Recent research has demonstrated that all body fluids assessed contain substantial amounts of vesicles that range in size from 30 to 1000 nm and that are surrounded by phospholipid membranes containing different membrane microdomains such as lipid rafts and caveolae. The most prominent representatives of these so-called extracellular vesicles (EVs) are nanosized exosomes (70-150 nm), which are derivatives of the endosomal system, and microvesicles (100-1000 nm), which are produced by outward budding of the plasma membrane. Nanosized EVs are released by almost all cell types and mediate targeted intercellular communication under physiological and pathophysiological conditions. Containing cell-type-specific signatures, EVs have been proposed as biomarkers in a variety of diseases. Furthermore, according to their physical functions, EVs of selected cell types have been used as therapeutic agents in immune therapy, vaccination trials, regenerative medicine, and drug delivery. Undoubtedly, the rapidly emerging field of basic and applied EV research will significantly influence the biomedicinal landscape in the future.
Exosomes, a natural source of nanoparticles to target cell membranes and deliver bioactive molecules or to be analyzed for biomarkers. (A) Extracellular vesicles are 50–300 nm vesicles surrounded by a lipid bilayer. Such physical characteristics are uniquely observed by cryo-electron microscopy (exemplified by a picture of exosomes derived from a human melanocytic cell line observed by cryo-EM. Credit: G. van Niel and A. Di Cicco. (B) Schematic representation of extracellular vesicles and the potential bioactive molecules and biomarkers that can be associated. Families of molecules of interest are classified by color codes as detailed in the text beneath. Credit: G. van Niel.
In this Perspective, a network of European scientists from clinical, academic, and industry settings collaborating through the H2020 European Cooperation in Science and Technology (COST) program European Network on Microvesicles and Exosomes in Health and Disease (ME-HAD), demonstrate the high potential of nanosized EVs for both diagnostic and therapeutic (i.e., theranostic) areas of nanomedicine.