Comparison of biological measurement and physical estimates of space radiation in the International Space Station

Transcriptome Analysis by RNA Sequencing of Mouse Embryonic Stem Cells Stocked on International Space Station for 1584 Days in Frozen State after Culture on the Ground

“…The quality factor of the ISS was estimated to be about 1.48 on the ISS. This physically estimated value was similar to the relative biological effectiveness (RBE) of 1.54, which was established by the biological measurement of chromosome aberration using frozen mouse ES cells in the MELFI freezer on the ISS [ 19 ].…”

“…For space experiments, we used wild-type mouse ES cells. Preparation of mouse ES cells lacking the histone H2AX gene with 129 Sv and C57BL/6 heterozygous background was performed as described before [ 19 ].…”

“…Frozen mouse ES cells were thawed at 37 °C. After adding the warmed culture medium [ 19 ], the cells were inoculated on an 8-hole plastic dish and cultured for the experimentally determined time. The pre-culture cell samples and time-indicated samples were taken separately after rubbing with scrapers.…”

“…The dose-equivalent rates, indicating the biological effect that is calculated from a physical dose measurement, are about 0.5–0.62 mSv/day on the International Space Station (ISS) [ 11 , 12 ], 1.15 mSv/day on the surface of the moon of the Earth [ 13 , 14 ], 0.5 mSv/day on the surface of Mars [ 15 ], and 1.84 mSv/day during the flight from the Earth to Mars [ 16 , 17 , 18 ]. In our “Stem Cells” experiment, mouse ES cells were frozen and kept in MELFI on the ISS for 1584 days to quantitate the biological effect of space radiation [ 18 , 19 ]. The physical doses were measured by a passive dosimeter for life science experiments in space (PADLES), and it was revealed that the absorbed dose rate of space radiation in MELFI was 0.36 mGy/day, and the dose-equivalent rate was 0.53 mSv/day, as shown in Figure 1 [ 19 ].…”

“…In our “Stem Cells” experiment, mouse ES cells were frozen and kept in MELFI on the ISS for 1584 days to quantitate the biological effect of space radiation [ 18 , 19 ]. The physical doses were measured by a passive dosimeter for life science experiments in space (PADLES), and it was revealed that the absorbed dose rate of space radiation in MELFI was 0.36 mGy/day, and the dose-equivalent rate was 0.53 mSv/day, as shown in Figure 1 [ 19 ]. About 4.1% of particles had more than 10 keV/μm of LET (linear energy transfer), but they contributed 35.3% of total dose-equivalent.…”