Scheme 1.

Cell‐free bone tissue regeneration by the stem cell derived exosomes. a) Exosomes were isolated from the pre‐differentiated hMSCs induced by the osteogenic medium for 4, 10, 15, 20 days, respectively. Osteogenic differentiation was tested to identify the exosomes that could induce the osteogenic differentiation of hMSCs. b) Representative structure and morphology of Ti‐scaffolds (8 mm in length and 3 mm in diameter). c–e) Osteogenic exosomes were seeded into the Ti‐scaffolds, which were then implanted into the rat radial bone defect model (d and e) for 4 and 12 weeks, respectively.