TGFB1 and pulmonary arterial hypertension: The most common molecular pathways altered in PAH include the bone morphogenetic protein (BMP), TGF-β pathway, abnormal micro-RNA expression, increased growth factors (platelet-derived and vascular endothelial growth factors among others), altered inflammatory pathways (interleukins IL-6, IL-1β), mitochondrial metabolism, other neurohormonal pathways (i.e., serotonin, adrenergic), prostacyclin/cAMP/PKA, endothelin/calcium signaling, and NO/sGC/cGMP/PDE5 all leading to endothelial dysfunction and abnormal SMC proliferation and reduced apoptosis [25].