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

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 (TGFβ). microRNAs (miRs), small non-coding RNAs modulating 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 TGFβ 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. Since miR 19b showed the highest fold-change of the cluster members, activated HSCs were transfected with miR 19b mimic or negative control and TGFβ signaling and HSC activation assessed. miR 19b expression was determined in fibrotic rat and human liver specimens. miR 19b mimic negatively regulated TGFβ signaling components demonstrated by decreased TGFβ receptor II (TGFβRII) and SMAD3 expression. Computational prediction of miR 19b binding to the 3’UTR of TGFβRII was validated by luciferase reporter assay. Inhibition of TGFβ signaling by miR 19b was confirmed by decreased expression of type I collagen and by blocking TGFβ-induced expression of α1(I) and α2(I) procollagen mRNAs. miR 19b blunted the activated HSC phenotype by morphological assessment and decreased αSMA expression. Additionally, miR 19b expression was markedly diminished in fibrotic rat liver compared to normal liver; similarly, miR 19b expression was markedly down-regulated in fibrotic compared to normal human livers. CONCLUSIONS miR 19b is a novel regulator of TGFβ signaling in HSCs suggesting a potential therapeutic approach for hepatic fibrosis.

miR-17∼92 family clusters control iNKT cell ontogenesis via modulation of TGF-β signaling

“…These highly redundant clusters comprise 15 miRNAs that form four "seed" families: the miR-17, miR-18, miR-19, and miR-92 families. Two sequences in the 3′UTR of Tgfbr2 mRNA are experimentally validated targets for all eight miRNAs belonging to the miR-17 and miR-19 families (25)(26)(27)(28). The independent miR-21 and miR-23b were also predicted to target Tgfbr2 mRNA.…”

Expression of platelet-derived growth factor-C and insulin-like growth factor I in hepatic stellate cells is inhibited by miR-29

“…Others such as miR-19b, miR-150, and miR-194 are suggested to participate in TGF-b signaling and myofibroblastic HSC activation, respectively. 24,25 In particular, members of the miR-29 family, repressed during myofibroblastic activation, 26 are of special interest, because their dysregulation has been shown to be involved in synthesis of ECM proteins. [26][27][28][29][30] The miR-29 family consists of miR-29a, miR-29b, and miR-29c, differing only in two or three bases.…”

MicroRNAs in the Communication between Cancer Associated Fibroblasts (CAF) and Cancer Cells

“…Upregulation was also identified for miR-199a-5p/199a-3p and miR-221/222 in hepatitis C induced liver fibrosis in a fibrosis progression-dependent manner. [31] Members of the miR-17-92 cluster (19a, 19b, 92a) [32], miR-29, miR-133, miR-193 and miR-30c [33,34] were observed to be specifically downregulated in human liver fibrosis and HSC, while they showed a reciprocal expression pattern after recovery from liver fibrosis. Reduced expression of miR-144 was correlated with elevated HSC-specific expression of transforming growth factor-β1 (TGF-β1) and expression of α-SMA in fibrotic liver tissues.…”

“…[47] Furthermore, miR-19b blunted the activated HSC phenotype by morphological assessment and decreased α-SMA expression. [32] In HSCs another cluster member, miR-133a, is downregulated by TGF-β with subsequent stimulated expression of collagens. [34] The expression levels of fibrosis related genes (TIMP-1, MMP13, α1-procollagen) in HSCs were increased by overexpression of other members of the miR-214 cluster (miR-199a, 199a*).…”