RAPID FORMATION OF MULTICELLULAR SPHEROIDS OF ADULT-RAT HEPATOCYTES BY ROTATION CULTURE AND THEIR IMMOBILIZATION WITHIN CALCIUM ALGINATE

Tyrosine aminotransferase (TAT) induction and albumin secretion abilit ies were examined in rat hepatocytes immobilized within calcium algina te; the immobilized hepatocytes lost these abilities within a week. An attempt was then made to immobilize multicellular spheroids of hepato cytes for the purpose of stabilizing the liver functions. Although it takes at least 4 days to form spheroids in the conventional method usi ng monolayer-cultured cells, in this study we developed a new method f or rapid spheroid formation. Isolated hepatocytes were seeded into a p olystyrene dish and incubated on a rotary shaker. Hepatocytes started to aggregate after 6 h of the rotation culture, and spheroids approxim ately 100 mu m in diameter formed within 24 h. The immobilized spheroi ds had higher TAT induction and albumin secretion abilities, which wer e maintained for a longer time, than the immobilized nonaggregated cel ls. Further stabilization was observed in immobilized heterospheroids formed in the presence of nonparenchymal liver cells. This method for the rapid formation of spheroids consisting of hepatocytes and nonpare nchymal liver cells could be utilized in the construction of a bioarti ficial liver support system.