The development of a liver support system for the treatment of patients with fulminant hepatic failure and as a bridge to liver transplantation is a major challenge. Many early attempts focussed on broad detoxification based on the assumption that liver failure could be reversed if the associated toxins were removed from the circulation of the patient. Although improvement of the neurologic status of the patients has been reported, none achieved long term survival. It was therefore concluded that an effective liver support system should be able to perform the liver's multiple synthetic and metabolic functions including detoxification and excretion . The most logical approach to this problem is the introduction of active functioning hepatocytes. Different bioreactor systems are currently under investigation. However, an ideal BAL system has not yet been invented. We deviced a novel bioreactor (patent pending) which allows individual perfusion of high density cultured hepatocytes with low diffusional gradients, thereby more closely resembling the conditions in the intact liver lobuli. The bioreactor consists of a spirally wound nonwoven polyester matrix, i.e. a sheet-shaped threedimensional framework for hepatocyte immobilization and aggregation, and of integrated hydrophobic hollow-fibre membranes for oxygen supply and CO2 removal. The bioreactor is seeded with 220.106 freshly isolated porcine hepatocytes cultured at 20.106 viable cells/ml. Medium (plasma in vivo) is perfused through the extrafibre space and therefore in direct hepatocyte contact. In vitro evaluation of the BAL showed that hepatocytes contained cytoarchitectural characteristics as found in vivo and an even distribution of small hepatocyte aggregates ( < 75 fm) throughout the three-dimensional matrix with sufficient space between the aggregates for individual cell perfusion. The biochemical performance of the bioreactor remains stable over the investigated period of four days. On day one and day four galactose elimination was 28.4 + 2.3 fg/106 cells, urea synthesis was 1.9 + 0.4 fg/106 cells, and lidocaine metabolism 39.2 + 3 .2 fg/106 cells. Low lactate/pyruvate ratios and constant pH values indicated optimal oxygenation and CO2 exchange by the integrated oxygenator. Metabolism of a wide range of amino acids as well as protein secretion was documented. In the first in vivo experiments in rats with acute liver failure due to complete liver ischemia (porta caval shunt plus ligation of the hepatic artery) survival time in controls with only supportive therapy was 5 + 1 hr and in a second control group treated by plasmapheresis and a BAL without cells in the extracorporeal circuit 6 i 1.5 hr (n=7). The first rats with complete liver ischemia treated by our BAL in the extracorporeal circuit survived 11 and 12 hrs respectively, a highly significant improvement.
The next step in the development of a satisfactory BAL for human application will be evaluation of the BAL in a bigger animal experimental setting. In collaboration with the group of Dr. Calise in Napoli we will treat pigs with complete liver ischemia by a BAL scaled up for the pigs circulation. Our expertise for the group in Italy will be the application of the upgraded BAL, the knowledge of pig hepatocyte isolation and plasmapheresis. The pig experiments are essential as a bridge to human application. Since the group of Dr. Calise has already sufficient experience with the liver ischemia model in pigs our collaboration can be very fruitful. Production of a scaled up BAL for the pig will be performed by The Spectrum Companies La Cadena Drive, Laguna Hills in the United States. The price of these BAL's will be $ 300 to 400 per device. Other expences of this in vivo study will be the costs of the pigs and the plasmapheresis apparatus.
Fields of science
- engineering and technologyenvironmental biotechnologybioremediationbioreactors
- natural sciencesbiological sciencesbiochemistrybiomoleculesproteins
- natural scienceschemical sciencesorganic chemistryamines
- medical and health sciencesclinical medicinetransplantation
- medical and health sciencesmedical biotechnologytissue engineeringbioartificial liver
Call for proposalData not available
Funding SchemeRGI - Research grants (individual fellowships)
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