Abstract 3978: MicroRNA-378 exerts anti-fibrotic role by regulating hedgehog signaling in murine liver fibrosis
Authors: Hyun Jeongeun , Jung Youngmi 
Published: August 2015

Liver fibrosis that is a major characteristic of chronic liver diseases, including liver cancers, is regulated by the complex network of signaling pathways. Hedgehog (Hh) signaling is known to promote the hepatic fibrogenesis and modulate the cancer-favorable microenvironment. MicroRNAs (miRNAs), the endogenous short non-coding RNAs, negatively regulate the expression of their target genes, controlling a variety of cellular processes. The dysregulation of miRNAs has been involved in liver diseases, but little is known on their role in the liver fibrosis. Hence, we investigated the regulation of miRNAs in chronic liver disease in mice. MiRNA expression profiles were investigated in livers from healthy (corn-oil treated) and carbon tetrachloride (CCl4)-treated mice for 10 weeks. The regulatory mechanism of related miRNAs was further studied. Among liver-expressed miRNAs, three members of miR-378 family, including miR-378a-3p (0.395-fold), miR-378b (0.390-fold) and miR-378d (0.372-fold), were greatly downregulated in CCl4-treated mice compared to corn-oil-treated mice (p0.005). QRT-PCR analysis confirmed the lower expression of miR-378a-3p, -b and -d in the livers with CCl4 treatment and the activated LX2 cells, human hepatic stellate cell (HSC) line. Computational predictions revealed the binding of miR-378 (miR-378a-3p) with glioblastoma (Gli) 2 and/or Gli3, a transcriptional factor of Hh signaling, and luciferase assay proved that miR-378 directly targeted Gli3. The level of mRNA and protein of both Gli3 and Gli2 decreased in LX2 cell transfected with miR-378 mimic. As the expression of Glis was reduced, the mRNA expression of profibrotic genes, including vimentin, plasminogen activator inhibitor-1 and connective tissue growth factor, decreased, but the expression of glial fibrillary acidic proteinn, an inactivation marker of HSC, increased in miR-378 mimic-transfected LX2 cells. Inversely, treatment of GDC-0449, an inhibitor of Smoothened (Smo) which is the Hh receptorm, upregulated the expression of miR-378 family in LX2 cells, indicating that Smo suppressed the expression of miR-378, upregulating Gli3 in the activated HSCs. In addition, the expression of miR-378 family was significantly alleviated in the damaged livers of mice fed with methionine/choline-deficient and ethionine-supplemented diet for 4 weeks. Therefore, our results demonstrated that miR-378 family was most downregulated in the chronically damaged liver, suppressed the activation of HSCs by targeting Gli3 and its inhibitory action was regulated by Smo expression, suggesting that Hh-dependent regulation of miR-378 influenced the liver fibrosis in mice.

Citation Format: Jeongeun Hyun, Youngmi Jung. MicroRNA-378 exerts anti-fibrotic role by regulating hedgehog signaling in murine liver fibrosis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3978. doi:10.1158/1538-7445.AM2015-3978