| ObjectiveTo elevate the efficacy of intravitreal Bevacizumab injection on early diabetic retinopathy(DR) of rats, to explore the safe dose of Bevacizumab and appropriate repeated intravitreal injection interval.Method1 Diabetic mellitus(DM) rats models constructing:80 healthy adult Sprague Dawley rats were chosen and randomly divided into normal group and diabetic group which were constructed for diabetic models by streptozotocin (STZ) 45 mg/kg tails intravenous injection.2 Proving DM rats with early DR:Evans blue(EB) angiography was used to ensure that the diabetic rats had early diabetic retinopathy in the 10th week after successful model making.2 normal rats and 2 DM rats reiceived (EB) angiography.3 Intravitreal Bevacizumab injection:after proving DM rats had early diabetic retinopathy, the diabetic model were divided into three groups randomly including control model group (DR group),high-dose treatment group(H group) and Low-dose treatment group(L group).After that, Bevacizumab was injected into the vitreous in the treatment group,the dose was 2.5mg/ml×4μl and 1.25 mg/ml×4μl,respectively.4 2 weeks,4weeks,6 weeks after injection,the rats were executed and eyes were enucleated. The expression of VEGF in retinas was assessed by Immunohistochemistry assay. EB perfusion method was used to assess the function of BRB. EB angiography was used to assess the capillary vessel pattern after Bevacizumab injection.Result165 rats were constructed for diabetic model successfully,the other 2 were divided into normal group, success rate was 97%.2 EB angiography:N group:The blood vessels travel generally normal, no pathological changes were visible. Diabetic rats:the density of microvascular become higher, vessels run tortuous; Occasionally,EB leaked from the branch of retinal vessels, no microaneurysms was visible.ALL these reveal that the diabetic rats had early DR.3 Total 50 DR rats received intravitreal Bevacizumab injection,2 rats had vitreous hemorrhage,all rats had cataract with time going.4 Immunohistochemistry assay:VEGF was expressed in the retina of all rats, but the expression of the H group and Lgroup is weaker than DR group while stronger than N group. EB perfusion method:2 weeks after the treatment, EB leakage of treatment groups was lower than DR group and higher than N group (P=0.000),there were no statistically significant differences between the H group and L group (P=0.364);4 weeks and 8 weeks after the treatment, EB leakage of treatment groups was lower than DR group and higher than N group (P=0.000), there were statistically significant differences between the H group and L group (P=0.035, 0.031).EB angiography:DR group:2 weeks after the treatment, the density of microvascular increase; vessels run tortuous; EB leaked from the branch of retinal vessels, some microaneurysms were visible but neovascularization was unvisible.4 and 8 weeks after the treatment, retinal vasculars irregularly expanded and run tortuosity; there were microaneurysms and no perfusion zone; there was large-scale EB leakage in the peripheral retina. Retinal vascular density was significantly higher than the N group and lower than DR group; retinal vascular tortuosity was not obvious, and there were no microaneurysms and no-perfusion zone in treatment group; Occasionally, there were retina vascular leakage in L group, but no in H group.Conclusion(1) EB perfusion method is an effective mean of quantitative detecting BRB of the DR rats by measuring the EB content of retina.(2)Intravitreal injection of Bevacizumab at approprite dose is effective in preventing rats DR progression,it is possible to delay the occurrence of proliferative DR, The efficent of 2.5mg/0.1ml is better than 1.25mg/0.1ml.(3)The effet of Intravitreal Bevacizumab injection is dose-related,at least 8 weeks,the effect is stable. |
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