Abstract
Proton radiation (PR) and microgravity (μG) are two key factors that impact living things in space. This study aimed to explore the combined effects of PR and simulated μG (SμG) on bone function. Mouse embryo osteoblast precursor cells (MC3T3-E1) were irradiated with proton beams and immediately treated with SμG for 2 days using a three-dimensional clinostat. All samples were subjected to cell viability, alkaline phosphatase (ALP) activity and transcriptome assays. The results showed that cell viability decreased with increasing doses of PR. The peak ALP activity after PR or SμG alone was lower than that obtained with the non-treatment control. No difference in cell viability or ALP activity was found between 1 Gy PR combined with SμG (PR-SμG) and PR alone. However, 4 Gy PR-SμG resulted in decreased cell viability and ALP activity compared with those obtained with PR alone. Furthermore, Gene Ontology analysis revealed the same trend. These results revealed that PR-SμG may lead to reductions in the proliferation and differentiation capacities of cells in a dose-dependent manner. Our data provide new insights into bone-related hazards caused by multiple factors, such as PR and μG, in the space environment.
Highlights
With the comprehensive development of manned space exploration missions, more astronauts need to be sent into space
No difference in cell viability was detected between 1 Gy Proton radiation (PR)-simulated μG (SμG) and 1 Gy PR alone after 36 hours, whereas the 4 Gy PR combined with SμG (PR-SμG) treatment resulted in significantly lower viability than that obtained with the 4 Gy PR alone (p < 0.05)
Our experimental results show that a high dose (4 Gy) of PR combined with SμG has a stronger inhibitory effect on cell viability than PR alone
Summary
With the comprehensive development of manned space exploration missions (such as manned missions to the Moon and manned missions to Mars), more astronauts need to be sent into space. Astronauts on space missions will experience space environmental stressors, such as continuous microgravity (μG) and uninterrupted doses of ionizing radiation [1]. The impact of the space environment on astronauts is directly related to their own health and whether the space mission can be successfully completed. It is necessary to perform a risk assessment of the space environment for astronauts. The risks of the μG environment to astronauts’ health cannot be ignored. Long-term space flight causes a variety of physiological and pathological changes in the body of astronauts, such as bone loss, decreased immune function, and muscle atrophy. One of the most obvious is the decrease in bone density caused by space μG. A recent study conducted a systematic retrospective analysis of the bone density of 148 individuals who had performed space
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