HIF1A and Duchenne muscular dystrophy: Although we did not examine whether long-term exosome exposure still stimulated either of these pathways, comparative analyses of the exosome surface proteome revealed that DMD-exo contained peptides associated with protective signaling, such as MAPK and adrenergic signaling, in addition to peptides associated with cell injury pathways, such as apoptosis and HIF-1α.