Connective tissue growth factor (CTGF) is a potent mitogen for angiogenesis-related fibrosis1. We compared the subretinal neovascular membrane (CNV) and associated fibrous tissue areas2 two weeks after single intravitreal injection of a safe dose of anti-CTGF antibody3, bevacizumab (IVB), and combination of anti-CTGF-IVB in a rat model of laser induced CNV.

Four laser spots, 2 disc diameters away from the optic disc, were applied to the right eye retinas of 48 pigmented rats, to induce subretinal bubble formation. The rats were categorized into 4 groups that received single intravitreal injection of 2µl of the 50µg/ml anti-CTGF (A) , 2µl of 25mg/ml IVB (B), and a combination of 1µl anti-CTGF and 1µl IVB (C). Group D received no injection. After 2 weeks, double immunohistochemical staining was performed by anti-lectin for CNV and anti-collagen type1 for subretinal fibrosis on the sclerochoroidal flat-mounts. Masked measurement of the fluorescent images of the CNV and subretinal fibrosis (SRF) areas was performed by using the ImageJ software.

After 2 weeks Mean ± SD of CNV area in groups A (41,258 ± 13,688µm2), B (47,976 ± 15,141µm2), and C (38,405 ± 13,956µm2) were significantly less than group D (65,174 ± 18,836µm2) (P <0.001). Additionally, Mean ± SD of subretinal fibrosis area in group D (66,602 ± 31,444µm2) was notably greater than groups A (37,070 ± 14,586µm2) and C (35,939 ± 13,166µm2) (p<0.001) but not statistically different from group B (54,624 ± 20,890µm2). The SRF to CNV area ratio in groups A to D was 0.94, 1.18, 1.04 and 1.01 respectively.

To our best knowledge, this is the first time evaluation of the anti-fibrotic effect of CTGF neutralization via intravitreal injection in an animal model of laser induced CNV. In this study, we noticed significant reduction of the CNV associated subretinal fibrosis by CTGF inhibition that mediates the final steps of fibrosis in various inflammatory, angiogenic and restorative pathways.