Sex-specific responses in trabecular and cortical microstructure of tibia due to repeated irradiation from micro-computed tomography in adult CD-1 mice

Abstract

While repeated in vivo micro-computed tomography (μCT) allows for longitudinal measurement of bone outcomes in rodent models, it is important to determine that the resulting irradiation – dependent on the frequency and number of scans - does not exceed the effects of the intervention. The objective of this study was to determine whether repeated irradiation exposure from μCT scans at 1-month intervals for a total of four scans would alter trabecular or cortical bone structure outcomes and/or bone mineral density in tibias from both male and female CD-1 mice. The right tibia of male (n = 12) and female (n = 11) CD-1 mice were scanned using μCT at 2, 3, 4, and 5 months of age, while the contralateral left tibia served as a control and was scanned only at 5 months of age. All scans were performed at a resolution of 9 μm using a radiation dose of 460 mGy per scan. Some outcomes of trabecular bone structure were affected by repeated irradiation in both males and females. The bone volume fraction was lower in the irradiated right tibia compared to the non-irradiated left tibia in both males (p < 0.05) and females (p < 0.01) as a result of decreased trabecular number (males p < 0.05; females p < 0.05) and increased trabecular separation (males p < 0.05; females p < 0.01). Some cortical measures were also affected in females but not in males, including lower cortical bone periosteal perimeter (p < 0.05), lower total area (p < 0.01) and lower marrow area (p < 0.05) with repeated irradiation. Exposure to repeated radiation at intervals of 1 month, for a total of four scans, altered trabecular bone in both male and female CD-1 mice while outcomes of cortical bone structure were altered only in females.

Trabecular and cortical bone are unaltered in response to chronic lipopolysaccharide exposure via osmotic pumps in male and female CD-1 mice

“…The microcomputed tomography (μCT) scanning parameters and analysis have previously been published [26] for the male and female control group as they were a part of this larger study. Mice underwent in vivo scans of the hindlimb at 8, 12, 16, and 20 weeks of age by μCT.…”

“…In vivo scanning using μCT. Scans were completed using μCT (SkyScan 1176, Bruker-microCT, Kontich, Belgium) and host software (1176 version 1.1, Bruker-microCT, Kontich, Belgium) as previously described [26][27][28]. To ensure consistent animal sedation during the in vivo scans isoflurane anesthetic was used since the flow rate could be tightly controlled and allowed mice to remain still throughout the scan, essential for obtaining a clear scan.…”

“…Scans of the hindlimb were performed with the mouse positioned on its back with the scanning leg extended and nonscanning leg and tail secured away from scanning region, as previously described [27]. Scans were set to an isotropic resolution of 9 μm with a 1 mm aluminum filter and scanning parameters were specified at 3350 ms exposure time, 40 kV and 300 μA using a rotation step of 0.8o ver 180˚with no frame averaging [26] (Table 1). Scanning parameters are summarized in Table 1.…”

“…As previously described, GPURecon Server program (version 1.7.3.2, Bruker-microCT) and NRecon Reconstruction (version 1.7.3.1, Bruker-microCT) were used to reconstruct cross-sectional images [26]. The same reconstruction parameters were applied to all images for males…”

Direct Assessment of Rabbit Cortical Bone Basic Multicellular Unit Longitudinal Erosion Rate: A 4D Synchrotron-Based Approach

“…( 34 , 35 ) Although the translation of this technology to cortical bone porosity occurred relatively early, ( 36 ) the translation to in vivo cortical porosity imaging in preclinical models has been relatively rare, ( 37 , 38 ) being impeded by the need for higher resolution and, concomitantly, higher radiation dose. Indeed, repetitive in vivo trabecular bone protocols with typical image resolutions of 9 to 18 μm ( 39 , 40 , 41 ) and radiation doses in the range of 0.5 to 1 Gy are known to cause adverse effects, such as reduced bone volume fraction in the tibiae of mice. ( 39 , 41 , 42 , 43 ) In vivo synchrotron radiation (SR) scans of 13‐week‐old mice's knees at a dose of 5 Gy have also reported adverse effects on trabecular bone 10 days post scan.…”