Similarities Between Disuse and Age‐Induced Bone Loss

• Published in: Journal of bone and mineral research Vol. 37; no. 8; pp. 1417 - 1434
• Main Authors: Buettmann, Evan G., Goldscheitter, Galen M., Hoppock, Gabriel A., Friedman, Michael A., Suva, Larry J., Donahue, Henry J.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.08.2022; Oxford University Press
• Subjects: Adipogenesis; Advanced glycosylation end products; AGING; Bone and Bones; Bone Diseases, Metabolic; BONE DISORDERS AND DISEASES—OSTEOPOROSIS; Bone growth; Bone loss; Bone mass; Bone resorption; Bone strength; Bone turnover; Cancellous bone; CELLS OF BONE—OSTEOCYTES; Collagen; Cortical bone; Genetic variability; Glycosylation; Humans; Mechanotransduction; Molecular modelling; MOLECULAR PATHWAYS—REMODELING; Osteocytes; Osteoporosis; Osteoprotegerin; PRECLINICAL STUDIES; Reactive oxygen species; Risk factors; SENESCENCE; TRANCE protein; Wnt protein; CELLS OF BONE-OSTEOCYTES; BONE DISORDERS AND DISEASES-OSTEOPOROSIS; AGING; SENESCENCE; PRECLINICAL STUDIES; MOLECULAR PATHWAYS-REMODELING
• ISSN: 0884-0431; 1523-4681; 1523-4681
• DOI: 10.1002/jbmr.4643

ABSTRACT Disuse and aging are known risk factors associated with low bone mass and quality deterioration, resulting in increased fracture risk. Indeed, current and emerging evidence implicate a large number of shared skeletal manifestations between disuse and aging scenarios. This review provides a detailed overview of current preclinical models of musculoskeletal disuse and the clinical scenarios they seek to recapitulate. We also explore and summarize the major similarities between bone loss after extreme disuse and advanced aging at multiple length scales, including at the organ/tissue, cellular, and molecular level. Specifically, shared structural and material alterations of bone loss are presented between disuse and aging, including preferential loss of bone at cancellous sites, cortical thinning, and loss of bone strength due to enhanced fragility. At the cellular level bone loss is accompanied, during disuse and aging, by increased bone resorption, decreased formation, and enhanced adipogenesis due to altered gap junction intercellular communication, WNT/β‐catenin and RANKL/OPG signaling. Major differences between extreme short‐term disuse and aging are discussed, including anatomical specificity, differences in bone turnover rates, periosteal modeling, and the influence of subject sex and genetic variability. The examination also identifies potential shared mechanisms underlying bone loss in aging and disuse that warrant further study such as collagen cross‐linking, advanced glycation end products/receptor for advanced glycation end products (AGE‐RAGE) signaling, reactive oxygen species (ROS) and nuclear factor κB (NF‐κB) signaling, cellular senescence, and altered lacunar‐canalicular connectivity (mechanosensation). Understanding the shared structural alterations, changes in bone cell function, and molecular mechanisms common to both extreme disuse and aging are paramount to discovering therapies to combat both age‐related and disuse‐induced osteoporosis. © 2022 American Society for Bone and Mineral Research (ASBMR).