Inhibition efficacy of CFB-siRNA on laser-induced choroidal neovascularization in rat

Abstract

Background Choriodal neovascularization is an important ocular manifestation of angiogenesis in eyes,which derives from the choroid capillaries.Recent studies have found that complement activation is playing a key role in the laser-induced CNV.Because of the key position of CFB in the alternative pathway,bytargeting CFB and blocking the alternative pathway may provide an approach to observe the role of this alternative pathway in the generation of CNV. Objective This study was to investigate the inhibitory effect of reconstructed complement factor B (CFB)-small interfering ribonucleic acid (siRNA) on choroidal neovascularization (CNV)and its mechanism. Methods Experimental CNV was induced by laser photocoagulation in 96 eyes of 48 clean Brown Norway rats.The rats were randomly divided into 4 groups.25,50 and 75 μg B factor siRNA were injected via caudal vein on 1 day,3,5 days after photocoagulation in different dose groups,and normal saline solution was injected at the same way in experimental control group.Other 12 normal rats were used as blank control group.Fundus fluorescein angiography(FFA) was performed on 3,7,14,21,28 days after injection of CFB-siRNA and CNV was scored.The expressions of vascular endothelial growth factor(VEGF) and factor Ⅷ in choroid were detected by immunochemistry.The expressions of CFB-siRNA,VEGF,transforming growth factor β2( TGF-β2 )proteins in choroid were determined using immunochemistry in 7,14,21,28 days,and the expressions of mRNA of CFB-siRNA,VEGF,TGF-β2 were examined by reverse transcription polymerase chain reaction(RT-PCR). Results FFA revealed that the CNV rates in various doses of CFB-siRNA groups were significant lower than those of experimental control group in various time points(P＜0.05),and those in 75 μg B factor siRNA were decreased in comparison with 25 μg B factor siRNA (P＜0.05).Immunochemistry showed that the intensities of the VEGF and factor Ⅶ expression in various doses of CFB-siRNA groups were weaker than the blank control group ( P ＜ 0.05 ).Compared with the control group,the expression of CFB reduced in 7 days,and then approached to the level near the control group.Fourteen to twenty-one days after injection of CFB-siRNA,VEGF and TGF-β2 depressions in different doses of CFB-siRNA groups were lower than blank control group( P＜0.05 ).CFB expression in choroid showed the lower levels in CFB-siRNA injection group compared with blank control group in from 7 through 21 days (P＜0.05).RT-PCR displayed the gradual increase of CFB mRNA and curve-like changes of VEGF and TGF-β2 with time prolong. Conclusions Recombinated CFB-siRNA can effectively inhibit laser-induced CNV by down-regulating the expression of VEGF and factor Ⅷ.Alternative pathway of complement plays an important role in the production of CNV. Key words: Choroidal neovascularization/management; Gene therapy; Complement factor B; Small interfering RNA