Exosomes are a heterogenous subpopulation of extracellular vesicles 30–150 nm in range and of endosome-derived origin. Despite more than 30 years of research that followed their definition and indicated their important role in cellular physiology, the exosome biology is still in its infancy with rapidly growing interest. The reasons for the rapid increase in interest with respect to exosome biology is because they provide means of intercellular communication and transmission of macromolecules between cells, with a potential role in the development of diseases. Moreover, they have been investigated as prognostic biomarkers, with a potential for further development as diagnostic tools for neurodegenerative diseases and cancer. The interest grows further with the fact that exosomes were reported as useful vectors for drugs.
Researchers from the Poznan University of Medical Sciences explored the exosome formation through different systems, including the endosomal sorting complex required for transport (ESCRT) and ESCRT-independent system, looking at the mechanisms of release. Different isolation techniques and specificities of exosomes from different tissues and cells are also discussed.
Endocytic pathways in the process of exosome biogenesis
Different steps of exosome biogenesis are demonstrated including early endosome formation, late endosome formation and multivesicular body (MVB) formation, respectively. MVB is then either transported into the lysosome for lysosomal exocytosis or fused with the endosomal membrane followed by exosomes release into the extracellular space. Two main organelles are shown including Golgi apparatus and endoplasmic reticulum due to their interaction with early endosomes as soon as they are formed from endocytic vesicles.