Moreover, the results of Western blot showed that hucMSC‐exosomes in H‐EXO and L‐EXO could distinctly inhibit the expression of apoptosis protein BAX in CVB3‐induced myocarditis mice, but just hucMSC‐exosome (50 μg, H‐EXO) could enhance the anti‐apoptosis protein Bcl‐2 in CVB3‐induced myocarditis mice (Figure 4C,D). Here, BAX is linked to myocarditis.