Effects of mild hyperbaric oxygen on osteoporosis induced by hindlimb unloading in rats

• Published in: Journal of bone and mineral metabolism Vol. 38; no. 5; pp. 631 - 638
• Main Authors: Takemura, Ai, Pajevic, Paola Divieti, Egawa, Tatsuro, Teshigawara, Rika, Hayashi, Tatsuya, Ishihara, Akihiko
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01.09.2020; Springer Nature B.V
• Subjects: Animals; Atmospheric pressure; Body Weight; Bone growth; Bone loss; Bone Morphogenetic Proteins - genetics; Bone Morphogenetic Proteins - metabolism; Bone resorption; Cancellous bone; Cancellous Bone - pathology; Cancellous Bone - physiopathology; Cortical bone; Cortical Bone - pathology; Cortical Bone - physiopathology; Environmental conditions; Gene expression; Genetic Markers - genetics; Growth Plate - pathology; Hindlimb Suspension - physiology; Hyperbaric oxygen; Hyperbaric Oxygenation; Male; Medicine; Medicine & Public Health; Metabolic Diseases; Original Article; Orthopedics; Osteoblasts; Osteocalcin - genetics; Osteocalcin - metabolism; Osteoclasts; Osteoclasts - pathology; Osteogenesis; Osteoporosis; Osteoporosis - genetics; Osteoporosis - physiopathology; Osteoporosis - therapy; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha - genetics; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha - metabolism; RANK Ligand - genetics; RANK Ligand - metabolism; Rats, Wistar; RNA, Messenger - genetics; RNA, Messenger - metabolism; Rodents; SOST protein; Surface area; Unloading; Hindlimb unloading; Osteoporosis; Mild hyperbaric oxygen; Bone loss; Oxidative metabolism
• ISSN: 0914-8779; 1435-5604
• DOI: 10.1007/s00774-020-01100-6

Introduction Disuse-induced bone loss is caused by a suppression of osteoblastic bone formation and an increase in osteoclastic bone resorption. There are few data available for the effects of environmental conditions, i.e., atmospheric pressure and/or oxygen concentration, on osteoporosis. This study examined the effects of mild hyperbaric oxygen at 1317 hPa with 40% oxygen on unloading-induced osteoporosis. Materials and methods Eighteen 8-week old male Wistar rats were randomly divided into three groups: the control for 21 days without unloading and mild hyperbaric oxygen (NOR, n  = 6), the unloading for 21 days and recovery for 10 days without mild hyperbaric oxygen (HU + NOR, n  = 6), and the unloading for 21 days and recovery for 10 days with mild hyperbaric oxygen (HU + MHO, n  = 6). Results The cortical thickness and trabecular bone surface area were decreased in the HU + NOR group compared to the NOR group. There were no differences between the NOR and HU + MHO groups. Osteoclast surface area and Sclerostin (Sost) mRNA expression levels were decreased in the HU + MHO group compared to the HU + NOR group. These results suggested that the loss of the cortical and trabecular bone is inhibited by mild hyperbaric oxygen, because of an inhibition of osteoclasts and enhancement of bone formation with decreased Sost expression. Conclusions We conclude that exposure to mild hyperbaric oxygen partially protects from the osteoporosis induced by hindlimb unloading.