Hepatocyte-like cells differentiated from human induced pluripotent stem (iPS) cells are of great interest for applications in pharmacological research. For drug metabolism testing, commercially available hepatocytes derived from human iPS cells are generally recommended to be used 1 week after seeding on plates. In this study, however, after 3-4 weeks of culture according to the manufacturer's instructions, human cytochrome P450 (P450) 2C9- and 2C19-dependent diclofenac 4'-hydroxylation and omeprazole 5-hydroxylation activities of the iPS-derived hepatocytes had significantly increased above the activities at 1 week and had reached levels similar to those in HepaRG cells, a human hepatocyte-like cell line. This increase in activities was associated with increasing P450 2C9 and 2C19 mRNA levels. Human P450 3A4-dependent midazolam 1'/4-hydroxylation activities in the iPS-derived hepatocytes were also enhanced after 3 weeks of culture, but the levels were low compared with those of HepaRG cells. These results indicate that the induction of mRNA of typical P450s in human iPS-derived hepatocyte-like cells occurred after 3 weeks of normal culture conditions. However, the induction levels varied considerably depending on the pregnane X receptor pathway and/or the P450 isoform. Our findings that the hepatic functions of human iPS-derived hepatocytes were enhanced by 3 weeks of simple culture could facilitate the use of these cells for drug metabolism and toxicity testing.
Keywords: HepaRG cells; P450 2C19; P450 2C9; P450 3A4; P450 3A5; iPSC-derived hepatocytes.