Liver-specific deletion of microRNA-34a alleviates ductular reaction and liver fibrosis during experimental cholestasis.

Primary sclerosing cholangitis (PSC) is a chronic liver disease characterized by inflammatory responses and fibrotic scar formation leading to cholestasis. Ductular reaction and liver fibrosis are typical liver changes seen in human PSC and cholestasis patients. The current study aimed to clarify the role of liver-specific microRNA-34a in the cholestasis-associated ductular reaction and liver fibrosis. We demonstrated that miR-34a expression was significantly increased in human PSC livers along with the enhanced ductular reaction, cellular senescence, and liver fibrosis. A liver-specific miR-34a knockout mouse was established by crossing floxed miR-34a mice with albumin-promoter-driven Cre mice. Bile duct ligation (BDL) induced liver injury characterized by necrosis, fibrosis, and immune cell infiltration. In contrast, liver-specific miR-34a knockout in BDL mice resulted in decreased biliary ductular pathology associated with the reduced cholangiocyte senescence and fibrotic responses. The miR-34a-mediated ductular reactions may be functioning through Sirt-1-mediated senescence and fibrosis. The hepatocyte-derived conditioned medium promoted LPS-induced fibrotic responses and senescence in cholangiocytes, and miR-34a inhibitor suppressed these effects, further supporting the involvement of paracrine regulation. In conclusion, we demonstrated that liver-specific miR-34a plays an important role in ductular reaction and fibrotic responses in a BDL mouse model of cholestatic liver disease.

miR-34a regulates macrophage-associated inflammation and angiogenesis in alcohol-induced liver injury.

BACKGROUND: Alcohol-associated liver disease (ALD) is a syndrome of progressive inflammatory liver injury and vascular remodeling associated with long-term heavy intake of ethanol. Elevated miR-34a expression, macrophage activation, and liver angiogenesis in ALD and their correlation with the degree of inflammation and fibrosis have been reported. The current study aims to characterize the functional role of miR-34a-regulated macrophage- associated angiogenesis during ALD. METHODS RESULTS: We identified that knockout of miR-34a in 5 weeks of ethanol-fed mice significantly decreased the total liver histopathology score and miR-34a expression, along with the inhibited liver inflammation and angiogenesis by reduced macrophage infiltration and CD31/VEGF-A expression. Treatment of murine macrophages (RAW 264.7) with lipopolysaccharide (20 ng/mL) for 24 h significantly increased miR-34a expression, along with the enhanced M1/M2 phenotype changes and reduced Sirt1 expression. Silencing of miR-34a significantly increased oxygen consumption rate (OCR) in ethanol treated macrophages, and decreased lipopolysaccharide-induced activation of M1 phenotypes in cultured macrophages by upregulation of Sirt1. Furthermore, the expressions of miR-34a and its target Sirt1, macrophage polarization, and angiogenic phenotypes were significantly altered in isolated macrophages from ethanol-fed mouse liver specimens compared to controls. TLR4/miR-34a knockout mice and miR-34a Morpho/AS treated mice displayed less sensitivity to alcohol-associated injury, along with the enhanced Sirt1 and M2 markers in isolated macrophages, as well as reduced angiogenesis and hepatic expressions of inflammation markers MPO, LY6G, CXCL1, and CXCL2. CONCLUSION: Our results show that miR-34a-mediated Sirt1 signaling in macrophages is essential for steatohepatitis and angiogenesis during alcohol-induced liver injury. These findings provide new insight into the function of microRNA-regulated liver inflammation and angiogenesis and the implications for reversing steatohepatitis with potential therapeutic benefits in human alcohol-associated liver diseases.