miR-141 regulates TGF-β1-induced epithelial-mesenchymal transition through repression of HIPK2 expression in renal tubular epithelial cells

Epithelial-mesenchymal transition (EMT) plays a critical role in embryonic development, wound healing, tissue regeneration, cancer progression and organ fibrosis. The proximal tubular epithelial cells undergo EMT, resulting in matrix-producing fibroblasts and thereby contribute to the pathogenesis of renal fibrosis. The profibrotic cytokine,TGF-beta, is now recognized as the main pathogenic driver that has been shown to induce EMT in tubular epithelial cells. Increasing evidence indicate that HIPK2 dysfunction may play a role in fibroblasts behavior, and therefore, HIPK2 may be considered as a novel potential target for anti-fibrosis therapy. Recently, members of the miR-200 family (miR-200a, b and c and miR-141) have been shown to inhibit EMT. However, the steps of the multifactorial renal fibrosis progression that these miRNAs regulate, particularly miR-141, are unclear. To study the functional importance of miR-141 in EMT, a well-established in vitro EMT assay was used to demonstrate renal tubulointerstitial fibrosis; transforming growth factor-beta 1-induced EMT in HK-2 cells. Overexpression of miR-141 in HK-2 cells, either with or without TGF-beta 1 treatment, hindered EMT by enhancing E-cadherin and decreasing vimentin and fibroblast-specific protein 1 expression. miR-141 expression was repressed during EMT in a dose- and time-dependent manner through upregulation of HIPK2 expression. Ectopic expression of HIPK2 promoted, EMT by decreasing E-cadherin. Furthermore, co-transfection of miR-141 with the HIPK2 ORF clone partially inhibited EMT by restoring E-cadherin expression. miR-141 downregulated the expression of HIPK2 via direct interaction with the 3'-untranslated region of HIPK2. Taken together, these findings aid in the understanding of the role and mechanism of miR-141 in regulating renal fibrosis via the TGF-beta 1/miR-141/HIPK2/EMT axis, and miR-141 may represent novel biomarkers and therapeutic targets in the treatment of renal fibrosis.