Extracellular vesicles at the neuromuscular junction: messengers of synaptic health and disease

Extracellular vesicles (EVs) have emerged as pivotal modulators of neuromuscular junction (NMJ) biology, reshaping our understanding of synaptic communication, maintenance, and degeneration. This review consolidates current insights into the roles of EVs derived from motor neurons, muscle fibers, and Schwann cells in regulating NMJ integrity. In healthy states, EVs deliver trophic factors, structural proteins, and regulatory RNAs that promote the clustering of acetylcholine receptors, presynaptic stability, and axonal growth. Motor neuron EVs carry Wnt7a, synaptophysin, and PGC-1α, while muscle-derived EVs deliver miR-206, agrin, and caveolin-3. Schwann cell EVs contribute neurotrophic support via NRG1 and GDNF. In contrast, diseased or aged NMJs exhibit EV cargo dysregulation, marked by the presence of misfolded proteins (e.g., SOD1, TDP-43), pro-inflammatory cytokines, and reduced regenerative miRNAs. These changes contribute to synaptic dismantling, neuroinflammation, and impaired repair in conditions such as ALS, SMA, MG, and sarcopenia. The review highlights the bidirectional nature of EV signalling and its dynamic regulation by neuronal activity and stress. Emerging therapeutic strategies include engineering EVs to deliver protective cargo, targeting them to NMJ components, and designing biomaterial-based depots for sustained release. Furthermore, EV signatures in blood and muscle hold promise as non-invasive biomarkers for early detection of NMJ decline in ALS, SMA, MG, and sarcopenia. Despite promising preclinical data, challenges remain in EV characterization, targeting specificity, and clinical translation. This review underscores a paradigm shift: EVs are not passive byproducts but active messengers of neuromuscular health and disease, with realistic applications in diagnostics, regenerative therapy, and personalized medicine.