Extracellular vesicles (EVs) are microparticles, ranging in size from tens of nanometers to microns, found in almost all biological fluids. Extracellular vesicles (EVs) include exosomes and exomeres (particles less than 120 nm in size), microvesicles (from 100 to 250 nm), and apoptotic bodies - particles larger than 200 nm. Exosomes and exomeres are of considerable interest since they are biological markers of the state of cells, which can be used for diagnostics, regulatory functions, and can be involved in intercellular signaling. The nomenclature of exosomes remains poorly developed. Most researchers try to classify them based on the mode of formation, physicochemical characteristics (size, density, etc.), and the presence of tetrasporin markers CD9, CD63, and CD81. It was shown in 2010 using the dynamic light scattering method that the histogram of the size distribution of exosomes (PSD) is bimodal: EVs are divided into two fractions with average sizes of about 25 and 90 nm. Despite this fact, only in 2018 by the method of fractionation in a force field ( asymmetric flow field-flow fractionation - a4f ) two subtypes of exosomes were identified, as well as particles which were called "exomeres", with a size less than 50 nm, differ from exosomes in protein and lipid composition. However, to date, the debate continues whether exomeres are produced by cells, or are the product of cell death. The data presented in this work show that although exomeres carry biomarkers characteristic of EVs, they differ from exosomes strongly in lipid composition, especially in cholesterol content. The production of exomeres by cells, both in culture and in vitro, is associated with the synthesis of cholesterol in cells and is expressed or suppressed by regulators of the synthesis of mevalonate, an intermediate product of cholesterol metabolism. In addition, the work shows that the concentration of explosives in the body correlates with the concentration of cholesterol in the plasma, but weakly correlates with the concentration of cholesterol in lipoproteins. This suggests that not all plasma cholesterol is associated with lipoproteins, as previously thought. Thus, exomeres are not a product of cell death and play an essential role in the transport of cholesterol in blood plasma.
Extracellular vesicles, exosomes, exomers, tetrasporins, cholesterol, lipoproteins, dynamic light scattering method
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