Abstract
microRNA-29b (miR-29b) is known to be associated with TGF-β-mediated fibrosis, but the mechanistic action of miR-29b in liver fibrosis remains unclear and is warranted for investigation. We found that miR-29b was significantly downregulated in human and mice fibrotic liver tissues and in primary activated HSCs. miR-29b downregulation was directly mediated by Smad3 through binding to the promoter of miR-29b in hepatic stellate cell (HSC) line LX1, whilst miR-29b could in turn suppress Smad3 expression. miR-29b transduction in the liver of mice prevented CCl4 induced-fibrogenesis, concomitant with decreased expression of α-SMA, collagen I and TIMP-1. Ectopic expression of miR-29b in activated HSCs (LX-1, HSC-T6) inhibited cell viability and colony formation, and caused cell cycle arrest in G1 phase by downregulating cyclin D1 and p21cip1. Further, miR-29b induced apoptosis in HSCs mediated by caspase-9 and PARP. miR-29b inhibited its downstream effectors of PIK3R1 and AKT3 through direct targeting their 3'UTR regions. Moreover, knockdown of PIK3R1 or AKT3 suppressed α-SMA and collagen I and induced apoptosis in both HSCs and in mice. In conclusion, miR-29b prevents liver fibrogenesis by inhibiting HSC activation and inducing HSC apoptosis through inhibiting PI3K/AKT pathway. These results provide novel mechanistic insights for the anti-fibrotic effect of miR-29b.
Highlights
Hepatic fibrosis is an integral part in the progression of chronic inflammatory liver disease featured with the excessive accumulation of extracellular matrix (ECM) proteins
They became fully activated after cultured for more than 7 days with the typical cell morphology of a large, spread out and flattened polygonal shape observed at day 21 day (Figure 1B). mRNA expression of the key genes involved in the activation of hepatic stellate cells (HSCs) including alpha-smooth muscle actin (α-SMA), discoidin domain receptor 2 (DDR2), fibronectin 1 (FN1), integrin â1 (ITGB1) and platelet-derived growth factor receptor-β (PDGFR-β) was up-regulated in day 21 HSCs as compared to day 2 HSCs (Figure 1C), confirming the activation status of day 21 HSCs from the primary culture
We have previously reported that miR-29b is a downstream target gene of Smad3 and it is negatively regulated by transforming growth factor-β (TGF-β)/Smad signaling in renal fibrosis [15]
Summary
Hepatic fibrosis is an integral part in the progression of chronic inflammatory liver disease featured with the excessive accumulation of extracellular matrix (ECM) proteins. Fibrosis may progress to cirrhosis and primary liver cancer [1]. Hepatic fibrosis is a reversible disease, and an effective treatment can be able to prevent or reverse the fibrotic process [2]. Hepatic stellate cells (HSCs) play a key role in liver fibrogenesis [3]. HSCs are quiescent in normal liver but will be activated in response to liver damage [4]. Activated HSCs, on one side, secrete transforming growth factor beta-1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
