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    Biomechanics

    (D-145) Effect of Low Dose Acute Proton Radiation Treatment on Bone Strength

    Friday, October 13, 2023
    9:30 AM – 10:30 AM PDT
    Location: Exhibit Hall - Row D - Poster # 145

      Presenting Author(s)

    • AS

      Alexandra K. Stibler (she/her/hers)

      Undergraduate Research Student
      The College of New Jersey
      Mount Laurel Township, New Jersey, United States

      • Co-Author(s)

    • LB

      Laura C. Bowman

      Postdoctoral Researcher
      The College of New Jersey, United States

    • CD

      Catherine M. Davis

      Co-Author
      Uniformed Services University of Health Sciences, United States

      • Primary Investigator(s)

    • AL

      Anthony G. Lau

      Principal Investigator
      The College of New Jersey, United States

    Introduction:: As NASA prepares to venture deeper into space, sources of potential harm to astronaut health, such as space radiation exposure, must be investigated. High energy protons can be emitted from solar flares, emitting ionizing radiation into space, which is capable of damaging DNA, and can cause potential oxidative damage to bone tissue [1,2]. An increase in osteoclast activity following exposure to spaceflight and clinically relevant radiation doses has been demonstrated, alongside damage to osteoblast precursors [3]. The resulting bone loss impacts skeletal health, and bone strength may be compromised, placing astronauts at a higher risk for injury. Further insight into these consequences is required for the development of improved countermeasures. This study aims to quantify the effects of acute exposure to high energy proton radiation on the mechanical properties of bone in a rat model.

    Materials and Methods::

    A cohort of Long Evans rats (n=40, 18 female and 22 male) were irradiated with 50cGy of acute proton radiation (250 and 1000 MEV/n) at the NASA Space Radiation Laboratory at Brookhaven National Labs, along with corresponding sham controls (n=31, 10 female and 21 male). Rats were euthanized at various time points, including 7, 30, 90 and 180 days after exposure. The right femurs were removed, cleaned of nonosseous tissue, and stored in ethanol until testing. A 3-point bend test was conducted for each femur using an Instron Testing Machine model 5967 with an extension rate of 0.02mm/s. The force and displacement data were processed using a MATLAB script to calculate stiffness (N/mm), yield load (N) and maximum load (N). Statistical analysis was performed using a Kruskal-Wallis test to determine significance (p< 0.05). All testing was conducted under IACUC approval.



    Results, Conclusions, and Discussions:: There were no significant differences observed from 3-point bend data for bone mechanical properties between irradiated rats across different time points. However, there were significant sex differences in stiffness (p=1.59e-6), yield load (p=4.83e-4) and maximum load (p=1.35e-6), with trends displaying higher values in the males. These results align with a previous study that discovered male mice tibiae recorded a 27.4% higher stiffness value and a 29.1% higher maximum load compared to females [4]. It is theorized that these differences in mechanical properties across sex are attributed to hormone level variance [4]. Future work will conclude testing on the 180day cohort and include these specimens in the final analysis.

    Measured values for bone stiffness, yield load and maximum load in males were significantly higher than females. Females demonstrated increased variation in the 7day cohort across all properties. Time after exposure did not significantly alter any bone mechanical properties. Further analysis is still required.


    Acknowledgements (Optional): :

    References (Optional): :

    [1] Perez, J. “Why Space Radiation Matters”. (2017, April 13).  NASA.  


    [2] Vico, L., & Hargens, A. (2018). Skeletal changes during and after spaceflight. Nature reviews. Rheumatology, 14(4), 229–245. https://doi.org/10.1038/nrrheum.2018.37


    [3] Willey, J. S., Lloyd, S. A., Nelson, G. A., & Bateman, T. A. (2011). Space Radiation and Bone Loss. Gravitational and space biology bulletin : publication of the American Society for Gravitational and Space Biology, 25(1), 14–21.


    [4] Yao, X., Carleton, S. M., Kettle, A. D., Melander, J., Phillips, C. L., & Wang, Y. (2013). Gender-dependence of Bone Structure and Properties in Adult Osteogenesis Imperfecta Murine Model. Annals of Biomedical Engineering, 41(6), 1139–1149. https://doi.org/10.1007/s10439-013-0793-7