04/11/2026
Extracellular vesicles (EVs), including exosomes, are small membrane-bound particles released by cells. They can carry proteins, lipids, and RNA—including microRNA—and may influence recipient cells through surface interactions or uptake.
Their labels and sizes should be interpreted carefully. Commonly cited ranges are 30–150 nm for exosomes, 100–1,000 nm for microvesicles, and 50–5,000 nm for apoptotic bodies, but these distributions overlap. One nanometer is one-millionth of a millimeter.
The MISEV2023 guidelines from the International Society for Extracellular Vesicles (ISEV) advise against identifying a particle as an exosome based on size alone. Markers such as CD63, CD9, and CD81 can support characterization, yet neither size nor these markers alone can establish exosome biogenesis. When this cannot be directly demonstrated, the term small extracellular vesicles (small EVs) is recommended.
Research findings also depend on the cells from which vesicles originate, along with isolation, analysis, and storage methods. Reliable characterization uses multiple complementary methods to assess particle size distribution and concentration, EV-associated proteins, and non-vesicular co-isolates.
Interest in extracellular vesicles has expanded in regenerative medicine, while important questions remain around manufacturing processes, homogeneity, purity, storage, biodistribution, and safety assessment. Cell-based and animal findings require separate clinical evidence to determine whether they apply to humans.
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