MiR-135a regulates renal fibrosis in rats with diabetic kidney disease through the Notch pathway

L.-Y. Zhang, Y. Wang, Y.-R. Yang, J.-J. Shao, B. Liang

Department of Nephrology, The Second Hospital of Shanxi Medical University, Taiyuan, China. tyliangbin@163.com

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• Nephrology

OBJECTIVE: To explore the influence of micro ribonucleic acid (miR)-135a on the renal fibrosis in rats with diabetic kidney disease (DKD) through the Notch signaling pathway.

MATERIALS AND METHODS: A total of 30 male Wistar rats weighing 200-220 g were selected and randomly divided into Control group (n=10), diabetes mellitus (DM) group (n=10), and miR-13a inhibitor group (n=10). Streptozotocin (STZ) was intraperitoneally injected daily to establish the DM model in rats of both DM group and miR-135a group, while normal saline was given daily through intraperitoneal injection in rats of Control group. After 4 weeks, the rats in miR-135a inhibitor group were intraperitoneally injected with miR-135a inhibitor, and those in Control and DM groups were administrated with an equal amount of normal saline. Changes in the blood glucose (BG), glycated hemoglobin (GHb), serum creatinine (Scr), triglyceride (TG), and total cholesterol (TC) of rats were evaluated, and the pathological changes in the renal tissues of DM rats were observed via hematoxylin-eosin (HE) staining. Sirius red staining was performed to observe the changes in collagen fibers in the kidney of all groups of rats. The expressions of Notch and Hes1 in the renal tissues of rats in each group were detected using immunohistochemistry. Immunofluorescence assay was employed to detect the positive expression of Notch in the renal tissues of rats. The mRNA expressions of Notch and miR-135a were detected via quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR). Finally, Western blotting was conducted to detect the protein expressions of Notch, Notch intracellular domain (NICD) and Hes1.

RESULTS: Compared with Control group, rats in DM group had substantially raised levels of BG, GHb, Scr, TG, and TC (p<0.05). HE staining showed that the rats in Control group had renal tubular cells with normal morphology and well-defined structure, while those in DM group exhibited evident cavitation in the renal tubular epithelium. Sirius red staining results manifested that the red collagen fibers were evenly distributed with light staining in the glomeruli and renal tubules of rats in Control group. In contrast, the collagen fibers of the glomeruli and renal tubules of rats in DM group exhibited deep and evident red staining. Moreover, compared with DM group, rats in miR-135a inhibitor group had notably faded red staining in the glomeruli and renal tubules of rats, evenly distributed collagen and remarkably decreased fibrotic nodules. According to immunohistochemistry detection results, the protein levels of Notch and Hes1 in the renal tubulointerstitial cells and renal tubular epithelial cells of rats in DM group were markedly higher than those in Control group. Compared with those in DM group, their protein levels were remarkably lowered in miR-135a inhibitor group (p<0.05). Immunofluorescence assay results revealed that the protein level of Notch in the renal tissues of rats in DM group was considerably higher than that in Control group (p<0.05), while its protein level in miR-135a inhibitor group was significantly lower than that in DM group. According to qRT-PCR results, compared with those in Control group, mRNA expressions of Notch mRNA and miR-135a in the rat kidney tissues were substantially raised in DM group (p<0.05), and they were notably lowered in miR-13a inhibitor group compared with those in DM group (p<0.05). Finally, Western blotting results manifested that the protein levels of Notch, NIC, and Hes1 in the renal tissues of rats in DM group were considerably higher than those in Control group (p<0.05), and that their protein expression levels in miR-135a inhibitor group were markedly lower than those in DM group (p<0.05).

CONCLUSIONS: Inhibition of miR-135a can reduce the renal fibrosis in DKD rats through the Notch pathway.

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