Microbiological safety of a novel bio-artificial liver support system based on porcine hepatocytes: a experimental study. Eur J Med Res. 2012;17:13. [PMID: 22632261 PMCID: PMC3419623 DOI: 10.1186/2047-783x-17-13]

Stem Cell-Based Strategies: The Future Direction of Bioartificial Liver Development

Acute liver failure (ALF) results from severe liver damage or end-stage liver disease. It is extremely fatal and causes serious health and economic burdens worldwide. Once ALF occurs, liver transplantation (LT) is the only definitive and recommended treatment; however, LT is limited by the scarcity of liver grafts. Consequently, the clinical use of bioartificial liver (BAL) has been proposed as a treatment strategy for ALF. Human primary hepatocytes are an ideal cell source for these methods. However, their high demand and superior viability prevent their widespread use. Hence, finding alternatives that meet the seed cell quality and quantity requirements is imperative. Stem cells with self-renewing, immunogenic, and differentiative capacities are potential cell sources. MSCs and its secretomes encompass a spectrum of beneficial properties, such as anti-inflammatory, immunomodulatory, anti-ROS (reactive oxygen species), anti-apoptotic, pro-metabolomic, anti-fibrogenesis, and pro-regenerative attributes. This review focused on the recent status and future directions of stem cell-based strategies in BAL for ALF. Additionally, we discussed the opportunities and challenges associated with promoting such strategies for clinical applications.

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.

In vitro safety and efficacy evaluation of a novel hybrid bioartificial liver system with simulated liver failure serum

BACKGROUND

Acute liver failure (ALF), which can potentially be treated with an artificial liver, is a fatal condition. The purpose of this study was to evaluate the safety and effectiveness of a novel hybrid bioartificial liver system (NHBLS) using simulated liver failure serum in vitro.

METHODS

The bioreactor in experimental group was cultivated with primary porcine hepatocytes, whereas in control group was not. Next, the simulated liver failure serum was treated using the NHBLS for 10 h. Changes in albumin (ALB), total bilirubin (TBIL), ammonia (Amm), total bile acid (TBA), creatinine (Cr), and blood urea nitrogen (BUN) were measured before treatment (0 h) and every 2 h during treatment. In addition, changes in NHBLS pressures, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lidocaine metabolism were also recorded.

RESULTS

The NHBLS worked steadily without unexpected occurrences during the treatment. Blood culture showed no bacterial growth after 7 days, and the endotoxin level was less than 0.5 EU. The TBIL, TBA, Cr, and BUN levels in both groups were markedly lower than those at 0 h (p < 0.05). The Amm level in experimental group was significantly lower than that in control group (p < 0.05). NHBLS pressures were also stable, and the hepatocytes in the bioreactor functioned well.

CONCLUSIONS

The preparation method for the simulated liver failure serum was optimized successfully, and the safety and effectiveness of the NHBLS in vitro were verified. Furthermore, the NHBLS significantly reduced the levels of Amm which can lead to hepatic encephalopathy.

Establishment of gene-edited pigs expressing human blood-coagulation factor VII and albumin for bioartificial liver use

BACKGROUND AND AIM

Bioartificial livers (BALs) are considered as a solution to bridge patients with acute liver failure to liver transplantation or to assist in spontaneous recovery for patients with end-stage liver disease. Pig is the best donor of hepatocytes for BALs in clinical trials, because metabolic and detoxification function of its liver are close to human. However, using pig hepatocytes for BALs remains controversial for safety concern owing to nonhuman proteins secretion. Herein, we attempt to establish modified pigs expressing humanized liver proteins, blood-coagulation factor VII (F7), and albumin (ALB). These pigs should also be porcine endogenous retrovirus subtype C (PERV-C) free so that their ability of transmitting PERV to human could be diminished seriously.

METHODS

We devised both homology-dependent and independent knock-in approaches to insert a fusion of hF7 and hALB gene downstream the site of pig endogenous F7 promoter in pig fetal fibroblasts negative for PERV-C. The modified pigs were then generated through somatic cell nuclear transfer.

RESULTS

We obtained 14 and 10 cloned pigs by homology-dependent and independent approaches, respectively. Among them, 19 cloned pigs were with expected gene modification and 13 are alive to date. These modified pigs can successfully express hF7 and hALB in the liver and serum, and the expressed hF7 exhibits normal coagulation activity.

CONCLUSIONS

The gene-edited pigs expressing hF7 and hALB in the liver were generated successfully. We anticipate that our pigs could provide an alternative cell source for BALs as a promising treatment for patients with acute liver failure.

[Progress in hepatocyte status detection and its application in bioartificial liver support system]

Bioartificial liver support system (BALSS) provides a new way to treat liver failure and leaves more time for patients who are waiting for liver transplantation. It has detoxification function as well as the human liver, at the same time it can provide nutrition and improve the internal environment inside human body. Bioreactors and hepatocytes with good biological activity are the cores of BALSS which determine the treatment effect. However, in the course of prolonged treatment, the function and activity of hepatocytes might be greatly changed which could influence the efficacy. Therefore, it is very important to detect the status of the hepatocytes in BALSS. This paper presents some common indicators of cell activity, detoxification and synthetic functions, and also introduces the commonly detection methods corresponding to each indicator. Finally, we summarize the application of detection methods of the hepatocyte status in BALSS and discuss its development trend.

Performance of cold-preserved rat liver Microorgans as the biological component of a simplified prototype model of bioartificial liver

AIM

To develop a simplified bioartificial liver (BAL) device prototype, suitable to use freshly and preserved liver Microorgans (LMOs) as biological component.

METHODS

The system consists of 140 capillary fibers through which goat blood is pumped. The evolution of hematocrit, plasma and extra-fiber fluid osmolality was evaluated without any biological component, to characterize the prototype. LMOs were cut and cold stored 48 h in BG35 and ViaSpan^® solutions. Fresh LMOs were used as controls. After preservation, LMOs were loaded into the BAL and an ammonia overload was added. To assess LMOs viability and functionality, samples were taken to determine lactate dehydrogenase (LDH) release and ammonia detoxification capacity.

RESULTS

The concentrations of ammonia and glucose, and the fluids osmolalities were matched after the first hour of perfusion, showing a proper exchange between blood and the biological compartment in the minibioreactor. After 120 min of perfusion, LMOs cold preserved in BG35 and ViaSpan^® were able to detoxify 52.9% ± 6.5% and 53.6% ± 6.0%, respectively, of the initial ammonia overload. No significant differences were found with Controls (49.3% ± 8.8%, P < 0.05). LDH release was 6.0% ± 2.3% for control LMOs, and 6.2% ± 1.7% and 14.3% ± 1.1% for BG35 and ViaSpan^® cold preserved LMOs, respectively (n = 6, P < 0.05).

CONCLUSION

This prototype relied on a simple design and excellent performance. It’s a practical tool to evaluate the detoxification ability of LMOs subjected to different preservation protocols.

Improved survival of porcine acute liver failure by a bioartificial liver device implanted with induced human functional hepatocytes

Acute liver failure (ALF) is a life-threatening illness. The extracorporeal cell-based bioartificial liver (BAL) system could bridge liver transplantation and facilitate liver regeneration for ALF patients by providing metabolic detoxification and synthetic functions. Previous BAL systems, based on hepatoma cells and non-human hepatocytes, achieved limited clinical advances, largely due to poor hepatic functions, cumbersome preparation or safety concerns of these cells. We previously generated human functional hepatocytes by lineage conversion (hiHeps). Here, by improving functional maturity of hiHeps and producing hiHeps at clinical scales (3 billion cells), we developed a hiHep-based BAL system (hiHep-BAL). In a porcine ALF model, hiHep-BAL treatment restored liver functions, corrected blood levels of ammonia and bilirubin, and prolonged survival. Importantly, human albumin and α-1-antitrypsin were detectable in hiHep-BAL-treated ALF pigs. Moreover, hiHep-BAL treatment led to attenuated liver damage, resolved inflammation and enhanced liver regeneration. Our findings indicate a promising clinical application of the hiHep-BAL system.

No transmission of porcine endogenous retrovirus in an acute liver failure model treated by a novel hybrid bioartificial liver containing porcine hepatocytes

BACKGROUND

A novel hybrid bioartificial liver (HBAL) was constructed using an anionic resin adsorption column and a multi-layer flat-plate bioreactor containing porcine hepatocytes co-cultured with bone marrow mesenchymal stem cells (MSCs). This study aimed to evaluate the microbiological safety of the HBAL by detecting the transmission of porcine endogenous retroviruses (PERVs) into canines with acute liver failure (ALF) undergoing HBAL.

METHODS

Eight dogs with ALF received a 6-hour HBAL treatment on the first day after the modeling by D-galactosamine administration. The plasma in the HBAL and the whole blood in the dogs were collected for PERV detection at regular intervals until one year later when the dogs were sacrificed to retrieve the tissues of several organs for immunohistochemistry and Western blotting for the investigation of PERV capsid protein gag p30 in the tissue. Furthermore, HEK293 cells were incubated to determine the in vitro infectivity.

RESULTS

PERV RNA and reverse transcriptase activity were observed in the plasma of circuit 3, suggesting that PERV particles released in circuit 3. No positive PERV RNA and reverse transcriptase activity were detected in other plasma. No HEK293 cells were infected by the plasma in vitro. In addition, all PERV-related analyses in peripheral blood mononuclear cells and tissues were negative.

CONCLUSION

No transmission of PERVs into ALF canines suggested a reliable microbiological safety of HBAL based on porcine hepatocytes.

Detection of porcine endogenous retrovirus in xenotransplantation

Xenotransplantation can provide a virtually limitless supply of cells, tissues and organs for a variety of therapeutic procedures. Cells and tissues for use in human transplantation procedures could be supplied using material taken from pigs. However, there is a potential risk of transmission of porcine infectious agents, including porcine endogenous retroviruses (PERVs), to a novel human host, with as yet unknown consequences. Three subtypes of PERV have been identified, of which both PERV-A and PERV-B have the ability to infect human cells in vitro. The third subtype, PERV-C, does not show this ability. Recombinant PERV-A/C forms have demonstrated infectivity in human cell culture. Monitoring in xenotransplantation should comprise screening of the source pig herd (PERV-A and PERV-B level expression assessment, PERV-C detection) and screening of recipients (differentiation between PERV transmission and chimerism). The detection of PERVs includes analyses of both DNA and RNA (PCR and RT-PCR), quantitative determination of the level of PERV nucleic acids (real-time PCR and real-time RT-PCR), assessment of reverse transcriptase (RT) activity (RT assays) and viral and recipient protein detection (immunological methods). In summary, all available methods should be used in monitoring of PERVs in xenotransplantation, and caution should be exercised at all stages of monitoring. Such monitoring has enormous significance for eliminating the possibility of transmission of PERV infection, thus contributing to higher levels of safety in xenotransplantation.