A multicenter assessment of single-cell models aligned to standard measures of cell health for prediction of acute hepatotoxicity.

Assessing the potential of a new drug to cause drug-induced liver injury (DILI) is a challenge for the pharmaceutical industry. We therefore determined whether cell models currently used in safety assessment (HepG2, HepaRG, Upcyte and primary human hepatocytes in conjunction with basic but commonly used endpoints) are actually able to distinguish between novel chemical entities (NCEs) with respect to their potential to cause DILI. A panel of thirteen compounds (nine DILI implicated and four non-DILI implicated in man) were selected for our study, which was conducted, for the first time, across multiple laboratories. None of the cell models could distinguish faithfully between DILI and non-DILI compounds. Only when nominal in vitro concentrations were adjusted for in vivo exposure levels were primary human hepatocytes (PHH) found to be the most accurate cell model, closely followed by HepG2. From a practical perspective, this study revealed significant inter-laboratory variation in the response of PHH, HepG2 and Upcyte cells, but not HepaRG cells. This variation was also observed to be compound dependent. Interestingly, differences between donors (hepatocytes), clones (HepG2) and the effect of cryopreservation (HepaRG and hepatocytes) were less important than differences between the cell models per se. In summary, these results demonstrate that basic cell health endpoints will not predict hepatotoxic risk in simple hepatic cells in the absence of pharmacokinetic data and that a multicenter assessment of more sophisticated signals of molecular initiating events is required to determine whether these cells can be incorporated in early safety assessment.

Comparative Proteomic Characterization of 4 Human Liver-Derived Single Cell Culture Models Reveals Significant Variation in the Capacity for Drug Disposition, Bioactivation, and Detoxication.

In vitro preclinical models for the assessment of drug-induced liver injury (DILI) are usually based on cryopreserved primary human hepatocytes (cPHH) or human hepatic tumor-derived cell lines; however, it is unclear how well such cell models reflect the normal function of liver cells. The physiological, pharmacological, and toxicological phenotyping of available cell-based systems is necessary in order to decide the testing purpose for which they are fit. We have therefore undertaken a global proteomic analysis of 3 human-derived hepatic cell lines (HepG2, Upcyte, and HepaRG) in comparison with cPHH with a focus on drug metabolizing enzymes and transport proteins (DMETs), as well as Nrf2-regulated proteins. In total, 4946 proteins were identified, of which 2722 proteins were common across all cell models, including 128 DMETs. Approximately 90% reduction in expression of cytochromes P450 was observed in HepG2 and Upcyte cells, and approximately 60% in HepaRG cells relative to cPHH. Drug transporter expression was also lower compared with cPHH with the exception of MRP3 and P-gp (MDR1) which appeared to be significantly expressed in HepaRG cells. In contrast, a high proportion of Nrf2-regulated proteins were more highly expressed in the cell lines compared with cPHH. The proteomic database derived here will provide a rational basis for the context-specific selection of the most appropriate 'hepatocyte-like' cell for the evaluation of particular cellular functions associated with DILI and, at the same time, assist in the construction of a testing paradigm which takes into account the in vivo disposition of a new drug.

Increased survival despite failure of transplanted human hepatocyte implantation into liver parenchyma of nude mice with repeated lethal Jo2-induced liver deficiency.

We recently found that rat hepatocyte transplantation was efficient (liver repopulation: 2.4%) in a sublethal nude mouse model (less than 33% mortality) of repeated liver injury generated using Jo2, a mouse-specific anti-Fas antibody, at sublethal dose of 250 µg/kg for 3 weeks. Genomic analysis of the livers revealed cell cycle blockade and an antiproliferative status of circadian genes, suggesting a selective advantage. By contrast, in the present study, freshly isolated human hepatocyte transplantation performed in the same mouse model resulted in implantation of less than 6,000 cells per liver (about 0.006% repopulation) in all animals. Genomic analysis of nude mouse livers revealed a lack of P21 upregulation, while a signature of stimulation of liver regeneration was observed, including upregulation of early response genes and upregulation of circadian genes. When we translated this sublethal model to a lethal model (65% mortality) by increasing the Jo2 repeated doses to 375 µg/kg, human hepatocyte engraftment was still very low; however, animal mortality was corrected by transplantation (only 20% mortality). Genomic findings in livers from the mice of the lethal Jo2 transplanted group were similar to those of the sublethal Jo2 transplanted group, that is, no selective advantage genomic signature and signature of mouse liver regeneration. In conclusion, transplanted human hepatocytes acted as if they modified nude mouse liver responses to Jo2 by stimulating liver regeneration, leading to an increased survival rate.

Isolation and culture of primary hepatocytes from resected human liver tissue.

As our knowledge of the species differences in drug metabolism and drug-induced hepatotoxicity has expanded significantly, the need for human-relevant in vitro hepatic model systems has become more apparent than ever before. Human hepatocytes have become the "gold standard" for evaluating hepatic metabolism and toxicity of drugs and other xenobiotics in vitro. In addition, they are becoming utilized more extensively for many kinds of biomedical research, including a variety of biological, pharmacological, and toxicological studies. This chapter describes methods for the isolation of primary human hepatocytes from liver tissue obtained from an encapsulated end wedge removed from patients undergoing resection for removal of liver tumors or from resected segments from whole livers obtained from multi-organ donors. In addition, methods are described for culturing primary hepatocytes under various matrix compositions and geometries, which reestablish intercellular contacts and normal cellular architecture for optimal phenotypic gene expression and response to drugs and other xenobiotics in vitro. Overall, improved isolation, cultivation, and preservation methods have expanded the number of applications for primary human hepatocytes in basic research, which has allowed for exciting advances in our understanding of the biochemical and molecular mechanisms of human liver toxicity and disease.

Improved xenogenic hepatocyte implantation into nude mouse liver parenchyma with acute liver failure when followed by repeated anti-Fas antibody (Jo2) treatment.

Hepatocyte transplantation is a promising therapy for acute liver failure in humans. Recently, we succeeded in inducing various acute and chronic liver failures in nude mice. Engraftment of transplanted xenogeneic rat hepatocytes, visualized in the host liver by anti-MHC class I immunohistochemistry, revealed that liver repopulation was limited, and equivalent in nude mice with and without acute liver failure. In the present study, acute liver failure was induced in nude mice by a single injection of sublethal anti-Fas antibody Jo2, followed 24 h later by rat hepatocyte transplantation and than by a weekly repeated injection of Jo2. Rat hepatocyte engraftment into the recipient liver parenchyma 3 weeks following hepatocyte transplantation was about sevenfold increased when nude mice were subsequently subjected to weekly repeated Jo2 injection. Genomic analysis of these mice showed an overall transcriptome profile of upregulation of cellular cycle blocking transcripts, activation of liver injury inducing IFN-gamma/STAT1 pathway, and circadian transcript signature of antiproliferative cell status compared to mice submitted to hepatocyte transplantation only. The findings of the present study suggest that the induction of cell proliferation blockade in recipient livers could promote sufficient engraftment of transplanted hepatocytes to allow transient or definitive treatment of liver failure in humans.

Isolation and culture of primary human hepatocytes.

As our knowledge of the species differences in drug metabolism and drug-induced hepatotoxicity has expanded significantly, the need for human-relevant in vitro hepatic model systems has become more apparent than ever before. Human hepatocytes have become the "gold standard" for evaluating hepatic metabolism and toxicity of drugs and other xenobiotics in vitro. In addition, they are becoming utilized more extensively for many kinds of biomedical research, including a variety of biological, pharmacological, and toxicological studies. This chapter describes methods for the isolation of primary human hepatocytes from liver tissue obtained from an encapsulated end wedge removed from patients undergoing resection for removal of liver tumors or resected segments from whole livers obtained from multiorgan donors. The maintenance of normal cellular physiology and intercellular contacts in vitro is of particular importance for optimal phenotypic gene expression and response to drugs and other xenobiotics. As such, methods are described for culturing primary hepatocytes under various matrix compositions and geometries. Differential expression of liver-selective properties occurs over time in primary hepatocytes dependent on the culture and study conditions. Overall, improved isolation and cultivation methods have allowed for exciting advances in our understanding of the pathology, biochemistry, and cellular and molecular biology of human hepatocytes.

Hydrogel networks of poly(ethylene oxide) star-molecules supported by expanded polytetrafluoroethylene membranes: characterization, biocompatibility evaluation and glucose diffusion characteristics.

The present work discusses the grafting by electron beam irradiation of poly(ethylene oxide) (PEO) star-shaped polymers onto porous expanded polytetrafluoroethylene (EXPTFE) surfaces. The resulting materials are intended to combine the good biocompatible properties of PEO with the outstanding mechanical properties of PTFE. The star-shaped PEOs were synthesized via anionic polymerization. 3 Mev electron beam irradiation was applied to graft these PEO stars onto porous EXPTFE surfaces. The hydrophobic EXPTFE surface had to be pre-modified with N-vinylpyrrolidone. ESCA was used to quantify the amount of grafted star-shaped PEO. Unmodified EXPTFE surfaces are well known, when implanted in a body, to be rapidly covered by a layer of cells and fibrin. The EXPTFE coated with PEO were implanted in the peritoneal cavity of rats (or under the back skin). This implantation did not induce any inflammation reactions and SEM analysis had attested the absence of adsorbed cells and fibrin. The glucose diffusion properties of these membranes were studied by a lag time analysis method and compared to those of pure PEO hydrogels. As expected, glucose diffuses through the hydrogel coated membrane and diffusion is not affected by the presence of the EXPTFE membrane.

Tissue collection, transport and isolation procedures required to optimize human hepatocyte isolation from waste liver surgical resections. A multilaboratory study.

BACKGROUND: The European Center for Validation of Alternative Methods (ECVAM) has funded a prevalidation study in three laboratories (France, USA and UK) on the use of human hepatocyte cultures to predict cytochrome P-450 induction. AIMS AND METHODS: As first stage of this prevalidation study, the purpose of the present work was to set criteria for optimization and harmonization of hepatocyte isolation from human tissue among laboratories to establish a routine procedure. This was achieved by combining and/or comparing the data generated by the two independent European laboratories (France and UK). RESULTS: The results confirmed that surgical waste material is a valuable source for obtaining high quality hepatocytes under certain pre-, intra- and post-operative conditions: cell yield of viable hepatocytes was not significantly affected by age and sex of patients, nor indications for resection, steatosis or cholestasis. Cold ischeamia up to 5 hours did not influence viable cell yield allowing transport of material. CONCLUSION: The use of biopsy sizes between 50-100 g, cannulation with 2-4 cannulae, digestion with collagenase-containing digestion medium at a flow rate of 25 ml/cannula for 20 minutes, with cut surface being glued in order to reform Glisson's capsule, should optimize the total yield of viable human hepatocytes obtained per preparation of waste liver surgical resections.

Avaliação do estado energético de enxertos hepáticos após perfusão hipotérmica contínua ou conservação simples com solução universidade de wisconsin modificada / Effect on energy status of liver grafts preserved with modified UW solution by hypothermic continuous perfusion or simple storage

Racional - O transplante hepático representa, atualmente, o tratamento de escolha para doenças hepáticas crônicas irreversíveis, em estado terminal. Seu sucesso está ligado a diferentes fatores, dentre os quais se inclui uma eficiente conservação do enxerto hepático. A perfusão hipotérmica contínua do enxerto hepático demonstrou experimentalmente ampliar o período de conservação do fígado para além dos limites clinicamente atingidos. A resistência do fígado a períodos mais prolongados de conservação parece estar relacionada aos níveis energéticos das células. Objetivos - Verificar se melhores níveis energéticos de enxertos hepáticos são obtidos com o acréscimo dos aminoácidos glutamina, ácido glutâmico, cisteína, alanina e glicina à solução de conservação em perfusão hipotérmica contínua. Material e Método - Vinte porcos da raça Large-White foram operados após 12 horas de jejum. Seis dos fígados retirados foram preservados por 24 horas pelo método da conservação simples, três com a solução Universidade de Wisconsin, chamada BASE, e três com a mesma solução acrescida dos aminoácidos supracitados. Quatorze fígados foram conservados pelo método da perfusão hipotérmica contínua, metade deles com a solução BASE e outra metade com a solução acrescida de aminoácidos. A avaliação do estado emergético do fígado foi feita pela dosagem tecidual dos nucleotídeos adenílicos e glicogênio. O glutation foi também medido no tecido hepático tendo em vista sua importância como neutralizador de radicais livres de oxigênio. Resultados - O glicogênio hepático não se alterou com o uso de aminoácidos na solução ou com o método de preservação (CS ou PHC). O glutation, elevou sua concentração durante conservação simples com solução com aminoácidos,mas não se alterou com a perfusão contínua. O ATP manteve-se estável no tecido hepático, quando a perfusão contínua foi utilizada, mas reduziu-se rapidamente com a conservação simples. A perfusão contínua manteve estável a carga energética e a carga total em nucleotídeos adenílicos do enxerto, durante o período de conservação. Conclusão - O estudo demonstrou que a perfusão hipotérmica contínua foi capaz de manter os níveis energéticos iniciais do tecido hepático, independentemente da solução utilizada, enquanto que a conservação simples permitiu uma rápida queda nos níveis teciduais de trifosfato de adenosina.

Hepatocyte ploidy in regenerating livers after partial hepatectomy, drug-induced necrosis, and cirrhosis.

The hepatocyte ploidy was investigated by flow cytometry in regenerating Sprague-Dawley rat livers following either drug-induced acute necrosis (single sublethal doses of D-galactosamine or thioacetamide) or drug-induced chronic cirrhosis (repeated thioacetamide injections for 10-18 weeks) and in regenerating livers following 70% partial hepatectomy and was compared with that of normal hepatocytes. Twenty-four hours after partial hepatectomy, a significant decrease in 2n (1 diploid nucleus) hepatocytes and a significant increase in 8n (1 octoploid nucleus) hepatocytes occurred. In contrast, 24 h following induction of acute hepatic failure by single D-galactosamine or thioacetamide injections, a significant increase in 2n hepatocytes was observed, whereas the proportion of 8n hepatocytes remained unchanged. The liver ploidy returned to basal values within 21 days in all cases. In cirrhotic livers induced by chronic thioacetamide injections, the rate of 2n hepatocytes was about ten times that of the controls having the same age, while 4n (1 tetraploid nucleus) and 8n hepatocytes were one third of controls. The binucleation rate was also significantly decreased.

Failure of liver cirrhosis induction by thioacetamide in Nagase analbuminaemic rats.

Repeated administration of thioacetamide (TA), either intraperitoneally or in drinking water, produced liver cirrhosis in normal Sprague-Dawley rats (SDR) with significant histological alterations similar to those observed in human cirrhosis. In the present study, we evaluated the ability of TA to induce liver cirrhosis in mutant Nagase analbuminaemic SDR. Thioacetamide was administered either intraperitoneally up to 4 months or in drinking water up to 6 months to normal and to Nagase analbuminaemic SDR. Nagase analbuminaemic rats (NAR) were also administered TA in drinking water up to 10 months. Liver cirrhosis development was determined by macroscopic and microscopic analysis. In contrast to normal SDR, no histological characteristics of cirrhosis could be observed in NAR submitted to a 4 or 6 months treatment with TA. Such failure to induce cirrhosis in Nagase rats was confirmed even after prolonged TA administration in drinking water for up to 10 months. In contrast, fibrosis and cholangiolar proliferation occurred in the 10-month TA-treated analbuminaemic rats, suggesting that the mechanisms involved in cirrhosis induction are different from those involved in fibrosis development and carcinogenesis. It is unlikely that the protective effect against TA-induced cirrhosis observed in analbuminaemic rats is related to the absence of albumin in this rat strain, since a co-administration of TA with albumin in analbuminaemic rats did not restore the potential for TA to induce cirrhosis in this rat strain. In conclusion, the fact that induction of cirrhosis by TA is prevented in the inherently hyperlipidaemic and hypercholesterolaemic analbuminaemic rats could be considered for potential application in the treatment of clinical cirrhosis.