A novel treatment strategy utilizing panobinostat for high-risk and treatment-refractory hepatoblastoma

BACKGROUND & AIMS

Patients with metastatic, treatment-refractory, and relapsed hepatoblastoma (HB) have survival rates of less than 50% due to limited treatment options. To develop new therapeutic strategies for these patients, our laboratory has developed a preclinical testing pipeline. Given that histone deacetylase (HDAC) inhibition has been proposed for HB, we hypothesized that we could find an effective combination treatment strategy utilizing HDAC inhibition.

METHODS

RNA sequencing, microarray, NanoString, and immunohistochemistry data of patient HB samples were analyzed for HDAC class expression. Patient-derived spheroids (PDSp) were used to screen combination chemotherapy with an HDAC inhibitor, panobinostat. Patient-derived xenograft (PDX) mouse models were developed and treated with the combination therapy that showed the highest efficacy in the PDSp drug screen.

RESULTS

HDAC RNA and protein expression were elevated in HB tumors compared to normal livers. Panobinostat (IC50 of 0.013-0.059 μM) showed strong in vitro effects and was associated with lower cell viability than other HDAC inhibitors. PDSp demonstrated the highest level of cell death with combination treatment of vincristine/irinotecan/panobinostat (VIP). All four models responded to VIP therapy with a decrease in tumor size compared to placebo. After 6 weeks of treatment, two models demonstrated necrotic cell death, with lower Ki67 expression, decreased serum alpha fetoprotein and reduced tumor burden compared to paired VI- and placebo-treated groups.

CONCLUSIONS

Utilizing a preclinical HB pipeline, we demonstrate that panobinostat in combination with VI chemotherapy can induce an effective tumor response in models developed from patients with high-risk, relapsed, and treatment-refractory HB.

IMPACT AND IMPLICATIONS

Patients with treatment-refractory hepatoblastoma have limited treatment options with survival rates of less than 50%. Our manuscript demonstrates that combination therapy with vincristine, irinotecan, and panobinostat reduces the size of high-risk, relapsed, and treatment-refractory tumors. With this work we provide preclinical evidence to support utilizing this combination therapy as an arm in future clinical trials.

A humanized mouse model for adeno-associated viral gene therapy

Clinical translation of AAV-mediated gene therapy requires preclinical development across different experimental models, often confounded by variable transduction efficiency. Here, we describe a human liver chimeric transgene-free Il2rg-/-/Rag2-/-/Fah-/-/Aavr-/- (TIRFA) mouse model overcoming this translational roadblock, by combining liver humanization with AAV receptor (AAVR) ablation, rendering murine cells impermissive to AAV transduction. Using human liver chimeric TIRFA mice, we demonstrate increased transduction of clinically used AAV serotypes in primary human hepatocytes compared to humanized mice with wild-type AAVR. Further, we demonstrate AAV transduction in human teratoma-derived primary cells and liver cancer tissue, displaying the versatility of the humanized TIRFA mouse. From a mechanistic perspective, our results support the notion that AAVR functions as both an entry receptor and an intracellular receptor essential for transduction. The TIRFA mouse should allow prediction of AAV gene transfer efficiency and the study of AAV vector biology in a preclinical human setting.

Circadian dysfunction induces NAFLD-related human liver cancer in a mouse model

BACKGROUND & AIMS

Chronic circadian dysfunction increases the risk of non-alcoholic fatty liver disease (NAFLD)-related hepatocellular carcinoma (HCC), but the underlying mechanisms and direct relevance to human HCC have not been established. In this study, we aimed to determine whether chronic circadian dysregulation can drive NAFLD-related carcinogenesis from human hepatocytes and human HCC progression.

METHODS

Chronic jet lag of mice with humanized livers induces spontaneous NAFLD-related HCCs from human hepatocytes. The clinical relevance of this model was analysed by biomarker, pathological/histological, genetic, RNA sequencing, metabolomic, and integrated bioinformatic analyses.

RESULTS

Circadian dysfunction induces glucose intolerance, NAFLD-associated human HCCs, and human HCC metastasis independent of diet in a humanized mouse model. The deregulated transcriptomes in necrotic-inflammatory humanized livers and HCCs bear a striking resemblance to those of human non-alcoholic steatohepatitis (NASH), cirrhosis, and HCC. Stable circadian entrainment of hosts rhythmically paces NASH and HCC transcriptomes to decrease HCC incidence and prevent HCC metastasis. Circadian disruption directly reprogrammes NASH and HCC transcriptomes to drive a rapid progression from hepatocarcinogenesis to HCC metastasis. Human hepatocyte and tumour transcripts are clearly distinguishable from mouse transcripts in non-parenchymal cells and tumour stroma, and display dynamic changes in metabolism, inflammation, angiogenesis, and oncogenic signalling in NASH, progressing to hepatocyte malignant transformation and immunosuppressive tumour stroma in HCCs. Metabolomic analysis defines specific bile acids as prognostic biomarkers that change dynamically during hepatocarcinogenesis and in response to circadian disruption at all disease stages.

CONCLUSION

Chronic circadian dysfunction is independently carcinogenic to human hepatocytes. Mice with humanized livers provide a powerful preclinical model for studying the impact of the necrotic-inflammatory liver environment and neuroendocrine circadian dysfunction on hepatocarcinogenesis and anti-HCC therapy.

IMPACT AND IMPLICATIONS

Human epidemiological studies have linked chronic circadian dysfunction to increased hepatocellular carcinoma (HCC) risk, but direct evidence that circadian dysfunction is a human carcinogen has not been established. Here we show that circadian dysfunction induces non-alcoholic steatohepatitis (NASH)-related carcinogenesis from human hepatocytes in a murine humanized liver model, following the same molecular and pathologic pathways observed in human patients. The gene expression signatures of humanized HCC transcriptomes from circadian-disrupted mice closely match those of human HCC with the poorest prognostic outcomes, while those from stably circadian entrained mice match those from human HCC with the best prognostic outcomes. Our studies establish a new model for defining the mechanism of NASH-related HCC and highlight the importance of circadian biology in HCC prevention and treatment.

In vivo expansion of gene-targeted hepatocytes through transient inhibition of an essential gene

Homology Directed Repair (HDR)-based genome editing is an approach that could permanently correct a broad range of genetic diseases. However, its utility is limited by inefficient and imprecise DNA repair mechanisms in terminally differentiated tissues. Here, we tested "Repair Drive", a novel method for improving targeted gene insertion in the liver by selectively expanding correctly repaired hepatocytes in vivo. Our system consists of transient conditioning of the liver by knocking down an essential gene, and delivery of an untargetable version of the essential gene in cis with a therapeutic transgene. We show that Repair Drive dramatically increases the percentage of correctly targeted hepatocytes, up to 25%. This resulted in a five-fold increased expression of a therapeutic transgene. Repair Drive was well-tolerated and did not induce toxicity or tumorigenesis in long term follow up. This approach will broaden the range of liver diseases that can be treated with somatic genome editing.

Rescue of glutaric aciduria type I in mice by liver-directed therapies

Glutaric aciduria type I (GA-1) is an inborn error of metabolism with a severe neurological phenotype caused by the deficiency of glutaryl-coenzyme A dehydrogenase (GCDH), the last enzyme of lysine catabolism. Current literature suggests that toxic catabolites in the brain are produced locally and do not cross the blood-brain barrier. In a series of experiments using knockout mice of the lysine catabolic pathway and liver cell transplantation, we uncovered that toxic GA-1 catabolites in the brain originated from the liver. Moreover, the characteristic brain and lethal phenotype of the GA-1 mouse model was rescued by two different liver-directed gene therapy approaches: Using an adeno-associated virus, we replaced the defective Gcdh gene or we prevented flux through the lysine degradation pathway by CRISPR deletion of the aminoadipate-semialdehyde synthase (Aass) gene. Our findings question the current pathophysiological understanding of GA-1 and reveal a targeted therapy for this devastating disorder.

The roles of Cyp1a2 and Cyp2d in pharmacokinetic profiles of serotonin and norepinephrine reuptake inhibitor duloxetine and its metabolites in mice

Duloxetine (DLX) is widely used to treat major depressive disorder. Little is known about the mechanistic basis for DLX-related adverse effects (e.g., liver injury). Human CYP1A2 and CYP2D6 mainly contributes to DLX metabolism, which was proposed to be involved in its adverse effects. Here, we investigated the roles of Cyp1a2 and Cyp2d on DLX pharmacokinetic profile and tissue distribution using a Cyp1a2 knockout (Cyp1a2-KO) mouse model together with a Cyp2d inhibitor (propranolol). Cyp1a2-KO has the few effects on the systematic exposure (area under the plasma concentration-time curve, AUC) and tissue disposition of DLX and its primary metabolites. Propranolol dramatically increased the AUCs of DLX by 3 folds and 1.5 folds in WT and Cyp1a2-KO mice, respectively. Meanwhile, Cyp2d inhibitor decreased the AUC of Cyp2d-involved DLX metabolites (e.g., M16). Mouse tissue distribution revealed that DLX and its major metabolites were the most abundant in kidney, followed by liver and lung with/without Cyp2d inhibitor. Cyp2d inhibitor significantly increased DLX levels in tissues (e.g., liver) in WT and KO mice and decreases the levels of M3, M15, M16 and M17, while it increased the levels of M4, M28 and M29 in tissues. Our findings indicated that Cyp2d play a fundamental role on DLX pharmacokinetic profile and tissue distribution in mice. Clinical studies suggested that CYP1A2 has more effects on DLX systemic exposure than CYP2D6. Further studies in liver humanized mice or clinical studies concerning CYP2D6 inhibitors-DLX interaction study could clarify the roles of CYP2D6 on DLX pharmacokinetics and toxicity in human.

Metabolism of a Selective Serotonin and Norepinephrine Reuptake Inhibitor Duloxetine in Liver Microsomes and Mice

Duloxetine (DLX) is a dual serotonin and norepinephrine reuptake inhibitor, widely used for the treatment of major depressive disorder. Although DLX has shown good efficacy and safety, serious adverse effects (e.g., liver injury) have been reported. The mechanisms associated with DLX-induced toxicity remain elusive. Drug metabolism plays critical roles in drug safety and efficacy. However, the metabolic profile of DLX in mice is not available, although mice serve as commonly used animal models for mechanistic studies of drug-induced adverse effects. Our study revealed 39 DLX metabolites in human/mouse liver microsomes and mice. Of note, 13 metabolites are novel, including five N-acetyl cysteine adducts and one reduced glutathione (GSH) adduct associated with DLX. Additionally, the species differences of certain metabolites were observed between human and mouse liver microsomes. CYP1A2 and CYP2D6 are primary enzymes responsible for the formation of DLX metabolites in liver microsomes, including DLX-GSH adducts. In summary, a total of 39 DLX metabolites were identified, and species differences were noticed in vitro. The roles of CYP450s in DLX metabolite formation were also verified using human recombinant cytochrome P450 (P450) enzymes and corresponding chemical inhibitors. Further studies are warranted to address the exact role of DLX metabolism in its adverse effects in vitro (e.g., human primary hepatocytes) and in vivo (e.g., Cyp1a2-null mice). SIGNIFICANCE STATEMENT: This current study systematically investigated Duloxetine (DLX) metabolism and bioactivation in liver microsomes and mice. This study provided a global view of DLX metabolism and bioactivation in liver microsomes and mice, which are very valuable to further elucidate the mechanistic study of DLX-related adverse effects and drug-drug interaction from metabolic aspects.

Targeting the Apoa1 locus for liver-directed gene therapy

Clinical application of somatic genome editing requires therapeutics that are generalizable to a broad range of patients. Targeted insertion of promoterless transgenes can ensure that edits are permanent and broadly applicable while minimizing risks of off-target integration. In the liver, the Albumin (Alb) locus is currently the only well-characterized site for promoterless transgene insertion. Here, we target the Apoa1 locus with adeno-associated viral (AAV) delivery of CRISPR-Cas9 and achieve rates of 6% to 16% of targeted hepatocytes, with no evidence of toxicity. We further show that the endogenous Apoa1 promoter can drive robust and sustained expression of therapeutic proteins, such as apolipoprotein E (APOE), dramatically reducing plasma lipids in a model of hypercholesterolemia. Finally, we demonstrate that Apoa1-targeted fumarylacetoacetate hydrolase (FAH) can correct and rescue the severe metabolic liver disease hereditary tyrosinemia type I. In summary, we identify and validate Apoa1 as a novel integration site that supports durable transgene expression in the liver for gene therapy applications.

A human liver chimeric mouse model for non-alcoholic fatty liver disease

Background & Aims

The accumulation of neutral lipids within hepatocytes underlies non-alcoholic fatty liver disease (NAFLD), which affects a quarter of the world's population and is associated with hepatitis, cirrhosis, and hepatocellular carcinoma. Despite insights gained from both human and animal studies, our understanding of NAFLD pathogenesis remains limited. To better study the molecular changes driving the condition we aimed to generate a humanised NAFLD mouse model.

Methods

We generated TIRF (transgene-free Il2rg ^-/-/Rag2 ^-/-/Fah ^-/-) mice, populated their livers with human hepatocytes, and fed them a Western-type diet for 12 weeks.

Results

Within the same chimeric liver, human hepatocytes developed pronounced steatosis whereas murine hepatocytes remained normal. Unbiased metabolomics and lipidomics revealed signatures of clinical NAFLD. Transcriptomic analyses showed that molecular responses diverged sharply between murine and human hepatocytes, demonstrating stark species differences in liver function. Regulatory network analysis indicated close agreement between our model and clinical NAFLD with respect to transcriptional control of cholesterol biosynthesis.

Conclusions

These NAFLD xenograft mice reveal an unexpected degree of evolutionary divergence in food metabolism and offer a physiologically relevant, experimentally tractable model for studying the pathogenic changes invoked by steatosis.

Lay summary

Fatty liver disease is an emerging health problem, and as there are no good experimental animal models, our understanding of the condition is poor. We here describe a novel humanised mouse system and compare it with clinical data. The results reveal that the human cells in the mouse liver develop fatty liver disease upon a Western-style fatty diet, whereas the mouse cells appear normal. The molecular signature (expression profiles) of the human cells are distinct from the mouse cells and metabolic analysis of the humanised livers mimic the ones observed in humans with fatty liver. This novel humanised mouse system can be used to study human fatty liver disease.

A hepatitis B virus transgenic mouse model with a conditional, recombinant, episomal genome

Background & Aims

Development of new and more effective therapies against hepatitis B virus (HBV) is limited by the lack of suitable small animal models. The HBV transgenic mouse model containing an integrated overlength 1.3-mer construct has yielded crucial insights, but this model unfortunately lacks covalently closed circular DNA (cccDNA), the episomal HBV transcriptional template, and cannot be cured given that HBV is integrated in every cell.

Methods

To solve these 2 problems, we generated a novel transgenic mouse (HBV1.1X), which generates an excisable circular HBV genome using Cre/LoxP technology. This model possesses a HBV1.1-mer cassette knocked into the ROSA26 locus and is designed for stable expression of viral proteins from birth, like the current HBV transgenic mouse model, before genomic excision with the introduction of Cre recombinase.

Results

We demonstrated induction of recombinant cccDNA (rcccDNA) formation via viral or transgenic Cre expression in HBV1.1X mice, and the ability to regulate HBsAg and HBc expression with Cre in mice. Tamoxifen-inducible Cre could markedly downregulate baseline HBsAg levels from the integrated HBV genome. To demonstrate clearance of HBV from HBV1.1X mice, we administered adenovirus expressing Cre, which permanently and significantly reduced HBsAg and core antigen levels in the murine liver via rcccDNA excision and a subsequent immune response.

Conclusions

The HBV1.1X model is the first Cre-regulatable HBV transgenic mouse model and should be of value to mimic chronic HBV infection, with neonatal expression and tolerance of HBV antigens, and on-demand modulation of HBV expression.

Lay summary

Hepatitis B virus (HBV) can only naturally infect humans and chimpanzees. Mouse models have been developed with the HBV genome integrated into mouse chromosomes, but this prevents mice from being cured. We developed a new transgenic mouse model that allows for HBV to be excised from mouse chromosomes to form a recombinant circular DNA molecule resembling the natural circular HBV genome. HBV expression could be reduced in these mice, enabling curative therapies to be tested in this new mouse model.

Metabolic profiling of norepinephrine reuptake inhibitor atomoxetine

Atomoxetine (ATX), a selective and potent inhibitor of the presynaptic norepinephrine transporter, is used mainly to treat attention-deficit hyperactivity disorder. Although multiple adverse effects associated with ATX have been reported including severe liver injuries, the mechanisms of ATX-related toxicity remain largely unknown. Metabolism frequently contributes to adverse effects of a drug through reactive metabolites, and the bioactivation status of ATX is still not investigated yet. Here, we systematically investigated ATX metabolism, bioactivation, species difference in human, mouse, and rat liver microsomes (HLM, MLM, and RLM) and in mice using metabolomic approaches as mice and rats are commonly used animal models for the studies of drug toxicity. We identified thirty one ATX metabolites and adducts in LMs and mice, 16 of which are novel. In LMs, we uncovered two methoxyamine-trapped aldehydes, two cyclization metabolites, detoluene-ATX, and ATX-N-hydroxylation for the first time. Detoluene-ATX and one cyclization metabolite were also observed in mice. Using chemical inhibitors and recombinant CYP enzymes, we demonstrated that CYP2C8 and CYP2B6 mainly contribute to the formation of aldehyde; CYP2D6 is the dominant enzyme for the formation of ATX cyclization and detoluene-ATX; CYP3A4 is major enzyme responsible for the hydroxylamine formation. The findings concerning aldehydes should be very useful to further elucidate the mechanistic aspects of adverse effects associated with ATX from metabolic angles. Additionally, the species differences for each metabolite should be helpful to investigate the contribution of specific metabolites to ATX toxicity and possible drug-drug interactions in suitable models.

Hepatitis B Virus HBx Protein Mediates the Degradation of Host Restriction Factors through the Cullin 4 DDB1 E3 Ubiquitin Ligase Complex

The hepatitis B virus (HBV) regulatory HBx protein is required for infection, and its binding to cellular damaged DNA binding protein 1 (DDB1) is critical for this function. DDB1 is an adaptor protein for the cullin 4A Really Interesting New Gene (RING) E3 ubiquitin ligase (CRL4) complex and functions by binding cellular DDB1 cullin associated factor (DCAF) receptor proteins that recruit substrates for ubiquitination and degradation. We compared the proteins found in the CRL4 complex immunoprecipitated from uninfected versus HBV-infected hepatocytes from human liver chimeric mice for insight into mechanisms by which HBV and the cell interact within the CRL4 complex. Consistent with its role as a viral DCAF, HBx was found in the HBV CRL4 complexes. In tissue culture transfection experiments, we showed that HBx expression led to decreased levels of known restriction factor structural maintenance of chromosomes protein 6 (SMC6) and putative restriction factors stromal interaction molecule 1 (STIM1, zinc finger E-box binding homeobox 2 (ZEB2), and proteasome activator subunit 4 (PSME4). Moreover, silencing of these proteins led to increased HBV replication in the HepG2-sodium taurocholate cotransporting polypeptide (NTCP) infection model. We also identified cellular DCAF receptors in CRL4 complexes from humanized mice. Increasing amounts of HBx did not reveal competitive DCAF binding to cullin4 (CUL4)-DDB1 in plasmid-transfected cells. Our results suggest a model in which HBx benefits virus replication by directly or indirectly degrading multiple cellular restriction factors.

Somatic Liver Knockout (SLiK): A Quick and Efficient Way to Generate Liver-Specific Knockout Mice Using Multiplex CRISPR/Cas9 Gene Editing

Somatic liver knockout (SLiK) is a method developed to rapidly generate a liver-specific knockout of one or several genes. This technique combines the strengths of CRISPR/Cas9 gene editing and hydrodynamic tail-vein injection, a simple in vivo method for transfection of hepatocytes, to harness the powerful selection pressure of tyrosinemic livers to replace host hepatocytes with any desired gene deletion. In this protocol, we will describe sgRNA design and cloning, hydrodynamic tail-vein injection of targeting constructs, and screening and validation methods for efficient in vivo gene editing. © 2020 by John Wiley & Sons, Inc. Support Protocol 1: sgRNA design Support Protocol 2: sgRNA construction: daisy chaining multiple sgRNAs Basic Protocol: Delivery of DNA by hydrodynamic tail-vein injection and liver repopulation of edited hepatocytes Support Protocol 3: Validation of CRISPR/Cas9 cutting in vivo.

Small Animal Models for Human Immunodeficiency Virus (HIV), Hepatitis B, and Tuberculosis: Proceedings of an NIAID Workshop

The main advantage of animal models of infectious diseases over in vitro studies is the gain in the understanding of the complex dynamics between the immune system and the pathogen. While small animal models have practical advantages over large animal models, it is crucial to be aware of their limitations. Although the small animal model at least needs to be susceptible to the pathogen under study to obtain meaningful data, key elements of pathogenesis should also be reflected when compared to humans. Well-designed small animal models for HIV, hepatitis viruses and tuberculosis require, additionally, a thorough understanding of the similarities and differences in the immune responses between humans and small animals and should incorporate that knowledge into the goals of the study. To discuss these considerations, the NIAID hosted a workshop on 'Small Animal Models for HIV, Hepatitis B, and Tuberculosis' on May 30, 2019. Highlights of the workshop are outlined below.

Using CRISPR/Cas9 to model human liver disease

CRISPR/Cas9 gene editing has revolutionised biomedical research. The ease of design has allowed many groups to apply this technology for disease modelling in animals. While the mouse remains the most commonly used organism for embryonic editing, CRISPR is now increasingly performed with high efficiency in other species. The liver is also amenable to somatic genome editing, and some delivery methods already allow for efficient editing in the whole liver. In this review, we describe CRISPR-edited animals developed for modelling a broad range of human liver disorders, such as acquired and inherited hepatic metabolic diseases and liver cancers. CRISPR has greatly expanded the repertoire of animal models available for the study of human liver disease, advancing our understanding of their pathophysiology and providing new opportunities to develop novel therapeutic approaches.

Rapid Disruption of Genes Specifically in Livers of Mice Using Multiplex CRISPR/Cas9 Editing

BACKGROUND & AIMS

Despite advances in gene editing technologies, generation of tissue-specific knockout mice is time-consuming. We used CRISPR/Cas9-mediated genome editing to disrupt genes in livers of adult mice in just a few months, which we refer to as somatic liver knockouts.

METHODS

In this system, Fah^-/- mice are given hydrodynamic tail vein injections of plasmids carrying CRISPR/Cas9 designed to excise exons in Hpd; the Hpd-edited hepatocytes have a survival advantage in these mice. Plasmids that target Hpd and a separate gene of interest can therefore be used to rapidly generate mice with liver-specific deletion of nearly any gene product.

RESULTS

We used this system to create mice with liver-specific knockout of argininosuccinate lyase, which develop hyperammonemia, observed in humans with mutations in this gene. We also created mice with liver-specific knockout of ATP binding cassette subfamily B member 11, which encodes the bile salt export pump. We found that these mice have a biochemical phenotype similar to that of Abcb11^-/- mice. We then used this system to knock out expression of 5 different enzymes involved in drug metabolism within the same mouse.

CONCLUSIONS

This approach might be used to develop new models of liver diseases and study liver functions of genes that are required during development.

P450-Humanized and Human Liver Chimeric Mouse Models for Studying Xenobiotic Metabolism and Toxicity

Preclinical evaluation of drug candidates in experimental animal models is an essential step in drug development. Humanized mouse models have emerged as a promising alternative to traditional animal models. The purpose of this mini-review is to provide a brief survey of currently available mouse models for studying human xenobiotic metabolism. Here, we describe both genetic humanization and human liver chimeric mouse models, focusing on the advantages and limitations while outlining their key features and applications. Although this field of biomedical science is relatively young, these humanized mouse models have the potential to transform preclinical drug testing and eventually lead to a more cost-effective and rapid development of new therapies.

Argininosuccinate Lyase Deficiency Causes an Endothelial-Dependent Form of Hypertension

Primary hypertension is a major risk factor for ischemic heart disease, stroke, and chronic kidney disease. Insights obtained from the study of rare Mendelian forms of hypertension have been invaluable in elucidating the mechanisms causing primary hypertension and development of antihypertensive therapies. Endothelial cells play a key role in the regulation of blood pressure; however, a Mendelian form of hypertension that is primarily due to endothelial dysfunction has not yet been described. Here, we show that the urea cycle disorder, argininosuccinate lyase deficiency (ASLD), can manifest as a Mendelian form of endothelial-dependent hypertension. Using data from a human clinical study, a mouse model with endothelial-specific deletion of argininosuccinate lyase (Asl), and in vitro studies in human aortic endothelial cells and induced pluripotent stem cell-derived endothelial cells from individuals with ASLD, we show that loss of ASL in endothelial cells leads to endothelial-dependent vascular dysfunction with reduced nitric oxide (NO) production, increased oxidative stress, and impaired angiogenesis. Our findings show that ASLD is a unique model for studying NO-dependent endothelial dysfunction in human hypertension.

HBsAg-redirected T cells exhibit antiviral activity in HBV-infected human liver chimeric mice

BACKGROUND

Chronic hepatitis B virus (HBV) infection remains incurable. Although HBsAg-specific chimeric antigen receptor (HBsAg-CAR) T cells have been generated, they have not been tested in animal models with authentic HBV infection.

METHODS

We generated a novel CAR targeting HBsAg and evaluated its ability to recognize HBV+ cell lines and HBsAg particles in vitro. In vivo, we tested whether human HBsAg-CAR T cells would have efficacy against HBV-infected hepatocytes in human liver chimeric mice.

RESULTS

HBsAg-CAR T cells recognized HBV-positive cell lines and HBsAg particles in vitro as judged by cytokine production. However, HBsAg-CAR T cells did not kill HBV-positive cell lines in cytotoxicity assays. Adoptive transfer of HBsAg-CAR T cells into HBV-infected humanized mice resulted in accumulation within the liver and a significant decrease in plasma HBsAg and HBV-DNA levels compared with control mice. Notably, the fraction of HBV core-positive hepatocytes among total human hepatocytes was greatly reduced after HBsAg-CAR T cell treatment, pointing to noncytopathic viral clearance. In agreement, changes in surrogate human plasma albumin levels were not significantly different between treatment and control groups.

CONCLUSIONS

HBsAg-CAR T cells have anti-HBV activity in an authentic preclinical HBV infection model. Our results warrant further preclinical exploration of HBsAg-CAR T cells as immunotherapy for HBV.

In Situ Liver Expression of HBsAg/CD3-Bispecific Antibodies for HBV Immunotherapy

Current therapies against hepatitis B virus (HBV) do not reliably cure chronic infection, necessitating new therapeutic approaches. The T cell response can clear HBV during acute infection, and the adoptive transfer of antiviral T cells during bone marrow transplantation can cure patients of chronic HBV infection. To redirect T cells to HBV-infected hepatocytes, we delivered plasmids encoding bispecific antibodies directed against the viral surface antigen (HBsAg) and CD3, expressed on almost all T cells, directly into the liver using hydrodynamic tail vein injection. We found a significant reduction in HBV-driven reporter gene expression (184-fold) in a mouse model of acute infection, which was 30-fold lower than an antibody only recognizing HBsAg. While bispecific antibodies triggered, in part, antigen-independent T cell activation, antibody production within hepatocytes was non-cytotoxic. We next tested the bispecific antibodies in a different HBV mouse model, which closely mimics the transcriptional template for HBV, covalently closed circular DNA (cccDNA). We found that the antiviral effect was noncytopathic, mediating a 495-fold reduction in HBsAg levels at day 4. At day 33, bispecific antibody-treated mice exhibited 35-fold higher host HBsAg immunoglobulin G (IgG) antibody production versus untreated groups. Thus, gene therapy with HBsAg/CD3-bispecific antibodies represents a promising therapeutic strategy for patients with HBV.

CRISPR/Cas9: at the cutting edge of hepatology

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 genome engineering has revolutionised biomedical science and we are standing on the cusp of medical transformation. The therapeutic potential of this technology is tremendous, however, its translation to the clinic will be challenging. In this article, we review recent progress using this genome editing technology and explore its potential uses in studying and treating diseases of the liver. We discuss the development of new research tools and animal models as well as potential clinical applications, strategies and challenges.

Differentiation of spontaneously contracting cardiomyocytes from non-virally reprogrammed human amniotic fluid stem cells

Congenital heart defects are the most common birth defect. The limiting factor in tissue engineering repair strategies is an autologous source of functional cardiomyocytes. Amniotic fluid contains an ideal cell source for prenatal harvest and use in correction of congenital heart defects. This study aims to investigate the potential of amniotic fluid-derived stem cells (AFSC) to undergo non-viral reprogramming into induced pluripotent stem cells (iPSC) followed by growth-factor-free differentiation into functional cardiomyocytes. AFSC from human second trimester amniotic fluid were transfected by non-viral vesicle fusion with modified mRNA of OCT4, KLF4, SOX2, LIN28, cMYC and nuclear GFP over 18 days, then differentiated using inhibitors of GSK3 followed 48 hours later by inhibition of WNT. AFSC-derived iPSC had high expression of OCT4, NANOG, TRA-1-60, and TRA-1-81 after 18 days of mRNA transfection and formed teratomas containing mesodermal, ectodermal, and endodermal germ layers in immunodeficient mice. By Day 30 of cardiomyocyte differentiation, cells contracted spontaneously, expressed connexin 43 and β-myosin heavy chain organized in sarcomeric banding patterns, expressed cardiac troponin T and β-myosin heavy chain, showed upregulation of NKX2.5, ISL-1 and cardiac troponin T with downregulation of POU5F1, and displayed calcium and voltage transients similar to those in developing cardiomyocytes. These results demonstrate that cells from human amniotic fluid can be differentiated through a pluripotent state into functional cardiomyocytes.

Reprogramming metabolic pathways in vivo with CRISPR/Cas9 genome editing to treat hereditary tyrosinaemia

Many metabolic liver disorders are refractory to drug therapy and require orthotopic liver transplantation. Here we demonstrate a new strategy, which we call metabolic pathway reprogramming, to treat hereditary tyrosinaemia type I in mice; rather than edit the disease-causing gene, we delete a gene in a disease-associated pathway to render the phenotype benign. Using CRISPR/Cas9 in vivo, we convert hepatocytes from tyrosinaemia type I into the benign tyrosinaemia type III by deleting Hpd (hydroxyphenylpyruvate dioxigenase). Edited hepatocytes (Fah(-/-)/Hpd(-/-)) display a growth advantage over non-edited hepatocytes (Fah(-/-)/Hpd(+/+)) and, in some mice, almost completely replace them within 8 weeks. Hpd excision successfully reroutes tyrosine catabolism, leaving treated mice healthy and asymptomatic. Metabolic pathway reprogramming sidesteps potential difficulties associated with editing a critical disease-causing gene and can be explored as an option for treating other diseases.

Novel patient-derived xenograft and cell line models for therapeutic testing of pediatric liver cancer

BACKGROUND & AIMS

Pediatric liver cancer is a rare but serious disease whose incidence is rising, and for which the therapeutic options are limited. Development of more targeted, less toxic therapies is hindered by the lack of an experimental animal model that captures the heterogeneity and metastatic capability of these tumors.

METHODS

Here we established an orthotopic engraftment technique to model a series of patient-derived tumor xenograft (PDTX) from pediatric liver cancers of all major histologic subtypes: hepatoblastoma, hepatocellular cancer and hepatocellular malignant neoplasm. We utilized standard (immuno) staining methods for histological characterization, RNA sequencing for gene expression profiling and genome sequencing for identification of druggable targets. We also adapted stem cell culturing techniques to derive two new pediatric cancer cell lines from the xenografted mice.

RESULTS

The patient-derived tumor xenografts recapitulated the histologic, genetic, and biological characteristics-including the metastatic behavior-of the corresponding primary tumors. Furthermore, the gene expression profiles of the two new liver cancer cell lines closely resemble those of the primary tumors. Targeted therapy of PDTX from an aggressive hepatocellular malignant neoplasm with the MEK1 inhibitor trametinib and pan-class I PI3 kinase inhibitor NVP-BKM120 resulted in significant growth inhibition, thus confirming this PDTX model as a valuable tool to study tumor biology and patient-specific therapeutic responses.

CONCLUSIONS

The novel metastatic xenograft model and the isogenic xenograft-derived cell lines described in this study provide reliable tools for developing mutation- and patient-specific therapies for pediatric liver cancer.

LAY SUMMARY

Pediatric liver cancer is a rare but serious disease and no experimental animal model currently captures the complexity and metastatic capability of these tumors. We have established a novel animal model using human tumor tissue that recapitulates the genetic and biological characteristics of this cancer. We demonstrate that our patient-derived animal model, as well as two new cell lines, are useful tools for experimental therapies.

In vivo reduction of hepatitis B virus antigenemia and viremia by antisense oligonucleotides

BACKGROUND & AIMS

Current treatment of chronic hepatitis B virus infection (CHB) includes interferon and nucleos(t)ide analogues, which generally do not reduce HBV surface antigen (HBsAg) production, a constellation that is associated with poor prognosis of CHB. Here we evaluated the efficacy of an antisense approach using antisense oligonucleotide (ASO) technology already in clinical use for liver targeted therapy to specifically inhibit HBsAg production and viremia in a preclinical setting.

METHODS

A lead ASO was identified and characterized in vitro and subsequently tested for efficacy in vivo and in vitro using HBV transgenic and hydrodynamic transfection mouse and a cell culture HBV infection model, respectively.

RESULTS

ASO treatment decreased serum HBsAg levels ⩾2 logs in a dose and time-dependent manner; HBsAg decreased 2 logs in a week and returned to baseline 4 weeks after a single ASO injection. ASO treatment effectively reduced HBsAg in combination with entecavir, while the nucleoside analogue alone did not. ASO treatment has pan-genotypic antiviral activity in the hydrodynamic transfection system. Finally, cccDNA-driven HBV gene expression is ASO sensitive in HBV infected cells in vitro.

CONCLUSION

Our results demonstrate in a preclinical setting the efficacy of an antisense approach against HBV by efficiently reducing serum HBsAg (as well as viremia) across different genotypes alone or in combination with standard nucleoside therapy. Since the applied antisense technology is already in clinical use, a lead compound can be rapidly validated in a clinical setting and thus, constitutes a novel therapeutic approach targeting chronic HBV infection.

Abstract 050: Loss of Argininosuccinate Lyase Leads to Nitric Oxide Deficiency, Endothelial Dysfunction, Impaired Angiogenesis, and Hypertension

Nitric oxide (NO) is an important mediator of vascular homeostasis and its deficiency in murine models results in hypertension. However, there are few monogenic causes of NO deficiency in humans and the effects of such genetic forms of NO deficiency on vasculature are not well-studied. We have recently shown that argininosuccinate lyase (ASL), a urea cycle enzyme, is necessary for synthesis of NO. ASL deficiency results in decreased production of NO and hypertension in humans and mice. To investigate whether loss of Asl-mediated NO synthesis in the vascular endothelium alone can cause hypertension, we generated a mouse model with endothelial-specific deletion of Asl (VE-Cadherin Cre(tg/+); Asl(flox/flox), or cKO). Asl cKO mice developed hypertension and had higher mean arterial pressure compared to control littermates (102.2± 2.9 vs. 89.8±3.6 mmHg, p<0.05). This hypertension was secondary to endothelial-specific NO deficiency as demonstrated by abnormal relaxation of aortic rings and correction with treatment with an NOS-independent NO supplement (MAP in sodium nitrite treated Asl cKO 97.7±3.8 vs. 97.6±7.3 mmHg in untreated control mice). To evaluate the human relevance of these findings, we developed human cell-based models from patients with ASL deficiency. Human induced pluripotent stem cells (hiPSCs) were generated and differentiated into endothelial cells. Interestingly, ASL-deficient hiPSCs differentiated less efficiently into endothelial cells as compared to control hiPSCs (9.7±4.0 vs. 20.8±3.7 % of CD144+; CD31+ cells, p<0.01). Furthermore, ASL-deficient hiPSCs-derived endothelial cells had a significantly reduced capacity to form capillary-like structures on Matrigel. Our study using a novel mouse model and hiPSCs-derived endothelial cells from patients with a rare Mendelian form of hypertension supports the hypothesis that structural and functional abnormalities in endothelial cells contribute to pathogenesis of hypertension. Our study is the first to use hiPSC-derived endothelial cells as a model system to study hypertension and highlights the utility of this technology in exploring the pathogenesis of other vascular diseases.

The camKK2/camKIV relay is an essential regulator of hepatic cancer

Hepatic cancer is one of the most lethal cancers worldwide. Here, we report that the expression of Ca(2+) /calmodulin-dependent protein kinase kinase 2 (CaMKK2) is significantly up-regulated in hepatocellular carcinoma (HCC) and negatively correlated with HCC patient survival. The CaMKK2 protein is highly expressed in all eight hepatic cancer cell lines evaluated and is markedly up-regulated relative to normal primary hepatocytes. Loss of CaMKK2 function is sufficient to inhibit liver cancer cell growth, and the growth defect resulting from loss of CaMKK2 can be rescued by ectopic expression of wild-type CaMKK2 but not by kinase-inactive mutants. Cellular ablation of CaMKK2 using RNA interference yields a gene signature that correlates with improvement in HCC patient survival, and ablation or pharmacological inhibition of CaMKK2 with STO-609 impairs tumorigenicity of liver cancer cells in vivo. Moreover, CaMKK2 expression is up-regulated in a time-dependent manner in a carcinogen-induced HCC mouse model, and STO-609 treatment regresses hepatic tumor burden in this model. Mechanistically, CaMKK2 signals through Ca(2+) /calmodulin-dependent protein kinase 4 (CaMKIV) to control liver cancer cell growth. Further analysis revealed that CaMKK2 serves as a scaffold to assemble CaMKIV with key components of the mammalian target of rapamycin/ribosomal protein S6 kinase, 70 kDa, pathway and thereby stimulate protein synthesis through protein phosphorylation.

CONCLUSION

The CaMKK2/CaMKIV relay is an upstream regulator of the oncogenic mammalian target of rapamycin/ribosomal protein S6 kinase, 70 kDa, pathway, and the importance of this CaMKK2/CaMKIV axis in HCC growth is confirmed by the potent growth inhibitory effects of genetically or pharmacologically decreasing CaMKK2 activity; collectively, these findings suggest that CaMKK2 and CaMKIV may represent potential targets for hepatic cancer.

Development and rescue of human familial hypercholesterolaemia in a xenograft mouse model

Diseases of lipid metabolism are a major cause of human morbidity, but no animal model entirely recapitulates human lipoprotein metabolism. Here we develop a xenograft mouse model using hepatocytes from a patient with familial hypercholesterolaemia caused by loss-of-function mutations in the low-density lipoprotein receptor (LDLR). Like familial hypercholesterolaemia patients, our familial hypercholesterolaemia liver chimeric mice develop hypercholesterolaemia and a 'humanized‘ serum profile, including expression of the emerging drug targets cholesteryl ester transfer protein and apolipoprotein (a), for which no genes exist in mice. We go on to replace the missing LDLR in familial hypercholesterolaemia liver chimeric mice using an adeno-associated virus 9-based gene therapy and restore normal lipoprotein profiles after administration of a single dose. Our study marks the first time a human metabolic disease is induced in an experimental animal model by human hepatocyte transplantation and treated by gene therapy. Such xenograft platforms offer the ability to validate human experimental therapies and may foster their rapid translation into the clinic.

Familial hypercholesterolemia (FH) is a congenital disease associated with high plasma cholesterol levels. Here, the authors recapitulate FH in chimeric mice, in which livers are repopulated with hepatocytes from an FH patient, and successfully correct the disease using adenovirus-mediated gene therapy.

KDR identifies a conserved human and murine hepatic progenitor and instructs early liver development

Understanding the fetal hepatic niche is essential for optimizing the generation of functional hepatocyte-like cells (hepatic cells) from human embryonic stem cells (hESCs). Here, we show that KDR (VEGFR2/FLK-1), previously assumed to be mostly restricted to mesodermal lineages, marks a hESC-derived hepatic progenitor. hESC-derived endoderm cells do not express KDR but, when cultured in media supporting hepatic differentiation, generate KDR+ hepatic progenitors and KDR- hepatic cells. KDR+ progenitors require active KDR signaling both to instruct their own differentiation into hepatic cells and to non-cell-autonomously support the functional maturation of cocultured KDR- hepatic cells. Analysis of human fetal livers suggests that similar progenitors are present in human livers. Lineage tracing in mice provides in vivo evidence of a KDR+ hepatic progenitor for fetal hepatoblasts, adult hepatocytes, and adult cholangiocytes. Altogether, our findings reveal that KDR is a conserved marker for endoderm-derived hepatic progenitors and a functional receptor instructing early liver development.

A high proliferation rate is required for cell reprogramming and maintenance of human embryonic stem cell identity

Human embryonic stem (hES) cells show an atypical cell-cycle regulation characterized by a high proliferation rate and a short G1 phase. In fact, a shortened G1 phase might protect ES cells from external signals inducing differentiation, as shown for certain stem cells. It has been suggested that self-renewal and pluripotency are intimately linked to cell-cycle regulation in ES cells, although little is known about the overall importance of the cell-cycle machinery in maintaining ES cell identity. An appealing model to address whether the acquisition of stem cell properties is linked to cell-cycle regulation emerged with the ability to generate induced pluripotent stem (iPS) cells by expression of defined transcription factors. Here, we show that the characteristic cell-cycle signature of hES cells is acquired as an early event in cell reprogramming. We demonstrate that induction of cell proliferation increases reprogramming efficiency, whereas cell-cycle arrest inhibits successful reprogramming. Furthermore, we show that cell-cycle arrest is sufficient to drive hES cells toward irreversible differentiation. Our results establish a link that intertwines the mechanisms of cell-cycle control with the mechanisms underlying the acquisition and maintenance of ES cell identity.

Human liver chimeric mice provide a model for hepatitis B and C virus infection and treatment

A paucity of versatile small animal models of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection has been an impediment to both furthering understanding of virus biology and testing antiviral therapies. We recently described a regulatable system for repopulating the liver of immunodeficient mice (specifically mice lacking fumaryl acetoacetate hydrolase [Fah], recombination activating gene 2 [Rag2], and the gamma-chain of the receptor for IL-2 [Il-2rgamma]) with human hepatocytes. Here we have shown that a high transplantation dose (3 x 106 to 5 x 106 human hepatocytes/mouse) generates a higher rate of liver chimerism than was previously obtained in these mice, up to 95% human hepatocyte chimerism. Mice with a high level of human liver chimerism propagated both HBV and HCV, and the HCV-infected mice were responsive to antiviral treatment. This human liver chimeric mouse model will expand the experimental possibilities for studying HBV and HCV infection, and possibly other human hepatotropic pathogens, and prove useful for antiviral drug testing.

Whole animal copper flux assessed by positron emission tomography in the Long – Evans cinnamon rat – a feasibility study

Copper is an essential trace element. However, excess copper can lead to oxidation of biomolecules and cell damage and copper levels must be carefully controlled. While copper homeostasis has been studied extensively at the cellular level, short-term body copper fluxes are poorly understood. Here, we assessed for the first time the feasibility of measuring whole body copper flux by positron emission tomography, using 64Cu. A comparative approach comparing the Long-Evans cinnamon (LEC) rat to the wild type was chosen. LEC rats are an accepted model for Wilson disease, an inherited disorder of copper excretion in humans. In LEC rats as well as in Wilson patients, the copper transporting ATPase, ATP7B, is defective. This ATPase is primarily expressed in the liver and serves in copper secretion via the bile. Dysfunction of ATP7B leads to accumulation of copper in the liver. A control and an LEC rat were transgastrically injected with 10 microg of 64Cu and the copper flux followed for three hours by whole animal PET and concomitant collection of bile, as well as the analysis of tissue following tomography. As seen by PET, the administered copper was largely trapped in the stomach and the proximal intestine, and without a significant difference between control and LEC rat. Due to an insufficient dynamic range of the PET technology, copper which was systemically absorbed and primarily transported to the liver could only be followed by sampling and by beta-counting. Biliary copper excretion ensued after 15 min in the control rat, but was absent in the LEC rat. Biliary excretion reached saturation one hour after copper administration. The trapping of orally administered copper in the gastrointestinal tract may be an important mechanism to prevent copper toxicity under conditions of a sudden, excessive copper load, which cannot be alleviated by increased biliary secretion. This trapping does however limit the utility of PET to measure whole animal copper flux.

Herpes simplex virus hepatitis 4 years after liver transplantation

If not promptly recognized and treated, herpes simplex virus (HSV) hepatitis is associated with a high mortality. A patient transplanted for primary sclerosing cholangitis required, 4 years later, a colectomy for a steroid-resistant flare of ulcerative colitis. He subsequently developed fever, with genital and oral ulcerations. He was hospitalized for diabetic decompensation with massive elevation of serum aminotransferases. Examination revealed vesicles on the hands. Liver biopsy showed Cowdry type B inclusions. Therapy with acyclovir was immediately initiated and the patient recovered. This case illustrates the diagnostic importance of mucocutaneous lesions in the assessment of complications after liver transplantation.

Tetrathiomolybdate inhibition of the Enterococcus hirae CopB copper ATPase

Tetrathiomolybdate (TTM) avidly interacts with copper and has recently been employed to reduce excess copper in patients with Wilson disease. We found that TTM inhibits the purified Enterococcus hirae CopB copper ATPase with an IC(50) of 34 nM. Dithiomolybdate and trithiomolybdate, which commonly contaminate TTM, inhibited the copper ATPases with similar potency. Inhibition could be reversed by copper or silver, suggesting inhibition by substrate binding. These findings for the first time allowed an estimate of the high affinity of CopB for copper and silver. TTM is a new tool for the study of copper ATPases.

Interaction of the CopZ copper chaperone with the CopA copper ATPase of Enterococcus hirae assessed by surface plasmon resonance

Intracellular copper routing in Enterococcus hirae can be accomplished by the CopZ metallochaperone. Using surface plasmon resonance analysis, we show here that CopZ interacts with the CopA copper ATPase. The binding affinity of CopZ for CopA was increased in the presence of copper, due to a 15-fold lower dissociation rate constant. Mutating the N-terminal copper binding motif of CopA from CxxC to SxxS abolished this copper-induced effect. Moreover, CopZ failed to show an interaction with an unrelated copper binding protein used as a control. These results show that (i) the CopA copper ATPase specifically interacts with the CopZ chaperone, (ii) this interaction is based on protein-protein interaction, and (iii) surface plasmon resonance is a novel tool for quantitative analysis of metallochaperone-target interactions.

Structure-function analysis of purified Enterococcus hirae CopB copper ATPase: effect of Menkes/Wilson disease mutation homologues

The Enterococcus hirae CopB ATPase (EC 3.6.1.3) confers copper resistance to the organism by expelling excess copper. Two related human ATPase genes, ATP7A (EC 3.6.1.36) and ATP7B (EC 3.6.1.36), have been cloned as the loci of mutations causing Menkes and Wilson diseases, diseases of copper metabolism. Many mutations in these genes have been identified in patients. Since it has not yet been possible to purify the human copper ATPases, it has proved difficult to test the impact of mutations on ATPase function. Some mutations occur in highly conserved sequence motifs, suggesting that their effect on function can be tested with a homologous enzyme. Here, we used the E. hirae CopB ATPase to investigate the impact of such mutations on enzyme function in vivo and in vitro. The Menkes disease mutation of Cys-1000-->Arg, changing the conserved Cys-Pro-Cys ('CPC') motif, was mimicked in CopB. The corresponding Cys-396-->Ser CopB ATPase was unable to restore copper resistance in a CopB knock-out mutant in vivo. The purified mutant ATPase still formed an acylphosphate intermediate, but possessed no detectable ATP hydrolytic activity. The most frequent Wilson disease mutation, His-1069-->Gln, was introduced into CopB as His-480-->Gln (H480Q). This mutant CopB also failed to confer copper resistance to a CopB knock-out strain. Purified H480Q CopB formed an acylphosphate intermediate and retained a small, but significant, ATPase activity. Our results reveal that Cys-396 and His-480 of CopB are key residues for ATPase function, and similar roles are suggested for Cys-1000 and His-1069 of Menkes and Wilson ATPases respectively.

Expression of the human Menkes ATPase in Xenopus laevis oocytes

Menkes disease is an X-linked disorder of copper metabolism that is usually fatal. The affected gene has recently been cloned and encodes one of the two human copper ATPases. If the Menkes ATPase is defective, copper is trapped in the intestinal mucosa, leading to systemic copper deficiency. In order to study copper transport by this ATPase and the effects of disease mutations on its function, we developed a Xenopus laevis oocyte expression system. Wild-type Menkes ATPase cDNA and a fusion of this gene with the green fluorescent protein (GFP) gene was transcribed in vitro and the mRNA injected into oocytes. Expression in oocytes was analyzed by Western blotting and fluorescence microscopy. The Menkes ATPase-GFP chimera appeared to localize primarily to the plasma membrane as assessed by confocal microscopy. This system should thus provide an interesting new tool to study the function of the Menkes ATPase.

Epidermal growth factor is decreased in liver of rats with biliary cirrhosis but does not act as paracrine growth factor immediately after hepatectomy

BACKGROUND/AIMS

Epidermal growth factor, a potent mitogen for hepatocytes and cholangiocytes, is thought to act as an immediate-early gene after partial hepatectomy. Since regeneration is impaired in cirrhosis, we explored the expression of epidermal growth factor in cirrhotic rat liver immediately after partial hepatectomy.

METHODS

Cirrhosis was induced by bile duct ligation (n=21); sham-operated animals served as controls (n=21). Twenty-five days after initial surgery animals were subjected to 70% partial hepatectomy or sham operation; the liver was sampled before surgery and 20, 40 and 90 min thereafter. Epidermal growth factor mRNA levels were assessed by quantitative reverse transcription polymerase chain reaction. Protein expression was estimated by immunohistochemistry using a polyclonal antibody against epidermal growth factor.

RESULTS

Before hepatectomy, epidermal growth factor mRNA averaged 70.3+/-39.9 pg/microg of total RNA in controls; this was markedly decreased to 21.9+/-12.7 pg/microg RNA in bile duct ligation (p<0.01). Epidermal growth factor mRNA did not increase after partial hepatectomy in either group, with the exception of sham-operated controls. Immunohistochemistry revealed that partial hepatectomy had no effect on epidermal growth factor expression. Hepatocytes showed uniformly cytosolic epidermal growth factor in controls, while in bile duct ligation immunostaining was faint or absent. Cholangiocytes exhibited a strong cytosolic staining in all experimental groups.

CONCLUSIONS

The present study shows that epidermal growth factor is reduced in the cirrhotic liver. This could contribute to the loss of parenchymal liver tissue observed in cirrhosis. The lack of up-regulation after PH sheds doubt on the role of epidermal growth factor as an immediate-early gene in hepatic regeneration. Further, we demonstrate that epidermal growth factor accumulates in cholangiocytes. This observation is strong evidence for involvement of the mitogen epidermal growth factor in the proliferation of bile ducts during cirrhogenesis.

[How (deficient) copper causes illness]

Copper is an essential cofactor in all cells. However, it remains largely unknown how cells deal with this element, which is essential yet toxic. Through the study of microbial model systems on the one hand, and the investigation of inherited diseases in copper metabolism on the other, important insights into the way cells deal with copper can be gained. Two key new elements of copper metabolism have emerged from these studies: ATP-driven copper pumps and intracellular copper transport proteins, the copper chaperones.