Effect of extracellular matrix composition on the expression of glutathione S-transferase isoenzymes in organotypical hepatocyte cultures

Collagen gel sandwich and immobilization cultures of hepatocytes, using hyd rated collagen type I as extracellular matrix (ECM), have been proposed as long-term in vitro models in pharmacotoxicology. The in vivo ECM compositio n in the space of Disse is. however, much more complex. As a differentiated hepatocyte phenotype is thought to be highly dependent on ECM composition and biophysical characteristics, we modulated the ECM to mimic the bt vivo situation. Moreover, commercially available collagen type I (Boehringer-Ing elheim) was compared to the one prepared in the laboratory from rat tails. ECM composition had no effect on albumin secretion or hepatocyte morphology in both collagen gel sandwich and immobilization cultures. Total, Alpha an d Mu class GST activities in organotypical cultures with a complex or a sim ple collagen type I ECM were similar. The Pi class GST activity increased a s a function of culture time in all culture models. Thus, mimicking the in vivo composition of the ECM did not improve the changes in GST expression t hat were observed in simple collagen gel cultures. The collagen type I matr ix is therefore assumed to confer sufficient protection to help the hepatoc ytes to maintain their differentiated phenotype to a certain extent. Moreov er, we hypothesize that the collagen gel matrix may act as a scaffold to ke ep newly synthesized ECM components in the proximity of the basolateral sur faces of the hepatocytes. (C) 1999 Elsevier Science Ltd. All rights reserve d.