The Mechanisms Underlying The Protective Effects Of Pedf In Early Stage Of Diabetic Retinopathy

Objective: Diabetic retinopathy is one of the complications of diabetes mellitus, which eventually lead to blindness. Therefore, the major concern has emerged about its early prevention and treatment. Angiogenesis is the main pathological alterations in DR and it has been suggested many factors were involved in this process. PEDF,Pigment epithelium-derived factor, a multifunctional secreted protein that has strong anti-angiogenic effects and it plays important role in the pathogenesis of DR. In the present study, we try to investigate the role of PEDF in early stage of DR in rats with type 1 diabetes.Method:8 weeks old male SD rats were used as animal model and were randomly divided into four groups: control groups(CON):rats got no treatments; diabetes mellitus group (DM):rats were Intraperitoneally injected with Streptozotocin (STZ, 65mg/kg body weight), diabetes treated with PEDF or saline groups(DM+PEDF and DM+NS): rats were get Intravitreal injection of 2ug/8ul PEDF or same volume of saline in right eye once per week one week after the DM model was set. Body weight and fasting blood glucose were measured once per week and rats were terminated 3 weeks after the DM was set. All the right eyes were collected and used for histopathological studies and alterations in ultrastructure were observed by Transmission electron microscopy (TEM). All data were presented as mean士SD and differences were calculated by one-way ANOVA. p<0.05was considered statistically different and was P<0.001 was significantly statistically different. Results:1 STZ induced type 1 diabetes mellitusTotal 28 rats out of 30 (93.3%)were found diabetic after intraperitoneally injected with STZ. And, there were 2 rats(7.1%)died in groups DM+PEDF and DM during the experiment.2 body weight and blood glucoseCompared with CON animals, rats in DM,DM+NS and DM+PEDF groups all had significantly increased fasting blood glucose levels. No differences in fasting blood glucose levels found between DM animals。DM rats had significantly decreased body weight when compared with age-matched normal controls. And this difference seems get more magnificent following the diabetes duration.3 3 weeks of diabetic courses caused no alterations in fundusCompared with CON animals, there were no pathological alterations found fundus in all DM animals. And all lens observed were transparent.4 ultrastructural alterations observed by TEM:Under TEM, structure of the retinal ganglion cells CON rats was clear and its organelles was intact. in both DM and DM+NS rats, there existed edema in retinal ganglion cells, mitochondrial get swollen and most of ridge were disappeared and part of the bilateral membrane were even found fusion. Rough endoplasmic reticulum was found enlarged in these animals. These pathological ultrastructural alterations can be partly ameliorated by PEDF injection.5 PEDF and VEGF expression in retinaBoth PEDF and VEGF were very low expressed in retina in both CON and DM animals, and there were no statistical differences found between CON and DM ,DM+NS animals. PEDF injection tends to increase PEDF and VEGF expression when compared with DM and DM+NS animals, but those changes did not reach statistical differnces. These results indicatied that 3 weeks of diabetic duration could not cause PEDF and VEGF alterations on protein level.6 PEDF-treatment may decrease ICAM-1 and MCP-1 expression in retina Both ICAM-1 and MCP-1 were very low expressed in retinal in CON rats. However, 3weeks of diabetic duration lead to significantly higher ICAM-1 and MCP-1 expression in both DM and DM+NS rats when compared with CON animals. Intravitreal injection of PEDF may effectively decrease ICAM-1 and MCP-1 expression in DM rats, indicating PEDF may partly protect retina from diabetic retinopathy by inhibiting inflammatory relative factors.7 PEDF treatment may increase ZO-1 and Akt expression in retina. In CON rats, ZO-1 protein mainly expressed in the inner nuclear layer cells and ganglion cells. ZO-1 expression was significantly reduced DM and DM+NS rats when compared with CON rats while PEDF injection may significantly increase ZO-1 protein expression in diabetic rats. Akt mainly expressed in the inner plexiform layer of the retina. Compared with CON animals, Akt expression was significantly decreased in DM rats, and this decrease can be prevented by PEDF but not saline treatment.Conclusion :1 no differences in PEDF and VEGF gene expression on protein level were found between diabetic and control rats in early phase of experimental diabetic retinopathy.2 there were pathological alterations in ultrastructue of retinal ganglion cell in early diabetic retinopathy. And these pathological changes can be partly ameliorated by PEDF treatment.3 ICAM-1 and MCP-1 levels increased significantly in retina of early diabetic retinopathy, and this effect can be blocked by PEDF injection..4 both ZO-1 and Akt protein levels were reduced in retina of diabetic animals,and PEDF may increase ZO-1 and Akt expression in diabetic animals.5 Results suggest that PEDF could prevent retinal ganglion cell damage and vascular hyperpermeability in early diabetic retinopathy by decreasing ICAM-1 and MCP-1 expression and increasing ZO-1 and Akt expression. PEDF may prevent the progression of early diabetic retinopathy.