Recently, a novel culture system consisting of primary hepatocytes structured over a network of endothelial cells on the Engelbreth-Holm-Swarm (EHS) gel has been reported. This in vitro liver model on the EHS gel (IVLEHS) has been shown to maintain the expression of hepatic genes and their functional activity. Moreover, the IVLEHS was more sensitive to xenobiotics than hepatocyte monocul-tures, suggesting the potential utility of this culture system for compound hepatotoxicity screening. However, the effect of this three-dimensional structure formation on the cellular metabolic profile of hepatocytes in the IVLEHS is not well understood. To address this concern, we performed metabolome analysis using capillary electrophoresis-time of flight mass spectrometry. Between the IVLEHS and mono-cultured hepatocytes on the EHS gel, there was no significant difference in the levels of metabolites of the urea cycle and the tricarboxylic acid cycle, essential amino acids, and adenylate energy charge (AEC) which is an important indicator of cellular energy status. On the other hand, acetaminophen-dependent decrease of the AEC in the IVLEHS was greater than that in the monoculture, suggesting the higher sensitivity of IVLEHS to acetaminophen-induced hepatotoxicity which is caused by metabolic activation of this drug. Further analysis showed that the levels of taurocholate, one of the major conjugated bile acids, were higher in the IVLEHS than in the monoculture. Considering that the construction of the IVLEHS did not seem to disturb the major cellular metabolism, our findings would strengthen the concept that IVLEHS would have beneficial effects on the maintenance of hepatic functions.
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