RTN4 and osteoporosis: Mechanistic investigations suggested that co-culture with Rtn4-Exos attenuated TNF-α-induced cytotoxicity and apoptosis in MC3T3-E1 cells, as evidenced by the decrease in cleaved caspase-3 and Bax protein expression and caspase-3 activity, thus suggesting that Rtn4-Exos may serve as potential candidates for the treatment of osteoporosis.