Purpose To investigate the inhibitory effect of intravitreally administered human complement factor H (CFH) in a rat model of laser-induced choroidal neovascularisation (CNV).

Methods Analysis of alternative pathway inhibition by human plasma-purified CFH was conducted by measuring C3 deposition on zymosan particles using rat serum. CNV was induced by laser photocoagulation on Day 0 in the eyes of Brown Norway rats. Human plasma-purified CFH (50 μg/2 μl) or phosphate buffered saline was injected intravitreally on Day 0 (prevention arm) or Day 7 (treatment arm). Seven days after injection, eyes were enucleated and retinal pigment epithelium-choroid-sclera flat mounts were prepared. Areas of CNV were determined in flat mounts and quantified using an image analysis programme. Flat mounts were also stained for membrane attack complex.

Results In rat serum, human CFH inhibited activity of alternative pathway in a dose-dependent manner. On Day 3, mean membrane attack complex deposition in laser-treated retina significantly decreased in CFH-treated eyes (p<0.001). In the prevention arm, the mean CNV area in CFH-treated eyes decreased by 27.0% compared with phosphate buffered saline-treated control eyes on Day 7 (p=0.011). In the treatment arm, the mean CNV area in CFH-treated eyes decreased by 38.3% compared with control eyes on Day 14 (p=0.001).

Conclusions Intravitreal injection of human CFH resulted in the suppression of formation of new, and regression of preformed laser-induced CNV in the rat model. Human CFH may be a feasible treatment for CNV associated with age-related macular degeneration or other causes.