As a specific microvascular complication of diabetes, diabetic retinopathy (DR) causes severe visual impairment in patients with diabetes. The expression of microRNA-126 (miRNA/miR-126) has previously been found to be significantly decreased in the serum of patients with DR. In the present study, the functions of miR-126 and its mechanisms of action in experimental diabetic retinopathy were examined in rats with streptozotocin (STZ)-induced diabetes and in high glucose (HG)-induced human retinal capillary endothelial cells (HRCECs). In vivo , diabetic rat models were established and the rats were intravitreally injected with lentivirus expressing rno-miR-126 (lenti-miR-126) or negative control (lenti-NC). RT-qPCR was used to determine the miR-126 level in the serum and retina. Paraffin sections and retinal vasculature were used to determine the extent of retinopathy. The protein content of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in the retina was used as an auxiliary measurement of retinopathy. Western blot analysis and immunofluorescence staining were used to measure the expression of polo-like kinase 4 (PLK4) in rat retinal tissue. In vitro , the cells were transfected with miR-126 inhibitor or mimic and treated with the PLK4 inhibitor, CFI-400945 fumarate. RT-qPCR and western blot analysis were used to detect the miR-126 level and PLK4 expression. Cell proliferation and migration were measured by EdU and Transwell assays. The diabetic rats were found to exhibit downregulated serum and retinal miR-126 levels compared with the non-diabetic rats. The intravitreal delivery of miR-126 alleviated retinopathy and reduced the diabetes-induced upregulation of PLK4 in retinal tissues. Luciferase reporter assays confirmed that PLK4 mRNA was the target of miR-126. In HG-induced HRCECs, transfection with miR-126 mimic increased the miR-126 level, whereas it downregulated that of its downstream target, PLK4, which was opposite to the effects exerted by the miR-126 inhibitor. Furthermore, miR-126 mimic and CFI-400945 fumarate reduced the HG-induced upregulation of PLK4 expression, as well as cell proliferation and migration. On the whole, the findings of the present study demonstrate that miR-126 reduces experimental diabetic retinopathy and suppresses endothelial cell proliferation and migration by targeting PLK4. Thus, miR-126 and CFI-400945 fumarate may be therapeutic targets for DR.

Background: To investigate the expression and significance of mechanistic target of rapamycin complex 1(mTORC1) in diabetic retinopathy (DR), and to find new targets and new methods for the treatment of DR. Methods: A DR rat model was prepared by general feeding combined with intraperitoneal injection of 10% streptozotocin (60 mg/kg). The rats were randomly divided into a control group (NDM group) and a diabetes group (DM group). Three months later, the degrees of retinopathy was determined using hematoxylin and eosin staining, and the levels of p-S6, VEGF, and PEDF proteins were detected by immunohistochemistry and western blotting. Human retinal capillary endothelial cells (HRCECs) were cultured in high glucose (HG) conditions, then treated with rapamycin or transfected with siTSC1.The protein levels of p-S6 were assessed by western blotting. The 5-ethynyl-2′deoxyuridine assay was used to detect cell proliferation, and the Transwell assay was used to detect cell migration. Results: A DM rat model was successfully developed. The expressions of p-S6 and VEGF proteins were significantly increased in the DM group (p < 0.05), and the expression of PEDF protein was significantly decreased compared with the NDM group (p < 0.05). In vitro, the p-S6 protein, as well as cell proliferation and migration, in HG induced HRCECs were increased (p < 0.05) compared with the control (normal glucose) group (p < 0.05). After transfection with siTSC1 to activate mTORC1, the expression of p-S6, as well as cell proliferation and migration, were increased. In contrast, rapamycin decreased p-S6 expression, as well as proliferation and migration, in HG induced HRCECs compared to the control group (p < 0.05). Conclusion: mTORC1 plays an important role in DR. After activation, mTORC1 induced expression of the p-S6 protein, regulated the expressions of VEGF and PEDF proteins, and changed the proliferation and migration of endothelial cells. The mTORC1 can therefore be used as a new target,as well as in the treatment of DR.

Background: To investigate the expression and significance of mechanistic target of rapamycin complex 1(mTORC1) in diabetic retinopathy(DR), and to find new targets and new methods for the treatment of DR.Methods: A DR rat model was prepared by general feeding combined with intraperitoneal injection of 10% streptozotocin (60 mg/kg). The rats were randomly divided into a control group (NDM group) and diabetes group (DM group).Three months later,the degrees of retinopathy were determined using hematoxylin and eosin staining,and the levels of p-S6, VEGF, and PEDF proteins were detected by immunohistochemistry and western blotting. Human retinal capillary endothelial cells (HRCECs) were cultured in high glucose conditions,then treated with rapamycin or transfected with siTSC1.The protein levels of p-S6 were assessed by western blotting. The 5-ethynyl-2´-deoxyuridine assay was used to detect cell proliferation, and the Transwell assay was used to detect cell migration.Results: A DM rat model was successfully developed. The expressions of p-S6 and VEGF proteins were significantly increased in the DM group (p < 0.05), and the expression of PEDF protein was significantly decreased compared with the control group (p < 0.05). In vitro,the p-S6 protein in high glucose(HG) induced HRCECs was increased compared with the normal control (p < 0.05), and cell proliferation and migration were increased compared with the normal glucose(NG) group (p < 0.05). After transfection with siTSC1 to activate mTORC1,the expression of p-S6 was increased,as well as cell proliferation and migration.In contrast rapamycin decreased p-S6 expression in HG induced HRCECs, as well as decrased proliferation and migration (p < 0.05).Conclusion: The mTORC1 played an important role in DR. After activation, mTORC1 induced expression of the p-S6 protein, regulated the expressions of VEGF and PEDF proteins, and changed the proliferation and migration of endothelial cells.The mTORC1 can therefore be used as a new target,as well as in the treatment of DR.

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