Nanoparticle tracking analysis of extracellular vesicles reveals two populations of exosomes

Exosomes are extracellular vesicles of 30 to100 nm in diameter, which are secreted by various cells of mammals. It is known that exosomes represent a specific way of cell-to-cell communication. Mechanisms of secretion and uptake of these vesicles are not clear. To address this problem, we fused the transmembrane protein CD63, a known exosomal marker, at its N-termini to the EGFP protein. We have shown that these proteins exit cells as a part of exosomes, substantiated by the fluorescent nanoparticle tracking analysis. The analysis has also shown that there are two prevailing exosome populations in general population of vesicles.