PDF(Pubmed)
Abstract：
Nowadays, ordinary people can travel in space, and the possibility of extended durations in an environment such as moon of the Earth and Mars with higher space radiation exposures compared to past missions, is increasing. Until now, the physical doses of space radiation have been measured, but measurement of direct biological effects has been hampered by its low dose and low dose-rate effect. To assess the biological effects of space radiation, we launched and kept frozen mouse embryonic stem (ES) cells in minus eighty degree Celsius freezer in ISS (MELFI) on the International Space Station (ISS) for a maximum of 1,584 days. The passive dosimeter for life science experiments in space (PADLES) was attached on the surface of the sample case of the ES cells. The physical dosimeter measured the absorbed dose in water. After return, the frozen cells were thawed and cultured and their chromosome aberrations were analyzed. Comparative experiments with proton and iron ion irradiation were performed at particle accelerators on Earth. The wild-type ES cells showed no differences in chromosomal aberrations between the ground control and ISS exposures. However, we detected an increase of chromosome aberrations in radio-sensitized histone H2AX heterozygous-deficient mouse ES cells and found that the rate of increase against the absorbed dose was 1.54-fold of proton irradiation at an accelerator. On the other hand, we estimated the quality factor of space radiation as 1.48 ± 0.2. using formulas of International Commission of Radiation Protection (ICRP) 60. The relative biological effectiveness (RBE) observed from our experiments (1.54-fold of proton) was almost equal (1.04-fold) to the physical estimation (1.48 ± 0.2). It should be important to clarify the relation between biological effect and physical estimates of space radiation. This comparative study paves a way to reveal the complex radiation environments to reduce the uncertainty for risk assessment of human stay in space.
摘要：
如今,普通人可以在太空旅行，以及与过去的任务相比，在地球月球和火星等具有更高空间辐射暴露的环境中延长持续时间的可能性，正在增加。直到现在,已经测量了空间辐射的物理剂量，但其低剂量和低剂量率效应阻碍了直接生物学效应的测量。为了评估空间辐射的生物效应，我们在国际空间站（ISS）的ISS（MELFI）中的零下80摄氏度冰箱中发射并保存了冷冻的小鼠胚胎干细胞（ES），最长时间为1,584天。用于太空生命科学实验的被动剂量计（PADLES）附着在ES细胞的样品盒的表面上。物理剂量计测量水中的吸收剂量。回来后,将冷冻细胞解冻培养，分析其染色体畸变。在地球上的粒子加速器上进行了质子和铁离子辐照的比较实验。野生型ES细胞在地面对照和ISS暴露之间的染色体畸变没有差异。然而,我们检测到放射性致敏组蛋白H2AX杂合子缺陷型小鼠ES细胞中染色体畸变的增加,并发现在加速器下质子照射相对于吸收剂量的增加速率为1.54倍.另一方面,我们估计空间辐射的质量因子为1.48±0.2。使用国际辐射防护委员会(ICRP)60的公式。从我们的实验中观察到的相对生物有效性（RBE）（质子的1.54倍）几乎等于（1.04倍）物理估计值（1.48±0.2）。阐明生物效应与空间辐射的物理估计之间的关系应该很重要。这项比较研究为揭示复杂的辐射环境铺平了道路，以减少人类在太空中的风险评估的不确定性。
