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A decade ago, albumin dialysis was introduced as a new extracorporeal detoxification method for patients with liver failure. Today, the molecular adsorbent recirculating system is the most frequently used type of albumin dialysis and most studied liver-support technique. Numerous preclinical and clinical studies demonstrated the importance of albumin as a scavenger for molecules with pathophysiological relevance in liver failure. Albumin dialysis enables the selective regeneration of albumin. The resulting increase of albumin binding capacity is paralleled by improvement of central and local hemodynamics and liver, brain, and kidney functions. The treatment can contribute to liver regeneration and prolongation of patient survival in the context of acute liver failure, decompensated chronic liver disease, and bridging of patients to liver transplantation. Proper patient selection is critical for clinical success. Aggressive treatment of infections and sepsis seems to be a decisive prerequisite for its safe and efficient use. Cautious anticoagulation with heparin is the common standard. Citrate use is recommended for patients prone to bleeding. Taken together, albumin dialysis represents a valuable therapeutic tool for the treatment of various types of liver failure. Ongoing and future studies will help define the optimal patient selection and technical process parameters such as session length and frequency of treatment.

Conventional treatment of severe viral disease is limited by the narrow choice as well as the often-significant side effects or lack of clear efficacy of antiviral chemotherapy. At the same time, however, it is known that a reduction in viral load leads to significant clinical improvement in a number of important viral diseases. In this paper we discuss the possibility of using preconditioned human phagocytes in an extracorporeal biohybrid system for adsorption of viral pathogens. We present data from in vitro experiments testing adsorption of an enterovirus and of hepatitis B virus (HBV) by a preconditioned human promyelocytic cell line. While no clearance of HBV could be detected, the results revealed a near elimination of enterovirus with the cell line displaying robust viability. Enterovirus titers of 1000 (reciprocal) were reduced to a mean titer of 100.6 CCID50 with no virus detectable after adsorption in two out of five samples. Titers of 10 000 (reciprocal) were in turn reduced to a mean of 101.4 CCID50. The kinetics of the process was remarkable with this near elimination of the pathogen occurring within only 15 min. Extracorporeal viral adsorption by a cellular biohybrid system appears feasible. Pairing target pathogens with suitable cell lines may offer a versatile antiviral technology.

Objectives: Granulocyte transfusions have been used to treat immune cell dysfunction in sepsis. As granulocyte transfusions can trigger tissue injury via local effects of neutrophils, we hypothesized that extracorporeal treatment of plasma using granulocytes would prove beneficial while having less side effects. Design: Prospective controlled three-armed animal study. Setting: Research laboratory. Subjects: Twenty-one female immature pigs (7.5-12 kg, 7-9 weeks old). Interventions: Three groups of spontaneously breathing, sedated pigs (n = 7 each) received an intravenous lethal dose of live Staphylococcus aureus over 1 hour. Although group I had no specific treatment (control), group II and III were subsequently treated for 4 hours with an extracorporeal device containing either no cells (sham control, group II) or human cell line-derived granulocytic cells (group III). Survival time and physiologic, biochemical, and hematologic parameters were monitored for 7 days. Measurements and Main Results: All animals of group I died during the observation time (mean survival time: 70 hours). In group II, two of seven and in group III, six of seven animals survived the observation time (mean survival: 75 and 168 hours, respectively). Survival differences were significant between group I and III (p < 0.001) and between group II and III (p < 0.05) but not between group I and II (p = 0.43). Furthermore, group differences in bacterial blood concentrations, differential blood count, blood gases, lactate, and interleukins were observed. The extracorporeal cell treatment was well tolerated by the animals. Conclusions: Extracorporeal therapy with granulocytic cells significantly improved survival in a pig model of sepsis. Further studies with this approach are encouraged.

Human serum albumin has multiple functions, the most important being maintaining colloid osmotic pressure, ligand binding and transport. In liver failure, an impaired binding of endogenous substances and drugs can be observed. The aim of this study was to investigate the relationship between the severity of liver disease and an impaired albumin binding.In 44 patients with decompensated liver cirrhosis, Child-Turcotte-Pugh and model for end-stage liver disease scores were assessed and the site II-specific albumin-binding function (albumin-binding capacity) was characterized. Briefly, the unbound amount of diazepam site ligand Dansylsarcosine in a sample was determined and compared with the unbound amount in a reference albumin solution (=100%).Thirty-two out of 44 of the patients presented with Child-Turcotte-Pugh class C, the median Child-Turcotte-Pugh score was 10 [6-13 (min-max)], median model for end-stage liver disease score was 21 (8-40) and the median albumin-binding capacity was 63 (24-91)% compared with healthy controls 98 (95-106)% (P0.001). Albumin-binding capacity was found to be strongly correlated to model for end-stage liver disease (r=0.783; P0.001).An impaired albumin-binding function of a site II-specific marker in decompensated liver cirrhosis was found to be correlated to the severity of the liver disease.

Patients with liver cirrhosis and a superimposed acute injury with progressive hyperbilirubinemia have a high mortality. A prospective, controlled study was performed to test whether hyperbilirubinemia, 30-day survival, and encephalopathy would be improved by extracorporeal albumin dialysis (ECAD). Twenty-four patients were studied; 23 patients had cirrhosis; 1 had a prolonged cholestatic drug reaction and was excluded from per protocol (PP) analysis. Patients had a plasma bilirubin greater than 20 mg/dL and had not responded to prior standard medical therapy (SMT). Patients were randomized to receive SMT with ECAD or without (control). ECAD was performed with an extracorporeal device that dialyzes blood in a hollow fiber dialyzer (MW cutoff60 kd) against 15% albumin. Albumin-bound molecules transfer to dialysate albumin that is regenerated continuously by passage through a charcoal and anion exchange column and a conventional dialyzer. ECAD was associated with improved 30-day survival (PP, 11 of 12 ECAD, 6 of 11 controls; log rank P.05). Plasma bile acids and bilirubin decreased on average by 43% and 29%, respectively, in the ECAD group after 1 week of treatment, but not in the control group. Renal dysfunction and hepatic encephalopathy improved in the ECAD group, but worsened significantly in the control group. ECAD was safe, with adverse events being rare and identical in both groups. In conclusion, ECAD appears to be effective and safe for the short-term treatment of patients with cirrhosis and superimposed acute injury associated with progressive hyperbilirubinemia and may be useful for increasing survival in such patients awaiting liver transplantation.

Extracorporeal liver support using the MARS recently has shown remarkable results in several trials. This study aims to extend the basis for analyses by making available the worldwide data with help of an international registry. One hundred and seventy six patients were analysed, main indications are acute-on-chronic liver failure (56%), acute liver failure (22%), primary graft dysfunction (15%), liver failure post liver surgery (4%) and miscellaneous (3%). The predicted survival within the first group based on a mean MELD score of 30.4 pts. and a mean Child score of 12.6 pts. was quite limited. The data suggest an improved survival accompanied by significant improvements of hepatic encephalopathy, mean arterial pressure, serum bilirubin level, creatinine, urea, albumin, INR, ammonia and MELD score. The results are confirming observations of other trials before which have shown MARS therapy to be an effective and safe extracorporeal liver support in liver failure.

Artificial liver support aims to prolong survival time of patients with liver failure by detoxification. Albumin as a molecular adsorbent in dialysis solution is capable of attracting even tightly albumin-bound toxins from blood into the dialysate if a specific dialysis membrane is used and if the albumin's binding sites are on-line-purified by a sorbent/dialysis-based recycling system (i.e., molecular adsorbents recycling system, or MARS). The MARS technology has been shown to remove water-soluble and albumin-bound toxins and to provide renal support in case of renal failure. Fourteen centers have reported that MARS treatment improved mental status of patients with liver failure and hepatic encephalopathy. In treating liver failure and cholestasis, MARS was associated with hemodynamic stabilization, improvement of hepatic and kidney function, and disappearance of pruritus. In hepatic failure and hepatorenal syndrome, a prospective, randomized, controlled trial of MARS treatment was able to prolong survival time significantly. MARS has been used in 26 patients with acute liver failure or primary graft dysfunction. Nineteen centers reporting on 103 patients have shown that MARS treatment is safe, easy to handle, feasible, and effective.

Recently, significant improvement of renal function and prolongation of survival were reported in hepatorenal syndrome (HRS) patients treated with the Molecular Adsorbent Recirculating System (MARS). As no impact on extrarenal organ function was documented, this trial looked into multiple organ function changes during MARS in HRS patients. Eight HRS patients (4 male, mean age 42.1 years, range 30-58, all United Network for Organ Sharing [UNOS] status 2A) were treated intermittendly 4-14 times (total 47, mean 5.9 +/- 3.4) between 4 and 8 h/single treatment. The following changes were observed pre- and posttreatment: bilirubin 466 +/- 146 to 284 +/- 134 micromol/L, creatinine 380 +/- 182 to 163 +/- 119 micromol/L, urea 26.4 +/- 10.3 to 12.9 +/- 4.9 mmol/L, plasma sodium 127.5 +/- 7.7 to 137.5 +/- 4.8 mmol/L (all p < 0.01). Mean arterial pressure (MAP) increased from 71.9 +/- 12.8 to 95.6 +/- 7.8 Torr (p < 0.001). Oliguria or anuria, present in all patients, was successfully reverted. Ascites, present in all patients, was not detectable after the treatment period. The hepatic encephalopathy grade decreased from 2.8 +/- 0.8 to 0.8 +/- 0.7 (p < 0.0001). Child-Index decreased from 13.25 +/- 1.3 to 9.4 +/- 1.8 (p < 0.001). The hospital survival rate was 62%. One man underwent successful liver transplantation 18 months after the treatment. We conclude that MARS can improve multiple organ functions in patients with HRS.

Because gene therapy of the future will primarily take an in vivo approach, a number of problems associated with its current implementation exist. Currently, repeated delivery of a vector in vivo is necessary to ensure adequate transfer of the therapeutic gene. This may lead to the development of an immune response against the vector, thus interfering with gene delivery. To circumvent this problem, retroviral vector packaging cells that permanently produce recombinant retroviral vector particles have been encapsulated.Vector (pBAG)-producing amphotropic cells were encapsulated in beads composed of polymerized cellulose sulphate. These capsules were analysed in vitro for expression of the vector construct using X-gal staining, as well as for the release of particles by performing RT-PCR from culture supernatant. Infectivity studies were performed in vitro and in vivo. The latter was assayed using histological sections of the microcapsule and the surrounding area stained for beta-galactosidase activity and by RT-PCR.In culture, the virus-producing cells inside the capsules remained viable and released virus into the culture medium for at least 6 weeks. To test whether these capsules, upon implantation into mice, also release vector virions that infect the surrounding cells, two different models were used. In the first, capsules were implanted in the fat pad of the mammary gland of Balb/c mice. The capsules were well tolerated for at least 6 weeks and a self-limiting inflammatory reaction without any other gross immune response was observed during this period. Furthermore, the virus-producing cells remained viable. In the second model, SCID mice were immunologically reconstituted by subcutaneous implantation of thymus lobes from MHC-identical Balb/c newborn mice and gene transfer into lymphoid cells was achieved by retroviral vectors released by co-implanted capsules.The implantation of such capsules containing cells that continually produce retroviral vector particles may be of use for in vivo gene therapy strategies. The data presented demonstrate the feasibility of the concept.

Liver support systems based on either dialysis, filtration, and adsorption or plasmaperfusion over hepatocytes have been tested clinically with varying success. A new approach in this field is the selective removal of albumin-bound end products of metabolism. This can be achieved in a high-flux dialysis setting by the addition of human serum albumin as a molecular adsorbent to the dialysate with subsequent recirculation of the dialysate over sorbents (molecular adsorbent recirculating system). The current knowledge about the albumin dialysis molecular adsorbent recirculating system is reviewed in this article.

Long-term benefits of coronary angioplasty remain limited by the treatment-induced renarrowing of arteries, termed restenosis. One of the mechanisms leading to restenosis is the proliferation of smooth muscle cells. Therefore, proliferating cells of the injured arterial wall, which can be selectively transduced by retroviruses, are potential targets for gene therapy strategies. A direct single-dose therapeutic application of retroviral vectors for inhibition of cell proliferation is normally limited by too low transduction efficiencies. Encapsulated retrovirus-producing cells release viral vectors from microcapsules, and may enhance the transduction efficiency by prolonged infection. Primary and immortal murine and porcine cells and murine retrovirus-producing cells were encapsulated in cellulose sulphate. Cell viability was monitored by analysing cell metabolism. Safety, stability, transfer efficiency and extent of restenosis using capsules were determined in a porcine restenosis model for local gene therapy using morphometry, histology, in situ beta-galactosidase assay and PCR. Encapsulation of cells did not impair cell viability. Capsules containing retrovirus-producing cells expressing the beta-galactosidase reporter gene were implanted into periarterial tissue or a pig model of restenosis. Three weeks following implantation, beta-galactosidase activity was detected in the pericapsular tissue with a transduction efficiency of approximately 1 in 500 cells. Adventitial implantation of vector-producing encapsulated cells for gene therapy may, therefore, facilitate successful targeting of proliferating vascular smooth muscle cells, and allow stable integration of therapeutic genes into surrounding cells. The encapsulation of vector-producing cells could represent a novel and feasible way to optimize local retroviral gene therapy.

Liver failure associated with excretory insufficiency and jaundice results in an endogenous accumulation of toxins involved in the impairment of cardiovascular, kidney, and cerebral function. Moreover, these toxins have been shown to damage the liver itself by inducing hepatocellular apoptosis and necrosis, thus creating a vicious cycle of the disease. We report a retrospective cohort study of 26 patients with acute or chronic liver failure with intrahepatic cholestasis (bilirubin level > 20 mg/dL) who underwent a new extracorporeal blood purification treatment. A synthetic hydrophilic/hydrophobic domain-presenting semipermeable membrane (pore size < albumin size, 100-nm thick) was used for extracorporeal blood detoxification using dialysis equipment. The opposite side was rinsed with ligandin-like proteins as molecular adsorbents that were regenerated online using a chromatography-like recycling system (molecular adsorbent recirculating system [MARS]). Bile acid and bilirubin levels, representing the previously described toxins, were reduced by 16% to 53% and 10% to 90% of the initial concentration by a single treatment of 6 to 8 hours, respectively. Toxicity testing of patient plasma onto primary rat hepatocytes by live/dead fluorescence microscopy showed cell-damaging effects of jaundiced plasma that were not observed after treatment. Patients with a worsening of Child-Turcotte-Pugh (CTP) index before the treatments showed a significant improvement of this index during a period of 2 to 14 single treatments with an average of 14 days. After withdrawal of MARS treatment, this improvement was sustained in all long-term survivors. Ten patients represented a clinical status equivalent to the United Network for Organ Sharing (UNOS) status 2b (group A1), and all survived. Sixteen patients represented a clinical status equivalent to UNOS status 2a, and 7 of these patients survived (group A2), whereas 9 patients (group B) died. We conclude that in acute excretory failure caused by a chronic liver disease, this treatment provides a therapy option to remove toxins involved in multiorgan dysfunction secondary to liver failure.

In hepatorenal syndrome (HRS), renal insufficiency is often progressive, and the prognosis is extremely poor under standard medical therapy. The molecular adsorbent recirculating system (MARS) is a modified dialysis method using an albumin-containing dialysate that is recirculated and perfused online through charcoal and anion-exchanger columns. MARS enables the selective removal of albumin-bound substances. A prospective controlled trial was performed to determine the effect of MARS treatment on 30-day survival in patients with type I HRS at high risk (bilirubin level,or =15 mg/dL) compared with standard treatment. Thirteen patients with cirrhosis with type I HRS were included from 1997 to 1999. All were Child's class C, with Child-Turcotte-Pugh scores of 12.4 +/- 1. 0, United Network for Organ Sharing status 2A, and total bilirubin values of 25.7 +/- 14.0 mg/dL. Eight patients were treated with the MARS method in addition to hemodiafiltration (HDF) and standard medical therapy, and 5 patients were in the control group (HDF and standard medical treatment alone). None of these patients underwent liver transplantation or received a transjugular intrahepatic portosystemic shunt or vasopressin analogues during the observation period. In the MARS group, 5.2 +/- 3.6 treatments (range, 1 to 10 treatments) were performed for 6 to 8 hours daily per patient. A significant decrease in bilirubin and creatinine levels (P.01) and increase in serum sodium level and prothrombin activity (P.01) were observed in the MARS group. Mortality rates were 100% in the control group at day 7 and 62.5% in the MARS group at day 7 and 75% at day 30, respectively (P.01). We conclude that the removal of albumin-bound substances with the MARS method can contribute to the treatment of type I HRS.

Implantation of capsules containing antibody-producing cells into patients would potentially permit systemic long-term delivery of antibodies and might, thus, be useful in the development of surveillance treatments for cancers and severe viral diseases. We show that cellulose sulphate (CS) capsules containing hybridoma cells, when implanted subcutaneously or in the intraperitoneal cavity, can be used for delivering monoclonal antibodies into the blood-stream of immunocompetent mice for at least several months. In contrast to capsules implanted into the intraperitoneal cavity, which remain mobile and nonvascularized, capsules implanted under the skin form neo-organs which become vascularized within days. This may explain the higher blood concentration of the antibody we have observed in the latter case. Importantly, neither an isolating fibrosis nor an obvious inflammatory response was detected at the capsule implantation sites during observation periods as long as 10 months. Finally, no anti-idiotypic immune response against the ectopically delivered antibody was shown to occur. This rules out any potent adjuvant effect of the cellulose sulphate matrix that might have stimulated a neutralizing humoral response. Taken together, our data indicate that encapsulation of antibody-producing cells into CS might be used in antibody-based gene/cell therapy approaches.

The human phagocytosis system represents a major immunological defense barrier. At the onset of bacterial sepsis the phagocytosis capacity of blood neutrophils markedly decreases to values below 30% of normal. Therefore it seems a reasonable therapeutic approach to support the phagocytosis system by an extracorporeal phagocytosis device. We demonstrate in vitro-data showing that phagocytosis of relevant amounts of pathogenic bacteria and fungi can be achieved in suitable bioreactor-systems. The human promyelocytic cell line HL-60 was differentiated towards neutrophils upon stimulation with all trans-retinoic acid (atRA). The phagocytosis index of stimulated HL-60 was higher than in normal peripheral blood neutrophils. The HL-60 phagocytosis among others comprises internalization of living and dead E.coli, Staphylococcus aureus and Candida albicans. Highly relevant concentrations of Candida albi-cans could be removed from cell culture-medium (2×105 C. alb./ml). Stimulated phagocytes can be separated by magnetic microbeads from inactive cells to increase the efficiency of the system. In conclusion phagocytosis assist seems to be an interesting approach to extracorporeal detoxification in sepsis and neutropenia lowering the microbial burden of the blood.

Combination of detoxifying liver support systems with liver cell bioreactors may have additional benefits for the treatment of liver failure due to the replacement of known and unknown metabolic activities of the liver. However, the problem of side effects and possible risks caused by the use of animal hepatocytes or hepatoma cells remains unsolved which underlines the need of a safety barrier between the patients blood and the extracorporeal bioreactor. Passive filters do not meet the requirements of such membranes, because in liver failure desired and undesired molecules in the patients blood share similar physicochemical properties. That challanges the developement of biologically designed separation membranes. A hybrid membrane is formed by implementation of transport proteins into a highly permeable hollow fiber. The transport of free solutes and albumin bound toxins is tested in vitro in comparison with conventional high flux membranes. The transport characteristics for tightly albumin bound toxins are significantly improved for the hybrid membrane. The transport of albumin bound toxins across the membrane is not associated with albumin. The selectivity of the transport is evaluated in vivo. No significant loss of middle molecular weight hormones attached to other carrier proteins was observed. Neither transport of immunologically relevant proteins across the membrane nor loss of valuable proteins was measured. Also in vivo, a significant reduction of protein bound toxins and a transport of metabolically relevant solutes, like amino acids, was shown. The presented hybrid membrane may be used like an “intellegent membrane” as a safety barrier between the patients blood and cell devices.

It is currently in discussion whether or not established liver cell lines can be used for an extracorporeal liver assist device. Thus, metabolic features of primary hepatocytes, immortalized hepatocytes, and hepatoma cells were compared. The ability of these cells to process toxic blood of patients with hepatic failure was investigated by testing their viability in toxin enriched medium that was obtained by toxin separation from patients' blood via a molecular adsorbents recirculating system (MARS). In addition, glucose metabolism, urea synthesis, P450 dependent verapamil metabolism using high performance liquid chromatography, and interleukin-6 induced "acute phase" reaction by sulfodesoxysalicylic acid-polyacrylamide gel electrophoresis detected changes of albumin synthesis were determined in primary hepatocytes and in established liver cells. The viability of hepatoma cells after contact with the toxic compounds coming from the patients' blood was significantly decreased in comparison to that of immortalized hepatocytes and primary hepatocytes. Immortalized hepatocytes and hepatoma cells showed a significantly higher consumption of glucose associated with a significantly higher lactate synthesis. A basic urea synthesis rate could be measured in immortalized hepatocytes and hepatoma cells, but it was significantly lower than that of primary cells. P450 with its subenzyme CYP2C was inducible only in primary hepatocytes and in immortalized cells, but in the latter the enzymatic activity was lower than that of primary cells. The incubation with acute phase mediators resulted in a decrease of albumin synthesis in primary hepatocytes and in hepatoma cells, but it increased the albumin synthesis in immortalized hepatocytes. Summarizing these data, partially beneficial effects can be assumed if established cells are used in an extracorporeal liver assist device. These might include synthesis of some compounds and basic metabolic activities, such as urea synthesis. However, established liver cells showed clearly altered metabolic characteristics. The sufficient removal of toxic compounds requires additional strategies for detoxification by primary hepatocytes in sufficient amounts.