Renal interstitial fibrosis (RIF) is characterized by excessive extracellular matrix deposition and involves epithelial-mesenchymal transition (EMT). The lncRNA taurine-upregulated gene 1 (TUG1) participates in EMT in several cancers; however, the effect and underlying mechanism of TUG1 in RIF-related EMT remain unclear. Here, we explored the mechanisms by which TUG1 modulates RIF. An in vivo model of renal fibrosis was established by unilateral ureteral obstruction in Balb/c mice. Human renal proximal tubular epithelial (HK-2) cells treated with transforming growth factor (TGF)-β1 were used to induce the in vitro model. Morphological changes and TUG1 expression were assessed. HK-2 cells were transfected with siRNA to silence TUG1. Western blot analysis, immunofluorescence staining, cell proliferation, and migration assays were performed to examine TGF-β1-induced changes in EMT markers and EMT-like cell behaviors. TUG1 and β-catenin (CTNNB1) levels were significantly upregulated, whereas miR-141-3p was significantly downregulated, during EMT in vitro and in vivo. TUG1 knockdown or miR-141-3p overexpression supported the epithelioid morphology of HK-2 cells while enhancing the downregulation of E-cadherin and upregulation of vimentin, α-smooth muscle actin, and β-catenin levels in TGF-β1-treated HK-2 cells. TUG1 knockdown promoted the proliferation and decreased the migration of HK-2 cells and enhanced the downregulation of miR-141-3p levels in TGF-β1-treated HK-2 cells. TUG1 directly targeted miR-141-3p, and miR-141-3p was directly bound to CTNNB1. Downregulation of miR-141-3p inhibited TUG1 silencing-induced suppression of EMT. In conclusion, TUG1 promotes EMT in TGF-β1-induced HK-2 cells via upregulation of β-catenin levels by sponging miR-141-3p, suggesting a novel therapeutic candidate for RIF.
Keywords: epithelial-mesenchymal transition; long noncoding RNA taurine upregulated 1; miR-141-3p; renal interstitial fibrosis; β-catenin.