A Single Institution's Experience (1982–1999) with Plasma-Exchange Therapy in Patients with Fulminant Hepatic Failure

Fulminant hepatic failure is a rare, but often fatal complication of acute viral hepatitis. This condition, in absence of orthotopic liver transplantation (OLTx) surgery, is associated with a high mortality rate, despite the improvement of general intensive care.

Plasma-exchange (PEx) therapy has been long used to treat FHF, in particular by removing toxic substances and correcting the severe coagulopathy.

In this study we describe our experience with PEx treatment of FHF, beginning in 1982. Seventy patients affected with FHF due to various causes (HBV=40; cryptogenic/non-A, non-E=15; Amanita phalloides=8; other=7) were treated with PEx (altogether 348 sessions).

Overall survival rate, comprising patients undergoing OLTx, was 51%, a little higher than what we observed in patients (N=49) treated solely by PEx, i.e., 41%.

The best outcome predictor was FHF aetiology, owing to the good survival rate in patients with Amanita phalloides intoxication and the very poor prognosis of patients suffering from cryptogenic/non-A, non-E FHF. Moreover, the marked increase in prothrombin time and alpha-fetoprotein levels after 48 hours from admission was associated with a good prognosis, whereas the patient's age and coma grade were not clearly predictive of survival. Additionally, lymphocyte subpopulation, resulting in a CD4/CD8 ratio lower than 1.0 along with CD8 activation with HLA-DR strong expression, were associated with a high rate of mortality and morbidity.

Our data indicate that PEx therapy can improve survival in patients with sufficient residual capacity of liver regeneration. Moreover, the identification of certain prognostic factors may be useful for the rational planning of therapeutic strategy in FHF.

Development of a Non-Transformed Human Liver Cell Line with Differentiated-Hepatocyte and Urea-Synthetic Functions: Applicable for Bioartificial Liver

There is a need to develop human hepatocyte cell lines which retain both replicating capacity and highly differentiated functions to facilitate the development of an efficient bioartificial liver. The present study was undertaken to differentiate, using sodium butyrate, the actively replicating immortalized human liver cell line.

The effects of butyrate on cell growth and cell cycle were analyzed, and the albumin synthesis, cytochrome P450 and ammonia-detoxifying activity of the butyrate-treated cells were measured. Butyrate treatment resulted in G2/M arrest of the cell cycle and polygonal changes in the cell morphology. Neither the control nor the butyrate-treated cells showed transformed characteristics. Butyrate treatment increased the amount of albumin secretion, cytochrome P450 activity, and the urea production rate of the cells.

The present study provides non-transformed human hepatocytes, which can replicate unlimitedly and then restore differentiated hepatocyte-specific functions by butyrate, and therefore, have applications for the development of an efficient bioartiflcial liver

Alginate-Encapsulated Human Hepatoma C3A Cells for use in a Bioartificial Liver Device - The Hybrid-Mds

Purpose

The aim of this study was to encapsulate C3A cells into alginate microcapsules with an average diameter of ≤ 100 μm, thus enabling them to be recirculated in a bioartificial liver device based on MDS (Microsphere-based Detoxification System) technology. The microcapsules have to be permeable for essential proteins such as albumin.

Methods

C3A cells were encapsulated using alginate. The resulting alginate beads were coated with poly(diallyldimethylammoniumchloride) (pDADMAC) and poly(sodium-p-styrenesulfonate) (pSS). Their mechanical stability was tested by recirculation of the microcapsule suspension, while their permeability was determined by reverse-size exclusion chromatography and by the use of a confocal laser microscope. The metabolic activities of encapsulated C3A cells were compared to freely growing adherent C3A cells in static cultivation models. The metabolic functionality of encapsulated C3A cells in static conditions was compared to encapsulated C3A cells in a dynamic model.

Results

The mean diameter of the resulting microcapsules was 86 μm. Our experiments show that these microcapsules were permeable for albumin and the high flow rate of 600 ml/min in a dynamic model has no influence on the survival and the metabolic activities of the encapsulated cells during the tested time of 24 hours.

Conclusions

Alginate microcapsules containing C3A cells can be used to produce albumin and growth factors in a bioartificial or hybrid liver support system. Thanks to their small diameter, the microcapsules in suspension can be recirculated in the MDS.

A novel minimal invasive mouse model of extracorporeal circulation

Extracorporeal circulation (ECC) is necessary for conventional cardiac surgery and life support, but it often triggers systemic inflammation that can significantly damage tissue. Studies of ECC have been limited to large animals because of the complexity of the surgical procedures involved, which has hampered detailed understanding of ECC-induced injury. Here we describe a minimally invasive mouse model of ECC that may allow more extensive mechanistic studies. The right carotid artery and external jugular vein of anesthetized adult male C57BL/6 mice were cannulated to allow blood flow through a 1/32-inch external tube. All animals (n = 20) survived 30 min ECC and subsequent 60 min observation. Blood analysis after ECC showed significant increases in levels of tumor necrosis factor α, interleukin-6, and neutrophil elastase in plasma, lung, and renal tissues, as well as increases in plasma creatinine and cystatin C and decreases in the oxygenation index. Histopathology showed that ECC induced the expected lung inflammation, which included alveolar congestion, hemorrhage, neutrophil infiltration, and alveolar wall thickening; in renal tissue, ECC induced intracytoplasmic vacuolization, acute tubular necrosis, and epithelial swelling. Our results suggest that this novel, minimally invasive mouse model can recapitulate many of the clinical features of ECC-induced systemic inflammatory response and organ injury.

A modified surgical model of fulminant hepatic failure in the rat

BACKGROUND

There is a need for better animal models of fulminant liver failure (FHF). Eguchi et al described an interesting surgical model of FHF in the rat. This model includes 68% partial hepatectomy, ischemia of 24% of the liver mass, and 8% of remnant liver left intact. In the original description by Eguchi et al, rats were administered subcutaneous glucose. However, the authors found that normothermic FHF rats with subcutaneous glucose died from deep hypoglycemia. In this report, we describe a modification of that model, and show that administration of intravenous glucose allows better survival and development of intracranial hypertension.

METHODS

We operated on FHF rats using the procedure described by Eguchi et al, kept them normothermic, and maintained normoglycemia by continuous intravenous glucose injection (glucose 10%, 1 mL/h). At 24 h, we monitored liver blood tests (n = 5), intracranial pressure (n = 5), clinical encephalopathy, and survival (n = 10), and compared them with sham and 68% hepatectomy rats.

RESULTS

The FHF rats developed acute cytolysis, cholestasis, and liver failure, as demonstrated by the liver blood tests. They experienced progressive encephalopathy and intracranial hypertension leading to death. Mean survival was 45.9 h. Of 10 FHF rats from the survival evaluation cohort, one survived 7 d. Laparotomy showed necrosis of lateral liver lobes and enlargement of omental lobes with a normal hepatic aspect, suggesting liver recovery.

CONCLUSIONS

This surgical rat model mimics the features of human FHF and seems interesting for further research into the pathophysiology and therapeutic management of the disease.

Neurological complications of acute liver failure: pathophysiological basis of current management and emerging therapies

One of the major causes of mortality in patients with acute liver failure (ALF) is the development of hepatic encephalopathy (HE) which is associated with increased intracranial pressure (ICP). High ammonia levels, increased cerebral blood flow and increased inflammatory response have been identified as major contributors to the development of HE and the related brain swelling. The general principles of the management of patients with ALF are straightforward. They include identifying the insult causing hepatic injury, providing organ systems support to optimize the patient's physical condition, anticipation and prevention of development of complications. Increasing insights into the pathophysiological mechanisms of ALF are contributing to better therapies. For instance, the evident role of cerebral hyperemia in the pathogenesis of increased ICP has led to a re-evaluation of established therapies such as hyperventilation, N-acetylcysteine, thiopentone sodium and propofol. The role of systemic inflammatory response in the pathogenesis of increased ICP has also gained importance supporting the concept that antibiotics given prophylactically reduce the risk of developing sepsis during the course of illness. Moderate hypothermia has also been established as a therapy able to reduce ICP in patients with uncontrolled intracranial hypertension and to prevent increases in ICP during orthopic liver transplantation. Ornithine phenylacetate, a new drug in the treatment of liver failure, and liver replacement therapies are still being investigated both experimentally and clinically. Despite many advances in the understanding of the pathophysiological basis and the management of intracranial hypertension in ALF, more clinical trials should be conducted to determine the best therapeutic management for this difficult clinical event.

Lidocaine/monoethylglycinexylidide test, galactose elimination test, and sorbitol elimination test for metabolic assessment of liver cell bioreactors

Various metabolic tests were compared for the performance characterization of a liver cell bioreactor as a routine function assessment of cultures in a standby for patient application in clinical studies. Everyday quality assessment (QA) is essential to ensure a continuous level of cellular functional capacity in the development of hepatic progenitor cell expansion systems providing cells for regenerative medicine research; it is also of interest to meet safety requirements in bioartificial extracorporeal liver support systems under clinical evaluation. Quality criteria for the description of bioreactor cultures were developed using primary porcine liver cells as a model. Porcine liver cells isolated by collagenase perfusion with an average of 3 x 10(9) primary cells were used in 39 bioreactors for culture periods up to 33 days. Measurements of monoethylglycinexylidide synthesis and elimination of lidocaine, galactose elimination, and sorbitol elimination proved to be useful for routine QA of primary liver cell cultures. We demonstrate two methods for dispensing test substances, bolus administration and continuous, steady-state administration. Bolus test data were grouped in Standard, Therapy, Infection/Contamination, and Cell-free control groups. Statistical analyses show significant differences among all groups for every test substance. Post hoc comparisons indicated significant differences between Standard and Cell-free groups for all elimination parameters. For continuous tests, results were categorized according to number of culture days and time-dependent changes were analyzed. Continuous administration enables a better view of culture health and the time dependency of cellular function, whereas bolus administration is more flexible. Both procedures can be used to define cell function. Assessment of cellular function and bioreactor quality can contribute significantly to the quality of experimental or clinical studies in the field of hepatic bioreactor development.

Bioartificial Organ Grafts: A View at the Beginning of the Third Millennium

An immunoisolated collection of cells, which communicate and exchange essential factors, co-stimulatory hormones, as well as providing immunoprotection and immunomodulation, can be prepared, given existing scientific and medical know-how, within two decades. These "Bioartificial Organ Grafts" have advantages relative to isolated cell therapies, including beta-cell encapsulation for diabetes treatment, and xenotransplantation, which has a de facto moratorium. This paper documents that the majority of the research for the bioartificial organ grafts has been concluded, with the remaining hurdles minimum in comparison. The use of co-encapsulation and the induction of local immune-privilege will provide a more sensitive humoral hormonal response and graft survival, without systemic immunosuppression. A call for the staged implementation of bioartificial organ grafts, based on the best available medical practice, materials, tissue and technology available, is advocated. The implementation of bioartificial organ grafts can begin within the next two years, based on allografts succeeded by genetically modified human tissue, without the need to pass through a xenograft stage.

The place of adsorption and biochromatography in extracorporeal liver support systems

Artificial and bioartificial liver devices aim at replacing some or all liver functions in the cases of end stage or fulminant disorders. Among all of its function, liver plays a key role in detoxification of substances that are hydrosoluble or bound to albumin. In this paper, the authors first reviewed the requirements for temporary liver support, then the adsorption-based systems that can be found on the market and finally propose new applications of biochromatography using perfusion-based bioartificial systems.

Modern management of acute liver failure

Liver transplantation has revolutionized the management of acute or fulminant liver failure. Overall success rates of liver transplantation are satisfactory, although not as high as for elective transplantation. Although the bulk of liver transplants use standard whole grafts, interesting data are emerging on auxiliary liver grafts and donations from living donors. Liver transplantation is an integral part of management protocols complementing the sophisticated critical care protocols that have contributed significantly to the overall improved outcomes seen in acute liver failure. The potential for liver support devices to have an impact on the need for liver transplantation and outcomes after transplantation remains exciting.

Brain edema and intracranial hypertension in fulminant hepatic failure: Pathophysiology and management

Intracranial hypertension is a major cause of morbidity and mortality of patients suffering from fulminant hepatic failure. The etiology of this intracranial hypertension is not fully determined, and is probably multifactorial, combining a cytotoxic brain edema due to the astrocytic accumulation of glutamine, and an increase in cerebral blood volume and cerebral blood flow, in part due to inflammation, to glutamine and to toxic products of the diseased liver. Validated methods to control intracranial hypertension in fulminant hepatic failure patients mainly include mannitol, hypertonic saline, indomethacin, thiopental, and hyperventilation. However all these measures are often not sufficient in absence of liver transplantation, the only curative treatment of intracranial hypertension in fulminant hepatic failure to date. Induced moderate hypothermia seems very promising in this setting, but has to be validated by a controlled, randomized study. Artificial liver support systems have been under investigation for many decades. The bioartificial liver, based on both detoxification and swine liver cells, has shown some efficacy on reduction of intracranial pressure but did not show survival benefit in a controlled, randomized study. The Molecular Adsorbents Recirculating System has shown some efficacy in decreasing intracranial pressure in an animal model of liver failure, but has still to be evaluated in a phase III trial.

Molecular Adsorbent Recirculating System in Liver Transplantation: Safety and Efficacy

We assessed the safety and clinical efficacy of the Molecular Adsorbent Recirculating System (MARS) in liver failure patients admitted to our intensive care unit (ICU) from May 2000 to February 2006. Of 28 adult patients with bilirubin >15 mg/dL and hepatic encephalopathy (HE) grade > or =2 or hepato-renal syndrome, 22 patients were included in the study, because 6 patients were older than 65 years of age or showed recent alcohol abuse or extrahepatic malignancy. Patients were assigned to 2 groups according to whether MARS therapy was associated with a transplantation procedure: 11 patients received MARS therapy and liver transplantation (OLT group) and 11 patients received MARS therapy alone (non-OLT group). Five of 11 patients in the OLT group were listed for transplantation and 6 patients with graft failure for retransplantation. The patients in the OLT and non-OLT groups were similar in MELD, SOFA, and SAPS scores. All patients were stable and free from complications. MARS significantly reduced bilirubin, bile acids, and blood urea nitrogen (BUN) levels in both groups (P < .05), whereas a significant decrease in ammonia level was observed in the OLT group. Patient survival rates at 3 and 6 months in the OLT group were 91% and 73%, respectively, and in the non-OLT group, 9% and 9%, respectively (P < .001). MARS was safe and well tolerated, improving biochemical parameters, neurological function, and pruritus. In terms of survival, the use of MARS alone was not effective due to the high rate of multiple organ failure. Nevertheless, the association of MARS with a transplant/retransplantation procedure was highly effective.

Personal view: current role of artificial liver support devices

Enthusiasm for liver support devices, particularly cell-based biological systems and albumin dialysis, increased over the last decade and there has been considerable clinical activity both within and without the construct of clinical trials. Most data have been generated on patients with acute liver failure or in patients with decompensation of chronic liver disease, often referred to as acute-on-chronic liver failure. In acute liver failure liver, liver support devices are more realistically being used as a 'bridge' to liver transplantation rather than to transplant-free survival. In acute-on-chronic liver failure the clinical objective of attaining clinical stability with treatment appears more achievable. The so-called bioartificial liver device, based on porcine hepatocytes, is the most extensively evaluated biological device. A sizeable clinical trial failed to demonstrate efficacy, but secondary analyses suggest it would be unwise to assume futility had been established with this device. Molecular adsorbent recirculating system leads the way in the non-biological category in terms of the number of patients treated, but data from large clinical trials are not yet available. One of the strongest conclusions of this review is that the amount of high-quality data available on liver support devices dramatically understates the effort and money that have been expended in their assessment. It is very clear that randomized controlled trials are mandatory to establish clinical efficacy, but it is less clear how the ideal trial should be constructed.

Cytomimetic engineering of hepatocyte morphogenesis and function by substrate-based presentation of acellular E-cadherin

Although cadherin-mediated intercellular contacts can be integral to the maintenance of functionally competent hepatocytes in vitro, the ability to engineer hepatocellular differentiated function via acellular E-cadherin has yet to be thoroughly explored. To investigate the potential of substrate-presented, acellular E-cadherin to modulate hepatocellular self-assembly and functional fate, rat hepatocytes were cultured at sparse densities on surfaces designed to display recombinant E-cadherin/Fc chimeras. On these substrates, hepatocytes were observed to recognize microdisplayed E-cadherin/Fc and responded by modulating the spatial distribution of the intracellular cadherin-complexing protein beta-catenin. Substrate-presented E-cadherin/Fc was also found to markedly alter patterns of hepatocyte morphogenesis, as cellular spreading and two-dimensional reorganization were significantly inhibited under these conditions, leading to multicellular aggregates that were considerably more three-dimensional in nature. Increasing cadherin exposure was also associated with elevated levels of albumin and urea secretion, two markers of hepatocyte differentiation, over control cultures. This suggested that cell-substrate cadherin engagement established more functionally competent hepatocellular phenotypes, coinciding with the notion that E-cadherin is a differentiation-inducing ligand for these cells. The morphogenetic and function-promoting effects of substrate-bound E-cadherin/Fc were further enhanced under conditions in which protein A was utilized as an anchoring molecule to present cadherin molecules, suggesting that ligand mobility may play an important role in the effective establishment of cell-to-substrate cadherin interactions. Interestingly, the percent increase in function detected for conditions of high cadherin exposure versus control cultures was found to be substantially higher at extremely low cell densities. This observation indicated that hepatocytes respond to substrate-presented E-cadherin even in the absence of native intercellular interactions and associated juxtacrine signaling. The incorporation of acellular E-cadherin on biomaterial substrates may thus potentially present a means to prevent hepatocellular dedifferentiation by maintaining liver-specific function in otherwise severely functionally repressive culture conditions.

Bioartificial liver systems: current status and future perspective

Because the liver is a multifunctional and a vital organ for survival, the management of acute liver failure requires the support of a huge number of metabolic functions performed by the organ. Many early detoxification-based artificial liver techniques failed to treat the patients owing to the inadequate support of the many essential hepatic functions. For this reason, a bioartificial liver (BAL) comprising of viable hepatocytes on a mechanical support is believed to more likely provide these essential functions than a purely mechanical device. From 1990, nine clinical studies of various BAL systems have been reported, most of which utilize a hollow fiber technology, and a much larger number of various BAL systems have been suggested to show an enhanced performance. Safety issues such as immunological reactions, zoonosis and tumorgenicity have been successfully addressed for regulatory approval, but a recent report from a large-scale, randomized, and controlled phase III trial of a leading BAL system (HepatAssist) failed to meet our expectation of efficacy in terms of the overall survival rate. In this paper, we review the current BAL systems actively studied and discuss critical issues such as the hepatocyte bioreactor configuration and the hepatocyte source. On the basis of the insights gained from previously developed BAL systems and the rapid progress in stem cell technology, the short-term and long-term future perspectives of BAL systems are suggested.

Clinical application of bioartificial liver support systems

OBJECTIVE

To review the present status of bioartificial liver (BAL) devices and their obtained clinical results.

BACKGROUND

Acute liver failure (ALF) is a disease with a high mortality. Standard therapy at present is liver transplantation. Liver transplantation is hampered by the increasing shortage of organ donors, resulting in high incidence of patients with ALF dying on the transplantation waiting list. Among a variety of liver assist therapies, BAL therapy is marked as the most promising solution to bridge ALF patients to liver transplantation or to liver regeneration, because several BAL systems showed significant survival improvement in animal ALF studies. Until today, clinical application of 11 different BAL systems has been reported.

METHODS

A literature review was performed using MEDLINE and additional library searches. Only BAL systems that have been used in a clinical trial were included in this review.

RESULTS

Eleven BAL systems found clinical application. Three systems were studied in a controlled trial, showing no significant survival benefits, in part due to the insufficient number of patients included. The other systems were studied in a phase I trial or during treatment of a single patient and all showed to be safe. Most BAL therapies resulted in improvement of clinical and biochemical parameters.

CONCLUSIONS

Bioartificial liver therapy for bridging patients with ALF to liver transplantation or liver regeneration is promising. Its clinical value awaits further improvement of BAL devices, replacement of hepatocytes of animal origin by human hepatocytes, and assessment in controlled clinical trials.

Influence of polymer membrane porosity on C3A hepatoblastoma cell adhesive interaction and function

The effect of the porosity of acrylonitrile-N-vinylpyrrolidone copolymer membranes on human C3A hepatoblastoma cell adhesive interaction and functioning is investigated on four membranes with an average pore size ranging between 6 and 12 nm. Adhesion of C3A cells was quantified and characterized by studying overall cell morphology and focal adhesion formation. Cell-cell interactions were characterized by E-cadherin expression and organization. Cell growth, fibronectin synthesis and cytochrome P450 activity were estimated as criteria of functional cell activity. The results suggest that membrane porosity influences the initial cell-surface interactions since an increasing pore size augmented cell adhesion and aggregate formation. Cell growth after 7 d was diminished on membranes with an average pore size of 12 nm. The activity of P450 measured by 7-ethoxycoumarin conversion at day 7 was influenced by membrane topography representing a clear optimum in the range of 7-10 nm pore size. These results indicate that membrane porosity is a determinant for the function of hepatocytes in extracorporal liver assist devices.

The role of cytokines in liver failure and regeneration: potential new molecular therapies

The liver is a unique organ, and first in line, the hepatocytes encounter the potential to proliferate during cell mass loss. This phenomenon is tightly controlled and resembles in some way the embryonal co-inhabitant cell lineage of the liver, the embryonic hematopoietic system. Interestingly, both the liver and hematopoietic cell proliferation and growth are controlled by various growth factors and cytokines. IL-6 and its signaling cascade inside the cells through STAT3 are both significantly important for liver regeneration as well as for hematopoietic cell proliferation. The process of liver regeneration is very complex and is dependent on the etiology and extent of liver damage and the genetic background. In this review we will initially describe the clinical relevant condition, portraying a number of available animal models with an emphasis on the relevance of each one to the human condition of fulminant hepatic failure (FHF). The discussion will then be focused on the role of cytokines in liver failure and regeneration, and suggest potential new therapeutic modalities for FHF. The recent findings on the role of IL-6 in liver regeneration and the activity of the designer IL-6/sIL-6R fusion protein, hyper-IL-6, in particular, suggest that this molecule could significantly enhance liver regeneration in humans, and as such could be a useful treatment for FHF in patients.

Development of a new bioartificial liver using a porcine autologous biomatrix as hepatocyte support

Long-term maintenance of hepatocyte viability and differentiated function expression is crucial for bioartificial liver support. The maintenance of hepatocyte function in a bioreactor is still a problem. A major advance was the recognition that hepatocytes in attachment cultures can maintain their differentiation longer. To restore hepatocyte polarity and prolong their function, we developed a new bioreactor with a cross-flow geometry configuration and an original hepatocyte extracellular autologous biomatrix (Porcine Bio-Matrix) support. To test this new bioreactor, we compared it with a standard bioartificial liver cartridge in a suitable surgical model of acute liver failure in pigs. In our model, we performed a total hepatectomy, followed by partial liver transplantation after an 18 hour anhepatic phase. The results showed that the bioreactor containing the biomatrix was able to bridge the animal to transplantation and to sustain the transplanted liver until all function recovered (80% of animals survived, p = 0.0027). No animal survived more than 24 hours after liver transplantation in the group treated with the traditional bioartificial liver, whereas hepatocyte viability on the Porcine Bio-Matrix was 65% after 12 hours of treatment. The results suggest that our biomatrix is a suitable cell support and guarantees long-term maintenance of metabolic activity of hepatocytes. Further studies are needed, but the results obtained with this new three-dimensional bioreactor are promising, and its potential is attractive.

Review of methods to remove protein-bound substances in liver failure

A wide range of toxic substances accumulates in the circulation of patients with liver failure, including more lipid-soluble substances, which bind to plasma proteins. Serum albumin is the most important binding protein for ligands such as bilirubin and bile acids, which are potentially toxic and can cause apoptosis in astrocytes and hepatocytes respectively in vitro. Resin haemoperfusion was originally investigated to remove these compounds, as well as inflammatory cytokines. Current effective methods for removal of protein-bound compounds in patients with liver failure include high volume plasmapheresis and different forms of albumin dialysis. Bioartificial liver support systems need adsorbent and/or dialysis modules to replace the lack of excretory function.

A method to assess biochemical activity of liver cells during clinical application of extracorporeal hybrid liver support

Biochemical activity of a hybrid liver support system based on porcine liver cells was investigated in patients suffering from acute liver failure, coma stage III-IV Patient plasma was drawn systemically and after circulation through the bioreactor at four hour intervals. A method is used that takes into account the rate of plasma flow and the differences in plasma concentration systemically and after circulation through the liver support system to determine the net release or uptake of metabolites such as ammonia, urea and glucose. Urea release (mean 2.28+/-0.37 micromol/h/g cells) and ammonia uptake (mean 0.17+/-0.11 micromol/h/g cells) was seen during treatment, an active role of the system in glucose metabolism was observed. All patients were bridged successfully to liver transplantation.

TECA hybrid artificial liver support system in treatment of acute liver failure

AIM: To assess the efficacy and safety of TECA type hybr id artificial liver support system (TECA-HALSS) in providing liver function of detoxification, metabolism and physiology by treating the patients with acute liv er failure (ALF).

METHODS: The porcine liver cells (1-2) × 10¹⁰ were separated from the Chinese small swine and cultured in the bioreactor of TECA-BALSS at 37.0 °C and circulated through the outer space of the hollow fiber tubes in BALSS. The six liver failure patients with various degree of hepatic coma were treated by TECA-HALSS and with conventional medicines. The venous plasma of the patients was separated by a plasma separator and treated by charcoal adsorbent or plasma exchange. The plasma circulated through the inner space of the hollow fiber tubes of BALSS and mixed with the patients’ blood cells and flew back to their blood circulation. Some small molecular weight substances were exchanged between the plasma and porcine liver cells. Each treatment lasted 6.0-7.0 h. Physiological and biochemical parameters were measured before, during and after the treatment.

RESULTS: The average of porcine liver cells was (1.0-3.0) × 10¹⁰ obtained from each swine liver using our modified enzymatic digestion method. The survival rate of the cells was 85%-93% by trypan blue stain and AO/PI fluorescent stain. After cultured in TECA-BALSS bioreactor for 6 h, the survival rate of cells still remained 70%-85%. At the end of TECA-HALSS treatment, the levels of plasma NH₃, ALT, TB and DB were significantly decreased. The patients who were in the state of drowsiness or coma before the treatment improved their appetite significantly and regained consciousness, some patients resumed light physical work on a short period after the treatment. One to two days after the treatment, the ratio of PTA increased warkedly. During the treatment, the heart rates, blood pressure, respiration condition and serum electrolytes (K⁺, Na⁺ and Cl^-) were stable without thrombosis and bleeding in all the six patients.

CONCLUSION: TECA-HALSS treatment could be a rapid, safe and efficacious method to provide temporary liver support for patients with ALF.

Bridge therapy to liver transplantation in fulminant hepatic failure

The management of patients with fulminant hepatic failure is a major clinical endeavor. Early intensive care at an institution able to perform liver transplantation is essential. It is recognized that therapy focused solely on attempts at preventing/reversing increased intracranial pressure, and the treatment of other failing organs as they occur falls well short of ideal. This review covers the non-biological and biological techniques utilized in efforts to support liver function. The goal is to foster recovery, or to buy enough time for successful liver transplantation. Prospective, controlled trials are beginning to acknowledge subgroups of fulminant hepatic failure and properly randomize therapy. Our understanding of the essential elements of liver support is improving, but no single device has yet proved indispensable.

Long-term maintenance of cytochrome P450 activities by rat hepatocyte/3T3 cell co-cultures in heparinized human plasma

Little information on the effect of plasma on hepatocyte cytochrome P450 (CYP) activities is currently available. We characterized the effect of plasma on CYPs of hepatocyte-mesenchymal cell co-cultures, which exhibit stable liver specific functions and may be potentially useful for bioartificial liver design. Rat hepatocyte-mouse 3T3-J2 cell co-cultures were maintained for 6 days in medium, and then switched to heparinized human plasma containing 3-methylcholanthrene (3MC; 2 microM), phenobarbital (PB; 1 mM), or no inducer for up to 7 days. CYP activities were measured in situ based on the o-dealkylation of ethoxy- (EROD), methoxy- (MROD), pentoxy- (PROD), or benzyloxy- (BROD) resorufin. Plasma alone increased PROD/BROD but not EROD/MROD. The endogenous inducer was in the high molecular weight fraction (>5 kD) of plasma and inhibited by >5 nM okadaic acid and >10 microM dibutyryl cyclic AMP, two inhibitors of PB-inducible CYPs. Furthermore, plasma increased CYP1A1 and CYP2B1/2 mRNA levels. In plasma, 3MC induced EROD/MROD to about 60% of the level induced in culture medium while PB induced PROD/BROD that were three- to 10-fold above levels induced in medium. CYP activities decreased between days 2 and 7 of plasma exposure, but were enhanced by plasma supplementation with amino acids, insulin, glucagon, and hydrocortisone.

Artificial liver support devices for fulminant liver failure

Artificial liver-support devices attempt to bridge patients with fulminant hepatic failure until either a suitable liver allograft is obtained for transplantation or the patient's own liver regenerates sufficiently to resume normal function. It is thought that toxins contribute to the clinical picture of fulminant hepatic failure. The earliest reports of successful toxin removal were blood- and plasma-exchange transfusions. Given these successful case reports, mechanical liver-support devices were designed to filter toxins. These mechanical devices used hemodialysis, charcoal hemoperfusion, hemoperfusion through cation-exchange resins, hemodiabsorption, and combinations of all of these techniques as in the MARS liver-support device. Despite promising case reports and small series, no controlled studies of mechanical devices have ever showed a long-term survival benefit. Thus, the removal of presumed toxins seems to be insufficient to support patients with fulminant hepatic failure, and the biologic function of the liver must also be replaced. Attempts at replacing the biologic function have included extracorporeal liver perfusion, cross-circulation, and hepatocyte transplantation. Current technologies have combined mechanical and biologic support systems in hybrid liver-support devices. The mechanical component of these hybrid devices serves both to remove toxins and to create a barrier between the patient's serum and the biologic component of the liver-support device. The biologic component of these hybrid liver support devices may consist of liver slices, granulated liver, or hepatocytes from low-grade tumor cells or porcine hepatocytes. These biologic components are housed within bioreactors. Currently the most clinically studied bioreactors are those that use capillary hollow-fiber systems. Both the bioartificial liver by Demetrious and the extracorporeal liver-assist device by Sussman and Kelly are in clinical trials. Although the trials seemed to have yielded good survival data when the devices are used as a bridge to transplantation, the type and degree of liver support provided by these devices remains uncertain. Thus, despite decades of great progress in the field of artificial liver support, no one technique alone yet provides sufficient liver support. A hybrid system seems to be the best option at present. Still to be determined is the best tissue to use, how much liver tissue should be used, and the optimal design of the bioreactor.

Optimization of rat hepatocyte culture in citrated human plasma

BACKGROUND

Maintenance of liver-specific functions in hepatocyte cultures during plasma exposure is critical for the clinical application of bioartificial liver assist systems. Sodium citrate is a common anticoagulant but has been shown to be cytotoxic to hepatocytes. We have tested the effect of various supplements on the viability and function of adult primary rat hepatocytes exposed to citrated plasma.

MATERIALS AND METHODS

Freshly isolated rat hepatocytes were cultured in the collagen gel sandwich configuration in culture medium for 6 days followed by exposure to citrated human plasma with various supplements for 1 week. Controls were left in culture medium throughout. Viability and synthetic functions were evaluated.

RESULTS

Hepatocytes exposed to unsupplemented citrated plasma lost significant viability and function within the first 2 days. Cells cultured in plasma supplemented with a fivefold concentrate of standard hepatocyte culture medium maintained urea (1. 2-2.1 micromol/day/10(6) cells) and albumin (51-62 microg/day/10(6) cells) synthesis rates equal to or higher than those of controls. Among the various components of the concentrated medium supplement, calcium chloride (1.8 mM), magnesium sulfate (0.8 mM), amino acids (fourfold Basal Medium Eagle amino acids including 4 mM glutamine), and glucagon (14 ng/ml) were found to be essential in maintaining urea synthesis. Maintenance of a high albumin synthesis rate also required the addition of hydrocortisone (7.5 microg/ml) and insulin (0.5 U/ml).

CONCLUSIONS

Appropriate metabolic and hormonal supplementation of citrated human plasma prevents its cytotoxic effects and may be used in conjunction with in vivo use of bioartificial liver assist systems.

Long-term culture of glutamine synthetase-transfected HepG2 cells in circulatory flow bioreactor for development of a bioartificial liver

Glutamine synthetase (GS) is involved in an accessory pathway of ammonia removal in mammals. To develop a bioartificial liver with a human cell line, GS gene was transfected into HepG2 cells, which had no ammonia removal activity. After culturing in the presence of methionine sulfoximine (MSX), a GS inhibitor, we obtained a MSX-resistant HepG2 subline (GS-HepG2), which had amplified GS gene; ammonia removal activity was estimated to be 1/7 of that of rat primary culture hepatocytes. The cells were cultured in a circulatory flow bioreactor for 109 days, while they multiplied from 5 x 10(7) to 4 x 10(9) cells. Three days after inoculation, the ammonia level of the culture medium was lowered to a level maintained thereafter, suggesting that using recombinant cell lines for bioartificial livers enables long-term repeated treatment for hepatic failure patient. Judging from the rate of decrease in the amount of the added ammonia, the ammonia removal capability of 4 x 10(9) GS-HepG2 cells was almost equivalent to 5 x 10(8) porcine hepatocytes inoculated into the circulatory flow bioreactor. Apart from their ammonia removal activity, GS-HepG2 cells eliminated human tumor necrosis factor-alpha (TNF-alpha). Cytokine removal therefore promises to be another useful property of bioreactor cells.

Nutrition support for individuals with liver failure

The prevalence of liver diseases is increasing in the United States, particularly as a result of the recent hepatitis C epidemic. In the past, patients who developed fulminant hepatic failure or cirrhosis owing to a chronic liver disease were likely to expire. During the last 15-20 years, liver transplantation has given these patients a chance at survival. Progressive nutrition deficiencies and muscle wasting are universal problems in these patients. Left untreated, the progressive wasting of liver disease leads to infection and an increased risk of death owing to infection both before and after transplantation. Aggressive nutritional support is essential to optimize the care of these patients and to enable them to obtain and survive a liver transplant and gain access to a new life following a successful liver engraftment.

Enhancing hepatocyte adhesion by pulsed plasma deposition and polyethylene glycol coupling

Decreased hepatocyte adhesion to polymeric constructs limits the function of tissue engineered hepatic assist devices. We grafted adhesion peptides (RGD and YIGSR) to polycaprolactone (PCL) and poly-L-lactic acid (PLLA) in order to mimic the in vivo extracellular matrix and thus enhance hepatocyte adhesion. Peptide grafting was done by a novel technique in which polyethylene glycol (PEG)-adhesion peptide was linked to allyl-amine coated on the surface of PCL and PLLA by pulsed plasma deposition (PPD). Peptide grafting density, quantified by radio-iodinated tyrosine in YIGSR, was 158 fmol/cm(2) on PLLA and 425 fmol/cm(2) on PCL surfaces. The adhesion of hepatocytes was determined by plating 250,000 hepatocytes/well (test substrates were coated on 12 well plates) and quantifying the percentage of adhered cells after 6 h by MTT assay. Adhesion on PCL surfaces was significantly enhanced (p < 0.05) by both YIGSR (percentage of adhered cells = 53 +/- 7%) and RGD (53 +/- 12%) when compared to control surfaces (31 +/- 8%). Hepatocyte adhesion on PLLA was significantly (p < 0.05) enhanced on PLLA-PEG-RGD surfaces (76 +/- 14%) compared to control surfaces (42 +/- 19%) and more (68 +/- 25%) but not statistically significant (p = 0.15) on PLLA-PEG-YIGSR surfaces compared to control surfaces. These results indicate that hepatocyte adhesion to PCL and PLLA based polymeric surfaces can be enhanced by a novel adhesion peptide grafting technique using pulsed plasma deposition and PEG cross-linking.

Is there a future for liver-assist devices?

Patients with fulminant hepatic failure fall into two categories: those who will not recover without hepatic replacement, and those with severe but potentially reversible liver injury whose livers have the potential to recover and/or regenerate. Liver support systems must provide physiologic support, rendering the patient hemodynamically stable and "bridging" the patient to transplantation, or allowing the native liver to recover and/or regenerate. Recent limited successes with bioartificial liver support for patients with fulminant liver failure are encouraging. However, these preliminary results come without randomization or control groups and without stratification by disease etiology or severity. It is hoped that randomized, controlled trials will answer important questions about the efficacy of these systems.