Microrna-302b Mitigates Renal Fibrosis Via Inhibiting Tgf-Beta/Smad Pathway Activation

Renal fibrosis is one of the most significant pathological changes after ureteral obstruction. Transforming growth factor-beta (TGF-beta) signaling pathway plays essential roles in kidney fibrosis regulation. The aims of the present study were to investigate effects of microRNA-302b (miR-302b) on renal fibrosis, and interaction between miR-302b and TGF-beta signaling pathway in murine unilateral ureteral obstruction (UUO) model. Microarray dataset GSE42716 was downloaded by retrieving Gene Expression Omnibus database. In accordance with bioinformatics analysis results, miR-302b was significantly down-regulated in UUO mouse kidney tissue and TGF-beta 1-treated HK-2 cells. Masson's trichrome staining showed that miR-302b mimics decreased renal fibrosis induced by UUO. The increased mRNA expression of collagen I and alpha-smooth muscle actin (alpha-SMA) and decreased expression of E-cadherin were reversed by miR-302b mimics. In addition, miR-302b up-regulation also inhibited TGF-beta 1-induced epithelial mesenchymal transition (EMT) of HK-2 cells by restoring E-cadherin expression and decreasing alpha-SMA expression. miR-302b mimics suppressed both luciferase activity and protein expression of TGF-beta R2. However, miR-302b inhibitor increased TGF-beta R2 luciferase activity and protein expression. Meanwhile, miR-302b mimics inhibited TGF-beta R2 mRNA expression and decreased Smad2 and Smad3 phosphorylation in vivo and in vitro. Furthermore, over-expression of TGF-beta R2 restored the miR-302b-induced decrease of collagen I and alpha-SMA expression. In conclusion, this study demonstrated that miR-302b attenuated renal fibrosis by targeting TGF-beta R2 to suppress TGF-beta/Smad signaling activation. Our findings showed that elevating renal miR-302b levels may be a novel therapeutic strategy for preventing renal fibrosis.