MicroRNA-29a Alleviates Bile Duct Ligation Exacerbation of Hepatic Fibrosis in Mice through Epigenetic Control of Methyltransferases.

Ya-Ling Yang,Ying-Hsien Huang,Feng-Sheng Wang,Mao-Meng Tiao,Sung-Chou Li

doi:10.3390/ijms18010192

Abstract

MicroRNA-29 (miR-29) is found to modulate hepatic stellate cells’ (HSCs) activation and, thereby, reduces liver fibrosis pathogenesis. Histone methyltransferase regulation of epigenetic reactions reportedly participates in hepatic fibrosis. This study is undertaken to investigate the miR-29a regulation of the methyltransferase signaling and epigenetic program in hepatic fibrosis progression. miR-29a transgenic mice (miR-29aTg mice) and wild-type littermates were subjected to bile duct-ligation (BDL) to develop cholestatic liver fibrosis. Primary HSCs were transfected with a miR-29a mimic and antisense inhibitor. Profibrogenic gene expression, histone methyltransferases and global genetic methylation were probed with real-time quantitative RT-PCR, immunohistochemical stain, Western blot and ELISA. Hepatic tissue in miR-29aTg mice displayed weak fibrotic matrix as evidenced by Sirius Red staining concomitant with low fibrotic matrix collagen 1α1 expression within affected tissues compared to the wild-type mice. miR-29a overexpression reduced the BDL exaggeration of methyltransferases, DNMT1, DNMT3b and SET domain containing 1A (SET1A) expression. It also elevated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) signaling within liver tissue. In vitro, miR-29a mimic transfection lowered collagen 1α1, DNMT1, DNMT3b and SET1A expression in HSCs. Gain of miR-29a signaling resulted in DNA hypomethylation and high PTEN expression. This study shines a new light on miR-29a inhibition of methyltransferase, a protective effect to maintain the DNA hypomethylation state that decreases fibrogenic activities in HSC. These robust analyses also highlight the miR-29a regulation of epigenetic actions to ameliorate excessive fibrosis during cholestatic liver fibrosis development.

Highlights

Chronic liver injuries caused by hepatitis and cholestasis lead to liver fibrosis, a detrimental reaction regulated by several signaling pathways [1]
We previously uncovered that miR-29a overexpression mitigated hepatocellular apoptosis and hepatic stellate cells (HSCs) activation during liver injury [1,6,7]. miR-29a reduction of TGF-β1 and histone deacetylase 4 signaling diminished profibrogenic phenotypes of HSCs and, thereby, ameliorated bile duct-ligation (BDL)-mediated cholestatic liver fibrosis [1,6]
We examined extracellular matrices (ECM) deposition and production with Sirius Red staining to confirm whether miR-29a overexpression changed the sequela of cholestatic liver injuries

Summary

Introduction

Chronic liver injuries caused by hepatitis and cholestasis lead to liver fibrosis, a detrimental reaction regulated by several signaling pathways [1]. HSC cultures in an activated state express high fibrogenic reactions in association with low expression of miR-29a, b and c [5]. MiR-29 overexpression attenuates collagen and fibrotic matrix accumulation in HSCs through directly targeting genes of interest [5,8]. We previously uncovered that miR-29a overexpression mitigated hepatocellular apoptosis and HSC activation during liver injury [1,6,7]. MiR-29a reduction of TGF-β1 and histone deacetylase 4 signaling diminished profibrogenic phenotypes of HSCs and, thereby, ameliorated bile duct-ligation (BDL)-mediated cholestatic liver fibrosis [1,6] We previously uncovered that miR-29a overexpression mitigated hepatocellular apoptosis and HSC activation during liver injury [1,6,7]. miR-29a reduction of TGF-β1 and histone deacetylase 4 signaling diminished profibrogenic phenotypes of HSCs and, thereby, ameliorated bile duct-ligation (BDL)-mediated cholestatic liver fibrosis [1,6]

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Discussion

Conclusion