Rapid formation of hepatic organoid in collagen sponge by rat small hepatocytes and hepatic nonparenchymal cells

Background/Aims: Hybrid bioartificial liver devices supporting a large mass of metabolically active hepatocytes are thought to be necessary for the successful treatment of patients with severe acute liver failure. However, it is very difficult to obtain cells with both growth activity and differentiated functions. Rat small hepatocytes (SHs), which are hepatic progenitor cells, can differentiate into mature hepatocytes and reconstruct a hepatic organoid by interacting with hepatic nonparenchymal cells (NPCs). Methods: Colonies of SHs were collected and replated on a collagen sponge. Hepatic functions were examined by ELISA, immunoblotting, and Northern blotting. Cells in the sponge were characterized by immunocytochemistry and transmission electron microscopy. Urea synthesis was measured and metabolization of fluorescein diacetate was examined. Results: SHs could proliferate and expand to form a hepatic organoid in the sponge. Albumin secretion and other hepatic protein production of the cells in the sponge increased with time in culture and the amounts were much larger than for those obtained from cells grown on dishes. Morphologically and functionally differentiated hepatocytes were observed and some CK19-positive cells formed duct-like structures within the sponge. Excretion of fluorescein was observed in bile canaliculi. Conclusions: Hepatic organoids can be rapidly reconstructed in a collagen sponge by rat SHs and NPCs.