2.2.1. Extraction of Exos

When hWJMSCs reached 60% confluence, the culture medium was replaced with culture medium containing 10% Exo-free serum (SBI, EXO-FBS-50A-1) for 48 h, and the culture supernatant was collected. Differential ultracentrifugation was used to extract Exos (Fig. 2a). In short, centrifugal force of 300×g, 2000×g, 10000×g, and 100000×g was used to centrifuge the cell culture supernatant. The final pellet was resuspended in 200 μL of PBS. Exos were quantified using a bicinchoninic acid (BCA) protein quantification kit (Thermo Scientific, 23225).

(a) Extracted exosomes by differential ultracentrifugation. (b) Osteochondral defects model. Scale bar = 5 mm. (c) The ACECM scaffold was implanted into the defect site. (d) Groups used in the osteochondral defects repair experiments.