Bioartificial Liver Support Systems Research Articles

Bio-Artificial Liver Support System: A Prospective Future Therapy

Whether acute or chronic, liver failure is a state of liver dysfunction that can progress to multiorgan failure. Mortality in liver failure patients is approximately 80–90% and is caused by detoxification failure, which triggers other immediate complications, such as encephalopathy, coagulopathy, jaundice, cholestasis, and acute kidney failure. The ideal treatment for liver failure is liver transplantation, but the long waiting period for the right donor match causes unavoidable deaths in most patients. Therefore, new therapies, such as tissue engineering, hepatocyte transplantation, and stem cells, are now being studied to anticipate the patient’s condition while waiting for liver transplantation. This literature review investigated the effectiveness of some bio-artificial liver support systems using review methods systematically from international publication sites, including PubMed, using keywords, such as bio-artificial liver, acute and chronic liver failure, extracorporeal liver support system (ECLS), MARS, single-pass albumin dialysis (SPAD). Artificial and bioartificial liver systems can show specific detoxification abilities and pathophysiological improvements in liver failure patients but cannot reach the ideal criteria for actual liver function. The liver support system must provide the metabolic and synthetic function as in the actual liver while reducing the pathophysiological changes in liver failure. Aspects of safety, cost efficiency, and practicality are also considered. Identifying the technology to produce high-quality hepatocytes on a big scale is essential as a medium to replace failing liver cells. An increase in detoxification capacity and therapeutic effectiveness must also focus on patient survival and the ability to perform liver transplantation.

Optimization of decellularized liver matrix-modified chitosan fibrous scaffold for C3A hepatocyte culture.

Hepatocyte scaffold is an essential part in bioartificial liver device. We have designed a novel hepatocyte scaffold based on porcine liver extracellular matrix (ECM) and chitosan (CTS) fabrics. This CTS-ECM scaffold can improve cell adhesion and proliferation. In the present study, an orthogonal test was designed to optimize the CTS/ECM composite scaffold, in which ECM concentration, EDC concentration and EDC to NHS ratio were taken as factors, proportion of nitrogen element and hydroxyproline content as indicators. The cytocompatibility of the novel scaffold for C3A hepatocytes was analyzed in vitro. The orthogonal test demonstrated that the optimal scaffold should be based on ECM concentration of 5mg/mL, EDC concentration of 5mg/mL, and EDC to NHS ratio 1:1. C3A hepatocytes cultured on the optimized CTS-ECM scaffolds showed stronger proliferation and functionality than those on Cytodex3 microcarriers (p < 0.05). The CTS/ECM composite scaffold may be widely used as a promising hepatocyte culture carrier, especially in bioartificial liver support systems.

Improved Metabolic Pathways of Glycolysis, Glycogen Synthesis, the Urea Cycle, and Cytochrome Peroxidase Oxidative Reabsorption in a Miniature Bioreactor.

Bioreactor-based bioartificial liver support systems have had limited success in a translational setting and at preclinical stages. None of the existing systems monitor the metabolic pathways of glycolysis, glycogen synthesis, the urea cycle, and cytochrome peroxidase oxidative reabsorption. Herein, we designed a bioreactor that mimics the human liver microenvironment in vivo and monitors different hepatic metabolic pathways in order to help establish in vitro culture conditions for improved glycolysis, glycogen synthesis, the urea cycle, cytochrome peroxidase oxidative reabsorption and improved hepatic functions in a miniature bioartificial liver. An abnormality in such pathways negatively influences survivability and hepatic functions, including spontaneous liver regeneration. We investigated the metabolic functions of primary mouse adult hepatocytes cultured in a three-dimensional configuration under direct oxygenation conditions (5%, 10%, 20%, and 40% O2) for 14 days in the bioreactor. We analyzed the expression of the genes of hepatic metabolic pathways, such as glycolysis (glucokinase, phosphofructokinase, and pyruvate kinase), glycogen synthesis (glycogen synthetase, UTP glucose-1-phosphate uridylylisomerase, phosphoglucomutase, and glycogen phosphorylase), the urea cycle (arginase, ornithine carbomoyltransferase, fumarate hydratase), oxidative reabsorption (peroxidase), and cytochrome peroxides (catalase and superoxide dismutase), and compared it with the level in vivo. The metabolic mini-map was used to represent the above-mentioned metabolic genes. Increased urea secretion under normoxia and hyperoxia conditions (20% and 40% O2, respectively) was observed, while albumin secretion was decreased in hyperoxic cultures. Lactate formation was up to 15 mg/L-g/h-h/106 cells, 2 mg/L-g/h-h/106 cells, and 0.2 mg/L-c/h-h/106 cells in 5%, 20%, and 40% O2 conditions, respectively while glucose consumption was enhanced under hypoxic conditions (5% and 10% O2). Cellular membrane integrity was estimated by lactate dehydrogenase assay and was found to be negligible in only 20% and 40% O2 conditions. The expression of the phase II enzyme UDP-glucuronosyltransferase was only upregulated in 20% oxygenation. Taken together, 20% O2 was found to be an optimal condition for the long-term culture (up to 14 days) of hepatocytes that promoted the expression of genes in metabolic pathways such as glycolysis, glycogen synthesis, the urea cycle, and cytochrome peroxidase oxidative reabsorption, and improved hepatic functions in a miniature bioreactor for bioartificial liver construction.

Evaluation of hydromechanical and functional properties of diversion-type microcapsule-suspension bioreactor for bioartificial liver.

To evaluate the performance of a diversion-type microcapsulesuspension fluidized bed bioreactor and a choanoid fluidized bed bioreactor as bioartificial liver support systems. We evaluated the performance between the modified fluidized bed bioreactor based on diversion-type microcapsule suspension (DMFBB) and choanoid fluidized bed bioreactor (CFBB). The fluidization performance, fluidized height, bed expansion, and the mechanical stability and strength of microcapsule were determined. The viability, synthetic, metabolism, and apoptosis of microcapsulated HepLi5 cells were evaluated. Finally, samples were collected for measurement of alanine aminotransferase, total bilirubin, direct bilirubin, and albumin concentrations. Uniform fluidization was established in both DMFBB and CFBB. The bed expansion, shear force, retention rate, swelling rate, and breakage rate of microcapsules differed significantly between two bioreactors over 3 days. The viability of microencapsulated HepLi5 cells and the activities of cytochrome P450 1A2 and 3A4 increased on each day in DMFBB compared to the control. The albumin and urea concentrations in the DMFBB displayed obvious improvements compared to the control. Caspase3/7 activities in the DMFBB decreased compared to those in the CFBB. At 24 h, the alanine aminotransferase concentration in the DMFBB declined significantly compared to the control. The total and direct bilirubin concentrations within plasma perfusion were decreased and albumin was increased in the DMFBB at 24 h than in the CFBB. The DMFBB shows a promising alternative bioreactor for use in bioartificial liver support systems for application of clinical practice.

Porcine Hepatocytes: Isolation and Liver Tissue Engineering for Xenotransplantation.

Various liver diseases result in liver failure, and liver transplantation as a definite treatment is limited by the shortage of organs available for transplantation. The use of isolated primary hepatocytes in cell-based therapies including hepatocyte transplantation, tissue engineering liver transplantation, and bioartificial liver support systems has gained increasing interest during the past years. Human hepatocytes are the preferred source of cells. Aside from the organ shortage, the isolation of human liver cells is usually limited by obtaining a sufficient quantity of high-quality, metabolically active cells. Furthermore, livers from which hepatocytes are typically harvested are not suitable for transplantation, with the variability in quantity and quality. Porcine hepatocytes, on the other hand, have the ability to perform complex biological functions and show modifiable behavior. Primary porcine hepatocytes are currently widely used in the investigation of drug metabolism, hepatotoxicity, protein biosynthesis, and gene expression. Primary hepatocytes do not proliferate in vitro and are sensitive to freeze-thaw damage in cryopreservation and thus need to be freshly isolated for each experiment. Consequently, the methods of porcine hepatocyte isolation are being actively sought after. Our laboratories have been involved in various applications of liver cells, and we have long-lasting experiences in liver cell isolation and their application in R&D. We here summarize the present protocol of our laboratories for primary hepatocyte isolation from pig and their liver tissue engineering for xenotransplantation.

Bioartificial liver support systems for acute liver failure: A systematic review and meta-analysis of the clinical and preclinical literature.

BACKGROUNDAcute liver failure (ALF) has a high mortality varying from 80% to 85% with rapid progress in multi-organ system failure. Bioartificial liver (BAL) support systems have the potential to provide temporary support to bridge patients with ALF to liver transplantation or spontaneous recovery. In the past decades, several BAL support systems have been conducted in clinical trials. More recently, concerns have been raised on the renovation of high-quality cell sources and configuration of BAL support systems to provide more benefits to ALF models in preclinical experiments.AIMTo investigate the characteristics of studies about BAL support systems for ALF, and to evaluate their effects on mortality.METHODSEligible clinical trials and preclinical experiments on large animals were identified on Cochrane Library, PubMed, and EMbase up to March 6, 2019. Two reviewers independently extracted the necessary information, including key BAL indicators, survival and indicating outcomes, and adverse events during treatment. Descriptive analysis was used to identify the characteristics of the included studies, and a meta-analysis including only randomized controlled trial (RCT) studies was done to calculate the overall effect of BAL on mortality among humans and large animals, respectively.RESULTSOf the 30 selected studies, 18 were clinical trials and 12 were preclinical experiments. The meta-analysis result suggested that BAL might reduce mortality in ALF in large animals, probably due to the recent improvement of BAL, including the type, cell source, cell mass, and bioreactor, but seemed ineffective for humans [BAL vs control: relative risk (95% confidence interval), 0.27 (0.12-0.62) for animals and 0.72 (0.48-1.08) for humans]. Liver and renal functions, hematologic and coagulative parameters, encephalopathy index, and neurological indicators seemed to improve after BAL, with neither meaningful adverse events nor porcine endogenous retrovirus infection.CONCLUSIONBAL may reduce the mortality of ALF by bridging the gap between preclinical experiments and clinical trials. Clinical trials using improved BAL must be designed scientifically and conducted in the future to provide evidence for transformation.

Lecithin doped electrospun poly(lactic acid)-thermoplastic polyurethane fibers for hepatocyte viability improvement.

The development of hepatocyte cultures in vitro holds great significance in the study of bioartificial liver support systems. Electrospun fiber cultures have received widespread attention as an effective method to culture hepatocytes in vitro. Polylactic acid (PLA) -a synthetic polymer with high biocompatibility and biodegradability- is widely used to fabricate electrospun fibers in the biomedical field. However, the use of PLA is limited in cell cultures due to its brittleness, strong hydrophobicity, and lack of biologically active functional groups. In this study, thermoplastic polyurethane (TPU) and lecithin (Lec) were used to modify PLA by spiking them into the PLA electrospun solution in attempt to establish a suitable fiber scaffold for hepatocyte culture in bioreactors. TPU and lecithin incorporation into PLA increases the flexibility, hydrophilicity, and biologically active groups of the fibers which further promotes the growth, proliferation, and viability of hepatocytes. The morphology, wettability, and biocompatibility of the as-prepared PLA-TPU-Lec fibers were carefully characterized. The results showed that the PLA-TPU-Lec fibers possessed favorable morphology and hydrophilicity, as well as high biocompatibility ability. HepG2 cells on the PLA-TPU-Lec fibers and tissue culture plates (TCP) were exposed to hepatotoxins for 24 h and we found that HepG2 cells on the PLA-TPU-Lec fibers had higher viability than cells on TCP. The PLA-TPU-Lec fibers are therefore expected to be used in vitro for hepatocyte culture to improve cellular activity in artificial liver bioreactors.

Functionally coated polyethersulfone hollow fiber membranes: A substrate for enhanced HepG2/C3A functions.

Hollow fiber membrane (HFM) based liver assist systems are a life-saving bridge for patients until a donor organ is available for transplantation or until liver regeneration. However, liver cell attachment and functional maintenance on HFM surface is a major challenge in bio-artificial liver (BAL) support systems. In the present study, novel glutaraldehyde (GTA)-crosslinked gelatin (gel)-coated polyethersulfone (X-gel-PT) HFMs were manufactured using triple orifice spinneret by the dry-wet spinning method. HFMs were characterized for morphology, outer surface roughness, hydrophilicity, tensile strength, thermal stability, BET surface area and pore volume measurements, permeability and rejection. Fourier transform infrared spectroscopy, and transmission electron microscopy confirmed the GTA-crosslinked gel-coating in the X-gel-PT HFMs, which provided the desirable extracellular matrix-like environment to the HepG2/C3A cells. The results of in-vitro hemocompatibility tests showed the better suitability of the developed HFMs for the blood-contact application. X-gel-PT HFMs showed significantly better cellular attachment and proliferation of HepG2/C3A cells on day 3 and 6, as shown by scanning electron and confocal microscopy. Significantly high urea synthesis and albumin secretion seen indicated the improved functional and metabolic activity of HepG2/C3A cells. Thus, the developed X-gel-PT HFMs is a suitable substrate for the hepatocyte culture, mass culture, and development of BAL support system.

Hepatic congestion is the main pathological sign in concanavalin A-induced acute hepatitis in Bama mini-swine

Objective: The plant lectin concanavalin A (ConA) induced acute hepatitis in mice is a commonly used animal model applied in acute immune-mediated hepatitis studies, but it is not suitable for large animal model of hepatic injury to promote the study of bio-artificial liver support systems in humans and help to assist pre-clinical evaluation. During producing Bama mini-swine model of hepatic injury, we find Hepatic congestion is dispensable for this model. Methods: Seven Obama mini-swines in the model group were exposed to ConA by intravenous injection (5 mg/kg) into the vein of auricular back. The other 3 miniswines in the control group was administered with equal volume of saline. Blood was collected from precaval vein at 0 h, 6 h and 24 h after injection. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), serum creatinine (SCr) were determined. Portal vein pressure was measured. Animals surviving 24 h were euthanased. Afterwards, Liver tissues were collected and liver/weight index was calculated. The histological analyses of liver, kidney and spleen were performed. Results: Our data show that hepatic congestion is the main pathological sign in concanavalin A-induced acute hepatitis model in mini-swine resulting in hepatitis congestion, intestinal bleeding, marked renal tubular necrosis and spleen. Conclusion: Hepatic congestion is the main pathological sign in concanavalin A-induced acute hepatitis in Bama mini-swine.

Decellularized Liver Matrix-Modified Cryogel Scaffolds as Potential Hepatocyte Carriers in Bioartificial Liver Support Systems and Implantable Liver Constructs.

Recent progress in the use of decellularized organ scaffolds as regenerative matrices for tissue engineering holds great promise in addressing the issue of donor organ shortage. Decellularization preserves the mechanical integrity, composition, and microvasculature critical for zonation of hepatocytes in the liver. Earlier studies have reported the possibility of repopulating decellularized matrices with hepatic cell lines or stem cells to improve liver regeneration. In this work, we study the versatility of the decellularized liver matrix as a substrate coating of three-dimensional cryogel scaffolds. The coated cryogels were analyzed for their ability to maintain hepatic cell growth and functionality in vitro, which was found to be significantly better than the uncoated cryogel scaffolds. The decellularized liver matrix-coated cryogel scaffolds were evaluated for their potential application as a cell-loaded bioreactor for bioartificial liver support and as an implantable liver construct. Extracorporeal connection of the coated cryogel bioreactor to a liver failure model showed improvement in liver function parameters. Additionally, offline clinical evaluation of the bioreactor using patient-derived liver failure plasma showed its efficacy in improving liver failure conditions by approximately 30-60%. Furthermore, implantation of the decellularized matrix-coated cryogel showed complete integration with the native tissue as confirmed by hematoxylin and eosin staining of tissue sections. HepG2 cells and primary human hepatocytes seeded in the coated cryogel scaffolds implanted in the liver failure model maintained functionality in terms of albumin synthesis and cytochrome P450 activity post 2 weeks of implantation. In addition, a 20-60% improvement in liver function parameters was observed post implantation. These results, put together, suggest a possibility of using the decellularized matrix-coated cryogel scaffolds for liver tissue engineering applications.

Optimized performance of the integrated hepatic cell-loaded cryogel-based bioreactor with intermittent perfusion of acute liver failure plasma.

Acute liver failure (ALF) plasma has cytotoxic effects on the cell-loaded bioreactor in bioartificial liver support systems due to the presence of innumerable hepatotoxic compounds that adversely affect the morphology and functionality of the cells. We have designed a hybrid bioreactor that integrates a hepatic cell-loaded cryogel disc and an activated carbon cloth in one compact unit, with potential application as a bioartificial liver support. In this article, we assess the performance of this integrated hybrid cryogel-based bioreactor in a perfusion-based culture system and analyze its functionality and longevity in the presence of intermittent exposure to ALF plasma. The bioreactor maintained functionality in terms of glucose consumption and albumin synthesis for up to 40 days under perfusion. Additionally, intermittent perfusion of plasma from rodent models of ALF resulted in a decrease in viability and functionality only after the second spike of plasma, with the bioreactor maintaining its functionality even after the first spike. Similar results were obtained with patient plasma indicating the potential to reuse the bioreactor for multiple sessions of liver dialysis. Collectively, these results suggest the potential of the integrated cryogel-based bioreactor to be used at most twice before being disposed of. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 259-269, 2018.

Hydrodynamics characterization of a choanoid fluidized bed bioreactor used in the bioartificial liver system: Fully resolved simulation with a fictitious domain method

Choanoid fluidized bed bioreactors (CFBBs) are newly developed core devices used in bioartificial liver-support systems to detoxify blood plasma of patients with microencapsulated liver cells. Direct numerical simulations (DNS) with a direct-forcing/fictitious domain (DF/FD) method were conducted to study the hydrodynamic performance of a CFBB. The effects of particle–fluid density ratio, particle number, and filter screens preventing particles flowing out of the reactor were investigated. Depending on density ratio, two flow patterns are evident: the circulation mode in which the suspension rises along one sidewall and descends along the other sidewall, and the non-circulation mode in which the whole suspension roughly flows upward. The circulation mode takes place under non-neutral-buoyancy where the particle sedimentation dominates, whereas the non-circulation mode occurs under pure or near-neutral buoyancy with particle–fluid density ratios of unity or near unity. With particle–fluid density ratio of 1.01, the bioartificial liver reactor performs optimally as the significant particle accumulation existing in the non-circulation mode and the large shear forces on particles in the circulation mode are avoided. At higher particle volume fractions, more particles accumulate at the filter screens and a secondary counter circulation to the primary flow is observed at the top of the bed. Modelled as porous media, the filter screens play a negative role on particle fluidization velocities; without screens, particles are fluidized faster because of the higher fluid velocities in the jet center region. This work extends the DF/FD-based DNS to a fluidized bed and accounts for effects from inclined side walls and porous media, providing some hydrodynamics insight that is important for CFBB design and operation optimization.

Clinical translation of bioartificial liver support systems with human pluripotent stem cell-derived hepatic cells.

There is currently a pressing need for alternative therapies to liver transplantation. The number of patients waiting for a liver transplant is substantially higher than the number of transplantable donor livers, resulting in a long waiting time and a high waiting list mortality. An extracorporeal liver support system is one possible approach to overcome this problem. However, the ideal cell source for developing bioartificial liver (BAL) support systems has yet to be determined. Recent advancements in stem cell technology allow researchers to generate highly functional hepatocyte-like cells from human pluripotent stem cells (hPSCs). In this mini-review, we summarize previous clinical trials with different BAL systems, and discuss advantages of and potential obstacles to utilizing hPSC-derived hepatic cells in clinical-scale BAL systems.

Isolations and Cultures of Primary Hepatocytes

Various liver diseases result in liver failure, and liver transplantation and artificial liver support systems are emerging as alternative therapies for these disease. However, both treatments are depending on cell resources, so isolating sufficient number of functional primary hepatocytes is a most important early issue. Isolated hepatocytes are also a suitable system for the physiological, pharmacological and toxicological study of hepatic uptake, metabolism, excretion and toxicity. In this paper, the methods for hepatocyte isolation are reviewed; the culture and assessment methods are also examined. Hepatocyte transplantation and hepatocyte-based bioartificial liver support systems have attracted the attention of researchers. From a future perspective, developing of gene engineering is emerging as a promising way to modify cells, and this is renewing interest in the development of methods for isolation and culture of hepatocytes.

P11: Targeted modulation of hepatocellular stress pathways during biopreservation affects storage outcome

Primary hepatocytes are central to a number of in vitro applications including hepatotoxicity testing for drug development, potential uses in cell therapy, and as research tools for improving organ transplantation. Further, hepatocyte derivatives such as the human hepatoma cell line C3A serve important roles in other technologies such as bioartificial liver support systems. While it is well characterized that molecular stress pathways are activated in response to biopreservation associated stresses thereby resulting in cell death and system failure, it remains unclear whether the specific molecular pathways activated are universal or cell specific. We hypothesized that given the vastly different characteristics of hepatocyte cell systems, cell type specific stress pathways may be activated under different storage regimes. To this end, we compared the responses of two hepatic cell types following both hypothermic and hypoxic normothermic storage and examined storage related stress signaling. Normal hepatocytes (NHEP) and C3A were stored under either hypothermic (4 °C) conditions for 18hrs to 3d or hypoxic normothermic (37 °C) conditions for 1–14 d. Respective growth media, HBSS (Balanced Salt Solution), and ViaSpan (UW solution) were utilized as storage media with and without the addition of salubrinal or resveratrol to examine targeted molecular pathway modulation. Viability was assessed at 0, 24 and 48 h post-storage. Apoptotic and necrotic populations were assessed via flow cytometry and fluorescent microscopy post-storage. Protein immunoblotting was performed to evaluate alterations in ER stress pathway proteins and apoptotic signaling proteins. Viability studies demonstrated a significant difference in modulation study outcomes for the two cell types. This was noted as salubrinal addition to HBSS stored C3A yielded significant improvement in viability (∼60%) while having no significant impact on NHEPs. Conversely, resveratrol addition to HBSS resulted in a significant decrease in C3A viability (∼80%) whereas it conferred a marked improvement on NHEP survival (∼25%). Interestingly, when the modulators were utilized under a hypoxic normothermic regime a differential response was observed as salubrinal negatively impacted C3A viability (∼50% decrease) while yielding improvement to NHEP survival (∼30% increase) and resveratrol yielded decreased viability in both cell types. Investigations into cell death populations demonstrated marked changes in the number of cells undergoing apoptosis and necrosis that was influenced by the use of these molecular modulators. Further, immunoblot analyses revealed alterations to protein levels associated with apoptotic activation (pro-caspase cleavage) as well as implications of ER stress induced cell death signaling (calnexin cleavage). These data demonstrate a differential response in hepatic cell systems that is dependent upon storage temperature, basal media and modulator addition. This is important for the processing and storage of biologics as it demonstrates that universal protocols may not be effective for all cell types and conditions and a more specific and directed approach may be necessary for optimal efficacy.

HEPATIC TISSUE ENGINEERING (MODERN STATE OF THIS PROBLEM)

In this article it was discussed the problem of creation implanted hepatic tissue engineering designs as a modern stage of complex investigation for working out bioartifi cial liver support systems. It was determined that for the positive decision of numerous biological and technological problems it is necessary: to use matrices with determined properties, which mimic properties of hepatic extracellular matrix; to use technology for stereotype sowing of these matrices by both parenchymal and non-parenchymal hepatic cells and to improve the technologies for making and assembling of hepatic tissue-engineering designs.

Liver support strategies: cutting-edge technologies

The treatment of end-stage liver disease and acute liver failure remains a clinically relevant issue. Although orthotopic liver transplantation is a well-established procedure, whole-organ transplantation is invasive and increasingly limited by the unavailability of suitable donor organs. Artificial and bioartificial liver support systems have been developed to provide an alternative to whole organ transplantation, but despite three decades of scientific efforts, the results are still not convincing with respect to clinical outcome. In this Review, conceptual limitations of clinically available liver support therapy systems are discussed. Furthermore, alternative concepts, such as hepatocyte transplantation, and cutting-edge developments in the field of liver support strategies, including the repopulation of decellularized organs and the biofabrication of entirely new organs by printing techniques or induced organogenesis are analysed with respect to clinical relevance. Whereas hepatocyte transplantation shows promising clinical results, at least for the temporary treatment of inborn metabolic diseases, so far data regarding implantation of engineered hepatic tissue have only emerged from preclinical experiments. However, the evolving techniques presented here raise hope for bioengineered liver support therapies in the future.

Integration of single-layer skin hollow fibers and scaffolds develops a three-dimensional hybrid bioreactor for bioartificial livers

Bioartificial liver support systems are expected to be an effective therapy as a "bridge" for liver transplantation or reversible acute liver disease. A major roadblock in the application of bioartificial livers is the need for a bioreactor that fully meets the requirements of hepatocyte culture, mass transfer and immunobarriers. In this study, we developed a three-dimensional hybrid bioreactor (3DHB) on a base of single-layer skin polyethersulfone hollow fibers by integrating with polyurethane scaffolds. The mass transfer of bilirubin and albumin from the intracapillary space to the extracapillary space of the hollow fibers was not significantly different between 3DHBs and hollow fiber bioreactors (HFBs). Cell viability staining showed that high-density hepatocytes were uniformly found in different regions of the 3DHB after 7 days of culture. Liver-specific functions of human mature hepatocytes cultured in the 3DHB, such as albumin secretion, urea production, ammonia removal rate and cytochrome P450 activity, were maintained stably and were significantly higher compared with the HFB. These results indicated that the 3DHB has good mass transfer and improves cell distribution and liver-specific functions. Meanwhile, the ammonia and unconjugated bilirubin concentrations in plasma from patients with liver failure were significantly decreased during 6 h of circulation by hepatocytes cultured in the 3DHB. Most hepatocytes in the 3DHB were viable after 6 h exposure to the patient plasma. We further demonstrated that bioartificial liver systems with 3DHB can remove toxins from and endure the deleterious effects of the patient plasma. Therefore, the 3DHB has the potential to accomplish different actions for the clinical application of bioartificial livers.

Artificial and bioartificial liver support systems for acute and acute-on-chronic hepatic failure: A meta-analysis and meta-regression

Artificial and bioartificial liver support systems (LSSs) appear to be safe and effective in the treatment of acute and acute-on-chronic hepatic failure (AHF and AOCHF); however, individually published studies and previous meta-analyses have revealed inconclusive results. The aim of the present meta-analysis was to derive a more precise estimation of the benefits and disadvantages of artificial and bioartificial LSSs for patients with AHF and AOCHF. A literature search was conducted in the PubMed, Embase, Web of Science and Chinese Biomedical (CBM) databases for publications prior to March 1, 2013. Crude relative risks (RRs) or standardized mean differences (SMDs) with 95% confidence intervals (95% CI) were calculated using either the fixed effects or random effects models. Nineteen randomized controlled trials (RCTs) were included, which comprised a total of 566 patients with AHF and 371 patients with AOCHF. The meta-analysis showed that artificial LSS therapy significantly reduced mortality in patients with AOCHF; however, it had no apparent effect on total mortality in patients with AHF. The results also indicated that the use of bioartificial LSSs was correlated with decreased mortality in patients with AHF. A significant reduction in the bridging to liver transplantation was observed in patients with AOCHF following artificial LSS therapy; however, similar results were not observed in patients with AHF. Patients with AHF and those with AOCHF showed significant reductions in total bilirubin levels following artificial LSS therapy. There were no significantly increased risks of hepatic encephalopathy or bleeding in either the patients with AHF or AOCHF following artificial or bioartificial LSS therapies. Univariate and multivariate meta-regression analyses confirmed that none of the factors explained the heterogeneity. The present meta-analysis indicated that artificial LSSs reduce mortality in patients with AOCHF, while the use of bioartificial LSSs was correlated with reduced mortality in patients with AHF.

Progress in technology and clinical application of non-bioartificial liver support system

Several types of non- bioartificial liver support systems are now widely used in the treatment of severe hepatitis and liver failure,which are life- threatening diseases,but no consensus has been reached regarding its efficacy. The designs and results of high- level studies for evaluating the therapeutic effects of 6 common types of non- bioartificial liver are reviewed; considering the pathophysiological characteristics of liver failure and the mechanism of artificial liver,analysis and horizontal comparison are performed on the effectiveness of non- bioartificial liver,and the advantages and disadvantages of artificial liver and its indications are pointed out. In addition,the safety and strategy of clinical application of non- bioartificial liver,as well as the future demand and development in technical and clinical research in this field,are summarized.