量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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When a long term manned space flight and stay is assumed, it is considered to be one of the most prime issues to evaluate the influence of the space radiation on the human body. Especially damages occurring in the reproductive organs bear the risk to seriously injure the descendant. Because experiments using breeding mouse in space is difficult, we propose an alternative method to evaluate the effect of space radiation to mammals. We plan to launch frozen embryonic stem (ES) cells in space for being exposed to space radiation. After returns to ground, the cells will be microinjected to mouse blastocysts to become chimeric mice. The process of development of ES cells can be followed to judge the radiation effects.
We carried out irradiation experiment with heavy particles on ground at HIMAC at Chiba in Japan. We irradiated mouse cultured ES cells after irradiation with doses from 0.01 to 10Gy with carbon (290 MeV/u) and iron ions (500 MeV/u) at room temperature. The survival rate of the cell was analyzed by colony formation. The results show an increase in response in the following order: Fe>C>X-rays. It is planned to launch frozen ES cell; accordingly in a ground-based experiment mouse ES cell frozen at -80 degree-C were also irradiated by dose from 0.01 to 10Gy with carbon (290 MeV/u) and iron ion (500 MeV/u) beams. The number of colonies was counted eight days later and the survival rate of the cells was analyzed. For the dose of 1Gy or more, cells irradiated at standard culture condition are more sensitive than frozen cells.
We irradiated the mouse ES cells by the dose to 0.01-10Gy with carbon (290 MeV/u) and iron (500 MeV/u) beams, and the histone H2AX (gamma-H2AX) phosphorylation was followed. The gamma-H2AX was strongly detected at doses greater than 0.5 Gy 1hr after irradiation, while foci formation after X-ray irradiation was moderately, indicating the induction of severer DNA damage by iron beam irradiation. We will evaluate the influence of space radiation by analyzing development of ES cells-microinjected embryos. The system worked well in the experiment with X-rays, showing the generation of an abnormal embryo to be proportional to irradiation dose. In addition, we try to estimate the influence of space radiation on human ontogeny by comparing the effect to human and mouse iPS cells by using microinjection system.
Effect of heavy ion radiation to mouse ES cells
