Liver support technology--an update

Therapeutic Effects of Plasmapheresis on Acute Exacerbations of Chronic Hepatitis B Infection

Objective

In this study, we aimed to demonstrate the effectiveness of plasmapheresis therapy in patients with acute exacerbation of chronic Hepatitis B (CHB) infection.

Methods

We selected 48 patients with acute exacerbation of CHB infection who were treated by plasmapheresis in our intensive care unit between 2009 and 2016. The patients' demographic characteristics and biochemical and hematological parameters, which were recorded before and after plasmapheresis, were assessed, and the effect of plasmapheresis on the course of patients' treatment was examined. The patients were also divided into three groups according to their clinical course (discharged: 24; transplanted: six; exitus: eight). The patients were further divided into four groups and compared based on the underlying causes that led to the exacerbation (spontaneous exacerbation: 25; caused by immunosuppressive drugs: nine; hepatotoxic drugs: six; other agents: eight).

Results

We observed significant improvements in terms of international normalized ratio (INR), aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), total bilirubin, direct bilirubin, blood urea nitrogen (BUN), ammonia, and the Model for End-Stage Liver Disease (MELD) score after plasmapheresis therapy. However, there was no significant improvement in hemoglobin (Hb), white blood cell (WBC) count, platelets, albumin, and lactate values. Also, INR, ALP, and ALT values were found to be significantly correlated with transplants and exitus in patients.

Conclusion

Plasmapheresis therapy is a reliable treatment method that provides clinical recovery and improvement in laboratory parameters in patients with exacerbation of CHB infection.

Targeting Albumin Binding Function as a Therapy Goal in Liver Failure: Development of a Novel Adsorbent for Albumin Dialysis

Liver failure results in impaired hepatic detoxification combined with diminished albumin synthesis and is associated with secondary organ failure. The accumulation of liver toxins has shown to saturate albumin binding sites. This was previously demonstrated by an in vitro test for albumin binding capacity (ABiC) that has shown to inversely correlate with the established MELD (Model for End-Stage Liver Disease) score. In this study, we introduced a new adsorbent material for albumin dialysis treatments that improves albumin binding capacity. The new charcoal adsorbent was developed by an evolutionary test schedule. Batch testing of charcoals was performed as steady-state experiments. The charcoal reflecting the highest increase in albumin binding capacity was then introduced to kinetic models: Perfusion tests were designed to evaluate adsorption capacity and kinetics for liver failure marker toxins. A dynamic recirculation model for liver failure was used for upscaling and comparison against conventional MARS adsorbents as the gold standard in an albumin dialysis setting. Batch tests revealed that powdered activated Hepalbin charcoal displayed the highest ABiC score. Hepalbin charcoal also demonstrated higher adsorptive capacity and kinetics for liver failure marker toxins as determined by perfusion tests. These findings translated to tests of upscaled adsorbents in a dynamic model for liver failure: upscaled Hepalbin adsorbent removes bile acids, direct bilirubin and indirect bilirubin significantly better than MARS adsorbents and significantly increases ABiC. The novel adsorbent Hepalbin offers a significant improvement over both MARS adsorbents concerning liver failure marker toxin removal and ABiC improvement.

Generation of carbamoyl phosphate synthetase 1 reporter cell lines for the assessment of ammonia metabolism

Both primary hepatocytes and stem cells-derived hepatocyte-like cells (HLCs) are major sources for bioartificial liver (BAL). Maintenance of hepatocellular functions and induction of functional maturity of HLCs are critical for BAL's support effect. It remains difficult to assess and improve detoxification functions inherent to hepatocytes, including ammonia clearance. Here, we aim to assess ammonia metabolism and identify ammonia detoxification enhancer by developing an imaging strategy. In hepatoma cell line HepG2, and immortalized hepatic cell line LO2, carbamoyl phosphate synthetase 1 (CPS1) gene, the first enzyme of ammonia-eliminating urea cycle, was labelled with fluorescence protein via CRISPR/Cas9 system. With the reporter-based screening approach, cellular detoxification enhancers were selected among a collection of 182 small molecules. In both CPS1 reporter cell lines, the fluorescence intensity is positively correlated with cellular CPS1 mRNA expression, ammonia elimination and secreted urea, and reflected ammonia detoxification in a dose-dependent manner. Surprisingly, high-level CPS1 reporter clones also reserved many other critical hepatocellular functions, for example albumin secretion and cytochrome 450 metabolic functions. Sodium phenylbutyrate and resveratrol were identified to enhance metabolism-related gene expression and liver-enriched transcription factors C/EBPα, HNF4α. In conclusion, the CPS1-reporter system provides an economic and effective platform for assessment of cellular metabolic function and high-throughput identification of chemical compounds that improve detoxification activities in hepatic lineage cells.

Hepatocyte transplantation in children with liver cell failure

Patients with hepatic failure and liver-based metabolic disorders require management which is both costly and complex. Hepatocyte transplantation has been very encouraging as an alternative to organ transplantation for liver disease treatment, and studies in rodents, show that transplants involving isolated liver cells can reverse hepatic failure, and correct various metabolic deficiencies of the liver. This 2016 review is based on a literature search using PubMed including original articles, reviews, cases and clinical guidelines. The search terms were “hepatocyte transplantation”, “liver transplantation”, “liver cell failure”, “metabolic liver disorders”, “orthotropic liver transplantation”, “hepatocytes” and “stem cell transplantation”. The goal of this review is to summarize the significance of hepatocyte transplantation, the sources of hepatocytes and the barriers of hepatocyte transplantation using a detailed review of literature. Our review shows that treatment of patients with liver disease by hepatocyte transplantation has expanded exponentially, especially for patients suffering from liver-based metabolic disorders. Once hepatocyte transplantation has been shown to effectively replace organ transplantation for a portion of patients with life-threatening liver metabolic diseases and those with liver failure it will make cell therapy effective and available for a broad population of patients with liver disorders.

Extracorporeal liver support devices for listed patients

An alternative to liver transplantation for patients with liver failure remains an unmet need. In acute liver failure, the ideal extracorporeal liver support device (ELSD) would replace the functions of the failing liver in order to permit spontaneous recovery, given the incredible regenerative potential of the liver, negating the need for transplantation. In acute-on-chronic liver failure, an ELSD would ideally support hepatic function until a recovery to liver function before acute decompensation or until liver transplantation. In decompensated cirrhosis, an ELSD could again be used to support hepatic function until transplant. In addition, ELSDs may have the potential to treat the multiorgan failure that accompanies liver failure including hepatic encephalopathy, renal failure, and immune dysfunction or indeed potential to promote liver regeneration. Creation of an extracorporeal bioartificial liver able to completely replace liver function remains an unmet need. This review will describe a number of technologies suitable for clinical trials in humans, which have resulted from decades of engineering and biological research to develop a bioreactor able to adequately sustain functional hepatocytes. In addition, this review will describe artificial liver support devices that are primarily designed to replace the detoxifying functions of the liver and will consider the current data available or studies required to support their use in liver failure patients on the transplant waiting list. Liver Transplantation 22 839-848 2016 AASLD.

Advanced therapeutic strategies for HBV-related acute-on-chronic liver failure

BACKGROUND

Acute-on-chronic liver failure (ACLF) is increasingly recognized as a distinct clinical entity and is associated with a high short-term mortality. The most common cause of ACLF is chronic hepatitis B worldwide. Currently, there is no standardized approach for the management of ACLF and the efficacy and safety of therapeutic modalities are uncertain.

DATA SOURCES

PubMed and Web of Science were searched for English-language articles. The search criteria focused on clinical trials and observational studies on the treatment of patients with HBV-related ACLF.

RESULTS

Therapeutic approaches for ACLF in patients with chronic hepatitis B included nucleos(t)ide analogues, artificial liver support systems, immune regulatory therapy, stem cell therapy and liver transplantation. All of these therapeutic approaches have shown the potential to improve liver function and increase patients' survival rate, but most of the studies were not randomized or controlled.

CONCLUSION

Substantial challenges for the treatment of HBV-related ACLF remain and further basic research and randomized controlled clinical trials are needed.

Serum wnt5a is a predictor for the prognosis of acute on chronic hepatitis B liver failure

OBJECTIVES

To find a biomarker to predict the prognosis of acute on chronic hepatitis B liver failure (ACHBLF).

METHODS

Expression gene profiles in wnt pathway were determined in serum from 63 patients with ACHBLF, 60 patients with chronic hepatitis B (CHB) and 30 healthy controls (HCs).

RESULTS

Serum wnt5a concentration of 1.553 ng/ml showed a poor prognosis with a sensitivity of 69.23% and a specificity of 83.33% in ACHBLF patients.

CONCLUSIONS

Serum wnt5a gene expression might be a potential biomarker for predicting the prognosis of ACHBLF.

A non-adhesive hybrid scaffold from gelatin and gum Arabic as packed bed matrix for hepatocyte perfusion culture

Development of liver support systems has become one of the most investigated areas for the last 50 years because of the shortage of donor organs for orthotopic liver transplantations. Bioartificial liver (BAL) device is one of the alternatives for liver failure which provides a curing method and support patients to recover from certain liver failure diseases. The biological compartment of BAL is called the bioreactor where functionally active hepatocytes are maintained to support the liver specific functions. We have developed a packed bed bioreactor with a cytocompatible, polysaccharide-protein hybrid scaffold. The scaffold prepared from gelatin and gum Arabic acts as a packed bed matrix for hepatocyte culture. Quantitative evaluation of the hepatocytes cultured using packed bed bioreactor demonstrated that cells maintained liver specific functions like albumin and urea synthesis for seven days. These results indicated that the system can be scaled up to form the biological component of a bioartificial liver.

Artificial liver

Artificial liver generally is classified as either inert or cell-based, although only the latter is a true artificial liver. Despite some major achievements and investment, no device is currently available; devices have either not been tested rigorously, or have failed to meet expectations in clinical trials. A successful device will provide the appropriate level of liver function, but it also must be applied in the appropriate clinical setting. An extracorporeal device may be capable of supporting a failing liver, but it will not correct portal hypertension. The future of this field depends on both the technical aspects of the device(s) and their application to the appropriate clinical situation.

Liver dialysis in acute-on-chronic liver failure: current and future perspectives

Patients with acute-on-chronic liver failure (ACLF) are known to have a very high mortality rate as the majority of these patients succumb to multiorgan failure. Liver transplant remains the only option for these patients; however, there are problems with its availability, cost and also the complications and side effects associated with immunosuppression. Unlike advanced decompensated liver disease, there is a potential for hepatic regeneration and recovery in patients with ACLF. A liver support system, cell or non-cell based, logically is likely to provide temporary functional support until the donor liver becomes available or the failing liver survives the onslaught of the acute insult and spontaneously regenerates. Understanding the pathogenesis of liver failure and regeneration is essential to define the needs for a support system. Removal of hepatotoxic metabolites and inhibitors of hepatic regeneration by liver dialysis, a non-cell-based hepatic support, could help to provide a suitable microenvironment and support the failing liver. The current systems, i.e., MARS and Prometheus, have failed to show survival benefits in patients with ACLF based on which newer devices with improved functionality are currently under development. However, larger randomized trials are needed to prove whether these devices can enable restoration of the complex dysregulated immune system and impact organ failure and mortality in these patients.

Liver tissue engineering and cell sources: issues and challenges

Liver diseases are of major concern as they now account for millions of deaths annually. As a result of the increased incidence of liver disease, many patients die on the transplant waiting list, before a donor organ becomes available. To meet the huge demand for donor liver, alternative approaches using liver tissue engineering principles are being actively pursued. Even though adult hepatocytes, the primary cells of the liver are most preferred for tissue engineering of liver, their limited availability, isolation from diseased organs, lack of in vitro propagation and deterioration of function acts as a major drawback to their use. Various approaches have been taken to prevent the functional deterioration of hepatocytes including the provision of an adequate extracellular matrix and co-culture with non-parenchymal cells of liver. Great progress has also been made to differentiate human stem cells to hepatocytes and to use them for liver tissue engineering applications. This review provides an overview of recent challenges, issues and cell sources with regard to liver tissue engineering.

Blood-derived stem cells (BDSCs) plasticity: in vitro hepatic differentiation

The limited availability of hepatic tissue suitable for the treatment of liver disease and drug research encourages the generation of hepatic-like cells from alternative sources as support for the regenerative medicine. Human blood derived stem cells (BDSCs) express surface markers and genes characteristic of pluripotent stem cells and have the ability to differentiate into different cell types, including tissues of endodermal origin (i.e., liver). Therefore they can represent a valuable source of hepatocytes for medicine. In this investigation, we exploited a fast hepatic differentiation protocol to generate hepatocyte-like cells from human BDSCs using only hepatocyte growth factor (HGF) and fibroblast growth factor-4 (FGF-4) as growth factors. The resulting cell population exhibited hepatic cell-like morphology and it was characterized with a variety of biological endpoint analyses. Here, we demonstrate how human BDSCs can be reprogrammed in hepatocyte-like cells by morphological, functional analysis, reverse transcriptase (RT)-PCR, and Western Blot assay. This study defines a fast and easy reprogramming strategy that facilitates the differentiation of human BDSCs along a hepatic lineage and provides a framework for a helpful source in the stem cells therapy and liver disorders.

External inosculation as a feature of revascularization occurs after free transplantation of murine liver grafts

The induction of angiogenesis is essential for successful engraftment of freely transplanted cells or cellular composites. How to augment angiogenesis to ensure an appropriate viability of the grafts is still under investigation. This study evaluated the proangiogenic capability of different syngeneic free liver transplants and elucidated the origin of the newly formed vascular network via use of an eGFP(+) /eGFP(-) (enhanced green fluorescent protein) cross-over design. Using intravital fluorescence microscopy, we found that neonatal and resected murine liver transplants implanted into dorsal skinfold chambers display a significantly enhanced vascularization compared to regular adult transplants. Immunohistochemically, less tissue hypoxia, apoptosis and macrophage infiltration was observed in the neonatal and resected transplants, which is in line with improved vascularization of those grafts. Additionally, electron microscopy revealed morphological hallmarks of liver cells. eGFP(+) liver transplants implanted on eGFP(-) recipients displayed vascular sprouting from the grafts themselves and connection to the recipients` microvasculature, which also undergoes transient proangiogenic response. This process is described as external inosculation, with microvessels exhibiting a chimeric nature of the endothelial lining. These data collectively show that proliferative stimulation is taking effect on angiogenic properties of free transplants and might provide a novel tool for modulating the revascularization of free grafts.

Artificial liver support system reduces intracranial pressure more effectively than bioartificial system: an experimental study

OBJECTIVES

Extracorporeal liver support (ELS) may play a role in bridging therapy in patients with acute liver failure (ALF). The aim of this study was to compare the influence of nonbiological and biological methods on intracranial pressure (ICP) in an animal model of ALF.

METHODS

A surgical devascularization model of ALF in pigs (35-40 kg) was used. Elimination therapy started after the onset of hypoglycemia. Biochemical parameters (bilirubin, ammonia, lactate, etc.) as well as ICP and cerebral perfusion pressure (CPP) were monitored for 12 hours. Of the total 31 pigs with ALF, 14 animals were treated by fractionated plasma separation and absorption (FPSA), 10 were treated with a bioartificial liver (BAL), and 7 animals were used as a control group.

RESULTS

FPSA and BAL treatment started on average 3 hours 17 minutes and 2 hours 21 minutes, after devascularization and lasted for 5 hours 54 minutes and 5 hours 43 minutes, respectively. Ammonia levels were lower in the FPSA group, and bilirubin levels differed significantly in both the FPSA and BAL groups compared with controls. However, ICP values were reduced more effectively in pigs treated by FPSA: 19.1 vs. 27.0 mm Hg at 9 hours, 22.5 vs. 28.7 mm Hg at 11 hours, and 24.0 vs. 33.0 mm Hg at 12 hours (p<0.05).

CONCLUSIONS

The artificial liver support system FPSA reduced ICP values more effectively than the Performer O. Liver RanD BAL system. Compared with this BAL system, the nonbiological elimination method of FPSA is a simpler application with the advantage that it can be applied in a more continuous way.

Key challenges to the development of extracorporeal bioartificial liver support systems

BACKGROUND

For nearly three decades, extracorporeal bioartificial liver (BAL) support systems have been anticipated as promising tools for the treatment of liver failure. However, these systems are still far from clinical application. This review aimed to analyze the key challenges to the development of BALs.

DATA SOURCE

We carried out a PubMed search of English-language articles relevant to extracorporeal BAL support systems and liver failure.

RESULTS

Extracorporeal BALs face a series of challenges. First, an appropriate cell source for BAL is not readily available. Second, existing bioreactors do not provide in vivo-like oxygenation and bile secretion. Third, emergency needs cannot be met by current BALs. Finally, the effectiveness of BALs, either in animals or in patients, has been difficult to document.

CONCLUSIONS

Extracorporeal BAL support systems are mainly challenged by incompetent cell sources and flawed bioreactors. To advance this technology, future research is needed to provide more insights into interpreting the conditions for hepatocyte differentiation and liver microstructure formation.

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.

Effects of fractionated plasma separation and adsorption on survival in patients with acute-on-chronic liver failure

BACKGROUND & AIMS

Fractionated plasma separation and adsorption (FPSA) is an extracorporeal procedure that supports liver function by removing endogenous toxins that cause complications from acute-on-chronic liver failure (AOCLF). We performed a randomized trial to investigate survival of patients with AOCLF treated with FPSA.

METHODS

Patients with AOCLF were randomly assigned to groups given a combination of FPSA and standard medical therapy (SMT) (FPSA group, n = 77) or only SMT (SMT group, n = 68). The Prometheus liver support system was used to provide 8 to 11 rounds of FPSA (minimum of 4 hours each) for 3 weeks. Primary end points were survival probabilities at days 28 and 90, irrespective of liver transplantation.

RESULTS

Baseline clinical parameters and number of transplant patients were similar between study arms. Serum bilirubin level decreased significantly in the FPSA group but not in the SMT group. In an intention-to-treat analysis, the probabilities of survival on day 28 were 66% in the FPSA group and 63% in the SMT group (P = .70); on day 90, they were 47% and 38%, respectively (P = .35). Baseline factors independently associated with poor prognosis were high SOFA score, bleeding, female sex, spontaneous bacterial peritonitis, intermediate increases in serum creatinine concentration, and combination of alcoholic and viral etiology of liver disease. There were no differences between the 2 groups in the incidence of side effects.

CONCLUSIONS

Among all patients with AOCLF, extracorporeal liver support with FPSA does not increase the probability of survival. Further studies are needed to assess whether therapy might be beneficial in specific subsets of patients.

Hepatogenic differentiation of mesenchymal stem cells induced by insulin like growth factor-I

AIM

To improve hepatic differentiation of human mesenchymal stem cell (MSC) using insulin growth factor 1 (IGF-I), which has important role in liver development, hepatocyte differentiation and function.

METHODS

Bone marrow of healthy donors was aspirated from the iliac crest. The adherent cells expanded rapidly and were maintained with periodic passages until a relatively homogeneous population was established. The identification of these cells was carried out by immunophenotype analysis and differentiation potential into osteocytes and adipocytes. To effectively induce hepatic differentiation, we designed a protocol based on a combination of IGF-I and liver specific factors (hepatocyte growth factor, oncostatin M and dexamethasone). Morphological features, hepatic functions and cytological staining were assessed to evaluate transdifferentiation of human marrow-derived MSCs.

RESULTS

Flow cytometric analysis and the differentiation potential into osteoblasts and adipocytes showed that more than 90% of human MSCs which were isolated and expanded were positive by specific markers and functional tests. Morphological assessment and evaluation of glycogen storage, albumin and α-feto protein expression, as well as albumin and urea secretion revealed a statistically significant difference between the experimental groups and control.

CONCLUSION

In vitro differentiated MSCs using IGF-I were able to display advanced liver metabolic functions, supporting the possibility of developing them as potential alternatives to primary hepatocytes.

Acute-on-chronic liver failure: extracorporeal liver assist devices

PURPOSE OF REVIEW

Acute-on-chronic liver failure (ACLF), a syndrome precipitated by acute liver injury in patients with advanced cirrhosis, is associated with multiorgan dysfunction and high rates of mortality. Liver support systems have been developed in an attempt to improve survival of patients with ACLF by providing a bridge until recovery of the native liver function.

RECENT FINDINGS

Nonbiological devices such as molecular adsorbent recirculating system (MARS) and fractionated plasma separation and adsorption (Prometheus) are effective in improving severe hepatic encephalopathy and cholestasis, have good safety and tolerability profiles and are frequently employed in patients with ACLD; however, randomized controlled trials (RCTs) failed to show improvement in survival. Biologic devices that incorporate hepatic cells in bioreactors are also under development. Recent data from pilot studies suggested improvement in survival rates in some groups of patients with ACLF; however, their effect on patient survival in RCT is still unknown.

SUMMARY

Liver support systems are safe and well tolerated when used in management of patients with ACLF. Their use should continue in controlled clinical trials to explore their role in bridging patients to liver transplantation or recovery in well defined patient groups.

Hepatic differentiation of mesenchymal stem cells: in vitro strategies

Recently, evidence has been provided that mesenchymal stem/progenitor cells (MSC) from various sources (bone marrow, adipose tissue, skin, placenta, umbilical cord) could occasionally overcome lineage borders and differentiate into endodermal (hepatocytes) and ectodermal (neural cells) cell types in vitro. Whereas unidirectional differentiation into other mesenchymal cell types, including adipocytes, chondrocytes, and osteoblasts, readily occurs in the presence of a simple cocktail of growth factors and nutrients, successful bypassing of lineage borders mainly depends on multistep processes in a coordinated signaling network. Here, we provide a reproducible basic methodology to differentiate adult MSC into functional hepatocytes in a sequential and time-dependent way. In addition, focus lies on the functional characterization of MSC-derived hepatocyte-like cells. In particular, we provide a detailed modus operandi to measure the inducible cytochrome P450 (CYP)-dependent activity of MSC-derived hepatocyte-like cells.

Barriers to the successful treatment of liver disease by hepatocyte transplantation

Management of patients with hepatic failure and liver-based metabolic disorders is complex and expensive. Hepatic failure results in impaired coagulation, altered consciousness and cerebral function, a heightened risk of multiple organ system failure, and sepsis [1]. Such manifold problems are only treatable today and for the foreseeable future by transplantation. In fact, whole or auxiliary partial liver transplantation is often the only available treatment option for severe, even if transient, hepatic failure. Patients with life-threatening liver-based metabolic disorders similarly require organ transplantation even though their metabolic diseases are typically the result of a single enzyme deficiency, and the liver otherwise functions normally. For all of the benefits it may confer, liver transplantation is not an ideal therapy, even for severe hepatic failure. More than 17,000 patients currently await liver transplantation in the United States, a number that seriously underestimates the number of patients that need treatment [2], as it has been estimated that more than a million patients could benefit from transplantation [3]. Unfortunately, use of whole liver transplantation to treat these disorders is limited by a severe shortage of donors and by the risks to the recipient associated with major surgery [4].

A combining method to enhance the in vitro differentiation of hepatic precursor cells

The ideal bioartificial liver should be designed to reproduce as nearly as possible in vitro the habitat that hepatic cells find in vivo. In the present work, we investigated the in vitro perfusion condition with a view to improving the hepatic differentiation of pluripotent human liver stem cells (HLSCs) from adult liver. Tissue engineering strategies based on the cocultivation of HLSCs with hepatic stellate cells (ITO) and with several combinations of medium were applied to improve viability and differentiation. A mathematical model estimated the best flow rate for perfused cultures lasting up to 7 days. Morphological and functional assays were performed. Morphological analyses confirmed that a flow of perfusion medium (assured by the bioreactor system) enabled the in vitro organization of the cells into liver clusters even in the deeper levels of the sponge. Our results showed that, when cocultured with ITO using stem cell medium, HLSCs synthesized a large amount of albumin and the MTT test confirmed an improvement in cell proliferation. In conclusion, this study shows that our in vitro cell conditions promote the formation of clusters of HLSCs and enhance the functional differentiation into a mature hepatic population.

New Strategies for Acute Liver Failure: Focus on Xenotransplantation Therapy

Acute liver failure (ALF) has a poor prognosis and, despite intensive care support, reported average survival is only 10-40%. The most common causes responsible for ALF are viral hepatitis (mainly hepatitis A and B) and acetaminophen poisoning. Hepatic transplantation is the only appropriate treatment for patients with unlikely survival with supportive care alone. Survival rates after transplantation can be as high as 80-90% at the end of the first year. However, there is a shortage of donors and is not uncommon that no appropriate donor matches with the patient in time to avoid death. Therefore, new technologies are in constant development, including blood purification therapies as plasmapheresis, hemodiafiltration, and bioartificial liver support. However, they are still of limited efficacy or at an experimental level, and new strategies are welcome. Accordingly, cell transplantation has been developed to serve as a possible bridge to spontaneous recovery or liver transplantation. Xenotransplant of adult hepatocytes offers an interesting alternative. Moreover, the development of transgenic pigs with less immunogenic cells associated with new immunosuppressor strategies has allowed the development of this area. This article reviews some of the newly developed techniques, with focus on xenotransplant of adult hepatocytes, which might have clinical benefits as future treatment for ALF.

Adsorbents with high selectivity for uremic middle molecular peptides containing the Asp-Phe-Leu-Ala-Glu sequence

Asp-Phe-Leu-Ala-Glu (DE5) is a frequent sequence of many toxic middle molecular peptides that accumulate in uremic patients. To eliminate these peptides by hemoperfusion, three adsorbents (CP1-Zn(2+), CP2-Zn(2+), and CP3-Zn(2+)) were designed on the basis of coordination and hydrophobic interactions. Adsorption experiments indicated that CP2-Zn(2+) had the highest affinity for DE5 among these three adsorbents. Also, the adsorption capacity of CP2-Zn(2+) in DE5 and DE5-containing peptides was about 2-6 times higher than that of peptides without the DE5 sequence. Linear polymers bearing the same functional groups of the adsorbents were used as models to study the adsorption mechanism via isothermal titration calorimetry (ITC) and computer-aided analyses. The results indicated that coordination and hydrophobic interactions played the most important roles in their affinity. When two carboxyl moieties on Asp and Glu residues coordinated to CP2-Zn(2+), the hydrophobic interaction took place by the aggregation of the hydrophobic amino acid residues with phenyl group on CP2-Zn(2+). The optimal collaboration of these interactions led to the tight binding and selective adsorption of DE5-containing peptides onto CP2-Zn(2+). These results may provide new insight into the design of affinity adsorbents for peptides containing DE5-like sequences.

Predictive criteria for the outcome of patients with acute liver failure treated with the albumin dialysis molecular adsorbent recirculating system

The aim of this study was to evaluate the improvement of prognostic parameters after treatment with the molecular adsorbent recirculating system (MARS) in patients with fulminant hepatitis (FH). The parameters conducive to a positive prognosis include: Glasgow Coma Scale (GCS) score >/=11, intracranial pressure (ICP) <15 mm Hg or an improvement of the systolic peak flow of 25-32 cm/s via Doppler ultrasound in the middle cerebral artery, lactate level <3 mmol/L, tumor necrosis factor-alpha <20 pg/mL, interleukin (IL)-6 <30 pg/mL, and a change in hemodynamic instability from hyperkinetic to normal kinetic conditions, and so define the timing (and indeed the necessity) of a liver transplant (LTx). From 1999 to 2008 we treated 45 patients with FH with MARS in the intensive care unit of our institution. We analyzed all the parameters that were statistically significant using univariate analysis and considered the patients to be candidates for inclusion in a multivariate logistic regression analysis. Thirty-six patients survived: 21 were bridged to liver transplant (the BLT group) and 15 continued the extracorporeal method until native liver recovery (the NLR group) with a positive resolution of the clinical condition. Nine patients died before transplantation due to multi-organ failure. We stratified the entire population into three different groups according to six risk factors (the percentage reduction of lactate, IL-6 and ICP, systemic vascular resistance index values, GCS <9, and the number of MARS treatments): group A (0-2 risk factors), group B (3-4 risk factors), and group C (5-6 risk factors). Analyzing the prevalence of these parameters, we noted that group A perfectly corresponded to the NLR group, group B corresponded to the BLT group, and group C was composed of patients from the non-survival group; thus, we were able to select the patients who could undergo a LTx using the predictive criteria. For patients with an improvement of neurological status, cytokines, lactate, and hemodynamic parameters, LTx was no longer necessary and their treatment continued with MARS and standard medical therapy.

Future of bioartificial liver support

Many different artificial liver support systems (biological and non-biological) have been developed, tested pre-clinically and some have been applied in clinical trials. Based on theoretical considerations a biological artificial liver (BAL) should be preferred above the non-biological ones. However, clinical application of the BAL is still experimental. Here we try to analyze which hurdles have to be taken before the BAL will become standard equipment in the intensive care unit for patients with acute liver failure or acute deterioration of chronic liver disease.

Pig liver xenotransplantation as a bridge to allotransplantation: which patients might benefit?

Acute liver failure is a potentially devastating clinical syndrome that, without liver transplantation (Tx), is associated with high mortality. Rapid deterioration in clinical status and a shortage of deceased human organs prohibits liver Tx in many patients. Bridging to liver Tx has been attempted by various approaches, for example, bioartificial liver support, extracorporeal pig liver perfusion, and hepatocyte Tx, but none of these approaches has convincingly improved patient survival. The orthotopic Tx of a genetically engineered pig liver could theoretically provide successful bridging. Immediate availability, perfect metabolic condition, adequate size-match and hepatocyte mass, and freedom from potentially pathogenic microorganisms could be assured. The advantages and disadvantages of bridging by pig liver Tx compared with other approaches are discussed. The selection of patients for an initial clinical trial of pig liver Tx would be similar to that of various prior trials in patients experiencing rapid and severe deterioration in liver function. The ability to give truly informed consent for a pig bridging procedure at the time of listing for liver Tx renders the patient with acute-on-chronic liver failure or primary allograft failure is a preferable candidate for this procedure than a patient who is admitted urgently with acute (fulminant) liver failure in whom consent may not be possible. Although several barriers to successful pig organ xenoTx remain, for example, coagulation dysfunction between pig and primate, if these can be resolved by further genetic engineering of the organ-source pigs, a pig liver may prove life saving to patients dying rapidly of liver failure.

In vitro differentiation of embryonic and adult stem cells into hepatocytes: state of the art

Stem cells are a unique source of self-renewing cells within the human body. Before the end of the last millennium, adult stem cells, in contrast to their embryonic counterparts, were considered to be lineage-restricted cells or incapable of crossing lineage boundaries. However, the unique breakthrough of muscle and liver regeneration by adult bone marrow stem cells at the end of the 1990s ended this long-standing paradigm. Since then, the number of articles reporting the existence of multipotent stem cells in skin, neuronal tissue, adipose tissue, and bone marrow has escalated, giving rise, both in vivo and in vitro, to cell types other than their tissue of origin. The phenomenon of fate reprogrammation and phenotypic diversification remains, though, an enigmatic and rare process. Understanding how to control both proliferation and differentiation of stem cells and their progeny is a challenge in many fields, going from preclinical drug discovery and development to clinical therapy. In this review, we focus on current strategies to differentiate embryonic, mesenchymal(-like), and liver stem/progenitor cells into hepatocytes in vitro. Special attention is paid to intracellular and extracellular signaling, genetic modification, and cell-cell and cell-matrix interactions. In addition, some recommendations are proposed to standardize, optimize, and enrich the in vitro production of hepatocyte-like cells out of stem/progenitor cells.

Role of epigenetics in liver-specific gene transcription, hepatocyte differentiation and stem cell reprogrammation

Controlling both growth and differentiation of stem cells and their differentiated somatic progeny is a challenge in numerous fields, from preclinical drug development to clinical therapy. Recently, new insights into the underlying molecular mechanisms have unveiled key regulatory roles of epigenetic marks driving cellular pluripotency, differentiation and self-renewal/proliferation. Indeed, the transcription of genes, governing cell-fate decisions during development and maintenance of a cell's differentiated status in adult life, critically depends on the chromatin accessibility of transcription factors to genomic regulatory and coding regions. In this review, we discuss the epigenetic control of (liver-specific) gene-transcription and the intricate interplay between chromatin modulation, including histone (de)acetylation and DNA (de)methylation, and liver-enriched transcription factors. Special attention is paid to their role in directing hepatic differentiation of primary hepatocytes and stem cells in vitro.

Study of the microcirculation in hDAF transgenic rat livers xenoperfused with human blood

BACKGROUND

The microcirculation was assessed in the livers of human decay accelerating factors (hDAF) and wild-type transgenic rats by fluorescent intravital microscopy, histology and histomorphology to determine the benefits of hDAF expression for the microcirculation of a rat liver xenograft perfused with human blood.

METHODS

Male hDAF transgenic rats (group A; n = 20) and wild-type Sprague-Dawley rats (group B; n = 20) were xenoperfused with human blood, while other male wild-type Sprague-Dawley rats (group C; n = 10) were perfused with allogeneic blood. Following plasma and leukocyte staining with fluorescein sodium, and platelet staining with rhodamine, the right lobe of the liver was assessed by intravital microscopy, counting the numbers of perfused sinusoids and leukocytes adhering to the endothelium per mm(2), and calculating the acinar perfusion index (Pi). The liver underwent histological assessment at the end of each experiment. Mean +/- SEM values were calculated and the Mann-Whitney U-test was used for statistical analysis.

RESULTS

The number of perfused sinusoids was higher in the group of hDAF rat livers (group A) and controls (group C) than in the group of non-transgenic rat livers perfused with human blood (group B) (P < 0.05), although only group C still had a significantly more perfused sinusoids than the other groups after 90 min of perfusion (P < 0.05). The acinar perfusion index was higher in groups A and C than in group B (P < 0.05); here again, only group C still had a significantly higher Pi than group B after 90 min of perfusion (P < 0.05). There was a massive accumulation of leukocytes that peaked after 5 min and persisted throughout the perfusion in all three groups. Histology showed portal and subendothelial hepatic vein hemorrhage, necrosis and inflammatory reaction, which were particularly evident in group B.

CONCLUSION

In our study, rat livers transgenic for hDAF were better protected against early tissue damage by perfusion with human blood, but this did not result in a longer xenograft survival.

Role of artificial liver support in hepatic encephalopathy

Hepatic encephalopathy (HE) refers to the reversible neuropsychiatric disorders observed in acute liver failure and as a complication of cirrhosis and/or portal hypertension. This review aims to describe the pathophysiology of HE, the rationale for the use of artificial liver support in the treatment of HE, the different concepts of artificial liver support and the results obtained. Ammonia has been considered central to its pathogenesis but recently an important role for its interaction with inflammatory responses and auto-regulation of cerebral hemodynamics has been suggested. Artificial liver support might be able to decrease ammonia and modulate inflammatory mediators and cerebral hemodynamics. Bioartificial liver support systems use hepatocytes in an extracorporeal device connected to the patient's circulation. Artificial liver support is intended to remove protein-bound toxins and water-soluble toxins without providing synthetic function. Both systems improve clinical and biochemical parameters and can be applied safely to patients. Clinical studies have shown that artificial liver support, especially albumin dialysis, is able to improve HE in acute and acute-on-chronic liver failure. Further studies are required to better understand the mechanism, however, artificial liver support can be added to the therapeutic bundle in treating HE.

Hepatic assist devices: will they ever be successful?

Hepatic assist remains elusive. Bioartificial livers (BALs), consisting of liver cells or tissue in a synthetic housing, have been promising but have not proven successful in clinical trials. Artificial livers that consist of sophisticated sorbents and membranes cannot support a failing liver but may shorten episodes of acute decompensation in patients with stable cirrhosis. These artificial livers are most likely to find a place as temporary support prior to transplantation. True liver support will require a BAL. This article proposes goals for making a clinically useful BAL, with attention to systems biology and potential sources of hepatocytes.

Acute decompensation and absence of brain and kidney dysfunction predict long-term efficacy of plasma exchange in hyper-bilirubinemic cirrhotic patients awaiting liver transplantation

Various artificial liver support systems are currently used in patients with decompensated chronic liver disease or acute liver failure as a bridge to recovery or to orthotopic liver transplantation (OLT). Between June 2004 and September 2006, 9 subjects were treated with plasma exchange (PE) for acute decompensation on chronic liver disease or chronic decompensation in end-stage liver disease. All of them were awaiting OLT or were listed at the moment of decompensation. Grade II to III hepatic encephalopathy (HE) was present in 4 patients, significant renal dysfunction in 3 patients, and ascites in 6 patients. Baseline serum total bilirubin was 35.1+/-11.2 mg/dL (mean value+/-SD). The patients underwent a mean of 12.1 2-hour exchanges over 1 to 8 weeks. The 3 who recovered were alive after a mean follow-up of 22.7+/-10.3 months. There were 3 patients who underwent transplantation and 3 who died due to liver failure during treatment. Only subjects with acute decompensation and without HE or significant renal dysfunction survived without OLT. PE did not significantly modify the grade of HE or the renal function. PE seemed to be a safe, long-term, effective therapeutic option for acute decompensation among subjects with chronic liver disease without brain or renal dysfunction.

Advance in hepatic stem cells and liver injury

The liver diseases remain major causes of death all over the world. Although orthotopic liver transplantation is an effective treatment for end-stage liver diseases. However, shortage of healthy livers for transplantation worldwide have urgently limited the use of liver transplantation for acute and chronic liver diseases. Stem cells play an important role in the concert of liver regeneration. Hepatic stem cells have been shown experimentally to participate in liver proliferation. Furthermore, it has been postulated that hepatic stem cells are able to transdifferentiate into both hepatocytes and bole duct cells. These data indicate a possible role and therapeutic potential of hepatic stem cells in liver diseases. In this paper, we reviewed the application of stem cells in liver diseases.

Liver xenografts for the treatment of acute liver failure: clinical and experimental experience and remaining immunologic barriers

A critical element restricting the application of liver transplantation is the shortage of human deceased donor organs. Xenotransplantation using pig organs might be a solution to this shortage. Although the problems that still require resolution include the immunologic barrier, the potential risk of transferring infectious agents with the transplanted organ, and uncertainty about whether the transplanted organ will function satisfactorily in the human environment, recent progress in the genetic manipulation of pigs has led to the prospect that clinical xenografting, at least as a bridge to allotransplantation, may be possible in the foreseeable future. Experience with clinical auxiliary and orthotopic liver xenotransplantation and experimental liver xenotransplantation in nonhuman primate and other large animal models is reviewed, and the remaining immunologic problems are discussed. Evidence suggests that, in patients with hepatic failure, the pig liver may be less susceptible to antibody-mediated injury than other pig organs, such as the heart or kidney. Pig Kupffer cells and other macrophages will recognize and phagocytose primate red blood cells, but this problem should be overcome by pretransplant depletion of macrophages from the organ-source pig. From the evidence currently available, it does not seem unduly optimistic to anticipate that a liver from an alpha1,3-galactosyltransferase gene-knockout pig would survive at least long enough to function as a successful bridge to allotransplantation.

Sorbent-based artificial liver devices: principles of operation, chemical effects and clinical results

Devices for support of patients with liver failure are of two types: bioartificial livers and artificial livers. Bioartificial livers include hepatocytes in bioreactors to provide both excretory and synthetic liver functions. Artificial livers use nonliving components to remove toxins of liver failure, supply nutrients and macromolecules. Current artificial liver devices use columns or suspensions of sorbents (including adsorbents and absorbents) to selectively remove toxins and regenerate dialysate, albumin-containing dialysate, plasma filtrate or plasma. This article reviews three artificial liver devices. Liver Dialysis uses a suspension of charcoal and cation exchangers to regenerate dialysate. MARS uses charcoal and an anion exchanger to regenerate dialysate with albumin. Prometheus uses neutral and anion exchange resins to regenerate a plasma filtrate containing albumin and small globulins. We review the operating principles, chemical effects, clinical effects and complications of use of each type of artificial liver. These devices clearly improve the clinical condition of patients with acute or acute-on-chronic liver failure. Further randomized outcome studies are necessary to prove clinical outcome benefit of the artificial liver support devices, and define what types of patients appear most amenable to therapy.

Cells for bioartificial liver devices: the human hepatoma-derived cell line C3A produces urea but does not detoxify ammonia

Extrahepatic bioartificial liver devices should provide an intact urea cycle to detoxify ammonia. The C3A cell line, a subclone of the hepatoma-derived HepG2 cell line, is currently used in this context as it produces urea, and this has been assumed to be reflective of ammonia detoxification via a functional urea cycle. However, based on our previous findings of perturbed urea-cycle function in the non-urea producing HepG2 cell line, we hypothesized that the urea produced by C3A cells was via a urea cycle-independent mechanism, namely, due to arginase II activity, and therefore would not detoxify ammonia. Urea was quantified using (15)N-ammonium chloride metabolic labelling with gas chromatography-mass spectrometry. Gene expression was determined by real-time reverse transcriptase-PCR, protein expression by western blotting, and functional activities with radiolabelling enzyme assays. Arginase inhibition studies used N(omega)-hydroxy-nor-L-arginine. Urea was detected in C3A conditioned medium; however, (15)N-ammonium chloride-labelling indicated that (15)N-ammonia was not incorporated into (15)N-labelled urea. Further, gene expression of two urea cycle genes, ornithine transcarbamylase and arginase I, were completely absent. In contrast, arginase II mRNA and protein was expressed at high levels in C3A cells and was inhibited by N(omega)-hydroxy-nor-L-arginine, which prevented urea production, thereby indicating a urea cycle-independent pathway. The urea cycle is non-functional in C3A cells, and their urea production is solely due to the presence of arginase II, which therefore cannot provide ammonia detoxification in a bioartificial liver system. This emphasizes the continued requirement for developing a component capable of a full repertoire of liver function.