Experimental study of bioartificial liver with cultured human liver cells

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Circulating immune complexes in patients with fulminant hepatic failure.

Circulating immune complexes were found in 15 of 16 patients with fulminant hepatic failure due to viral hepatitis and all of six patients who had had halothane anaesthesia; however, they were found in only five of 32 patients with paracetamol-induced hepatic necrosis. The levels of circulating immune complexes were not related to the severity of the clinical course, development of renal failure, final outcome, or severity of hypocomplementaemia. All the patients had depressed reticuloendothelial function as assessed by the clearance of 125I microaggregated albumin. These findings show that circulating immune complexes in fulminant hepatic failure are not simply a reflection of an immune response to liver antigens released as a result of the hepatic necrosis; nor are they a reflection of the failure of the reticuloendothelial system. This supports the view that circulating immune complexes are associated with immune mediated liver injury and may contribute to the process.     

The distribution of HBV, HCV and HGV among livers with fulminant hepatic failure of different aetiology

Background/Aims: The aim of the study was to assess the impact factor of HCV and HGV in fulminant hepatic failure.Methods: The 5′-untranslated regions of HCV RNA and HGV RNA and a segment of the core antigen sequence of HBV were amplified after extracting the nucleic acids from snap-frozen tissue aliquots from explanted livers of 26 consecutive patients undergoing orthotopic liver transplantation for fulminant hepatic failure preoperatively diagnosed as either autoimmune (n=2), HAV/HBV (n=8), toxic (n=4) or aetiologically unknown (n=12).Results: HCV RNA was detected in five of 26 (19.2%) livers with fulminant hepatic failure. All five HCV RNA-positive livers belonged to the group of non-toxic, non-autoimmune liver failure (n=20), three of them were found in the group of liver failure with unknown aetiology (n=12) and two in the group of HBV-associated liver failure (n=7), making an HCV incidence of 25%, 25%, and 28.6%, in the different groups, respectively. HGV RNA was detected in 10 of 17 (58.8%) explants and in all four groups of fulminant hepatic failure as defined preoperatively. HBV DNA was identified in six livers of 26 patients (23.1%) with fulminant hepatic failure. Neither HCV RNA nor HBV DNA was detected in the livers of patients with toxic or autoimmune fulminant hepatic failure.Conclusions: These results indicate that HBV and HCV, but not HGV, play an aetiologic role in fulminant hepatic failure. HCV-positive cases were concentrated either in the group of otherwise unexplained fulminant hepatic failure or in the group of HBV fulminant hepatic failure. HGV-positive cases, on the other hand, were found within all four preoperatively defined groups, indicating a role as cofactor rather than as single aetiologic agent.     

Aspects of our liver support systems using extracorporeal xenoperfusion of pig or baboon liver: review

Artificial liver support systems using xenoperfusion of pig or baboon liver have metabolic activity and there is the possibility that they could substitute for total liver functions; however, several problems have yet to be solved. In our early clinical experience, a method of cross-hemodialysis with interposed cuprophane membrane was employed in order to avoid immunological reactions in patients. Sixteen patients with hepatic failure were treated by this method. Although the coma grade was ameliorated in 65% of the patients, the ultimate survival rate was 18.9%. In this clinical trial, the indication for liver support was clarified based on hepatic mitochondrial functions. This unsatisfactory result could also be attributed to insufficient effects of the device, due to the interposed membrane, and also to damage of the supporting livers due to hyperacute xenoperfusion injury. Recent investigations in the field of xenotransplantations have shown us possibilities for controlling xenogeneic hyperacute rejection. Suppression of complement activation enabled long-term xenoperfusion of supporting livers with high metabolic activity. The administration of prostaglandin E1 or soluble complement receptor type 1, and the use of transgenic pig livers expressing human decay-accelerating factor, may be promising methods to estab-lish highly active artificial liver support systems using xenoperfusion.     

Evidence that host size determines liver size: studies in dogs receiving orthotopic liver transplants

Orthotopic liver transplantation was performed in two groups of dogs; Group I animals consisted of large dogs that served as recipients of livers obtained from smaller dogs while Group II animals consisted of dogs that received liver from donor dogs of nearly the same size. The small-for-size livers transplanted into the Group I dogs rapidly increased in size over the course of 2 weeks until they achieved a size equal to that originally present in the larger recipient dogs. In contrast, the livers transplanted into dogs of the same size as the donors underwent some degree of atrophy. In both groups of animals, plasma levels of insulin and glucagon and hepatic (graft) activities of thymidine kinase and ornithine decarboxylase were followed serially. The only difference between the two groups of animals for these measures was that the ornithine decarboxylase activity rose to a greater degree in the liver that underwent graft enlargement. These data suggest that recipient size determines, at least in part, liver graft size once it is transplanted. These data also suggest that of the parameters followed, only ornithine decarboxylase activity parallels the finding of growth of the transplanted liver.     

猪急性肝衰竭模型的建立及猪纤维介素的表达

目的 建立一个模拟人类疾病进程的猪急性肝衰竭(ALF)模型,用于ALF治疗药物的临床前安全性评价及疗效评价,检测模型中猪纤维介素(pfg12)的表达情况,为针对fg12的基因治疗提供基础和依据. 方法造模组耳静脉快速注射D-氨基半乳糖盐酸盐,剂量1.2 g/kg;对照组耳静脉快速注射5%的葡萄糖,剂量12 ml/kg.观察两组动物临床表现,肝功能指标和肝组织病理学改变,实时定量PCR检测肝组织中pfg12 mRNA表达,免疫组织化学检测肝组织中pfg12蛋白的表达.采用重复测量数据的方差分析和独立样本t检验进行统计学处理.结果 成功建立了与人在临床表现、肝脏生物化学指标、组织病理学改变相似的猪ALF模型;实时定量PCR检测结果显示造模组猪肝组织中pfg12的mRNA表达水平显著增加,与对照组比较,差异具有统计学意义(t=7.695,P＜0.05).免疫组织化学显示造模组猪肝组织中有明显的pfg12蛋白的表达,主要分布在肝细胞坏死区域的肝细胞、炎症浸润细胞、肝血窦内皮细胞及血管内皮细胞,对照组动物肝组织未见pfg12阳性着色.结论 以D-氨基半乳糖盐酸盐诱导的猪ALF模型可用于评价肝衰竭治疗药物的临床前疗效及安全性;pfg12在猪ALF动物模型的肝组织中异常高表达,提示其参与了ALF时肝细胞坏死的发生和发展过程.     

猪急性肝衰竭模型的建立及猪纤维介素的表达

目的 建立一个模拟人类疾病进程的猪急性肝衰竭(ALF)模型,用于ALF治疗药物的临床前安全性评价及疗效评价,检测模型中猪纤维介素(pfg12)的表达情况,为针对fg12的基因治疗提供基础和依据. 方法造模组耳静脉快速注射D-氨基半乳糖盐酸盐,剂量1.2 g/kg;对照组耳静脉快速注射5%的葡萄糖,剂量12 ml/kg.观察两组动物临床表现,肝功能指标和肝组织病理学改变,实时定量PCR检测肝组织中pfg12 mRNA表达,免疫组织化学检测肝组织中pfg12蛋白的表达.采用重复测量数据的方差分析和独立样本t检验进行统计学处理.结果 成功建立了与人在临床表现、肝脏生物化学指标、组织病理学改变相似的猪ALF模型;实时定量PCR检测结果显示造模组猪肝组织中pfg12的mRNA表达水平显著增加,与对照组比较,差异具有统计学意义(t=7.695,P＜0.05).免疫组织化学显示造模组猪肝组织中有明显的pfg12蛋白的表达,主要分布在肝细胞坏死区域的肝细胞、炎症浸润细胞、肝血窦内皮细胞及血管内皮细胞,对照组动物肝组织未见pfg12阳性着色.结论 以D-氨基半乳糖盐酸盐诱导的猪ALF模型可用于评价肝衰竭治疗药物的临床前疗效及安全性;pfg12在猪ALF动物模型的肝组织中异常高表达,提示其参与了ALF时肝细胞坏死的发生和发展过程.     

In vivo evaluation of a hollow fiber liver assist device

Orthotopic liver transplantation is the only effective form of therapy currently available for patients with fulminant hepatic failure (FHF). The use of an extracorporeal (EC) liver assist device (LAD) may result in improved presurgical clinical management. Alternatively, patients treated with LADs could avoid the transplantation procedure if they are able to regenerate a critical mass of hepatocytes that will sustain functional viability. In this study, the efficacy of a prototype hollow fiber LAD seeded with rabbit hepatocytes was assessed in vivo by the use of two different animal models: (1) normal rabbits injected with diazepam or lidocaine, and (2) a galactosamine (Gal)-intoxicated rabbit model of FHF. The EC LAD clearly decreased the blood levels of the two drugs and significantly generated diazepam and lidocaine metabolites indicating the maintenance of active P450 forms in the cellular component of the devices. A 6-hour EC treatment significantly increased the survival time and delayed the onset of hepatic encephalopathy (HE) in the Gal-intoxicated rabbits. Histological evaluations of postmortem livers showed greater hepatocyte regenerative activity in the animals treated with hepatocyte-seeded LADs than in the two control groups, e.g., rabbits not treated or treated with unseeded devices. These findings support the concept that a microporous hollow fiber LAD seeded with rabbit hepatocytes is able to sustain drug detoxification in vivo as well as to modify the course of FHF in a well-characterized animal model.     

体外生物人工肝支持作用的实验研究

目的 构建理想的体外人工肝支持系统，探讨其对暴发性肝衰竭的支持作用。方法 用经体外两步灌流法分离，限制贴壁技术球形聚集混合培养的人肝细胞－肝非实质细胞与中空纤维型生物反应器及由血液透析仪改装的辅助循环装置共同构建的ＥＢＬＳＳ，对门腔静脉分流加入肝血液阻断法建立的ＦＨＦ模型犬进行人工肝支持实验。结果 在平均约１０＾８肝细胞－肝非实质细胞ＥＢＬＳＳ的支持下，治疗组犬存活时间较无细胞空白循环对照组延长近     

Bioengineering of liver assist devices

Over 30 000 patients die annually in the United States from liver failure. In fulminant hepatic failure, a clinical syndrome associated with high mortality, orthotopic liver transplantation is the primary therapeutic option for patients not responding to supportive therapy. However, the persistent scarcity of donor organs has limited this therapeutic modality, resulting in a continued increase in the number of patients who die waiting for a donor liver. An extracorporeal bioartificial liver device could provide vital support to a liver failure patient until a donor liver was available or until the patient's own liver regenerated. Although it is unclear which liver‐specific functions must be provided by such a device to be effective, a constant challenge has been to obtain stable, well‐differentiated, and normally functioning hepatocytes that can be cultured at high cell densities. Many of the devices currently undergoing clinical trials are limited by designs which are prone to substrate limitations, resulting in compromised hepatocyte function. In devices that avoid substrate limitations, hepatocyte functions can be optimized, thereby leading to increased device efficiency. In this overview, the authors describe the critical issues involved in bioartificial liver development and discuss their experiences in hepatocyte culture optimization within the context of a microchannel, flat‐plate bioartificial liver device with an internal membrane oxygenator.     

Liver Transplantation Avoided in Patients With Fulminant Hepatic Failure Who Received Albumin Dialysis With the Molecular Adsorbent Recirculating System While on the Waiting List: Impact of the Duration of Therapy

Eighteen patients with fulminant hepatic failure due to various medical causes were listed for emergency liver transplantation and treated with extracorporeal albumin dialysis sessions using the molecular adsorbent recirculating system (MARS) at our center over a 74‐month period. Due to improvement of liver function, transplantation could be avoided in 9 patients (50%, 95% confidence interval 29% to 71%) who fully recovered afterwards. This improvement rate was higher than the rate of improvement in the French cohort of fulminant hepatic failure patients with similar etiologies (19.3%, 95% confidence interval 14.9% to 24.6%, P = 0.002). In our 18 patients, there were no statistically significant differences in any baseline characteristics or in the time with liver failure meeting transplant criteria between the patients who improved while waiting and those who did not. However, the patients who improved received a greater number of sessions and a longer total duration of MARS therapy (all P < 0.001). In the whole study population, a MARS therapy duration ≥15 h was significantly associated with improvement of liver function without transplantation (adjusted adds ratio [OR] 65.76, 2.48–1743.11, P = 0.01). Tolerance of therapy was acceptable. These results suggest that MARS therapy could contribute to native liver recovery and is safe in patients on the waiting list for fulminant hepatic failure. A minimum duration of therapy (≥15 h) could be necessary to expect significant liver function improvement.     

Diagnosis of Wilson's disease presenting as fulminant hepatic failure

The clinical course, results of standard laboratory tests, parameters of copper metabolism, and hepatic morphology in 9 cases (3 of our own and 6 from the literature) of Wilson's disease presenting as fulminant hepatic failure were compared with the findings in 5 cases of idiopathic fulminant hepatic failure. Patients with Wilson's disease were usually younger, and 7 of the 9 patients had Kayser-Fleischer rings. Patients with idiopathic fulminant hepatic failure had elevated 24-h urinary copper, decreased ceruloplasmin, and low or normal serum copper. Fulminant hepatic failure with Wilson's disease differed from idiopathic fulminant hepatic failure by the following biochemical findings: (a) higher copper levels in serum, urine and liver; (b) less pronounced elevations of transaminase levels; (c) higher concentrations of total bilirubin; and (d) lower hemoglobin values. Serum copper was the most useful biochemical test in diagnosing Wilson's disease before death. At autopsy, only hepatic copper concentrations clearly separated the two groups. Serial serum copper levels (antemortem) and quantitative analysis of hepatic copper (after recovery or postmortem) in patients with fulminant hepatic failure should help to exclude Wilson's disease.     

Galactose elimination capacity as a prognostic index in patients with fulminant liver failure.

In 25 patients with fulminant hepatic failure the prognostic value of a quantitative liver function test, the galactose elimination capacity, was assessed and comapred with routine liver function tests and clinical features. The galactose elimination capacity was significantly higher (P less than 0-05) in the five patients who survived than in the 20 patients who died. None of the other liver function tests, was significantly different. The values of the galactose elimination capacity overlapped considerably between survivors and non-survivors, but all patients with a galactose elimination capacity below 12-8 mumol galactose/min and kg body weight died. The disease among most patients who died having a galactose elimination capacity greater than 13 mumol ran a subacute course. It is suggested that quantitative liver function tests be included when new treatments of fulminant hepatic failure are investigated.     

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.     

Technology insight: liver support systems

Emergency orthotopic liver transplantation (OLT) is currently the only standard treatment for fulminant hepatic failure (FHF). The waiting time for transplantation can exceed a week-using a liver assist device to bridge patients with FHF to OLT might therefore decrease the mortality rate. Several liver support systems have been described, but no system has gained FDA approval or widespread clinical acceptance. Although the results of many experimental and clinical trials are encouraging, the field is still in its initial stages. Using nonbiologic liver support is based on the assumption that several toxins that cause hepatic coma can be removed from the circulation by blood or plasma sorption methods. As these toxins could be involved in many FHF complications recovery without the need for transplantation is the ultimate aim. Biologic liver support uses xenogeneic livers or hepatocytes to support the failed human liver, exploiting biological cell functions, namely detoxification, metabolism, and biosynthesis. The classical nonbiologic dialysis methods could decrease mortality in patients with acute-on-chronic liver failure, but definitive conclusions are impossible to draw because of the small number of patients studied and inadequate follow-up. Larger studies performed in specialty centers should provide conclusive data about the role of the bioartificial liver support system as a possible universal bridge to OLT. This article presents an overview of published experience with liver support systems since the 1960s.     

Clinical characteristics and prognostic indicators of drug-induced fulminant hepatic failure

BACKGROUND/AIMS: In most cases of drug-induced liver injury, it is difficult to diagnose whether these cases would progress to fulminant hepatic failure. We investigated the characteristics of non-viral and suspiciously drug-induced fulminant hepatic failure by comparing clinical data between cases that progressed and those that did not progress to fulminant hepatic failure. METHODOLOGY: Ninety-five cases of suspicious drug-induced liver injury including 22 cases that had been treated at our hospital, and subsequently progressed to fulminant hepatic failure were involved in this study. We investigated the characteristics of drug-induced fulminant hepatic failure by a comparison of non-fulminant and fulminant cases, and simultaneously of survivors and fatal cases in the group of fulminant cases. RESULTS: Many of the clinical variables were significantly deteriorated in fulminant cases. The latent period, which means the duration of drug administration, correlated with the severity of drug-induced liver injury including fulminant hepatic failure. Suspicious cases of drug-induced liver injury where the bilirubin level at the time of definite diagnosis stayed over 13 mg/dL for more than one month were likely to progress to fulminant hepatic failure. CONCLUSIONS: Our results suggest that the latent period and the peak level of total bilirubin would be prognostic factors for the severity of drug-induced fulminant hepatic failure. Early preparation of liver transplantation should be recommended by referring these characteristics.     

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.     

Adipose tissue-derived stem cells: hepatic plasticity

Currently, the only effective treatment for end-stage liver disease is liver transplantation. The number of patients on the waiting list increases considerably each year, giving rise to a wide imbalance between supply and demand for healthy livers. Knowledge of stem cells and their possible use have awakened great interest in the field of hepatology, these cells being one of the most promising short-term alternatives. Hepatic stem cell therapy consists of the implantation of healthy cells capable of performing the functions that damaged cells are unable to carry out. Recent observations indicate that several stem cells can differentiate into distinct cell lineages. Hepatic differentiation of adult stem cells from several origins has yielded highly promising results. Adipose tissue in adults contains a reservoir of stem cells that can be induced and differentiated into different types of cells, showing a high degree of plasticity. Because of its abundance and easy access, adipose tissue is a promising source of adult stem cells for hepatic stem cell therapy. The present article reviews the progress made in the differentiation of adult stem cells from adipose tissue into cells with hepatic phenotype. We also discuss the potential application of this technique as a therapy for temporary metabolic support in patients with end-stage liver failure awaiting whole organ transplantation, as a method to support liver function and facilitate regeneration of the native liver in cases of fulminant hepatic failure, and as a treatment in patients with genetic metabolic defects in vital liver functions.     

Is there a future for liver-assist devices?

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