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Background: Endothelial dysfunction is the pathophysiological characteristic of pulmonary arterial hypertension (PAH). Some paracrine factors secreted by bone marrow-derived endothelial progenitor cells (BMEPCs) have the potential to strengthen endothelial integrity and function. This study investigated whether BMEPCs have the therapeutic potential to improve monocrotaline (MCT)-induced PAH via producing vasoprotective substances in a paracrine fashion., Methods and Results: Bone marrow-derived mononuclear cells were cultured for 7 days to yield BMEPCs. 24 hours or 3 weeks after exposure to BMEPCs in vitro or in vivo, the vascular reactivity, cyclooxygenase-2 (COX-2) expression, prostacyclin (PGI2) and cAMP release in isolated pulmonary arteries were examined respectively. Treatment with BMEPCs could improve the relaxation of pulmonary arteries in MCT-induced PAH and BMEPCs were grafted into the pulmonary bed. The COX-2/prostacyclin synthase (PGIS) and its progenies PGI2/cAMP were found to be significantly increased in BMEPCs treated pulmonary arteries, and this action was reversed by a selective COX-2 inhibitor, NS398. Moreover, the same effect was also observed in conditioned medium obtained from BMEPCs culture., Conclusions: Implantation of BMEPCs effectively ameliorates MCT-induced PAH. Factors secreted in a paracrine fashion from BMEPCs promote vasoprotection by increasing the release of PGI2 and level of cAMP.

Previous studies have underlined the importance of endothelial dysfunction and microvascular occlusion in the pathogenesis of pulmonary artery hypertension (PAH). Since the endothelial progenitor cells (EPCs) are involved in maintaining endothelial homeostasis, we observed the change of peripheral EPCs in canines before and after PAH onset. PAH was induced by intra-pulmonary artery injection of dehydromonocrotaline (DHMC) in nine beagles. Before and 48 h and 6 weeks after DHMC injection, 40 ml peripheral blood was obtained from the femoral vein. Circulating EPCs were identified as CD133 + KDR + cells and numerated by fluorescence-activated cell sorter; the EPCs functional capacity was determined by in vitro tubule-forming assay. The senescence of EPCs was determined by beta-galactosidase staining. At each time point, 2 ml blood from femoral artery was obtained for arterial oxygen pressure (PaO(2)). Forty-eight hours after DHMC injection, treated beagles suffered from hypoxemia; however, both the number and the tubule-forming capacity of EPCs were transiently raised. Six weeks later, PAH was confirmed by obviously high mean pulmonary arterial pressure (20.2 +/- 1.64 vs. 11.3 +/- 2.0 mmHg, p < 0.05) and low PaO(2) (69.30 +/- 9.15 vs. 95.94 +/- 1.43 mmHg, p < 0.01) in beagles after DHMC treatment, and their EPCs exhibited a predominant decrease in either the number (206.1 +/- 26.8 vs. 632.8 +/- 42.8 cells/ml blood, p < 0.01) or the tubule-forming capacity (21.1 +/- 2.8 vs. 11.2 +/- 2.8 tubules/x200 field, p < 0.01). Additionally, senescence-associated beta-galactosidase-positive EPCs were significantly increased. Our data suggested that, after the acute stage of DHMC injury to pulmonary vessels, the EPCs from PAH beagles suffered from exhaustion and senescence.

Experimental data suggest that transplantation of EPCs attenuates monocrotaline-induced pulmonary hypertension in rats and dogs. In addition, our previous studies suggested that autologous EPC transplantation was feasible, safe, and might have beneficial effects on exercise capacity and pulmonary hemodynamics in adults with IPAH. Thus, we hypothesized that transplantation of EPCs would improve exercise capacity and pulmonary hemodynamics in children with IPAH. Thirteen children with IPAH received intravenous infusion of autologous EPCs. The right-sided heart catheterization and 6-MWD test were performed at baseline and at the time of 12 wk after cell infusion. At the time of 12 wk, mPAP decreased by 6.4 mmHg from 70.3 +/- 19.0 to 63.9 +/- 19.3 mmHg (p = 0.015). PVR decreased by approximately 19% from 1118 +/- 537 to 906 +/- 377 dyn s/cm(5) (p = 0.047). CO increased from 3.39 +/- 0.79 to 3.85 +/- 0.42 L/min (p = 0.048). The 6-MWD increased by 39 m from 359 +/- 82 to 399 +/- 74 m (p = 0.012). NYHA functional class also improved. There were no severe adverse events with cell infusion. The small pilot study suggested that intravenous infusion of autologous EPCs was feasible, safe, and associated with significant improvements in exercise capacity, NYHA functional class, and pulmonary hemodynamics in children with IPAH. Confirmation of these results in a randomized controlled trial are essential.

Objectives: The goal of this study was to investigate the feasibility, safety, and initial clinical outcome of intravenous infusion of autologous endothelial progenitor cells (EPCs) in patients with idiopathic pulmonary arterial hypertension (IPAH)., Background: Experimental data suggest that transplantation of EPCs attenuates monocrotaline-induced pulmonary hypertension in rats and dogs. In addition, clinical studies suggest that autologous progenitor cell transplantation is feasible and safe in patients with ischemic diseases., Methods: We conducted a prospective, randomized trial comparing the effects of EPC transplantation plus conventional therapy with those of conventional therapy alone in patients with IPAH. The primary end point was change in the 6-min walk distance using a standardized protocol. The secondary end points were changes in hemodynamic variables as assessed by right heart catheterization., Results: After 12 weeks of follow-up, the mean distance walked in 6 min increased by 48.2 m in the cell infusion group (from 263 +/- 42 m to 312 +/- 34 m), and an increase of 5.7 m occurred in the conventional therapy group (from 264 +/- 42 m to 270 +/- 44 m). The mean difference between the 2 groups was 42.5 m (95% confidence interval 28.7 to 56.3 m, p < 0.001). The patients in the cell infusion group also had significant improvement in mean pulmonary artery pressure, pulmonary vascular resistance, and cardiac output. There were no severe adverse events with cell infusion., Conclusions: This preliminary study showed that intravenous infusion of autologous EPCs seemed to be feasible and safe, and might have beneficial effects on exercise capacity and pulmonary hemodynamics in patients with IPAH. (Safety and Efficacy Study of Transplantation of EPCs to Treat Idiopathic Pulmonary Arterial Hypertension; http://www.clinicaltrials.gov/ct/show/NCT00257413?order=1; NCT00257413).