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R. G. Tytarenko, V. V. Lyzogubov, P. Jha, J. Liu, N. S. Bora, P. S. Bora; Role of Ocular Complement Factor H in Animal Model of Choroidal Neovascularization. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6188.
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This study was aimed to explore the relationship between local (i.e. ocular) complement factor H (CFH) and choroidal neovascularization (CNV) associated with wet age-related macular degeneration (AMD).
C57BL/6 mice received 20 or 80 pM of CFH siRNA, control siRNA and vehicle separately via the subretinal route using lipid based delivery system and CNV was induced in these animals by photocoagulation using Argon laser. For CFH siRNA localization experiments, the same dose of AF488 labeled siRNAs (CFH and control) were injected subretinally. Samples were collected on days 1, 3, 5 and 7 post-laser photocoagulation. Suppression of CFH was confirmed by RT-PCR and Western blotting. Alternative pathway activity in mouse serum was measured using a modification of the zymosan assay which measures C3 deposition on zymosan particles. The incidence as well as the size of CNV complex was determined using flat mounted RPE-choroid-sclera, confocal microscopy and ImageJ program. MAC deposition in RPE-choroid was evaluated by immunohistochemistry (IHC). IHC and ELISA were used to determine VEGF levels in RPE-choroid.
Subretinal injection of siRNA directed against CFH resulted in 3 fold suppression of CFH in the RPE and choroid without affecting CFH levels in the liver and the functional activity of the alternative pathway in the blood. Ocular knock-down of CFH resulted in increased MAC deposition and elevated VEGF levels which lead to the early onset as well as exacerbation of laser-induced CNV.
Our findings provide evidence that CFH present on RPE and choroid regulates local MAC formation essential for the release of VEGF that is critical for the development of laser-induced CNV. We propose that local inhibition of the alternative pathway of complement activation may be used as a therapeutic tool in the treatment of wet AMD in future.
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