Application of circulatory flow bioreactor for long-term and large-scale culture of glutamine synthetase transduced CHO cells and its ammonia removal activity with an aim of development for a bioartificial liver assist system

Abstract

Glutamine synthetase-transduced Chinese hamster ovary (GS-CHO) cells were cultured in a circulatory flow bioreactor for 28 days. The bioreactor inoculated with 4.72×108 of GS-CHO cells was kept at 37°C and supplied with air, CO2, O2, and glutamine-free RDF culture medium containing 5% fetal bovine serum, 2.3mM of ammonia, and 1.0mM of glutamate. Since GS-CHO cells synthesize glytamine from ammonia and glutamate, the ammonia concentration in the culture medium was decreased corresponding to the cell growth. The clearance rate of added ammonia showed that the ammonia removal activity was equivalent to that of 1.25×108 porcine hepatocytes. Amino acid analysis showed a peak of glutamine synthesis that was not found in the original medium. The ammonia concentration in the culture medium returned to the original level 24 days after the start of culture, suggesting the cells went into a stationary stage. The number of cells in the bioreactor at the end of the culture was 9.64×109, and the cells were uniformly distributed throughout the glass fiber cell matrix. These data suggest that the circulatory flow bioreactor system with recombinant cells is applicable for a bioartificial liver assist unit to remove toxic substances in the blood of a patient whose detoxification has been injured by hepatic failure.