The effect of intravitreal ranibizumab on apoptosis induction in rat retinal tissue

Purpose
Despite the rapidly accumulating knowledge on pharmacokinetic properties and dosage of ranibizumab, the influence of this vascular endothelial growth factor inhibitor on retinal cell survival/apoptosis homeostasis remains unclear. The aim of this study was to investigate the biological effects of a single intravitreal injection of ranibizumab on retinal tissue with a focus on apoptosis-related signaling pathways in the rat retina.

Material and methods
Male Wistar rats were treated with an intravitreal injection of ranibizumab or anti-rat vascular endothelial growth factor antibody in the right eye. The left eyes were injected with the same volume of physiological saline. On the 3rd and 7th day post-injection, the eyes were enucleated, and the retinas were isolated for further molecular analysis of the expression of selected apoptosis-related molecules at mRNA (BAX, BCL-2) and protein (caspase-3) levels using quantitative RT-PCR and western blot techniques, respectively.

Results
Following a 3-day-exposure to ranibizumab at the established concentration, the BAX/BCL-2 mRNA expression ratio was significantly increased compared to the saline-treated controls and the healthy control eyes. Furthermore, on day 3. post ranibizumab injection, caspase-3 cleavage, detected qualitatively using western blotting, confirmed potential activation of the ir¬reversible phase of apoptosis. In contrast, on day 7. post-injection, there were no significant differences in the BAX/BCL-2 mRNA expression ratios or caspase-3 cleavage between different groups.

Conclusions
Intravitreal administration of ranibizumab leads to a transient induction of apoptosis in retinal cells, with an onset directly after the vascular endothelial growth factor inhibitor administration and apparent down-regulation shortly afterwards. These results must be considered when intravitreal injections of ranibizumab are administered to treat retinal diseases.