Role of ocular complement factor H in a murine model of choroidal neovascularization

The objective of this study was to explore the relationship between local (ie, ocular) complement factor H (CFH) and choroidal neovascularization (CNV) associated with wet age-related macular degeneration (AMD), a leading cause of irreversible blindness, in laser-treated C57BL/6 mice. Immunohistochemical and RT-PCR analysis of retinal pigmented epithelium (RPE)-choroid sclera revealed that the expression of CFH was down-regulated on day 1 with a dramatic increase on days 5 and 7 postlaser injury. Flat mount and Western blot analysis further revealed that membrane attack complex (MAC) expression was up-regulated on days 1 and 3 postlaser injury; however, MAC was down-regulated on days 5 and 7 postinjury but was still higher than in non-injured mice. Similar patterns for CFH and MAC were observed for RPE cells when serial paraffin sections of the laser spots were analyzed. Subretinal injection of siRNA directed against CFH resulted in a threefold suppression of CFH in the RPE and choroid without affecting either CFH levels in the liver or the functional activity of the alternative pathway in the peripheral blood. Ocular knock-down of CFH resulted in increased MAC deposition, which leads to the early onset as well as exacerbation of laser-induced CNV. In conclusion, our findings provide evidence that CFH present on RPE and choroid regulates local MAC formation that is critical for the development of laser-induced CNV.