Intracranial pressure observations in a canine model of acute liver failure supported by a bioartificial liver support system

Abstract:  Life-threatening, severely elevated intracranial pressure (ICP) is a common feature of acute liver failure (ALF). Perfusion with a bioartificial liver may serve to mitigate rising ICP. A retrospective analysis of ICP measurements in a canine ALF model prospectively supported with a bioartificial liver support system (BLSS) is presented. Animals are divided into two groups based upon care provided: (i) standard medical care ( n  = 6); and (ii) standard medical care plus BLSS support ( n  = 9). Nonparametric analysis with respect to ICP, arterial NH₃, lactate, and supportive-care parameters found BLSS-supported animals evidenced significantly less metabolic acidosis than unsupported animals. Analysis of variance/linear regression for direct dependence of ICP on arterial NH₃, lactate, and supportive care parameters irrespective of care found ICP was uncorrelated with any measured factor ( P  > 0.06 for all factors). Lack of correlation of ICP with the considered parameters indicates that none of these factors are predictive of the extent of ICP elevation in the d -galactosamine canine model. Blood chemistry and supportive care factors that are correlated with and predictive of ICP elevation remain to be identified.     

Bioartificial liver inoculated with porcine hepatocyte spheroids for treatment of canine acute liver failure model

The aim of this study was to evaluate a novel bioartificial system in a canine model of acute liver failure. An acute liver failure model in canines was induced by an end-side portocaval shunt combined with common bile duct ligation and transection. The bioartificial liver system, which utilized blood perfusion through a hollow fiber bioreactor from BIOLIV A3A inoculated with 1.0 - 3.1 x 1010 porcine hepatocyte spheroids, was developed for the treatment of acute liver failure. Sixteen acute liver failure model canines were divided between a group treated with bioartificial liver (n=8) and a control group (n=8) for 5 h. Blood alanine aminotransferase (ALT), alkaline phosphatase (AKP), total bilirubin (TBi), direct bilirubin (DBi), prothrombin time (PT), ammonia levels, and the ratio of branched chain to aromatic amino acids (Fischer's ratio) were determined. ALT, AKP, TBi, DBi, and ammonia levels were significantly elevated, PT was significantly prolonged, and Fischer's ratio decreased significantly in the canine model of the two groups on day 14 after operation compared to baseline. There were no significant differences between the two groups in laboratory data before treatment. In canines treated with the bioartificial liver system, ALT, AKP, TBi, DBi, and ammonia levels decreased significantly, PT was significantly shortened, Fischer's ratio was significantly elevated after treatment, and the survival rate by day 7 after treatment was 100%. In canines in the control group, on the other hand, there were no significant differences in ALT, AKP, TBi, DBi, PT, and ammonia levels between pretreatment and posttreatment, though these indices decreased to a slight degree after treatment. The survival rate by day 7 after treatment was 62.5% in the control group. Fischer's ratio decreased after treatment. ALT, AKP, TBi, DBi, PT, and ammonia levels in the bioartificial liver system group were lower, and Fischer's ratio and survival rate were higher than those in the control group after treatment. These results indicate that the novel bioartificial liver system we developed has a significant impact on the course of canine acute liver failure model and has potential advantages for clinical use in patients with acute liver failure.     

Evaluation of primary human liver cells in bioreactor cultures for extracorporeal liver support on the basis of urea production

Primary human liver cells from donor organs unsuitable for transplantation were cultivated in bioreactors developed for extracorporeal liver support. Because each system contains cells originating from an individual organ, each bioreactor culture must be individually characterized. The objective of this study was to identify suitable decisive parameters for the evaluation of cell culture performance. We analyzed the data from 47 bioreactor cultures containing 437 +/- 110 g of cells. Choosing urea production as the decisive parameter, the bioreactor cultures were divided into high-performance (daily urea production > or = 110 mg per bioreactor between culture days 3 and 14) and low-performance cultures. Comparing the mean courses of the groups revealed a significant distinction in most other investigated biochemical parameters. In conclusion, urea production seems to be an appropriate parameter for evaluating the performance of liver cell cultures in bioreactors because it corresponds to all other evaluated parameters of cell function.     

First clinical use of a novel bioartificial liver support system (BLSS).

The first clinical use of the Excorp Medical Bioartificial Liver Support System (BLSS) in support of a 41-year-old African-American female with fulminant hepatic failure is described. The BLSS is currently in a Phase I/II safety evaluation at the University of Pittsburgh/UPMC System. Inclusion criteria for the study are patients with acute liver failure, any etiology, presenting with encephalopathy deteriorating beyond Parson's Grade 2. The BLSS consists of a blood pump; a heat exchanger to control blood temperature; an oxygenator to control oxygenation and pH; a bioreactor; and associated pressure and flow alarm systems. Patient liver support is provided by 70-100 g of porcine liver cells housed in the hollow fiber bioreactor. The patient exhibited transient hypotension and thrombocytopenia at initiation of perfusion. The only unanticipated safety event was a lowering of patient glucose level at the onset of perfusion with the BLSS that was treatable with intravenous glucose administration. Moderate changes in blood biochemistries pre- and post perfusion are indicative of liver support being provided by the BLSS. While the initial experience with the BLSS is encouraging, completion of the Phase I/II study is required in order to more fully understand the safety aspects of the BLSS.     

体外生物人工肝系统对暴发性肝衰竭兔的支持作用

目的探讨培养肝细胞用于生物人工肝及其作为肝移植辅助支持手段的可能性。方法以培养人肝细胞和中空纤维反应器为主要材料构成体外生物人工肝系统,对Ｄ-氨基半乳糖诱导的暴发性肝衰竭（ＦＨＦ）免进行人工肝支持实验。结果尽管两组实验动物的存活时间没有明显差异,但支持治疗组兔的血清转氨酶、总胆红素和肌酐水平均低于对照组,肝组织病理检查见肝细胞坏死程度明显轻于对照组,实验所用肝细胞保持较好的活力和贴壁能力。结论所用体外生物人工肝支持系统已发挥出培养肝细胞的生物作用,能够部分代偿ＦＨＦ兔的肝脏功能。【关键词】##4人工肝;;支持;;暴发性肝衰竭;;兔     

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.     

Life support of artificial liver: development of a bioartificial liver to treat liver failure

In recent years there has been a particular focus on research regarding tissue engineering targeting the liver, especially in terms of what types of cells and extracellular matrices should be organized and in what type of environments to create an artificial liver, i.e., a life-saving organ. The ideal is to use healthy human liver cells as a source of cells for such research, but there is an extreme shortage of human-donor livers that can be used for cell isolation. Therefore, we are presently working on the differentiation of embryonic stem cells into liver cells as well as reversibly immortalized human liver cell lines that can be cultured in large quantities and at low cost. We are also working on the development of a bioartificial liver (BAL) using such cells as a source. Herein, we introduce our findings on the current status of BAL development.     

Efficacy of an extracorporeal flat-plate bioartificial liver in treating fulminant hepatic failure

BACKGROUND: Fulminant hepatic failure is associated with a high mortality rate. Orthotopic liver transplantation is the only established treatment for patients who do not respond to medical management. A major limitation of this treatment is a shortage of donor organs, resulting in many patients dying while waiting for a transplant. An extracorporeal bioartificial liver (BAL) has the potential to provide temporary support for patients with fulminant hepatic failure (FHF) and for patients awaiting orthotopic liver transplantation. We developed a flat-plate BAL with an internal membrane oxygenator in which porcine hepatocytes were cultured as a monolayer. MATERIALS AND METHODS: Twenty-four hours after cannulation of the left carotid artery and right jugular vein, FHF was induced in rats by administering 2 intraperitoneal injections of D-galactosamine (GalN) (1.2 g/kg) at a 12-h interval. The rats were connected to a BAL device 24 h after the first GalN injection and underwent extracorporeal perfusion for a duration of 10 h. Liver histology, liver-specific markers, and animal survival up to 168 h (7 days) were examined. RESULTS: Histologically, liver damage was reduced in the animal group treated with the hepatocyte-based BAL device. Significant reductions occurred in the plasma ammonia levels and prothrombin times in the group treated with the seeded BAL device. Animal survival in the group treated with the seeded BAL device was significantly higher (50.0%) than in the control animal group treated with an unseeded BAL device (11.1%). CONCLUSIONS: This flat-plate BAL with an internal membrane oxygenator and cultured porcine hepatocytes has yielded encouraging results in the treatment of rats with GalN-induced FHF.     

The bioreactor with CYP3A4- and glutamine synthetase-introduced HepG2 cells: treatment of hepatic failure dog with diazepam overdosage

A novel recombinant human hepatic cell line, CYP3A4- and glutamine synthetase (GS, an enzyme which converts ammonium ion and glutamate to glutamine)-introduced HepG2 (HepG2-GS-CYP3A4), was established. Its usefulness in a large-scale culture with a circulatory bioreactor in vitro and in dog models of ischemic hepatic failure with acute diazepam (DZP, a substrate of CYP3A4) overdosage was further examined. HepG2-GS-CYP3A4 expressed about 9 times larger amounts of CYP3A4 protein than a control. After incubation with HepG2-GS-3A4 cells in a circulatory bioreactor for 24 h, ammonia and DZP concentrations in the culture medium significantly decreased by about 40%. Furthermore, this system improved the survival time and decreased serum concentrations of DZP, ammonia, and transaminase in dogs with ischemic hepatic failure plus acute DZP overdosage. The mean survival time with bioreactor with HepG2-GS-3A4 was 42.7 +/- 3.6 h, which was significantly longer than that without reactor, with reactor (no cells), and with HepG2-GS (23.4 +/- 2.8, 22.1 +/- 2.4, and 31 +/- 3.7 h, respectively). Therefore, it is concluded that this bioartificial liver could be a good tool for the treatment of dogs with hepatic failure and that it could potentially be a bridging procedure to liver transplantation.     

Ex vivo liver perfusion with arterial blood from a pig with ischemic liver failure

To simplify liver support using an ex vivo perfused liver, an isolated pig liver was perfused with arterial blood from the recipient pig while monitoring the metabolic capacity of the ex vivo perfused liver. It was possible to perfuse the isolated liver for more than 24 h using arterial blood from a pig with ischemic liver failure. The viability of the isolated liver during support from the liver failure pig was well maintained as evidenced by the high adenylate energy charge (0.815) and a constant ketone body ratio (KBR) of over 1.0 sampled from the hepatic vein. Oxygen consumption (mean, 29.0 microl/min/g of liver) and bile production (mean, 24.2 microl/h/g of liver) were significantly higher in the isolated liver connected to the liver failure pig than in the organ connected to the pig without liver failure (15.5 microl/min/g and 7.3 microl/h/g, respectively). These findings suggest that this liver support system has sufficient metabolic capacity to support a failed liver. Further studies may provide the experimental basis necessary for the clinical application of this device in treatment of patients with acute liver failure.     

闭合型双循环生物人工肝支持系统治疗犬急性肝功能衰竭实验研究

目的探讨和评价闭合型双循环生物人工肝支持系统(CBC-BALSS)在治疗犬急性肝功能衰竭模型过程中的稳定性、安全性和有效性。方法建立犬急性肝功能衰竭模型(门腔分流联合胆总管离断),采用CBC-BALSS进行支持治疗。20只模型犬分为两组CBC-BALSS治疗组(n=11);无肝细胞CBC-BALSS对照组(n=9)。治疗时限6h。检测实验犬血氨、生化全套、凝血因子(FactorⅦ)、支/芳氨基酸(BCAA/AAA)、单乙基甘氨酸二甲苯胺(monoethylglycinexylidide,MEGX)和细胞循环路生化全套、肝细胞密度和数量。结果CBC-BALSS细胞回路细胞悬液总体积200ml,肝细胞的总数1×1010个、密度5×107/ml、活率98%左右。治疗中16只犬的生命体征平稳,在治疗30min内均出现一过性低血压;2只转流开始15min出现过敏反应;1只转流中因上消化道出血死亡;1只因穿刺部位出血死亡。模型治疗前血氨、ALT、TBil/DBil、白蛋白、FactorⅦ和BCAA/AAA分别达150mmol/L、400U/L、80/55mmol/L、35g/L、20%和1.6;CBC-BALSS治疗6h后,血氨、TBil/DBil下降均显著低于对照组;ALT存在下降趋势且在第6小时差异有统计学意义;白蛋白、FactorⅦ和BCAA/AAA在所有时段、组间差异均无统计学意义。在治疗1h和2h,MEGX差异有统计学意义,治疗组MEGX比对照组提前2h达最高点。治疗15~30min后,双循环路压力至115mmHg趋于平稳,且在±5mmHg波动。在治疗过程中,治疗组细胞循环路ALT显著性升高;组间细胞循环路TBil/DBil变化差异无统计学意义,而两组在各时间点均显著性升高;白蛋白变化无统计学意义。结论CBC-BALSS治疗犬急性肝功能衰竭过程中,安全、有效、稳定且代谢支持作用明显。     

异种肝细胞移植缓解大鼠急性肝功能衰竭及其排斥反应观察

目的探讨异种肝细胞移植对大鼠急性肝功能衰竭防治效果及其免疫排斥反应。方法将异种豚鼠肝细胞,90%肝除术前1d植入大鼠脾脏内。观察受试大鼠存活时间,及切肝术后24h血生化改变。另外观察植入肝细胞被排斥情况及受体CH50、异种抗体IgG、IgM水平变化。结果(1)中位存活时间,对照组为21h,同种组为56h,异种组为40h。同种组存活时间较对照组延长(P<0·01),异种组亦延长(P<0·05)。(2)异种组血糖和凝血酶原时间改善较明显(P<0·05),同种组谷丙转氨酶、总胆红素、血糖、凝血酶原时间都有明显改善(P<0·05或P<0·01)。(3)受体CH50和异种抗体IgM水平下降与植入异种肝细胞排斥过程同步。结论异种肝细胞移植对大鼠急性肝功能衰竭有防治作用,补体和异种抗体IgM与排斥反应关系密切。     

Efficacy of nonwoven fabric bioreactor immobilized with porcine hepatocytes for ex vivo xenogeneic perfusion treatment of liver failure in dogs

We have developed a new bioartificial liver bioreactor filled with porcine hepatocytes immobilized on polyester nonwoven fabric (NWF). In this study, we investigated the efficacy of our hybrid bioartificial liver system incorporating the NWF bioreactors and an immunoglobulin adsorbent column for perfusion treatment in a canine liver failure model. Xenogeneic perfusion treatment for operative canine liver failure models were performed for 3 h, and survival time, intracranial pressure, and blood and cerebrospinal fluid data were documented. Treatment was carried out without obstruction by immunological rejection when immunoglobulin adsorbent columns were used with the NWF bioreactors in combination. Dogs treated with this system exhibited a restricted increase of intracranial pressure and significant compensatory effects on blood and cerebrospinal amino acid imbalances as shown by a significant improvement of Fischer's ratio. On the other hand, relatively low capacity for ammonia elimination was shown as compared with homologous direct hemoperfusion.     

终末期肝病模型对肝衰竭的近期预后价值

目的探讨终末期肝病模型(model for end-stage liver disease,MELD)评分系统对急性肝衰竭患者近期预后的价值。方法检测115例急性肝衰竭患者的肝、肾功能及凝血项,计算MELD评分,并随访90d的生存率,比较存活组与死亡组MELD分值,并观察分析不同预后患者入选后30d时MELD分值的动态变化。结果 115例急性肝衰竭患者中,死亡组基线MELD分值明显高于存活组,且基线MELD分值越高,病死率越高。死亡组入选后30d的MELD分值较基线MELD分值升高,存活组入选后30d的MELD分值较基线MELD分值下降。结论 MELD评分系统可以作为预测急性肝衰竭患者预后较客观的指标。纵向评估MELD分值的动态变化可以较客观地反映急性肝衰竭的进展。     

Improved function of microencapsulated hepatocytes in a hybrid bioartificial liver support system

Conventional methods of microencapsulating isolated hepatocytes with Type I collagen matrix have provided metabolic liver support in experimental animal models of acute liver failure and congenital metabolic liver disease. We compared the biological function of transplanted microencapsulated hepatocytes cultured on standard Type I collagen (Vitrogen) and a commercially available liver basement-membrane-like extract from a mouse sarcoma (Matrigel). Isolated hepatocytes were microencapsulated with Matrigel and Vitrogen within an alginate-poly-L-lysine composite membrane. Isolated encapsulated hepatocytes (IEH) were transplanted intraperitoneally into homozygous Gunn rats that exhibit congenital hyperbilirubinemia. Control Gunn rats received empty or no microcapsules. Total serum bilirubin and conjugated bilirubin in bile were measured at weekly intervals for one month. Significant (p < 0.01) decreases in total serum bilirubin were observed in all IEH transplanted animals. No such decrease was seen in control animals. Gunn rats that received Matrigel had significantly (p < 0.05) lower serum bilirubin values and significantly (p < 0.05) higher conjugated bilirubin in bile than those that received Vitrogen. We conclude that hepatocytes microencapsulated with Matrigel functioned better than those with Vitrogen. This improved in vivo biological response underscores the importance of using the appropriate cell attachment substratum to enhance the function of a hybrid bioartificial liver support system based on transplanted hepatocytes.     

Assessment of an extracorporeal liver assist device in anhepatic dogs

We have used an anhepatic dog model to demonstrate the efficacy of a bioartificial liver assist device. Six dogs underwent total hepatectomy. Three received only medical care (controls) while the remainder were connected to an extracorporeal liver assist device (ELAD). The control dogs failed to regain consciousness after anesthesia although all lived 4-5 h postoperatively. Plasma ammonia concentration increased by an average of 250 mumol/L between the end of surgery and the demise of the animals. The treated dogs lived 3-12.5 h, and 2 of them required repeated doses of thiamylal sodium to maintain sedation. Plasma ammonia concentration was unchanged after connection to the ELAD except in the longest survivor, whose ammonia began to rise after 8 h on the ELAD. The short survival in the other 2 treated dogs was the result of uncontrolled intraabdominal bleeding. This device is capable of replacing the metabolic function of the liver, and might provide hepatic support in patients awaiting transplantation or in fulminant hepatic failure.     

Liver stem cells: a potential source of hepatocytes for the treatment of human liver disease

Severe liver injury often leads to the proliferation of oval cells, which differentiate along hepatocytic and biliary lineages. Because oval cells proliferate only when hepatocyte replication is impaired, they are considered to be the progeny of facultative liver stem cells (FLSCs). Identification and isolation of FLSCs has been hampered by the lack of markers that delineate these bipotential progenitors. We hypothesized that transition ductal cells are FLSCs because they are located in a unique anatomical niche sharing tight junctions with a neighboring hepatocyte and another terminal ductular cell. Alternatively, it has been proposed recently that bone marrow-derived stem cells are FLSCs since these cells differentiate along the hepatic lineage following colonization of the liver. The intent of this review is to provide insight into the nature and origin of liver stem cells and to explore the possibility that stem cell technology may lead to the development of clinical modalities for the treatment of human liver disease.     

终末期肝病模型评分及MELD-Na评分评估肝衰竭肝移植短期预后的对比观察

目的探讨终末期肝病模型（model for end-stage liver disease, MELD）评分与MELD-Na评分对肝衰竭患者行肝移植短期预后（3个月）的临床价值。 方法收集从2012年1月至2019年12月在中国人民解放军联勤保障部队第九〇〇医院因肝衰竭行肝移植的86例患者的术前及术中临床资料。采用受试者工作特征（ROC）曲线评价MELD和MELD-Na评分对短期预后的鉴别能力并根据Youden指数确定最佳的cut-off值。 结果86例患者中早期死亡21例（24.4%）。术前MELD评分（P=0.001）和术中输血量（P<0.001）是肝衰竭行肝移植患者早期死亡的独立危险因素。MELD和MELD-Na评分预测肝移植术后早期死亡的ROC曲线下面积分别为0.696和0.686，差异无统计学意义（P=0.677）。MELD≥24.3组、MELD<24.3组的早期生存率分别为51.7%（15/29）和87.7%（50/57），MELD-Na≥25.7组、MELD<25.7组的早期生存率分别为54.9%（17/31）和87.3%（48/55），差异均有统计学意义（P<0.001），MELD评分与MELD-Na评分升高时，早期生存率降低。 结论在预测肝衰竭行肝移植患者早期预后方面，MELD评分与MELD-Na评分预测能力无明显差异。MELD评分与术中输血量是患者早期死亡的独立危险因素。     

The relationship of systemic hemodynamics and oxygen consumption to early allograft failure after liver transplantation

The early postoperative hemodynamic data of 88 patients who underwent primary liver transplantation between July 1989 and October 1990 at the University Health Center of Pittsburgh were analyzed to establish the relationship of systemic hemodynamics and oxygen consumption to perioperative allograft function. The 15 patients whose allografts failed within the 1 st month following transplantation were designated as group 1, while 73 patients who retained adequate graft function constituted group 2. Although the cardiac index and oxygen delivery did not differ significantly between the groups, group 1 consistently demonstrated a lower mean arterial pressure, oxygen consumption, arteriovenous oxygen content difference, and arterial ketone body ratio. The etiology of reduced oxygen consumption in group 1 patients is speculative, but the data support the notion that oxygen consumption is a useful, predictive indicator for liver allograft function after transplantation.