The investigators then generated reporter HEALs by transducing lentiviruses expressing firefly luciferase under the control of the albumin promoter into HEP/FIB+TMNK1 cultures, and the encapsulated HEALs were implanted at an intraperitoneal (IP) site in athymic nude mice. Bioluminescence

imaging showed that the IP site could support the HEALs. Albumin promoter activity was maintained for several weeks, and human albumin and alpha-1-antitrypsin were secreted in the mouse sera. HEALs were reproducibly engrafted (91.6% of 131 mice transplanted) and microcomputed GSK2118436 purchase tomography angiography of extracted HEALs confirmed host vessel recruitment to, around, and inside the implant. HEAL-humanized mice could be rapidly and reproducibly generated from fresh and also cryopreserved hepatocytes. Moreover, unlike humanized chimeric mouse models, HELAs were maintained in immunocompetent and non-liver-injury mice for up to 8 days. HEAL-humanized mice expressed various human CYPs. Because major drug metabolites can be missed in standard animal models because of differences in drug-metabolism pathways among species, the investigators assessed whether the mice

could be used for the identification of major metabolites. Debrisoquine (DB) is a CYP2D6 substrate converted to 4-hydroxydebrisoquined (4-OHDB) in humans, but not in mice. 2 In fact, HEAL-humanized mice metabolized DB to 4-OHDB. More important, CYP2D6 is responsible for the metabolism of 25% of known drugs and its highly polymorphic nature contributes to significant interindividual this website variability. 15 The investigators prepared HEALs from two donors with different Fer-1 order levels of CYP2D6 and compared the ability of mice harboring the HEALs to metabolize DB. Mice with HEALs from the donor with lower levels of CYP2D6 metabolized DB less efficiently than those with HEALS from the donor with higher expression levels. Thus, HEAL-humanized mice can be used to detect breakdown products of drugs, which are missed

in standard mouse models. Drug-drug interactions are critical determinants of drug efficacy and safety because of the potential for drugs to alter the therapeutic or toxic effect of concomitantly administered compounds. Finally, the investigators explored the utility of the humanized mice for modeling toxic drug-drug interactions in vivo. Mice were first given rifampin (RIF) and then a therapeutic dose of acetoaminophen (APAP), a hepatotoxin at a high dose because of the CYP-mediated formation of N-acetyl-p-benzoquinone (NAPQI). 16 Although mice were resistant to RIF+APAP as a result of species-specific drug-drug interaction and HEAL-humanized mice given either RIF and APAP alone showed no sign of liver injury, HEAL-humanized mice given RIF+APAP showed evidence of human hepatocellular injury. Thus, HEAL-humanized mice can be used for screening hepatotoxic drug-drug combinations and doses invivo.