1α,25-Dihydroxyvitamin D3 prevents the differentiation of human lung fibroblasts via microRNA-27b targeting the vitamin D receptor

Pulmonary fibroblasts have key roles in the formation and maintenance of lung structure and function, and are involved in tissue repair and remodeling. Transforming growth factor-beta 1 (TGF-beta 1) induces differentiation of fibroblasts into myofibroblasts, the key effector cells in fibrotic states, which are characterized by the expression of a-smooth muscle actin (alpha-SMA) markers. 1 alpha,25-Dihydroxyvitamin D-3 [1,25(OH)(2)D-3] has been implicated in regulating differentiation, and the vitamin D receptor (VDR) may be a regulator of TGF-beta signaling. In addition, there is presently only limited information regarding microRNA (miRNA) regulation of lung fibroblast differentiation. To determine the role of 1,25(OH)(2)D-3 in regulating the differentiation of fibroblasts induced by TGF-beta 1 and the functional importance of miR-27b, cell culture systems, cell transfection and the 3' untranslated region (3'UTR) luciferase assay were employed. 1,25(OH)(2)D-3 inhibited differentiation and downregulated miR-27b expression in human lung fibroblasts induced by TGF-beta 1. In addition, human lung fibroblasts were transfected with miR-27b mimic or miR-27b inhibitor, and demonstrated that the overexpression of miR-27b decreased the VDR protein expression and increased the expression of a-SMA, while reducing levels of miR-27b had opposing effects. Finally, the luciferase reporter assays were performed to confirm that miR-27b directly targeted VDR 3'UTR. Taken together, these results suggest that 1,25(OH)(2)D-3 inhibits lung fibroblast differentiation induced by TGF-beta 1 via miR-27b targeting VDR 3'UTR, which may be used as a novel treatment strategy in differentiation pathways.