The successful establishment of human embryonic stem cell (hESC) lines has inaugurated a new era in regenerative medicine by facilitating the transplantation of differentiated ESCs to specific organs. However, problems with the safety and efficacy of hESC therapy in vivo remain to be resolved. Preclinical studies using animal model systems, including nonhuman primates, are essential to evaluate the safety and efficacy of hESC therapies. Previously, we demonstrated that common marmosets are suitable laboratory animal models for preclinical studies of hematopoietic stem cell therapies. As this animal model is also applicable to preclinical trials of ESC therapies, we have established novel common marmoset ESC (CMESC) lines. To obtain marmoset embryos, we developed a new embryo collection system, in which blastocysts can be obtained every 3 weeks from each marmoset pair. The inner cell mass was isolated by immunosurgery and plated on a mouse embryonic feeder layer. Some of the CMESC lines were cultured continuously for more than 1 year. These CMESC lines showed alkaline phosphatase activity and expressed stage-specific embryonic antigen (SSEA)-S, SSEA-4, TRA-1-60, and TRA-1-81. On the other hand, SSEA-1 was notdetected. Furthermore, our novel CMESCs are pluripotent, as evidenced by in vivo teratoma formation in immunodeficient mice and in vitro differentiation experiments. Our established CMESC lines and the common marmoset provide an excellent experimental model system for understanding differentiation mechanisms, as well as the development of regenerative therapies using hESCs.
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