Acute liver failure: targeted artificial and hepatocyte-based support of liver regeneration and reversal of multiorgan failure

Selectively targeting the AdipoR2-CaM-CaMKII-NOS3 axis by SCM-198 as a rapid-acting therapy for advanced acute liver failure

Acute liver failure (ALF) is a hepatology emergency with rapid hepatic destruction, multiple organ failures, and high mortality. Despite decades of research, established ALF has minimal therapeutic options. Here, we report that the small bioactive compound SCM-198 increases the survival of male ALF mice to 100%, even administered 24 hours after ALF establishment. We identify adiponectin receptor 2 (AdipoR2) as a selective target of SCM-198, with the AdipoR2 R335 residue being critical for the binding and signaling of SCM-198-AdipoR2 and AdipoR2 Y274 residue serving as a molecular switch for Ca2+ influx. SCM-198-AdipoR2 binding causes Ca2+ influx and elevates the phosphorylation levels of CaMKII and NOS3 in the AdipoR2-CaM-CaMKII-NOS3 complex identified in this study, rapidly inducing nitric oxide production for liver protection in murine ALF. SCM-198 also protects human ESC-derived liver organoids from APAP/TAA injuries. Thus, selectively targeting the AdipoR2-CaM-CaMKII-NOS3 axis by SCM-198 is a rapid-acting therapeutic strategy for advanced ALF.

Mesenchymal stromal cells (MSCs) and their exosome in acute liver failure (ALF): a comprehensive review

Recently, mesenchymal stromal cells (MSCs) and their derivative exosome have become a promising approach in the context of liver diseases therapy, in particular, acute liver failure (ALF). In addition to their differentiation into hepatocytes in vivo, which is partially involved in liver regeneration, MSCs support liver regeneration as a result of their appreciated competencies, such as antiapoptotic, immunomodulatory, antifibrotic, and also antioxidant attributes. Further, MSCs-secreted molecules inspire hepatocyte proliferation in vivo, facilitating damaged tissue recovery in ALF. Given these properties, various MSCs-based approaches have evolved and resulted in encouraging outcomes in ALF animal models and also displayed safety and also modest efficacy in human studies, providing a new avenue for ALF therapy. Irrespective of MSCs-derived exosome, MSCs-based strategies in ALF include administration of native MSCs, genetically modified MSCs, pretreated MSCs, MSCs delivery using biomaterials, and also MSCs in combination with and other therapeutic molecules or modalities. Herein, we will deliver an overview regarding the therapeutic effects of the MSCs and their exosomes in ALF. As well, we will discuss recent progress in preclinical and clinical studies and current challenges in MSCs-based therapies in ALF, with a special focus on in vivo reports.

GPR120 induces regulatory dendritic cells by inhibiting HK2-dependent glycolysis to alleviate fulminant hepatic failure

Fulminant hepatic failure (FHF) is a potentially fatal liver disease that is associated with intrahepatic infiltration of inflammatory cells. As the receptor of polyunsaturated long chain fatty acids, GPR120 can regulate cell differentiation, proliferation, metabolism, and immune response. However, whether GPR120 is involved in FHF remains unknown. Using Propionibacterium acnes (P. acnes)-primed, LPS-induced FHF in mice, we found that interference with GPR120 activity using pharmacological agonist attenuated the severity of the liver injury and mortality of FHF in mice, while a lack of GPR120 exacerbated the disease. GPR120 activation potently alleviated FHF and led to decreased T helper (Th) 1 cell response and expansion of regulatory T cells (Tregs). Interestingly, GPR120 agonist didn't directly target T cells, but dramatically induced a distinct population of CD11c⁺MHC II^lowCD80^lowCD86^low regulatory DCs in the livers of FHF mice. GPR120 was found to restrict HIF-1α-dependent glycolysis. The augmented HIF-1α stabilization caused by GPR120 antagonism or deletion could be attenuated by the inhibition of ERK or by the activation of AMPK. Through the analysis of the clinical FHF, we further confirmed the activation of GPR120 was negatively associated with the severity in patients. Our findings indicated that GPR120 activation has therapeutic potential in FHF. Strategies to target GPR120 using agonists or free fatty acids (FFAs) may represent a novel approach to FHF treatment.

Enhancing Filtration Rates by the use of Blood Flow around the Capillaries of Plasmafilters: An in Vitro Study

As the low clearance rate of plasmaseparation limits its use in the treatment of patients suffering from liver failure, sepsis or MOF, we intend to develop strategies for a plasmaseparation unit which increases plasmafiltration rates. Our first question focused on whether commercially available plasmaseparation filters, and in particular their membranes, are suitable for the inversion of blood and plasma compartments. This experimental study was performed using in vitro systems. Commercially available plasmafilters PF2000N (Gambro) and Plasmaflo (Asahi) were compared in both their normal operating mode with blood flow through the capillary lumen, and in the inverse mode. Inverse mode means that blood flows through the outer space of the capillaries while plasma was obtained from the lumen. Heparinised porcine blood (5 I.U./ml) was used in a heated, recirculating in vitro circuit. Our main results were that the normal use of both filter types Plasmaflo and PF2000N enabled maximal blood flows (Qb) of 200 ml/min and filtration rates (Qf) of 25–40 ml/min. Operating the filters in the inverse mode enabled Qb up to 500 ml/min and Qf up to 100 ml/min. Hemolysis, platelet counts and coagulation parameters did not differ significantly regardless of whether the normal or inverse mode was used. The tested plasmafiltration membranes appear to be suitable for use in inverse mode. Although in our experiments, hemocompatibility tests did not indicate severe problems induced by the module geometry, the development of a module specially constructed for blood flow outside of the hollow fibers appears to be necessary in order to minimise shunts and low perfusion areas.

The evolving story of macrophages in acute liver failure

Acute liver failure (ALF) remains a worldwide problem. The innate immune system acts as an important regulator of ALF. Kupffer cells (KCs), the resident macrophages in liver, play a key role in liver innate immune response. Recent researches have shown that macrophages display a remarkable plasticity and can differentiate into functionally diverse subsets. However, the dynamic polarized phenotypes and functional status of macrophages at different stage of ALF are not clear. In this paper, we present a review of evidence that KCs play a significant role in the pathogenesis of ALF, including the phenotype and functions of macrophages, signaling pathways involved in macrophage functional status and cell-crosstalks of KCs with other immune cells. More information on macrophages will promote a better understanding of the cellular molecular mechanisms of ALF and provide new insights for the development of therapeutic targets for ALF.

Dynamic tracking of stem cells in an acute liver failure model

AIM: To investigate a dual labeling technique, which would enable real-time monitoring of transplanted embryonic stem cell (ESC) kinetics, as well as long-term tracking.

METHODS: Liver damage was induced in C57/BL6 male mice (n = 40) by acetaminophen (APAP) 300 mg/kg administered intraperitoneally. Green fluorescence protein (GFP) positive C57/BL6 mouse ESCs were stained with the near-infrared fluorescent lipophilic tracer 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide (DiR) immediately before transplantation into the spleen. Each of the animals in the cell therapy group (n = 20) received 5 × 10⁶ ESCs 4 h following treatment with APAP. The control group (n = 20) received the vehicle only. The distribution and dynamics of the cells were monitored in real-time with the IVIS Lumina-2 at 30 min post transplantation, then at 3, 12, 24, 48 and 72 h, and after one and 2 wk. Immunohistochemical examination of liver tissue was used to identify expression of GFP and albumin. Plasma alanine aminotransferase (ALT) was measured as an indication of liver damage.

RESULTS: DiR-stained ESCs were easily tracked with the IVIS using the indocyanine green filter due to its high background passband with minimal background autofluorescence. The transplanted cells were confined inside the spleen at 30 min post-transplantation, gradually moved into the splenic vein, and were detectable in parts of the liver at the 3 h time-point. Within 24 h of transplantation, homing of almost 90% of cells was confirmed in the liver. On day three, however, the DiR signal started to fade out, and ex vivo IVIS imaging of different organs allowed signal detection at time-points when the signal could not be detected by in vivo imaging, and confirmed that the highest photon emission was in the liver (P < 0.0001). At 2 wk, the DiRsignal was no longer detectable in vivo; however, immunohistochemistry analysis of constitutively-expressed GFP was used to provide an insight into the distribution of the cells. GFP +ve cells were detected in tissue sections resembling hepatocytes and were dispersed throughout the hepatic parenchyma, with the presence of a larger number of GFP +ve cells incorporated within the sinusoidal endothelial lining. Very faint albumin expression was detected in the transplanted GFP +ve cells at 72 h; however at 2 wk, few cells that were positive for GFP were also strongly positive for albumin. There was a significant improvement in serum levels of ALT, albumin and bilirubin in both groups at 2 wk when compared with the 72 h time-point. In the cell therapy group, serum ALT was significantly (P = 0.016) lower and albumin (P = 0.009) was significantly higher when compared with the control group at the 2 wk time-point; however there was no difference in mortality between the two groups.

CONCLUSION: Dual labeling is an easy to use and cheap method for longitudinal monitoring of distribution, survival and engraftment of transplanted cells, and could be used for cell therapy models.

Epidemiological and clinical features of hepatitis B virus related liver failure in China

AIM: To examine the epidemiologic and clinical characteristics of hepatitis B virus (HBV) related liver failure in patients in China.

METHODS: This study was conducted with a retrospective design to examine 1066 patients with HBV-related liver failure in the southwest of China.

RESULTS: There were more male than female patients. Young and middle-aged people comprised most of the patients. Farmers and laborers comprised the largest proportion (63.09%). Han Chinese accounted for 98.12%, while minority ethnic groups only accounted for 0.88% of patients. A total of 43.47% patients had a family history of HBV-related liver failure and 56.66% patients had a history of drinking alcohol. A total of 42.59% patients with HBV-related liver failure had definite causes. With regard to the clinical manifestation of HBV-related liver failure, the symptoms were: hypodynamia, anorexia and abdominal distension. Total bilirubin (TBIL) and alanine aminotransferase (ALT) levels were altered in 46.23% of patients with evident damage of the liver. Univariate logistic regression analysis showed that the patients’ prognoses were correlated with ALT, aspartate aminotransferase, albumin, TBIL, prothrombin activity (PTA), and alpha-fetoprotein levels, and drinking alcohol, ascites, hepatorenal syndrome, infection and ≥ 2 complications. Multifactor logistic regression analysis showed that the activity of thrombinogen and the number of complications were related to the prognosis.

CONCLUSION: Alcohol influences the patients’ prognosis and condition. PTA and complications are independent factors that can be used for estimating the prognosis of HBV-related liver failure.

An overview of animal models for investigating the pathogenesis and therapeutic strategies in acute hepatic failure

Acute hepatic failure (AHF) is a severe liver injury accompanied by hepatic encephalopathy which causes multiorgan failure with an extremely high mortality rate, even if intensive care is provided. Management of severe AHF continues to be one of the most challenging problems in clinical medicine. Liver transplantation has been shown to be the most effective therapy, but the procedure is limited by shortage of donor organs. Although a number of clinical trials testing different liver assist devices are under way, these systems alone have no significant effect on patient survival and are only regarded as a useful approach to bridge patients with AHF to liver transplantation. As a result, reproducible experimental animal models resembling the clinical conditions are still needed. The three main approaches used to create an animal model for AHF are: surgical procedures, toxic liver injury and infective procedures. Most common models are based on surgical techniques (total/partial hepatectomy, complete/transient devascularization) or the use of hepatotoxic drugs (acetaminophen, galactosamine, thioacetamide, and others), and very few satisfactory viral models are available. We have recently developed a viral model of AHF by means of the inoculation of rabbits with the virus of rabbit hemorrhagic disease. This model displays biochemical and histological characteristics, and clinical features that resemble those in human AHF. In the present article an overview is given of the most widely used animal models of AHF, and their main advantages and disadvantages are reviewed.

The use of stem cells in liver disease

PURPOSE OF REVIEW

Cell transplantation to restore liver function as an alternative to whole liver transplantation has thus far not been successful in humans.

RECENT FINDINGS

Adult mature hepatocytes and various populations of liver progenitors and stem cells are being studied for their regenerative capabilities. Hepatocyte transplantation to treat metabolic deficiencies has shown promising early improvement in liver function; however, long-term success has not been achieved. Liver progenitor cells can now be identified and were shown to be capable to differentiate into a hepatocyte-like phenotype. Despite evidence of mesenchymal stem cell fusion in animal models of liver regeneration, encouraging results were seen in a small group of patients receiving autologous transplantation of CD133 mesenchymal stem cells to repopulate the liver after extensive hepatectomy for liver masses. Ethical issues, availability, potential rejection and limited understanding of the totipotent capabilities of embryonic stem cells are the limitations that prevent their use for restoration of liver function. The effectiveness of embryonic stem cells to support liver function has been proven with their application in the bioartificial liver model in rodents.

SUMMARY

There is ongoing research to restore liver function in cell biology, animal models and clinical trials using mature hepatocytes, liver progenitor cells, mesenchymal stem cells and embryonic stem cells.

Effects of bone marrow and hepatocyte transplantation on liver injury

BACKGROUND

The therapeutic effects of bone marrow and hepatocyte transplantation were investigated regarding the treatment of retrorsine-partial hepatectomy-induced liver injury.

METHODS

Analbuminemic F344alb rats were given two doses of retrorsine 2 wk apart, followed 4 wk later by transplantation with F344 rat bone marrow cells or hepatocytes immediately after a two-thirds hepatectomy. The survival rate, liver regeneration rate, liver functions, albumin-positive hepatocytes, and normal albumin gene sequences in the liver and serum albumin levels were investigated in the recipients.

RESULTS

Although 65% retrorsine/partial hepatectomy-treated F344alb died between 1 and 11 d after the partial hepatectomy, only 27.5% of the animals died following bone marrow transplantation, and 50% with hepatocyte transplantation. Both bone marrow and hepatocyte transplantation ameliorated acute liver injury after a partial hepatectomy. Bone marrow transplantation yielded a very small increase in the number of albumin-positive hepatocytes in the liver, while hepatocyte transplantation resulted in massive replacement of the liver tissues by the donor hepatocytes associated with an elevation of serum albumin after an extended time.

CONCLUSIONS

Both bone marrow and hepatocyte transplantation could prevent acute hepatic injury, conceivably due to a paracrine mechanism.

Early renal replacement therapy in patients with postoperative acute liver failure associated with acute renal failure: effect on postoperative outcomes

BACKGROUND

Acute liver failure after major surgical procedures is associated with a high risk of multiple organ failure, including acute renal failure. The optimal time to initiate renal replacement therapy for acute renal failure is controversial because of the poor overall clinical outcomes.

STUDY DESIGN

From July 2002 to January 2005, all patients who had no history of liver disease, but developed acute liver failure and subsequent renal failure requiring renal replacement therapy after major surgery, at a surgical intensive care unit, were retrospectively analyzed. Patients were divided into early or late dialysis groups based on an arbitrary blood urea nitrogen cut-off level of 80 mg/dL before renal replacement therapy.

RESULTS

Eighty consecutive patients (21 women), with a mean age of 57.8+/-17.0 (SD) years, comprised the study group. The late dialysis group (n=26) had a higher ICU mortality rate (p=0.02) and a lower renal function recovery rate (p=0.02) than the early dialysis group (n=54). Fifty-three (66.3%) patients died during their ICU stay. Independent risk factors for ICU mortality were renal replacement therapy modality (intermittent hemodialysis versus continuous venous-venous hemofiltration; odds ratio [OR]=4.32, 95% CI 1.26 to 14.79; p=0.02), predialysis APACHE II score> 20 (OR=6.52, 95% CI 1.61 to 26.36; p < 0.01), and late dialysis (OR=4.01, 95% CI 1.05 to 15.27; p=0.04).

CONCLUSIONS

The mortality rate in postoperative patients with acute liver failure-associated acute renal failure was very high. Earlier initiation of renal replacement therapy, based on the predialysis blood urea nitrogen level, with continuous venous-venous hemofiltration might provide a better ICU survival rate.

Comparison scoring model of severe viral hepatitis and model of end stage liver disease for the prognosis of patients with liver failure in China

AIM: To estimate the prognosis of patients with liver failure using a scoring model of severe viral hepatitis (SMSVH) and a model of end stage liver disease (MELD) to provide a scientific basis for clinical decision of treatment.

METHODS: One hundred and twenty patients with liver failure due to severe viral hepatitis were investigated with SMSVH established. Patients with acute, subacute, and chronic liver failure were 40, 46 and 34, respectively. The follow-up time was 6 mo. The survival rates of patients with liver failure in 2 wk, 4 wk, 3 mo and 6 mo were estimated with Kaplan-Meier method. Comparison between SMSVH and MELD was made using ROC statistic analysis.

RESULTS: The survival curves of group A (at low risk, SMSVH score ≤ 4) and group B (at high risk, SMSVH score ≥ 5) were significantly different (The 4-wk, 3-mo, 6-mo survival rates were 94.59%, 54.05%, 43.24% in group A, and 51.81%, 20.48%, 12.05% in group B, respectively, P < 0.001). The survival curves of group C (SMSVH scores unchanged or increased), group D (SMSVH scores decreased by 1) and group E (SMSVH scores decreased by 2 or more) were significantly different .The survival rates of groups C, D and E were 66.15%, 100%, 100% in 2-wk; 40.0%, 91.18%, 100% in 4-wk; 0%, 58.82%, 80.95% in 3-mo and 0%, 38.24%, 61.90% in 6-mo, respectively, P < 0.001). The area under the ROC curve (AUC) of SMSVH scores at baseline and after 2 wk of therapy was significantly higher than that under the ROC curve of MELD scores (0.804 and 0.934 vs 0.689, P < 0.001).

CONCLUSION: SMSVH is superior to MELD in the estimation of the prognosis of patients with severe viral hepatitis within 6 mo. SMSVH may be regarded as a criterion for estimation of the efficacy of medical treatment and the decision of clinical treatment.

Continuously Microscopically Observed and Process-Controlled Cell Culture Within the SlideReactor: Proof of a New Concept for Cell Characterization

Certain cell types, especially primary human cells, favor a well-defined culture environment offering continuous supply of nutrients and oxygen and waste product removal. Several bioreactors based on special matrices or hollow fibers have been developed that provide such conditions. However, characterization of matrix re-organization or growth of tissue within these systems is possible only after culture termination. Evaluation of the influence of certain medium additives or culture conditions (e.g., temperature, oxygenation) on cell viability, expansion, and differentiation within these systems remains a challenging task. The SlideReactor, a miniaturized hollow fiber-based bioreactor, was developed to enable the observation of cells during culture. An operation concept offering predefined conditions for various cell types has been designed. For proof of concept, primary human cells (hepatocytes, fibroblasts, keratinocytes) and cell lines (HepG2, HuH7, C3A, WiDr, SkHep1) were cultured and observed. A series of experiments (n=40) showed the feasibility of the set-up; determination of process parameters and continuous observation is possible. The SlideReactor may serve as a simple and cost-efficient tool for cell characterization and optimization of cell-culture conditions.

Improved hepatocyte excretory function by immediate presentation of polarity cues

Liver tissue constructs with excretory function are crucial to developing realistic hepatocyte models for engineering effective bioartificial liver-assisted devices and for modeling the in vivo tissue. Current hepatocyte in vitro models suffer from limited or inefficient hepatocyte repolarization, which results in poor removal of xenobiotics and other waste products from the cells. We hypothesized that the temporal and spatial presentation of the cell matrix and cell-cell contacts as polarity cues would be important to define the axis of polarization to improve the excretory function of hepatocytes. The spatial presentation of polarity cues can be best achieved with sandwich configuration. We improve the temporal presentation of polarity cues by introducing the collagen overlay immediately in synchrony with cell-cell contacts instead of after 24 h in conventional sandwich culture. We demonstrate that the immediate presentation of the collagen matrix overlay enhances the formation of apicobasolateral domains, tight junctions, and the recovery of the functional activity of 2 canalicular transporters, the multidrug resistance-associated protein (Mrp2) and P-glycoprotein (P-gp) at 48 h of culture, and enhances the albumin secretion, urea production, and 7-ethoxyresorufin-O-deethylation cytochrome P450 activities of hepatocytes over 14 days of culture as compared to the 24-h overlay controls. The improvement in the excretory function of hepatocytes for the removal of waste products deleterious to cells may improve the functional maintenance and the in vivo fidelity of tissue-engineered liver constructs.

Understanding and managing HELLP syndrome: the integral role of aggressive glucocorticoids for mother and child

Antepartum or postpartum HELLP syndrome constitutes an obstetric emergency that requires expert knowledge and management skills. The insidious and variable nature of disease presentation and progression challenges the clinician and complicates consensus on universally accepted diagnostic and classification criteria. A critical review of published research about this variant form of severe preeclampsia, focused primarily on what is known about the pathogenesis of this disorder as it relates to patient experience with corticosteroids for its management, leads to the conclusion that there is maternal-fetal benefit realized when potent glucocorticoids are aggressively used for its treatment. Although acknowledging the need for definitive multicenter trials to better define the limits of benefit and the presence of any maternal or fetal risk, and given an understanding of the nature of the disorder with its potential to cause considerable maternal morbidity and mortality, we recommend for the present that aggressively used potent glucocorticoids constitute the cornerstone of management for patients considered to have HELLP syndrome.

New management options for end-stage chronic liver disease and acute liver failure: potential for pediatric patients

The management of children with end-stage chronic liver disease and acute liver failure mandates a multidisciplinary approach and intense monitoring. In recent years, considerable progress has been made in developing specific and supportive medical measures, but studies and publications have mainly concerned adult patients. Therapeutic approaches to complications of end-stage chronic liver disease and acute liver failure (e.g. refractory ascites, hepatorenal syndrome, encephalopathy, and cerebral edema) that may be applied to children are reviewed in this article.Mild-to-moderate ascites should be managed by modest salt restriction and oral diuretic therapy in the first instance. Large volume paracentesis associated with colloid volume expansion and diuretic therapy may be effective for acute relief. Treatment of hepatorenal syndrome type 1 with vasopressin analogs (terlipressin) is recommended prior to liver transplantation in order to improve renal function. Prevention and treatment of chronic hepatic encephalopathy are directed primarily at controlling the events that may precipitate hepatic encephalopathy and at reducing ammonia generation and increasing its detoxification or removal. In addition to reduction of gut ammonia production using non-absorbable disaccharides such as lactulose and/or antibacterials such as neomycin, sodium benzoate may be used on a long-term basis to prevent, stabilize, or improve hepatic encephalopathy. The management of hepatic encephalopathy in acute liver failure is considerably more unsatisfactory; treatment is aimed at preventing brain edema and intracranial hypertension. Extracorporeal liver support devices are now used commonly in critically ill children with acute renal failure, advanced hepatic encephalopathy, cerebral edema, intracranial hypertension, and severe coagulopathy. Continuous renal replacement therapy could potentially help support patients until liver transplantation is performed or liver regeneration occurs. The Molecular Adsorbent Recirculating System (MARS or albumin dialysis) is the liver support system most frequently used worldwide in adults and appears to offer distinct advantages over hepatocyte-based systems. There are no specific medical therapies or devices that can correct all of the functions of the liver. Apart from a few metabolic diseases presenting with severe liver dysfunction for which specific medical therapies may preclude the need for liver transplantation, liver transplantation still remains the only definitive therapy in most instances of end-stage chronic liver disease and acute liver failure. Future research should focus on gaining a better understanding of the mechanisms responsible for liver cell death and liver regeneration, as well as developments in hepatocyte transplantation and liver-directed gene therapy.

THIS ARTICLE HAS BEEN RETRACTED: An Australian Experience With the Molecular Adsorbents Recirculating System (MARS)

The molecular adsorbents recirculating system (MARS) is a form of artificial extracorporeal liver support which has the potential to remove substantial quantities of albumin-bound toxins postulated to contribute to the pathogenesis of liver cell damage, hemodynamic instability and multi-organ failure in patients with acute liver failure and acute-on-chronic liver failure (AoCLF). We assessed the efficacy of MARS therapy in a cohort of patients with severe liver damage unresponsive to intensive medical therapy. MARS therapy was instituted late in the clinical course of six patients with severely impaired liver function refractory to intensive medical therapy, including four with AoCLF precipitated by sepsis and two with liver dysfunction due to sepsis in the absence of pre-existing chronic liver disease. Outcome measures included markers of hemodynamic stability, renal function, serum bilirubin and bile acid levels, arterial ammonia levels, the arterial ketone body (acetoacetate/beta-hydroxybutyrate) ratio, hepatic encephalopathy grade and the plasma disappearance rate of indocyanine green. The rates of discharge from the intensive care unit and in-hospital mortality were determined. Our findings suggest that MARS treatment might be associated with some clinical efficacy even in patients with advanced multi-organ dysfunction occurring in the setting of severe liver damage and in whom treatment is instituted late in the clinical course. However, the overall survival rate (1/6; 17%) was poor. More data obtained from larger cohorts of patients enrolled in randomized controlled studies will be required in order to identify categories of liver failure patients who might benefit most from MARS treatment and to ascertain the most appropriate timing of intervention.

Acute liver failure: from bench to bedside

Acute liver failure constitutes a challenge to clinicians and scientists alike. The course of the disease, usually unpredictable and polarizing, is associated with a high mortality unless liver transplantation is feasible, but can end in a spontaneous restitution. It poses many scientific questions regarding the mechanisms of liver cell damage and regeneration and the possibility of new therapeutic approaches. However, the performance of clinical studies in patients in acute liver failure presents problems because of the varied etiology, the small number of cases, and furthermore due to ethical and logistical difficulties. For this reason experimental investigations have gained a special importance. Arising from the improved understanding of the mechanisms of liver cell damage in acute liver failure, which may be primarily due not to the initial noxious agent alone but may also be triggered secondarily by the release of proinflammatory mediators, there are numerous options for liver cell protection, some of which have already proved successful in experimental studies. New insights into the mechanisms of regulation of liver regeneration and the physiological liver mass, gathered in particular from experimental models of partial hepatectomy and by the use of gene-manipulated animals, have contributed to the development of new therapeutic approaches for the stimulation of liver cell regeneration. Temporary liver support systems have already been successfully employed in some cases under clinical conditions. Although the systematic experimental investigation of many of the questions of acute liver failure has significantly contributed to a better understanding of liver cell damage and regeneration, the application of this new knowledge to clinical practice is to some extent made difficult by the artificial simplification that experimental studies inevitably entail and needs to be validated by controlled clinical studies.

Mathematical Model of Binding of Albumin—Bilirubin Complex to the Surface of Carbon Pyropolymer

We proposed a mathematical model and estimated the parameters of adsorption of albumin-bilirubin complex to the surface of carbon pyropolymer. Design data corresponded to the results of experimental studies. Our findings indicate that modeling of this process should take into account fractal properties of the surface of carbon pyropolymer.

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.

Combined human growth hormone and lactulose for prevention and treatment of multiple organ dysfunction in patients with severe chronic hepatitis B

AIM: To evaluate the efficiency and safety of combined recombinant human growth hormone (rhGH) and lactulose for treatment and/or prevention of multiple organ dysfunction in patients with chronic severe hepatitis B.

METHODS: Forty-eight inpatients with chronic severe hepatitis B were randomly divided into rhGH group (n = 28) and control group (n = 20). In rhGH group, 4-4.5 IU of rhGH was injected intramuscularly once daily for 2-4 wk, and 100 mL of enema containing 30 mL of lactulose, 2 g of metronidazole and 0.9% saline was administered every 2 d for 2-4 wk. Their symptoms and complications were noted. Liver and kidney functions were analyzed by an Olympus analyzer. Serum GH, IGF-1, IGFBP1 and IGFBP3 were measured by ELISA.

RESULTS: Clinical symptoms of 90% of these patients in rhGH group were obviously improved. The total effectiveness in rhGH group was better than that in control group (75% vs 40%, P<0.05). After 2- and 4-wk treatment of rhGH respectively, serum albumin (26.1±4.1 vs 30.2±5.3, 31.9±5.1 g/L), prealbumin (79.6±28.0 vs 106.6±54.4, 108.4±55.0 g/L), cholesterol (76.3±16.7 vs 85.6±32.3, 96.1±38.7 mg/dL), and IGFBP1 (56.8±47.2 vs 89.7±50.3 ng/mL after 2 wk) were significantly increased compared to control group (P<0.05). However, serum GH was decreased. The increase of serum IGF1 and IGFBP3 after rhGH treatment was also observed.

CONCLUSION: rhGH in combination with lactulose may be beneficial to the prevention and treatment of multiple organ dysfunction in patients with chronic severe hepatitis.

Amelioration of microcirculatory damage by an endothelin A receptor antagonist in a rat model of reversible acute liver failure

BACKGROUND/AIMS

Hepatocellular damage in acute liver failure (ALF) is aggravated by proinflammatory and cytotoxic mediators released from sinusoidal-lining cells. We studied a selective endothelin A receptor (ETAR) antagonist for its potential influence on the microcirculation in the setting of ALF.

METHODS

Seventy Wistar rats were divided into five groups: (I) induction of ALF by a 70% liver resection combined with injection of 400 microg/kg endotoxin, (II) ALF treated with the ETAR antagonist LU 135252 (1 mg/kg b.w. i.v.), (III) sham operation, (IV) injection of endotoxin, (V) 70% liver resection. Liver microcirculation was measured by intravital microscopy. Parenchymal injury, growth fractions, endothelin (ET)-1 and ETAR were studied by histology and immunohistology. Survival, liver function, and morphology were followed up to 14 days.

RESULTS

100% mortality, impaired liver function, widespread endothelial lesions, highest ET-1 and ETAR levels, a decreased perfusion rate, reduced sinusoidal diameter, as well as an increase in both leukocyte-endothelium interactions and sinusoidal blood flow were observed after induction of ALF. ETAR antagonist-treated rats showed decreased ET-1 and ETAR levels as well as improved microcirculatory function, morphology, liver function, and 85% survival.

CONCLUSIONS

Microcirculatory disturbances correlate with liver dysfunction in ALF. ETAR blockade represents a new therapeutic approach to ALF by reducing microcirculatory lesions and their sequelae.

Pathogenic molecular mechanisms in an animal model of fulminant hepatic failure: rabbit hemorrhagic viral disease

In this study we sought to determine whether molecular mechanisms involved in the pathogenesis of fulminant hepatic failure are present in rabbits experimentally infected with rabbit hemorrhagic disease virus (RHDV). The activities of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, as well as bilirubin concentration, were found to be significantly increased 36 hours after infection. Infected animals also demonstrated significant decreases in factor VII activity, in the Fischer index, and in the deterioration of prothrombin time. The concentration of reduced glutathione was significantly decreased 36 hours after infection, and we noted a marked increase in the ratio of oxidized to reduced glutathione. Infected animals showed progressive decreases in liver activity of the antioxidant enzyme superoxide dismutase. Expression of hepatocyte growth factor and c-met was found to be progressively reduced from 24 hours after infection, during which time we detected no modification in messenger RNA (mRNA) levels of transforming growth factor (TGF)-alpha. TFG-beta 1 was overexpressed 24 and 36 hours after infection, and 36 hours after infection we detected a significant increase in TNF-alpha mRNA levels. Experimental RHDV infection also induced marked activation of nuclear factor-kappaB and a significant increase in inducible nitric oxide synthase mRNA levels from 24 hours after infection. Data obtained from this animal model support its usefulness in the investigation of potential novel therapeutical modalities aimed at neutralizing reactive oxygen species and hepatocyte growth inhibitors or enhancing hepatocyte responsiveness to mitogens.

Equipment review: the molecular adsorbents recirculating system (MARS)

The molecular adsorbents recirculating system (MARS^®) is a form of artificial liver support that has the potential to remove substantial quantities of albumin-bound toxins that have been postulated to contribute to the pathogenesis of liver cell damage, haemodynamic instability and multi-organ failure in patients with acute liver failure (ALF) and acute-on-chronic liver failure (AoCLF). These toxins include fatty acids, bile acids, tryptophan, bilirubin, aromatic amino acids and nitric oxide. Data from controlled clinical trials are limited so far. One of two studies performed on small numbers of patients with AoCLF suggest a survival benefit, but no controlled data are available in the ALF setting. Our preliminary experience with MARS therapy, instituted late in the clinical course of five patients with severely impaired liver function, including three with AoCLF precipitated by sepsis and two with liver dysfunction due to sepsis in the absence of pre-existing chronic liver disease, indicates some clinical efficacy. However, the overall survival rate (1 of 5; 20%) remained poor. More data obtained from larger cohorts of patients enrolled in randomised controlled studies will be required in both the AoCLF and ALF settings to identify categories of liver failure patients who might benefit most from MARS treatment, to ascertain the most appropriate timing of intervention and to determine the overall impact on outcome, including cost-effectiveness.

In vitro comparison of the molecular adsorbent recirculation system (MARS) and single-pass albumin dialysis (SPAD)

The detoxification capacities of single-pass albumin dialysis (SPAD), the molecular adsorbents recirculation system, (MARS) and continuous veno-venous hemodiafiltration (CVVHDF) were compared in vitro. In each experiment 4,100 mL of toxin-loaded human plasma was processed for 6.5 hours. MARS treatment (n = 6) was undertaken in combination with CVVHDF. For SPAD (n = 6) and CVVHDF (n = 6) a high-flux hollow fiber hemodiafilter (identical to the MARS filter) was used. Levels of ammonia, urea, creatinine, bilirubin, and bile acids were determined. Concentrations before and after application of detoxification procedures were expressed as differences and were compared using the Kruskal-Wallis test. Post hoc comparisons for pairs of groups were adjusted according to Bonferroni-Holm. Time, group, and interaction effects were tested using the nonparametric ANOVA model for repeated measurements. SPAD and CVVHDF induced a significantly greater reduction of ammonia levels than MARS. No significant differences were found among SPAD, MARS, and CVVHDF with respect to other water-soluble substances. SPAD induced a significantly greater reduction in bilirubin levels than MARS. Reductions in bile acid levels were similar for SPAD and MARS. When operating MARS in continuous veno-venous hemodialysis mode, as recommended by the manufacturer, no significant differences in the removal of bilirubin, bile acids, urea, and creatinine were found. However, MARS in continuous veno-venous hemodialysis mode was significantly less efficient in removing ammonia than MARS in CVVHDF mode. In conclusion, the detoxification capacity of SPAD is similar to or even greater than that of MARS.

Extracorporeal albumin dialysis in patients with Amanita phalloides poisoning

BACKGROUND

Ingestion of Amanita phalloides is the most common cause of lethal mushroom poisoning. The relative late onset of symptoms is a distinct diagnostic feature of Amanita intoxication and also the main reason of failure for extracorporeal removal of Amanita-specific toxins from the gut and circulation.

PATIENTS AND METHODS

Extracorporeal albumin dialysis (ECAD) has been used on six consecutive patients admitted after A. phalloides poisoning with acute liver failure (ALF).

RESULTS

Six patients, with mean age of 46 years (range: 9-70 years), underwent one to three ECAD treatments. The mean time from mushroom ingestion until the first ECAD treatment was 76 h. Two patients regenerated spontaneously under ECAD treatment and orthotopic liver transplantation (OLT) could be avoided. Two patients were successfully bridged to OLT and one patient died because of cerebral herniation. One patient was treated with ECAD immediately after OLT because of the graft dysfunction and survived without re-transplantation.

CONCLUSION

ECAD appeared to be a successful treatment perspective in supporting liver regeneration or in sufficient bridging to OLT and also in treatment of graft dysfunction after OLT in patients with A. phalloides poisoning.

Fulminant hepatic failure

Fulminant hepatic failure is a rapidly progressive and often fatal syndrome, and the only definitive treatment is liver transplantation. However, given the scarcity of available grafts, the mainstay of therapy remains supportive care until there is spontaneous recovery or until a suitable donor liver becomes available. After initial assessment and stabilization, patients should be transferred to the nearest liver transplant center as soon as possible, as they can deteriorate rapidly. All patients with fulminant hepatic failure must be monitored closely and treated for hepatic encephalopathy, coagulopathy, gastrointestinal bleeding, renal failure, cerebral edema, and metabolic derangement.

Hepatic stimulator substance administration ameliorates liver regeneration in an animal model of fulminant hepatic failure and encephalopathy

AIMS/BACKGROUND

Hepatic stimulator substance (HSS) is a liver-specific growth factor implicated in hepatocellular proliferation and hepatoprotection in models of acute liver injury. In the present study, we examined the effect of exogenous HSS administration on liver proliferating capacity and survival outcome in an experimental animal model of fulminant hepatic failure (FHF) and encephalopathy, induced by repeated injections of thioacetamide (TAA) in rats.

METHODS

Fulminant hepatic failure was induced in adult male Wistar rats by three consecutive intraperitoneal injections of TAA (400 mg/kg of body weight), at 24 h time intervals. The animals received intraperitoneally either a saline solution or HSS (50 mg protein/kg of body weight), 2 h after the second and third TAA injections. The animals were killed at 6, 12 and 18 h post the last injection of TAA.

RESULTS

Levels of liver enzymes and urea in serum, blood ammonia values, liver histology, stage of hepatic encephalopathy and survival were statistically significantly improved in TAA-intoxicated and HSS-treated rats compared to TAA-intoxicated and saline-treated ones. Furthermore, HSS ameliorated liver regenerative indices--DNA biosynthesis, thymidine kinase activity and hepatocyte mitotic activity--in a statistically significant manner.

CONCLUSIONS

Our data suggest the beneficial effect of HSS administration in this animal model of FHF and encephalopathy, supporting evidence for a possible use of HSS as supportive therapy, by increasing hepatocellular proliferation, in management of FHF.

Artificial liver support in the third millennium

Analogous to the artificial kidney there is a need for an effective and safe liver support system to bridge patients with hepatic failure to liver transplantation or own liver regeneration. An overview is given of the biological and non-biological systems used in clinical practice in the past and at present. The conclusion is drawn that only the biological systems might have the potential to prolong life significantly in patients with acute liver failure. The systems with this potential are summarised. Both in Europe and the USA good bioreactors are available. Most of them are based on porcine hepatocytes, which have immunological and zoonotic drawbacks. What is missing is the well differentiated human hepatocyte in sufficient amounts. Successful development of this cell will be the crown on bioartificial liver research in the third millenium.

[Fulminant hepatitis B]

Fulminant hepatitis, or fulminant hepatic failure, is defined as a clinical syndrome of severe liver function impairment, which causes hepatic coma and the decrease in synthesizing capacity of liver, and develops within eight weeks of the onset of hepatitis. Several independent factors influence the survival of patients: age, the cause of liver disease, the degree and the duration of encephalopathy in relation to the onset of the disease, and the prevention of complications. Over the years many intensive treatments have been practiced. Liver transplantation is expensive, and patients who survive transplantation require life-long immunosuppression, clinical care and complications management. Without transplantation fulminant hepatitis and hepatic failure might be completely recovered spontaneously, and the patient could expect a normal life. Two cases of fulminant B hepatitis with intensive care treatment, and their survival despite unfavorable prognosis are presented in this paper. The management of patients with fulminant hepatitis required intensive monitoring and therapeutic measures, including corticosteroids. The prognosis for survival without transplantation in fulminant hepatitis is limited by the measures of medical treatment and new specific therapeutic modalities which must be developed through basic research.

[Acute liver failure]

Acute liver failure is characterized by a dynamic clinical course associated with high mortality. The main prognostic determinant is the development of extrahepatic complications. Close monitoring is mandatory, and prophylactic measures to avoid complications should be initiated. In case of complications, early and aggressive treatment is indicated. To date, artificial liver support devices are still in the experimental phase. Liver transplantation should be considered in patients with predictors of a poor spontaneous prognosis. Therefore, a transplant center should be contacted in every case of acute liver failure.

Extracorporeal liver support by recirculating albumin dialysis: analysing the effect of the first clinically used generation of the MARSystem

Albumin dialysis with the MARSystem is used in many hospitals to support excretory hepatic function in acute or acute on chronic liver failure. Potential pathogenic albumin bound substances accumulated in excretory liver insufficiency can be removed from patients blood by dialysis against albumin solution. A specific membrane enables the selective transport of albumin bound metabolites to the albumin containing dialysate compartment, where the loaded transport albumin is cleared and regenerated at the same time by adsorption columns and a second dialyser. Between 1993 and 1995 different membranes, set-ups and components in albumin dialysis were tested and led finally to the recirculating MARSystem with a modified polysulphone based membrane (P3/5S Gambro, Hechingen) and two adsorption columns (N350 and BR 350, ASAHI Medical Ltd.), which showed the best performance at this time. This first generation of MARSystems was used clinically between 1995 and 1998 with only minor changes in 15 patients with acute (n = 1) or acute deterioration of chronic liver disease in our department until the improved next generation of MARSystems has been available (MARS set and monitor, Teraklin AG, Rostock, Germany). Changes in blood tests pre/post during 95 single MARS treatments and in clinical status over treatment period were evaluated retrospectively.

RESULTS

A significant decrease of albumin bound substances (average reduction during single MARS treatments: bilirubin -18%, bile acids -43.7%) as well as of water soluble metabolites (creatinine -32%, urea -31%) was observed. During extracorporeal therapy also a significant drop in platelets (- 15.4%) and a prolongation of activated prothrombin time (- 21%) was documented, whereas haemoglobin, WBC, electrolytes as well as transaminases and albumin were not affected significantly.

CONCLUSION

Albumin dialysis with the first generation of MARS enables the removal of albumin bound and water soluble toxins. Unwanted side-effects and changes in laboratory tests are comparable to conventional haemodialysis (drop of platelets and prolongation of coagulation tests). The elimination of albumin bound and water soluble substances was accompanied by an improvement of clinical status.

Rabbit hemorrhagic viral disease: characterization of a new animal model of fulminant liver failure

In this study we sought to characterize a novel model of fulminant liver failure (FLF) by means of experimental infection of rabbits with the rabbit hemorrhagic disease virus (RHDV). Thirty-seven 9-week-old rabbits were injected intramuscularly with 2 x 10(4) hemagglutination units of an RHDV isolate. Eighty-five percent of rabbits died 36 to 54 hours after infection. From 36 hours after infection we noted marked increases in transaminases, lactate dehydrogenase, and total bilirubin. The rabbits exhibited hypoglycemia and coagulation abnormalities, with a significant decrease in factor V, factor VII, and prothrombin. Plasma aromatic amino acids and taurine showed progressive increases, and the Fischer index was significantly reduced. Expression of hepatocyte growth factor messenger RNA was inhibited from 36 hours after infection. Prostration and side recumbency were present at later stages, and neurologic symptoms rapidly progressed to coma. Onset of brain death was associated with a significant increase in intracranial pressure and blood ammonia. RHDV infection reproduces clinical, biochemical, and histologic features of the FLF syndrome and satisfies criteria for a suitable animal model. Rabbit hemorrhagic viral disease could provide a useful tool for the study of FLF and the evaluation of new liver-support technologies in human subjects.

Recent advances in liver transplantation

Advances in liver transplantation continue to evolve but are hampered by continued increasing shortages in donor organs. This has resulted in a high incidence of patients dying while on the United Network for Organ Sharing waiting list. Indeed, we continue to assess ways of expanding the donor pool by using marginal donors, living donor liver transplantation, split liver transplantation, domino transplantation, and hepatic support systems to prolong survival long enough for the patient to undergo liver transplantation. Changes in the liver allocation policy to reduce the number of people dying while waiting for an organ are discussed. Implementation of the model for end-stage liver disease allocation system should help alleviate the problem of increasing deaths of patients while on the waiting list. Recurrent disease, particularly recurrent hepatitis C, continues to be a major problem, and effective therapy is needed to prevent both progression of hepatitis C and recurrence in the graft and avoid retransplantation. The use of pegylated interferon in combination with ribavirin holds promise for improving the success in overcoming recurrent hepatitis C. Finally, advances in immunosuppression have reduced the incidence of acute cellular rejection and chronic rejection. However, these therapies have been fraught with metabolic complications that are now affecting quality of life and long-term survival. Tailoring immunosuppressive regimens to the individual patient is discussed.

Liver transplantation for fulminant hepatic failure

The etiology and prognosis of individuals with various forms of fulminant hepatic failure are reviewed. Special techniques of clinical management and decision making as to when and to whom to transplant in cases of fulminant hepatic failure are reviewed.

Bioartificial liver support anno 2001

Despite maximal intensive care, mortality of acute fulminant hepatic failure is high: 60%-75% in several studies. In addition patients with chronic liver insufficiency suffer from a bad quality of life: all patients suffer from fatigue; symptoms of hepatic encephalopathy, jaundice, and itching are often present. Analogous to artificial kidney treatment in patients with renal failure, an artificial liver assist device is needed not only to bridge patients with fulminant hepatic failure to liver transplantation or own liver regeneration, but also to improve the quality of life of patients with chronic liver insufficiency. Several modalities of artificial liver support are under investigation, like plasma exchange, haemodialysis, haemadsorption, albumin dialysis, liver cell transplantation, and the bioartificial liver. Artificial livers based on only supportive detoxification function do not show significant improvement of survival in controlled studies. Bioartificial liver support systems have also the potential to support hepatic synthetic functions. Bioreactors can be charged with freshly isolated or cryopreserved porcine hepatocytes, but also by human hepatoma cell lines. Several uncontrolled studies in humans show safety of such a treatment, even by using porcine cells. Transmission of porcine endogenous retrovirus to recipients has not been found. Furthermore, beneficial effects have been reported on symptoms of hepatic encephalopathy, on the height of intracranial pressure and on hemodynamic parameters. By using porcine cells immunological problems (e.g., serum sickness) can be expected during treatments longer than one week. However, "proof of the pudding" in the sense of improvement of survival is not yet available. The creation of a "liver dialysis unit" in the near future depends mainly on the development of well-differentiated immortalized human hepatocytes. Some progress in this field has already been obtained.

Biologic liver support: optimal cell source and mass

Hepatic support is indicated in acute liver failure (ALF) patients to foster liver regeneration, or until a liver becomes available for orthotopic liver transplantation (OLT), in primary non function of the transplanted liver, and hopefully in chronic liver disease patients affected by ALF episodes, in whom OLT is not a therapeutic option. The concept of bioartificial liver (BAL) is based on the assumption that only the hepatocytes can perform the whole spectrum of biotransformation functions, which are needed to prevent hepatic encephalopathy, coma and cerebral edema. Among others, two important issues are related to BAL development: 1) the choice of the cellular component; 2) the cell mass needed to perform an adequate BAL treatment. Primary hepatocytes, of human or animal origin, should be considered the first choice because they express highly differentiated functions. Accordingly, a minimal cell mass corresponding to 10% of a human adult liver, i.e. 150 grams of freshly isolated, > or = 90% viable hepatocytes should be used. When 4 degrees C cold-stored or cryopreserved hepatocytes are used, the cellular mass should be increased because of a drop in cell viability and function. In case of hepatoma-derived cells, cultured cell lines or engineered cells, an adequate functional cell mass should be used, expressing metabolic and biotransformation activities comparable to those of primary hepatocytes. Finally, the use of porcine hepatocytes or other animal cells in BAL devices should be presently directed only to ALF patients as a bridge treatment to OLT, because of potential transmission of animal retrovirus and prions which may potentially cause major pandemics.