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Biomechanics

Biomechanics - Poster Session B

Poster E2 - Effects of Continuous, Low Dose-Rate Neutron Radiation Exposure on Maternal Bone Microstructure During Pregnancy

Thursday, October 24, 2024
2:45 PM - 3:45 PM EST
Location: Exhibit Hall E, F & G

Introduction:  As NASA moves towards the first human voyage to Mars and to put the first woman on the moon, the creation of extra-Earth colonies seems to increase in likelihood and viability. To make this prospect more achievable, the safety of future colonists must be secured. A key aspect of this is understanding the long-term physiological effects of the space radiation environment. Previous studies have found exposure to neutron radiation decreases both compressive elastic modulus and compressional breaking strength in the cortical bone of large mammals [1]. During pregnancy, the mother’s bones undergo resorption to meet the developmental demands of the fetus [2]. However, the impact of continuous exposure to low-dose-rate radiation on the female skeletal system during pregnancy is less well-defined. The goal of this study is to analyze the combined effect of neutron radiation and pregnancy on maternal skeletal health using image processing.

Materials and

Methods:  Eight to twelve-week-old female C57BL/6J mice were mated with male C57BL/6J mice and randomized into two gestational time point groups (E12.5 or E18.5 then subdivided into irradiated and non-irradiated groups following confirmation of vaginal plug development. Irradiated animals were housed in the CSU Neutron Radiation Facility vivarium and received continuous, whole-body neutron radiation exposure at 1mGy/day for either 12 or 18 days. Non-irradiated animals were housed in an adjacent vivarium and exposed to CSU background radiation (0.005mGy/day). At euthanasia, the right hind limbs were removed. MicroCT scans were conducted at 6μm resolution using a SCANCO μCT40. Due to varying tibia lengths, the region of interest was chosen for anatomical comparability rather than a fixed distance from a landmark [3]. The cortical and trabecular bone were separated using MIMICS and imported into ImageJ, where the BoneJ plugin was used to calculate morphometric parameters, including bone volume, total volume, thickness, and connectivity.

Results, Conclusions, and Discussions: Preliminary analysis revealed exposure to neutron radiation resulted in a significant decline in trabecular connectivity density at the E18.5 gestational time point (p=0.0273, Fig 1) and near significance at the E12.5 gestational state (p=0.0659, Fig 1). There was no effect of radiation exposure at either timepoint for trabecular thickness.
Finding a statistically significant difference in trabecular connectivity density at the E18.5 gestational time point may indicate substantial differences in the mechanical strength of the trabecular structure. Future work will involve finite element analysis to run mechanical simulations on the existing DICOMS to test this. Imaging limitations may inflate the average trabecular thickness in irradiated groups, as very thin trabeculae might not be detected during scans or thresholding.
Significant differences were found in the trabecular connectivity density of the E18.5 gestational time point group. Analysis of additional parameters of both trabecular and cortical bone is ongoing and will be required to fully explore the effects of neutron radiation on the microstructure of pregnant mice.

Acknowledgements (Optional):  [1] Galiano, Eduardo, et al., (2024) “Mechanical and architectural changes in animal bone following fast neutron irradiation.” Health Physics, 127(2), 298–305.
[2]Yun, K. Y., Han, S. E., Kim, S. C., Joo, J. K., & Lee, K. S. (2017). “Pregnancy-related osteoporosis and spinal fractures.” Obstetrics & Gynecology Science, 60(1), 133–137.
[3] Bouxsein, Mary L, et al., (2010). “Guidelines for assessment of bone microstructure in rodents using micro-computed tomography.” Journal of Bone and Mineral Research, 25(7), 1468–1486.