecular weight polyethylene glycol (PEG-8) can activate the alternative pathway of the complement system. The aim of this study was to see if CNV can be induced by PEG-8.
Male C57BL/6 mice received a single injection containing different doses (0.125-2 mg) of PEG-8 via subretinal route and CNV was investigated in these animals from day 3 to day 42 post-injection. Control animals received a similar treatment with sterile PBS. In parallel experiments C57BL/6 mice received cobra venom factor (CVF) two days prior to PEG-8 injection to explore the role of complement. Levels of complement component C3, C3 activation products, membrane attack complex (MAC) and VEGF in PEG-8 and PBS injected animals were investigated by Western blotting, immunohistochemistry and ELISA.
Subretinal injection of PEG-8 resulted in increased levels of C3 split products, MAC and VEGF in RPE-choroid as early as day 1 after treatment compared to similar treatment with PBS. High resolution confocal microscopy revealed that a single subretinal injection of PEG-8 induced penetration of Bruch’s membrane by choroidal endothelial cells at day 1 post-injection in the areas of increased C3 and MAC deposition.Confocal microscopy of RPE-choroid-scleral flat mounts detected CNV in C57BL/6 mice as early as day 3 post-injection. Fully developed CNV complex was observed at day 5 after PEG-8 injection. CNV did not develop in PBS injected control mice. Interestingly complement depletion using CVF inhibited the development of PEG-8 induced CNV and MAC deposition in the laser spots.
Our results demonstrate that activation of ocular complement by PEG-8 leads to increased levels of MAC and VEGF. This results in the induction of CNV. Thus, we describe a new, inexpensive and accelerated mouse model of CNV using PEG-8. We believe that this new model will be of use in future to study wet AMD.
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