Project description:Gene-expression profiles of hepatic stellate cells isolated from IL15R-alpha knockout mouse IL-15 and its high affinity receptor IL-15Rα are widely expressed in immune cells including dendritic cells and macrophages and non-immune cells such as hepatocytes, oval cells and hepatic stellate cells (HSC). IL-15 signaling has important functions in natural killers (NK), natural killers T (NKT) and cytotoxic T (CD8+T) cell homeostasis and also in liver regeneration. We hypothesized that IL-15 may have a protective role during liver fibrosis progression due to its role in NK cell homeostasis. We compared fibrosis progression in IL-15Rα knockout mice (IL-15RαKO) to wild type mice using two mechanistically distinct models, chronic carbon tetrachloride (CCl4) exposure and bile duct ligation (BDL). Enhanced fibrosis progression was observed in IL-15RαKO mice in both models. Furthermore, using congenic bone marrow transplantation (BMT), we demonstrated an unexpected role for IL-15 signaling in hepatic resident cells for the maintenance of liver NK and CD8+T cell populations. Using this approach, transplanting IL-15RKO hematopoietic cells results in NK defect that surprisingly is not reflected in a change of fibrosis progression. However, chimeric mice with defect of IL-15R on liver resident cells have similar NK defects and significant more fibrosis after CCL4 liver injury. This supports a direct protective, anti-fibrogenic role for IL-15R on one of the radioresistant liver cell populations (hepatocytes, HSC and sessile Kupffer cells). Microarray analysis of IL15RKO HSC suggests up-regulation of collagen transcripts and down-regulation of pathways involved in cell proliferation/survival. Finally, activated HSCs isolated from IL-15RKO mice show increased collagen secretion and as predicted, no changes in the growth curves. In summary, IL-15Rα signaling has an anti-fibrotic effect through both BM-derived and hepatic resident cells. These findings establish a rationale to explore IL-15 signaling in HSC as a potential therapeutic target in liver fibrogenesis.
Project description:Hepatic fibrosis, the wound-healing response to repeated liver injury, ultimately leads to cirrhosis. There is an urgent need to develop effective antifibrotic therapies. Ghrelin (encoded by Ghrl) is an orexigenic hormone that has pleiotrophic functions including protection against cell death1. Here we investigate whether ghrelin modulates liver fibrosis and protects from acute liver injury. Recombinant ghrelin reduced the fibrogenic response to prolonged bile duct ligation in rats. This effect was associated with decreased liver injury and myofibroblast accumulation as well as attenuation of the altered gene expression profile. Ghrelin also reduced fibrogenic properties in cultured hepatic stellate cells. Moreover, Ghrl-/- mice developed exacerbated hepatic fibrosis and liver damage after chronic injury. Ghrelin also protected rat livers from acute liver injury and reduced the extent of oxidative stress and the inflammatory response. In patients with chronic liver diseases, ghrelin serum levels decreased in those with advanced fibrosis and hepatic expression of the ghrelin gene correlated with expression of fibrogenic genes. Finally, in patients with chronic hepatitis C, single nucleotide polymorphisms of the ghrelin gene (-994CT and â604GA) influenced the progression of liver fibrosis. We conclude that ghrelin exerts antifibrotic effects on the liver and may represent a novel antifibrotic therapy. Experiment Overall Design: Rats were divided into three groups: control rats receiving saline (sham operation), rats with bile duct ligation receiving saline and rats with bile duct ligation receiving recombinant ghrelin (10 micrograms/Kg/day by a subcutaneous osmotic mimi-pump). For the microarray analysis samples from 6 rats were analyzed except for the ghrelin-treated group (5 rats).
Project description:Hepatic fibrosis, the wound-healing response to repeated liver injury, ultimately leads to cirrhosis. There is an urgent need to develop effective antifibrotic therapies. Ghrelin (encoded by Ghrl) is an orexigenic hormone that has pleiotrophic functions including protection against cell death1. Here we investigate whether ghrelin modulates liver fibrosis and protects from acute liver injury. Recombinant ghrelin reduced the fibrogenic response to prolonged bile duct ligation in rats. This effect was associated with decreased liver injury and myofibroblast accumulation as well as attenuation of the altered gene expression profile. Ghrelin also reduced fibrogenic properties in cultured hepatic stellate cells. Moreover, Ghrl-/- mice developed exacerbated hepatic fibrosis and liver damage after chronic injury. Ghrelin also protected rat livers from acute liver injury and reduced the extent of oxidative stress and the inflammatory response. In patients with chronic liver diseases, ghrelin serum levels decreased in those with advanced fibrosis and hepatic expression of the ghrelin gene correlated with expression of fibrogenic genes. Finally, in patients with chronic hepatitis C, single nucleotide polymorphisms of the ghrelin gene (-994CT and –604GA) influenced the progression of liver fibrosis. We conclude that ghrelin exerts antifibrotic effects on the liver and may represent a novel antifibrotic therapy.
Project description:Background & Aims: Rapid induction of beta-PDGF receptor (beta-PDGFR) is a core feature of hepatic stellate cell activation, the hallmark of liver fibrogenesis. However, biological consequences of the induction are not well characterized. We aimed to determine the involvement of beta-PDGFR-mediated molecular pathway activation on hepatic stellate cells in liver injury, fibrogenesis, and carcinogenesis in vivo. Methods: Loss and constitutive activation of beta-PDGFR were assessed in mouse models with either a stellate cell-specific beta-PDGFR knockout or the expression of an autoactivating mutation respectively. Liver injury and fibrosis were induced in two mechanistically distinct models: carbontetrachloride (CCl4) treatment and ligation of the common bile duct. Hepatocarcinogenesis with underlying liver injury/fibrosis was assessed by a single dose of diethylnitrosamine (DEN) followed by repeated injections of CCl4. Genome-wide expression profiling was performed isolated stellate cells from these models to determine deregulated pathways. Results: Depletion of beta-PDGFR in hepatic stellate cells led to decreased histological liver injury, serum transaminases, collagen alpha 1(I) and alpha smooth muscle actin expression, and collagen deposition. Stellate cell proliferation was significantly reduced after acute hepatic injury in vivo. In contrast, autoactivation of beta-PDGFR in stellate cells accelerated liver fibrosis, most prominently after 6 weeks of CCl4 induced injury. There was no difference in development of DEN-induced pre-neoplastic loci according to the status of beta-PDGFR. Conclusions: Depletion of beta-PDGFR in hepatic stellate cells attenuated the development of liver injury, fibrosis, and stellate cell proliferation in multiple animal models, whereas the constitutive activation of beta-PDGFR enhanced fibrosis. However, manipulation of beta-PDGFR alone did not reduce development of dysplastic nodules. These findings indicate that titration of receptor beta-PDGFR expression on stellate cells parallels fibrosis and injury, but may not impact the development of hepatic neoplasia alone. Hepatic stellate cells were isolated from liver of beta-PDGFR-wild-type or knockout mice, and treated with beta-PDGF ligand or vehicle control.
Project description:Hepatic fibrosis is a dynamic process characterized by the net accumulation of extracellular matrix resulting from chronic liver injury such as nonalcoholic steatohepatitis. During the pathogenesis of hepatic fibrosis, activation of hepatic stellate cells (HSCs) causes transdifferentiation of quiescent cells into proliferative and fibrogenic myofibroblasts. In the present study, we developed a novel RORα-selective ligand, ODH-08, based on the modification of JC1-40, a previously reported N-methylthiourea analog. Administration of ODH-08 to Western diet (WD)-fed mice improved the signs of hepatic fibrosis: decreased hepatic collagen deposition and suppression of the expression of fibrogenic markers. ODH-08 inhibits the TGF1-induced fibrogenic activation of HSCs through suppression of the TGFβ1–SMAD signaling pathway, which represents a novel mechanism for the antifibrogenic effect of RORα. Thus, ODH-08 appears to be a promising antifibrotic agent to treat hepatic fibrosis. We performed a microarray analysis in the liver tissue of ODH-08-treated WD-fed mice to anlyse differentially expressed genes under ODH-08 administration. The control group was vehicle-treated WD-fed mice.
Project description:Liver injury causes “transdifferentiation” of quiescent hepatic stellate cells (Q-HSCs) into wound repairing myofibroblasts (MF-HSCs), whose uncontrolled activation leads ultimately to liver fibrosis. Although this process is triggered by deep metabolic and transcriptional reprogramming, functional links between these two key events are not yet understood. Here, using a compendium of in vitro, ex vivo and in vivo models of fibrogenic liver injuries in addition to human liver samples, we report that O-linked β D N acetylglucosaminylation (O GlcNAcylation), a post-translational modification (PTM) considered as nutritional sensor, is increased during myofibroblastic activation of HSCs and is required for their pro-fibrotic activities. Mechanistically, a multi omics approach combining proteomic, epigenomic and transcriptomic data mining revealed that O GlcNAcylation controls the transcriptional program of MF-HSCs by targeting the key fibrogenic transcription factors Basonuclin 2 (BNC2) and TEA domain transcription factor 4 (TEAD4) together with the Yes associated protein 1 (YAP1) co-activator. Indeed, inhibition of protein O GlcNAcylation impedes their stability leading to decreased functionality of the BNC2/TEAD4/YAP1 complex towards promoting activation of fibrogenic transcriptional regulatory elements. Altogether, this study unravels the fibrogenic role of protein O-GlcNAcylation identifying a vulnerable regulatory process in activated HSCs.
Project description:Background & Aims: Rapid induction of beta-PDGF receptor (beta-PDGFR) is a core feature of hepatic stellate cell activation, the hallmark of liver fibrogenesis. However, biological consequences of the induction are not well characterized. We aimed to determine the involvement of beta-PDGFR-mediated molecular pathway activation on hepatic stellate cells in liver injury, fibrogenesis, and carcinogenesis in vivo. Methods: Loss and constitutive activation of beta-PDGFR were assessed in mouse models with either a stellate cell-specific beta-PDGFR knockout or the expression of an autoactivating mutation respectively. Liver injury and fibrosis were induced in two mechanistically distinct models: carbontetrachloride (CCl4) treatment and ligation of the common bile duct. Hepatocarcinogenesis with underlying liver injury/fibrosis was assessed by a single dose of diethylnitrosamine (DEN) followed by repeated injections of CCl4. Genome-wide expression profiling was performed isolated stellate cells from these models to determine deregulated pathways. Results: Depletion of beta-PDGFR in hepatic stellate cells led to decreased histological liver injury, serum transaminases, collagen alpha 1(I) and alpha smooth muscle actin expression, and collagen deposition. Stellate cell proliferation was significantly reduced after acute hepatic injury in vivo. In contrast, autoactivation of beta-PDGFR in stellate cells accelerated liver fibrosis, most prominently after 6 weeks of CCl4 induced injury. There was no difference in development of DEN-induced pre-neoplastic loci according to the status of beta-PDGFR. Conclusions: Depletion of beta-PDGFR in hepatic stellate cells attenuated the development of liver injury, fibrosis, and stellate cell proliferation in multiple animal models, whereas the constitutive activation of beta-PDGFR enhanced fibrosis. However, manipulation of beta-PDGFR alone did not reduce development of dysplastic nodules. These findings indicate that titration of receptor beta-PDGFR expression on stellate cells parallels fibrosis and injury, but may not impact the development of hepatic neoplasia alone.
Project description:In order to identify novel transcription target genes of COUP-TFII that could account for the fibrogenic phenotype of human hepatic stellate cells (HSCs), we carried out an exploratory microarray analysis with mRNA extracted from cultured HSC transfected with COUP-TFII wt or control plasmid.
Project description:Hepatic stellate cells (HSCs) are the primary cell type responsible for liver fibrosis, the final common pathway leading to cirrhosis and liver failure for nearly every cause of chronic liver disease. Activation of HSCs in response to injury represents the key step in hepatic fibrogenesis, and is characterized by a phenotypic change from a non-fibrogenic, quiescent HSC to a fibrogenic HSC myofibroblast that secretes extracellular matrix proteins responsible for the fibrotic scar. We developed a small molecule screen to identify compounds that revert fibrotic human HSC myofibroblasts to an inactive phenotype through the quantification of lipid droplets with fluorescent microscopy. Conditions were optimized in a 384-well format using culture in Matrigel as a positive control. We screened 1600 compounds and identified 30 small molecules that induce reversion to an inactive phenotype. Among the hits, we identified five tricyclic antidepressants (TCAs) and showed that this class of drugs also repressed ACTA2 and COL1A1 while promoting PPAR-gamma expression. RNA sequencing analysis implicated extracellular matrix proteins and the sphingolipid pathway as a target of the TCAs.
Project description:Liver fibrosis is characterized by the activation of perivascular hepatic stellate cells (HSCs), the release of fibrogenic nano-sized extracellular vesicles (EVs) and increased HSC glycolysis. Nevertheless, how glycolysis in HSCs coordinates fibrosis amplification through tissue zone-specific pathways remains elusive. Here, we demonstrate that HSC-specific genetic inhibition of glycolysis reduced liver fibrosis. Moreover, spatial transcriptomics revealed a fibrosis-mediated upregulation of EV-related pathways in the liver pericentral zone, which was abrogated by the glycolysis genetic inhibition. Mechanistically, glycolysis in HSCs upregulated the expression of EV-related genes such as RAB31 by enhancing histone-3-lysine-9 acetylation on the promoter region, which increased EV release. Functionally, these glycolysis-dependent EVs increased fibrotic gene expression in recipient HSC. Furthermore, EVs derived from glycolysis-deficient mice abrogated liver fibrosis amplification in contrast to glycolysis-competent mouse EVs. In summary, glycolysis in HSCs amplifies liver fibrosis by promoting fibrogenic EV release in the hepatic pericentral zone, which represents a potential therapeutic target.