What Are Exosomes?

By Rikinari Hanayama, Professor, Department of Immunology, Kanazawa University Graduate School of Medical Sciences

In recent years, research of extracellular vesicles (EVs) has been advancing at an accelerating pace. While the number of scientific articles on EVs published in 2011 was approximately two hundreds, the number increased to more than one thousand in 2016 and involvement of EVs in various physiological functions and pathogenic mechanisms has been suggested. Although EVs are roughly classified into at least two categories: exosomes derived from endosomes and microvesicles derived from plasma membrane, it is difficult to strictly separated them from each other by differential centrifugation, the technique most frequently used for purification of EVs at present, and the EVs not sedimenting at 10,000×g are called "small EVs" (mainly composed of exosomes) for convenience.¹