LAUSR

We found that the expression of microRNA (miRNA)‐9a‐5p decreased in inflammatory bowel diseases (IBD; ulcerative colitis and Crohn's disease). Further, we revealed the effects and mechanisms of miRNA‐9a‐5p for regulating IBD progression. In C57BL/6N mice, IBD was induced with dextran sodium sulfate (DSS), and the effects of endogenous miRNA‐9a‐5p were mimicked/antagonized through intraperitoneal injection of miRNA‐9a‐5p agomir and antagomir. In animal experimentation, agomir could inhibit intestinal inflammation and tissue damage, and reduce the mucosal barrier permeability. Antagomir, on the other hand, could promote barrier damage, whose effect was associated with the M1 macrophage polarization. This study finds that miRNA‐9a‐5p targets NOX4 to suppress ROS production, which plays an important role in mucosal barrier damage in IBD.