HGF and pulmonary arterial hypertension: Finally, knockdown of HGF in the lungs in early disease stage exacerbated PH in male rats characterized by higher mortality, worsened RV and PA function as well as enhanced PA medial thickening and adventitial fibrosis.<h4>Conclusions</h4>Lung HGF expression may be upregulated to counteract PAH disease progression by inhibiting proliferation of PASMC and PAFB.