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.

Hypercholesterolaemia contributes to atherosclerosis and coronary artery diseases by inducing endothelial cell injury and dysfunction. Recent studies have provided increasing evidence that EPCs (endothelial progenitor cells) participate in ongoing endothelial repair and postnatal neovascularization. However, the changes in EPCs in patients with hypercholesterolaemia have not been elucidated to date. Therefore we investigated the number and functional activity of EPCs in patients with hypercholesterolemia. Total MNCs (mononuclear cells) were isolated from 20 patients with hypercholesterolaemia and 20 matched control subjects. EPCs were characterized as adherent cells double-positive for DiI-LDL (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanide percholate-labelled low-density lipoprotein) uptake and lectin binding by direct fluorescent staining under a laser scanning confocal microscope, and were characterized further by demonstrating the expression of KDR (kinase insert domain-containing receptor), CD34 and AC133 by flow cytometry. Proliferation, migration and in vitro vasculogenesis activity of EPCs were assayed using the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] assay, modified Boyden chamber assay and an in vitro vasculogenesis kit respectively. EPC adhesion assay was performed by replating cells on fibronectin-coated dishes and then counting the adherent cells. As a result, the number of EPCs was significantly reduced in patients with hypercholes-terolaemia compared with that in control subjects (41.8 +/- 8.7 compared with 64.5 +/- 16.6 EPCs/x 200 field respectively; P < 0.05). The number of EPCs was inversely correlated with total cholesterol (r = -0.659, P < 0.001) and LDL-cholesterol (r = -0.611, P < 0.001) levels. In addition, the functional activities of isolated EPCs, such as proliferative, migratory, adhesive and in vitro vasculogenesis capacity, were also impaired. In conclusion, the results of the present study may state a novel pathophysiological mechanism of hypercholesterolaemia: the reduction of EPCs with decreased functional activity.

A growing body of evidence in animal models and clinical studies supports the concept that endothelial progenitor cell (EPC)-mediated therapy ameliorates pulmonary arterial hypertension (PAH) and thus may represent a novel approach to treat it. Conversely, several experimental findings suggest that EPCs may be involved in PAH pathogenesis and disease progression. These discrepant results confuse the application of EPC transplantation as an effective treatment strategy for PAH. To improve the study of EPC transplantation in PAH therapy, it is high time that we resolve this dilemma. In this review, we examine the pathobiological changes of PAH, the characteristics of EPCs, and the underlying mechanisms of EPC effects on PAH.

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