Yoshida Kayo, Hada Megumi, Kizu Akane, Kitada Kohei, Eguchi-Kasai Kiyomi, Kokubo Toshiaki, Teramura Takeshi, Yano Sachiko, Suzuki Hiromi Hashizume, Watanabe Hitomi, Kondoh Gen, Nagamatsu Aiko, Saganti Premkumar, Cucinotta Francis A, Morita Takashi
Osaka City University, Graduate School of Medicine, Osaka, Japan.
Radiation Institute for Science and Engineering, Prairie View A&M University, TX, USA.
Heliyon. 2022 Aug 18;8(8):e10266. doi: 10.1016/j.heliyon.2022.e10266. eCollection 2022 Aug.
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 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.
如今，普通人也能够进入太空，而且在诸如地球的月球和火星等环境中停留更长时间的可能性正在增加，与过去的任务相比，这些环境中的太空辐射暴露量更高。到目前为止，已经对太空辐射的物理剂量进行了测量，但由于其低剂量和低剂量率效应，直接生物效应的测量受到了阻碍。为了评估太空辐射的生物效应，我们将小鼠胚胎干细胞发射到国际空间站（ISS）零下80摄氏度的冷冻器（MELFI）中并保持冷冻状态，最长达1584天。太空生命科学实验用被动剂量计（PADLES）附着在胚胎干细胞样本盒的表面。物理剂量计测量了水中的吸收剂量。返回后，将冷冻的细胞解冻并培养，然后分析其染色体畸变情况。在地球上的粒子加速器上进行了质子和铁离子辐照的对比实验。胚胎干细胞在地面对照和国际空间站暴露之间的染色体畸变没有差异。然而，我们在对辐射敏感的组蛋白H2AX杂合缺陷小鼠胚胎干细胞中检测到染色体畸变增加，并发现相对于吸收剂量的增加率是加速器中质子辐照的1.54倍。另一方面，我们使用国际辐射防护委员会（ICRP）60号公式估计太空辐射的品质因数为1.48±0.2。我们实验中观察到的相对生物效能（RBE）（质子的1.54倍）几乎与物理估计值（1.48±0.2）相等（1.04倍）。阐明太空辐射的生物效应与物理估计之间的关系应该很重要。这项对比研究为揭示复杂的辐射环境铺平了道路，以减少人类在太空停留风险评估的不确定性。
