Inhibition Of Retinopathy Of Prematurity By Intravitreal Injection Of The Sorafenib

Objective: To investigate the effect of intravitreal injection administered sorafenib, in a rat model ofoxygen-induced retinopathy (OIR) and to provide a theoretical basis for sorafenib treating retinopathy ofpremature.Method: Seven-day-old Sprague-Dawley rats (n=216) were divided into six groups randomly, as follows:A. controlled group; B. ROP group; C. vehicle-treated ROP group; D.5μg sorafenib-treated ROP group; E.20μg sorafenib-treated ROP group; F.80μg sorafenib-treated ROP group. Group A received normal partialoxygen pressure from birth to postnatal day17(P17). Groups B, C, D, E and F were exposed to hyperoxia（85%±2%）from P7to P12to induce OIR modle. Then, at P12, the rats were returned to normoxia tillP17. Left eyes of the rats in groups D, E and F were received intravitreal injections of5μL sorafenib (5μg,20μg and80μg respectively) solution at P12. Left eyes of the rats in groups C were received intravitrealinjections of5μL DMSO as the vehicle treated group. Then the retinas were whole-mounted and stainedwith Fluorescein labeled GSLⅠ–isolectin B, and imaged with a confocal microscopy. The vascularbranching points were counted to quantify neovascularization in high magnification at P17. Cross-sectionsof the retina were stained with hematoxylin and eosin (HE). The nuclei of new vessels breaking the internallimiting membrane were counted to quantify the proliferative neovascular response. RT-PCR was used todetect the expression of VEGFR-2m RNA and PDGFR-β mRNA. Immunochemistry was used to detect theexpression of VEGFR-2protein and PDGFR-β protein.Result: Retinal flat mounts and cross-sections with HE staining show the morphological structure of retinalnew vessels. The retinal vessel in group B and C turned into tortuosity. Moreover, great deals ofneovascularization were observed. Sorafenib-treated rats had significantly less neovascularization ascompared with vehicle-treated and control rats in a dose dependent manner. The number of vascularbranching points in A, B, C, D, E and F were16.50±3.90,37.44±6.47,37.08±5.10,30.80±6.85,26.08±5.08and19.83±3.51, respectively. The number of the nuclei of retinal new vessel in A, B, C, D, E and F were0.22±0.42,35.66±4.70,35.30±4.54,27.30±4.28,21.41±3.53and7.41±2.87, respectively. There weresignificant difference between each group (P＜0.05) except group B and C. The mRNA level expressionand the protein of VEGFR-2in group B and C, was significantly more than other groups. The expression ofVEGFR-2mRNA and VEGFR-2protein in group D, E, and F was decreased in sequence. But theexpression of PDGFR-β mRNA and protein were undetected with immunochemistry and RT-PCR.Conclusion: In the rat OIR model, sorafenib could inhibit retinal neovascularization in a dose dependentmanner. Inhibition achieved mainly through VEGF/VEGFR-2signaling pathway. We speculated that it isdue to immaturity of neonatal rats, the extremely lower retinal tissue pericytes contented, the expression ofPDGFR-βmRNA is exceeding low. Sorafenib acting on ripe pathological retinal neovascularization whichare rich in pericytes could be remarklier.