Purpose: To study RhoA activation and the effect of the Rho-kinase inhibitor in the development of retinal neovascularization in a mouse model of oxygen-induced retinopathy (OIR).
Methods: C57BL/6 mice at postnatal day (P7) were exposed to hyper-oxygen for 5 days and returned to room air for 5 days to induce OIR. RhoA-GTP, an active form of RhoA, in retinas at P12, P13 and P17 was detected. Mice received a single intravitreal injection of Y27632 (5 mu M or 50 mu M), a Rho-kinase inhibitor, in one eye during the transition from oxygen to room air at P12. Contralateral eyes were used as the control. Fluorescein-conjugated dextran angiography of retinal whole mount was prepared to score features of neovascular retinopathy at P17. The preretinal neovascular nuclei quantification was performed in frozen sections as well to evaluate the neovascularization.
Results: The retinal RhoA-GTP in OIR mice significantly increased from 0.24 +/- 0.06 at P12 to 0.38 +/- 0.12 at P13 (p < 0.05). The median total retinopathy score of 5.7 was significantly lower in eyes treated with Y27632 than controls (p < 0.001). Significant improvement was found in the specific categories of vascular tufts (p < 0.01) and extraretinal neovascularization (p < 0.05) in treated eyes. Those treated eyes also had a significantly decreased number of neovascular nuclei (p < 0.01).
Conclusions: These results suggest that Rho/Rho-kinase signaling pathways are involved in the early process of hypoxia-induced retinal neovascularization and Y27632 might have therapeutic potential for the treatment of retinal neovascularization.