![]() ![]() There is growing evidence that the serum component can reflect the state of osteoporosis, and physical activity in humans. The imbalance in bone remodeling culminates in various degrees of bone loss. long-term inactivity and disuse such as long-term bed bound, and microgravity increase bone resorption to a rate higher than bone formation. Similar conditions in humans and other mammals lead to osteopenia and osteoporosis, e.g. Previous studies by the use of biochemical, histological, and imaging tests have clearly shown that bears do not suffer from osteoporosis despite long-term inactivity, lack of food intake and cold exposure during hibernation. Interestingly, hibernating bears’ musculoskeletal system is not compromised by environmental and metabolic alterations throughout the torpor period. Another distinctive feature is that bears do not intake food, urinate, nor defecate during hibernation. Bears, in terms of body mass, are by far the largest hibernating mammalian species. ![]() Hibernating mammals have evolved with various types of physiological and behavioral responses, which enable them to go through harsh environmental conditions. Hibernation is a phenomenon affected by external stimuli such as cold season, short day length and food paucity, and internal factors such as biochemical regulations and circadian rhythm. In addition, this study for the first time showed the formation of bears’ OCs in-vitro. It was revealed that osteoclastogenesis of PBMCs is hindered by HBSM, implying an underlying mechanism for the suppressed bone resorption during hibernation in bears. However, cells supplemented with hibernating bear serum containing medium (HBSM) failed to form OCs, and showed significantly lower TRAP stain ( p 0.05), indicating no difference on cell growth. PBMCs that were cultured with the active bear serum containing medium (ABSM) differentiated to multi-nucleated OCs, and were positive for TRAP stain. PBMCs collected from 3 bears were separately cultured with 10% serum of 4 active and 4 hibernating bears (each individual serum type was assessed separately by a bear PBMCs), and differentiation were induced by treatment with macrophage colony stimulating factor (M-CSF) and receptor activator of NF-kB ligand (RANKL). We investigated the effect of serum from hibernating Japanese black bears ( Ursus thibetanus japonicus) on differentiation of peripheral blood mononuclear cells (PBMCs) to osteoclasts (OCs). However, the mechanisms involved in bone loss prevention have scarcely been elucidated in bears. Bears do not suffer from osteoporosis during hibernation, which is associated with long-term inactivity, lack of food intake, and cold exposure. ![]()
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