Circulating mononuclear cells may play an important role for the vascular remodelling in pulmonary arterial hypertension (PAH), but studies addressing multiple progenitor populations are rare and inconsistent.We used a comprehensive fluorescence-activated cell sorting analysis of circulating mononuclear cells in 20 PAH patients and 20 age- and sex-matched controls, and additionally analysed CD133(+) cells in the lung tissue of five PAH transplant recipients and five healthy controls (donor lungs).PAH patients were characterised by increased numbers of circulating CD133(+) cells and lymphopenia as compared with control. In PAH, CD133(+) subpopulations positive for CD117 or CD45 were significantly increased, whereas CD133(+)CD309(+), CD133(+)CXCR2(+) and CD133(+)CD31(+) cells were decreased. In CD133(+) cells, SOX2, Nanog, Ki67 and CXCR4 were not detected, but Oct3/4 mRNA was present in both PAH and controls. In the lung tissue, CD133(+) cells included three main populations: type 2 pneumocytes, monocytes and undifferentiated cells without significant differences between PAH and controls.In conclusion, circulating CD133(+) progenitor cells are elevated in PAH and consist of phenotypically different subpopulations that may be up- or downregulated. This may explain the inconsistent results in the literature. CD133(+) type 2 pneumocytes in the lung tissue are not associated with circulating CD133(+) mononuclear cells.
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