Figure 3.

Schematic illustration of MSC-derived exosome-guided macrophage reprogramming. MSC-derived exosomes can induce a conversion of M1 to M2 Mφs and accelerate musculoskeletal tissue healing. Mφs could be activated by inflammatory chemokines and then to produce proinflammatory factors. This creates a feedback loop whereby proinflammatory cytokines produced by Mφs stimulate MSC to produce immune modulators, such as exosomes or EVs. Therefore, the formation of exosomes begins with membrane invagination in the form of endosomes, leading to the development of the early endosomes. Upon maturation, the endosomes become multivesicular endosomes, which release their contents in the form of exosomes.