Thalidomide-induced limb abnormalities in a humanized CYP3A mouse model.

Yasuhiro Kazuki,Shoko Takehara,Kanako Kazuki,Tetsuya Kamataki,Ryo Ohta,Masaharu Akita,Hiroshi Yamazaki,Mitsuhiko Osaki,Daisuke Satoh,Mitsuo Oshimura,Kaoru Kobayashi,Satoshi Abe

doi:10.1038/srep21419

Abstract

Thalidomide is a teratogen in humans but not in rodents. It causes multiple birth defects including malformations of limbs, ears, and other organs. However, the species-specific mechanism of thalidomide teratogenicity is not completely understood. Reproduction of the human teratogenicity of thalidomide in rodents has previously failed because of the lack of a model reflecting human drug metabolism. In addition, because the maternal metabolic effect cannot be eliminated, the migration of unchanged thalidomide to embryos is suppressed, and the metabolic activation is insufficient to develop teratogenicity. Previously, we generated transchromosomic mice containing a human cytochrome P450 (CYP) 3A cluster in which the endogenous mouse Cyp3a genes were deleted. Here, we determined whether human CYP3A or mouse Cyp3a enzyme expression was related to the species difference in a whole embryo culture system using humanized CYP3A mouse embryos. Thalidomide-treated embryos with the human CYP3A gene cluster showed limb abnormalities, and human CYP3A was expressed in the placenta, suggesting that human CYP3A in the placenta may contribute to the teratogenicity of thalidomide. These data suggest that the humanized CYP3A mouse is a useful model to predict embryonic toxicity in humans.

Highlights

Thalidomide has been previously used as a sedative and to treat morning sickness in pregnant women
In this mouse strain with fully humanized CYP3A genes [designated as CYP3A-human artificial chromosome (HAC)/ Cyp3a knock out (KO)] reproduced the kinetics of triazolam metabolism catalysed by CYP3A, CYP3A-mediated mechanism-based inactivation effects, and the formation of fetal-specific CYP3A7-mediated metabolites of dehydroepiandrosterone observed in humans
To test whether human CYP3A or mouse Cyp3a enzymes were related to species-specific teratogenicity, thalidomide was administered to pregnant mice or added to culture medium of the whole-embryo culture (WEC) system

Summary

Thalidomide n

We believed that two issues prevented reproduction of embryonic teratogenicity in a rodent model. The first issue was the lack of a human metabolic enzyme-expressing animal that demonstrated human-specific teratogenicity at the embryonic stage. To address this issue, we generated transchromosomic (TC) mice containing a single copy of a 700 kb genomic region with CYP3A4, CYP3A5, CYP3A7, and CYP3A43 genes, via a chromosome-engineering technique in which the endogenous mouse Cyp3a genes were deleted[15]. We generated transchromosomic (TC) mice containing a single copy of a 700 kb genomic region with CYP3A4, CYP3A5, CYP3A7, and CYP3A43 genes, via a chromosome-engineering technique in which the endogenous mouse Cyp3a genes were deleted[15] In this mouse strain with fully humanized CYP3A genes [designated as CYP3A-human artificial chromosome (HAC)/ Cyp3a knock out (KO)] reproduced the kinetics of triazolam metabolism catalysed by CYP3A, CYP3A-mediated mechanism-based inactivation effects, and the formation of fetal-specific CYP3A7-mediated metabolites of dehydroepiandrosterone observed in humans. We determined whether the human CYP3A or mouse Cyp3a enzymes were related to the species-specific teratogenicity in a WEC system using humanized CYP3A mouse embryos

Results and Discussion

Total number of somites

Methods

Author Contributions

Additional Information