Figure 1.

Schematic diagram showing roles of bone‐derived exosomes in regulating bone remodelling. Bone‐derived exosomes can regulate differentiation of osteoclasts and osteoblasts by transferring biologically active molecules to target cells. Osteoclast precursor‐derived exosomes (A) stimulate the differentiation of osteoclasts and osteoblasts. Osteoclast‐derived exosomes (B) reduce the number of osteoclasts formed and osteoblastic bone formation. Furthermore, osteoclast‐derived exosomes containing miR‐214 may promote the osteoclast differentiation. Osteoblast‐derived exosomes (C) promote differentiation of osteoblasts and osteoclasts, as well as establish a positive feedback in bone growth. In addition, osteoblast‐derived exosomes containing OPG may inhibit the osteoclast differentiation. Osteoblast precursor‐derived exosomes (D) induce MSCs to differentiate into osteoblasts. Dotted boxes indicate the primary contents of bone‐derived exosomes that are involved in bone remodelling. Short black arrows indicate the secretion process. Dotted black arrows indicate the translocation of cells. Solid blue arrows indicate the differentiation process. Solid red arrows indicate the promotion of cellular processes, and solid green lines indicate inhibition of cellular processes. Dotted lines indicate that the mechanism has not been fully elucidated.