: Retinal pigment epithelial (RPE) cells have been suggested to play an important role in epiretinal membrane (ERM) formation. Connective tissue growth factor (CTGF) as a downstream mediator of TGF-β, released by RPE cells has been found in ERMs. We compared the quality and quantity of ERM formation two weeks after the single intravitreal injection of a safe dose of anti-CTGF antibody alone, anti-VEGF (bevacizumab) alone, and combination of anti-CTGF/ bevacizumab in a rabbit model of RPE cell induced ERM formation.

With adherence to the ARVO regulations, intravitreal injection of 0.3 ml SF6 was performed in the right eyes of 24 adult male albino rabbits to induce posterior vitreous detachment. Three days later, human RPE cells obtained from the eye bank and being cultured by 2-3 passages were injected into the vitreous cavity over the optic disc (250,000 in 0.1 ml). Rabbits were categorized into four groups that received single intravitreal injection of 0.05 ml of 50µg/ml humanized anti-CTGF ( group A), 0.05 ml of 25mg/ml bevacizumab (group B), and 0.05 ml anti-CTGF plus 0.05 ml bevacizumab ( group C). No antibody injection was done in the control group (group D). After 2 weeks, epiretinal membrane formation was confirmed by indirect ophthalmoscopy; animals were sacrificed and paraffin embedded anterior-posterior sections were prepared from the right globes. Twenty sections of each eye stained by Masson-trichrome for collagen and twenty sections immunostained by humanized anti-alpha-smooth muscle for fibroblasts differentiated from RPE cells. Masked measurements of epiretinal membrane thickness, collagen tissue area and fibroblast counts on 10x light and fluorescent images (respectively) were performed by using the ImageJ software.

Means of ERM thicknesses, collagen tissue area and fibroblast cell counts in ERMs in three treatment groups (A, B, C) were significantly less than the control group (P<0.001). Means of fibroblast counts for groups A and C were also significantly less than group B (P<0.01).

In this experimental study, intravitreal injection of anti-CTGF antibody significantly reduced the RPE induced ERM formation via inhibiting CTGF as the mediator of the final steps of fibrosis in various inflammatory, healing and restorative pathways.