Treprostinil increases the number and angiogenic potential of endothelial progenitor cells in children with pulmonary hypertension

Pulmonary vasodilators in general and prostacyclin therapy in particular, have markedly improved the outcome of patients with pulmonary arterial hypertension (PAH). As endothelial dysfunction is a key feature of PAH, and as endothelial progenitor cells (EPC) may contribute to vascular repair in PAH, we suspected that prostacyclin therapy might enhance EPC numbers and functions. In the present study, objectives were to determine whether EPC may contribute to vasodilator treatment efficacy in PAH. We quantified CD34+ cells, CFU-Hill and ECFC (endothelial colony forming cells) in peripheral blood from children with idiopathic PAH (n = 27) or PAH secondary to congenital heart disease (n = 52). CD34+ were enumerated by flow cytometry, CFU-Hill and ECFC by a culture assay. ECFC grown ex vivo were tested for their angiogenic capacities before and after prostacyclin analog therapy (subcutaneous treprostinil). ECFC counts were significantly enhanced in the 8 children treated with treprostinil, while no change was observed in children receiving oral therapy with endothelin antagonists and/or PDE5 inhibitors. CD34+ cell and CFU-Hill counts were unaffected. ECFC from patients treated with treprostinil had a hyperproliferative phenotype and showed enhanced angiogenic potential in a nude mouse preclinical model of limb ischemia. ECFC may partly mediate the clinical benefits of prostanoids in pulmonary arterial hypertension.