Maintained function of primary human hepatocytes by cellular interactions in coculture: implications for liver support systems

Extracellular vesicles released by steatotic hepatocytes alter adipocyte metabolism

The composition of extracellular vesicles (EVs) is altered in many pathological conditions, and their molecular content provides essential information on features of parent cells and mechanisms of crosstalk between cells and organs. Metabolic Syndrome (MetS) is a cluster of clinical manifestations including obesity, insulin resistance, dyslipidemia and hypertension that increases the risk of cardiovascular disease and type 2 diabetes mellitus. Here, we investigated the crosstalk between liver and adipocytes by characterizing EVs secreted by primary hepatocytes isolated from Zucker rat model, and studied the effect they have on 3T3-L1 adipocytes. We found that steatotic hepatocytes secrete EVs with significantly reduced exosomal markers in comparison with their lean counterpart. Moreover, proteomic analysis revealed that those EVs reflect the metabolic state of the parent cell in that the majority of proteins upregulated relate to fat metabolism, fatty acid synthesis, glycolysis, and pentose phosphate pathway. In addition, hepatocytes-secreted EVs influenced lipolysis and insulin sensitivity in recipient 3T3-L1 adipocytes. Untargeted metabolomic analysis detected alterations in different adipocyte metabolic pathways in cells treated with hepatic EVs. In summary, our work showed that steatosis has a significant impact in the amount and composition of EVs secreted by hepatocytes. Moreover, our data point to the involvement of hepatic-EVs in the development of pathologies associated with MetS.

Liver Tissue Engineering: Challenges and Opportunities

Liver tissue engineering aims at the possibility of reproducing a fully functional organ for the treatment of acute and chronic liver disorders. Approaches in this field endeavor to replace organ transplantation (gold standard treatment for liver diseases in a clinical setting) with in vitro developed liver tissue constructs. However, the complexity of the liver microarchitecture and functionality along with the limited supply of cellular components of the liver pose numerous challenges. This review provides a comprehensive outlook onto how the physicochemical, mechanobiological, and spatiotemporal aspects of the substrates could be tuned to address current challenges in the field. We also highlight the strategic advancements made in the field so far for the development of artificial liver tissue. We further showcase the currently available prototypes in research and clinical trials, which shows the hope for the future of liver tissue engineering.

Evaluation of a Flat Membrane Hepatocyte Bioreactor for Pharmacotoxicological Applications: Evidence that Inhibition of Spontaneously Produced Nitric Oxide Improves Cell Functionality

A laboratory-scale bioreactor was re-evaluated, with the aim of improving its use for the perfused culture of rat hepatocytes. In contrast to conventional culture systems, the flat membrane bioreactor (FMB) showed good functionality and biochemical competence during 2-3 days. Hepatocytes cultured in the FMB, specifically in a "sandwich" configuration, were functionally stable, as shown by a high rate of urea biosynthesis after challenge with NH4Cl, a low alanine-aminotransferase leakage and suppressed spontaneous nitric oxide (NO) production. Moreover, the time-course of the disappearance of cyclosporin A (CsA) from the perfusate demonstrated the high biotransformation capacity of cells in the FMB. The effect of CsA on the modulation of urea and spontaneous NO production demonstrated flexibility, in that minor changes could be observed at diverse time intervals and in a non-destructive way. The monitoring of nitrite levels during various steps of isolation and culture suggested that spontaneously produced NO has a negative impact on hepatocyte metabolic and functional integrity. In spite of the sophisticated techniques that are being used for the preparation of bioreactors, with hepatocytes surviving for longer periods, our data have shed light on some factors that could be important for the successful use of similar models for pharmacotoxicological and other biomedical applications.

Challenges on the road to a multicellular bioartificial liver

Over recent years, the progress in the development of a bioartificial liver (BAL) as an extracorporeal device or as a tissue engineered transplantable organ has been immense. However, many important BAL characteristics that are necessary to meet clinical demands have not been sufficiently addressed. This review describes the existing challenges in the development of a BAL for clinical applications, highlighting multicellularity and sinusoidal microarchitecture as crucial BAL characteristics to fulfil various liver functions. Currently available sources of nonparenchymal liver cells, such as endothelial cells, cholangiocytes and macrophages, used in BAL development are defined. Also, we discuss the recent studies on the reconstruction of the complex liver sinusoid microarchitecture using various liver cell types. Moreover, we highlight some other aspects of a BAL, such as liver zonation and formation of a vascular as well as biliary network for an adequate delivery, biotransformation and removal of substrates and waste products. Finally, the benefits of a multicellular BAL for the pharmaceutical industry are briefly described. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of Concentrated Fibroblast-Conditioned Media on In Vitro Maintenance of Rat Primary Hepatocyte

The effects of concentrated fibroblast-conditioned media were tested to determine whether hepatocyte function can be maintained without direct contact between hepatocytes and fibroblasts. Primary rat hepatocytes cultured with a concentrated conditioned media of NIH-3T3 J2 cell line (final concentration of 55 mg/ml) showed significantly improved survival and functions (albumin and urea) compared to those of control groups. They also showed higher expression levels of mRNA, albumin and tyrosine aminotransferase compared to hepatocyte monoculture. The results suggest that culture with concentrated fibroblast-conditioned media could be an easy method for in vitro maintenance of primary hepatocytes. They also could be contribute to understand and analyze co-culture condition of hepatocyte with stroma cells.

Transcriptome-Wide Analysis of Hepatitis B Virus-Mediated Changes to Normal Hepatocyte Gene Expression

Globally, a chronic hepatitis B virus (HBV) infection remains the leading cause of primary liver cancer. The mechanisms leading to the development of HBV-associated liver cancer remain incompletely understood. In part, this is because studies have been limited by the lack of effective model systems that are both readily available and mimic the cellular environment of a normal hepatocyte. Additionally, many studies have focused on single, specific factors or pathways that may be affected by HBV, without addressing cell physiology as a whole. Here, we apply RNA-seq technology to investigate transcriptome-wide, HBV-mediated changes in gene expression to identify single factors and pathways as well as networks of genes and pathways that are affected in the context of HBV replication. Importantly, these studies were conducted in an ex vivo model of cultured primary hepatocytes, allowing for the transcriptomic characterization of this model system and an investigation of early HBV-mediated effects in a biologically relevant context. We analyzed differential gene expression within the context of time-mediated gene-expression changes and show that in the context of HBV replication a number of genes and cellular pathways are altered, including those associated with metabolism, cell cycle regulation, and lipid biosynthesis. Multiple analysis pipelines, as well as qRT-PCR and an independent, replicate RNA-seq analysis, were used to identify and confirm differentially expressed genes. HBV-mediated alterations to the transcriptome that we identified likely represent early changes to hepatocytes following an HBV infection, suggesting potential targets for early therapeutic intervention. Overall, these studies have produced a valuable resource that can be used to expand our understanding of the complex network of host-virus interactions and the impact of HBV-mediated changes to normal hepatocyte physiology on viral replication.

Recent advances in 2D and 3D in vitro systems using primary hepatocytes, alternative hepatocyte sources and non-parenchymal liver cells and their use in investigating mechanisms of hepatotoxicity, cell signaling and ADME

This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro. In a complex architecture of nested, zonated lobules, the liver consists of approximately 80 % hepatocytes and 20 % non-parenchymal cells, the latter being involved in a secondary phase that may dramatically aggravate the initial damage. Hepatotoxicity, as well as hepatic metabolism, is controlled by a set of nuclear receptors (including PXR, CAR, HNF-4α, FXR, LXR, SHP, VDR and PPAR) and signaling pathways. When isolating liver cells, some pathways are activated, e.g., the RAS/MEK/ERK pathway, whereas others are silenced (e.g. HNF-4α), resulting in up- and downregulation of hundreds of genes. An understanding of these changes is crucial for a correct interpretation of in vitro data. The possibilities and limitations of the most useful liver in vitro systems are summarized, including three-dimensional culture techniques, co-cultures with non-parenchymal cells, hepatospheres, precision cut liver slices and the isolated perfused liver. Also discussed is how closely hepatoma, stem cell and iPS cell-derived hepatocyte-like-cells resemble real hepatocytes. Finally, a summary is given of the state of the art of liver in vitro and mathematical modeling systems that are currently used in the pharmaceutical industry with an emphasis on drug metabolism, prediction of clearance, drug interaction, transporter studies and hepatotoxicity. One key message is that despite our enthusiasm for in vitro systems, we must never lose sight of the in vivo situation. Although hepatocytes have been isolated for decades, the hunt for relevant alternative systems has only just begun.

Campylobacteremia in stage IV gliosarcoma with bevacizumab treatment

Primary campylobacter enteritis with secondary bacteremia was diagnosed in an immunocompromised patient with stage IV gliosarcoma. She developed mild diarrhea followed by systemic symptoms with transient generalized weakness and fever. She was treated with azithromycin and had a full recovery and without relapse through 2 months of follow-up. Her diagnosis was confirmed by a positive stool culture for Campylobacter sp. and blood culture for Campylobacter jejuni/coli.

Mesenchymal stromal cells as supportive cells for hepatocytes

Hepatocytes and hematopoietic stem cells (HSCs) appear to share many of the same requirements for their survival, functionality, and proliferation. This may be due to a shared location during fetal development. Moreover, hepatocytes and HSCs are unable to function, or even survive, without stromal cell support. Bone marrow-derived mesenchymal stromal cells (MSCs) support the proliferation and functionality, not only of HSCs, but also of hepatocytes. Although knowledge of the mechanisms underlying HSCs' support is far more advanced than for hepatocytes, data suggest that many agents important for HSCs also maintain the normal hepatocyte phenotype in vitro. Thus, it is possible that new techniques for the maintenance and expansion of HSCs may also be useful for hepatocytes. Bone marrow-derived MSCs are easily cultured and expanded in vitro, and some data suggest that they are immunoregulatory as well as relatively nonimmunogenic. These observations suggest that allogeneic MSCs may be useful not only in supporting hepatocyte growth and proliferation but also in modulating immune responses such as stellate cell activation.

Effect of human patient plasma ex vivo treatment on gene expression and progenitor cell activation of primary human liver cells in multi-compartment 3D perfusion bioreactors for extra-corporeal liver support

Cultivation of primary human liver cells in innovative 3D perfusion multi-compartment capillary membrane bioreactors using decentralized mass exchange and integral oxygenation provides in vitro conditions close to the physiologic environment in vivo. While a few scale-up bioreactors were used clinically, inoculated liver progenitors in these bioreactors were not investigated. Therefore, we characterized regenerative processes and expression patterns of auto- and paracrine mediators involved in liver regeneration in bioreactors after patient treatment. Primary human liver cells containing parenchymal and non-parenchymal cells co-cultivated in bioreactors were used for clinical extra-corporeal liver support to bridge to liver transplantation. 3D tissue re-structuring in bioreactors was studied; expression of proteins and genes related to regenerative processes and hepatic progenitors was analyzed. Formation of multiple bile ductular networks and colonies of putative progenitors were observed within parenchymal cell aggregates. HGF was detected in scattered cells located close to vascular-like structures, expression of HGFA and c-Met was assigned to biliary cells and hepatocytes. Increased expression of genes associated to hepatic progenitors was detected following clinical application. The results confirm auto- and paracrine interactions between co-cultured cells in the bioreactor. The 3D bioreactor provides a valuable tool to study mechanisms of progenitor activation and hepatic regeneration ex vivo under patient plasma treatment.

Significant contribution of liver nonparenchymal cells to metabolism of ammonia and lactate and cocultivation augments the functions of a bioartificial liver

A bioartificial liver (BAL) will bridge patients with acute liver failure (ALF) to either spontaneous regeneration or liver transplantation. The nitrogen metabolism is important in ALF, and the metabolism of nonparenchymal liver cells (NPCs) is poorly understood. The scope of this study was to investigate whether cocultivation of hepatocytes with NPCs would augment the functions of a BAL (HN-BAL) compared with a BAL equipped with only hepatocytes (H-BAL). In addition, NPCs were similarly cultivated alone. The cells were cultivated for 8 days in simulated microgravity with serum-free growth medium. With NPCs, initial ammonia and lactate production were fivefold and over twofold higher compared with later time periods despite sufficient oxygen supply. Initial lactate production and glutamine consumption were threefold higher in HN-BAL than in H-BAL. With NPCs, initial glutamine consumption was two- to threefold higher compared with later time periods, whereas initial ornithine production and arginine consumption were over four- and eightfold higher compared with later time periods. In NPCs, the conversion of glutamine to glutamate and ammonia can be explained by the presence of glutaminase, as revealed by PCR analysis. Drug metabolism and clearance of aggregated gamma globulin, probes administered to test functions of hepatocytes and NPCs, respectively, were higher in HN-BAL than in H-BAL. In conclusion, NPCs produce ammonia by hydrolysis of amino acids and may contribute to the pathogenesis of ALF. High amounts of lactate are produced by NPCs under nonhypoxic conditions. Cocultivation augments differentiated functions such as drug metabolism and clearance of aggregated gamma-globulin.

Present and Future Developments in Hepatic Tissue Engineering for Liver Support Systems : State of the art and future developments of hepatic cell culture techniques for the use in liver support systems

The liver is the most important organ for the biotransformation of xenobiotics, and the failure to treat acute or acute-on-chronic liver failure causes high mortality rates in affected patients. Due to the lack of donor livers and the limited possibility of the clinical management there has been growing interest in the development of extracorporeal liver support systems as a bridge to liver transplantation or to support recovery during hepatic failure. Earlier attempts to provide liver support comprised non-biological therapies based on the use of conventional detoxification procedures, such as filtration and dialysis. These techniques, however, failed to meet the expected efficacy in terms of the overall survival rate due to the inadequate support of several essential liver-specific functions. For this reason, several bioartificial liver support systems using isolated viable hepatocytes have been constructed to improve the outcome of treatment for patients with fulminant liver failure by delivering essential hepatic functions. However, controlled trials (phase I/II) with these systems have shown no significant survival benefits despite the systems' contribution to improvements in clinical and biochemical parameters. For the development of improved liver support systems, critical issues, such as the cell source and culture conditions for the long-term maintenance of liver-specific functions in vitro, are reviewed in this article. We also discuss aspects concerning the performance, biotolerance and logistics of the selected bioartificial liver support systems that have been or are currently being preclinically and clinically evaluated.

In vitro detection of differential and cell-specific hepatobiliary toxicity induced by geldanamycin and 17-allylaminogeldanamycin in rats

The differential toxicity of two anticancer agents is described using the in vitro rat liver slice culture model. Liver slices from F-344 rats were cultured for 5 days in Waymouth's-based medium with exposure to a range of geldanamycin (GEL) or 17-allylaminogeldanamycin (17-AAG) concentrations. GEL induced concentration-dependent reduction of alkaline phosphatase and of gamma-glutamyl transferase levels, which are indicators of biliary epithelial cell(s) (BEC) viability, and exhibited hepatocellular toxicity at higher concentrations. Histologically, BEC cell injury was evident at the lowest GEL concentration (0.1 microM) and progressed to overt bile duct necrosis at 5 microM, a level at which hepatocellular damage was also more prominent. Slices exposed to the same concentrations were more sensitive to toxic effects of GEL than of 17-AAG. 17-AAG at the lowest concentration had more slice biomarker retention than GEL, and histological analysis revealed minimal toxic effect on BEC. With increasing concentration, BEC were progressively lost, and BEC proliferation was completely inhibited at 5 microM 17-AAG. Hepatocellular injury was evident only at high dose exposures. This is believed to be the first use of an in vitro liver tissue model to accurately predict the differential and concentration-dependent toxicities of these compounds.

In vitro detection of differential and cell-specific hepatobiliary toxicity induced by geldanamycin and 17-allylaminogeldanamycin using dog liver slices

Experiments on rat liver slices demonstrated the differential hepatobiliary toxic potency of two anticancer agents, geldanamycin (GEL) and 17-allylaminogeldanamycin (17-AAG), over a 5-day period. This report describes the pattern of toxicity of these agents in dog liver tissue, using the in vitro liver slice culture model. Liver slices (200 microm thick) from male beagle dogs were cultured for 5 days in chemically defined culture medium containing a range of GEL and 17-AAG concentrations (0.1-5 microM). Tissues were evaluated using a panel of clinically relevant biomarkers and histological endpoints. GEL-induced reduction of alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) slice levels, indicators of biliary epithelial cell (BEC) viability, was supported by histological findings showing an increasing loss of BEC as higher concentrations were applied. At the highest concentrations studied, GEL caused both hepatocellular necrosis and BEC loss. Biomarker pattern results in the medium concurred with those from slice biochemistry measurements and histology. 17-AAG, a less potent compound in vivo, elicited more biomarker retention at higher concentrations than did GEL. Histological analysis revealed higher BEC viability and significant retention of BEC proliferation as compared with GEL. However, at the highest concentration, the toxic insult caused a marked decrease in BEC viability and proliferation. Comparison of responses with both compounds indicated that slices exposed to the same concentrations were more sensitive to GEL than to 17-AAG. Dog liver slices can thus be used to evaluate species-, compound-, and concentration-dependent differences in toxicity.

Factors influencing stem cell differentiation into the hepatic lineage in vitro

A major area of research in transplantation medicine is the potential application of stem cells in liver regeneration. This would require well-defined and efficient protocols for directing the differentiation of stem cells into the hepatic lineage, followed by their selective purification and proliferation in vitro. The development of such protocols would reduce the likelihood of spontaneous differentiation of stem cells into divergent lineages upon transplantation, as well as reduce the risk of teratoma formation in the case of embryonic stem cells. Additionally, such protocols could provide useful in vitro models for studying hepatogenesis and liver metabolism. The development of pharmokinetic and cytotoxicity/genotoxicity screening tests for newly developed biomaterials and drugs, could also utilize protocols developed for the hepatic differentiation of stem cells. Hence, this review critically examines the various strategies that could be employed to direct the differentiation of stem cells into the hepatic lineage in vitro.

In vitro production of functionally mature hepatocytes from prospectively isolated hepatic stem cells

Hepatocyte transplantation and artificial organ hepatic support require a number of functionally mature hepatocytes. However, their growth activity and functional behaviors are much smaller in culture after isolation from the liver. We examined whether continuously differentiating hepatocytes from multipotent hepatic stem cells that were isolated by using flow cytometry and propagated clonally in culture could be a source of clinical application. They actually gave rise to cells that were functionally equal to mature hepatocytes found in the adult liver, which secreted albumin into culture medium and metabolized harmful ammonium into urea. These data suggest that stem cell-derived hepatocytes are a useful cell source for developing therapeutic strategies, such as cell transplantation, gene therapy, and artificial liver organ to treat various liver disorders.

Review article: a medicine based on cell transplantation -- is there a future for treating liver diseases?

Cell-based therapies, comprising isolated hepatocyte transplantation, ex vivo gene therapy and bioartificial liver devices, may actually design a new scenario in the treatment of patients with liver failure. Recent advances in the liver repopulation field and the considerable excitement surrounding the use of haematopoietic stem cells for a 'regenerative medicine', allow us to see under a new light the alternative cell sources actually under investigation. In particular, the major drawbacks and the most important advantages of xenogenic primary cells, tumour-derived cell lines, immortalised hepatocytes and stem cells in the wide range of experimental and clinical applications are presented. Even if up to now none of them represent a 'gold standard' in the clinical practice, the intersecting advances in the development of mechanical components of artificial devices and in the liver biology and bioengineering will open tantalising possibilities to treat patients with liver failure, by tailoring the therapeutic choice on the basis of the aetiology and the stage of liver disease.

Large-scale expansion of mammalian neural stem cells: a review

A relatively new approach to the treatment of neurodegenerative diseases is the direct use of neural stem cells (NSCs) as therapeutic agents. The expected demand for treatment from the millions of afflicted individuals, coupled with the expected demand from biotechnology companies creating therapies, has fuelled the need to develop large-scale culture methods for these cells. The rapid pace of discovery in this area has been assisted through the use of animal model systems, enabling many experiments to be performed quickly and effectively. This review focuses on recent developments in expanding human and murine NSCs on a large scale, including the development of new serum-free media and bioreactor protocols. In particular, engineering studies that characterise important scale-up parameters are examined, including studies examining the effects of long-term culture of NSCs in suspension bioreactors. In addition, recent advances in the human NSC system are reviewed, including techniques for the evaluation of NSC characteristics.

Three-dimensional co-culture of primary human liver cells in bioreactors for in vitro drug studies: effects of the initial cell quality on the long-term maintenance of hepatocyte-specific functions

In vitro culture models that employ human liver cells could be potent tools for predictive studies on drug toxicity and metabolism in the pharmaceutical industry. A bioreactor culture model was developed that permits the three-dimensional co-culture of liver cells under continuous medium perfusion with decentralised mass exchange and integral oxygenation. We tested the ability of the system to support the long-term maintenance and differentiation of primary human liver cells. The effects of the initial cell quality were investigated by comparing cultures from resected, non-preserved liver with cultures from liver graft tissue damaged by long-term preservation. In cultures originating from non-preserved liver, protein and urea synthesis, glucose metabolism, and cytochrome (CYP450) activities were stable over the 2-week culture period, with maximal activities at the end of the first week in culture. Enzyme induction led to increased 7-ethoxyresorufin O-deethylase activities of up to 20 times the basal value. In cultures from preservation-damaged liver, recovery of metabolic activities was detected during bioreactor culture. After two weeks, most biochemical parameters approached those of cultures from non-preserved human liver. Light microscopy demonstrated the three-dimensional reorganisation of hepatocytes and non-parenchymal cells in co-culture. Long-term maintenance, and even the regeneration of specific functional activities of human liver cells, can be achieved in the bioreactor. This could facilitate the introduction into the pharmaceutical industry of in vitro drug testing with primary human liver cells.

Long-term culture of primary human hepatocytes with preservation of proliferative capacity and differentiated functions

BACKGROUND

The aim of this study was to develop a suitable method for the prolonged culture and maintenance of human hepatocytes with preservation of both proliferative capacity and differentiated functions.

MATERIALS AND METHODS

Primary human hepatocytes were isolated from small pieces of liver tissue obtained from 15 patients who underwent hepatic resection. Hepatocytes were cultured in keratinocyte-stimulating factor medium supplemented with 10% human serum, 10 mM nicotinamide, 10 ng/ml epidermal growth factor, 0.5 microg/ml insulin, 10(-7) M dexamethasone, and antibiotics. Hepatic differentiation and function were analyzed by immunocytochemistry, Western blot, ELISA, lidocaine metabolism, and urea synthesis. Ultrastructural analysis of cultured hepatocytes was performed by electron microscopy.

RESULTS

Many primary hepatocytes were maintained for more than 56 days. Hepatocytes proliferated during the initial 14 days, and bromodeoxyuridine labeling indices were 15.2, 12.2, and 6.2% at days 5, 10, and 15, respectively. Electron micrographs of the hepatocytes at day 28 demonstrated numerous mitochondria, rough endoplasmic reticulum, large peroxisomes, and glycogen granules. Albumin secretion increased for the first 14 days and then gradually decreased thereafter but was maintained at levels greater than 2 microg/ml/h until day 56. alpha(1)-Antitrypsin, alpha(1)-antichymotrypsin, and ceruloplasmin production was also observed at day 56, while lidocaine metabolism and urea synthesis were maintained for a long time.

CONCLUSION

This hepatocyte culture method facilitates the prolonged culture of primary human hepatocytes with preservation of hepatocyte differentiation, function, and proliferative capacity.

Recent developments on human cell lines for the bioartificial liver

Most bioartificial liver (BAL) devices contain porcine primary hepatocytes as their biological component. However, alternatives are needed due to xenotransplantation associated risks. Human liver cell lines have excellent growth characteristics and are therefore candidates for application in BAL devices. Tumour-derived cell lines HepG2 and C3A express a variety of liver functions, but some specific liver functions, like ammonia detoxification and ureagenesis are insufficient. Immortalised human hepatocytes might offer better prospects. The balance between immortalisation and transformation with dedifferentiation of cells seems controllable by conditional immortalisation and/or the use of telomerase as immortalising agent. Another promising approach will be the use of embryonic or adult human stem cells. Rodent stem cells have been directed to hepatic differentiation in vitro, which might be applicable to human stem cells. However, both functionality and safety of immortalised human liver cell lines and differentiated stem cells should be improved before successful use in BAL devices becomes reality.

Human hepatocyte cell lines proliferating as cohesive spheroid colonies in alginate markedly upregulate both synthetic and detoxificatory liver function

BACKGROUND/AIMS

Bio-artificial liver support systems for treatment of hepatic failure require maintained expression of hepatocyte function in vitro. We studied cultures of human hepatocyte cell-lines proliferating within alginate beads, investigating the hypothesis that 3-dimensional cohesive colonies of hepatocyte cell-lines would achieve polarity and cell-to-cell contact resulting in upregulation of function.

METHODS

HepG2 and HHY41 human cell lines in alginate beads were cultured for >20 days.

RESULTS

Proliferation was maintained for 20 days. Production of albumin, prothrombin, fibrinogen, alpha-1-acid glycoprotein and alpha-1-antitrypsin was maintained throughout, maximal at days 8-10, when upregulation was 300-1100% compared with monolayer cultures at similar cell number per unit volume. Detoxificatory functions: ethoxyresorufin deethylase activity, androstenedione metabolism, and urea synthesis from arginine was also increased several-fold. Function returned to pre-freezing levels within 18 h of thawing after cryopreservation of cells in alginate. Electron microscopy revealed spherical colonies of cells of cuboidal shape, with cell-to-cell contact via desmosomes and junctional complexes, abundant microvilli, and cytoplasmic appearances suggesting transcriptionally active hepatocytes.

CONCLUSION

Hepatocyte cell-lines, proliferating in alginate express a range of liver-specific functions at levels approaching those found in vivo, relevant to their use in liver support systems.