| Abstract: | Interindividual differences in hepatic metabolism, which are mainly due to genetic polymorphism in its gene, have a large influence on individual drug efficacy and adverse reaction. Hepatocyte-like cells (HLCs) differentiated from human induced pluripotent stem (iPS) cells have the potential to predict interindividual differences in drug metabolism capacity and drug response. However, it remains uncertain whether human iPSC-derived HLCs can reproduce the interindividual difference in hepatic metabolism and drug response. We found that cytochrome P450 (CYP) metabolism capacity and drug responsiveness of the primary human hepatocytes (PHH)-iPS-HLCs were highly correlated with those of PHHs, suggesting that the PHH-iPS-HLCs retained donor-specific CYP metabolism capacity and drug responsiveness. We also demonstrated that the interindividual differences, which are due to the diversity of individual SNPs in the CYP gene, could also be reproduced in PHH-iPS-HLCs. We succeeded in establishing, to our knowledge, the first PHH-iPS-HLC panel that reflects the interindividual differences of hepatic drug-metabolizing capacity and drug responsiveness.Drug-induced liver injury (DILI) is a leading cause of the withdrawal of drugs from the market. Human induced pluripotent stem cell (iPSC)-derived hepatocyte-like cells (HLCs) are expected to be useful for the prediction of DILI in the early phase of drug development. Many groups, including our own, have reported that the human iPS-HLCs have the ability to metabolize drugs, and thus these cells could be used to detect the cytotoxicity of drugs that are known to cause DILI (1, 2). However, to accurately predict DILI, it will be necessary to establish a panel of human iPS-HLCs that better represents the genetic variation of the human population because there are large interindividual differences in the drug metabolism capacity and drug responsiveness of hepatocytes (3). However, it remains unclear whether the drug metabolism capacity and drug responsiveness of human iPS-HLCs could reflect those of donor parental primary human hepatocytes (PHHs). To address this issue, we generated the HLCs differentiated from human iPSCs which had been established from PHHs (PHH-iPS-HLCs). Then, we compared the drug metabolism capacity and drug responsiveness of PHH-iPS-HLCs with those of their parental PHHs, which are genetically identical to the PHH-iPS-HLCs.Interindividual differences of cytochrome P450 (CYP) metabolism capacity are closely related to genetic polymorphisms, especially single nucleotide polymorphisms (SNPs), in CYP genes (4). Among the various CYPs expressed in the liver, CYP2D6 is responsible for the metabolism of approximately a quarter of commercially used drugs and has the largest phenotypic variability, largely due to SNPs (5). It is known that certain alleles result in the poor metabolizer phenotype due to a decrease of CYP2D6 metabolism. Therefore, the appropriate dosage for drugs that are metabolized by CYP2D6, such as tamoxifen, varies widely among individuals (6). Indeed, in the 1980s, polymorphism in CYP2D6 appears to have contributed to the withdrawal of CYP2D6-metabolized drugs such as perhexiline from the market in many countries (7). If we could establish a panel of HLCs that better represents the diversity of genetic polymorphisms in the human population, it might be possible to determine the appropriate dosage of a drug for a particular individual. However, it is not known whether the drug metabolism capacity and drug responsiveness of HLCs reflect the genetic diversity, including SNPs, in CYP genes. Therefore, in this study we generated HLCs from several PHHs that have various SNPs on CYP2D6 and then compared the CYP2D6 metabolism capacity and responses to CYP2D6-metabolized drugs between the PHH-iPS-HLCs and parental PHHs.To this end, PHHs were reprogrammed into human iPSCs and then differentiated into the HLCs. To examine whether the HLCs could reproduce the characteristics of donor PHHs, we first compared the CYP metabolism capacity and response to a hepatotoxic drug between PHHs and genetically identical PHH-iPS-HLCs (12 donors were used in this study). Next, analyses of hepatic functions, including comparisons of the gene expression of liver-specific genes and CYPs, were performed to examine whether the hepatic characteristics of PHHs were reproduced in the HLCs. To the best of our knowledge, this is the first study to compare the functions between iPSC-derived cells from various donors and their parental cells with identical genetic backgrounds. Finally, we examined whether the PHH-iPS-HLCs exhibited a capacity for drug metabolism and drug responsiveness that reflect the genetic diversity such as SNPs on CYP genes. |
