Cell Sources for Bioartificial Liver Support

The present review discusses hepatocyte sources for a bioartificial liver. Intended requirements for cell sources are for example: synthesis of plasma proteins, detoxification and regulation. The need for highly differentiated hepatocytes is stressed. Furthermore, the gap between this objective on the one hand and the real possibilities as they appear today on the other is shown. Alternatives to primarily isolated hepatocytes are discussed, thereby elucidating the limits of established cell lines. In summary, it is postulated that the results expected from a bioartificial liver, are closely related to the source and type of cells used.

A Carrier-Mediated Transport of Toxins in a Hybrid Membrane. Safety Barrier between a Patients Blood and a Bioartificial Liver

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.

Atypical electrolyte kinetics during an emergency dialysis session in a patient with Leriche syndrome

A hemodialysis patient suffered from circulation failure due to a low output syndrome caused by a hyperkalemia (9.9 micromol/l) with typical ecg signs. An emergency hemodialysis was started. After 2 h ecg signs of hypokalemia (2.1 micromol/l) were detectable. Hemodialysis was stopped. 2 h later, serum potassium rose to 6.2 micromol/l. An obturation of the aorta and the inferior caval vein with perfusion through collateral vessels of the lower body side was obvious, resulting into a faster electrolyte correction in the upper and a delayed correction in the lower body side with a rebound in the upper compartment. Dialysis time and dialysate potassium (4.0 micromol/l) were increased. Furthermore no potassium problems occurred.

Prolonged survival of renal allograft in rats by methotrexate-albumin conjugates as immunosuppressive therapy

Methothrexate (MTX) causes unwanted adverse events by affecting gastrointestinal and bone marrow cells when used as an immunosuppressant. Our aim was to reduce those side effects by covalent binding of methothrexate to human serum albumin (HSA) targeting rapidly proliferating lymphocytes, which are known to ingest albumin as an energy source. Twenty-one rats received a kidney transplant. Group A (n = 5) received standard immunosupression (free MTX); group B (n = 9), albumin-MTX conjugates; and group C (n = 7) albumin control. The primary endpoint of this animal study was transplant survival, which was evaluated as death due to uremia. The study was terminated on day 100. Placebo-treated rat recipients (group C) rejected their grafts at a median of 8 days, which was prolonged to 17 days in standard immunosuppressed rats (group A), resulting in doubling transplant survival compared to nonimmunosuppressed animals. However, the same dose given as HSA-conjugated MTX prolonged the median survival time to 43 days. (group B). Hence, the administration of conjugated methotrexate appeared to result in a doubling of transplant survival compared with standard immunosuppression. Moreover, two animals receiving MTX-HSA became long-term survivors without additional immunosuppression. Further studies should be performed to evaluate the significance of these findings in larger animals and possibly in clinical studies.

[Extracorporeal blood purification in severe liver failure with the albumin dialysis MARS -- impact on relevant intensive care parameters]

Extracorporeal liver support methods have been tested for over 50 years now. Standard techniques of blood purification like dialysis, adsorption, hemo- and plasma filtration as well as bioreactor-based approaches using liver cells or tissues have been used. Most clinical experience, however, is limited to use in acute liver failure (ALF). Since 1993, the Molecular Adsorbent Recirculating System (MARS) has been used clinically -- a system that combines dialysis, filtration and adsorption in a biocompatible method. Human serum albumin (HSA) acts as a selective molecular adsorbent binding protein-bound compounds like bile acids or bilirubin. These substances can contribute to the maintenance or even further aggravation of liver failure. They are linked with the pathogenesis of hyperdynamic hypotonic circulation, hepatic encephalopathy, hepatorenal syndrome, impaired hepatic protein synthesis, and intractable pruritus seen in chronic liver failure. HSA takes over the toxic substances from a patient's blood and passes through a remote detoxification process including bicarbonate-dialysis and a two-step adsorption. It is then recirculated in the patient's blood. Up to today, more than 4000 patients have been treated in approximately 16,000 single sessions. Thus, MARS represents the most frequently used liver support method at the present time. In addition to ALF, mainly acute decompensations of chronic liver failures (ACLF) have been treated. The impact of the extracorporeal treatment on relevant medical parameters of intensive care medicine is discussed with regard to the specific situation of the liver-failure patient (susceptibility to infection, atypical picture and course of infection, coagulation disorders and bleeding tendencies).

Albumin dialysis in cirrhosis with superimposed acute liver injury: possible impact of albumin dialysis on hospitalization costs

Albumin dialysis using the Molecular Adsorbents Recirculating System (MARS) has been found to be beneficial in the treatment of cirrhotic patients with acute decompensation to improve survival as well as reduce associated complications. The present study attempts to analyze the costs involved, and compare it to the benefit as a result of the MARS therapy, thus evaluating its cost-effectiveness. Using the results of a study by Kim et al. describing the effects of complications on the cost of hospitalization in alcoholic liver disease patients, the expenditure incurred in a group of 11 patients treated with standard medical therapy (five survivors) and a group of 12 patients treated with MARS in addition (11 survivors) (Heemann et al., Hepatology 2002) were analyzed. MARS resulted in a reduction of in-hospital deaths, as well as liver disease-related complications. Both these factors led to a substantial reduction of costs in the MARS group, which was enough to counterbalance the extra costs associated with extra-corporeal therapy. In the control group, the total hospitalization cost per survivor were calculated to be at $35,904. In the MARS group, the overall expenditure per survivor including standard medical therapy plus additional MARS liver support therapy were $32,036--a saving of nearly $4000 compared to the control group. Therefore, it appears that the benefits of MARS therapy are enough to justify the cost of treatment and safe hospital costs, at least in the described population. However, further studies are needed to confirm these results.

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

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

RESULTS

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

CONCLUSION

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

Albumin dialysis: single pass vs. recirculation (MARS)

The single pass albumin dialysis (SPAD) was reported to be an alternative to the Molecular Adsorbent Recirculating System (MARS) for the effective removal of protein bound substances in liver failure. Three SPAD experiments using different albumin concentrations and dialysate flow rates were performed. In each experiment, 1000 ml human donor plasma, spiked with 250 mg unconjugated bilirubin, 200 mg sulfobromophthalein (BSP) and 115 mg glycocholic acid (N-[3alpha,7alpha,12alpha-trihydroxy-24-oxycholan-24-yl]glycine) - a conjugated bile acid (BA), circulated in a closed loop with 150 ml/min and was dialysed against albumin solution. These substances are bound to the different binding sites of albumin and have different association constants. For the comparison, the standard MARS experiment was performed using the same plasma flow rate of 150 ml/min. Moreover, the clearances of bilirubin for MARS and SPAD during clinical treatments were calculated using own data and those reported by Seige, Kreymann, Jeschke, et al. in Transplant Proc 1999; 31: 1371-5. The concentrations of bilirubin, BSP and BA were measured in plasma and dialysate and for these substances clearances (Cl) were calculated. It is known that the elimination rate of bilirubin is not very high during albumin dialysis in comparison to other substances, like bile acids, due to the high association constant. An increase of albumin concentration or the flow rate improved the efficacy but also raised the costs substantially. In this study, we have shown that MARS is the more effective kind of albumin dialysis for the important substances like bile acids. By SPAD an improvement of efficacy can be reached only by dramatic increase of the costs. Also, the earlier experiments showed that MARS is safer because of the removal of the stabilizers, which are normally included in the commercial albumin solutions.

Amino acid dysbalance in liver failure is favourably influenced by recirculating albumin dialysis (MARS)

INTRODUCTION

Dysbalance between branched chain (BCAA) and aromatic amino acids (AAA), which can be quantified by a low Fischer's Index (SigmaBCAA/SigmaAAA), as well as elevated levels of free tryptophan in plasma are common in hepatic failure and may contribute to the development of hepatic encephalopathy.

AIM

To evaluate the influence of a new extracorporeal detoxification system for liver failure (Molecular Adsorbents Recirculating System, MARS(R), i.e. dialysis against a recirculating albumin solution cleaned online by charcoal and an anion exchange resin) on plasma tryptophan and Fischer's Index.

METHODS

Plasma samples were taken before, during and after MARS treatments (n = 11, mean blood flow 135 ml/min, mean dialysate flow 120 ml/min, high flux polysulfone membrane). Simultaneous to blood sampling, aliquots of the albumin dialysate were taken between the elements of the dialysate circuit.

RESULTS

Fischer's Index in systemic blood increased during MARS by 24% (from 1.44 to 1.79, P < 0.001; mean treatment duration, 5.5 h). Systemic tryptophan level was significantly reduced at the same time (-25%, n = 8). Amino acid removal rates from plasma during a single dialyser passage ranged from 10 to 53%. In particular, AAA were preferentially removed (42-44% throughout treatment), while BCAA removal was 28-46% initially and later declined to 24-28%. A maximum concentration gradient between plasma and dialysate was maintained for the AAA throughout treatment through their apparently complete removal by the charcoal adsorber. Conversely, BCAA removal at both adsorbers was only minor. As a result, Fischer's Index showed a significant increase in the processed plasma, which became even more pronounced with increasing treatment duration.

CONCLUSIONS

MARS enables an elevation of a pathologically decreased Fischer's Index as well as a reduction of systemic tryptophan levels in patients with liver failure. The effects of MARS on plasma amino acid dysbalance may contribute to an improvement of hepatic encephalopathy.

Improvement in central nervous system functions during treatment of liver failure with albumin dialysis MARS--a review of clinical, biochemical, and electrophysiological data

The Molecular Adsorbent Recirculating System (MARS) is a nonbiological liver support method based on the principles of dialysis, filtration, and adsorption. It allows the safe and efficient removal of both albumin-bound and water-soluble toxic metabolites, including ammonia, aromatic amino acids, tryptophan, and related phenolic and indolic products, as well as benzodiazepines. A well-documented effect of the treatment is the improvement of the hemodynamic situation of decompensated chronic patients. Systemic vascular resistance, mean arterial pressure, cerebral blood flow, and cerebral oxygen consumption increased significantly. The degree of hepatic encephalopathy decreased significantly. Increased intracranial pressure could be normalized in both chronic and fulminant liver failure. In three randomized clinical trials significant improvement of survival could be demonstrated. In a model of murine neuronal networks cultured on multi-microelectrode array plates and incubated with plasma from liver failure patients, a normalization of the spike and burst pattern could be observed, if plasma samples from MARS-treated patients before and after treatment were compared. In conclusion, MARS significantly improves central nervous system functions. It can serve as a model for the further investigation of the role of protein-bound substances in hepatic encephalopathy and cerebral hemodynamics.

Delay in the diagnosis of cutaneous melanoma: an analysis of 233 patients

Knowledge of factors associated with the detection of cutaneous malignant melanomas and reasons for delay in diagnosis are essential for the improvement of secondary prevention of cutaneous melanoma. For this reason, the extent and consequence of patient and professional delay in diagnosis and treatment was investigated in 233 patients with histologically proven primary cutaneous melanomas seen at the Department of Dermatology and Allergology at the Ludwig-Maximilians-University, Munich, Germany, between January 1999 and January 2001. Personal interviews were conducted by two physicians to obtain information on patients' knowledge of melanoma symptoms, sun behaviour, delay in seeking medical attention, professional delay and related factors. The main component of delay was patient related. Nearly one-third (29.2%) of all patients reported a delay interval of more than 12 months from the onset of an observed change in a pigmented lesion or first detection of a pigmented lesion to the first visit to a physician. The delay interval from the first visit to a physician to surgical treatment was shorter (< 1 month) in most of our patients (74.7%). The predominant symptoms of melanoma detected by patients were a change in colour and an increase in size or elevation. Most patients had obtained knowledge about cutaneous melanomas from television and magazines. A delay in diagnosis and a history of many sunburns and outdoor leisure time activities were not associated with a greater tumour thickness. However, fairer skin types, lower education levels and lack of knowledge about cutaneous melanoma were associated with a greater tumour thickness. Further efforts are necessary to improve public and medical education about early detection and prompt surgical treatment, which is known to be the most effective treatment modality for cutaneous melanomas.

MTS colorimetric assay in combination with a live-dead assay for testing encapsulated L929 fibroblasts in alginate poly-L-lysine microcapsules in vitro

Biomaterials such as applied in microcapsules may have harmful effects on encapsulated cells. Up to now, there are no adequate assays available for testing the function and viability of cells in capsules. Therefore, we investigated whether the combination of MTS proliferation assay and live-dead viability assay is suitable for testing microencapsulated L929 fibroblasts in long-time culture. Proliferation of L929 cells was shown by a significant increase of formazan absorbance within the first 3 weeks (Day 0: 0.132 +/- 0.047; Day 7: 0.404 +/- 0.101; Day 14: 0.728 +/- 0.239; Day 21: 0.877 +/- 0.224) followed by stagnation and decrease thereafter. This was confirmed by an increasing proportion of dead cells measured by the live-dead assay. Thus, proliferation of encapsulated L929 can be reliably investigated by the MTS assay. In combination with life-dead assays, the proliferation can be correlated to the survival rate of the encapsulated cells.

Albumin dialysis using the molecular adsorbent recirculating system

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.

Improvement of multiple organ functions in hepatorenal syndrome during albumin dialysis with the molecular adsorbent recirculating system

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.

Use of human preconditioned phagocytes for extracorporeal immune support: introduction of a concept

Neutrophils are critical effector cells in humoral and innate immunity and play a vital role in phagocytosis and bacterial killing. If they and/or their specific functions are lacking, then immunoparalysis may occur, and severe diseases like systemic inflammatory response syndrome (SIRS) or sepsis can take a fatal course. In this paper, we discuss the possibility of using preconditioned cells in an extracorporeal biohybrid immune support system. A human promyelocytic cell line was stimulated for different times with all-trans retinoic acid. The resulting cells displayed major signs and functions of mature neutrophilic granulocytes including oxygen radical production, phagocytosis of living and dead Escherichia coli, Staphylococcus aureus, Candida albicans, intracellular killing, and interleukin production. The cells can be expanded to yield a sufficient cell mass, and subsequent prestimulation results in an expression of specific neutrophil functions. Extracorporeal bioreactor experiments seem to be feasible to test the benefit in immunoparalysis-associated diseases like SIRS or sepsis.

In vivo perivascular implantation of encapsulated packaging cells for prolonged retroviral gene transfer

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.

Extracorporeal detoxification using the molecular adsorbent recirculating system for critically ill patients with liver failure

Liver failure resulting from different causes and its concomitant complications represent difficult-to-treat conditions with high mortality rates, despite improved therapeutic modalities in intensive care medicine. The accumulation of albumin-bound metabolites that are normally cleared by the liver, such as bilirubin and bile acids, contributes substantially to the development of multiorgan dysfunction in these clinical situations. The molecular adsorbent recirculating system (MARS) represents a cell-free, extracorporeal, liver assistance method for the selective removal of albumin-bound substances. Moreover, it enables the removal of excess water and water-soluble substances via an inbuilt dialysis step. Since 1993, >400 patients have been treated in 53 centers in Europe, the United States, and Asia. Diseases treated with MARS included acute exacerbation of chronic hepatic failure, hepatorenal syndrome, acute hepatic failure, and primary nonfunction/poor function after liver transplantation and major liver resection. Treatments were well tolerated. No severe adverse events were observed. Six- to 8-h MARS treatments resulted in significant (P < 0.05) removal of bilirubin, bile acids, tryptophan, short- and middle-chain fatty acids, aromatic amino acids, and ammonia. Clearance rates for strongly albumin-bound substances were between 10 and 60 ml/min. The removal of albumin-bound toxins resulted in decreases in hepatic encephalopathy, increases in mean arterial pressure, and improvements in kidney and liver function. In the first randomized clinical trial of the MARS method for treatment of the hepatorenal syndrome, significant prolongation of survival was observed for the MARS-treated group. It is concluded that the MARS method can contribute to the treatment of critically ill patients with liver failure and different underlying diseases.

Liver support by extracorporeal blood purification: a clinical observation

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.

Improvement of hepatorenal syndrome with extracorporeal albumin dialysis MARS: results of a prospective, randomized, controlled clinical trial

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.

Improvement of hepatorenal syndrome with extracorporeal albumin dialysis MARS: results of a prospective, randomized, controlled clinical trial

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.

Molecular adsorbent recycling system (MARS): clinical results of a new membrane-based blood purification system for bioartificial liver support

The use of xenogenic or genetically engineered cell types in bioartificial liver support systems requires separation methods between the patients' blood and the liver support bioreactors that guarantee the sufficient transfer of pathophysiologically relevant substances but prevent complications. The present paper describes a new membrane separation system that is nearly impermeable to proteins but enables the exchange of water soluble and protein bound toxins by a special membrane and a recycled protein containing dialysate. Because the full range of toxins in hepatic failure has still not been identified, the value of this membrane separation method was evaluated clinically. Thirteen patients suffering from life threatening hepatic failure who had not responded to state of the art therapy were treated with this device, the molecular adsorbent recycling system (MARS). The overall survival rate was 69%. All patients showed positive response to the therapy, indicating that the presented membrane separator combines therapeutic effectivity with the highest safety criteria for the patient by cutting the exchange of substances below the level of proteins.

Targeted chemotherapy by intratumour injection of encapsulated cells engineered to produce CYP2B1, an ifosfamide activating cytochrome P450

The prognosis of pancreatic adenocarcinoma is poor and current treatment ineffective. A novel treatment strategy is described here using a mouse model system for pancreatic cancer. Cells that have been genetically modified to express the cytochrome P450 2B1 enzyme are encapsulated in cellulose sulphate and implanted into pre-established tumours derived from human pancreatic cells. Cytochrome P450 2B1 converts the chemotherapeutic agent ifosfamide to toxic metabolites. Administration of ifosfamide to tumour-bearing mice that were recipients of implanted encapsulated cells results in partial or even complete tumour ablation. These results suggest that in situ chemotherapy with genetically modified cells in an immunoprotected environment may prove useful for application in man.

Systemic long-term delivery of antibodies in immunocompetent animals using cellulose sulphate capsules containing antibody-producing cells

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.

Prediction of in vivo drug interaction from in vitro systems exemplified by interaction between verapamil and cimetidine using human liver microsomes and primary hepatocytes

Emphasis on drug safety is increasing as newly developed drugs become more potent. Interest in the prediction and description of drug interactions is growing accordingly. The study of potential interactions at a very early stage of drug development requires suitable in vitro models that describe drug interactions both qualitatively and quantitatively. The purpose of the work described here was to help assess the predictive value of in vitro drug interaction tests with liver microsomes and hepatocytes by means of the interaction between verapamil and cimetidine. The in vitro inhibition of verapamil metabolism by cimetidine observed during the studies was quantitatively similar to the results reported in published clinical studies after intravenous application. Studies using liver microsome fractions showed that the intrinsic clearances for the formation of various metabolites could be used to predict drug interactions. In addition, work with hepatocyte cultures revealed that an in vitro system covering both phase I and phase II reactions should be included in such studies to permit quantitative prediction of the various metabolic pathways. Both human hepatocyte cultures and human microsomes offer certain advantages for predicting the degree of drug metabolism and interactions in humans at the biotransformation level. Therefore, it seems likely that the simultaneous application of both systems will yield conclusions that most closely approximate the situation in humans.

A carrier-mediated transport of toxins in a hybrid membrane. Safety barrier between a patients blood and a bioartificial liver

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 challenges the development 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 "intelligent membrane" as a safety barrier between the patients blood and cell devices.

Rapid HPLC assay for verapamil and its metabolites: use for application to in vitro studies

An improved method using isocratic reversed phase HPLC is presented for the extraction and rapid determination of verapamil and its main metabolites in microsomal preparations and cell culture media. Possibilities for using the method to estimate cytochrome P450 enzymes in microsomal test systems and hepatocyte cultures are described. The studies show that primary hepatocyte cultures are suitable for studying the metabolism and interactions of pharmaceuticals in vitro and could be superior to microsomal systems in many cases.

Cell sources for bioartificial liver support

The present review discusses hepatocyte sources for a bioartificial liver. Intended requirements for cell sources are for example: synthesis of plasma proteins, detoxification and regulation. The need for highly differentiated hepatocytes is stressed. Furthermore, the gap between this objective on the one hand and the real possibilities as they appear today on the other is shown. Alternatives to primarily isolated hepatocytes are discussed, thereby elucidating the limits of established cell lines. In summary, it is postulated that the results expected from a bioartificial liver, are closely related to the source and type of cells used.

Primary or established liver cells for a hybrid liver? Comparison of metabolic features

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.

Dialysis against a recycled albumin solution enables the removal of albumin-bound toxins

The removal of protein-bound substances of pathogenetic relevance from blood is of therapeutic interest for drug intoxications, renal and liver failure, and metabolic disorders. Current methods using adsorbents are effective but often not specific enough. This work presents an alternative method that enables the dialyzability of albumin-bound toxins from plasma by the use of a high-flux dialyzer (F 60 Fresenius) and an albumin solution circulating on the dialysate side to increase selectively the affinity for albumin-bound toxins. This method resulted in effective removal of unconjugated bilirubin, drugs with a high protein-binding ratio (sulfobromophthalein, theophylline), and a protein-bound toxin (phenol). The additional removal of PBS could extend the applicability of dialysis, for example, to drug intoxications and liver failure or could improve the elimination of protein-bound uremic toxins in chronic renal failure.

A new procedure for the removal of protein bound drugs and toxins

To extend the applicability of dialysis to the removal of albumin bound toxins, a new dialysis procedure was developed. A double sided albumin impregnated high-flux polysulfon dialyzer was used together with a closed loop dialysate compartment with an albumin containing dialysate solution, that was purified on line in a three step process with a charcoal and resin adsorbent, and another dialyzer for a normal dialysis or filtration of the albumin containing dialysate that was then recycled to the albumin impregnated dialyzer. The system effectively removed strongly albumin bound toxins like unconjugated bilirubin or free fatty acids from plasma and blood in vitro and in vivo and therefore could be considered a possible therapeutic means for the treatment of acute liver failure or acute and chronic intoxications with albumin bound toxins, e.g., in drug overdose or chronic renal failure.

Prolonged biochemical and morphological stability of encapsulated liver cells--a new method

In this work a new type of polyelectrolyte complex capsules is introduced as an artificial housing for liver cells. Male Wistar rat hepatocytes were encapsulated using cellulose sulphate and polydimethyldialyllammonium chloride as polyelectrolytes. Amino acid metabolism rate and urea synthesis of the cells increased over the investigation period in contrast to the decrease observed in control monolayer cultures. The encapsulated cells were morphologically characterized. The described procedure represents a sufficient method for the cultivation of living cells in mechanically stable semipermeable microcapsules.

["Elastic osteosynthesis" with autocompression plates of carbon fiber reinforced thermoplastic material]

The problem of atrophic bone that occurs in osteosynthesis employing rigid plates is first depicted. Attempts at fabricating "simirigid" plates, which, however, have so far failed to gain any practical importance are then discussed. The reason for this seems to be that made of duroplastics cannot be molded during the operation and the thermoplastics do not have sufficient strength. The production of semirigid plates made of thermoplastic Polyethersulfon (PES), reinforced with 20% short carbon fibres, results in plates which are made moldable by heating in a small oven, white retaining sufficient static strength, although only limited fatigue strength. Biomechanical examinations revealed that with appropriate dimensioning of the plates, "elastic osteosynthesis" results in less loss of mechanical function of the stabilized bones, so that less atrophy of the bone may be expected. During more pronounced exercise loading, a reversible "springiness" of the fracture results, which might stimulate callus formation and improved stability.

Disruptive behavior: a dietary approach

The effect of particular foods on levels of hyperactivity, uncontrolled laughter, and disruptive behaviors was studied in an 8-year-old autistic boy. The floor of the child's room was taped off into six equal-sized rectangles to measure general activity level. Frequency data were recorded on screaming, biting, scratching, and object throwing. A time-sample technique was used to record data on laughing. Data were gathered during four phases. During an initial 4-day period the child was fed a normal American diet. A 6-day fasting period followed, during which time only spring water was allowed. The third phase lasted 18 days and involved the presentation of individual foods. During the final phase of the study the child was given only foods that had not provoked a reaction in the third phase. Results showed that foods such as wheat, corn, tomatoes, sugar, mushrooms, and dairy products were instrumental in producing behavioral disorders with this child.