EXTENDED LIVER-SPECIFIC FUNCTIONS OF PORCINE HEPATOCYTE SPHEROIDS ENTRAPPED IN COLLAGEN GEL

The potential use of porcine hepatocytes in a bioartificial liver devi ce requires large quantities of viable and highly active cells. To fac ilitate the scaling up of the system, liver specific activities of hep atocytes should be maximized. One way of enhancing the specific activi ties is to cultivate hepatocytes as multicellular spheroids. Freshly i solated porcine hepatocytes form spheroids when cultivated in suspende d cultures. These spheroids exhibit higher activities for a number of liver specific functions compared to hepatocytes cultivated as monolay ers. However, these activities decreased in a few days in culture. Ent rappment of spheroids in collagen gel sustained their metabolic activi ties at a stable level over 21 days. Production of albumin and urea by spheroid hepatocytes entrapped in collagen gels were 2 to 3 times hig her than those by freshly isolated single cells. P-450 activity was de monstrated by metabolism of lidocaine to its main metabolite, monoethy lglycinexylidide. Phase II drug metabolism was demonstrated by glucuro nidation of 4-methylumbelliferone. This work shows that porcine hepato cyte spheroids entrapped in collagen maintain differentiated functions for an extended time period. Such hepatocyte spheroid entrappment sys tem may facilitate the development of a bioartificial liver support de vice.