Spatial Variation in Osteonal Bone Properties Relative to Tissue and Animal Age

Abstract

Little is known about osteonal bone mineral and matrix properties, although these properties are of major importance for the understanding of bone alterations related to age and bone diseases such as osteoporosis. During aging, bone undergoes modifications that compromise their structural integrity as shown clinically by the increase of fracture incidence with age. Based on Fourier transform infrared (FTIR) analysis from baboons between 0 and 32 yr of age, consistent systematic variations in bone properties as a function of tissue age are reported within osteons. The patterns observed were independent of animal age and positively correlated with bone tissue elastic behavior measured by nano-indentation. As long as tissue age is expressed as a percentage of the entire osteon radius, osteonal analyses can be used to characterize disease changes independent of the size of the osteon. These mineral and matrix analyses can be used to explain bone fragility. The mineral content (mineral-to-matrix ratio) was correlated with the animal age in both old (interstitial) and newly formed bone tissue, showing for the first time that age-related changes in BMC can be explain by an alteration in the mineralization process itself and not only by an imbalance in the remodeling process.

Relationship between the v2PO4/amide III ratio assessed by Raman spectroscopy and the calcium content measured by quantitative backscattered electron microscopy in healthy human osteonal bone

“…32,33 This variability is likely due to changes in the apatite composition due to type A and type B carbonate substitutions as well as Mg, Na, or K or even the presence of calcium ion lattice vacancies in the apatite crystal. [34][35][36][37][38] Of course, alterations in the mineral composition or phase change both Raman and qBEI outcomes. The expected range of the measurements according to changes in the Ca/P ratio is estimated in Sec.…”

“…This is in agreement with the previous studies showing that the chemical composition of hydroxyapatite changes as a function of the location (thus tissue age) within an osteon. 10,35 Of course, it cannot be excluded that changes in the organic matrix also contribute to the observed variability. For example, phosphorylated organic molecules potentially increase the local PO 4 content, and protein-bound Ca may also contribute to our results.…”

Raman Assessment of Bone Quality

“…Second, the quantum efficiency of the best available CCD detector in the 800 to 900-nm range (required for 785-nm laser excitation) is approximately 30% to 40% [20,27]. As a consequence, individual Raman measurements can be made of bone matrix collagen bands in the amide I region (approximately 1620-1710 cm À1 ) have lower S/N ratios and are less precise than single infrared measurements [30,55]. Raman measurements can be made very precise by averaging multiple Raman spectra from a single Raman image, resulting in S/N ratios of up to 850:1 [40].…”

Aging Versus Postmenopausal Osteoporosis: Bone Composition and Maturation Kinetics at Actively-Forming Trabecular Surfaces of Female Subjects Aged 1 to 84 Years

“…(5,6) Bone quality is also dependent on other factors such as homocysteine (which has been proposed as a fracture risk contributor). Moreover, the material compositional properties have been shown to significantly vary as a function of both subject and tissue age, (2,(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) and correlate with bone's mechanical properties in both animal models and humans, (8,11,14,16,17) though tissue age was determined on general anatomical morphological criteria (eg, distance from Haversian canal in osteons) rather than more robust, histomorphometric criteria, and most of these studies focused on cortical bone.…”