Application Of Bioartificial Liver Research Articles

Microencapsulated Hepatocytes Differentiated from Human Induced Pluripotent Stem Cells: Optimizing 3D Culture for Tissue Engineering Applications.

Liver cell therapy and in vitro models require functional human hepatocytes, the sources of which are considerably limited. Human induced pluripotent stem cells (hiPSCs) represent a promising and unlimited source of differentiated human hepatocytes. However, when obtained in two-dimensional (2D) cultures these hepatocytes are not fully mature and functional. As three-dimensional culture conditions offer advantageous strategies for differentiation, we describe here a combination of three-dimensional (3D) approaches enabling the successful differentiation of functional hepatocytes from hiPSCs by the encapsulation of hiPSC-derived hepatoblasts in alginate beads of preformed aggregates. The resulting encapsulated and differentiated hepatocytes (E-iHep-Orgs) displayed a high level of albumin synthesis associated with the disappearance of α-fetoprotein (AFP) synthesis, thus demonstrating that the E-iHep-Orgs had reached a high level of maturation, similar to that of adult hepatocytes. Gene expression analysis by RT-PCR and immunofluorescence confirmed this maturation. Further functional assessments demonstrated their enzymatic activities, including lactate and ammonia detoxification, as well as biotransformation activities of Phase I and Phase II enzymes. This study provides proof of concept regarding the benefits of combining three-dimensional techniques (guided aggregation and microencapsulation) with liver differentiation protocols as a robust approach to generate mature and functional hepatocytes that offer a permanent and unlimited source of hepatocytes. Based on these encouraging results, our combined conditions to produce mature hepatocytes from hiPSCs could be extended to liver tissue engineering and bioartificial liver (BAL) applications at the human scale for which large biomasses are mandatory.

Preclinical characterization of alginate-poly-L-lysine encapsulated HepaRG for extracorporeal liver supply.

We recently demonstrated that HepaRG cells encapsulated into 1.5% alginate beads are capable of self-assembling into spheroids. They adequately differentiate into hepatocyte-like cells, with hepatic features observed at Day 14 post-encapsulation required for external bioartificial liver applications. Preliminary investigations performed within a bioreactor under shear stress conditions and using a culture medium mimicking acute liver failure (ALF) highlighted the need to reinforce beads with a polymer coating. We demonstrated in a first step that a poly-l-lysine coating improved the mechanical stability, without altering the metabolic activities necessary for bioartificial liver applications (such as ammonia and lactate elimination). In a second step, we tested the optimized biomass in a newly designed perfused dynamic bioreactor, in the presence of the medium model for pathological plasma for 6 h. Performances of the biomass were enhanced as compared to the steady configuration, demonstrating its efficacy in decreasing the typical toxins of ALF. This type of bioreactor is easy to scale up as it relies on the number of micro-encapsulated cells, and could provide an adequate hepatic biomass for liver supply. Its design allows it to be integrated into a hybrid artificial/bioartificial liver setup for further clinical studies regarding its impact on ALF animal models.

HepaRG Self-Assembled Spheroids in Alginate Beads Meet the Clinical Needs for Bioartificial Liver.

In liver tissue engineering, cell culture in spheroids is now well recognized to promote the maintenance of hepatic functions. However, the process leading to spheroids formation is time consuming, costly, and not easy to scale-up for further use in human bioartificial liver (BAL) applications. In this study, we encapsulated HepaRG cells (precursors of hepatocyte-like cells) in 1.5% alginate beads without preforming spheroids. Starting from a given hepatic biomass, we analyzed cell differentiation and metabolic performance for further use in a fluidized-bed BAL. We observed that cells self-rearranged as aggregates within the beads and adequately differentiated over time, in the absence of any differentiating factors classically used. On day 14 postencapsulation, cells displayed a wide range of hepatic features necessary for the treatment of a patient in acute liver failure. These activities include albumin synthesis, ammonia and lactate detoxification, and the efficacy of the enzymes involved in the xenobiotic metabolism (such as CYP1A1/2). Impact statement It has been recognized that culturing cells in spheroids (SPHs) is advantageous as they better reproduce the three-dimensional physiological microenvironment. This approach can be exploited in bioartificial liver applications, where obtaining a functional hepatic biomass is the major challenge. Our study describes an original method for culturing hepatic cells in alginate beads that makes possible the autonomous formation of SPHs after 3 days of culture. In turn, the cells differentiate adequately and display a wide range of hepatic features. They are also capable of treating a pathological plasma model. Finally, this setup can easily be scaled-up to treat acute liver failure.

Efficient Generation of an Fah/Rag2 Dual-Gene Knockout Porcine Cell Line Using CRISPR/Cas9 and Adenovirus.

The shortage of human hepatocytes continues to be a significant limitation for the widespread application of hepatocyte transplantation and bioartificial liver (BAL) support therapy. Recombinant activation gene 2 (Rag2) and fumarylacetoacetate hydrolase (Fah)-deficient mice could be highly repopulated with human hepatocytes. However, Fah/Rag2-deficient mice can only produce up to 1 × 108 human hepatocytes per mouse. We hypothesized that 2-10 × 1010 human hepatocytes can be produced per Fah/Rag2-deficient pig, which is an adequate supply for hepatocyte transplantation and BAL therapy. In a novel approach, we used stably transfected Cas9 cells and single-guide RNA adenoviruses containing fluorescent reporters to enrich porcine cells with Fah/Rag2 dual gene mutations. This resulted in the construction of Fah/Rag2 double knockout porcine iliac artery endothelial cells, which were subsequently used for generating Fah/Rag2-deficient pigs.

Hydrophilic ZIF-8 decorated GO nanosheets improve biocompatibility and separation performance of polyethersulfone hollow fiber membranes: A potential membrane material for bioartificial liver application

The hydrophobic nature of zeolitic imidazole framework-8 (ZIF-8) nanoparticles restricts their use as additives in hollow fiber membranes (HFMs) for biomedical applications. In this study, hydrophilic ZIF-8 decorated graphene oxide nanosheets (ZGs) were synthesized and used as additives (0–1 wt%) in polyethersulfone (P) HFMs with the aim of improving the biocompatibility and separation performance so as to make the ZGP HFMs suitable for bioartificial liver (BAL) application. Elemental mapping and Fourier transform infrared studies confirmed the efficacious incorporation of ZG nanohybrids in the ZGP HFMs, which resulted in their improved hydrophilicity. The remarkably improved biocompatibility was experimentally demonstrated for the ZGP HFMs, which also were antioxidative and hemocompatible. There was a significantly high attachment and proliferation of HepG2 cells on these HFMs, and they showed remarkably high urea synthesis and albumin secretion. Further, the ZGP HFMs showed high ultrafiltration coefficient (392.2 ± 26.5 mL/h/m2/mm Hg), high flux recovery ratio (84.3%), low flux reduction (15.7%), and desirable molecular weight cutoff (125–135 kDa). Thus, these results experimentally demonstrated that the hydrophilic ZG nanohybrids improve the desirable properties of ZGP HFMs making them a potential biocompatible material for biomedical applications including BAL application.

Three-dimensional multiscale fiber matrices: development and characterization for increased HepG2 functional maintenance for bio-artificial liver application.

The development of a cell-growth substrate that provides a nature-like microenvironment, promotes cell adhesion, and maintains the cells' functional activities is a research focus in the field of tissue engineering. In the present study, three-dimensional micro-nano multiscale fiber-based substrates were developed by depositing biocompatible polycaprolactone (PCL)/PCL-Chitosan (C)/PCL-C-Gelatin (G) electrospun nanofibers (NFs) on the outer surface of hollow fiber membranes (HFMs) in one step. A comparison study with regard to physico-chemical characterization, hemocompatibility, cytotoxicity, and cellular functionality was performed with the developed matrices. The PCL-C-G NFs-deposited HFMs-based matrix showed superior hemocompatibility for blood-contact applications. The cytotoxicity of these matrices was found to be minimal. HepG2 cells exhibited an exceptionally robust adherence and proliferated growth on the matrix with the formation of characteristic multi-cellular spheroids. Furthermore, cell functional activities such as albumin secretion, urea synthesis, and cytochrome P450 specific activity were measured for the developed matrices. The developed three-dimensional multiscale fibers-based matrix can be a potential membrane for bioreactor and bio-artificial liver applications.

Optimizing combination of liver-enriched transcription factors and nuclear receptors simultaneously favors ammonia and drug metabolism in liver cells

The HepG2 cell line is widely used in studying liver diseases because of its immortalization, but its clinical application is limited by its low expression of the urea synthesis key enzymes and cytochromes P450 (CYPs). On the basis of our previous work, we investigated the transcriptional regulation of arginase 1 (Arg1) and ornithine transcarbamylase (OTC) in HepG2 cells. We also screened for the optimal combination of liver enrichment transcription factors (LETFs) and xenobiotic nuclear receptors that can promote the expression of key urea synthases and five major CYPs in HepG2 cells. Thus, recombinant HepG2 cells were established. Results showed that C/EBPβ, not C/EBPα, could upregulate expression of Arg1 and PGC1α and HNF4α cooperatively regulate the expression of OTC. The two optimal combinations C/EBPβ+HNF4α+HNF6+PXR and C/EBPβ+HNF4α+HNF6+CAR were selected. Compared with the control cells, the recombinant HepG2 cells modified by the two optimal combinations exhibited enhanced ammonia metabolism and CYP enzyme activity. Moreover, the HepG2/(C/EBPβ+HNF4α+HNF6+PXR) cells more strongly reduced ammonia than any other combination tested in this study. The present work indicated that optimizing the combination of transcription factors will simultaneously promote hepatocyte ammonia metabolism and drug metabolism. The recombinant HepG2 liver cell line constructed by the optimal combination provided an improved alternative means for bioartificial liver applications and drug toxicity testing.

The development and status of bioartificial liver

Liver failure is a serious stage during liver disease development of which mobidity is high. There is no effective treatment at present.Artificial liver support system is one of the important methods to treat liver failure which includes non-biological artificial liver, biological artificial liver and hybrid artificial liver. Among the artificial liver devices. The bioartificial liver is the most similar artifical liver device to human liver in terms of detoxification, synthesis and metabolism currently.The complexity of human liver function makes the biological artificial liver facing great challenges in selection of liver seed cells, construction of bioreactor and the best combination with auxiliary device, which leads to the slow development of bioartificial liver. In order to provide theoretical support for the study of bioartificial liver, the current status and its development are reviewed in the following aspects, the source of seed cells, the construction of bioreactor, the combination of auxiliary devices and the clinical application of bioartificial liver in this article.

Cell Expansion During Directed Differentiation of Stem Cells Toward the Hepatic Lineage

The differentiation of human pluripotent stem cells toward the hepatocyte lineage can potentially provide an unlimited source of functional hepatocytes for transplantation and extracorporeal bioartificial liver applications. It is anticipated that the quantities of cells needed for these applications will be in the order of 109-1010 cells, because of the size of the liver. An ideal differentiation protocol would be to enable directed differentiation to the hepatocyte lineage with simultaneous cell expansion. We introduced a cell expansion stage after the commitment of human embryonic stem cells to the endodermal lineage, to allow for at least an eightfold increase in cell number, with continuation of cell maturation toward the hepatocyte lineage. The progressive changes in the transcriptome were measured by expression array, and the expression dynamics of certain lineage markers was measured by mass cytometry during the differentiation and expansion process. The findings revealed that while cells were expanding they were also capable of progressing in their differentiation toward the hepatocyte lineage. In addition, our transcriptome, protein and functional studies, including albumin secretion, drug-induced CYP450 expression and urea production, all indicated that the hepatocyte-like cells obtained with or without cell expansion are very similar. This method of simultaneous cell expansion and hepatocyte differentiation should facilitate obtaining large quantities of cells for liver cell applications.

Bifunctional Polysulfone-Chitosan Composite Hollow Fiber Membrane for Bioartificial Liver.

Hollow fiber membranes are widely used as assist devices for bioartificial liver application. Asymmetric porous polysulfone and polysulfone-tocopheryl polyethylene glycol succinate (Psf-TPGS) composite hollow fiber and flat membranes were prepared by phase inversion procedure and subsequently surface modified with chitosan using sulfonation with concentrated sulfuric acid. Sulfonation induces negative charge on the prepared membrane surface and facilitates the attachment of chitosan amine groups by electrostatic interaction. The surface modification of membrane is stable at room temperature as dictated by presence of nitrogen in XPS analysis and amide linkages in FT-IR spectra. Further, biological studies of the membranes were performed using HepG2 cell line. Chitosan is biocompatible and shows structural similarity to glycosaminoglycans, a native liver ECM component. The chitosan-modified composite Psf and Psf-TPGS membranes have shown enhanced attachment and proliferation of HepG2 cells on outer surface as confirmed by the cell counting, DNA content, confocal microscopy, and SEM micrographs. The cells form a 3D multicellular spheroid structure on the chitosan-modified membranes in significantly larger number as seen in the SEM micrographs. Also, the hemocompatibility of the modified composite membranes were comparable to the unmodified membranes. Thus, the chitosan-modified composite membranes we have developed are bifunctional and have the potential to be used in bioartifical liver application.

P0023 : Comparison of the C3A and HepaRG liver cell lines in monolayer and 3D for bioartificial liver application

P0023 : Comparison of the C3A and HepaRG liver cell lines in monolayer and 3D for bioartificial liver application

HepaRG microencapsulated spheroids in DMSO-free culture: novel culturing approaches for enhanced xenobiotic and biosynthetic metabolism.

The need for models that recapitulate liver physiology is perceived for drug development, study of liver disease and bioartificial liver support. The bipotent cell line HepaRG constitutes an efficient surrogate of liver function, yet its differentiated status relies on high concentrations of DMSO, which may compromise the study of drug metabolism and limit the applicability of this hepatic model. Herein, we present a three-dimensional (3D) strategy for the differentiation of HepaRG based on alginate microencapsulation of cell spheroids and culture in dimethyl sulfoxide (DMSO)-free conditions. A ratio of 2.9:1 hepatocyte-like to biliary-like cells was obtained in the 3D culture, with an improvement of 35.9% in the hepatocyte differentiation when compared with two-dimensional (2D) cultures. The expression of the hepatic identity genes HNF4α and PXR in 3D cultures was comparable to 2D differentiated cultures, while the expression of homeostatic-associated genes albumin and carbamoyl phosphate synthase 1 was higher in 3D. Moreover, the spheroids presented a polarized organization, exhibiting an interconnected bile canalicular network and excretory functionality, assessed by specific activity of MRP2. Importantly, despite variability in basal gene expression levels, the activity of the phase I enzymes cytochrome P450 family 3, subfamily A, polypeptide 4 and cytochrome P450 family 1, subfamily A, polypeptide 2 upon induction was comparable to differentiated 2D cultures and albumin production and ammonia detoxification were enhanced in 3D. The presented model is suitable for toxicological applications, as it allows high throughput analysis of multiple compounds in a DMSO-free setting. Due to the high xenobiotic metabolism and maintenance of biosynthetic functions, the applicability of this model might be broadened to understand liver physiology and for bioartificial liver applications.

Glycyrrhetinic Acid-Based Thermoresponsive Hydrogel As a Synthetic Extracellular Matrix for Hepatocyte Culture and Recovery

Glycyrrhetinic acid-based thermoresponsive hydrogels P(NIPAAm-co-GAA) were prepared and used to promote initial cell adhesion, growth, and recovery by lowering temperature for further tissue engineering or bioartificial liver applications. The compositions, morphologies and properties of hydrogels were characterized by element analysis, scanning electron microscopy (SEM), and water contact angle measurement (WCA), respectively. P(NIPAAm-co-GAA) hydrogels exhibited a shift between hydrophilicity and hydrophobicity by controlling temperature. Adhesion, growth, detachment, and physiological functions of human hepatocyte (HL-7702) cultured on P(NIPAAm-co-GAA) hydrogels were examined. The introduction of glycyrrhetinic acid (GA) with specific affinity to hepatocyte promoted the adhesion and proliferation of HL-7702 cells effectively. Importantly, HL-7702 cells cultured on P(NIPAAm-co-GAA) hydrogels maintained high levels of urea and albumin synthesis. HL-7702 cells grown on P(NIPAAm-co-GAA) hydrogels can also be recovered spontaneously by only reducing culture temperature without any damage. Furthermore, the behaviors of HL-7702 and human hepatoma cells (HepG2) on P(NIPAAm-co-GAA) hydrogels were evaluated comparatively. The result revealed that P(NIPAAm-co-GAA) hydrogels facilitated HL-7702 but inhibited the growth of HepG2. Glycyrrhetinic acid-based thermoresponsive hydrogel was shown to be a promising matrix for cultivation of functional hepatocytes.

Increased hepatic functionality of the human hepatoma cell line HepaRG cultured in the AMC bioreactor

The clinical application of a bioartificial liver (BAL) depends on the availability of a human cell source with high hepatic functionality, such as the human hepatoma cell line HepaRG. This cell line has demonstrated high hepatic functionality, but the effect of BAL culture on its functionality in time is not known. Therefore, we studied the characteristics of the HepaRG-AMC-BAL over time, and compared the functionality of the HepaRG-AMC-BAL with monolayer cultures of HepaRG cells, normalized for protein (bioactive mass) and DNA (cell number).Histological analysis of 14-day-old BALs demonstrated functional heterogeneity similar to that of monolayer cultures. Hepatic functionality of the HepaRG-AMC-BALs increased during 2–3 weeks of culture. The majority of the measured protein-normalized hepatic functions were already higher in day 14 BAL cultures compared to monolayer cultures, including ammonia elimination (3.2-fold), urea production (1.5-fold), conversion of 15N-ammonia into 15N-urea (1.4-fold), and cytochrome P450 3A4 activity (7.9-fold). Lactate production in monolayer cultures switched into lactate consumption in the BAL cultures, a hallmark of primary hepatocytes. When normalized for DNA, only cytochrome P450 3A4 activity was 2.5-fold higher in the BAL cultures compared to monolayer cultures and lactate production switched to consumption, whereas urea production and 15N-urea production were 1.5- to 2-fold lower. The different outcomes for protein and DNA normalized functions probably relate to a smaller cell volume of HepaRG cells when cultured in the AMC-BAL. Cell damage was 4-fold lower in day 14 BAL cultures compared to monolayer cultures. Transcript levels of cytochrome P450 1A2, 2B6, 3A4 and 3A7 genes and of regulatory genes hepatic nuclear factor 4α and pregnane X receptor increased in time in BAL cultures and reached higher levels than in monolayer cultures. Lastly, metabolism of amino acids, particularly the alanine consumption and ornithine production of HepaRG-AMC-BALs more resembled that of primary hepatocytes than monolayer HepaRG cultures.We conclude therefore that BAL culture of HepaRG cells increases its hepatic functionality, particularly when normalized for biomass, both over time, and compared to monolayer, and this is associated with a reduction in cell damage, upregulation of both regulatory and structural hepatic genes, and changes in amino-acid metabolism. These results underline the potential of HepaRG cells for BAL application.

Prospects for Creating Bioartificial Liver System with Induced Pluripotent Stem Cell Technology

Bioartificial liver (BAL) systems are designed to assist malfunctioning livers in patients with various liver diseases. Such systems are composed of a bioreactor device together with functional hepatocytes. It is expected that almost all liver functions, except for the secretion of bile, would be compensated for by BAL systems. Historically, a variety of cells have been studied as sources for the embedded hepatocytes in BAL applications. For example, primary human hepatocytes, immortalized cell lines of C3A human hepatoblastoma cells, liver progenitor cell line HepaRG and cryopreserved porcine hepatocytes have been researched [1-7]. Some of them have even been explored in clinical investigations [8-13]. On the other hand, the recent development of induced pluripotent stem (iPS) cell technology has enabled us to generate stem cells by genetic reprogramming of somatic cells, and differentiating them towards functional hepatocytes [14-18]. Recently, we reported preliminary data for an iPS cell-oriented BAL system and demonstrated the basic concept of this system [19]. Here, we summarize the advantages and disadvantages of iPS cell-oriented BAL systems. Problems awaiting solution before clinical application are also discussed.

The Effect of Rat Acute-Liver-Failure Plasma on HepaRG Cells

Purpose We recently demonstrated the high liver functionality of the human liver cell line HepaRG, including ammonia eliminating capacity, making it a valuable biocomponent of a bioartificial liver (BAL) to support patients with acute liver failure (ALF). This cell line further gains detoxification properties when cultured with dimethyl sulfoxide (DMSO). In this paper we describe whether its functionality is compromised by the toxic effects of ALF plasma, as has been shown for primary hepatocytes. Methods We exposed -DMSO and +DMSO HepaRG cultures during 16 hours to healthy plasma and ALF-rat plasma. The cultures were analyzed for lipid accumulation, cell leakage, apolipoprotein A-1 production, nitrogen metabolism and transcript levels of hepatic genes. Results The -DMSO cultures showed increased cell leakage after healthy and ALF plasma exposure in contrast to +DMSO cultures, but otherwise the -DMSO and +DMSO cultures were equally affected by exposure to the plasmas. Exposure to both plasmas caused lipid accumulation and decreased transcript levels of various hepatic genes. ALF plasma decreased urea cycle activity, but increased urea production from arginine by upregulated arginase 2. However, total ammonia elimination was not affected by exposure to either plasma, indicating its predominant elimination by fixation into amino acids. In addition, apolipoprotein A-1 production remained constant. Conclusions HepaRG cells are negatively affected by rat plasma, even of healthy origin. However, their ammonia eliminating capacity is relatively resistant, underlining their suitability for BAL application. DMSO pre-treatment may increase their viability in plasma.

Hepatocyte function within a stacked double sandwich culture plate cylindrical bioreactor for bioartificial liver system

Bioartificial liver (BAL) system is promising as an alternative treatment for liver failure. We have developed a bioreactor with stacked sandwich culture plates for the application of BAL. This bioreactor design addresses some of the persistent problems in flat-bed bioreactors through increasing cell packing capacity, eliminating dead flow, regulating shear stress, and facilitating the scalability of the bioreactor unit. The bioreactor contained a stack of twelve double-sandwich-culture plates, allowing 100 million hepatocytes to be housed in a single cylindrical bioreactor unit (7 cm of height and 5.5 cm of inner diameter). The serial flow perfusion through the bioreactor increased cell-fluid contact area for effective mass exchange. With the optimal perfusion flow rate, shear stress was minimized to achieve high and uniform cell viabilities across different plates in the bioreactor. Our results demonstrated that hepatocytes cultured in the bioreactor could re-establish cell polarity and maintain liver-specific functions (e.g. albumin and urea synthesis, phase I&II metabolism functions) for seven days. The single bioreactor unit can be readily scaled up to house adequate number of functional hepatocytes for BAL development.

Liver Progenitor Cell Line HepaRG Differentiated in a Bioartificial Liver Effectively Supplies Liver Support to Rats with Acute Liver Failure

A major roadblock to the application of bioartificial livers is the need for a human liver cell line that displays a high and broad level of hepatic functionality. The human bipotent liver progenitor cell line HepaRG is a promising candidate in this respect, for its potential to differentiate into hepatocytes and bile duct cells. Metabolism and synthesis of HepaRG monolayer cultures is relatively high and their drug metabolism can be enhanced upon treatment with 2% dimethyl sulfoxide (DMSO). However, their potential for bioartificial liver application has not been assessed so far. Therefore, HepaRG cells were cultured in the Academic Medical Center bioartificial liver (AMC-BAL) with and without DMSO and assessed for their hepatic functionality in vitro and in a rat model of acute liver failure. HepaRG-AMC-BALs cultured without DMSO eliminated ammonia and lactate, and produced apolipoprotein A-1 at rates comparable to freshly isolated hepatocytes. Cytochrome P450 3A4 transcript levels and activity were high with 88% and 37%, respectively, of the level of hepatocytes. DMSO treatment of HepaRG-AMC-BALs reduced the cell population and the abovementioned functions drastically. Therefore, solely HepaRG-AMC-BALs cultured without DMSO were tested for efficacy in rats with acute liver failure (n = 6). HepaRG-AMC-BAL treatment increased survival time of acute liver failure rats ∼50% compared to acellular-BAL treatment. Moreover, HepaRG-AMC-BAL treatment decreased the progression of hepatic encephalopathy, kidney failure, and ammonia accumulation. These results demonstrate that the HepaRG-AMC-BAL is a promising bioartificial liver for clinical application.

Evaluation of a reversibly immortalized human hepatocyte line in bioartificial liver in pigs

An appropriate cell source is essential for the clinical application of bioartificial liver (BAL) system. This study aimed to test a reversibly immortalized human hepatocyte line (HepLi-4) in our newly validated choanoid fluidized bed bioreactor based BAL in pigs with fulminant hepatic failure (FHF). 15 FHF pigs were allocated to three groups: a BAL group receiving BAL treatment with HepLi-4 cells; a sham BAL group receiving cell-free BAL treatment; and a FHF group receiving intensive care only. Expression of liver-specific genes in HepLi-4 cells before and after BAL was analyzed, adult human hepatocytes acted as a reference. In BAL group, Fischer index was higher and serum indirect bilirubin level was lower compared with two control groups. Survival time in BAL group was longer than that in two control groups, but the difference was not statistically significant. Gene expression analysis showed that the transcript levels of liver-specific genes in HepLi-4 were retained after BAL, but significant variations were observed between HepLi-4 and human hepatocytes. HepLi-4 showed beneficial metabolic effects on FHF pigs in BAL, but is still not an appropriate cell source for BAL. More insights into interpreting the conditions for hepatocyte differentiation are needed. Key words : Reversible immortalization, hepatocytes, bioartificial liver, fulminant hepatic failure.

The effect of rat acute-liver-failure plasma on HepaRG cells

We recently demonstrated the high liver functionality of the human liver cell line HepaRG, including ammonia eliminating capacity, making it a valuable biocomponent of a bioartificial liver (BAL) to support patients with acute liver failure (ALF). This cell line further gains detoxification properties when cultured with dimethyl sulfoxide (DMSO). In this paper we describe whether its functionality is compromised by the toxic effects of ALF plasma, as has been shown for primary hepatocytes. We exposed -DMSO and +DMSO HepaRG cultures during 16 hours to healthy plasma and ALF-rat plasma. The cultures were analyzed for lipid accumulation, cell leakage, apolipoprotein A-1 production, nitrogen metabolism and transcript levels of hepatic genes. The -DMSO cultures showed increased cell leakage after healthy and ALF plasma exposure in contrast to +DMSO cultures, but otherwise the -DMSO and +DMSO cultures were equally affected by exposure to the plasmas. Exposure to both plasmas caused lipid accumulation and decreased transcript levels of various hepatic genes. ALF plasma decreased urea cycle activity, but increased urea production from arginine by upregulated arginase 2. However, total ammonia elimination was not affected by exposure to either plasma, indicating its predominant elimination by fixation into amino acids. In addition, apolipoprotein A-1 production remained constant. HepaRG cells are negatively affected by rat plasma, even of healthy origin. However, their ammonia eliminating capacity is relatively resistant, underlining their suitability for BAL application. DMSO pre-treatment may increase their viability in plasma.