Ai Takemura1,2, Paola Divieti Pajevic3, Tatsuro Egawa4, Rika Teshigawara5, Tatsuya Hayashi4, Akihiko Ishihara6. 1. Laboratory of Cell Biology and Life Science, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, 606-8501, Japan. takemura.ai.46c@kyoto-u.jp. 2. Department of Sports Research, Japan Institute of Sport Sciences, Tokyo, 115-0056, Japan. takemura.ai.46c@kyoto-u.jp. 3. Department of Translational Dental Medicine, Boston University Goldman School of Dental Medicine, Boston, MA, 02118, USA. 4. Laboratory of Sports and Exercise Medicine, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, 606-8501, Japan. 5. Laboratory of Developmental Epigenome, Graduate School of Medicine, Kyoto University, Kyoto, 606-8507, Japan. 6. Laboratory of Cell Biology and Life Science, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, 606-8501, Japan.
Abstract
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.
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.
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