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Hepatic stellate cells (HSC), quiescent and activated - influence of ltbp1-k.o. on activation in vitro

ABSTRACT: Hepatic stellate cells (HSC) constitute the most important fibrogenic cell type during liver fibrosis. To analyse the different phenotypes of quiescent and activated cells, cells of 5 animals were transdifferentiated in a well established in vitro transdifferentiaition assay and compared to freshly seeded, quiescent HSC. Gene expression profiling of quiescent and in vitro activated HSC revealed well known and new marker genes upregulated upon HSC activation. ltbp1 (latent transforming growth factor beta binding protein 1) is a crucial factor controlling the secretion and bioactivation of TGFß1. Using the data comparing quiescent and activated HSC, we were able to qualify the subtle but reproducible differences in gene expression observed when comparing activated ltbp1-deficient and activted wt HSC. ltbp1-deficient HSC showed a less fibrogenic phenotype after 6 days of in vitro transdifferentiation compared to the wt counterparts. The microarray data was indepently confirmed in vivo using an experimental model for the induction of liver fibrosis (ligation of the common bile duct). ltbp1-/- mice, after 4 weeks of bile obstruction, showed markedly reduced signs of liver fibrosis. Keywords: gene expression profiling, analysyis of a fibrogenic cell type in the liver and the influence of ltbp1-k.o.

ORGANISM(S): Mus musculus

PROVIDER: GSE5670 | GEO | 2007/03/31

SECONDARY ACCESSION(S): PRJNA96949

REPOSITORIES: GEO

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Project description:BACKGROUND AND AIM: We previously established that endoplasmic reticulum stress leads to unfolded protein response (UPR) that promotes liver fibrosis by activating hepatic stellate cell (HSC). We aimed to determine the role of X-box binding protein 1 (XBP1), one of three UPR effector pathways, in the fibrogenic HSC activation. METHODS: XBP1 expression was measured by qPCR in tunicamycin-treated human HSC lines (TWNT4 and LX2) and culture-activated human primary HSCs. XBP1 was overexpressed in primary human HSCs and the HSC lines, and fibrogenic genes (COL1A1, ACTA2, PDGFRB, MMP2, TIMP1) and encoded proteins were assessed by qPCR and Western blotting, respectively. Autophagy was inhibited by knockdown of ATG7. Genome-wide transcriptome profiling was performed to determine modulated molecular pathway by XBP1. In vivo XBP1 activation was assessed in transcriptome datasets of fibrotic mouse models and immunohistochemistry of human liver tissues. RESULTS: XBP1 overexpression accompanied both tunicamycin- and culture-based HSC activation. Ectopic overexpression of XBP1 induced fibrogenic gene expression in the HSC lines, which was inhibited by knockdown of ATG7. UPR pathway together with PDGFRB pathway, a hallmark of HSC activation, were induced in transcriptome profiles of XBP1-transduced HSC lines. Some known fibrogenic pathways such as transforming growth factor (TGF)-beta pathway were not induced, suggesting partial contribution of XBP1 to the entire fibrogenic HSC activation machinery. XBP1 target gene signature defined in our XBP1-overexpressing HSC lines was significantly induced in liver tissue transcriptome profiles of carbon tetrachloride-treated or bile duct-ligated mouse models, and XBP1 and alpha-smooth muscle actin (encoded by ACTA2, another hallmark of HSC activation) were co-localized in human fibrotic liver tissues, collectively supporting involvement of XBP1 in HSC activation and fibrogesis in vivo. CONCLUSIONS: XBP1-mediated UPR is at least partially responsible for fibrogenic HSC activation via autophagy.

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Hepatic stellate cells (HSC), quiescent and activated - influence of ltbp1-k.o. on activation in vitro

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