Long-Term Fate of Human Fetal Liver Progenitor Cells Transplanted in Injured Mouse Livers.

Liver progenitor cells have the potential to repair and regenerate a diseased liver. The success of any translational efforts, however, hinges on thorough understanding of the fate of these cells after transplant, especially in terms of long-term safety and efficacy. Here, we report transplantation of a liver progenitor population isolated from human fetal livers into immune-permissive mice with follow-up up to 36 weeks after transplant.

Paracrine activation of hepatic stellate cells in platelet-derived growth factor C transgenic mice: evidence for stromal induction of hepatocellular carcinoma.

Cirrhosis is the primary risk factor for the development of hepatocellular carcinoma (HCC), yet the mechanisms by which cirrhosis predisposes to carcinogenesis are poorly understood. Using a mouse model that recapitulates many aspects of the pathophysiology of human liver disease, we explored the mechanisms by which changes in the liver microenvironment induce dysplasia and HCC. Hepatic expression of platelet-derived growth factor C (PDGF-C) induces progressive fibrosis, chronic inflammation, neoangiogenesis and sinusoidal congestion, as well as global changes in gene expression.

Impaired lipid accumulation in the liver of Tsc2-heterozygous mice during liver regeneration.

Tuberin is a negative regulator of mTOR pathway. To investigate the function of tuberin during liver regeneration, we performed 70% hepatectomy on wild-type and Tsc2+/- mice. We found the tuberin phosphorylation correlated with mTOR activation during early liver regeneration in wild-type mice.

A disintegrin and metalloproteinase 17 regulates TNF and TNFR1 levels in inflammation and liver regeneration in mice.

A disintegrin and metalloproteinase 17 (ADAM17), or tumor necrosis factor (TNF)-α-converting enzyme, is a key metalloproteinase and physiological convertase for a number of putative targets that play critical roles in cytokine and growth factor signaling. These interdependent pathways are essential components of the signaling network that links liver function with the compensatory growth that occurs during liver regeneration following 2/3 partial hepatectomy (PH) or chemically induced hepatotoxicity. Despite identification of many soluble factors needed for efficient liver regeneration, very little is known about how such ligands are regulated in the liver.

Sustained Glutathione Deficiency Interferes with the Liver Response to TNF-α and Liver Regeneration after Partial Hepatectomy in Mice.

Glutathione (GSH) is a critical intracellular antioxidant that is active in free radical scavenging and as a reducing equivalent in biological reactions. Recent studies have suggested that GSH can affect cellular function at the level of gene transcription as well, in particular by affecting NF-κB activation. Additionally, increased or decreased GSH levels have been tied to increased or decreased hepatocyte proliferation, respectively.

Acyclic retinoid targets platelet-derived growth factor signaling in the prevention of hepatic fibrosis and hepatocellular carcinoma development.

Hepatocellular carcinoma (HCC) often develops in association with liver cirrhosis, and its high recurrence rate leads to poor patient prognosis. Although recent evidence suggests that peretinoin, a member of the acyclic retinoid family, may be an effective chemopreventive drug for HCC, published data about its effects on hepatic mesenchymal cells, such as stellate cells and endothelial cells, remain limited. Using a mouse model in which platelet-derived growth factor (PDGF)-C is overexpressed (Pdgf-c Tg), resulting in hepatic fibrosis, steatosis, and eventually, HCC development, we show that peretinoin significantly represses the development of hepatic fibrosis and tumors.

Liver Regeneration after Partial Hepatectomy Is Not Impaired in Mice with Double Deficiency of Myd88 and IFNAR Genes.

Liver regeneration is known to occur in mice lacking one or more Toll-like receptors (TLRs) or the adaptor protein MyD88. Though MyD88 is required for signaling by many TLRs, others signal via MyD88-independent pathways, leading to the induction of type I interferons (IFNs). Here, we assessed liver regeneration after partial hepatectomy (PH) in mice lacking both MyD88 and the type I IFN receptor (Myd88-IFNAR double-KO).

The tyrphostin AG1478 inhibits proliferation and induces death of liver tumor cells through EGF receptor-dependent and independent mechanisms.

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death. Different signaling pathways are de-regulated in this pathogenesis, among them the epidermal growth factor receptor one (EGFR/Erb1). Here we show that blockage of this pathway by the tyrphostin 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) in different liver tumor cell lines promotes both inhibition of cell proliferation and induction of cell death, which are coincident with arrest in the G1 phase of the cell cycle, caspase-3 activation and DNA fragmentation.

Extracellular matrix dynamics in hepatocarcinogenesis: a comparative proteomics study of PDGFC transgenic and Pten null mouse models.

We are reporting qualitative and quantitative changes of the extracellular matrix (ECM) and associated receptor proteomes, occurring during the transition from liver fibrosis and steatohepatitis to hepatocellular carcinoma (HCC). We compared two mouse models relevant to human HCC: PDGFC transgenic (Tg) and Pten null mice, models of disease progression from fibrosis and steatohepatitis to HCC. Using mass spectrometry, we identified in the liver of both models proteins for 26 collagen-encoding genes, providing the first evidence of expression at the protein level for 16 collagens.

Sorafenib sensitizes hepatocellular carcinoma cells to physiological apoptotic stimuli.

Sorafenib increases survival rate of patients with advanced hepatocellular carcinoma (HCC). The mechanism underlying this effect is not completely understood. In this work we have analyzed the effects of sorafenib on autocrine proliferation and survival of different human HCC cell lines.

Toll-like receptor 4 and myeloid differentiation factor 88 provide mechanistic insights into the cause and effects of interleukin-6 activation in mouse liver regeneration.

Unlabelled: Partial hepatectomy (PH) consistently results in an early increase of circulating interleukin-6 (IL-6), which is thought to play a major role in liver regeneration. Activation of this cytokine after PH requires the adaptor protein, MyD88, but the specific MyD88-related receptors involved remain unidentified. It is also unknown whether the magnitude of IL-6 elevation determines the extent of subsequent hepatocyte proliferation.

A random mutation capture assay to detect genomic point mutations in mouse tissue.

Herein, a detailed protocol for a random mutation capture (RMC) assay to measure nuclear point mutation frequency in mouse tissue is described. This protocol is a simplified version of the original method developed for human tissue that is easier to perform, yet retains a high sensitivity of detection. In contrast to assays relying on phenotypic selection of reporter genes in transgenic mice, the RMC assay allows direct detection of mutations in endogenous genes in any mouse strain.

New concepts in liver regeneration.

The unique ability of the liver to regenerate itself has fascinated biologists for years and has made it the prototype for mammalian organ regeneration. Harnessing this process has great potential benefit in the treatment of liver failure and has been the focus of intense research over the past 50 years. Not only will detailed understanding of cell proliferation in response to injury be applicable to other dysfunction of organs, it may also shed light on how cancer develops in a cirrhotic liver, in which there is intense pressure on cells to regenerate.

The transforming growth factor-beta (TGF-β) mediates acquisition of a mesenchymal stem cell-like phenotype in human liver cells.

Transforming growth factor-beta (TGF-β) mediates several and sometime opposite effects in epithelial cells, inducing growth inhibition, and apoptosis but also promoting an epithelial to mesenchymal transition (EMT) process, which enhances cell migration and invasion. TGF-β plays relevant roles in different liver pathologies; however, very few is known about its specific signaling and cellular effects in human primary hepatocytes. Here we show that TGF-β inhibits proliferation and induces pro-apoptotic genes (such as BMF or BIM) in primary cultures of human fetal hepatocytes (HFH), but also up-regulates anti-apoptotic genes, such as BCL-XL and XIAP.

Inactivation of p38 MAPK during liver regeneration.

There is increasing evidence that p38 MAPK, which is classified as a stress-activated kinase, also participates in cell cycle regulation, functioning as a suppressor of cell proliferation and tumorigenesis. We conducted a study of p38 MAPK phosphorylation during liver regeneration in mice to determine whether p38 MAPK activation or inactivation may correlate with events that lead to DNA replication after partial hepatectomy (PH), and whether p38 MAPK activation may be required for hepatocyte DNA replication in vivo and in culture. We report that active p38 (Pi-p38 MAPK) is present in normal liver, is rapidly inactivated starting 30 min after PH, and is re-activated by 12h.

Attenuated progression of diet-induced steatohepatitis in glutathione-deficient mice.

In nonalcoholic fatty liver disease (NAFLD), depletion of hepatic antioxidants may contribute to the progression of steatosis to nonalcoholic steatohepatitis (NASH) by increasing oxidative stress that produces lipid peroxidation, inflammation, and fibrosis. We investigated whether depletion of glutathione (GSH) increases NASH-associated hepatic pathology in mice fed a diet deficient in methionine and choline (MCD diet). Wild-type (wt) mice and genetically GSH-deficient mice lacking the modifier subunit of glutamate cysteine ligase (Gclm null mice), the rate-limiting enzyme for de novo synthesis of GSH, were fed the MCD diet, a methionine/choline-sufficient diet, or standard chow for 21 days.

Mouse models of hepatocellular carcinoma.

The etiology of liver cancer is well known, but despite recent progress in the application of molecular techniques for the analysis of the development of these tumors, we still lack precise knowledge about pathogenesis of hepatocellular carcinoma (HCC). Animal models can provide essential knowledge about HCC pathogenesis, particularly if they mimic the tissue environment in which human tumors develop. The synergism between studies in animal models and human tumors is strengthened by using comparative genomic analysis to identify genes and pathways that are critical for both mouse and human oncogenesis.

TGF-beta inactivation and TGF-alpha overexpression cooperate in an in vivo mouse model to induce hepatocellular carcinoma that recapitulates molecular features of human liver cancer.

Hepatocellular carcinoma (HCC) results from the cumulative effects of deregulated tumor suppressor genes and oncogenes. The tumor suppressor and oncogenes commonly affected include growth factors, receptors and their downstream signaling pathway components. The overexpression of transforming growth factor alpha (TGF-alpha) and the inhibition of TGF-beta signaling are especially common in human liver cancer.

Induction of p53 renders ATM-deficient mice refractory to hepatocarcinogenesis.

Background & Aims: p53 Mutations are very common in human hepatocellular carcinoma, and induction of hepatic p53 expression causes lysis of implanted hepatoblastoma cells in a chimeric mouse. Ataxia Telangiectasia Mutated (ATM) kinase senses DNA strand breaks and induces p53. Our aims were to establish whether ATM deficiency alters the carcinogenic response of hepatocytes to diethylnitrosamine (DEN).

Relationships between deficits in tissue mass and transcriptional programs after partial hepatectomy in mice.

Liver regeneration after two-thirds partial hepatectomy (2/3 PH) results in synchronized proliferation of hepatocytes and rapid restoration of liver mass. Understanding the mechanisms that regulate this process has both biological and clinical importance. Using cDNA microarray analysis, we investigated whether gene activation after 2/3 PH is specifically related to liver growth and hepatocyte proliferation.

Distinct Nrf1/2-independent mechanisms mediate As 3+-induced glutamate-cysteine ligase subunit gene expression in murine hepatocytes.

Trivalent arsenite (As(3+)) is a known human carcinogen that is also capable of inducing apoptotic cell death. Increased production of reactive oxygen species is thought to contribute to both the carcinogenic and the cytotoxic effects of As(3+). Glutathione (GSH) constitutes a vital cellular defense mechanism against oxidative stress.

Upregulation of the NADPH oxidase NOX4 by TGF-beta in hepatocytes is required for its pro-apoptotic activity.

Background/aims: The transforming growth factor-beta (TGF-beta) induces apoptosis in hepatocytes through an oxidative stress process. Here, we have analyzed the role of different NADPH oxidase isoforms in the intracellular signalling induced by TGF-beta in hepatocytes, to later explore whether this mechanism is altered in liver tumor cells.

Methods: Primary cultures of rat and human hepatocytes, HepG2 and Hep3B cells were used in in vitro studies to analyze the TGF-beta response.