RESUMO
As a specific microvascular complication of diabetes, diabetic retinopathy (DR) causes severe visual impairment in patients with diabetes. The expression of microRNA126 (miRNA/miR126) has previously been found to be significantly decreased in the serum of patients with DR. In the present study, the functions of miR126 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 rnomiR126 (lentimiR126) or negative control (lentiNC). RTqPCR was used to determine the miR126 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 epitheliumderived 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 pololike kinase 4 (PLK4) in rat retinal tissue. In vitro, the cells were transfected with miR126 inhibitor or mimic and treated with the PLK4 inhibitor, CFI400945 fumarate. RTqPCR and western blot analysis were used to detect the miR126 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 miR126 levels compared with the nondiabetic rats. The intravitreal delivery of miR126 alleviated retinopathy and reduced the diabetesinduced upregulation of PLK4 in retinal tissues. Luciferase reporter assays confirmed that PLK4 mRNA was the target of miR126. In HGinduced HRCECs, transfection with miR126 mimic increased the miR126 level, whereas it downregulated that of its downstream target, PLK4, which was opposite to the effects exerted by the miR126 inhibitor. Furthermore, miR126 mimic and CFI400945 fumarate reduced the HGinduced upregulation of PLK4 expression, as well as cell proliferation and migration. On the whole, the findings of the present study demonstrate that miR126 reduces experimental diabetic retinopathy and suppresses endothelial cell proliferation and migration by targeting PLK4. Thus, miR126 and CFI400945 fumarate may be therapeutic targets for DR.