Exosomes are small extracellular vesicles (30-120 nm) of endosomal origin, which are gaining the attention of the scientific community. Originally considered only a waste disposal system, they are now emerging as another class of signal mediators. Exosomes are secreted by any cell type and retrieved in every body fluid, such as blood, urine, saliva and amniotic liquid. Remarkably, their biochemical content includes not only lipids and proteins, but also nucleic acids, mainly miRNA and mRNA, with a few reports also indicating the presence of genomic and mitochondrial DNA. Their properties have stimulated extensive research to exploit them as a source of biomarkers for the diagnosis and the follow-up of several pathologies. Furthermore, exosomes are relatively robust and stable, so they appear attractive as gene and drug delivery vehicles. They have also revealed immunomodulatory and regenerative properties, which are encouraging their application for therapeutic purposes. Several issues remain to be addressed: exosome isolation is still time consuming and unsatisfactorily reproducible, making it difficult to compare results among laboratories, improve our knowledge of their physiological function and correlate their features with pathological outcomes. Nevertheless, the number of patents trying to address these problems is growing exponentially and many novelties will reach the scientific community in the next few years.
Keywords: Biomarkers, circulating nucleic acids, drug delivery, exosomes, exosome-like nanoparticles, extracellular vesicles, liquid biopsy, microvesicles, nanovesicles, neurodegenerative diseases, stem cell particles, theranostics, tumor diagnosis.