An Improved Oxygenation Hollow Fiber Bioreactor for the Cultivation of Liver Cells

Abstract

Bioartificial livers represent a potential alternative to organ transplantations which are often limitated by a shortness of donor organs. Consequently, it is of great importance to cultivate the liver cells appropriately. The metabolic requirements of hepatocytes, particularly the high rates of oxygen consumption, place stringent demands on the bioreactor system. Until now liver cells were cultivated either in the sandwich configuration, as spheroids or in special hollow fiber systems. In this project we designed a hollow fiber bioreactor (HFB) with diffusion oxygenation membranes. The hollow fibers have a distance of 200 μm. The cells are placed in the extrafibrous space on the fibers. Through these fibers the oxygen supply is supported. Alternatively, we used bioreactors with fibers for oxygen and warmth supply. Medium is perfused through the extrafiber space and therefore in direct cell contact. The bioreactor offers different advantages. Because of the diffusion membranes a deposition of material on the membrane surface and in its pores is excluded. We studied the influence of the bioreactor technique with primary porcine hepatocytes with a high cell density of 25 mio. cells / ml. Moreover, we cultivated a human hepatocyte cell line (HepG2) in the bioreactor. Various parameters were investigated over a time span of three weeks. This includes urea synthesis, lactate formation, glucose elimination, albumin synthesis, oxygen level and pH. Furthermore, the metabolites of the diazepam decomposition were measured. The biochemical performance of the bioreactor remained stable over the investigated period of time. This results demonstrate that liver cells preserve their viability and primary metabolism in the oxygenation HFB over the complete period of study.