Extracellular vesicles of mesenchymal stem or stromal cells. From bench to bedside

With the beginning of the new millennium, great hopes were placed in the rapidly developing field of stem cell research. It was and is the goal to develop stem cell therapies that help to successfully treat a wide range of degenerative diseases as well as more acute diseases such as stroke or myocardial infarction. Conceptually, it was assumed that injected stem cells or their descendants migrate into affected tissues and replace lost cell types via transdifferentiation, thus alleviating disease associated symptoms. At that time, human embryonic stem cells came into focus of scientific interest. However, due to their high teratogenic potential and ethical explosiveness they could not be used for stem cell therapies. Instead, various somatic stem cell types were considered and used as therapeutic agents.