FIGURE 1.

Biogenesis, secretion, and potential application of exosome. (I) Extracellular constituents and cell surface proteins entered cells through endocytosis. (II) The formation of the cell membrane budded in the luminal side. The fusion of the bud with the compositions of the endoplasmic reticulum, Golgi, and mitochondria gave rise to early sorting endosome formation. (III) Then, early sorting endosome led to late sorting endosome. (IV) The secondary invagination was modified with cargos, giving rise to the generation of various intraluminal vesicles and the formation of the multivesicular body. (V) At last, the exocytosis of the multivesicular body released intraluminal vesicles to the outside of cells in the form of exosomes. Many studies have demonstrated that exosome-based treatment was effective for OA, OP, and bone defects.