Extended expression of liver functions of hepatocytes in collagen-contained cell aggregates (cell packs).

The functions of hepatocytes under the collagen-contained cell aggregate (cell pack) conditions were studied using liver-specific protein synthesis. Freshly isolated murine hepatocytes were suspended in the medium containing collagen and centrifuged, and the resultant cell masses were cultured on the porous membranes floating on the medium. In these cultures cells were attached to each other three-dimensionally with collagen present in the intercellular spaces. Cultured hepatocytes in the cell pack maintained high and stable activity in the expression of their functions for more than 2 weeks, even when cultured with the medium lacking any hormones and serum, whereas hepatocytes in monolayer cultures lost their functions within a week. Similarly, when the cell packs of rat hepatocytes were transplanted into rat spleens, they could retain viability in the form of cell aggregate with the expression of liver-specific albumin mRNA at a higher level than in the transplanted cell suspensions. The lifespan and the initial expression level of hepatocellular functions in culture were similar to that of the cell pack in cell aggregates without collagen and in cellular monolayers on the collagen gel respectively. It was concluded that the condition where cells are in contact with each other has an important role in the expression of hepatocellular functions and collagen present in the intercellular spaces enhances the functional levels.