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: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:Background: HGF/c-Met signaling plays a pivotal role in hepatocyte survival and tissue remodeling during liver regeneration. Treatment with HGF has been shown to accelerate resolution of fibrotic liver lesions in experimental animal models. To formally address the importance of c-Met signaling in hepatocytes in the context of chronic liver injury, we have used hepatocyte-specific Metfl/fl;Alb-Cre+/- conditional knockout mice (KO) and a model of liver fibrosis. Methods: CCl4 was administrated biweekly over a period of 4 weeks (injury phase), and the animals were followed over the next 4 weeks (healing phase). Macroscopic and microscopic changes during the injury and healing phases were monitored by IHC. Deposition of ECM was assessed by Sirius red staining and hydroxiproline content. Activation of hepatic stellate cells (HSC) was estimated by a-SMA using WB and IHC. Expression levels of the selected key fibrotic molecules were evaluated by RT-qPCR and WB. Time-dependent global transcriptomic changes from whole livers and isolated hepatocytes were examined using gene expression microarrays. Results: Loss of HGF/c-Met signaling in hepatocytes altered the hepatic microenvironment and dramatically aggravated hepatic fibrogenesis. Increased liver damage was associated with decreased hepatocyte proliferation, progressive accumulation of HSCs, and delayed fibrinolysis causing increased collagen deposit. Dystrophic calcification of necrotic areas impaired phagocytosis, resulting in sustained inflammatory and fibrogenic signaling further augmenting severity of fibrogenesis. Global gene-expression analysis demonstrated upregulation of key fibrogenic molecules, such as Tgf-Ã¢ and Pdgf-Ã¢, paralleled by a decreased expression of genes important for cell cycle, stress response and regeneration, which could be attributed to the c-Met deficiency in hepatocytes. Additionally, key chemotactic and inflammatory cytokines, including Ccl2, SDF1/Cxcr4 and Spp1, were upregulated in Metfl/fl;Alb-Cre+/- hepatocytes. However, the major pro-fibrotic signaling originated from the non-parenchymal cell compartments, as revealed by cell type-specific gene expression signatures. Conclusion: These results indicate that lack of c-Met signaling in hepatocytes disrupts the balance between extracellular matrix production and degradation and establish a protective role for c-Met against adverse microenvironment leading to the development of fibrotic liver disease. In the present study, we reported a detailed and comprehensive dynamic characterization of the cellular and molecular alterations involved in fibrosis in the liver of c-Met transgenic mice. Liver samples from female animals were collected at various time-points after fibrosis induction using CCL4 ranging from 0 weeks to 3 weeks. Tissue samples were divided into two parts; one was fixed in 10% formalin for histological evaluation and the other was used for RNA analysis.

Dataset Information

TGF-β1/p65/MAT2A: a novel pathway involved in the regulation of intracellular SAM and liver fibrogenesis - Part1

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TGF-β1/p65/MAT2A pathway regulates liver fibrogenesis via intracellular SAM.

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