Most present stem cell therapies achieve their positive results through signaling rather than any other action of the transplanted cells. The transplanted cells die fairly rapidly, but their signals change the behavior of native cells for the better for some period of time. Most cell signals are delivered via some form of extracellular vesicle, small membrane-bound packages containing a wide variety of molecules. The contents and variety of vesicles are at this time very poorly cataloged, but it is still possible to make use of them. Vesicles can be harvested from cultured cell populations, and packaging such vesicles as a therapy is somewhat easier than managing cell treatments. As an example of the type, researchers here report on a demonstration in pigs in which they replace the delivery of stem cells with the delivery of extracellular vesicles derived from stem cells, and achieve good results.

Extracellular vesicles are matter that is released by cells. Seen for many years as not having any value, this 'cellular dust' has been studied and presents therapeutic properties similar to their mother cells, without their disadvantages: These vesicles do not divide, limiting the risk of cancer, and do not differentiate either, thus preventing the development of poor function. Furthermore, it appears that they can be produced by a single donor for several patients, and have already demonstrated their therapeutic potential in animals in repairing heart, liver and kidney lesions.

In the case of digestive fistula, in which there is abnormal communication between organs in the digestive tract or with the skin, regenerative medicine is an important therapeutic avenue to explore. Fistulas of this kind respond poorly to current treatments; they can develop following postoperative complications or an autoimmune disorder such as Crohn's disease, which causes digestive tract dysfunction.

For the first time, scientists used extracellular vesicles from stem cells to treat digestive fistula in a swine model. The study reveals that local injections into the fistula of a gel containing these vesicles results in the complete closure of post-operative digestive fistula. Researchers intend to test the new approach in a perineal fistula model found in Crohn's disease, with the hope of replacing the stem cell injections. The vesicle gel could be administered locally and easily and become a simpler, safer and more effective treatment.