高度近视对糖尿病豚鼠视网膜血管内皮生长因子和色素上皮衍生因子表达的影响

背景 研究发现糖尿病合并高度近视患者较少发生糖尿病视网膜病变（DR）,高度近视对DR的发生和发展可能具有保护作用.DR的主要病理基础是新生血管的形成,而血管内皮生长因子（VEGF）和色素上皮衍生因子（PEDF）在DR的发生和发展过程中具有重要作用. 目的 观察高度近视合并糖尿病豚鼠视网膜中VEGF和PEDF表达的变化,探讨高度近视对DR的影响.方法 将出生3d的豚鼠48只采用随机数字表法随机分为正常对照组、高度近视组、糖尿病组和糖尿病合并高度近视组,每组12只.高度近视组豚鼠用半透明眼罩行右眼遮盖,构建高度近视动物模型;采用60 mg/kg的链脲佐菌素（STZ）腹腔内注射4次,每3天1次,制作糖尿病豚鼠模型;糖尿病合并高度近视组豚鼠采用半透明眼罩联合STZ制作糖尿病合并高度近视模型.造模成功后行常规苏木精-伊红染色观察视网膜结构,免疫组织化学染色检测视网膜中VEGF和PEDF的表达情况,应用Biosens数字成像分析系统分析阳性反应部位的平均吸光度（A）值. 结果 正常对照组、高度近视组、糖尿病组和糖尿病合并高度近视组的屈光度分别为（＋0.25±177;0.07）、（-7.50±177;0.04）、（＋0.25±177;0.03）和（-7.50±177;0.02）D;空腹血糖分别为（5.3±177;0.1）、（5.1±177;0.2）、（19.7±177;0.4）和（18.5±177;0.3）mmol/L.各组豚鼠均造模成功.与正常对照组相比,高度近视组视网膜组织变薄,神经节细胞数目减少;糖尿病组视网膜组织结构疏松、肿胀;糖尿病合并高度近视组视网膜组织变薄,结构肿胀.正常对照组、高度近视组、糖尿病组和糖尿病合并高度近视组VEGF阳性反应部位平均A值分别为128.61 ±177;5.57、118.24±177;2.59、155.60±177;9.70和135.15±177;5.22,各组间总体比较差异有统计学意义（F=17.365,P=0.032）,其中糖尿病合并高度近视组豚鼠视网膜中VEGF表达水平（A值）明显低于糖尿病组,差异有统计学意义（t=5.210,P＜0.05）;PEDF阳性反应部位平均A值分别为145.57±177;8.35、149.54±177;6.20、127.71 ±177;2.45和1 37.53±177;7.38,各组间总体比较差异有统计学意义（F=19.210,P=0.019）,其中糖尿病合并高度近视组豚鼠视网膜中PEDF水平明显高于糖尿病组,差异有统计学意义（t=4.521,P＜0.05）.结论 高度近视合并糖尿病的豚鼠视网膜中VEGF表达量下调,而PEDF表达上调,这可能是高度近视眼不易发生DR的主要机制.

Influence of high myopia on expression of vascular endothelial growth factor and pigment epithelial derived factor in retina in diabetic guinea pig

Background Diabetic retinopathy （DR） seems to be rarely found in high myopia patients with diabetes mellitus.This finding suggests that myopia,especially high myopia,plays a protective effect against DR.It is well-known that the primary pathological base of DR is neovescularization,and the changes of vascular endothelial growth factor （VEGF） and pigment epithelium derived factor （PEDF） are associated with DR.Objective This study was to analyze the expressions of VEGF and PEDF in retina and investigate the influence of high myopia on the pathogenesis of DR.Methods Forty-eight 3-day-old guinea pigs were randomly divided into normal control group,high myopia group,diabetic group and diabetes with high myopia group.Translucent goggles were worn in the right eyes of the guinea pigs for consecutive 8 weeks to induce high myopia,and streptozocin （STZ） was intraperitoneally injected at a dose of 60 mg/kg for four times,every three days for once,to establish diabetic models in the corresponding groups.Twelve weeks after modeling,the animals were sacrificed by excessive anesthesia,and the retinas were isolated for the histopathological examination.Expressions of VEGF and PEDF in the retinas were detected by immunohistochemistry.The use and care of experimental animals conformed to Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.Results The diopter of the normal control group,high myopia group,diabetic group and diabetes with high myopia group were （＋0.25±177;0.07）,（-7.50±177;0.04）,（＋0.25±177;0.03） and （-7.50±177;0.02） D,the fasting glucose of the four groups were （5.3 ±177;0.1）,（5.1 ±177;0.2）,（19.7 ±177;0.4） and （18.5±177;0.3）mmol/L,respectively.Compared with the normal control group,the retinas of high myopia group were thin,and the ganglion cells were less.The retinas of diabetic group were loose and oedematous.The retinas of diabetes with high myopia group were thin and oedematous.The expressing level of VEGF in retinas （absorbance value,A） were 128.61 ±177;5.57,118.24±177;2.59,155.60±177;9.70 and 135.15±177;5.22 in the normal control group,high myopia group,diabetic group and diabetes with high myopia group,respectively,showing a significant difference among the groups （F=17.365,P=0.032）,and the VEGF level was significantly lower in the diabetes with high myopia group than that of the diabetic group （t =5.210,P〈0.05）.The expressing level of PEDF in retinas （A value） were 145.57±177; 8.35,149.54±177;6.20,127.71±177;2.45 and 137.53±177;7.38,in the normal control group,high myopia group,diabetic group and diabetes with high myopia group,respectively,with a statistically significant difference among the four groups （F =19.210,P =0.019）,and the PEDF level was significantly higher in the diabetes with high myopia group than that of the diabetic group （t=4.521,P〈0.05）.Conclusions The expression of VEGF is downregulated and PEDF is upregulated in the retinas of diabetes with high myopia guinea pigs,which may be an accountable mechanism for the low incidence of DR in high myopia eyes.