RTN4 and osteoporosis: Our results showed that exosomes derived from circ-Rtn4-modified BMSCs (Rtn4-Exos) inhibited TNF-α-induced cytotoxicity and apoptosis in murine MC3T3-E1 cells via regulating miR-146a expression, thus indicating that Rtn4-Exos may serve as novel agents for the treatment of osteoporosis.