MicroRNA-31 is a positive modulator of endothelial-mesenchymal transition and associated secretory phenotype induced by TGF-β

Transforming growth factor- (TGF-) plays central roles in endothelial-mesenchymal transition (EndMT) involved in development and pathogenesis. Although EndMT and epithelial-mesenchymal transition are similar processes, roles of microRNAs in EndMT are largely unknown. Here, we report that constitutively active microRNA-31 (miR-31) is a positive regulator of TGF--induced EndMT. Although the expression is not induced by TGF-, miR-31 is required for induction of mesenchymal genes including -SMA, actin reorganization and MRTF-A activation during EndMT. We identified VAV3, a regulator of actin remodeling and MRTF-A activity, as a miR-31 target. Global transcriptome analysis further showed that miR-31 positively regulates EndMT-associated unique secretory phenotype (EndMT-SP) characterized by induction of multiple inflammatory chemokines and cytokines including CCL17, CX3CL1, CXCL16, IL-6 and Angptl2. As a mechanism for this phenomenon, TGF- and miR-31 suppress Stk40, a negative regulator of NF-B pathway. Interestingly, TGF- induces alternative polyadenylation (APA)-coupled miR-31-dependent Stk40 suppression without concomitant miR-31 induction, and APA-mediated exclusion of internal poly(A) sequence in Stk40 3UTR enhances target efficiency of Stk40. Finally, miR-31 functions as a molecular hub to integrate TGF- and TNF- signaling to enhance EndMT. These data confirm that constitutively active microRNAs, as well as inducible microRNAs, serve as phenotypic modifiers interconnected with transcriptome dynamics during EndMT.