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Hepatocyte cultivation in bioreactors for hybrid liver support systems is possible under two conditions: attached to a substrate like membranes or microcarriers or in suspension culture. To compare the ammonia metabolism of hepatocytes cultivated under these two conditions, cultures of primary seeded rat hepatocytes were cultivated either attached to collagen coated tissue culture plastic or as a suspension culture. During the time course of culture, the ability of hepatocytes to reduce the ammonia content of the medium decreased in both adhesion and suspension cultures, though to different extents. In suspension cultures, ammonia content was reduced from 350 microM to about 100 microM (day 4) and to about 180 microM (day 6). No significant reduction was seen on day 8 of culture. In contrast, hepatocytes attached to collagen coated dishes remained viable and functional for at least 8 days after plating, reducing ammonia content from 350 microM to 70 microM (day 4), 90 microM (day 6) and 180 microM (day 8). The period of useful metabolism of hepatocytes in bioreactors for hybrid liver support systems appears to depend on the culture conditions.

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Fourteen membranes out of cellulose (CuprophanR), polyamide and polypropylene were compared in a cytocompatibility test using the cytokinetics and cytomorphology of primary hepatatocytes as parameters. Additionally, the impact of coating the membranes with collagen or fibronectin was investigated. Hepatocytes were not able to attach in acceptable amounts on investigated cellulose membranes. On polyamide and polypropylene membranes a sufficient cell seeding was possible. Coating with collagen or fibronectin improves the attachment and spreading on all membranes. Differences between collagen and fibronectin were detected, observing the morphology of the cells: on collagen, most of the cells spread, whilst on fibronectin, most of the cells spread and flattened polygonally. If the adhesion of hepatocytes prolongs their metabolic function, a large adhesion surface in bioreactors is necessary. To reach a high surface area for cell adhesion in bioreactors one possibility is the use of polyamide and polypropylene membranes.