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

Abstract

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±0.07),(-7.50±0.04),(+0.25±0.03) and (-7.50±0.02) D,the fasting glucose of the four groups were (5.3 ±0.1),(5.1 ±0.2),(19.7 ±0.4) and (18.5±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 ±5.57,118.24±2.59,155.60±9.70 and 135.15±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± 8.35,149.54±6.20,127.71±2.45 and 137.53±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. Key words: Diabetic retinopathy; High myopia; Vascular endothelial growth factor; Pigment epithelial derived factor