Abstract
The interactions between skeletal muscle and bone have been recently noted, and muscle-derived humoral factors related to bone metabolism play crucial roles in the muscle/bone relationships. We previously reported that extracellular vesicles from mouse muscle C2C12 cells (Myo-EVs) suppress osteoclast formation in mice. Although mechanical stress is included in extrinsic factors which are important for both muscle and bone, the detailed roles of mechanical stress in the muscle/bone interactions have still remained unknown. In present study, we examined the effects of fluid flow shear stress (FFSS) to C2C12 cells on the physiological actions of muscle cell-derived EV. Applying FFSS to C2C12 cells significantly enhanced muscle cell-derived EV-suppressed osteoclast formation and several osteoclast-related gene levels in mouse bone marrow cells in the presence of receptor activator nuclear factor κB ligand (RANKL). Moreover, FFSS to C2C12 cells significantly enhanced muscle cell-derived EV-suppressed mitochondria biogenesis genes during osteoclast formation with RANKL treatment. In addition, FFSS to C2C12 cells significantly enhanced muscle cell-derived EV-suppressed osteoclast formation and several osteoclast-related gene levels in Raw264.7 cells in the presence of RANKL. Small RNA-seq-analysis showed that FFSS elevated the expression of miR196a-5p and miR155-5p with the suppressive actions of osteoclast formation and low expression in mouse bone cells. On the other hand, muscle cell-derived EVs with or without FFSS to C2C12 cells did not affect the expression of osteogenic genes, alkaline phosphatase activity and mineralization in mouse osteoblasts. In conclusion, we first showed that FFSS to C2C12 cells enhances the suppressive effects of muscle cell-derived EVs on osteoclast formation in mouse cells. Muscle cell-derived EVs might be partly involved in the effects of mechanical stress on the muscle/bone relationships.
Highlights
Numerous clinical studies about the relationships between sarcopenia and osteoporosis suggest that skeletal muscle and bone interact each other [1,2]
Size distribution of Myo-Extracellular vesicles (EVs) and fluid flow shear stress (FFSS)-Myo-EVs were similar (Fig 1B). These results suggest that exposing FFSS does not affect the amount and size of EVs secreted from C2C12 cells
These data indicate that FFSS influences EVs secreted from mouse muscle cells, leading to an enhancement of muscle cell-derived EV-induced suppressive effects on osteoclast formation and mitochondrial biogenesis in mouse cells
Summary
Numerous clinical studies about the relationships between sarcopenia and osteoporosis suggest that skeletal muscle and bone interact each other [1,2]. Effects of shear stress to muscle cells on the bone actions of muscle cell-derived extracellular vesicles. T.; the 2019 Kindai University Research Enchancement Grant (SR03) to Y.
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