The newly established human hepatocyte cell line: application for the bioartificial liver

Bioartificial livers: a review of their design and manufacture

Acute liver failure (ALF) is a rapidly progressive disease with high morbidity and mortality rates. Liver transplantation and artificial liver support systems, such as artificial livers (ALs) and bioartificial livers (BALs), are the two major therapies for ALF. Compared to ALs, BALs are composed of functional hepatocytes that provide essential liver functions, including detoxification, metabolite synthesis, and biotransformation. Furthermore, BALs can potentially provide effective support as a form of bridging therapy to liver transplantation or spontaneous recovery for patients with ALF. In this review, we systematically discussed the currently available state-of-the-art designs and manufacturing processes for BAL support systems. Specifically, we classified the cell sources and bioreactors that are applied in BALs, highlighted the advanced technologies of hepatocyte culturing and bioreactor fabrication, and discussed the current challenges and future trends in developing next generation BALs for large scale clinical applications.

Functional Analysis of Human Hepatocytes Isolated From Chimeric Mouse Liver

Chimeric mice with humanized liver were first established by transplanting primary human hepatocytes (PHHs) isolated from a Japanese 27-year-old donor into complementary DNA-urokinase-type plasminogen activator/severe combined immunodeficiency mice. The PHHs from the Japanese donor increased more than 100-fold in the mouse liver, and human hepatocytes purified from the chimeric mouse liver (hcPHs) were successfully transplanted into second-passaged mice. These PHHs and hcPHs can produce human albumin and preserve many liver-specific enzyme genes, which are important for liver function. Interestingly, hepatitis B virus can be infected with these chimeric mice; hepatitis B viral DNA and hepatitis B surface antigen levels were detectable. In conclusion, hcPHs can be an ideal cell source for analysis of human hepatocytes.

Hybrid bioartificial liver support in cynomolgus monkeys with D-galactosamine-induced acute liver failure

AIM: To evaluate a hybrid bioartificial liver support system (HBALSS) in cynomolgus monkeys with acute liver failure.

METHODS: To establish a model of acute liver failure, 0.3 g/kg of D-galactosamine was injected intravenously into cynomolgus monkeys. Chinese human liver cells were introduced into a perfusion bioreactor to carry out hybrid bioartificial liver support treatment. Forty-eight hours after the injection, one group of cynomolgus monkeys received HBALSS care, and a second experimental group received no treatment. Clinical manifestations of all animals, survival time, liver and kidney functions and serum biochemistry changes were recorded. Simultaneous detection of the number, viability and function of hepatocytes in the hybrid bioartificial liver were also performed.

RESULTS: Forty-eight hours after the injection of D-galactosamine, serum biochemistry levels were significantly increased, whereas albumin levels and the Fischer index were significantly reduced compared to baseline (all Ps < 0.05). Of the ten monkeys in the HBALSS treatment group, five survived, with an average duration of survival of 128 ± 3 h. All cynomolgus monkeys in the control group died, with a duration of survival of 112 ± 2 h. Survival time was significantly longer with HBALSS treatment (P < 0.05). Moreover, the number, viability and function of hepatocytes were maintained at a high level with HBALSS.

CONCLUSION: The novel hybrid bioartificial liver plays a significant role in liver support by significantly reducing serum biochemistry levels and extending animal survival time.

Advances in cell sources of hepatocytes for bioartificial liver

BACKGROUND

Orthotopic liver transplantation (OLT) is the most effective therapy for liver failure. However, OLT is severely limited by the shortage of liver donors. Bioartificial liver (BAL) shows great potential as an alternative therapy for liver failure. In recent years, progress has been made in BAL regarding genetically engineered cell lines, immortalized human hepatocytes, methods for preserving the phenotype of primary human hepatocytes, and other functional hepatocytes derived from stem cells.

DATA SOURCES

A systematic search of PubMed and ISI Web of Science was performed to identify relevant studies in English language literature using the key words such as liver failure, bioartificial liver, hepatocyte, stem cells, differentiation, and immortalization. More than 200 articles related to the cell sources of hepatocyte in BAL were systematically reviewed.

RESULTS

Methods for preserving the phenotype of primary human hepatocytes have been successfully developed. Many genetically engineered cell lines and immortalized human hepatocytes have also been established. Among these cell lines, the incorporation of BAL with GS-HepG2 cells or alginate-encapsulated HepG2 cells could prolong the survival time and improve pathophysiological parameters in an animal model of liver failure. The cBAL111 cells were evaluated using the AMC-BAL bioreactor, which could eliminate ammonia and lidocaine, and produce albumin. Importantly, BAL loading with HepLi-4 cells could significantly improve the blood biochemical parameters, and prolong the survival time in pigs with liver failure. Other functional hepatocytes differentiated from stem cells, such as human liver progenitor cells, have been successfully achieved.

CONCLUSIONS

Aside from genetically modified liver cell lines and immortalized human hepatocytes, other functional hepatocytes derived from stem cells show great potential as cell sources for BAL. BAL with safe and effective liver cells may be achieved for clinical liver failure in the near future.

Modifying three-dimensional scaffolds from novel nanocomposite materials using dissolvable porogen particles for use in liver tissue engineering

Background:

Although hepatocytes have a remarkable regenerative power, the rapidity of acute liver failure makes liver transplantation the only definitive treatment. Attempts to incorporate engineered three-dimensional liver tissue in bioartificial liver devices or in implantable tissue constructs, to treat or bridge patients to self-recovery, were met with many challenges, amongst which is to find suitable polymeric matrices. We studied the feasibility of utilising nanocomposite polymers in three-dimensional scaffolds for hepatocytes.

Materials and methods:

Hepatocytes (HepG2) were seeded on a flat sheet and in three-dimensional scaffolds made of a nanocomposite polymer (Polyhedral Oligomeric Silsesquioxane [POSS]-modified polycaprolactone urea urethane) alone as well as with porogen particles, i.e. glucose, sodium bicarbonate and sodium chloride. The scaffold architecture, cell attachment and morphology were studied with scanning electron microscopy, and we assessed cell viability and functionality.

Results:

Cell attachment to the scaffolds was demonstrated. The scaffold made with glucose particles as porogen showed a narrower range of pore size with higher porosity and better inter-pore communications and seemed to encourage near normal cell morphology. There was a steady increase of albumin secretion throughout the experiment while the control (monolayer cell culture) showed a steep decrease after day 7. At the end of the experiment, there was no significant difference in viability and functionality between the scaffolds and the control.

Conclusion:

In this initial study, porogen particles were used to modify the scaffolds produced from the novel polymer. Although there was no significance against the control in functionality and viability, the demonstrable attachment on scanning electron microscopy suggest potential roles for this polymer and in particular for scaffolds made with glucose particles in liver tissue engineering.

The HepaRG cell line is suitable for bioartificial liver application

For bioartificial liver application, cells should meet the following minimal requirements: ammonia elimination, drug metabolism and blood protein synthesis. Here we explore the suitability of HepaRG cells, a human cell line reported to differentiate into hepatocyte clusters and surrounding biliary epithelial-like cells at high density and after exposure to dimethyl sulfoxide (DMSO). The effect of carbamoyl-glutamate (CG), an activator of urea cycle enzyme carbamoylphosphate synthetase (CPS) was studied additionally. The effects of DMSO and/or CG were assessed in presence of (15)NH(4)Cl on HepaRG cells in monolayer. We tested hepatocyte-specific functions at transcript and biochemical level, cell damage parameters and performed immunostainings. Ureagenesis, ammonia/galactose elimination and albumin, glutamine synthetase and CPS transcript levels were higher in -DMSO than +DMSO cultures, probably due to a higher cell content and/or cluster-neighbouring regions contributing to their functionality. DMSO treatment increased cytochrome P450 (CYP) transcript levels and CYP3A4 activity, but also cell damage and repressed hepatic functionality in cluster-neighbouring regions. The levels of ammonia elimination, apolipoprotein A-1 production, and transcription of CYP3A4, CYP2B6 and albumin reached those of primary hepatocytes in either the + or -DMSO cultures. Preconditioning with CG increased conversion of (15)NH(4)Cl into (15)N-urea 4-fold only in -DMSO cultures. Hence, HepaRG cells show high metabolic and synthetic functionality in the absence of DMSO, however, their drug metabolism is only high in the presence of DMSO. An unparalleled broad hepatic functionality, suitable for bioartificial liver application, can be accomplished by combining CG treated -DMSO cultures with +DMSO cultures.

Establishment and characterization of immortalized porcine hepatocytes for the study of hepatocyte xenotransplantation

BACKGROUND

In light of the critical shortage of donor livers, xenogeneic sources offer the best alternative to human hepatocytes for the treatment of acute liver failure. This study investigated whether a combination of simian virus 40 large T antigen (SV40 LT) and human telomerase catalytic subunit (hTERT) genes could immortalize primary porcine hepatocytes that could reverse acute liver failure (ALF) in rats.

METHODS

We cotransfected SV40 LT and hTERT genes into primary porcine hepatocytes to examine the features of the transfected cell lines. We characterized the potentially therapeutic effect of immortalized porcine hepatocytes in a rat model of ALF induced by 90% hepatectomy.

RESULTS

An immortalized porcine hepatocyte cell line, HepLi, was expanded by >250 passages. HepLi cells maintained the defining characteristics of primary porcine hepatocytes, including porcine albumin secretion, urea production, and diazepam metabolism. Intrasplenic transplantation of HepLi cells significantly improved liver function, and significantly prolonging the survival of rats with ALF.

CONCLUSIONS

Cotransfection of SV40 LT and hTERT immortalized primary porcine hepatocytes without tumorigenicity in vitro. The Immortalized porcine hepatocytes served as a potential cell resource for xenotransplantation.

Bioartificial liver support systems

A variety of bioartificial liver support systems were developed to replace some of the liver's function in case of liver failure. Those systems, in contrast to purely artificial systems, incorporate metabolically active cells to contribute synthetic and regulatory functions as well as detoxification. The selection of the ideal cell source and the design of more sophisticated bioreactors are the main issues in this field of research. Several systems were already introduced into clinical studies to prove their safety. This review briefly introduces a cross-section of experimental and clinically applied systems and tries to give an overview on the problems and limitations of bioartificial liver support.

Role of growth factor receptor bound protein 7 in hepatocellular carcinoma

The human growth factor receptor-bound protein 7 (Grb7) is an adaptor molecule and is related to cell invasion. In this present study, we investigated the clinical and biological significance of Grb7 expression in human hepatocellular carcinoma (HCC). We reviewed 64 consecutive patients who had undergone liver resection for HCC, and we investigated the correlation between Grb7 expression and clinical outcome. To analyze the biological behavior of Grb7 in vitro and in vivo, we established Grb7 stable knockdown HCC cells using RNA interference technology. The positive staining of Grb7 protein was correlated with portal venous invasion (P < 0.01), hepatic venous invasion (P < 0.01), and intrahepatic metastasis (P < 0.05). Positive expression of Grb7 was significantly correlated with focal adhesion kinase (FAK) protein levels in HCC (P < 0.01). The Grb7- and FAK-positive group showed a significantly poorer prognosis as compared with the Grb7- and FAK-negative group (P < 0.05). Grb7 knockdown HCC cells exhibited significantly lower levels of invasion potential (P < 0.05) and motility (P < 0.05) than the control cells in vitro; moreover, Grb7 knockdown HCC cells showed delayed onset of the tumors compared with the control cells in vivo. Grb7 expression can modulate the invasive phenotype of HCC. Grb7 plays an important role in HCC progression and is strongly associated with expression of FAK. Grb7 could be a therapeutic target in HCC.

Treatment of acetaminophen-induced acute liver failure in the mouse with conditionally immortalized human hepatocytes

BACKGROUND/AIMS

Liver failure is a life threatening condition currently treated by palliative measures and, when applicable, organ transplantation. The use of a bioartificial organ capable of fulfilling the main functions of the liver would represent an attractive alternative. However, the shortage of suitable donor cells, and their limited growth ability have impeded the development of this strategy. We investigated whether lentiviral vectors allow for conditional immortalization of human hepatocytes and whether these immortalized hepatocytes could reverse lethal acute liver failure.

METHODS

We exposed primary human hepatocytes to Cre-excisable lentiviral vectors coding for SV40T Antigen, telomerase, and/or Bmi-1 and tested the functionality of the resulting cell lines. Therapeutic potential of immortalized hepatocytes were tested in a murine model of acetaminophen-induced hepatic injury.

RESULTS

The immortalized hepatocytes grew continuously yet were non-tumorigenic, stopped proliferating when exposed to Cre recombinase, and conserved defining properties of primary hepatocytes, including the ability to secrete liver-specific proteins and to detoxify drugs. The implantation of encapsulated immortalized human hepatocytes rescued mice from lethal doses of acetaminophen.

CONCLUSIONS

Lentiviral vectors represent tools of choice for immortalization of non-dividing primary cells, and lentivirally immortalized human hepatocytes are promising reagents for cell-based therapy of acute liver failure.