7. The immunomodulatory effects of mesenchymal stem cells

Beside cell-to-cell contact, the MSCs secret many factors including EVs and soluble factors modulating the inflammatory response. The main paracrine factors are TGF-β, prostaglandin E2 (PGE2), hepatocyte growth factor (HGF), IL-10, IL-6, indoleamine 2,3-dioxygenase (IDO), nitric oxide (NO), and human leukocyte antigen G (HLA-G). Each of these factors plays an important role in regulation of different target immune cells. Other than such soluble factors, MSCs secrete extracellular vehicles (EVs), lipid bilayers that contain and transport the cytoplasmic components of the MSCs. EV is an inclusive term that has recently been suggested to encompass both exosomes and microvesicles. The immunological potential of MSC EVs in vitro, and the ability of these EVs to attenuate an activated immune system in vivo have been reported [31].
