EXOSOMES: CAN DOCTORS STILL IGNORE THEIR EXISTENCE? Celeste Caruso Bavisotto, Antonella Marino Gammazza, Francesca Rappa, Alberto Fucarino, Alessandro Pitruzzella, Sabrina David, Claudia Campanella Cell-to-cell communication is imperative for life. Intercellular communications are medi- ated through “sending” and “receiving” information via the secretion and subsequent receptor-mediated detection of biomolecular species (1). Each type of cell exhibits a par- ticular set of receptors that allows it to respond to a corresponding number of signal molecules produced by other cells and these ligands act in combination to influence cell behavior (1). There are many pathways of intercellular communication such as the pres- ence of signaling molecules on plasma membranes or secretion of soluble ligands. A number of evidences have now demonstrated new mechanisms of intercellular interaction through lipid vesicles (2, 3). The extracellular vesicles are constituted by a lipid bilayer that contains in its lumen both transmembrane and free proteins, RNA and microRNA; based on their composition and size these vesicles can be categorized into various classes such as exosomes, apoptotic bodies, microparticles, etc. (4). In recent years many studies have focused on exosomes, a particularly important class of extracellular vesicles (5). Exosomes are 30-100 nm wide membranous vesicles first described in 1984 by Pan and Johnstone in maturing mammal- ian reticulocytes as a mechanism for removal of plasma membrane proteins (6); over the years they have been observed to be secreted into the culture medium from a large num- ber of cell types, including T cells, B cells, dendritic cells, platelets, epithelial cells and cancer cells (3, 5, 7- 9). Recent studies have reported the isolation and characterization of these vesicles in Invited Commentary © EUROMEDITERRANEAN BIOMEDICAL JOURNAL 2013, 8(22):137-139. DOI: 10.3269/1970-5492.2013.8.22 Available on-line at: http://www.embj.org SUMMARY With this invited commentary we want to draw the attention of young medical doctors, the main readers of this journal, towards the existence and importance of a group of nanovesicles released by human cells: the exosomes. These vesicles are incontinently se- creted as a mean of cell-to-cell communication. They are involved in a number of physiol- ogic processes as well as in the pathogenesis of, virtually, all human diseases. They can be isolated from all biological fluids, like blood, urine, sweat, sperm, crevicular fluid, bile, etc., and their composition in terms of proteins, RNA and lipids is different in pathology that in physiologic conditions. It is therefore possible to predict that they will become an important diagnostic and therapeutic tool in medicine. Address of the authors Human Anatomy Section, Department of Experimental Biomedicine and Clinical Neurosci- ences, University of Palermo, Italy. Send correspondence to: Claudia Campanella; claudia.campanella@unipa.it Received: September 29th, 2013 — Revised: October 9th, 2013 — Accepted: October 20th, 2013 ISSN 2279-7165 - Euromediterranean Biomedical Journal [online]