Project description:Liver cholestasis is a chronic liver disease (CLD) which belongs to a major health problem. Cholestasis is characterised by a decrease in bile flow due to impaired secretion by hepatocytes or by obstruction of bile flow through intra- or extrahepatic bile ducts. Thereby cholestasis can induce ductal proliferation, hepatocyte injury and liver fibrosis. Notch signalling promotes the formation and maturation of ductular reactions. We investigated the liver regeneration process in the context of cholestasis induced by disruption of the Notch signalling pathway. Liver-specific deletion of Rbpj, which represents a key regulator of Notch signalling, induces severe cholestasis through impaired IHBD maturation, severe necrosis and increased lethality. Deregulation of the biliary compartment and cholestasis are associated with change of several signalling pathways including the Hippo pathway resulting in upregulation of SOX9, which is associated with transdifferentiation of hepatocytes. SOX9 upregulation in cholestatic liver injury in vitro is independent of Notch signalling. We could comprehensively address that Rbpj depletion is followed by deregulation of YAP/TEAD, which influences transdifferentiation of hepatocytes and thereby contributing to liver regeneration. In this study the liver regeneration process was analyzed in 4 weeks old Rbpj knockout mice and compared to 4 weeks old Rbpj wildtype mice.
Project description:Liver cholestasis is a chronic liver disease and a major health problem worldwide. Cholestasis is characterised by a decrease in bile flow due to impaired secretion by hepatocytes or by obstruction of bile flow through intra- or extrahepatic bile ducts. Thereby cholestasis can induce ductal proliferation, hepatocyte injury and liver fibrosis. Notch signalling promotes the formation and maturation of bile duct structures. Here we investigated the liver regeneration process in the context of cholestasis induced by disruption of the Notch signalling pathway. Liver-specific deletion of recombination signal binding protein for immunoglobulin kappa j region (Rbpj), which represents a key regulator of Notch signalling, induces severe cholestasis through impaired intra-hepatic bile duct (IHBD) maturation, severe necrosis and increased lethality. Deregulation of the biliary compartment and cholestasis are associated with the change of several signalling pathways including a Kyoto Encyclopedia of Genes and Genomes (KEGG) gene set representing the Hippo pathway, further yes-associated protein (YAP) activation and upregulation of SRY (sex determining region Y)-box 9 (SOX9), which is associated with transdifferentiation of hepatocytes. SOX9 upregulation in cholestatic liver injury in vitro is independent of Notch signalling. We could comprehensively address that in vivo Rbpj depletion is followed by YAP activation, which influences the transdifferentiation of hepatocytes and thereby contributing to liver regeneration.
Project description:Cholestatic injuries, featured with regional damage around the periportal, cause considerable mortality without curative therapies. It is technically challenging to dissect regional cell-cell interactions and molecular changes to fully understand cholangiopathies. Here, we generated a high-definition atlas of spatiotemporal transcriptome during cholestatic injury and repair. Remarkably, cholangiocytes functioned as a periportal hub by integrating signals from neighboring cells. We also dissected periportal damage, spatial heterogenous reprogramming and zonal regeneration, which appeared to be strongly associated with cholangiocyte. Moreover, spatiotemporal analyses revealed a key inhibitory rheostat for hepatocyte proliferation. Together, our study provides a comprehensive resource that is instrumental to demarcate regional cholestatic injury.
Project description:Ductular reactive (DR) cells exacerbate cholestatic liver injury and fibrosis. In this study we posited that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) emanating from recruited macrophages restrains DR cell expansion by apoptosis, thereby limiting cholestatic liver injury. Cholestatic liver injury was induced in Wild type (WT), Trailfl/fl and in myeloid-specific Trail deleted (TrailΔmye) C57BL/6 mice using the DDC diet. The DDC diet induced injury and hepatomegaly. However, parameters of liver injury, fibrosis, ductular reaction and inflammation were all increased in the TrailΔmye mice as compared to the WT and Trailfl/fl mice. To better resolve the gene expression profile of cholangiocytes that may promote the recruitment of myeloid cells into the periportal neighborhood, we performed spatial transcriptomics on FPPE liver tissue sections from WT and TrailΔmye mice that were fed the control or DDC diet using the NanoString GeoMx DSP platform (Cat. No. 121401103, GeoMx NGS RNA WTA Mm).
Project description:The transcriptional regulator Rbpj is involved in T-helper (TH) subset polarization, but its function in Treg cells remains unclear. Here we show that Treg-specific Rbpj deletion leads to splenomegaly and lymphadenopathy despite increased numbers of Treg cells with a polyclonal TCR repertoire. A specific defect of Rbpj-deficient Treg cells in controlling TH2 polarization and B cell responses was observed, leading to the spontaneous formation of germinal centers and a TH2-associated immunoglobulin class switch as well as T-cell polarization into TH2 effector cells. The observed phenotype was environment-dependent and could be induced by infection with parasitic nematodes. Rbpj-deficient Treg cells adopted open chromatin landscapes and gene expression profiles reminiscent of tissue-derived TH2-polarized Treg cells, with a prevailing footprint of transcription factor Gata-3. The over-expression of Ilt3 rendered Rbpj-deficient Treg cells incompatible to specifically restrain TH2 responses, finally leading to severe and fatal lymphoproliferative disease.
Project description:Bile acid accumulation and subsequent liver damage is a frequent adverse effect induced by drugs. Considerable efforts have therefore been focused on the introduction and characterization of tools that allow reliable prediction of this type of drug-induced liver injury. Among those are the cholestatic index and transcriptomic profiling, which are typically assessed in in vitro settings. The present study was set up to test the applicability of both tools to non-pharmaceutical compounds with cholestatic potential, including the industrial compound bis(2-ethylhexyl)phthalate, the cosmetic ingredients triclosan and octynoic acid, the herbicides paraquat and quizalofop-para-ethyl, and the food additives sunset yellow and tartrazine, in a human hepatoma cell culture model of cholestatic liver injury. The cholestatic index method showed cholestatic liability of sunset yellow, tartrazine and triclosan. Of those, tartrazine induced transcriptional changes reminiscent of the transcriptional profile of cholestatic drugs. Furthermore, a number of genes were found to be uniquely modulated by tartrazine, in accordance with the cholestatic drugs atazanavir, cyclosporin A and nefazodone, which may have potential as novel transcriptomic biomarkers of chemical-induced cholestatic liver injury. In conclusion, unambiguous identification of the non-pharmaceutical compounds tested in this study as inducers of cholestasis could not be achieved.
Project description:Cholestasis is characterized by hepatic accumulation of cytotoxic bile acids (BAs), which often subsequentlyleads to liver injury, inflammation, fibrosis, and ultimately liver cirrhosis. Fibroblast growth factor 21 (FGF21) is a liver secreted hormone with pleiotropic effects on the homeostasis of glucose, lipid, and energy metabolism. However, whether hepatic FGF21 plays a role in cholestatic liver injury remains elusive. We found that serum and hepatic FGF21 levels were significantly increased in response to cholestatic liver injury. Hepatocyte-specific deletion of Fgf21 exacerbated hepatic accumulation of BAs, further accentuating liver injury. Consistently, administration of rFGF21 ameliorated cholestatic liver injury in α-naphthylisothiocyanate (ANIT)-treated and Mdr2 deficiency mice. Mechanically, FGF21 activated a hepatic FGFR4-JNK signaling pathway to decrease Cyp7a1 expression, thereby reducing hepatic BAs pool. Our study demonstrates that hepatic FGF21 functions as an adaptive stress-responsive signal to downregulate BA biosynthesis, thereby ameliorating cholestatic liver injury, and FGF21 analogs may represent a candidate therapy for cholestatic liver diseases.
Project description:Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis and is among the most common causes of cancer death worldwide. KrasG12D mutation is the main driver mutation but insuffi-cient for progression of invasive cancer on its own indicating that other pathways, such as Notch signaling may participate in that process. RBPJ, the only transcription factor in Notch signaling, is frequently lost in human cancers and associated with more aggressive breast cancer phenotype. Notch-independently, in complex with P48, RBPJ initiates transcription of its paralogue RBPJL ensuring acinar differentiation. The RBPJ knockout has an embryonic lethal effect. Mice with pancreas-specific deletion of RBPJ presented with less acinar tissue and large duct-like structures suggesting a relevance of RBPJ for acinar to ductal reprogramming and even pancreatic neoplasia. Here, we found reduced RBPJ expression level in the human PDAC specimens. Analyses of transgenic mouse models of an inducible P48-dependent RBPJ knockout revealed that it is dispensable for the maintenance adult acinar cells. In the context of oncogenic KRAS expression, the RBPJ deficiency facilitated the development of PanIN lesions with massive fibrotic stroma. Interestingly, RNA seq data revealed corresponding transcription pattern prior to phenotypic alterations.