The effects of serum from patients with acute liver failure on the growth and metabolism of Hep G2 cells

Assessment of biological functions for C3A cells interacting with adverse environments of liver failure plasma

BACKGROUND

For its better differentiated hepatocyte phenotype, C3A cell line has been utilized in bioartificial liver system. However, up to now, there are only a few of studies working at the metabolic alternations of C3A cells under the culture conditions with liver failure plasma, which mainly focus on carbohydrate metabolism, total protein synthesis and ureagenesis. In this study, we investigated the effects of acute liver failure plasma on the growth and biological functions of C3A cells, especially on CYP450 enzymes.

METHODS

C3A cells were treated with fresh DMEM medium containing 10% FBS, fresh DMEM medium containing 10% normal plasma and acute liver failure plasma, respectively. After incubation, the C3A cells were assessed for cell viabilities, lactate dehydrogenase leakage, gene transcription, protein levels, albumin secretion, ammonia metabolism and CYP450 enzyme activities.

RESULTS

Cell viabilities decreased 15%, and lactate dehydrogenase leakage had 1.3-fold elevation in acute liver failure plasma group. Gene transcription exhibited up-regulation, down-regulation or stability for different hepatic genes. In contrast, protein expression levels for several CYP450 enzymes kept constant, while the CYP450 enzyme activities decreased or remained stable. Albumin secretion reduced about 48%, and ammonia accumulation increased approximately 41%.

CONCLUSIONS

C3A cells cultured with acute liver failure plasma showed mild inhibition of cell viabilities, reduction of albumin secretion, and increase of ammonia accumulation. Furthermore, CYP450 enzymes demonstrated various alterations on gene transcription, protein expression and enzyme activities.

The Effect of Serum from Liver Cancer Patients on the Growth and Function of Primary and Immortalised Hepatocytes

A limiting factor in the efficacy of bioartificial liver (BAL) for the treatment of liver failure is the toxicity of the patients’ serum to the hepatocytes in the device. This study investigates the interaction of liver cancer patient serum with primary and immortalised rat hepatocytes. Liver cancer serum increased the growth rate of immortalised hepatocytes, without affecting reduced glutathione levels. The activities of DT-diaphorase and pi glutathione-S-transferase (GST), enzymes associated with de-differentiation, were also increased. Exposure of primary hepatocytes to liver cancer serum resulted in a decrease in cytochrome P450 (CYP) content, and in P450 dependent metabolism of testosterone. Formation of 2-alpha- and 6-beta- hydroxy testosterone was decreased. These reactions are predominantly associated with CYP 2C11 and 3A1 respectively in normal rat liver. The activity of total GST was also decreased, although that of the pi isoenzyme of GST was not affected. Our results suggest that exposure of hepatocytes in a bioreactor to liver cancer patient serum will result in overgrowth of cells, if proliferating cells are being used, and in de-differentiation. The serum may have to be pretreated with adsorbants to remove toxins prior to BAL treatment.

A promising hepatocyte-like cell line, CCL-13, exhibits good liver function both in vitro and in an acute liver failure model

BACKGROUND

A great many patients awaiting liver transplantation die because of the shortage of donor livers. To resolve the problem, liver support systems like bioartificial livers (BALs) have become subjects of active investigation. However, the problem with BALs is that it is difficult to find a source of healthy hepatic cells with good liver function. This study explored the possibility of employing Chang liver cells (ATCC CCL-13), a human hepatoma cell line as a source for liver support.

METHODS

To evaluate the function of Chang liver cells in vitro, hepatocyte markers were measured by Western blotting and laser confocal microscopy. The gene expression of hepatic markers was examined by reverse transcriptase polymerase chain reaction (RT-PCR). After acute liver failure (ALF) was established by 90% partial hepatectomy, Chang liver cells were intrasplenically transplanted for treatment.

RESULTS

In vitro, Western blotting and laser confocal microscopy showed conspicuous expression of liver function markers, such as albumin, uridine diphosphate glucuronosyltransferase, and cytochrome P450 3A4 by Chang liver cells. RT-PCR revealed expression of related genes at the mRNA level. The survival of rats receiving transplanted Chang liver cells reached 40% versus 0% among the controls (P < .01). Liver function of rats receiving transplanted Chang liver cells was improved at 24 hours after ALF, as evidenced by decreased levels of alanine transaminase, aspartate aminotransferase, bilirubin, and alkaline phosphate.

CONCLUSIONS

Chang liver cells, which express liver function markers and exert obvious liver-protective effects in ALF can serve in liver support systems.

Effects of acute-liver-failure-plasma exposure on hepatic functionality of HepaRG-AMC-bioartificial liver

BACKGROUND & AIMS

The AMC-bioartificial liver loaded with the human hepatoma cell line HepaRG as biocomponent (HepaRG-AMC-BAL) has recently proven efficacious in rats with acute liver failure (ALF). However, its efficacy may be affected by cytotoxic components of ALF plasma during treatment. In this study, we investigated the effects of ALF-plasma on the HepaRG-AMC-BAL.

METHODS

HepaRG-AMC-BALs were connected to the blood circulation of rats with total liver ischaemia, either during the first 5 h after induction of ischaemia (mild ALF group), or during the following 10 h (severe ALF group). After disconnection, the BALs were assessed for cell leakage, gene transcript levels, ammonia elimination, urea production, cytochrome P450 3A4 activity, apolipoprotein A 1 production, glucose and amino acid metabolism.

RESULTS

Cell leakage increased 2.5-fold in the severe ALF group, but remained limited in all groups. Hepatic gene transcript levels decreased (max 40-fold) or remained stable. In contrast, hepatic functions increased slightly or remained stable. Particularly, urea production increased 1.5-fold, with a concurrent increase in arginase 2 transcription and arginine consumption, with a trend towards reduced conversion of ammonia into urea. The amino acid consumption increased, however, the net glucose consumption remained stable.

CONCLUSIONS

The HepaRG-AMC-BAL retains functionality after both mild and severe exposure to ALF plasma, but urea production may be increasingly derived from arginase 2 activity instead of urea cycle activity. Nevertheless, the increase in cell leakage and decrease in various hepatic transcript levels suggest that a decrease in hepatic functionality may follow upon extended exposure to ALF plasma.

Plasma from patients with liver failure inhibits the proliferation of HepG2 cells

AIM: To explore the mechanisms by which plasma from patients with liver failure inhibits the proliferation of HepG2 cells and to evaluate whether epidermal growth factor (EGF) can reverse this inhibitory effect.

METHODS: Plasma samples were collected from three patients with acute-on-chronic liver failure during plasma exchange therapy and treated with heparin. After HepG2 cells were cultured in medium containing 50% plasma from patients with liver failure with or without EGF stimulation, cell proliferation and apoptosis were detected by methyl thiazolyl tetrazolium (MTT) assay and Hoechst staining, respectively. The expression of intracellular cyclin D1 and cyclin-dependent kinase 4 (CDK4) in HepG2 cells was examined by Western blotting.

RESULTS: Treatment with 50% plasma from patients with liver failure for 12 to 72 hours significantly inhibited the proliferation of HepG2 cells in a time-dependent manner when compared to cells cultured with 50% normal control plasma (NCP). EGF at a concentration of 5, 10 or 20 μg/L significantly induced the proliferation of HepG2 cells cultured with NCP, while only high-dose EGF (20 μg/L) showed a transient promotion to the proliferation of HepG2 cells cultured with plasma from patients with liver failure. After stimulation with 20 μg/L EGF, the proliferation was still significantly inhibited in cells cultured with patient plasma compared to those cultured with NCP. The presence of 50% patient plasma did not significantly alter apoptosis index of HepG2 cells (P > 0.05). The expression of intracellular cyclin D1 and CDK4 in HepG2 cells was obviously inhibited after treatment with patient plasma for 12 to 72 hours.

CONCLUSION: Plasma from patients with liver failure inhibits the proliferation of HepG2 cells possibly by down-regulating the expression of intracellular cyclin D1 and CDK4. EGF can not reverse this inhibitory effect.

Construction and functional evaluation of a liver cell line tranfected with a vector expressing cytochrome P450 3A4 and glutathione-S-transferase A1

AIM: To generate a new cell strain that could be used in the bioartificial liver support system.

METHODS: The C3A cell line was transfected with the recombinant plasmid pBudCE4.1-CYP 3A4-GST A1, which expresses both cytochrome P450 3A4 (CYP 3A4) and glutathione-S-transferase A1 (GSTA1), and cultured in MEM containing 400 mg/L Zeocin for 2 wk. The obtained cell line was named C3A-Unoptimized. The expression of CYP 3A4 and GSTA1 in C3A-Unoptimized cells was detected by qRT-PCR, and the function of the C3A-Unoptimized cell line was evaluated.

RESULTS: The C3A-Unoptimized cell line stably expressed both CYP 3A4 and GST A1. The expression levels of CYP 3A4 and GSTA1 were higher in C3A-Unoptimized cells than in non-transfected C3A cells. Chromatogram assay showed that the activity of CYP 3A4 could be detected in C3A-Unoptimized cells but was undetectable in non-transfected C3A cells. Immunohistochemical staining indicated higher expression of GSTA1 in C3A-Unoptimized cells than in non-transfected C3A cells. The ability to metabolize lidocaine for C3A-Unoptimized cells was enhanced compared to non-transfected C3A cells (62.5% vs 30%).

CONCLUSION: The function of the C3A-Unoptimized cell line has been improved, and this cell line might be used in the bioartificial liver support system.

Alginate-encapsulated HepG2 cells in a fluidized bed bioreactor maintain function in human liver failure plasma

Alginate-encapsulated HepG2 cells cultured in microgravity have the potential to serve as the cellular component of a bioartificial liver. This study investigates their performance in normal and liver failure (LF) human plasma over 6-8 h in a fluidized bed bioreactor. After 8 days of microgravity culture, beads containing 1.5 x 10(9) cells were perfused for up to 8 h at 48 mL/min with 300 mL of plasma. After exposure to 90% LF plasma, vital dye staining showed maintained cell viability, while a 7% increase in lactate dehydrogenase activity indicated minimal cell damage. Glucose consumption, lactate production, and a 4.3-fold linear increase in alpha-fetoprotein levels were observed. Detoxificatory function was demonstrated by quantification of bilirubin conjugation, urea synthesis, and Cyp450 1A activity. These data show that in LF plasma, alginate-encapsulated HepG2 cells can maintain viability, and metabolic, synthetic, and detoxificatory activities, indicating that the system can be scaled-up to form the biological component of a bioartificial liver.

Effect of supportive extracorporeal treatment in liver transplantation recipients and advanced liver failure patients

Recently, continuous venovenous hemodiafiltration (CVVHDF) and plasmapheresis (PF) were suggested as supportive therapy options in combination with standard treatment in advanced liver failure. The aim of this study was to analyze the effects of supportive extracorporeal treatment (SET) in a group of patients with advanced hepatic failure. A total of 25 patients (7 women, 18 men; mean age, 39.3+/-15.4 years; 13 were transplant recipients [6 women, 7 men; mean age, 37.7+/-16.9 years]) were included. All patients were in hepatic coma and receiving standard coma and liver failure management when they received SET. Number of SET sessions; levels of serum blood urea nitrogen, creatinine, albumin, calcium, phosphorus, ammonia, alanine and aspartate aminotransferase, and total/conjugated bilirubin; and prothrombin times (PTT) before and after SET were recorded retrospectively. 7.7+/-7.9 SET sessions were performed. Thirteen liver transplant recipients required SET for an average of 9.7+/-8.3 days after transplantation. Serum ammonia and bilirubin levels were lower after termination of supportive therapy when compared with initial levels (p<0.0001 and p<0.005 respectively). During follow-up, hepatic encephalopathy and liver failure resolved in 11 patients, while 14 patients (7 transplant recipients) died. There was no significant difference between patients in either group except that PTT was shorter in patients who survived (p<0.01). Further analyses revealed that in surviving patients, ammonia clearance was higher (p<0.01). In patients with advanced liver failure, or liver transplants, CVVHDF and/or PF could be supportive options combined with standard treatment.

Plasma Exchange-based Plasma Recycling Dialysis System as a Potential Platform for Artificial Liver Support

We developed a plasma recycling dialysis (PRD) system based on plasma exchange (PE). In this system, rapid reduction of toxic substances and restitution of deficient essential substances are performed by PE, and subsequent blood purification is performed by dialysis between separated plasma recycled over a purification device and the patient's blood across the membrane of the plasma separator. This study was performed to demonstrate the safety and efficacy of this system. Hyperbilirubinemia was induced by ligating the bile duct in pigs, and 7 days later, only PE for 2 h (group PE) or PE for 2 h followed by PRD for 6 h (group PE + PRD) was performed. The separated plasma was recycled over anion-exchange resin through the extra fiber space of the plasma separator. The safety and efficacy of this system were evaluated based on the values of hemodynamic and laboratory parameters. Transfer from PE to PRD was completed in a few minutes. The hemodynamic status and blood cells counts were stable and hemolysis was not observed during the procedure. In the PE + PRD group, the concentrations of total bile acids continuously decreased (pretreatment, 155.5 +/- 40.6 microM; 2 h [end of PE], 76.1 +/- 14.4 microM; 8 h [end of PRD], 25.8 +/- 9.1 microM) and the value was significantly lower than in the PE group after 6 h. The total bilirubin also continuously decreased during PRD (pretreatment, 55.3 +/- 11.5 microM; 2 h [end of PE], 33.8 +/- 8.4 microM; 8 h [end of PRD], 18.6 +/- 7.7 microM) and was significantly lower than in the PE group after 4 h. No significant change was observed in other laboratory values. This PE-based PRD system allowed a swift transfer from PE to sorbent-based blood purification. The safety of this system was demonstrated and the removal of toxic substances was significant. This study confirmed the clinical utility of this system as a platform for artificial liver support.

Response of porcine hepatocytes in primary culture to plasma from severe viral hepatitis patients

AIM

To observe the effects of plasma from patients with severe viral hepatitis (SVHP) on the growth and metabolism of porcine hepatocytes and the clinical efficiency of bioartificial liver device.

METHODS

Hepatocytes were isolated from male porcines by collagenase perfusion. The synthesis of DNA and total protein, leakages of AST and LDH, changes in glutathione (GSH), catalase and morphology of porcine hepatocytes exposed to SVHP were investigated to indicate the effect of plasma from patients with severe hepatitis on the growth, injury, detoxification, and morphology of porcine hepatocytes.

RESULTS

The synthesis of DNA and protein was inhibited in the medium containing 100% SVHP compared to the controls. The leakages of LDH and AST increased in porcine hepatocytes following exposure to 100% SVHP for 5 h. The difference between 100% SVHP and 10% newborn calf serum (NCS) was significant in t-test (LDH: t = 24.552, P = 0.001; AST: t = 4.169, P = 0.014). After exposure to SVHP for 24 h, alterations in GSH status were significant (F = 2.746, P<0.05) between porcine hepatocytes in 100% SVHP and 10% NCS, but no alteration occurred in the culture medium after 48 h (F = 4.378, P<0.05). A similar profile was observed in catalase activity. Many round vacuoles were observed in porcine hepatocytes cultured in SVHP. The membranes of these cells became indistinct and almost all the cells died on d 5.

CONCLUSION

Plasma from patients with severe hepatitis inhibits the growth, injures membrane, disturbs GSH homeostasis and induces morphological changes of porcine hepatocytes. It is suggested that SVHP should be pretreated to reduce the toxin load and improve the performance of porcine hepatocytes in extracorporeal liver-support devices.

Ratio of circulating follistatin and activin A reflects the severity of acute liver injury and prognosis in patients with acute liver failure

BACKGROUND AND AIM

The activin A-follistatin system is known to play a critical role in hepatocyte regeneration during the repair of liver tissue. However, the relationship between blood levels of these compounds and the severity and prognosis of acute liver injury remains unclear. The aim of this study was to evaluate the clinical significance of circulating activin A and follistatin in patients with acute liver disease.

METHODS

Serum activin A and plasma follistatin levels were determined on admission by enzyme-linked immunosorbent assay in 32 patients with acute hepatitis (AH), 23 patients with acute severe hepatitis (ASH) and 16 patients with acute liver failure (ALF).

RESULTS

Both serum activin A and plasma follistatin levels were significantly elevated in patients with ASH and ALF when compared with those in patients with AH and normal controls (NC). Although plasma follistatin levels were significantly and positively correlated with serum activin A levels (r = 0.413, P < 0.001), the follistatin and activin A (F/A) ratio showed distinct deviation from NC between AH and ALF patients. The F/A ratio in AH patients was significantly elevated when compared with NC, but was significantly reduced in ALF patients. Furthermore, the F/A ratio in non-surviving ALF patients was significantly lower than that in survivors. Levels of serum activin A and plasma follistatin were significantly and negatively correlated with prothrombin time (PT) and normotest (NT) levels, while the F/A ratio showed significant and positive correlations with PT and NT.

CONCLUSIONS

Decreased blood F/A ratio in ALF patients may be a reliable indicator of the severity of acute liver injury and prognosis in ALF.

Effects of plasma from patients with fulminant hepatic failure on function of primary rat hepatocytes in three-dimensional culture

BACKGROUND/AIM

As biotechnology continues to advance, a bioartificial liver is expected to be developed for the treatment of patients with fulminant hepatic failure (FHF) whose liver dysfunction is potentially reversible or for providing liver support as a bridge to liver transplantation. While monolayer-cultured hepatocytes rapidly lose their capacity to express many liver-specific functions over time when cultured, spherical-shaped hepatocytes in three-dimensional culture with the use of extracellular matrix components sustain long-term survival by maintaining differentiated hepatocyte functions. The aim of this study was to investigate whether sufficient functions of viable spherical-shaped hepatocytes could be maintained in plasma of patients with FHF in order to use these cells in an extracorporeal system.

METHODS

Hepatocyte functions were evaluated under monolayer or three-dimensional culture in FHF plasma.

RESULTS

Primary rat hepatocytes on poly-N-p-vinylbenzyl-D-lactonamide (PVLA) formed spheroids even in FHF plasma and maintained their spherical shapes in FHF plasma as long as in medium. Spherical-shaped hepatocytes on PVLA cultured in FHF plasma showed higher activity in albumin secretion, urea formation, and gluconeogenesis than those in normal human plasma or medium. As being cultured in medium, hepatocytes on PVLA cultured in plasma were also superior to cells on collagen in regard to albumin secretion, amino acid metabolism, and gluconeogenesis.

CONCLUSIONS

These findings demonstrated that FHF plasma is not toxic to rat hepatocyte spheroids and that hepatocyte spheroids have potential use in the development of a bioartificial liver.

Co-transplantation of encapsulated HepG2 and rat Sertoli cells improves outcome in a thioacetamide induced rat model of acute hepatic failure

Hepatocyte transplantation offers therapeutic opportunities in liver disease. Xenogeneic hepatocytes are a potential resource, but rejection presents a major problem. We combined cell encapsulation with modulation by local generation of an immunosuppressant by co-encapsulating Sertoli cells with HepG2 cells. We assessed in vitro rat leukocyte proliferative responses and HepG2 cell survival after intraperitoneal injection in rats. Empty beads, and beads containing HepG2 cells or HepG2/Sertoli cells were injected intra-peritoneally into rats and survival of implanted cells followed over 4 weeks; in some animals acute hepatic failure (AHF) using thioacetamide (TAA) was also induced. The marked proliferative response of rat leukocytes to HepG2 cells and HepG2-containing beads was reduced by Sertoli cell-conditioned medium and HepG2/Sertoli encapsulates. After intra-peritoneal transplantation, Sertoli cells co-encapsulation protected the HepG2 cells in normal and AHF animals. Combined encapsulation and locally generated immuno-suppression may be a valuable strategy in hepatocyte transplantation.

Improvement of C3A cell metabolism for usage in bioartificial liver support systems

BACKGROUND/AIMS

The use of cell lines in bioartificial liver support systems (BALSS) to treat fulminant hepatic failure (FHF) is hindered by their reduced metabolic functions, which could be further decreased by the patient's serum/plasma. Hence, the aim of this study was to (i) test the effect of the FHF serum on C3A cell metabolism; (ii) precondition the cells to improve their metabolic capacity.

METHODS

C3A cells were preconditioned in a medium developed at the University of Edinburgh (UoE) or a 10% FHF serum medium. Metabolism capacity was assessed on days 3, 7 and 10 and compared with primary porcine hepatocytes. Preconditioned-cell metabolism was reassessed after (i) passage and (ii) incubation with 10% FHF serum.

RESULTS

UoE-preconditioned cells showed time-dependent increase in gluconeogenesis (500%), ureogenesis (200%), galactose elimination (240%) albumin synthesis (250%). These results were in the same order of magnitude as the ones obtained with primary porcine hepatocytes and were further enhanced by cell passage. UoE-preconditioning prevented the decrease of metabolism induced by acute incubation with FHF serum on control C3A cells. Preconditioning with FHF serum did not improve cell metabolism.

CONCLUSIONS

Cell preconditioning with UoE-medium increases metabolic capacity and would greatly improve BALSS efficacy.

Serum from patients with fulminant hepatic failure causes hepatocyte detachment and apoptosis by a beta(1)-integrin pathway

Hepatocyte transplantation is restricted by the impaired ability of hepatocytes to engraft and survive in the damaged liver. Understanding the mechanisms that control this process will permit the development of strategies to improve engraftment. We studied changes in liver matrix during acute injury and delineated the mechanisms that perturb the successful adhesion and engraftment of hepatocytes. Collagen IV expression was increased in sinusoidal endothelium and portal tracts of fulminant hepatic failure explants, whereas there were minimal changes in the expression of fibronectin, tenascin, and laminin. Using an in vitro model of cellular adhesion, hepatocytes were cultured on collagen-coated plates and exposed to serum from patients with liver injury to ascertain their subsequent adhesion and survival. There was a rapid, temporally progressive decrease in the adhesive properties of hepatocytes exposed to such serum that occurred within 4 hours of exposure. Loss of activity of the beta1-integrin receptor, which controls adhesion to collagen, was seen to precede this loss of adhesive ability. Addition of the beta1-integrin activating antibody (TS2/16) to cells cultured with liver injury serum significantly increased their adhesion to collagen, and prevented significant apoptosis. In conclusion, we have identified an important mechanism that underpins the failure of infused hepatocytes to engraft and survive in liver injury. Pretreating cells with an activating antibody can improve their engraftment and survival, indicating that serum from patients with liver injury exerts a defined nontoxic biological effect. This finding has important implications in the future of cellular transplantation for liver and other organ diseases.

Combined twice-daily plasma exchange and continuous veno-venous hemodiafiltration for bridging severe acute liver failure

Aiming to remove the toxins produced during the course of severe hepatic failure, we combined hemodiafiltration and plasma exchange (patient plasma replaced by fresh frozen plasma in a twice-daily regimen) for treatment of five patients: two affected by primary nonfunction of a liver graft and three by fulminant hepatic failure. The simultaneous use of the two extracorporeal techniques allowed a rapid reduction in the administration of vasoactive drugs and a rapid, significant decrease in the indices of liver necrosis. Native liver functional recovery occurred in one case, and the wait for a second graft was made possible in the other four. Although it has been reported that the detoxifying efficacy of plasma exchange is optimal when the replaced volume of plasma is high, such a technique requires both long treatment times and high blood flows in the extracorporeal circuit, making it often hemodynamically intolerable. Our approach leads to replacement of smaller volumes, allowing lower blood flows that are better tolerated despite the often unstable hemodynamics of these patients. Liver transplantation and retransplantation remains the definite therapy for severe liver failure or primary nonfunction. However, the organ waiting time is unpredictable and often does not coincide with the patients' clinical needs. Thus alternative strategies must be developed until a suitable donor is found or there is spontaneous recovery. From this point of view, in our albeit limited experience, twice-daily plasma exchange combined with hemodiafiltration has proved to be an effective therapeutic approach.

Acute liver failure

Acute liver failure is a rare and life-threatening clinical syndrome following severe hepatic injury. Depending on the rapidity of its development, two distinct complications contribute to a high mortality: in hyperacute liver failure, rapid development of massive hepatic necrosis and apoptosis gives rise to severe hyperammonemia, hepatic encephalopathy and life-threatening cerebral edema. The high risk of cerebral herniation requires early listing for emergency liver transplantation. Patients with hyperacute liver failure surviving the initial episode of cerebral edema have a substantial potential for hepatic recovery. If progressive hepatic failure develops more slowly, astrocytic osmoregulation prevents cerebral herniation in most instances. Unfortunately, these patients have a small potential of hepatic regeneration and transplantation should be performed before renal failure, sepsis or multiorgan failure emerge. Experimental treatment methods including detoxification by artificial or bioartificial liver support or by stimulating hepatic regeneration are currently evaluated. Recognition of ammonia toxicity has stimulated the search for early ammonia-lowering strategies and strongly renewed the interest in dialytic therapies. Anti-apoptotic interventions are among the most promising pharmacological options for the near future.

Activin A and follistatin in acute liver failure

BACKGROUND

Liver regeneration may be impaired in acute liver failure due to either inhibition of the proliferative response or ongoing liver cell death. Activin A, a member of the TGFbeta superfamily, inhibits hepatocyte DNA synthesis and induces apoptosis.

METHODS

Levels of activin A and its binding protein follistatin in the serum of 23 patients with acute liver failure were determined by enzyme-linked immunosorbent assay.

RESULTS

Serum activin A was significantly increased in acute liver failure patients (median 2.15 ng/ml, range 0.28-6.87 ng/ml) compared to normal controls (median 0.25 ng/ml, range 0.19-0.53 ng/ml; = 10; 0.001). However, this was not linked to the final disease outcome. Higher levels of activin A were found in the serum of patients with acute liver failure due to paracetamol overdose (median 2.87 ng/ml, range 0.72-6.87 ng/ml; = 17) than in patients with acute liver failure due to non-A to E hepatitis (median 1.10 ng/ml, range 0.28-2.70 ng/ml; = 6; 0.05). Serum follistatin was also increased in acute liver failure patients (median 2.84 ng/ml, range 0.57-13.24 ng/ml) compared to normal controls (median 0.68 ng/ml, range 0.32-3.70 ng/ml; 0.01).

CONCLUSION

Serum activin A is increased in acute liver failure and could be a factor in the inhibition of liver regeneration.

Extracorporeal treatment in fulminant hepatic failure: pathophysiologic considerations

Fulminant hepatic failure is a life-threatening clinical syndrome following severe hepatic injury leading to cerebral edema and brainstem herniation. Excessive mortality can be currently reduced only by timely orthotopic liver transplantation. Due to the shortage of donor organs, a considerable proportion of patients develop irreversible neurological damage, multiorgan failure or death while waiting for transplantation. Consequently, alternatives to orthotopic liver transplantation and methods of stabilizing patients on the waiting list including extracorporeal detoxification treatment are currently investigated. Recent advances in the pathophysiology of cerebral edema have challenged some of the traditional assumptions on which many blood detoxification systems are based. This article aims to integrate pathophysiology of hepatic encephalopathy and cerebral edema into a proposed future concept of liver support.

Modulation of hepatocyte function in an immortalized human hepatocyte cell line following exposure to liver-failure plasma

For hepatocytes to function effectively in a bioartificial liver device, maintained function in the milieu of plasma from patients with liver failure will be required. We have investigated the effect of plasma obtained at plasmapheresis from patients with acute liver failure on the performance of the human hepatocyte cell line HHY41 in liver-failure plasma, normal plasma, and culture medium. Cytotoxicity of plasma, DNA synthesis by thymidine incorporation, oxidative status, and cytochrome P450 functions were assayed after a 16 h culture with normal plasma, liver-failure plasma, or culture medium. Some, but not all, samples of liver-failure plasma were deleterious to the performance of the cell line, inducing cytotoxicity and oxidative stress, with diminished DNA synthesis, protein synthesis, and cytochrome P4501A activity. Strategies to minimize the toxic effects of liver-failure plasma may improve the performance of liver cells in extracorporeal liver-support devices.

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.