Mesenchymal Stem/Stromal Cells as Biological Factories

Mesenchymal stem/stromal cells (MSCs) are factories of signaling molecules that affect diverse biological processes. MSCs respond to the microenvironment by releasing soluble factors that might regulate extracellular matrix remodeling as well as mitosis, angiogenesis, apoptosis, differentiation, and chemotaxis of target cells. The MSC secretome also modulates immune cells from innate and adaptive systems. MSCs might be considered as factories of extracellular vesicles (EVs) too. EVs include microvesicles, secreted by direct shedding of plasma membrane, and exosomes, formed inside the endosomal compartment and released to the milieu. MSC-EVs contain specific sets of molecules (lipids, proteins, nucleic acids) that function in cell-to-cell communication to maintain homeostasis and repair damaged tissues. These properties are under investigation in several disease models in trying to develop cell-free therapies for regenerative medicine. A caveat of these approaches is that MSC-EVs have anti- and protumorigenic activity. Much prudence and basic research is needed before these putative therapies reach the clinic.