Protective Effect And Mechanism Of Umbilical Cord Mesenchymal Stem Cells On Retinopathy In Mice With Type 1 Diabetes Mellitus

Objective Retinal neovascularization is an important cause of visual loss for diabetic retinopathy(DR)patients.Using umbilical cord mesenchymal stem cells(h UCMSCs)for the treatment of DR has become a hot topic in recent years,but its mechanism is still unclear.By using the therapy of h UCMSCs in NOD mice with T1 DM,we investigate whether h UCMSCs can play a role in the treatment of DR by affecting the Notch signaling pathway,hairy and enhancer of split related 1(HESR1)and vascular endothelial growth factor receptor-2(VEGFR-2).Methods NOD mice with two consecutive random blood glucose levels greater than 16.6mmol/L were diagnosed with type 1 diabetes.Type 1 diabetic mice were randomly divided into the following groups,and given the corresponding interventions: no intervention was given to diabetic group;insulin glargine was given to insulin group according to blood glucose level;the stem cell group was treated with injection of h UCMSCs,and insulin glargine was given according to the level of blood glucose.NOD mice without type 1 diabetes were selected as normal control group after 8 weeks of detection.After 8 weeks of regularly detection of random blood glucose,all mice was sacrificed and their eyes were collected.Under the optical microscope,the structure of each layer of the retina was observed and the number of vascular endothelial nuclei that beyond the internal limiting membrane of the retina was counted in sections with HE staining.The expression of retinal VEGFR-2 and HESR1 m RNA were detected by real-time quantitative PCR.The expression of retinal VEGFR-2 and Notch-1 protein was detected using Western blot.Results In the normal control group,the mice were generally in good condition,and the skin was not damaged.The other three groups of mice showed gradual decrease in activity,damaged hair and increased food consumption after onset.There was no significant difference in the levels of random blood glucose between the stem cell group and insulin group(P>0.05).In the stem cell group,the insulin injection amount began to decrease after the day 14 and maintained at a low level,which was significantly lower than that of the insulin group(P < 0.05).The weight of the mice of the normal control group showed an increasing trend in the experiment.The weight of the insulin group mice had no obvious fluctuation from the beginning to the end of the experiment.The weight of the mice in the diabetic group decreased gradually after the onset of the disease.The weight of the mice in the stem cell group decreased gradually in the early stage of the experiment,and began to rise after day 35,and could rise to the similar level as the normal control group.In the normal control group,the structure of each layer of the retina was in good order.In the diabetic group,the stem cell group and the insulin group,the structure of the retina were in disorder.There was a significant difference in the number of endothelial nuclei that beyond the internal limiting membrane of the retina between the four groups(F=557.2,P<0.05).The number was significantly lower in stem cell group than that in insulin group(P < 0.05).There were significant differences in the expression of Notch-1 protein,HESR1 m RNA,VEGFR-2 m RNA and protein in the retina of the four groups(F=562.3,376.2,155.1,197.8,all P<0.05).Compared with normal control group,the expression of Notch-1 protein and HESR1 m RNA were statistically decreased,the expression of VEGFR2 m RNA and protein were statistically increased in diabetic group(all P < 0.05).Compared with diabetic group,the expression of Notch-1 protein and HESR1 m RNA were statistically increased,the expression of VEGFR2 m RNA and protein were statistically decreased in stem cell group and insulin group(all P < 0.05).Compared with insulin group,the expression of Notch-1 protein and HESR1 m RNA were statistically increased,the expression of VEGFR2 m RNA and protein were statistically decreased in stem cell group(all P < 0.05).Conclusion The application of caudal vein injection of h UCMSCs can significantly ameliorate the hyperglycemic state,reduce the number of endothelial nuclei that beyond the internal limiting membrane of the retina and stabilize the structure of retina in experimental diabetic mice.The mechanism of its treatment of diabetic retinopathy may be inhibiting retinal neovascularization by upregulating Notch pathway and downstream HESR1 expression,and downregulating VEGFR-2 expression.