Comprehensive gene profiling of the metabolic landscape of humanized livers in mice.

BACKGROUND & AIMS: The human liver transcriptome is complex and highly dynamic, e.g. one gene may produce multiple distinct transcripts, each with distinct posttranscriptional modifications. Direct knowledge of transcriptome dynamics, however, is largely obscured by the inaccessibility of the human liver to treatments and the insufficient annotation of the human liver transcriptome at transcript and RNA modification levels. METHODS: We generated mice that carry humanized livers of identical genetic background and subjected them to representative metabolic treatments. We then analyzed the humanized livers with nanopore single-molecule direct RNA sequencing to determine the expression level, m6A modification and poly(A) tail length of all RNA transcript isoforms. Our system allows for the de novo annotation of human liver transcriptomes to reflect metabolic responses and for the study of transcriptome dynamics in parallel. RESULTS: Our analysis uncovered a vast number of novel genes and transcripts. Our transcript-level analysis of human liver transcriptomes also identified a multitude of regulated metabolic pathways that were otherwise invisible using conventional short-read RNA sequencing. We revealed for the first time the dynamic changes in m6A and poly(A) tail length of human liver transcripts, many of which are transcribed from key metabolic genes. Furthermore, we performed comparative analyses of gene regulation between humans and mice, and between two individuals using the liver-specific humanized mice, revealing that transcriptome dynamics are highly species- and genetic background-dependent. CONCLUSION: Our work revealed a complex metabolic response landscape of the human liver transcriptome and provides a novel resource to understand transcriptome dynamics of the human liver in response to physiologically relevant metabolic stimuli (https://caolab.shinyapps.io/human_hepatocyte_landscape/). IMPACT AND IMPLICATIONS: Direct knowledge of the human liver transcriptome is currently very limited, hindering the overall understanding of human liver pathophysiology. We combined a liver-specific humanized mouse model and long-read direct RNA sequencing technology to establish a de novo annotation of the human liver transcriptome and identified a multitude of regulated metabolic pathways that were otherwise invisible using conventional technologies. The extensive regulatory information on human genes we provided could enable basic scientists to infer the pathological relevance of their genes of interest and physician scientists to better pinpoint the changes in metabolic networks underlying a specific pathophysiology.

TNF receptor-related factor 3 inactivation promotes the development of intrahepatic cholangiocarcinoma through NF-κB-inducing kinase-mediated hepatocyte transdifferentiation.

BACKGROUND AND AIMS: Intrahepatic cholangiocarcinoma (ICC) is a deadly but poorly understood disease, and its treatment options are very limited. The aim of this study was to identify the molecular drivers of ICC and search for therapeutic targets. APPROACH AND RESULTS: We performed a Sleeping Beauty transposon-based in vivo insertional mutagenesis screen in liver-specific Pten -deficient mice and identified TNF receptor-related factor 3 ( Traf3 ) as the most significantly mutated gene in murine ICCs in a loss-of-function manner. Liver-specific Traf3 deletion caused marked cholangiocyte overgrowth and spontaneous development of ICC in Pten knockout and KrasG12D mutant mice. Hepatocyte-specific, but not cholangiocyte-specific, Traf3 -deficient and Pten -deficient mice recapitulated these phenotypes. Lineage tracing and single-cell RNA sequencing suggested that these ICCs were derived from hepatocytes through transdifferentiation. TRAF3 and PTEN inhibition induced a transdifferentiation-like phenotype of hepatocyte-lineage cells into proliferative cholangiocytes through NF-κB-inducing kinase (NIK) up-regulation in vitro. Intrahepatic NIK levels were elevated in liver-specific Traf3 -deficient and Pten -deficient mice, and NIK inhibition alleviated cholangiocyte overgrowth. In human ICCs, we identified an inverse correlation between TRAF3 and NIK expression, with low TRAF3 or high NIK expression associated with poor prognosis. Finally, we showed that NIK inhibition by a small molecule inhibitor or gene silencing suppressed the growth of multiple human ICC cells in vitro and ICC xenografts in vivo. CONCLUSIONS: TRAF3 inactivation promotes ICC development through NIK-mediated hepatocyte transdifferentiation. The oncogenic TRAF3-NIK axis may be a potential therapeutic target for ICC.

In Vivo and In Vitro Induction of Cytochrome P450 3A4 by Thalidomide in Humanized-Liver Mice and Experimental Human Hepatocyte HepaSH cells.

Autoinduction of cytochrome P450 (P450) 3A4-mediated metabolism of thalidomide was investigated in humanized-liver mice and human hepatocyte-derived HepaSH cells. The mean plasma ratios of 5-hydroxythalidomide and glutathione adducts to thalidomide were significantly induced (3.5- and 6.0-fold, respectively) by thalidomide treatment daily at 1000 mg/kg for 3 days and measured at 2 h after the fourth administration (on day 4). 5-Hydroxythalidomide was metabolically activated by P450 3A4 in HepaSH cells pretreated with 300 and 1000 µM thalidomide, and 5,6-dihydroxythalidomide was detected. Significant induction of P450 3A4 mRNA expression (4.1-fold) in the livers of thalidomide-treated mice occurred. Thalidomide exerts a variety of actions through multiple mechanisms following bioactivation by induced human P450 3A enzymes.

HepaSH cells: Experimental human hepatocytes with lesser inter-individual variation and more sustainable availability than primary human hepatocytes.

Primary human hepatocytes (PHHs) have been commonly used as the gold standard in many drug metabolism studies, regardless of having large inter-individual variation. These inter-individual variations in PHHs arise primarily from genetic polymorphisms, as well as from donor health conditions and storage conditions prior to cell processing. To equalize the effects of the latter two factors, PHHs were transplanted to quality-controlled mice providing human hepatocyte proliferation niches, and engrafted livers were generated. Cells that were harvested from engrafted livers, call this as experimental human hepatocytes (EHH; termed HepaSH cells), were stably and reproducibly produced from 1014 chimeric mice produced by using 17 different PHHs. Expression levels of acute phase reactant (APR) genes as indicators of a systemic reaction to the environmental/inflammatory insults of liver donors varied widely among PHHs. In contrast to PHHs, the expression of APR genes in HepaSH cells was found to converge within a narrower range than in donor PHHs. Further, large individual differences in the expression levels of drug metabolism-related genes (28 genes) observed in PHHs were greatly reduced among HepaSH cells produced in a unified in vivo environment, and none deviated from the range of gene expression levels in the PHHs. The HepaSH cells displayed a similar level of drug-metabolizing enzyme activity and gene expression as the average PHHs but retained their characteristics for drug-metabolizing enzyme gene polymorphisms. Furthermore, long-term 2D culture was possible and HBV infection was confirmed. These results suggest that the stably and reproducibly providable HepaSH cells with lesser inter-individual differences in drug-metabolizing properties, may have a potential to substitution for PHH as practical standardized human hepatocytes in drug discovery research.

The Unique Human N10-Glucuronidated Metabolite Formation from Olanzapine in Chimeric NOG-TKm30 Mice with Humanized Livers.

Olanzapine is an antipsychotic agent with species-dependent pharmacokinetic profiles in both humans and animals. In the present study, the metabolic profiles of olanzapine in vitro and in vivo were compared in non-transplanted immunodeficient NOG-TKm30 mice and chimeric mice with humanized livers (hereafter humanized-liver mice). Hepatic microsomal fractions prepared from humanized-liver mice and humans mediated olanzapine N10-glucuronidation, whereas fractions from cynomolgus monkeys, marmosets, minipigs, dogs, rabbits, guinea pigs, rats, CD1 mice, and NOG-TKm30 mice did not. The olanzapine N10-glucuronidation activity in liver microsomes from humanized-liver mice was inhibited by hecogenin, a human UDP-glucuronosyltransferase (UGT) 1A4 inhibitor. In addition, hepatocytes from humanized-liver mice suggest that olanzapine N10-glucuronidation was a major metabolic pathway in the livers of humanized-liver mice. After a single oral dose of olanzapine (10 mg/kg body weight) to humanized-liver mice and control NOG-TKm30 mice, olanzapine N10-glucuronide isomers and olanzapine N4'-glucuronide were detected only in the plasma of humanized-liver mice. In contrast, the area under the curve for N4'-demethylolanzapine, 2-hydroxymethylolanzapine, and 7-hydroxyolanzapine glucuronide was higher in NOG-TKm30 mice than that in humanized-liver mice. The cumulative excreted amounts of olanzapine N10-glucuronide isomers were high in the urine and feces from humanized-liver mice, whereas the cumulative excreted amounts of 2-hydroxymethylolanzapine were higher in NOG-TKm30 mice than in humanized-liver mice. Thus, production of human-specific olanzapine N10-glucuronide was observed in humanized-liver mice, which was consistent with the in vitro glucuronidation data. These results suggest that humanized-liver mice are useful for studying drug oxidation and conjugation of olanzapine in humans. SIGNIFICANCE STATEMENT: Human-specific olanzapine N10-glucuronide isomers were generated in chimeric NOG-TKm30 mice with humanized livers (humanized-liver mice), and high UGT1A4-dependent N10-glucuronidation was observed in the liver microsomes from humanized-liver mice. Hence, humanized-liver mice may be a suitable model for studying UGT1A4-dependent biotransformation of drugs in humans.

Pharmacokinetic Models Scaled-up from Humanized-liver Mouse Data Can Account for Drug Monitoring Results of Atomoxetine and Its 4-Hydroxylated and N-Demethylated Metabolites i n Pediatric Patients Genotyped for Cytochrome P450 2D6.

Atomoxetine is a cytochrome P450 (P450) 2D6 probe substrate and an approved medicine for attention-deficit/hyperactivity disorder. In this humanized-liver mouse study, interactions between atomoxetine and the P450 2D6 probe drug paroxetine were observed. Human physiologically based pharmacokinetic (PBPK) models were established by scaling up humanized-liver mouse data obtained in the absence or presence of paroxetine. These models could explain the drug monitoring results of atomoxetine and its primary 4-hydroxylated and N-demethylated metabolites in Japanese children aged 8-14 years and could be used to help establish the correct dosage and for the evaluation of clinical outcomes. The results of simple PBPK models (using input parameters that reflected the subjects' small body size and normal or reduced P450 2D6-dependent clearance) were in general agreement with one-point measured plasma concentrations of atomoxetine and its 4-hydroxylated and N-demethylated metabolites in 13 pediatric participants. Unexpectedly high hepatic exposure, possibly in intermediate-metabolizer patients harboring CYP2D6*10 or 2D6*36 alleles, might in part explain the adverse effects of atomoxetine prescribed alone recorded in a Japanese adverse-event database. The steady-state, one-point drug monitoring data from the participants indicated extensive biotransformation of atomoxetine to 4-hydroxyatomoxetine under individually prescribed doses of atomoxetine. These results also suggest that a relatively narrow range of 4-hydroxyatomoxetine and N-desmethylatomoxetine concentration ratios in spot urine and/or plasma samples from pediatric patients could be a simple semiquantitative determinant factor for P450 2D6 intermediate metabolizers, compared with the wide range of concentrations of the two primary metabolites and substrate in extensive metabolizers. Significance Statement Validated simple pharmacokinetic models are able to predict steady-state plasma concentrations of the approved medicine atomoxetine and its primary metabolites in the majority of pediatric patients. The package insert advises careful dose escalation, especially for poor metabolizers; however, no simple way exists to determine P450 2D6 phenotypes. A relatively narrow range ratio of 4-hydroxyatomoxetine and N-desmethylatomoxetine in spot urine/plasma samples could be a simple semi-quantitative determinant factor for P450 2D6 intermediate metabolizers to optimize or confirm the correct dosage.

Empirical scaling factor for predicting human pharmacokinetic profiles of disproportionate metabolites using the Css-MRTpo method and chimeric mice with humanised livers.

Predicting plasma concentration-time profiles of disproportionate metabolites in humans is crucial for evaluating metabolites according to the Safety Testing guidelines. We evaluated Css-MRTpo, an empirical method, using chimeric mice with humanised livers capable of generating human-disproportionate metabolites. Azilsartan and AZ-M2 were administered to humanised chimeric mice, and pharmacokinetic parameters were obtained. Pharmacokinetic data for DS-1971a and DS-M1 in humanised chimeric mice were obtained from the literature. The human plasma concentration-time profiles of these compounds were simulated using the Css-MRTpo method. Azilsartan, DS-1971a, and PF-04937319 produced human disproportionate metabolites, AZ-M2, DS-M1, and PF-M1, respectively. The predicted human pharmacokinetic profiles of PF-04937319 and PF-M1 were obtained from a previous study, and their outcomes were re-evaluated. Our findings revealed that the plasma concentrations of the three metabolites were unexpectedly underpredicted, whereas the three unchanged drugs were reasonably predicted. Further, the introduction of the empirical scaling factor of 3, obtained from six model compounds, improved the predictability of metabolites, suggesting the potential usefulness of the Css-MRTpo method in combination with humanised chimeric mice for predicting the pharmacokinetic profiles of disproportionate metabolites at the early stage of new drug development.

Cytochrome P450 1A2 and 2C enzymes autoinduced by omeprazole in dog hepatocytes and human HepaRG and HepaSH cells are involved in omeprazole 5-hydroxylation and sulfoxidation.

The induction assay for the cytochromes P450 (P450s) is an important tool in drug discovery and development. The inductions of dog P450 1A2 and 3A12 by omeprazole and rifampicin were functionally characterised in dog hepatocytes and were compared with induction in human HepaRG and HepaSH cells.P450 1A2-dependent ethoxyresorufin O-deethylation was induced by R,S-omeprazole and P450 3 A-dependent midazolam 1'-hydroxylation was induced by rifampicin, and both reactions were significantly enhanced in cultured dog hepatocytes and human HepaRG and HepaSH cells.Recombinant dog P450 1A2 exhibited activities towards R- and S-omeprazole 5-hydroxylation with low Km values of 23-28 µM, whereas dog P450 2C21 and 3A12 efficiently mediated S-omeprazole 5-hydroxylation and sulfoxidation, respectively, with high Vmax values of 12-17 min-1.Although omeprazole 5-hydroxylation by human P450 2C19 (and sulfoxidation by P450 3A4) in human HepaSH cells were slightly (∼2-fold) induced by R,S-omeprazole, dog P450 1A2 was autoinduced by omeprazole in dog hepatocytes and showed enhanced R-omeprazole 5-hydroxylation activity (∼5-fold).These results indicate that omeprazole can be an autoinducer of P450 1A2 in hepatocytes, and this enzyme was found to be involved in omeprazole 5-hydroxylation and sulfoxidation in dog hepatocytes and human HepaRG and HepaSH cells.

Expansion, in vivo-ex vivo cycling, and genetic manipulation of primary human hepatocytes.

Primary human hepatocytes (PHHs) are an essential tool for modeling drug metabolism and liver disease. However, variable plating efficiencies, short lifespan in culture, and resistance to genetic manipulation have limited their use. Here, we show that the pyrrolizidine alkaloid retrorsine improves PHH repopulation of chimeric mice on average 10-fold and rescues the ability of even poorly plateable donor hepatocytes to provide cells for subsequent ex vivo cultures. These mouse-passaged (mp) PHH cultures overcome the marked donor-to-donor variability of cryopreserved PHH and remain functional for months as demonstrated by metabolic assays and infection with hepatitis B virus and Plasmodium falciparum mpPHH can be efficiently genetically modified in culture, mobilized, and then recultured as spheroids or retransplanted to create highly humanized mice that carry a genetically altered hepatocyte graft. Together, these advances provide flexible tools for the study of human liver disease and evaluation of hepatocyte-targeted gene therapy approaches.

Hepatic Stellate Cells in Hepatocellular Carcinoma Promote Tumor Growth Via Growth Differentiation Factor 15 Production.

BACKGROUND & AIMS: Although the tumor microenvironment plays an important role in tumor growth, it is not fully understood what role hepatic stellate cells (HSCs) play in the hepatocellular carcinoma (HCC) microenvironment. METHODS: A high-fat diet after streptozotocin was administered to HSC-specific Atg7-deficient (GFAP-Atg7 knockout [KO]) or growth differentiation factor 15 (GDF15)-deficient (GFAP-GDF15KO) mice. LX-2 cells, a human HSC cell line, were cultured with human hepatoma cells. RESULTS: In the steatohepatitis-based tumorigenesis model, GFAP-Atg7KO mice formed fewer and smaller liver tumors than their wild-type littermates. Mixed culture of LX-2 cells and hepatoma cells promoted LX-2 cell autophagy and hepatoma cell proliferation, which were attenuated by Atg7 KO in LX-2 cells. Hepatoma cell xenograft tumors grew rapidly in the presence of LX-2 cells, but Atg7 KO in LX-2 cells abolished this growth. RNA-sequencing revealed that LX-2 cells cultured with HepG2 cells highly expressed GDF15, which was abolished by Atg7 KO in LX-2 cells. GDF15 KO LX-2 cells did not show a growth-promoting effect on hepatoma cells either in vitro or in the xenograft model. GDF15 deficiency in HSCs reduced liver tumor size caused by the steatohepatitis-based tumorigenesis model. GDF15 was highly expressed and GDF15-positive nonparenchymal cells were more abundant in human HCC compared with noncancerous parts. Single-cell RNA sequencing showed that GDF15-positive rates in HSCs were higher in HCC than in background liver. Serum GDF15 levels were high in HCC patients and increased with tumor progression. CONCLUSIONS: In the HCC microenvironment, an increase of HSCs that produces GDF15 in an autophagy-dependent manner may be involved in tumor progression.

Bovine ß-lactoglobulin-induced passive systemic anaphylaxis model using humanized NOG hIL-3/hGM-CSF transgenic mice.

Food allergy is a common disease caused by intake of allergen-containing foods, such as milk, eggs, peanuts and wheat. Systemic anaphylaxis is a severe hypersensitive allergic reaction resulting from degranulation of mast cells or basophils after cross-linking of surface high-affinity IgE receptors (Fcε-RI) with allergen-specific IgE and allergens. In this study, we developed a novel human mast cell/basophil-engrafted mouse model that recapitulates systemic anaphylaxis triggered by ß-lactoglobulin (BLG), a major allergen found in cow's milk. Human CD34+ hematopoietic stem cells were transferred into NOG (non-Tg) or NOG hIL-3/hGM-CSF transgenic (Tg) mice. After 14-16 weeks, bovine BLG-specific human IgE was intravenously injected into humanized mice, followed by intravenous or oral bovine BLG exposure 1 day later. Body temperature in Tg, but not in non-Tg, mice gradually decreased within 10 min, and 80% of Tg mice died within 1 h by intravenous BLG exposure. Serum histamine levels and anaphylaxis scores in Tg mice were markedly increased compared to non-Tg mice. Furthermore, these allergic symptoms were significantly inhibited by epinephrine treatment of the Tg mice. Therefore, the current NOG hIL-3/hGM-CSF Tg mouse model may be useful for development of novel anaphylaxis drugs for treatment of food allergies and for safety assessment of low-allergenicity extensively hydrolyzed cow's milk whey protein-based infant formulas.

Comparison of mouse and human cytochrome P450 mediated-drug metabolising activities in hepatic and extrahepatic microsomes.

Despite the importance of mice as a preclinical species in drug testing, their hepatic and extrahepatic drug-metabolising characteristics are poorly understood. Here, we compared the P450-dependent drug oxidation activity in tissue microsomes and distribution patterns of P450 protein/mRNA between humans and mice.The activities of midazolam 1'-/4-hydroxylation in the liver and intestine and chlorzoxazone 6-hydroxylation in the liver were similar in humans and mice. The activities of coumarin 7-hydroxylation, flurbiprofen 4'-hydroxylation, and S-mephenytoin 4'-hydroxylation in the liver were higher in humans than in mice. The activities of 7-ethoxyresorufin O-deethylation in the liver, 7-pentoxyresorufin O-depentylation in the lung/liver/intestine, bufuralol 1'-hydroxylation in the liver/intestine, propafenone 4'-hydroxylation in liver/intestine, and diazepam N-demethylation in the liver/intestine were higher in mice than in humans.CYP1A2/2E1 mRNAs were mainly expressed in the livers of humans and mice. Cyp2b9/2b10 mRNAs were abundant in the mouse lung/liver/intestine, but CYP2B6 was mainly expressed in the human liver. CYP2C/2D/3A mRNAs were expressed in the liver and intestine, with the respective proteins detected in tissue microsomes of both humans and mice.These information on P450-dependent drug-metabolising characteristics in hepatic and extrahepatic tissues is useful to understand the similarities and differences between humans and mice in drug metabolism.

Selection of the candidate compound at an early stage of new drug development: retrospective pharmacokinetic and metabolic evaluations of valsartan using common marmosets.

Valsartan is an antihypertensive drug that was developed using common marmosets (Callithrix jacchus) in pivotal toxicity studies as a non-rodent species. The aim of the present study was to investigate the utility of marmosets in the candidate selection of this drug from a pharmacokinetic and metabolic viewpoint.Valsartan, as well as three other angiotensin II type-I receptor blockers, assumed as competitive candidates, were administered to common marmosets. Human pharmacokinetic parameters predicted by single-species allometric scaling and Wajima superposition suggested that valsartan may exhibit promising pharmacokinetic properties in humans.In vitro metabolic studies of valsartan using isolated rat, dog, marmoset, cynomolgus monkey, and human hepatocytes revealed that the marmoset was the most relevant animal species to humans presenting with the most abundant human metabolite, 4-hydroxyvalsartan. Oral administration of an elevated dose of valsartan to a common marmoset demonstrated that the level of 4-hydroxyvalsartan in the plasma was comparable to that in clinical practice and suggested that safety of the human metabolite might have been confirmed in the toxicity studies using common marmosets.These results suggest that common marmosets, the small, non-human primates, had been a suitable species for the development of valsartan.

Metabolic Profiles of Tetrabromobisphenol A in Humans Extrapolated from Humanized-Liver Mouse Data Using a Simplified Physiologically Based Pharmacokinetic Model.

Tetrabromobisphenol A, a brominated flame retardant, is increasingly prevalent worldwide and presents a potential health risk. Adjusted animal biomonitoring equivalents of tetrabromobisphenol A after orally administered doses in humanized-liver mice were scaled up to humans using known species allometric scaling factors to set up simplified physiologically based pharmacokinetic (PBPK) models. Absorbed tetrabromobisphenol A was slightly, moderately, and extensively metabolized in vivo to its glucuronide in rats, control mice, and humanized-liver mice tested, respectively. In silico estimated hepatic exposures of tetrabromobisphenol A and its glucuronide generated using the rat PBPK model-generated plasma concentration profiles were consistent with the reported values. The extent of hepatic injury in humanized-liver mice caused by tetrabromobisphenol A was evaluated by detecting human albumin mRNA in mouse plasma after oral administration of a high dose of tetrabromobisphenol A (1000 mg/kg). Reverse dosimetry analyses were carried out using two human PBPK models (set up based on the humanized-liver-mouse model and by optimizing the input parameters for reported human plasma concentrations of tetrabromobisphenol A glucuronide) to estimate the tetrabromobisphenol A daily intake based on reported human serum concentrations of total tetrabromobisphenol A from biomonitoring data. Within the predictability of the forward and reverse dosimetry estimations, the calculated daily intake was found to be far below established health benchmark levels (i.e., the suggested daily reported reference dose) with a wide (4 orders of magnitude) safety margin. These results suggest that the simplified PBPK models can be successfully applied to forward and reverse dosimetry estimations of tissue and/or blood exposures of tetrabromobisphenol A in humans after oral doses.

Novel hepatitis B virus infection mouse model using herpes simplex virus type 1 thymidine kinase transgenic mice.

BACKGROUND AND AIM: The chronicity of hepatitis B virus (HBV) infection is the result of impaired HBV-specific immune responses that cannot eliminate or cure the infected hepatocytes efficiently. Previous studies have used immunodeficient mice such as herpes simplex virus type 1 thymidine kinase NOD/Scid/IL2Rrnull (HSV-TK-NOG) mice. However, it is difficult to analyze the immune response in the previous models. In the present study, we established a novel HBV infection model using herpes simplex virus type 1 thymidine kinase (HSV-TK) mice in which the host immune system was not impaired. METHODS: Herpes simplex virus type 1 thymidine kinase mice were injected intraperitoneally with ganciclovir (GCV). Seven days after GCV injection, GCV-treated mice were transplanted with 1 × 106 hepatocytes from HBV-transgenic (HBV-Tg) mice. RESULTS: Serum alanine aminotransferase levels in HSV-TK mice increased 1 and 2 weeks after GCV injection. The number and viability of hepatocytes from the whole liver of HBV-Tg mice significantly increased using digestion medium containing liberase. Hepatitis B surface antigen (HBsAg)-positive areas in the liver tissue were observed for at least 20 weeks after HBsAg-positive hepatocyte transplantation. In addition, we measured HBsAg in the serum after transplantation. HBsAg levels in HBV-Tg hepatocyte-replaced mice increased 4 weeks after transplantation. Furthermore, we examined the immune response in HSV-TK mice. The increase in hepatitis B surface antibody levels in replaced mice was maintained for 20 weeks. Also, interferon-γ-producing cells were increased in non-replaced mice. CONCLUSIONS: A novel HBV infection mouse model will help to understand the mechanisms of HBV tolerance similar to human chronic HBV-infected patients and can be used to develop a new strategy to treat chronic HBV infection.

UDP-glucuronosyltransferase 1A4-mediated N2-glucuronidation is the major metabolic pathway of lamotrigine in chimeric NOG-TKm30 mice with humanised-livers.

Lamotrigine is a phenyltriazine anticonvulsant used to treat epilepsy and bipolar disorder, with species-dependent metabolic profiles. In this study, we investigated the metabolism of lamotrigine in chimeric NOG-TKm30 mice transplanted with human hepatocytes (humanised-liver mice).Substantial lamotrigine N2-glucuronidation activities were observed in the liver microsomes from humanised-liver mice, humans, marmosets, and rabbits, compared to those from monkeys, minipigs, guinea pigs, rats, and mice. Lamotrigine N2-glucuronidation activities in the liver microsomes from humanised-liver mice were dose-dependently inhibited by hecogenin, a specific inhibitor of the human UGT1A4.The major metabolite in the hepatocytes from humanised-liver mice and humans was lamotrigine N2-glucuronide, whereas that in mouse hepatocytes was lamotrigine N2-oxide. After a single oral dose of lamotrigine (10 mg/kg), the plasma levels of N2-glucuronide, N5-glucuronide, and N2-methyl were higher in humanised-liver mice compared to that in NOG-TKm30 mice. Lamotrigine N2-glucuronide was the most abundant metabolite in the urine in humanised-liver mice, similar to that reported in humans; whereas, lamotrigine N2-oxide was predominantly excreted in the urine in NOG-TKm30 mouse.These results suggest that humanised-liver mice may be a suitable animal model for studying the UGT1A4 mediated-lamotrigine metabolism.

Methyl-hydroxylation and subsequent oxidation to produce carboxylic acid is the major metabolic pathway of tolbutamide in chimeric TK-NOG mice transplanted with human hepatocytes.

Tolbutamide is an oral anti-hyperglycaemic agent used to treat non-insulin-dependent diabetes mellitus with species-dependent metabolic profiles. In this study, we investigated tolbutamide metabolism in chimeric TK-NOG mice transplanted with human hepatocytes (humanised-liver mice).Substantial 4-hydroxytolbutamide and 4-carboxytolbutamide production was observed in hepatocytes from humanised-liver mice (Hu-Liver cells) and humans, whereas 4-carboxytolbutamide production was not detected in mouse hepatocytes. In Hu-Liver cells, 4-hydroxytolbutamide formation was inhibited by sulfaphenazole (CYP2C9 inhibitor), whereas 4-carboxytolbutamide formation was inhibited by raloxifene/ethinyloestradiol (aldehyde oxidase inhibitor) and disulfiram (aldehyde dehydrogenase inhibitor).After a single oral dose of tolbutamide (10 mg/kg), the plasma levels of 4-carboxytolbutamide and p-tolylsulfonylurea were higher in humanised-liver mice than in TK-NOG mice. Urinary excretion was the predominant route (>99% of unchanged drug and metabolites detected in excreta) of elimination in both groups. 4-Carboxytolbutamide was the most abundant metabolite in humanised-liver mouse urine, as similarly reported for humans, whereas 4-hydroxytolbutamide was predominantly excreted in TK-NOG mouse urine.These results suggest that humanised-liver mice might represent a suitable animal model for studying the successive oxidative metabolism of tolbutamide by multiple drug-metabolising enzymes. Future work is warranted to study the general nature of primary alcohol metabolism using humanised-liver mice.

Hepatotoxicological potential of P-toluic acid in humanised-liver mice investigated using simplified physiologically based pharmacokinetic models.

p-Toluic acid, a metabolite of organic solvent xylene, has a high reported no-observed-effect level (NOEL, 1000 mg/kg) in rats, possibly because of direct glycine conjugation to methylhippuric acid. In this study, plasma levels of p-toluic acid and its glycine conjugate in mice and humanised-liver mice were evaluated after oral administrations.Although rapid conversion of p-toluic acid to its glycine conjugate was evident from mouse plasma concentrations, the biotransformation of p-toluic acid was slower in humanised-liver mice. The input parameters for physiologically based pharmacokinetic (PBPK) models were determined using fitting procedures to create PBPK-generated plasma concentration curves.The PBPK-modelled hepatic concentrations of p-toluic acid in humanised-liver mice were higher than those observed in plasma. PBPK-modelled hepatic and plasma concentrations of p-toluic acid also indicated slow elimination in humans.These results suggest that rapid conjugations of p-toluic acid reportedly observed in rats could result in overestimation of NOELs for conjugatable chemicals when extrapolated to humanised-liver mice or humans.

Plasma and hepatic concentrations of acetaminophen and its primary conjugates after oral administrations determined in experimental animals and humans and extrapolated by pharmacokinetic modeling.

Plasma concentrations of acetaminophen, its glucuronide and sulfate conjugates, and cysteinyl acetaminophen were experimentally determined after oral administrations of 10 mg/kg in humanised-liver mice, control mice, rats, common marmosets, cynomolgus monkeys, and minipigs; the results were compared with reported human pharmacokinetic data. Among the animals tested, only rats predominantly converted acetaminophen to sulfate conjugates, rather than glucuronide conjugates. In contrast, the values of area under the plasma concentration curves of acetaminophen, its glucuronide and sulfate conjugates, and cysteinyl acetaminophen after oral administration of acetaminophen in marmosets and minipigs were consistent with those reported in humans under the present conditions. Physiologically based pharmacokinetic (PBPK) models (consisting of the gut, liver, and central compartments) for acetaminophen and its primary metabolite could reproduce and estimate, respectively, the plasma and hepatic concentrations of acetaminophen in experimental animals and humans after single virtual oral doses. The values of area under the curves of hepatic concentrations of acetaminophen estimated using PBPK models were correlated with the measured levels of cysteinyl acetaminophen (a deactivated metabolite) in plasma fractions in these species. Consequently, using simple PBPK models and plasma data to predict hepatic chemical concentrations after oral doses could be helpful as an indicator of in vivo possible hepatotoxicity of chemicals such as acetaminophen.

Highly efficient induction of primate iPS cells by combining RNA transfection and chemical compounds.

Induced pluripotent stem (iPS) cells hold great promise for regenerative medicine and the treatment of various diseases. Before proceeding to clinical trials, it is important to test the efficacy and safety of iPS cell-based treatments using experimental animals. The common marmoset is a new world monkey widely used in biomedical studies. However, efficient methods that could generate iPS cells from a variety of cells have not been established. Here, we report that marmoset cells are efficiently reprogrammed into iPS cells by combining RNA transfection and chemical compounds. Using this novel combination, we generate transgene integration-free marmoset iPS cells from a variety of cells that are difficult to reprogram using conventional RNA transfection method. Furthermore, we show this is similarly effective for human and cynomolgus monkey iPS cell generation. Thus, the addition of chemical compounds during RNA transfection greatly facilitates reprogramming and efficient generation of completely integration-free safe iPS cells in primates, particularly from difficult-to-reprogram cells.