Exosomes: Extracellular and extraordinary

Even though they’re in the nanometer range, extracellular vesicles (EVs) could start to make it big in the next few years. Long ignored as “cell debris”, the tiny bubbles have now been recognized as a key component in the complex communication between cells. EVs carry genetic material and proteins throughout the fluids in the body, and have biological properties comparable to stem cells – but apparently safer. They could serve as vaccines, carry cancer immuno­therapies, or play a role in regenerative medicine. Ideas and potential markets are growing fast.

“People are now slowly beginning to recognize that we’re not talking about artefacts or accidental debris in cells, but instead a whole new system of cell communication that influences regenerative processes, inflammation and even tumourigenesis in the human body,” says Bernd Giebel, a pioneering German EV researcher and stem-cell biologist at Essen University Clinic. In 2008, only around 50 papers were published on the topic. Eight years later, that number has exploded to well over 2,000 annually. In August, the microbubbles even earned their own dedicated Gordon Conference. “The field is still in its infancy, but we’ve seen fast development in the last few years,” says Giebel.  

The first suggestion that cells shed micro­vesicles to the extracellular space not by accident but as a result of a specific biological process came in 1977, and observed in electron microscopy six years later. But for a long time, little was known about their function. Only around twenty years later could researchers prove that vesicles deriving from B-cells are able to stimulate immune reactions in T cells.

One of the turning points for the field in terms of attention was a paper published in 2006 in Leukemia by Mariusz Ratajzak, who was still at the University of Louisville in the US at the time. Although it took him three years to convince editors and reviewers, the well-known stem-cell researcher finally delivered a key message to the scientific community: EVs from embryonic stem cells transfer RNA and protein to blood precursor cells, and change their developmental fate. Since then, extracellular vesicles have been viewed as mediators of information, and have been identified as influential factors in the behaviour and even developmental fate of recipient cells. In fact, they appear to be involved in almost every physiological and pathological process, including neurodegeneration, cancer and inflammation. 

Read the full background on exosomes in our print magazine!