After demonstrating the importance of myeloid-derived PDGF-B in experimental PH and the inductive effects of PDGF-B from macrophages of PAH patients on hPASMCs, we next aimed to pharmacologically downregulate this ligand in lung macrophages by delivering nanoparticles formed from a poly(amine-co-ester) (PACE) polymer and Pdgfb siRNA. Here, PDGFB is linked to pulmonary arterial hypertension.