In vivo imaging of EVs in zebrafish: New perspectives from 'the waterside'

Abstract To harmoniously coordinate the activities of all its different cell types, a multicellular organism critically depends on intercellular communication. One recently discovered mode of intercellular cross‐talk is based on the exchange of "extracellular vesicles" (EVs). EVs are nano‐sized heterogeneous lipid bilayer vesicles enriched in a variety of biomolecules that mediate short‐ and long‐distance communication between different cells, and between cells and their environment. Numerous studies have demonstrated important aspects pertaining to the dynamics of their release, their uptake, and sub‐cellular fate and roles in vitro. However, to demonstrate these and other aspects of EV biology in a relevant, fully physiological context in vivo remains challenging. In this review we analyze the state of the art of EV imaging in vivo, focusing in particular on zebrafish as a promising model to visualize, study, and characterize endogenous EVs in real‐time and expand our understanding of EV biology at cellular and systems level.