Efficacy of Immunoadsorbent Devices for Maintaining Hepatic Function in Ex Vivo Direct Xenogenic Hemoperfusion

We have developed a new system for direct xenogenic hemoperfusion of a bioartificial liver support system adopting two types of immunoadsorbent devices. In this study, we compared the efficacy of each immunoadsorbent device in maintaining porcine hepatocyte function during 3 h perfusion treatment in a canine liver failure model. Suppression of humoral immunity by the immunoglobulin adsorber prevented immunogenic hepatocyte injury more effectively, and the system showed higher hepatic function when compared with suppression of cell-mediated immunity by the leukocyte adsorber. However, single use of immunoglobulin adsorber was less effective in reducing patients' systemic ammmonia levels and modulating the Fischer's ratio compared with the case of combined use of both immunoadsorbent devices. These results suggest that suppression of humoral immunity was of primary importance in preventing immunogenic hepatocyte injury, however the adsorption of leukocytes may have a synergic effect on maintaining hepatocyte function in direct xenogenic hemoperfusion.

Treatment of acute liver failure in pigs reduces hepatocyte function in a bioartificial liver support system

Several different types of bioartificial liver (BAL) support systems have been developed to bridge patients suffering from acute liver failure (ALF) to transplantation or liver regeneration. In this study we assessed the effects of ALF plasma on hepatocyte function in the BAL system that has been developed in our center. Pigs (40-60 kg) were anaesthetised and a total hepatectomy was performed. Cells were isolated from the resected livers and were transferred to the bioreactor of the BAL system. Twenty hours after cell isolation, hepatocytes in the BAL were tested for cell viability and functional activity by using a recirculating test medium in which assessment of LDH leakage, ammonia clearance, urea synthesis, 7-ethoxycoumarin O-deethylase (ECOD) activity and pseudocholine esterase production was performed. Subsequently, two groups were studied. In one group (I, n=5), the cell-loaded bioreactor was used to treat the donor pig, rendered anhepatic, for 24 hours. In the second group (II, n=5) the bioreactor was cultured for 24 h and served as a control. After 24 hours treatment or culturing, the cell viability count and functional activity tests were repeated. The results show that hepatocytes in the BAL remained viable after 24 h treatment of anhepatic pigs, as shown by the LDH release and pseudocholine esterase production. However, metabolic functions such as ammonia clearance, ECOD and urea synthesis were reduced after 24 h exposure of hepatocytes to autologous ALF plasma, whereas these functions were unaltered after 24 h culturing of the cells in the bioreactor.

Optimization of rat hepatocyte culture in citrated human plasma

BACKGROUND

Maintenance of liver-specific functions in hepatocyte cultures during plasma exposure is critical for the clinical application of bioartificial liver assist systems. Sodium citrate is a common anticoagulant but has been shown to be cytotoxic to hepatocytes. We have tested the effect of various supplements on the viability and function of adult primary rat hepatocytes exposed to citrated plasma.

MATERIALS AND METHODS

Freshly isolated rat hepatocytes were cultured in the collagen gel sandwich configuration in culture medium for 6 days followed by exposure to citrated human plasma with various supplements for 1 week. Controls were left in culture medium throughout. Viability and synthetic functions were evaluated.

RESULTS

Hepatocytes exposed to unsupplemented citrated plasma lost significant viability and function within the first 2 days. Cells cultured in plasma supplemented with a fivefold concentrate of standard hepatocyte culture medium maintained urea (1. 2-2.1 micromol/day/10(6) cells) and albumin (51-62 microg/day/10(6) cells) synthesis rates equal to or higher than those of controls. Among the various components of the concentrated medium supplement, calcium chloride (1.8 mM), magnesium sulfate (0.8 mM), amino acids (fourfold Basal Medium Eagle amino acids including 4 mM glutamine), and glucagon (14 ng/ml) were found to be essential in maintaining urea synthesis. Maintenance of a high albumin synthesis rate also required the addition of hydrocortisone (7.5 microg/ml) and insulin (0.5 U/ml).

CONCLUSIONS

Appropriate metabolic and hormonal supplementation of citrated human plasma prevents its cytotoxic effects and may be used in conjunction with in vivo use of bioartificial liver assist systems.