Formation of rat hepatocyte spheroids on agarose

The hepatocyte spheroid formation on the Primaria™ dish (PM) occurred as a result of cell migration, adhesion, and shape changes. On the other hand, hepatocytes plated on 1.5% agarose-coated dishes did not attach to the dishes. The formation of spheroids on the agarose-coated dishes was significantly more rapid than that on the PM ones. The PA/plasmin system plays an important role in the process of hepatocyte spheroid formation on PM dishes, and thus the spheroid formation on PM is inhibited by plasmin inhibitors. Nevertheless, these inhibitors did not show any effect on the spheroid formation on agarose-coated dishes. PA activities could be detected in the conditioned medium harvested from the cells cultured on PM dishes, but not in that from those cultured on the agarose-coated dishes. In summary, we have established a novel method to form hepatocyte spheroids by using agarose-coated dishes, in which some mechanism(s) independent of the PA/plasmin system is involved in their formation. The differentiated hepatocyte-specific functions of the spheroids formed on the agarose-coated dishes were expressed to a quite lesser degree than those formed on the PM ones, suggesting that the processes involved in spheroid formation are important for the expression of spheroid functions.