RECONSTRUCTION OF LIVER-TISSUE IN-VITRO - GEOMETRY OF CHARACTERISTIC FLAT BED, HOLLOW-FIBER, AND SPOUTED BED BIOREACTORS WITH REFERENCE TO THE IN-VIVO LIVER

Bioreactors currently being developed for hybrid artificial livers var y greatly with respect to their microenvironment. The specific archite cture modifies the relationship parenchymal and nonparenchymal cells h ave with the exchange surfaces of the bioreactor. Most designs are eit her based on hollow fiber, spouted bed, or flat bed devices. This dive rsity is contrasted by the uniform and unique organization of the in v ivo liver. The liver cells are arranged as plates and both sinusoidal surfaces of the hepatocytes are enclosed within the matrix of the spac e of Disse. In this study we intended to define the in vivo liver tiss ue characteristics in a manner useful for an organotypical approach to hepatic tissue engineering. Transmission electron microscopy of an in vivo liver was utilized to describe these ratios. The ratios defined in this study are based on the constant hepatocellular expression of t wo sinusoidal surfaces. A relationship is established between the expr ession of the sinusoidal surfaces and their use as attachment and exch ange surfaces inside a bioreactor. The presence of biliary surfaces an d nonparenchymal cell surfaces is compared. The functional relevance o f an in vivo like extracellular matrix geometry for oxidative biotrans formation of primary hepatocytes in vitro was studied using the two mo del drugs cyclosporin and rapamycin. The generation of the hydroxylate d cyclosporin metabolites AM 9 and AM 1 and four rapamycin metabolites was analyzed by high performance liquid chromatography (HPLC). It is shown that the cell-specific biotransformation rates at 1 week in cult ure in matrix overlayed hepatocytes was 5-10 times that of hepatocytes without matrix overlay. Bilaminar membrane (BLM) bioreactors were use d to reconstruct extracellular matrix geometry, three-dimensional cell plates, and sinusoidal analogs in between cell plates.