ACTA2 and idiopathic pulmonary arterial hypertension: Staining against endothelial cell (EC), SMC, fibroblast, and immune cell markers (von Willebrand factor/VWF, ACTA2, decorin/DCN, and CD45, respectively), revealed the expansion of SMC coverage toward the distal PA vascular tree in IPAH lungs (Figure 1, A and B).