Research in extracellular vesicles has skyrocketed since its discovery 30 years ago due to its potential medical applications in treating diseases such as cancer, because of its essential role in remote communication between cells. This is one of the current lines of research of Dr. Antonio Marcilla, Professor at the Department of Cell Biology and Parasitology at the University of Valencia, and member of the GEIVEX Managing Board (Spanish Group of Innovation and Research in Extracellular Vesicles). Marcilla completed his training as a researcher at the course on extracellular vesicles, held at the premises of Menéndez Pelayo International University in Valencia. Marcilla talks about these spheres that «some even describe as if they were soap bubbles».
How would you define extracellular vesicles? They are spheres surrounded by a lipid membrane that are actually remodelling our approach to communication channels between cells. In countries like ours there are more mobile phones than people, so it seems that communication today is mediated by these devices. In other words, it is not directly between people. That is how we could compare the functioning of extracellular vesicles, which are supposed to communicate cells that can be found over long distances.
Why do they suppose a medical revolution? Undoubtedly, the medical revolution has been brought by the fact that,until recently, there were only two known types of communication channels between cells, either through direct contact, from cell to cell, or through certain molecules. Extracellular vesicles are the third communication channel between cells. They are important because they represent a new way of remote communication.
Do all extracellular vesicles carry information? The term extracellular vesicle is wide. It includes vesicles such as exosomes, which are between 30 and 100 nanometers and are produced within the cell and exported as such in multivesicular bodies. There is also a second group of vesicles, a little older, that can reach even 1,000 nanometers (1 micron). They are called microvesicles. These are not produced from within, but extruded from the plasma membrane. Finally there is a third type of vesicles, apoptotics, which are large vesicles produced by cells programmed before their death. All these vesicles contain proteins, nucleic acids, lipids (not just on the surface) and sugars. It has been described that some of these vesicles, which were initially waste material shippers, are also able to function in recipient cells. This has caused both a qualitative and quantitative leap in publications regarding these vesicles.
How can we generate vesicles that transport certain information? There are studies where vesicles from prokaryotic organisms have been purified. These vesicles, for example bacteria, are called «outer membrane vesicles» or gas surface, where their content can be edited as it is done with liposomes and some other membrane structures that are used in cosmetics for example. Q10 liposome lotions would be an example, which the skin absorbs better. They are membranous structures which have a composition artificially introduced inside them. Vesicles that are naturally-occurring or produced by living organisms can be manipulated to incorporate the desired material therein. They are recognized by the host cell as they are natural vesicles, therefore it is possible to send a particular component or signal to the target cell.
Does the nanoscopical scale represent a challenge for your research? It is certainly a major constraint. For example, the fact that we have to use electron microscopy techniques in order to watch them and manipulate each lot to be identical to the previous one or to have a different composition. It is an important limiting factor to resort to such sophisticated and expensive techniques. Techniques based on principles of loading vesicles are being developed, so they can be detected for example by flow cytometry or by some kind of system that is also faster and more reliable. But today there are no 100% reliable and marketable detection systems.
Is there any chance of using vesicles from other organisms to end human diseases? Yes, in theory. What has been documented to date is the use of extracellular vesicles produced by culture cells from a patient with terminal cancer (lymphoma). These vesicles that were incorporated into the same person were able to prolong his lifespan. Also, exosomes that have been used in certain patients to improve different pathologies have been reduced from culture cells. The fact that vesicles from other organisms are being used is also being considered in current research lines. For example, vesicles could be designed for a given treatment from bacteria.
And also from worms? Most studies today use extracellular vesicles derived from culture cells, which may be from mammals, usually mice, human cells, etc. But it is true that helminths also produce these vesicles. In fact, our research group has first described the role of these vesicles in communication with the host. Moreover, it has been previously seen that some materials of these parasites can modulate the immune response in the host, so it is not unreasonable to think that these vesicles could also have that effect and act upon certain diseases.
What are the purification techniques of extracellular vesicles about? There are several types of techniques. Ultracentrifugation is a very high speed centrifugation. As extracellular vesicles are very small they require high speed to be sedimented. Throughout their purification, differential centrifugations are made to eliminate firstly whole cells, and secondly cellular debris, organelles, etc., since they have larger structures than vesicles. In order to reach smaller size vesicles, there is no way to purify them unless we use a high speed centrifugation, above 100,000 g. This is the conventional vesicle purification technique, but ultracentrifuged vesicles have limited volume capacity that can be processed in one operation. If a hospital had to ultracentrifugate hundreds of samples it would take months of work. That is why we are investigating the possibility of using other technologies to isolate these vesicles without using ultracentrifugation. There are already some testing protocols. For example, precipitations with substances like polyethylene glycol, chromatography columns by molecular filtration, affinity, etc. In short, techniques which have previously been used for very small structures such as viruses, and can now be used for these vesicles that have similar sizes.
Could the cell degradation that comes with aging be addressed and corrected with extracellular vesicles? The potential of these vesicles is extraordinary because they are involved in any type of process, as we are seeing. Of course, one of them is cell senescence. If we find out which mechanisms trigger aging we could send a signal to block precisely those mechanisms. The possibilities are enormous. Not so long ago, a study was published where it seems that baldness is related to an occurrence of circulatory system in the scalp. Precisely this angiogenesis, which is the name of the process of producing vascularization in certain areas, is also mediated by extracellular vesicles.
In short, could we say that all diseases based on cell failure would have a possible solution by treating them with extracellular vesicles? Any disease in which there is communication between a pathogenic cell and a healthy cell is sensitive of being locked by means of this kind of vesicles, blocking the erroneous vesicles or producing new ones that replace them.
What application might vesicles have in the production of vaccines? From bacteria, vesicles induce a modulation or a change in the immune system and this naturally has a great applicability in vaccines. In the case of bacterial diseases, it has already been seen that some may be preventable by previously managing vesicles from these pathogen organisms. In the case of parasitic diseases such as malaria, caused by Plasmodium vivax, exosomes produced by cells infected with the parasite could be used to immunize people who have had no contact with the pathogen yet. In fact, they have already been tested in animals with very good results.
«The extracellular vesicles are supposed to communicate cells that can be found over long distances»
«Vesicles that are naturally-occurring or produced by living organisms can be manipulated to incorporate the desired material therein»
«Vesicles could be designed for a given treatment from bacteria»
«Any disease in which there is communication between a pathogenic cell and a healthy cell is sensitive of being locked by means of extracellular vesicles»
«In the case of bacterial diseases, it has already been seen that some may be preventable by previously managing vesicles from these pathogen organisms»
Teresa Coll 
Teresa Coll
