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Spaceflight-relevant types of ionizing radiation and cortical bone: Potential LET effect?
Shane A J Lloyd1, Eric R Bandstra, Neil D Travis
1Department of Bioengineering, Clemson University, 501 Rhodes Engineering Research Center, Clemson, SC 29634, USA.
Summary
Space radiation, particularly high-energy particles, significantly impacts bone health. This study reveals that high-linear energy transfer (LET) radiation negatively affects cortical bone properties, increasing fracture risks for astronauts.
Area of Science:
- Space medicine
- Radiation biology
- Skeletal physiology
Background:
- Spaceflight causes bone loss, exacerbated by radiation exposure, increasing fracture risk.
- Previous studies showed significant trabecular bone loss after 2 Gy radiation.
- Cortical bone's role in skeletal strength necessitates its analysis alongside trabecular bone.
Purpose of the Study:
- To investigate the effects of various spaceflight-relevant radiation types on cortical bone properties in mice.
- To compare the impact of low-LET (gamma, proton) and high-LET (carbon, iron) radiation on bone structure and strength.
Main Methods:
- Female C57BL/6 mice received a single 2 Gy whole-body dose of gamma, proton, carbon, or iron radiation.
- Femora were analyzed using biomechanical testing, microcomputed tomography, histomorphometry, mineral content, and micro-hardness analysis.
- Evaluated outcomes included fracture force, medullary area, and mineral content.
Main Results:
- High-LET radiation (carbon, iron) significantly reduced fracture force, medullary area, and mineral content compared to controls.
- High-LET irradiation was associated with declines in structural properties and mineral composition versus low-LET radiation.
- Bone loss appears primarily specific to trabecular bone, suggesting distinct biological responses.
Conclusions:
- Cortical bone properties are differentially affected by radiation type, with high-LET particles posing a greater risk.
- Findings suggest unique biological microenvironments and microdosimetry conditions influence radiation-induced bone loss.
- Further research is needed due to limited time points and the non-haversian bone structure in mice.
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