XIST/miR-139 axis regulates bleomycin (BLM)-induced extracellular matrix (ECM) and pulmonary fibrosis through β-catenin.

Pulmonary fibrosis (PF), characterized by the destruction of lung tissue architecture and the abnormal deposition of extracellular matrix (ECM) proteins, currently has no satisfactory treatment. In the present study, we investigated the hypothesis that XIST play a promotive role in bleomycin (BLM)-induced ECM and pulmonary fibrosis; XIST exerts its effect through miR-139 regulation. XIST expression was upregulated in lung tissues derived from BLM-induced mouse model of PF, and was positively correlated with β-catenin and ECM protein levels, respectively. LV-sh-XIST-induced XIST knockdown led to decreased PF, reduced β-catenin and ECM protein levels in lung tissues. XIST knockdown suppressed the proliferation of IMR-90 (human fibroblast) and murine lung fibroblasts (MLFCs) and ECM protein expression. Moreover, miR-139 could directly bind to XIST and the 3'UTR of β-catenin; XIST competed with β-catenin for miR-139 binding both in IMR-90 and MLFCs. In MLFCs, miR-139 inversely regulated XIST, and could partially reverse the effect of XIST on β-catenin and ECM proteins. In lung tissues of PF mice, miR-139 expression was downregulated, whereas β-catenin expression was upregulated. In conclusion, XIST exerts positive effects on BLM-induced PF through inhibiting miR-139 to promote human/mouse fibroblast proliferation and ECM proteins.