3.2. Internalization of EVs by BMSCs
To explore whether EVs could enter the cytoplasm of BMSCs, the six groups of EVs were labeled with green fluorescence dye PKH67 and incubated with BMSCs for 48 h. Fluorescence microscopy analysis showed that the BMSCs were capable of internalizing the EVs of all groups(Figure 3) . The internalized PKH67 fluorescence varied very little between EV groups and across cells within the culture, which suggests that the EVs were homogenously internalized.