Pursuing mechanisms of extracellular vesicle formation. Effects of sample processing

Although the role of extracellular vesicles in inter-cell communication is acknowledged, their analytics is yet problematic. Poor understanding of effects of sample processing may be one of the cornerstones of this issue. We investigated the effects of centrifugation during the vesicle isolation on the number, size, content and shape of particles in the isolates. Particles in the range of about 100-500 nm as observed by the scanning electron microscope exhibited characteristic shapes of vesicles without internal structure. Enhanced centrifugal pull resulted in increased amount of certain types of proteins in the isolates. Majority of present proteins were highly abundant human plasma proteins, including albumins and immunoglobulins. Results are in favor of the hypothesis that the isolated particles reflect the substance from which they originate (cells and the surrounding solution) and the performed processing; and therefore, vesicles in isolates should be viewed upon as a dynamic material with transient identity.