Aging exacerbates the morphological and mechanical response of mineralized collagen fibrils in murine cortical bone to disuse

Mineralized collagen fibrils (MCFs) are the fundamental building blocks of bone tissue and contribute significantly to the mechanical behavior of bone. However, it is still largely unknown how the collagen network in bone responds to aging and the disuse normally accompanying it. Utilizing atomic force mi-croscopy, nanoindentation and Raman spectroscopy, age-related alterations in the microstructure and me-chanical properties of murine cortical tibia at multiple scales were investigated in this study. The poten-tial difference in the responses of bone to disuse at different ages was studied. The results indicated that the age-and disuse-related alterations in bone initiate from MCFs in the bone matrix. The D-periodic spacing, radial elastic modulus of a single MCF and the mineral-to-matrix ratio on the cortical bone sur-face were larger in aged mice than in adult mice. Disuse, on the other hand, mainly has a major influence on aged mice, particularly on the morphology and mechanical properties of MCFs, but it only has modest effects on adult bone. These findings revealed insights into the morphological and mechanical adaptation of mineralized collagen fibrils in murine cortical bone to aging and disuse.Statement of significance Bone is a complex structured composite material consisting of an interwoven framework of collagen fib-rils reinforced by mineral particles and embedded in an extrafibrillar mineralized matrix. Utilizing atomic force microscopy, nanoindentation and Raman spectroscopy, this study suggests that the effects of aging, as well as the accompanying disuse, on the morphology and mechanical properties of bone initiate from the mineralized collagen fibril level. More interestingly, the MCF in the bone of aged mice seems to be more sensitive to disuse than that in adult mice. These findings significantly further the current under-standing of the adaptation process of bone to aging at the mineralized collagen fibril level and provide direct insights into the physiological response of bone to aging and the abnormal mechanical environ-ment. (c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the effects of aging and disuse on the microstructure and mechanical properties of mouse bone, focusing on the mineralized collagen fibrils. The results revealed that the alterations in bone due to aging and disuse initiated from the mineralized collagen fibrils in the bone matrix. The findings provide insights into the adaptation process of bone to aging and the abnormal mechanical environment.