MMP9 and pulmonary arterial hypertension: Vascular smooth muscle cell migration and secretion of various extracellular matrix (ECM) proteins (mainly MMP2 and MMP9) by macrophages also contribute to the vascular remodelling.27 Furthermore, the release of MMP2 and MMP9 promotes VSMC proliferation and migration.28, 29 TQ decreased migration and invasion, as well as the expression of MMP9 and MMP2 in A549 cells and human glioblastoma cells.30, 31 More importantly, TQ reduced vascular remodelling via MMP2 in PAH model according to our previous study.