Aging and three dimensional changes of bone structure in rats

Methods: The femora and mandibles from young (3-month-old), adult (12-month-old) and old (24-month-old) male and female Wistar rats were morphometrically analyzed, with three male and three female rats used per age group. After anaesthesia, all animals were sacrificed and the femora and mandibles extracted. All experiments were performed in accordance with the guidelines of the Institutional Animal Care and Use Committee of Showa University. The specimens were scanned and analyzed using an X-ray micro-CT system (Shimadzu Co, Kyoto, Japan), and further assessed with three-dimensional reconstruction and structure analysis.

Results: We showed that trabecular number, thickness and bone mineral density (BMD) in both the femora and mandibles increased up to 12 months of age and then decreased by 24 months. Cortical BMD in the femora continued to increase throughout the 24 months; however, no statistical difference in cortical BMD in the mandibles was observed between the 12- and 24-month-old groups. Additionally, in all groups, the values for female rats were lower than those for their male counterparts.

Conclusion: These results confirmed that aging decreased bone volume and altered bone structure in both male and female rats.