Bone strength depends on the amount of bone, typically expressed as bone mineral density (BMD) determined by dual X-ray absorptiometry (DEXA), and on bone quality. Bone quality is a multifactorial entity including bone structural and material properties. Both BMD and bone quality are dependent on bone turnover rates, which change as a function of subjects chronological age. Moreover, the material properties are greatly dependent on tissue age as well. The purpose of the present study was to examine whether bone material properties in health are dependent on subject age, independent of changes in turnover rates, and to contrast them against postmenopausal osteoporosis patients. To achieve this, we analysed by Raman microspectroscopy iliac crest biopsies from: healthy subjects aged 1.545.7 years, paired biopsies from females before and immediately after menopause aged 46.753.6 years, and biopsies from placebo-treated postmenopausal osteoporotic patients aged 6676 years. Data were obtained at actively forming trabecular bone surfaces, as evidenced by the presence of fluorescent double labels, and expressed as a function of tissue age. The monitored parameters as a function of subject and tissue age were: the mineral/matrix ratio; the mineral, organic matrix, glycosaminoglycan (GAG), and lipid contents; the mineral maturity/crystallinity; and the relative pyridinoline content. The results indicate that these bone quality parameters in healthy bone are dependent on subject age, independent of bone turnover, suggesting that with advancing age the kinetics of maturation (either accumulation, or post-translational modifications, or both) change. Moreover, they showcase the alterations due to an age-related transition such as menopause as opposed to disease (postmenopausal osteoporosis). The relative pyridinoline content exhibited unique changes in postmenopausal osteoporosis compared to the changes due to healthy ageing. The results of the present study help discriminate between ageing and disease, potentially improving our understanding of osteoporosis.
Disclosure: The authors declared no competing interests.