The histopathological effects of intravitreal golimumab injection on the retina of rabbit eyes

Purpose: The aim of this study is to evaluate the histopathological effect of intravitreal injection of Golimumab (anti-TNF) on the retina in rabbit eyes. Methods: 16 rabbits (New Zealand albino rabbits) were included in the study. The rabbits were divided into 3 groups. Intravitreal injections of Golimumab [group 1 (n=6): 5 mg / 0.05 ml, group 2 (n=6): 10 mg / 0.1 ml, group 3 (n=4): 20 mg / 0.2 ml] were performed to the right eyes, while sham injections with the same volume were administrated to the left eyes. The eyes of the rabbits were followed daily for a week. After one week of follow-up, the rabbits were sacrified and the eyes were enucleated. Eye tissues were prepared for light microscopic immunohistochemical examination (TUNEL and Caspase-3 staining) which showed apoptotic activation and ultrastructural examination under electron microscopy. Results: In hematoxylin-eosin (H&E) staining, none of the histological sections of the study eyes showed any evidence of retinal layer loss macroscopically. In all of the three different doses (5 mg / 0.05 ml, 10 mg / 0.1 ml and 20 mg / 0.2 ml), while number of the cells in outer nuclear (p=0.001, p=0.044 and p=0.045 respectively) and inner nuclear (p=0.047, p=0.045 and p=0.048 respectively) layers were decreased in Golimumab group compared to sham group; there was no significant difference in ganglion cell count (p = 0.11, p = 0.067 and p = 0.20, respectively) between three groups. In 5 mg/0.05 ml Golimumab injected eyes, there was no significant difference in the percentage of TUNEL staining in outer nuclear layer compared to control group, while the percentage of Caspase-3 staining of the same layer was significantly higher than the control group. (p = 0.061 and p = 0.048, respectively). For the same dose, in inner nuclear layer, TUNEL and Caspase-3 staining percentages were significantly higher in Golimumab group compared to control group. (p = 0.018 and p = 0.015, respectively) For 10 mg / 0.1 ml and 20 mg / 0.2 ml doses, TUNEL and Caspase-3 staining percentages in the outer and inner nuclear layers were found to be significantly higher than the control groups. (For TUNEL staining, p = 0.009, p = 0.020, p = 0.029 and p = 0.029 respectively, for Caspase-3 staining p = 0.041, p = 0.04, p = 0.048 and p = 0.041 respectively). In ganglion cell layer, for all dose groups, neither TUNEL nor Caspase-3 staining percentages showed any significant difference between Golimumab and control groups (For TUNEL staining, p = 0.937, p = 1.000 and p = 1.000 respectively, for Caspase-3 staining p = 0.064, p = 0.163 and p = 0.198 respectively). Caspase-3 staining didn't show any significant higher apoptosis rates in increasing doses of Golimumab, therefore we didn't find any statistically significant dose-dependent relationship (p = 0.555, p = 0.092 and p = 0.877, respectively). Discussion: Intravitreally administered TNF-α antagonist Golimumab caused apoptosis in both photoreceptors and bipolar cells in rabbit retina. Since there was increased retinal cell death in Golimumab injected eyes compared to control eyes for all of the three different doses (5 mg / 0.05 ml, 10 mg / 0.1 ml and 20 mg / 0.2 ml), potential toxicity of intravitreal Golimumab injections at these doses should be considered during treatment plan. Keywords: Apoptosis, Golimumab, intravitreal anti-TNF drugs, retina