Inhibitory effects of microRNA 19b in hepatic stellate... : Hepatology (original) (raw)

Liver Biology/Pathobiology

Inhibitory effects of microRNA 19b in hepatic stellate cell-mediated fibrogenesis

Lakner, Ashley M.1,2; Steuerwald, Nury M.2; Walling, Tracy L.3; Ghosh, Sriparna2; Li, Ting2; McKillop, Iain H.1,3; Russo, Mark W.2,4; Bonkovsky, Herbert L.2,5,6,7; Schrum, Laura W.1,2,*,a

1_Department of Biology, University of North Carolina at Charlotte, Charlotte, NC_

2_Department of Internal Medicine, Liver-Biliary-Pancreatic Center, Carolinas Medical Center, Charlotte, NC_

3_Department of General Surgery, Carolinas Medical Center, Charlotte, NC_

4_Department of Internal Medicine, Center for Liver and Transplantation, Carolinas Medical Center, Charlotte, NC_

5_Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC_

6_Department of Medicine, University of Connecticut Health Center, Farmington, CT_

7_Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT_

*Address reprint requests to: Ph.D., Department of Internal Medicine, Liver-Biliary-Pancreatic Center, Carolinas Medical Center, Charlotte, NC, 28203

Email:[email protected]

Received 1 September 2011; Accepted 7 January 2012

Grant sponsor: National Institutes of Health (NIH); Grant Number: R01AA014891; Grant sponsor: Institutional funds from Carolinas Medical Center.

Potential conflict of interest: Nothing to report.

a_fax: 704-355-7648_

Abstract

Hepatic stellate cell (HSC) activation is a pivotal event in initiation and progression of hepatic fibrosis and a major contributor to collagen deposition driven by transforming growth factor beta (TGF-β). MicroRNAs (miRs), small noncoding RNAs modulating messenger RNA (mRNA) and protein expression, have emerged as key regulatory molecules in chronic liver disease. We investigated differentially expressed miRs in quiescent and activated HSCs to identify novel regulators of profibrotic TGF-β signaling. miR microarray analysis was performed on quiescent and activated rat HSCs. Members of the miR-17-92 cluster (19a, 19b, 92a) were significantly down-regulated in activated HSCs. Because miR 19b showed the highest fold-change of the cluster members, activated HSCs were transfected with miR 19b mimic or negative control and TGF-β signaling and HSC activation assessed. miR 19b expression was determined in fibrotic rat and human liver specimens. miR 19b mimic negatively regulated TGF-β signaling components demonstrated by decreased TGF-β receptor II (TGF-βRII) and SMAD3 expression. Computational prediction of miR 19b binding to the 3′ untranslated region of TGF-βRII was validated by luciferase reporter assay. Inhibition of TGF-β signaling by miR 19b was confirmed by decreased expression of type I collagen and by blocking TGF-β-induced expression of α1(I) and α2(I) procollagen mRNAs. miR 19b blunted the activated HSC phenotype by morphological assessment and decreased smooth muscle α-actin expression. Additionally, miR 19b expression was markedly diminished in fibrotic rat liver compared with normal liver; similarly, miR 19b expression was markedly down-regulated in fibrotic compared with normal human livers. Conclusion: miR 19b is a novel regulator of TGF-β signaling in HSCs, suggesting a potential therapeutic approach for hepatic fibrosis. (HEPATOLOGY 2012;56:300–310)