Emerging roles of extracellular vesicles in physiology and disease.

Extracellular vesicles (EVs), such as exosomes and microvesicles, are small membrane vesicles secreted by almost all cell types and are abundant in blood, body fluids, such as urine, spinal fluid, tears and saliva, and cell culture media. From an evolutionary perspective, they are biologically significant as a means for expelling unwanted cellular contents. Recently, EVs have received considerable attention as messengers of intercellular communication networks, allowing the exchange of proteins and lipids between the cells producing them and target cells that trigger various cellular responses. EVs also carry mRNAs and microRNAs inside them, transferring genetic information among cells. In addition, the expression pattern of these molecules is related to the cellular state and the progression of diseases, and the search for biomarkers within the EV is underway in many research fields. However, the physiological and pathophysiological roles of EVs remain largely elusive. Therefore, in this special issue, we have compiled reviews of the latest research findings on EV research.