Reproducibility of extracellular vesicle research.

Cells release membrane-delimited particles into the environment. These particles are called "extracellular vesicles" (EVs), and EVs are present in fluids contacting cells, including body fluids and conditioned culture media. Because EVs change and contribute to health and disease, EVs have become a hot topic. From the thousands of papers now published on EVs annually, one easily gets the impression that EVs provide biomarkers for all diseases, and that EVs are carriers of all relevant biomolecules and are omnipotent therapeutics. At the same time, EVs are heterogeneous, elusive and difficult to study due to their physical properties and the complex composition of their environment. This overview addresses the current challenges encountered when working with EVs, and how we envision that most of these challenges will be overcome in the near future. Right now, an infrastructure is being developed to improve the reproducibility of EV measurement results. This infrastructure comprises expert task forces of the International Society of Extracellular Vesicles (ISEV) developing guidelines and recommendations, instrument calibration, standardized and transparent reporting, and education. Altogether, these developments will support the credibility of EV research by introducing robust reproducibility, which is a prerequisite for understanding their biological significance and biomarker potential.