BDNF and neurodegenerative disease: Preclinical studies have investigated EV-mediated delivery of neurotrophins (e.g., brain-derived neurotrophic factor, nerve growth factor), growth factors (e.g., insulin-like growth factor 1, fibroblast growth factor), and anti-apoptotic proteins (e.g., Bcl-2, XIAP) for promoting neuronal survival, axonal regeneration, and functional recovery in neurodegenerative diseases [120, 121].