生物人工肝系统的生物反应器

目的:介绍生物反应器的基本作用、功能、条件和要求,并对主要生物反应器的研究进展予以探讨.方法:由第一作者应用计算机检索PubMed数据库(http://www.ncbi.nlm.nih.gov/PubMed,英文)及CNKI数据库(www.cnki.net/index.htm,中文).检索时限1994-01/2009-08.中文检索关键词:生物人工肝,生物反应器,膜材料.英文检索关键词:bioartificial liver,bioreactor,membrane material.文献筛选、纳入标准:①选取针对性强,相关度高的文献.②对同一领域的文献选择近期发表或权威杂志的文献.③排除较陈旧的理论观点以及一些重复性研究.结果:计算机初检到150篇文献,阅读标题和摘要进行初筛,排除研究目的与本文无关的文献88篇,内容重复性研究32篇,共30篇文献符合标准.结果显示生物人工肝系统正在成为肝衰竭患者体外有效的肝支持治疗手段,生物反应器为肝细胞提供良好的生长代谢环境、物质交换及免疫隔离的平台,是人工肝最重要的组成部分.以纤维素半透膜为基础的生物反应器主要有平板式反应器、中空纤维型反应器,半透膜材料主要有混合纤维素酯膜、醋酸纤维素膜、铜仿膜、聚偏二氟乙烯膜、聚丙烯膜等.结论:生物反应器作为一个动态体系,伴随着生物反应器本身控制系统的优化,能够更好地控制反应器内部的传质,建立仿生物理化学梯度,实现肝细胞最小结构单元的模拟构建,膜材料的选择是构建人工肝支持系统生物反应器的首要和基础环节之一.     

生物人工肝支持系统中细胞材料的选择

学术背景:以培养肝细胞为基础的生物人工肝支持系统是治疗肝衰竭和重型肝炎的重要方法之一,装有细胞材料的生物反应器则是其重要组成部分,而理想的生物人工肝细胞材料应具备成熟肝细胞的所有功能。目的:了解近年来国内外有关生物人工肝细胞材料的研究情况和最新进展。检索策略:主要检索1994-01/2007-06美国国立图书馆网站(PUBMED)、国内全文网站康健西文生物医学期刊文献数据库和中文CHKD网站有关生物人工肝细胞材料的文献,主要为英文检索,辅以中文。关键词为人工肝(liver,artificial)和/或肝细胞(Hepatocytes),干细胞(stemcell),肝细胞系(Livercellline)和永生化肝细胞(immortalization hepatocytes)。检索到685篇文献,不采用未发表的文章。经初步筛查,排除研究目的不同及内容重复的文献,详细阅读27篇。文献评价:所选文献主要来源于Hepatology,Journal of Artificial Organs,Gastroen terology,Annals of Surgery,Tissue Engineering,Journalof Hepatology,Biomaterials等著名杂志,主要为论著。资料综合:目前国内外用于生物人工肝的细胞主要有以下几种:①成人肝实质细胞:主要体现在安全性好,细胞生物学功能相同,最大障碍是来源匮乏,活力难以长时间维持。②猪肝细胞:是生物人工肝支持装置中应用最多的细胞材料,目前已进入Ⅱ/Ⅲ期临床研究,但在使用过程中需密切注意免疫反应和内源性反转录病毒感染的问题。③肝细胞株:是重要的生物人工肝细胞材料之一,来源容易。依靠其获得方法不同,可分为肝肿瘤源性、经传代建立以及病毒转染后的细胞株。④肝干细胞:是非常有潜力的细胞材料,可分为肝源性肝干细胞和非肝源性肝干细胞。结论:目前应用于生物人工肝临床研究的肝细胞主要有猪肝细胞和肝肿瘤细胞株,各有优缺点,永生化人肝细胞、肝干细胞等能否应用于临床,仍需深入探究。     

骨髓干细胞向肝细胞分化方式的研究进展

学术背景:骨髓中的某个细胞群具有转化为卵圆细胞,并进一步分化为肝细胞和胆管上皮细胞的潜能,为修复肝脏不可逆性损伤带来了新希望.目的:对近年来骨髓干细胞向肝细胞分化的研究进行综述.检索策略:应用计算机检索PubMed 及HighWire l999-01/2007-06 期间骨髓干细胞治疗肝病文章,检索词为"bone marrow stem cells,mesenchymal stem cells,hemopoietic stem cells, hepatocytes, hepatic fibrosis, hepatic cirrhosis"等,限定语言种类为英文.同时检索维普数据库1999-01/2007-06期间骨髓干细胞治疗肝硬化及肝纤维化文章,检索词为"骨髓干细胞,间充质干细胞,造血干细胞,肝细胞,肝纤维化,肝硬化",限定语言种类为中文.对资料进行初审,并查看每篇文献后的引文.纳入标准:文章所述内容应与骨髓干细胞移植治疗肝纤维化、肝硬化的研究进展相关.排除标准:重复研究或Meta分析类文章.共收集到49篇外文文献和42篇中文文献,34篇文献符合纳入标准,排除的57篇为内容陈旧或重复文献.文献评价:符合纳入标准的34篇文献中,18篇涉及骨髓干细胞通过移植在体内转化为肝细胞,12篇涉及骨髓干细胞通过体外培养、诱导分化为肝细胞,4篇涉及存在的问题与展望.资料综合:骨髓干细胞主要包括造血干细胞和间充质干细胞, 其具有可塑性特性.体外通过生长因子,体内利用特定的微环境均可诱导骨髓干细胞分化为肝前体细胞和成熟肝细胞,并明显改善肝功能.从动物实验到临床研究都表明,骨髓干细胞具有的来源丰富、费用低廉、损伤小、自体移植不栓塞、无排斥反应等优点为治疗肝病提供了新思路,有望成为生物人工肝的细胞来源.结论:骨髓干细胞治疗肝炎、肝硬化和肝癌等难治性肝病的临床应用前景非常突出.     

分子吸附循环系统在肝移植等待期急性肝功能衰竭治疗中的作用

学术背景:肝移植是目前治疗肝功能衰竭的有效手段,但此法受到了急性肝功能衰竭发病迅速和供体短缺的限制.目的:充分认识分子吸附循环系统在肝移植等待期急性肝功能衰竭治疗中的作用.检索策略:由第一作者应用计算机检索Pubmed数据库及ISI Web of Knowledge数据库1993-01/2007-12有关分子吸附循环系统治疗肝移植等待期急性肝功能衰竭的文献,检索词为"acute liver failure,molecular adsorbent recycling system,artificial liver",并限定文章语言种类为English.同时检索中国期刊全文数据库1993-01/2007-12有关分子吸附循环系统治疗肝移植等待期急性肝功能衰竭的文献,检索词为"急性肝功能衰竭,分子吸附循环系统,人工肝",并限定文章语言种类为中文.此外手工检索人工肝相关中文文献.对资料进行初审,纳入标准:细胞因子、肝性脑病、肝肾综合征、生存率等相关研究文献.排除标准:明显不随机、研究目的与课题无关的文献及重复性文献.文献评价:初检得到467篇文献,阅读鉴定纳入32篇满足全部纳入标准,其中9篇中文,23篇英文;有关分子吸附循环系统治疗急性肝功能衰竭学术背景的文献4篇,有关急性肝功能衰竭定义及治疗的文献5篇,有关分子吸附循环系统的应用及其对急性肝功能衰竭治疗效果的文献23篇.资料综合:传统人工肝治疗急性肝功能衰竭各有利弊,分子吸附循环系统结合以往人工肝的优点,突破各自的局限性,可同时清除水溶性和脂溶性毒素,清除致病因子,减轻脑水肿,维护血流动力学的稳定,改善肝肾功能,提高生存率.结论:分子吸附循环系统是治疗肝功能衰竭安全而有效的辅助方法,可帮助急性肝功能衰竭患者顺利渡过肝移植等待期.     

体外生物人工肝支持系统治疗肝功能衰竭的系统评价

背景：生物人工肝支持系统由生物反应器和细胞材料组成,治疗过程中可部分替代肝脏的主要功能如解毒、合成、分泌和生物转化等功能。目的：回顾和评价体外生物人工肝支持系统近15年来治疗肝功能衰竭的疗效。方法：检索1995至2009年PubMed和Cochrane数据库有关生物人工肝支持系统的临床研究。被纳入的研究类型包括随机对照试验、临床对照试验和病例报告。结果与结论：共纳入31项研究,在生物人工肝支持系统治疗之后,患者生化指标呈现好转趋势,且大部分患者神经系统症状均得到改善,但多数患者生存率未见明显改善。说明尽管生物人工肝支持系统被证明具有一定治疗效果,但今后仍然有许多方面需要改进。     

肝干细胞的来源与移植应用

目的:肝干细胞的研究已成为近年的热点,本文检索了肝干细胞的分类、诱导、分离、培养及移植后的鉴定方法,分析了它们与肝病的关系和临床应用前景。资料来源:应用计算机检索PUBMED2000-01/2005-01和EBSCO2000-01/2005-01期间的相关文章,检索词为“hepaticstemcells”,并限定文章语言种类为英文。同时计算机检索万方数据库2000-01/2005-01期间的相关文章,检索词为“肝干细胞”,并限定文章语言种类为中文。资料选择:对资料进行初审,并查看每篇文献后的引文。纳入标准:文章所述内容应与肝干细胞的研究相关。排除标准:重复研究或Meta分析类文章。资料提炼:共收集到161篇相关文献,37篇文献符合纳入标准,排除的124篇文献中是由于内容陈旧或重复。资料综合:37篇文献中,28篇涉及肝干细胞的分类,6篇涉及肝干细胞的诱导、分离、培养及移植后的鉴定,3篇涉及肝干细胞的临床应用。一般认为肝干细胞是多源性的,可分为内源性和外源性两大类。目前已经建立的细胞分离方法主要是基于细胞表面标志的免疫分离法,包括应用流式细胞仪的荧光激活细胞分离法和免疫磁珠分离法,它们根据表面标志的有无和表达的高低来确定细胞的类型和特征。这样可能会忽略了一些标志阴性却具有肝细胞分化潜能的肝干细胞,所以肝干细胞的分离有待改进。在临床应用中,肝细胞移植为病损肝脏的细胞重建及衰竭肝脏的功能恢复提供了一种全新的治疗策略,具有移植技术简单、对受体影响小、价格相对低廉等优点,但免疫排斥、肝细胞的来源、移植肝细胞在体内的增殖等问题尚未完全解决。结论:目前对急性或晚期肝病引起的肝功能衰竭,最佳治疗方法是肝移植,包括原位肝移植、肝细胞移植和生物人工肝3种方法。原位肝移植受肝源缺乏和免疫排斥所限,受益者很少;后两者均因肝细胞来源问题,临床价值受限。而利用肝干细胞移植和肝组织工程治疗各种肝病其前景已得到肯定。     

肝脏干细胞研究及应用前景展望

背景：近年肝脏干细胞移植治疗终末期肝病得到人们的广泛关注,但临床应用中却面临来源有限,细胞数量不足,移植后干细胞往往弥散、流失,且分化率低,无法有效发挥其修复功能等技术问题制约。目的：总结肝脏干细胞组织工程的研究进展,并展望其应用前景。方法：应用计算机检索1999-01/2010-12 PubMed数据库相关文献,英文检索词＂liver stem cell tissue engineering＂分别与＂three dimensional culture,biodegradable materials,biological reactor＂组合,并限定文献语言种类为English。共检索到文献241篇,最终纳入符合标准的文献43篇。结果与结论：肝脏干细胞来源有限,而肝脏组织工程需要大量可靠的种子干细胞,三维培养是目前发现行之有效的体外扩增手段。在三维培养条件下,使用不同支架材料和反应器扩增效率及移植效果存在巨大差异,如何确定具有肝脏干细胞特异性的理想扩增条件、改善支架生物相容性以提高移植效率是关键技术问题。未来的研究需要进一步探讨肝脏干细胞特异性扩增生物反应器及肝脏干细胞特异性支架构建等技术难点。     

肝干细胞向成熟肝细胞诱导分化的体内外特点

学术背景:肝干细胞能够被诱导分化为肝细胞,移植肝干细胞可以修复受损肝组织,代偿部分肝功能.目的:介绍体内外诱导肝干细胞分化为成熟肝细胞的研究现状.检索策略:应用计算机检索Pubmed 2000-01/2007-10期间相关文献,检索词"liver stem cell,differentiation",并限定文献语种为"English",同时计算机检索万方数据库2000-01/2007-10期间相关文献,检索词"肝干细胞,分化",并限定文献语种为中文.纳入标准:文章内容与肝干细胞诱导分化相关.排除标准:重复研究或Meta分析类文章.文献评价:就检索到的100余篇文献进行筛选,选择以肝干细胞诱导分化为主要研究内容的文献38篇,以近年发表在较权威杂志者优先,其中关于细胞分离培养及增殖的5篇,体外诱导分化的22篇,体内诱导分化的11篇.从筛选到的30余篇文献中进一步对关于向成熟肝细胞分化的文献进行归纳及整理,选择其中28篇作为参考文献进行综述.资料综合:肝脏干细胞根据起源不同,可分为肝源性肝干细胞和非肝源性肝干细胞,前者包括卵圆细胞、分化的肝细胞、胎肝细胞和胆管上皮细胞,后者包括胚胎干细胞、骨髓造血干细胞、胰腺上皮祖细胞及肠上皮细胞等,均具有多向性演变的特性.肝干细胞的诱导分化:①体外诱导分化:可以是不同细胞因子或化学剂或病理微环境为主的细胞诱导培养体系,能使肝干细胞定向转化为肝细胞.②体内诱导分化:通过不同途径将肝干细胞植入体内,能够改善肝功能和受损肝脏的组织结构.结论:肝干细胞研究仍处于理论和实验阶段,应进一步加强对干细胞诱导分化机制的研究,防止向肿瘤细胞分化,促进其分化为成熟肝细胞,推进肝干细胞的临床应用.     

肝干细胞移植在肝病治疗中的应用

背景:目前,肝移植存在供体短缺、手术损伤、手术并发症发生率高以及费用高昂等问题,而肝干细胞移植为终末期肝病的治疗提供了崭新的思路.目的:介绍肝干细胞的来源与分类、肝干细胞移植治疗终末期肝病的研究现状及面临的问题,并展望了其临床应用前景.方法:应用计算机检索中国期刊全文数据库(CNKI:1999/2009)和Medline database数据库(1999/2009)相关文献,检索词分别为"肝干细胞,肝脏疾病,移植"和"hepatic stem cells,liver disease,transplantation",语言分别设定为中文和英文,共检索到87篇文章,阅读文题和摘要进行筛选,选择具有原创性,论点论据可靠且分析全面的与肝干细胞移植临床应用密切相关的文章,排除重复研究及质量较差的文献,最后纳入30篇进行总结综述.结果与结论:肝干细胞可分为肝源性和非肝源性.肝源性肝干细胞包括肝卵圆细胞、成熟肝细胞和间充质干细胞等,非肝源性肝干细胞主要来源于胚胎干细胞、骨髓造血干细胞和胰腺干细胞等.目前肝干细胞治疗肿病的研究尚处在初期阶段,从肝干细胞的发现到分离、纯化、全面鉴定、体外培养、定向分化及临床试验等,仍存在许多难题需要研究解决.不过作为一种新兴的种子细胞来源,肝干细胞不但可替换受损组织,而且可刺激受体组织再生以达到自身修复的目的,所以相比现在临床常用的原位肝移植和生物人工肝而言,肝干细胞在治疗各种原因引起的肝脏疾病中都具有十分广阔的前景.     

人肝细胞移植的临床应用

背景:目前的人肝细胞来源主要是在器官移植过程中供者的肝脏不适用于肝移植的边缘性肝脏,故其限制了向临床提供良好功能的肝细胞源.目的:阐述人肝细胞移植的临床现状和面临的挑战,对人肝细胞移植的临床应用和面临的困难进行总结.方法:应用计算机检索万方、维普和PubMed数据库中1990-01/2010-09关于肝细胞移植方面的文章,在标题和摘要中以"肝细胞;移植;肝衰竭;肝细胞源"或"hepatocyte transplantation; Liver failure;Liver-based metabolic disorders"为检索词进行检索.选择文章内容肝细胞移植相关,同一领域文献则选择近期发表或发表在权威杂志文章,排除陈旧和重复性研究文献.结果与结论:初检得到213篇文献,根据纳入标准选择30篇文章进行综述.全球已有超过80例肝脏代谢性疾病和肝衰竭的患者接受了人肝细胞移植,移植后,初步早期的临床结果显示肝脏功能得到不同程度的改善,治疗的结果表明其广泛的临床应用是很有前景的.但进一步开发并完善肝细胞源是现阶段的最大挑战,移植的人肝细胞整合到受者肝脏内而存活的过程也需要进一步地完善.     

Acute liver failure: liver support therapies

PURPOSE OF REVIEW: We summarize the therapeutic approach to patients with acute liver failure with the main focus on bioartificial and artificial liver support. We also describe specific and general therapeutic approaches based upon recent advances in the understanding of the pathophysiology of acute liver failure. RECENT FINDINGS: Bioartificial liver support systems use hepatocytes in an extracorporeal device connected to the patient's circulation. Artificial liver support is intended to remove protein-bound toxins and water-soluble toxins without providing synthetic function. Both systems improve clinical and biochemical parameters and can be applied safely to patients. Although bioartificial liver-assist devices have not been shown to improve the survival of patients with acute liver failure, further development is underway. Artificial liver support systems have been shown to alter several pathophysiological mechanisms involved in the development of acute liver failure but survival data are still limited. SUMMARY: Mortality in patients with acute liver failure is still unacceptably high. The most effective treatment, liver transplantation, is a limited resource and so other therapeutic options to bridge patients to recovery or stabilization have to be considered. Better understanding of the pathophysiology of acute liver failure and device development is necessary to achieve the elusive goal of effective extracorporeal liver assist.     

Proliferative human cell sources applied as biocomponent in bioartificial livers: a review

INTRODUCTION: Bioartificial livers (BALs) are urgently needed to bridge severe liver failure patients to liver transplantation or liver regeneration. When based on primary hepatocytes, their efficacy has been shown in animal experiments and their safety was confirmed in clinical trials. However, a proliferative human cell source with therapeutic functionality is needed to secure availability and move BAL application forward. AREAS COVERED: This review compares the performance of BALs based on proliferative human biocomponents and primary hepatocytes. This review evaluates relevant studies identified by searching the MEDLINE database until July 2011 and some of our own unpublished data. EXPERT OPINION: All the discussed hepatocyte-like biocomponents show deficiencies in their hepatic functionality compared with primary hepatocytes, particularly functions occurring late in liver development. Nonetheless, the HepaRG, HepG2-GS-CYP3A4, and mesenchymal stem cells show efficacy in a statistically well-powered animal model of acute liver failure, when applied in a BAL device. Various methods to gain higher functionality of BALs, including genetic modification, the usage of combinatory cell sources, and improvement of culture methods, have scarcely been applied, but may further pave the path for BAL application. Clinical implementation of a BAL based on a human proliferative biocomponent is still several years away.     

人源肝细胞系CL-1、HepFMMU、HepG2、C3A生物学特性与功能的比较

目的:比较体外培养的四种人源肝细胞系CL-1、HepFMMU、HepG2、C3A生物学与功能特性的异同,初步评价其应用于生物人工肝的可行性,为其在组织工程学研究和临床医学中的应用奠定基础。方法:4种肝细胞在接种密度相同的条件下培养7d,观察4种细胞形态特征和功能状态,检测培养液中白蛋白、尿素及安定代谢量。结果:4种肝细胞系均具有较快的生长速度,功能学比较C3A具有良好的白蛋白合成和安定代谢功能;CL-1具有良好的尿素合成功能。结论:4种肝细胞具有良好的增殖能力,C3A具有良好的白蛋白合成及安定代谢能力,但其尿素合成能力较差,需进一步改进;CL-1具有较好的尿素合成能力,但其安定代谢和白蛋白合成功能较差;HepFMMU功能较差,不适宜用于生物人工肝。     

Proliferative human cell sources applied as biocomponent in bioartificial livers: a review

Introduction: Bioartificial livers (BALs) are urgently needed to bridge severe liver failure patients to liver transplantation or liver regeneration. When based on primary hepatocytes, their efficacy has been shown in animal experiments and their safety was confirmed in clinical trials. However, a proliferative human cell source with therapeutic functionality is needed to secure availability and move BAL application forward.

Areas covered: This review compares the performance of BALs based on proliferative human biocomponents and primary hepatocytes. This review evaluates relevant studies identified by searching the MEDLINE database until July 2011 and some of our own unpublished data.

Expert opinion: All the discussed hepatocyte-like biocomponents show deficiencies in their hepatic functionality compared with primary hepatocytes, particularly functions occurring late in liver development. Nonetheless, the HepaRG, HepG2-GS-CYP3A4, and mesenchymal stem cells show efficacy in a statistically well-powered animal model of acute liver failure, when applied in a BAL device. Various methods to gain higher functionality of BALs, including genetic modification, the usage of combinatory cell sources, and improvement of culture methods, have scarcely been applied, but may further pave the path for BAL application. Clinical implementation of a BAL based on a human proliferative biocomponent is still several years away.     

Lactobionic acid-functionalized polyethersulfone hollow fiber membranes promote HepG2 attachment and function

Surface modification of polyethersulfone hollow fibers, which are important in bio-artificial liver, is increasingly used to improve biocompatibility and promote the adhesion and proliferation of hepatocytes resulting in improved cell functionality. Hepatocytes are anchorage-dependent cells, and membrane surface modification enhances the hepatic cell adhesion and proliferation. Specific interaction of the asialoglycoprotein receptor on hepatocyte cell surfaces with a galactose moiety enhances the attachment of the cells on a biocompatible substrate. In this study, the outer surface of the polyethersulfone (P) hollow fiber membranes (HFMs) was chemically modified by covalent coupling with lactobionic acid (LBA). The energy dispersive X-ray spectrometry elemental mapping, attenuated total reflectance-Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy confirmed the LBA-coupling on the outer surface of P-LBA HFMs. Hemocompatibility study indicated the suitability of the modified membranes with human blood. These membranes showed remarkably improved biocompatibility with human primary mesenchymal stem cells and HepG2 cells. Characteristic multi-cellular spheroids of HepG2 cells were observed under scanning electron and confocal microscopy. HepG2 cell functional activity was measured by quantifying the urea synthesis, albumin secretion and glucose consumption in the culture media, which indicated the improved HepG2 functions. These experimental results clearly suggest the potentiality of these LBA-modified P HFMs as a suitable biocompatible substrate for promoting HepG2 attachment and function leading to their application in bioreactors and bio-artificial liver devices.

Surface modification of polyethersulfone hollow fibers, which are important in bio-artificial liver, is increasingly used to improve biocompatibility and promote the adhesion and proliferation of hepatocytes resulting in improved cell functionality.     

Hepatocyte culture systems for artificial liver support: implications for critical care medicine (bioartificial liver support).

OBJECTIVE: The primary purpose of this review article is to familiarize critical care practitioners with newly developing techniques of hybrid artificial liver support. Implantable and extracorporeal hepatocyte culture systems are emphasized based on their current experimental and clinical status. DATA SOURCES: Data used to prepare this document were obtained from the authors' personal files, as well as the computerized MEDLINE database. Medical headings used include: liver, artificial organs, cell culture, growth hormones, extracellular matrix, and transplantation. Only articles published in English have been cited. STUDY SELECTION: All studies are discussed in which hepatocyte culture systems have been used to support human patients with liver failure. All studies reported the patient's condition before therapy, duration of therapy, and outcome after therapy in order to be included in this review. Since the number of clinical trials is small at this time, animal studies were used to demonstrate application of other systems in the treatment of experimentally induced liver failure. Similar selection criteria were used to select animal studies for review. All initially identified human studies met these selection criteria. DATA EXTRACTION: Independent extraction by multiple observers. DATA SYNTHESIS: Liver failure, resulting from infection, drugs, or as a part of the multiple organ failure syndrome, remains a major cause of morbidity, mortality, and resource allocation. Current therapy is limited to supportive care, along with liver transplantation. Because of these therapeutic limitations, hybrid artificial liver systems have been proposed for temporary and long-term hepatic support. Several animal studies and a small number of preliminary human studies indicate that hepatocyte culture systems are capable of supporting nearly all essential hepatic functions and may supply biologically active substances that promote regeneration and repair of the damaged liver being supported. Hybrid systems may be constructed from materials that serve as immunoprotective barriers against host defenses. CONCLUSIONS: During the past decade, important progress has been made with hybrid artificial liver support systems. Cell culture technology has progressed sufficiently so that an artificial liver, composed of metabolically active hepatocytes, may be a potential reality in the foreseeable future. Both implantable and extracorporeal artificial liver support systems have been developed to provide metabolic support during acute liver failure, or to serve as a bridge to solid organ transplantation. Implantable hepatocyte systems, however, require a prolonged period for intraperitoneal engraftment and vascularization, not typically available to patients with acute liver failure. For this reason, extracorporeal hybrid designs offer the greatest hope for on-line treatment of acute liver failure. Such systems are entering the final stages of animal testing.     

Use of the molecular adsorbent recirculating system (MARS™) for the management of acute poisoning with or without liver failure

Introduction. There is an increasing interest in recent developments in bioartificial and non-bioartificial devices, so called extracorporeal liver assist devices, which are now used widely not only to increase drug elimination, but also to enhance the removal of endogenous substances in acute liver failure. Most of the non-bioartificial techniques are based on the principle of albumin dialysis. The objective is to remove albumin-bound substances that could play a role in the pathophysiology of acute liver failure by dialysing blood against an albumin-containing solution across a high flux permeable membrane. The most widely used device is the Molecular Adsorbent Recirculating System (MARS?). Methods. The relevant English and French literature was identified through Medline using the terms, ‘molecular adsorbent recirculating system’, ‘MARS’, ‘acute liver failure’, ‘acute poisoning’, ‘intoxication’. This search identified 139 papers of which 48 reported on a toxic cause for the use of MARS?. Of these 48 papers, 39 specified the substance (eighteen different substances were identified); two papers reported on the same group of patients. Bioartificial and non-bioartificial systems. Bioartificial systems based on porcine hepatocytes incorporated in the extracorporeal circuit are no longer in use due to the possibility of porcine retroviral transmission to humans. Historically, experience with such devices was limited to a few cases of paracetamol poisoning. In contrast, an abundant literature exists for the non-bioartificial systems based on albumin dialysis. The MARS? has been used more widely than other techniques, such as the one using fractionated plasma separation and adsorption (Prometheus?). All the extracorporeal liver assist devices are able to some extent to remove biological substances (ammonia, urea, creatinine, bilirubin, bile acids, amino acids, cytokines, vasoactive agents) but the real impact on the patient's clinical course has still to be determined. Improvement in cardiovascular or neurological dysfunction has been shown both in acute liver failure and acute-on-chronic liver failure but no impact on mortality has been reported. Acute poisoning with liver failure. Randomized controlled trials are very limited in number and patients poisoned by paracetamol or Amanita phalloides are usually included for outcome analysis in larger groups of acute liver failure patients. Initial results look promising but should be confirmed. Beyond its effect in liver failure, MARS? could also enhance the elimination of the drug or toxin responsible for the failure, as is described with paracetamol. Acute poisoning without liver failure. Extracorporeal liver assist devices have also been used to promote elimination of drugs that are highly protein bound. Data in various case reports confirm a high elimination of phenytoin, theophylline and diltiazem. However, definite conclusions on the toxicokinetic or clinical efficacy cannot be drawn. Conclusions. Despite the lack of large multicentre randomized trials on the use of MARS? in patients with acute liver failure, the literature shows clinical and biological benefit from this technique. In drug or toxin-induced acute liver failure, such as paracetamol or mushroom poisoning, MARS? has been used extensively, confirming in a non-randomized fashion, the positive effect observed in the larger population of acute liver failure patients. Furthermore, as MARS? has been shown in experimental studies to remove protein-bound substances, it is potentially a promising treatment for patients with acute poisoning from drugs that have high protein-binding capacity and are metabolized by the liver, especially, if they develop liver failure concomitantly.     

Development of a hybrid liver-support device

The development of an extracorporeal hybrid liver-support system using hepatocytes and an artificial device has been long awaited for the treatment of patients with hepatic failure. During the past decade important progress has been made in biotechnology and bioengineering, and a hybrid liver-support device using metabolically active hepatocytes may well become a reality in the near future. This paper outlines recent developments in bioreactor systems used as bioartificial liver-support devices, and focuses on critical issues for bioreactor design, main transport features and culture techniques for hepatocytes. We describe our bioreactor, which uses porcine hepatocytes, and the scaling-up of the device. The biochemical performance of such a device is comparable to that of those developed by other researchers, and we feel encouraged to perform in vivo experiments on animal models in order to evaluate the potential of the device as a bioartificial liver.