Connective tissue growth factor (CTGF) is the major pro fibrotic growth factor associated with the wide variety of fibrotic disorders such as proliferative diabetic retinopathy (PDR) and proliferative vitreoretinopathy (PVR). In the present study we determine the maximum safe dose of intravitreal injection of anti-CTGF (IVAC) in rat eyes.

45 Lister Hooded pigmented rats were divided into five groups; 4 of these groups received IVAC, corresponding to doses of 10 (B), 20 (C), 50 (D), and 100 μg/ml (E), respectively. The sham group (A) received intravitreal normal saline. Full field electroretinography (ERG) was performed at baseline and at days 7 and 28 after IVAC. The animals were euthanized and the corresponding eyes were subjected to routine histopathology, immunohistochemistry for Glial Fibrillary Acidic Protein (GFAP), and TUNEL assay.

Scotopic rod b wave amplitude and maximal combined b wave amplitude were 111.89±71.2?v and 178.57 ± 55.58 ?v respectively at baseline which reduced significantly after 28 days (79.31 ± 52.59 ?v and 128.73 ± 41.61 ?v, respectively) in the group E with 100 ?g/ml of IVAC (P<0.05) . There was no significant reduction of amplitudes in other groups with lower doses of anit-CTGF antibody and in the sham group. Reduction in oscillatory potentials was also noticed after 7 and 28 days in the group E (46.24±18.05 ?v at baseline, 30.03±15.95 ?v at 7 days, P<0.05 and 29.79±12.20 ?v at 28 days, P<0.001) but not in other groups. Photopic ERG responses did not show any significant change in any groups. Excepting 4 out of 9 eyes in group E that revealed retinal inner nuclear and ganglion cell layer atrophic changes, histologic findings were unremarkable in other groups. GFAP immune reactivity was not significant in any of the groups. TUNEL test showed inner retinal neural cell apoptosis in group E, but not in other groups.

ERG, histopathologic, and apoptotic assays revealed no toxic effects of 10 to 50 μg/ml IVAC in the rat eyes. A significant toxic effect was observed after100 μg/ml IVAC in terms of both functional and histopathologic findings.