For example, MSC-sEVs derived let-7b inhibited TLR4 expression, thus reducing the downstream activation of MKK3/6 and decreasing p38 phosphorylation [43], while miR-21 delivered by MSC-sEVs downregulates p38 MAPK to modulate β-cell apoptosis in diabetes [44]. Here, MAP2K3 is linked to diabetes mellitus.