title: A Simplified In Vitro Teratoma Assay for Pluripotent Stem Cells Injected Into Rodent Fetal Organs.
abstract: Teratoma formation assays are established methods for evaluating the pluripotency of embryonic stem (ES) cells and induced pluripotent stem (iPS) cells. Teratoma formation in immunodeficient mice takes approximately 2 months. Here, we have developed a novel assay system for developing teratomas in vitro from ES cells and iPS cells in a short period. In vitro culture of ES, iPS, and mesenchymal stem cells (MSCs) in fetal rat metanephroi for 1 week resulted in distinct cell-dependent distribution patterns: Pluripotent cells (ES and iPS cells) formed aggregated masses, whereas MSCs showed disseminated distribution. The aggregated masses that had developed from ES cells and iPS cells after 2 weeks of culture comprised teratomas, though they were largely composed of immature components. Furthermore, in vitro organ culture for 1 week followed by relay transplantation into immunodeficient mice resulted in considerably rapid growing teratomas (teratomas developed in 4 weeks) having similar pathological features as of the teratomas developed using conventional 7-week in vivo teratoma formation assays. In addition, the initial cell number required in the in vitro assay was 1 × 103cells, which was about 1% of the number of cells required in the conventional in vivo teratoma formation assays. These results suggest that the in vitro teratoma assay is a rapid and convenient screening system and might be an alternative method for developing teratomas for investigating the pluripotency of ES cells and iPS cells.
authors.affiliation: Division of Regenerative Medicine, Center for Molecular Medicine, Jichi Medical University, Tochigi, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Masuda
authors.affiliation: †Division of Development of Advanced Treatment (DDAT), Center for Development of Advanced Medical Technology (CDAMTec), Jichi Medical University, Tochigi, Japan; ‡Project Laboratory for Kidney Regeneration, Institute of DNA Medicine, Jikei University School of Medicine, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yokoo
authors.affiliation: †Division of Development of Advanced Treatment (DDAT), Center for Development of Advanced Medical Technology (CDAMTec), Jichi Medical University, Tochigi, Japan; §Research and Development Center, Otsuka Pharmaceutical Factory, Inc., Tokushima, Japan.
authors.forename: Naomi
authors.initials: N
authors.lastname: Sugimoto
authors.affiliation: †Division of Development of Advanced Treatment (DDAT), Center for Development of Advanced Medical Technology (CDAMTec), Jichi Medical University, Tochigi, Japan; §Research and Development Center, Otsuka Pharmaceutical Factory, Inc., Tokushima, Japan.
authors.forename: Masako
authors.initials: M
authors.lastname: Doi
authors.affiliation: Division of Regenerative Medicine, Center for Molecular Medicine, Jichi Medical University, Tochigi, Japan.
authors.forename: Shuh-Hei
authors.initials: SH
authors.lastname: Fujishiro
authors.affiliation: ¶Pathology Project for Molecular Targets, Cancer Institute, Japanese Foundation for Cancer Research, Tokyo, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Takeuchi
authors.affiliation: †Division of Development of Advanced Treatment (DDAT), Center for Development of Advanced Medical Technology (CDAMTec), Jichi Medical University, Tochigi, Japan; §Research and Development Center, Otsuka Pharmaceutical Factory, Inc., Tokushima, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Kobayashi
authors.affiliation: Division of Regenerative Medicine, Center for Molecular Medicine, Jichi Medical University, Tochigi, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Hanazono
keywords: ES cells; Fetal rat metanephros; Organ culture; Teratoma formation; iPS cells