Inhibitory Effect Of A Small Interfering RNA Targeting VEGF On Retinal Neovascularization In Mice

Objective To investigate the inhibitory effect of a small interfering RNA targeting VEGF on retinal neovascularization in mice.Methods (1) According to Smith, the mouse(C57BL/6J) model of oxygen- induced retinopathy with retinal neovascularization was set up through exposure of postnatal day 7(P7) to 75±3% oxygen for 5 days. Fluorescein conjugated Dextran angiography of retinal vascular was performed to observe the formation of retinal neovascularization. (2) The normal group: 8 mice of postnatal day 7 were raised in the room air. (3) 24 mice were exposed to 75%±3% oxygen for 5 days from P7 to P12. On P12, the animals were returned to the room air and divided to 3 groups randomly: control group, vector group and gene therapy group. The vector group was the P12 model mice injected with pSilencer2.1-U6 hygro. The gene therapy group was the P12 model mice injected with pSilencer2.1-U6 hygro-VEGF₁₆₅siRNA. The above all of plasmids were mediated by liposome. (4) Seven days later, the mice were put to death. Fluorescein conjugated Dextran angiography of retinal vascular was performed, retinal slides were prepared to score the number of nuclei extending beyond the inner limiting membrane and expression of VEGF was detected in the retina by immunohistochemistry.Results (1) The retinal blood vessels of the normal group formed a fined radial branching pattern. The retinal vascular patterns in the control group and the vector group were characterized by decreased central perfusion in both the superficial and the deep layers. The large vessels were distored and irregular in the two groups, the capillary was obstructed and lots of neovascular tufts. The retinal neovascularization and non-perfusion distraction in the gene therapy group was reduced markedly. (2) VEGF immunohistochemistry in retinal sections: the normal group was weakly positive; the control group and the gene therapy group were strong positive; VEGF expression of the gene therapy group was weaker than one of the control group and the vector group. (3)There were few vascular endothelial cell nucleus extending beyond the internal limiting membrane(ILM) in the normal group, while a large number of vascular endothelial cell nucleus in the control group and vector group were extending into ILM, incidence rate: 100%. Statistically, there is significant difference between the number of nuclei extending beyond the ILM of the gene therapy group(6.83±4.72) and the control group(11.57±5.85),the vector group(11.53±6.15).Conclusion Retinal neovascularization can be efficiently inhibited by intravitreal injection of the pSilencer2.1-U6 hygro-VEGF₁₆₅siRNA mediated by liposome.