Effect of in vivo loading on bone composition varies with animal age

Abstract

Loading can increase bone mass and size and this response is reduced with aging. It is unclear, however how loading affects bone mineral and matrix properties. Fourier Transform Infrared Imaging and high resolution synchrotron scanning small angle X-ray scattering were used to study how bone’s microscale and nanoscale compositional properties were altered in the tibial midshaft of young, adult, and elderly female C57Bl/6J mice after two weeks of controlled in vivo compressive loading in comparison to physiological loading. The effect of controlled loading on bone composition varied with animal age, since it predominantly influenced the bone composition of elderly mice. Interestingly, controlled loading led to enhanced collagen maturity in elderly mice. In addition, although the rate of bone formation was increased by controlled loading based on histomorphometry, the newly formed tissue had similar material quality to new bone tissue formed during physiological loading. Similar to previous studies, our data showed that bone composition was animal and tissue age dependent during physiological loading. The findings that the new tissue formed in response to controlled loading and physiological loading had similar bone composition and that controlled loading enhanced bone composition in elderly mice further supports the use of physical activity as a noninvasive treatment to enhance bone quality as well as maintain bone mass in individuals suffering from age-related bone loss.

Skeletal maturation substantially affects elastic tissue properties in the endosteal and periosteal regions of loaded mice tibiae

“…We have previously shown that mineral and matrix properties are not altered by rapid bone tissue formation induced by mechanical loading [51]. In this study, also contrary to our hypothesis, we did not observe a reduction of tissue stiffness of bone formed as a response to loading in adult mice (26 week old) compared to younger mice (10 week old).…”

“…These results show an increase in bone tissue stiffness with age, which is in agreement with previous studies [64][65][66][67]. Interestingly, in a recent study [51], we did not observe a significant difference in mineral:matrix ratio or mineral organization in 10 versus 26 week old animals in the intracortical region. However, we did detect an increase in the carbonate:matrix ratio, which might partially explain differences in tissue elasticity.…”

“…This is also supported by recent Fourier transform infrared spectroscopy analyses [51], showing no differences in mineral-to-matrix ratio, collagen maturity or crystallinity of the newly formed bone from 10 week old compared to 26 week old mice.…”

“…We aimed at investigating two age groups with significantly different bone tissue elastic properties. In a recent study [51], we have shown that mechanical loading led to enhanced collagen maturity in the intra-cortical region in elderly mice while no changes were Fig. 7.…”

“…Histomorphometric and FTIR analyses were previously performed and reported for the same samples [50,51]. For the sake of clarity, the preparation of the samples is briefly described here.…”