Mikrovesikler

Mikrovesikler, or microvesicles, are extracellular vesicles released by cells through outward budding of the plasma membrane. They range in size from roughly 100 to 1000 nanometers and are found in various body fluids, including blood, urine, and saliva. This distinguishes them from smaller exosomes (approximately 30 to 150 nanometers), which originate within endosomal compartments, and from apoptotic bodies produced during cell death.

Biogenesis and cargo: Microvesicles form when cytoskeletal rearrangements and membrane blebbing drive outward budding. Increases in intracellular calcium and activation signals promote phospholipid redistributions, including exposure of phosphatidylserine on the surface. Their cargo reflects the parent cell and can include lipids, proteins, RNA, and even DNA fragments. Markers are not universal, but vesicles often carry surface proteins such as integrins or selectins that reflect their origin.

Functions and significance: Microvesicles participate in intercellular communication by transferring bioactive molecules to recipient cells, modulating signaling pathways. They contribute to coagulation and inflammation, influence immune responses, and are implicated in tissue repair and angiogenesis. In cancer, tumor-derived microvesicles can promote metastasis, alter the tumor microenvironment, and serve as potential biomarkers of disease.

Detection and standardization: Isolation and analysis commonly use ultracentrifugation, size-exclusion chromatography, or density gradients, often followed by nanoparticle tracking analysis, electron microscopy, or flow cytometry. Because markers are not universal, reporting follows guidelines from the International Society for Extracellular Vesicles (ISEV), such as MISEV recommendations, to improve comparability.

Clinical and research outlook: Microvesicles hold promise as disease biomarkers and potential therapeutic vectors, but challenges remain in standardization, quantification, and interpretation of cargo. Ongoing research seeks to clarify their roles in physiology and pathology and to establish robust methods for clinical use.