In our animal model with PAH and associated perivascular and interstitial fibrosis induced by MCT, a series of plasma proinflammatory cytokines (ET-1, TGF-β1, IL-1β, TNF-α) and tissue profibrotic molecules (COL1A1, Fibronectin, MMP-9, CTGF, Calponin, Vimentin, α-SMA) had increased protein expressions. This evidence concerns the gene MMP9 and pulmonary arterial hypertension.