Size-regulation and biochemical activities of the multicellular spheroid composed of rat liver cells.

It was reported that cell-sheets composed of rat liver cells could be obtained by using a collagen-conjugated thermo-responsive polymer, poly-N-isopropyl acrylamide, as a cell substratum and they were then able to transform into multicellular spheroids in the hydrophobic dish. In this study, we succeeded in easily obtaining the cell-sheets with the intended size by using the etched substratum. Biochemical analyses of spheroids derived from cell-sheets with areas of 0.2, 0.5 and 2.5 cm2 were carried out. Each cell-sheet rapidly aggregated at the same rate and finally turned into a multicellular spheroid within 5 days after the detachment. However, both decreases of DNA and LDH contents in cell-sheets with an area of 2.5 cm2 within 24 hr after the detachment were more obvious than in the others, respectively. It is tempting to speculate from these data that the vital spheroids with the desired size can be easily obtained by using our new method.