What are Exosomes?

Exosomes are a type of heterogeneous extracellular microvesicle (EMV) from a group that includes micro vesicles and apoptotic bodies. They are released from cells upon fusion of an intermediate endocytic compartment, the multivesicular body (MVB), with the plasma membrane. When we talk about exosomes we refer to extremely small bubbles that are released from cells, much smaller than a bacterium, with a diameter of between 30 and 200 nm.  They can carry a varied load, such as mRNA, non-coding RNA, proteins and lipids.  Exosomes are considered powerful communicators that carry all the signalling and the machinery necessary to go to and change the behaviour of a neighbouring cell. 

There has been increasing interest in EMVs in recent years not only as possible biomarkers for disease, but as novel cell to cell communicators with a functional role in both normal physiology and morbid conditions. Exosomes collectively are a very powerful and new way of thinking how cells communicate long distance. 

The field of exosomes is not a new field. It was being studied by immunologists as far back as two decades but the level of research generally has been historically very low.  The turning point in exosome research was a discovery by group of scientists in the Netherlands in late 90s when exosomes from immune cells were discovered to be carrying part of the function that the immune cells performed. Since the discovery that exosomes have other properties besides simply being a means by which cells offload waste, the past few years have seen a huge change in the way scientists think about exosomes and a number of fascinating functions of these vesicles have been uncovered. 

Now that is we know that exosomes are deliberately released from cells, functioning as signal carriers and tissue reshapers through their consignment of RNA, proteins and lipids,  scientists are seeking to further understand the biology of exosomes by focussing on two main strands of research. Firstly, studies into the role they play as communicator, in that they serve as delivery vesicles for RNA and proteins molecules from one cell to another, enabling cell communication signalling. Additionally, there is a growing community of research that studies exosomes for diagnostic application; by analysing their protein and RNA payload different types of cancer, autoimmune and viral diseases can be detected. Exosomes are being analysed for their role in these general biological processes as well as for their use as biological markers, or possibly an instrument for specified delivery of biomolecules.