Altered skeletal morphology resulting from in vivo micro-CT radiation exposure

Objectives: Much of the aging population suffers from osteoporosis and tooth loss. It is well established that periodontitis often results in tooth loss; however, the relationship between periodontitis and skeletal bone density is poorly understood. Furthermore, there have been no studies assessing the beneficial effect of systemic osteoporosis treatments on oral health. As such, recent researches focus on clarifying the relationship between osteoporosis and oral bone loss. In vivo micro-computed tomography(micro-CT) is the gold standard for assessing bone architecture in longitudinal studies; however, the skeletal changes resulting from serial in vivo micro-CT scans are poorly understood. In the present study, we demonstrate the impact of micro-CT radiation exposure on bone morphology in ovariectomized mouse model.
Methods: 12-week-old female BALB/c mice were randomly assigned to radiation and non-radiation groups at 5weeks post-ovariectomy(OVX) or Sham operation(4 groups; n=8/group). Biweekly DXA scans for all groups and monthly in vivo micro-CT scans for radiation groups were taken to dynamically assess bone-mineral-density(BMD). Animals were sacrificed at 13weeks for ex vivo micro-CT analysis and histology.
Results: Success of OVX was confirmed by decrease in uterine weight (mean 78%) compared to Sham. DXA analysis revealed that OVX radiation group had decreased BMD at L5, 6 vertebrae(7.42% decrease), distal femur(0.619% decrease), and proximal tibia(1.66% decrease) at 13weeks than non-radiated OVX mice. Interestingly, cortical thickness of femoral and tibial metaphyses and tibial midshaft were significantly increased in OVX radiation group(10.7%; 15.6%; and 7.22% increase, respectively). The effect of radiation was non-significant in Sham groups. Preliminary in vivo micro-CT data shows a similar trend in BMD, BV/TV, and trabecular structures.
Conclusions: Exposure to high radiation associated with in vivo micro-CT alters skeletal morphology on a site-dependent basis in ovariectomized mice. The site-specific effects of radiation are critical to consider when using in vivo micro-CT on the OVX mouse model.