Toward Standardization of Mesenchymal Stromal Cell-Derived Extracellular Vesicles for Therapeutic Use: A Call for Action.

Extracellular vesicles (EVs), which include a variety of nano-sized membrane-encapsulated particles, are released to the extracellular microenvironment by the vast majority of cells and carry lipids, proteins, mRNA, and miRNA or non-coding RNA. Increasing evidence suggests the great versatility and potential of EV-based applications in humans. In this issue, van Balkom et al. explore and compare the reported proteomic signature of mesenchymal stromal cell (MSC)-derived small EVs. In particular, their paper offers a valuable approach and point of view on MSC-EV manufacturing and therapeutic potential. Briefly, van Balkom et al. aimed to identify a common protein signature that may be useful in ensuring the homogeneity of therapeutic MSC-EVs. In addition to excessive variability in EV-producing cell sources and culture conditions, the harvesting time for the EV-containing conditioned medium, and EV isolation procedure, the authors found a specific protein signature from the publicly available MSC-EVs proteome. In light of their findings and those from the plentiful studies published in this continuously growing area of research, potential focus areas and issues are outlined for the more rational design and optimization of MSC-EV production and potency for therapeutics.