To confirm whether long-term DMD-exo exposure was promoting the disease pathogenesis or merely failing to protect DMD-iCMs undergoing stress, exosome production and secretion was inhibited for 24 h with GW4869, a neutral sphingomyelinase (nSMASE) inhibitor (Trajkovic et al., 2008), followed by assessment of the functional stress response. Here, SMPD2 is linked to Duchenne muscular dystrophy.