Exosomes from mesenchymal stem/stromal cells: a new therapeutic paradigm

Mesenchymal stem/stromal cells (MSCs) have been demonstrated to hold great potential for the treatment of several diseases. Their therapeutic effects are largely mediated by paracrine factors including exosomes, which are nanometer-sized membrane-bound vesicles with functions as mediators of cell-cell communication. MSC-derived exosomes contain cytokines and growth factors, signaling lipids, mRNAs, and regulatory miRNAs. Increasing evidence suggests that MSC-derived exosomes might represent a novel cell-free therapy with compelling advantages over parent MSCs such as no risk of tumor formation and lower immunogenicity. This paper reviews the characteristics of MSC exosomes and their fate after in vivo administration, and highlights the therapeutic potential of MSC-derived exosomes in liver, kidney, cardiovascular and neurological disease. Particularly, we summarize the recent clinical trials performed to evaluate the safety and efficacy of MSC exosomes. Overall, this paper provides a general overview of MSC-exosomes as a new cell-free therapeutic paradigm.