TGFB1 and pulmonary arterial hypertension: p38 MAPK is another member of the MAPK superfamily that is upregulated in PAH, whose activation is correlated with fibroblast-to-myofibroblast differentiation by pathways dependent on TGF-β1 and TRPC6 [39], and increased collagen synthesis and depositing by RV fibroblasts [40].