Hepatocyte Replication Research Articles

Liver regeneration after injury: Mechanisms, cellular interactions and therapeutic innovations.

The liver possesses a distinctive capacity for regeneration within the human body. Under normal circumstances, liver cells replicate themselves to maintain liver function. Compensatory replication of healthy hepatocytes is sufficient for the regeneration after acute liver injuries. In the late stage of chronic liver damage, a large number of hepatocytes die and hepatocyte replication is blocked. Liver regeneration has more complex mechanisms, such as the transdifferentiation between cell types or hepatic progenitor cells mediated. Dysregulation of liver regeneration causes severe chronic liver disease. Gaining a more comprehensive understanding of liver regeneration mechanisms would facilitate the advancement of efficient therapeutic approaches. This review provides an overview of the signalling pathways linked to different aspects of liver regeneration in various liver diseases. Moreover, new knowledge on cellular interactions during the regenerative process is also presented. Finally, this paper explores the potential applications of new technologies, such as nanotechnology, stem cell transplantation and organoids, in liver regeneration after injury, offering fresh perspectives on treating liver disease.

Biological effects of exposure to copper nanoparticles: markers of exposure

Introduction. Aerosol nanoparticles at operating metallurgical plants are potent of the significant risk factor that needs to be studied.
 The purpose of the work was to study biological effects of exposure to copper nanoparticles compared to microparticles and identify potential markers of the exposure.
 Materials and methods. Two experimental groups of rats, twelve animals each, were subchronically exposed to copper-containing nanoparticles and microparticles injected intraperitoneally. Changes in their biochemical parameters, tissues, and organs were then compared to those in the control rats administered with deionized water. During periodic medical examinations of workers occupationally exposed to copper-containing aerosols with different particle size distribution, additional laboratory and instrumental methods of testing were used to identify possible exposure effects to health manifested by changes in biochemical parameters.
 Results. The experimental study showed that in liver, the exposure to copper nanoparticles, compared to microparticles, induced a more significant inhibition of replication of hepatocytes in regeneration, as demonstrated by the number of binuclear cells, and an increase in the number of Kupffer cells (tissue macrophages), while in kidney, it caused a more pronounced convoluted tubule brush border loss. The exposure to both micro- and nano-sized copper particles was found to induce pathological changes in neurons of the ganglionic layer of the cortex and basal nuclei. Test results showed a significant increase in the blood concentration of ceruloplasmin in the core personnel of the metallurgical plant following the exposure to copper aerosols rich in nanoparticles.
 Limitations. The assessment of the results of the impact of copper nanoparticles in the composition of the aerosol on the health of 224 employees of the enterprise and the results of the experiment obtained on 36 animals corresponded to the current social and ethical standards and norms.
 Conclusion. Specifics of the exposure to nanoparticles require a revision of approaches to regulating aerosols with account for particle size distribution.

The Protection Conferred by HSD17B13 rs72613567 on Hepatic Fibrosis Is Likely Mediated by Lowering Ballooning and Portal Inflammation

The Protection Conferred by HSD17B13 rs72613567 on Hepatic Fibrosis Is Likely Mediated by Lowering Ballooning and Portal Inflammation

Induced Liver Regeneration Enhances CRISPR/Cas9-Mediated Gene Repair in Tyrosinemia Type 1.

The efficiency of gene repair by homologous recombination in the liver is enhanced by CRISP/Cas9 incision near the mutation. In this study, we explored interventions designed to further enhance in vivo hepatocyte gene repair in a model of hereditary tyrosinemia. A two-AAV system was employed: one virus carried a Staphylococcus pyogenes Cas9 (SpCas9) expression cassette and the other harbored a U6 promoter-driven sgRNA and a fragment of fumarylacetoacetate hydrolase (Fah) genomic DNA as the homologous recombination donor. In neonatal mice, a gene correction frequency of ∼10.8% of hepatocytes was achieved. The efficiency in adult mice was significantly lower at ∼1.6%. To determine whether hepatocyte replication could enhance the targeting frequency, cell division was induced with thyroid hormone T3. This more than doubled the gene correction efficiency to 3.5% (p < 0.005). To determine whether SpCas9 delivery was rate limiting, the gene repair AAV was administered to SpCas9 transgenic mice. However, this did not significantly enhance gene repair. Finally, we tested whether the Fanconi anemia (FA) DNA repair pathway was important in hepatocyte gene repair. Gene correction frequencies were significantly lower in neonatal mice lacking the FA complementation group A (Fanca) gene. Taken together, we conclude that pharmacological induction of hepatocyte replication along with manipulation of DNA repair pathways could be a useful strategy for enhancing in vivo gene correction.

Elimination of Wnt Secretion from Hepatic Stellate Cells Impairs Hepatocyte Proliferation After Partial Hepatectomy

Wnt‐dependent β‐catenin activation contributes to hepatocyte proliferation following 2/3 partial hepatectomy (PH) through regulation of Cyclin‐D1 (Ccnd1) expression, as we have previously shown using β‐catenin or Wnt co‐receptors, low‐density lipoprotein receptor‐related protein 5–6, conditional knockouts (KO). However, given the redundancy between the 19 mammalian Wnt proteins and various cell sources for Wnt secretion, the precise mechanisms of Wnt signaling in liver regeneration (LR) are not completely understood. Recently, using endothelial cell (EC)‐specific deletion of Wntless (Wls), a cargo receptor required for Wnt secretion, we have reported that sinusoidal ECs secrete Wnt2 and Wnt9b to activate β‐catenin in hepatocytes and enhance Ccnd1 expression, which is indispensable for normal and optimal proliferation of hepatocytes during LR after PH. Alternatively, conditional deletion of Wls in hepatocytes or cholangiocytes did not impact LR, whereas Wls deletion in macrophages only marginally affected LR post‐PH. Here, to investigate the roles for hepatic stellate cell (HSC)‐secreted Wnts in LR, we characterize the HSC‐Wls‐KO, generated by interbreeding Wls‐floxed and Lecithin Retinol Acyl Transferase (LRAT)‐driven Cre (Lrat‐Cre) transgenic mice. HSC‐Wls‐KO mice showed no effect on liver weight or β‐catenin‐dependent pericentral gene expression at baseline. However, hepatocyte‐specific CCND1 protein normally evident in midzonal hepatocytes, was diminished in baseline KO liver as also evident by WB, whereas Ccnd1 expression was unaltered as seen by RNA‐seq and qPCR, suggesting posttranslational regulation. No difference in CCND1 protein was seen in the non‐parenchymal cells of the KO livers when compared to WT. After PH, HSC‐Wls‐KO showed modest decrease in gene expression of Ccnd1 at only 24 hour (h) post‐PH as compared to WT but comparable levels between the two groups were seen at 40h and 72h. While similiar PCNA+ staining in hepatocytes was observed at 40–72h post‐PH in HSC‐Wls‐KO and WT, HSC‐Wls‐KO displayed significantly diminished BrdU+ or pHH3+ hepatocytes at 40h, which rebounded by 72h, suggesting delayed regeneration due to the impaired hepatocyte replication.ConclusionAt baseline, Wnt ligands secreted by HSCs are essential for CCND1 protein expression in midzonal hepatocytes but not for pericentral zonation. Following PH, HSCs‐derived Wnts also contribute to normal Ccnd1 expression and hepatocyte mitosis.Support or Funding InformationThis work was supported by NIH grants 1R01DK62277, 1R01DK100287, R01CA204586 and Endowed Chair for Experimental Pathology to S.P.M., and by NIH grant 1P30DK120531‐01 to Pittsburgh Liver Research Center (PLRC) and by PLRC Pilot &amp; Feasibility grant PF 2019‐05 to S.K.

Pregnancy facilitates maternal liver regeneration after partial hepatectomy.

Liver resection induces robust liver regrowth or regeneration to compensate for the lost tissue mass. In a clinical setting, pregnant women may need liver resection without terminating pregnancy in some cases. However, how pregnancy affects maternal liver regeneration remains elusive. We performed 70% partial hepatectomy (PH) in nonpregnant mice and gestation day 14 mice, and histologically and molecularly compared their liver regrowth during the next 4 days. We found that compared with the nonpregnant state, pregnancy altered the molecular programs driving hepatocyte replication, indicated by enhanced activities of epidermal growth factor receptor and STAT5A, reduced activities of cMet and p70S6K, decreased production of IL-6, TNFα, and hepatocyte growth factor, suppressed cyclin D1 expression, increased cyclin A1 expression, and early activated cyclin A2 expression. As a result, pregnancy allowed the remnant hepatocytes to enter the cell cycle at least 12 h earlier, increased hepatic fat accumulation, and enhanced hepatocyte mitosis. Consequently, pregnancy ameliorated maternal liver regeneration following PH. In addition, a report showed that maternal liver regrowth after PH is driven mainly by hepatocyte hypertrophy rather than hyperplasia during the second half of gestation in young adult mice. In contrast, we demonstrate that maternal liver relies mainly on hepatocyte hyperplasia instead of hypertrophy to restore the lost mass after PH. Overall, we demonstrate that pregnancy facilitates maternal liver regeneration likely via triggering an early onset of hepatocyte replication, accumulating excessive liver fat, and promoting hepatocyte mitosis. The results from our current studies enable us to gain more insights into how maternal liver regeneration progresses during gestation.NEW & NOTEWORTHY We demonstrate that pregnancy may generate positive effects on maternal liver regeneration following partial hepatectomy, which are manifested by early entry of the cell cycle of remnant hepatocytes, increased hepatic fat accumulation, enhanced hepatocyte mitosis, and overall accelerated liver regrowth.

Different strategies in the liver regeneration processes. Numerical experiments on the mathematical model

It is considered the generalized mathematical model which describes the processes of maintaining / restoring dynamic homeostasis (regeneration) of the liver and obviously depends on the control parameters. The model is a system of discrete controlled equations of the Lotka – Volterra type with transitions. These equations describe the controlled competitive dynamics of liver cell populations’ (hepatic lobules) various types in their various states and controlled competitive transitions between types and states. To develop this model there were accepted such assumptions: homogeneous approximation; independence of biological processes; small toxic factors. In the mathematical model the process of the liver regeneration occurs due to hyperplasia processes, replication, polyplodia and division of binuclear hepatocytes into mononuclear and controlled apoptosis. All these processes are necessary for adequate modeling of the liver regeneration. For example, single and constant toxic functions show that the above processes are not able to cope with the toxic factors that are accumulated in the body. The process of restoring the body’s functional state requires the non-trivial strategy of the liver regeneration. Numerical calculations revealed that the mathematical model corresponds to biological processes for different strategies of the liver regeneration. Based on the calculations in the case of partial hapatectomy it is concluded that the mixed strategy of regeneration should be used for the regeneration process. Henceforward it is planned to extend the mathematical model in the case of the liver regeneration, which occurs under the influence of strong toxins, that is, using the stem cells and fibrosis. It is also supposed to justify the principles and criteria for optimal regulation of the processes of maintaining / restoring liver’s dynamic homeostasis.

Interleukin 22 in Liver Injury, Inflammation and Cancer.

Interleukin 22(IL-22), a member of the IL-10 cytokine family and is an emerging CD4+Th cytokine that plays an important role in anti-microbial defense, homeostasis and tissue repair. We are interested in IL-22 as it has the double function of suppressing or encouraging inflammation in various disease models including hepatic inflammation. As a survival factor for hepatocytes, IL-22 plays a protective role in many kinds of liver diseases, such as hepatitis, liver fibrosis, or hepatocellular carcinoma (HCC) by binding to the receptors IL-22R1 and IL-10R2. Overexpression of IL-22 reduces liver fibrosis by attenuating the activation of hepatic stellate cell (the main cell types involved in hepatic fibrosis), and down-regulating the levels of inflammatory cytokines. Administration of exogenous IL-22 increases the replication of hepatocytes by inhibiting cell apoptosis and promoting mitosis, ultimately plays a contributing role in liver regeneration. Furthermore, treatment with IL-22 activates hepatic signal transducer and activator of transcription 3 (STAT3), ameliorates hepatic oxidative stress and alcoholic fatty liver, effectively alleviate the liver damage caused by alcohol and toxicant. In conclusion, the hepatoprotective functions and liver regeneration promoting effect of IL-22 suggests the therapeutic potential of IL-22 in the treatment of human hepatic diseases.

Transforming growth factor-β signaling confers hepatic stellate cells progenitor features after partial hepatectomy.

Liver regeneration involves not only hepatocyte replication but progenitor aggregation and scarring. Partial hepatectomy (PH), an established model for liver regeneration, reactivates transforming growth factor-β (TGF-β) signaling. Hepatic stellate cells (HSCs) are primarily responding cells for TGF-β and resident in stem cell niche. In the current study, PH mice were treated with SB-431542, an inhibitor of TGF-β Type I receptor, aiming to address the role of TGF-β signaling on the fate determination of HSCs during liver regeneration. After PH, control mice exhibited HSCs activation, progenitor cells accumulation, and a fraction of HSCs acquired the phenotype of hepatocyte or cholangiocyte. Blocking TGF-β signaling delayed proliferation, impaired progenitor response, and scarring repair. In SB-431542 group, merely no HSCs were found coexpressed progenitor makers, such as SOX9 and AFP. Inhibition of TGF-β pathway disturbed the epithelial-mesenchymal transitions and diminished the nuclear accumulation of β-catenin as well as the expression of cytochrome P450 2E1 in HSC during liver regeneration. We identify a key role of TGF-β signaling on promoting HSC transition, which subsequently becomes progenitor for generating liver epithelial cells after PH. This process might interact with an acknowledged stem cell function signaling, Wnt/β-catenin.

The Impact of Mevastatin on HCV Replication and Autophagy of Non-Transformed HCV Replicon Hepatocytes Is Influenced by the Extracellular Lipid Uptake.

Statins efficiently inhibit cholesterol synthesis by blocking 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase in the mevalonate pathway. However, the effect of statins on intracellular cholesterol is partially counterbalanced by a consequent increased uptake of extracellular lipid sources. Hepatitis C virus (HCV) infection induces intracellular accumulation of cholesterol by promoting both new synthesis and uptake of circulating lipoproteins, which is required for HCV replication and release. Hepatocytes respond to the increase in intracellular cholesterol levels by inducing lipophagy, a selective type of autophagy mediating the degradation of lipid deposits within lysosomes. In a cellular system of HCV replication based on HuH7 hepatoma cells, statin treatment was shown to be sufficient to decrease intracellular cholesterol, which is accompanied by reduced HCV replication and decreased lipophagy, and has no apparent impact on endocytosis-mediated cholesterol uptake. To understand whether these results were influenced by an altered response of cholesterol influx in hepatoma cells, we analyzed the effect of statins in non-transformed murine hepatocytes (MMHD3) harboring subgenomic HCV replicons. Notably, we found that total amount of cholesterol is increased in MMHD3 cells upon mevastatin treatment, which is associated with increased HCV replication and lipophagy. Conversely, mevastatin is able to reduce cholesterol amounts only when cells are grown in the presence of delipidated serum to prevent extracellular lipid uptake. Under this condition, HCV replication is reduced and autophagy flux is severely impaired. Altogether, these results indicate that both de novo synthesis and extracellular uptake have to be targeted in non-transformed hepatocytes in order to decrease intracellular cholesterol levels and consequently limit HCV replication.

Xenogeneic Heterotopic Auxiliary Liver transplantation (XHALT) promotes native liver regeneration in a Post-Hepatectomy Liver failure model.

The liver’s regenerative capacity is unique, but too small a segment can overwhelm its ability to simultaneously regenerate and support the host, resulting in liver dysfunction and death. Here we tested a temporary Xenogeneic Heterotopic Auxiliary Liver Transplant (XHALT) from Gal-KO miniature swine in a baboon model of Post-Hepatectomy Liver Failure (PHLF) by 90%- hepatectomy. Immunosuppression consisted of CVF, ATG, FK 506 and steroids. 90%-hepatectomized animals died within 4–5 days with the clinical picture of PHLF, (high LFTs and bilirubin, ascites, encephalopathy and coagulopathy). The 10% remnants had macroscopic and histological evidence of severe steatosis and absence of hepatocyte replication. In contrast, the addition of XHALT prolonged survival up to 11 days, with the cause of death being sepsis, rather than liver failure. The remnant liver appeared grossly normal, and on histology, there was no evidence of fatty infiltration, but there was pronounced Ki-67 staining. In conclusion, temporary auxiliary xenografts have the potential to support a small for size liver graft while it grows to adequate size or provide an opportunity for organ recovery in acute liver failure.

Hepatic NF-kB-inducing kinase (NIK) suppresses mouse liver regeneration in acute and chronic liver diseases.

Reparative hepatocyte replication is impaired in chronic liver disease, contributing to disease progression; however, the underlying mechanism remains elusive. Here, we identify Map3k14 (also known as NIK) and its substrate Chuk (also called IKKα) as unrecognized suppressors of hepatocyte replication. Chronic liver disease is associated with aberrant activation of hepatic NIK pathways. We found that hepatocyte-specific deletion of Map3k14 or Chuk substantially accelerated mouse hepatocyte proliferation and liver regeneration following partial-hepatectomy. Hepatotoxin treatment or high fat diet feeding inhibited the ability of partial-hepatectomy to stimulate hepatocyte replication; remarkably, inactivation of hepatic NIK markedly increased reparative hepatocyte proliferation under these liver disease conditions. Mechanistically, NIK and IKKα suppressed the mitogenic JAK2/STAT3 pathway, thereby inhibiting cell cycle progression. Our data suggest that hepatic NIK and IKKα act as rheostats for liver regeneration by restraining overgrowth. Pathological activation of hepatic NIK or IKKα likely blocks hepatocyte replication, contributing to liver disease progression.

ZBTB20 regulates EGFR expression and hepatocyte proliferation in mouse liver regeneration

Liver has a unique regenerative capacity, however, its regulatory mechanism is not fully defined. We have established the zinc-finger protein ZBTB20 as a key transcriptional repressor for alpha-fetoprotein (AFP) gene in liver. As a marker of hepatic differentiation, AFP expression is closely associated with hepatocyte proliferation. Unexpectedly, here we showed that ZBTB20 acts as a positive regulator of hepatic replication and is required for efficient liver regeneration. The mice specifically lacking ZBTB20 in hepatocytes exhibited a remarkable defect in liver regeneration after partial hepatectomy, which was characterized by impaired hepatocyte proliferation along with delayed cyclin D1 induction and diminished AKT activation. Furthermore, we found that epithelial growth factor receptor (EGFR) expression was dramatically reduced in the liver in the absence of ZBTB20, thereby substantially attenuating the activation of EGFR signaling pathway in regenerating liver. Adenovirus-mediated EGFR overexpression in ZBTB20-deficient hepatocytes could largely restore AKT activation in response to EGFR ligands in vitro, as well as hepatocyte replication in liver regeneration. Furthermore, ZBTB20 overexpression could significantly restore hepatic EGFR expression and cell proliferation after hepatectomy in ZBTB20-deficient liver. Taken together, our data point to ZBTB20 as a critical regulator of EGFR expression and hepatocyte proliferation in mouse liver regeneration, and may serve as a potential therapeutic target in clinical settings of liver regeneration.

Cholangiocytes: No Longer Cinderellas to the Hepatic Regenerative Response

Biliary ductal cells proliferate from the portal areas of chronically damaged livers, but their significance to regeneration has been controversial. A recent article in Nature by Raven etal. (2017) now shows that blocking hepatocyte replication is essential for the hepatic differentiation of ductular cells after liver damage.

Selective targeting of lysyl oxidase-like 2 (LOXL2) suppresses hepatic fibrosis progression and accelerates its reversal

Background/AimsWe studied the role of lysyl oxidase-like 2 (LOXL2) in collagen crosslinking and hepatic progenitor cell (HPC) differentiation, and the therapeutic efficacy of a LOXL2-blocking monoclonal antibody on liver fibrosis...

MicroRNA-141 Targets Sirt1 and Inhibits Autophagy to Reduce HBV Replication

Background/Aims: About 400 million individuals are chronically infected with hepatitis B virus, at high risk of developing liver cirrhosis and hepatocellular carcinoma. Recent studies have demonstrated an interaction between hepatitis B virus replication and autophagy activity of hepatocytes. In the present study, we aimed to investigate the role of miR-141 in regulating autophagy and hepatitis B virus replication. Methods: The expression of HBV-DNA, miR-141 and Sirt1 mRNA was determined by quantitative real-time PCR analysis. The expression of HBsAg and HBeAg was determined by ELISA. Western blotting was performed to detect protein expression. The LC3 puncta was determined by immunofluorescence. To test whether miR-141 directly regulate the expression level of Sirt1 mRNA, dual-luciferase reporter gene assay was performed. Results: In vitro studies showed that miR-141 mimic inhibited the autophagic response, hepatitis B virus and the expression of Sirt1 in hepatocytes. And transfection with miR-141 inhibitor enhanced autophagic response and Sirt1 expression. The autophagy induced by overexpression of Sirt1 was inhibited by miR-141 mimic. In addition, miR-141 mimic also decreased the expression of Sirt1 mRNA. Sirt1 was predicted as a potential miR-141 target by bioinformatic analysis of its 3'-UTR, and confirmed by luciferase reporter assays which analyzing the interaction of miR-141 with the wild- type or the mutated Sirt1 3’-UTR. Conclusion: We have therefore demonstrated a role of miR-141 in regulating autophagy-mediated hepatitis B virus inhibition by targeting Sirt1, and may provide potential targets for drug development.

Inflammasomes Coordinate Pyroptosis and Natural Killer Cell Cytotoxicity to Clear Infection by a Ubiquitous Environmental Bacterium

Defective neutrophils in patients with chronic granulomatous disease (CGD) cause susceptibility to extracellular and intracellular infections. Microbes must first be ejected from intracellular niches to expose them to neutrophil attack, so we hypothesized that inflammasomes detect certain CGD pathogens upstream of neutrophil killing. Here, we identified one such ubiquitous environmental bacterium, Chromobacterium violaceum, whose extreme virulence was fully counteracted by the NLRC4 inflammasome. Caspase-1 protected via two parallel pathways that eliminated intracellular replication niches. Pyroptosis was the primary bacterial clearance mechanism in the spleen, but both pyroptosis and interleukin-18 (IL-18)-driven natural killer (NK) cell responses were required for liver defense. NK cells cleared hepatocyte replication niches via perforin-dependent cytotoxicity, whereas interferon-γ was not required. These insights suggested a therapeutic approach: exogenous IL-18 restored perforin-dependent cytotoxicity during infection by the inflammasome-evasive bacterium Listeria monocytogenes. Therefore, inflammasomes can trigger complementary programmed cell death mechanisms, directing sterilizing immunity against intracellular bacterial pathogens.

Abstract 810: Non-genotoxic hepatocarcinogens induce growth and anti-apoptotic pathways in hepatocytes via mesenchymal cytokines

Abstract Purpose of study. Chemical carcinogens are categorized as either genotoxic or non-genotoxic. While most genotoxic carcinogens are known to interfere with DNA, the mode of action of non-genotoxic carcinogens (NGC) is far from being understood. Many steroid hormones act as NGC and account for cancer of the breast, prostate, or other organs. As ligands of nuclear receptors hormones induce growth in target tissues and support the outgrowth of mutated cells to malignancy. An almost identical principle is underlying the action of NGC producing liver tumors in long-term rodent bioassays. This group of compounds comprises drugs prescribed to hundred-thousands of humans, like hypolipidemic and antidiabetic drugs, or synthetic steroid hormones. A thorough knowledge of the mode of action of NGC is of utmost importance in order to estimate the risk of exposed humans. Conventional notion regards the action of NGC an autonomous process largely confined to parenchymal cells. Here, we aim to elucidate the role of the hepatic mesenchyme for the action of two prototypical NGC, phenobarbital (PB), an anti-epileptic drug, and cyproterone acetate (CPA), a gestagen used in contraceptive pills. Experimental procedures. Mesenchymal liver cells (MC) and hepatocytes (HC) were isolated from control and PB/CPA-treated rat livers by collagenase perfusion and subsequent low-speed centrifugation. Transcriptomics was performed by oligo-array analyses (Affymetrix). Cytokine levels were determined by ELISA. Nuclear translocation of NFkB was shown by immunoblotts of nuclear extracts and by reporter gene assay. Results: Analyses by oligo-arrays revealed that PB and CPA altered the transcriptome profiles of HC and MC. In PB-treated MC, there were deregulations of pro-inflammatory cytokines and chemokines of the TNF-, CCL- and CXCL-family. PB treatment in vivo or in vitro elevated the production and release of tumor necrosis factor alpha (TNFalpha)from MC. The secretome of PB-treated MC induced in HC a pro-inflammatory reaction and nuclear translocation of nuclear factor-kB (NFkB), an effect also observed with recombinant TNFalpha. Both, TNFalpha and the secretome of PB-treated MC, protected HC from pro-apoptotic stimuli. Transcriptome analyses of CPA-treated MC revealed enhanced expression not only of pro-inflammatory cytokines but also of several potent growth factors. Accordingly, the supernatant of CPA-treated MC enhanced considerably the DNA replication of preneoplastic hepatocytes. Conclusion: PB and CPA appear to alter considerably the function of the hepatic mesenchyme. The resulting release of cytokines induces growth and/or activates anti-apoptotic pathways in HC which may contribute to the tumor promoting activity of these compounds. Thus, epithelial-mesenchymal interactions appear crucial in NGC-driven hepatocarcinogenesis. Project MARCAR, funded by IMI JU under grant agreement Nr 115001. Citation Format: Bettina Grasl-Kraupp, Teresa Riegler, Marzieh Nejabat, Jakob Paur, Johannes Eichner, Michael Roemer, Andreas Zell, Rolf Schulte-Hermann, Wolfgang Huber. Non-genotoxic hepatocarcinogens induce growth and anti-apoptotic pathways in hepatocytes via mesenchymal cytokines. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 810. doi:10.1158/1538-7445.AM2015-810

Pregnane X Receptor-Humanized Mice Recapitulate Gender Differences in Ethanol Metabolism but Not Hepatotoxicity.

Both human and rodent females are more susceptible to developing alcoholic liver disease following chronic ethanol (EtOH) ingestion. However, little is known about the relative effects of acute EtOH exposure on hepatotoxicity in female versus male mice. The nuclear receptor pregnane X receptor (PXR; NR1I2) is a broad-specificity sensor with species-specific responses to toxic agents. To examine the effects of the human PXR on acute EtOH toxicity, the responses of male and female PXR-humanized (hPXR) transgenic mice administered oral binge EtOH (4.5 g/kg) were analyzed. Basal differences were observed between hPXR males and females in which females expressed higher levels of two principal enzymes responsible for EtOH metabolism, alcohol dehydrogenase 1 and aldehyde dehydrogenase 2, and two key mediators of hepatocyte replication and repair, cyclin D1 and proliferating cell nuclear antigen. EtOH ingestion upregulated hepatic estrogen receptor α, cyclin D1, and CYP2E1 in both genders, but differentially altered lipid and EtOH metabolism. Consistent with higher basal levels of EtOH-metabolizing enzymes, blood EtOH was more rapidly cleared in hPXR females. These factors combined to provide greater protection against EtOH-induced liver injury in female hPXR mice, as revealed by markers for liver damage, lipid peroxidation, and endoplasmic reticulum stress. These results indicate that female hPXR mice are less susceptible to acute binge EtOH-induced hepatotoxicity than their male counterparts, due at least in part to the relative suppression of cellular stress and enhanced expression of enzymes involved in both EtOH metabolism and hepatocyte proliferation and repair in hPXR females.

Role of liver progenitors in liver regeneration.

During massive liver injury and hepatocyte loss, the intrinsic regenerative capacity of the liver by replication of resident hepatocytes is overwhelmed. Treatment of this condition depends on the cause of liver injury, though in many cases liver transplantation (LT) remains the only curative option. LT for end stage chronic and acute liver diseases is hampered by shortage of donor organs and requires immunosuppression. Hepatocyte transplantation is limited by yet unresolved technical difficulties. Since currently no treatment is available to facilitate liver regeneration directly, therapies involving the use of resident liver stem or progenitor cells (LPCs) or non-liver stem cells are coming to fore. LPCs are quiescent in the healthy liver, but may be activated under conditions where the regenerative capacity of mature hepatocytes is severely impaired. Non-liver stem cells include embryonic stem cells (ES cells) and mesenchymal stem cells (MSCs). In the first section, we aim to provide an overview of the role of putative cytokines, growth factors, mitogens and hormones in regulating LPC response and briefly discuss the prognostic value of the LPC response in clinical practice. In the latter section, we will highlight the role of other (non-liver) stem cells in transplantation and discuss advantages and disadvantages of ES cells, induced pluripotent stem cells (iPS), as well as MSCs.