Neuronal extracellular vesicles mediate BDNF-dependent dendritogenesis and synapse maturation via microRNAs

Extracellular vesicles (EVs) have emerged as novel regulators of several biological processes, in part via the transfer of EV content such as microRNA; small non-coding RNAs that regulate protein production, between cells. However, how neuronal EVs contribute to trans-neuronal signaling is largely elusive. We examined the role of neuron-derived EVs in neuronal morphogenesis downstream signaling induced by brain-derived neurotrophic factor (BDNF). We found that EVs perpetuated BDNF induction of dendrite complexity and synapse maturation in naive hippocampal neurons, which was dependent on the activity of three microRNAs, miR-132-5p, miR-218 and miR-690. These microRNAs were up-regulated in BDNF-stimulated EVs. Moreover, supplementation with BDNF-EVs rescued the block of BDNF-induced phenotypes upon inhibition of miRNA activity. Our data therefore suggest a major role for EVs in BDNF-dependent morphogenesis, and provide new evidence for the functional transfer of microRNAs between neurons. This is not only an important step towards understanding the function of EVs in inter-neuronal signaling, but is also relevant for many disorders characterized by decreased BDNF signaling, such as major depression or cognitive impairment.