Systemic administration of osteoblast-derived collagenase released extracellular vesicles restores trabecular bone...

Matrix vesicles (MtVs), a type of extracellular vesicles (EVs), are secreted by osteoblasts and initiate bone mineralization. Recent evidence suggests that MtVs are also involved in intercellular communication, inhibiting osteoclast formation, and promoting bone repair. These findings suggest that MtVs might hold therapeutic potential for osteoporosis; however, their effects on osteoporosis have incompletely remained understood. In this study, we investigated the effects of mineralized mouse osteoblastic MC3T3-E1 cell-derived collagenase-released EVs (MC-CREVs) on bone loss in ovariectomized mice, using C2C12 myotube-derived EVs (MT-EVs) as a control. MC-CREVs approximately 100 nm in size were isolated from collagenase-digested mineralized MC3T3-E1 cultures by density gradient ultracentrifugation. Systemic administration of MC-CREVs restored trabecular bone mineral density, bone volume, and trabecular thickness in ovariectomized mice, while the number of osteoclasts on the trabecular bone surface was decreased. In vitro experiments, MC-CREVs suppressed osteoclast formation and osteoclast marker gene expression induced by RANKL more effectively than MT-EVs in RAW264.7 cells. The miRNA array analyses showed that miR-1224-5p was abundantly expressed in MC-CREVs. In conclusion, we demonstrated that systemic administration of MC-CREVs is effective for trabecular bone loss presumably through suppression of bone resorption in ovariectomized mice.