Development and characterization of a hybrid bioartificial liver using primary hepatocytes entrapped in a basement membrane matrix

For the development of a bioartificial liver (BAL) support device, it is most important to establish highly differentiated liver cells cultured at high density. When rat hepatocytes were cultured on a basement membrane matrix, Engelbreth-Holm-Swarm (EHS) gel, their rates of albumin secretion were very high, as measured by ELISA, and these high rates were maintained for more than three weeks of culturing. This level of activity greatly exceeded that of hepatocytes cultured on a plastic substratum, poly-N-p-vinylbenzyl-D-lactonamide (PVLA), on a single layer of collagen, or in a collagen sandwich culture. In an in vitro perfusion experiment. rat hepatocytes rapidly and completely removed ammonia from Eagle's MEM supplemented with 0.2 mM NH4Cl, although ammonia levels of the medium serially increased in modules containing HepG2 cells. A hybrid liver support system was developed and consisted of plasma perfusion through porous hollow fiber modules inoculated with 10 billion porcine hepatocytes entrapped in EHS gel. This system was applied to pigs with ischemic liver failure 8 hr after creation of a portocaval shunt and hepatic devascularization, In animals treated with the BAL support system, blood bicarbonate levels were increased immediately after treatment, and hemodynamic stability was improved. In control pigs, on the other hand, blood bicarbonate levels and blood pressure remained low. Plasma levels of ammonia and lactate decreased in pigs treated with the BAL device, but not in control animals. These results indicate that primary hepatocytes outperform HepG2 cells as a source of biotransformation functions in a BAL system and that the use of a BAL support device in combination with a hollow fiber module and hepatocytes entrapped in EHS gel has potential advantages for clinical use in patients with fulminant hepatic failure.