Urinary exosome and beyond

Abstract

The first publication on exosomes dates back to the 1980’s. Exosomes are membrane-derived vesicles that are specified by particle size (30–100 nm in diameter), density (1.13–1.19 g/mL), and surface markers. Once referred to as a “rubbish bag” to wrap up and dump out waste, the term “exosome” gained newfound meaning following the discovery of its biogenesis mechanism via multivesicular bodies and the joint effort of Nobel Prize winners, Sudhof, Schekman and Rothman, in discovering the machinery of vesicle transport. For the past decade, the number of exosome-related publications upsurged from fewer than 20 in the year 2001 to more than 1,000 in the year 2015. The nomenclature pertaining to “exosomes” was ambiguously used in literature, that is, “extracellular vesicles (EVs)” and “exosomes” were often used interchangeably or imprecisely. The criteria for exosomes have been refined over the decades to distinguish exosomes from other EVs (e.g., ectosomes, microvesicles and apoptotic bodies, see Table 1 ) by expression of distinct molecular markers such as TSG101, Aliex and CD63, and nanometer size in exosomes. However, the surface markers are overlapped in EV subgroups, making it fairly difficult to set a clear boundary. In this article, we will use “exosomes”, unless a specific subpopulation of EV is mentioned.