MAPK3 and systemic sclerosis: 1. PAR2 immunoreactivity in fibroblasts of SSc skin, but not in healthy skin.2. PAR2 co-localized with 21 ± 8% a-SMA-positive myofibroblasts in SSc skin.3. PAR2-induced intracellular calcium mobilization in HDF after bleomycin pretreatment.4. PAR2 silencing prevents sDPP4-induced ERK1/2 activation, NF-κB phosphorylation, and pro-inflammatory factors upregulation in human smooth muscle cells.5. PAR2 antagonist or knocking down PAR2 can prevent sDPP4–induced fibrotic marker expression via SMAD/NF-κb signaling in fibroblasts.