Establishment of hyperoxic cell culture system for predicting drug-induced liver injury: reducing accumulated lipids in hepatocytes derived from chimeric mice with humanized liver

- Drug-induced liver injury (DILI) is a major adverse reaction. Species-specific differenc-es between humans and laboratory animals make it difficult to establish evaluation models that can accu-rately predict DILI in the preclinical phase. Chimeric mice with humanized liver are potential predictive models for understanding DILI. Chimeric mice generated by transplanting human hepatocytes into uroki-nase-type plasminogen activator/severe combined immunodeficient mice are known to develop fatty liver and show lipid accumulation in isolated hepatocytes. It is speculated that the lipids accumulated in hepat-ocytes may interfere with DILI assessment. It is known that normal 20% oxygen culture conditions do not meet oxygen demand because oxygen consumption rate is higher than the oxygen supply rate. Therefore, we predicted that hyperoxic cultures could induce hepatocyte function and reduce accumulated lipids. A culture of chimeric mouse hepatocytes in 40% oxygen showed reduced intracellular lipid and triglycer-ide levels compared to those cultured in 20% oxygen on days 7 and 10. In addition, fatty acid (3-oxidation (FAO) activity increased from day 7 under 40% oxygen conditions. On the other hand, FAO activity increased on day 10 under 20% conditions. Microarray and Ingenuity Pathway Analysis showed that lipid metabolism-related pathways were downregulated under 40% oxygen conditions for 7 days, suggesting the involvement of several mechanisms in decreasing lipid levels and increasing FAO. Furthermore, some pathways related to cellular function and maintenance were upregulated under 40% oxygen conditions for 7 days. In conclusion, chimeric mouse hepatocytes cultured under hyperoxic conditions may be useful for predicting DILI.