Fig. 1: MSCs regulate innate immune cells.

A MSCs regulate neutrophil. i) MSCs enhance phagocytosis activity; ii) MSCs convert activated neutrophils to senescent neutrophil phenotypes by upregating CD24 expression; iii) MSCs reduce neutrophil infiltration, decrease the expression of TNF-α, IL-6 and IL-1β, and increase IL-10; iv) MSCs derived exosomes can prevent excessive NETs formation by transferring miR-17-5p to target the TLR-4/ROS/MAPK pathway. B MSCs regulate macrophage. i) MSCs inhibit the activation of NLRP3 and NLRC4 inflammasome in macrophages and improved phagocytosis function, thereby inhibiting inflammation; ii) MSCs inhibit macrophage autophagy through miR-384-5p/Beclin-1 and HO-1 signaling pathways; iii) MSC-Exo miR-150-3p inhibits M1 polarization by down-regulating IL-6, IL-1β, iNOS, and promotes M2 polarization by up-regulating IL-10 in LPS-stimulated macrophages; iv) MSC-Exos can transfer stem cell-derived mitochondrial components to alveolar macrophages; v) MSC-Exo miR-451 regulates the MIF-PI3K-AKT signaling pathway to promote the polarization of macrophages M1 to M2; vi) PD-1 expressed on apoptotic bodies interacts with PD-L1 expressed by macrophages to shift macrophage metabolism from glycolysis to oxidative phosphorylation.