Reduced number and activity of circulating endothelial progenitor cells from patients with hyperhomocysteinemia

BACKGROUND: Hyperhomocysteinemia (HHcy) contributes to atherosclerosis and coronary artery diseases by inducing endothelial cell injury and dysfunction. Recent studies provided increasing evidence that endothelial progenitor cells (EPCs) participated in ongoing endothelial repair. The changes of EPCs in patients with HHcy have not yet been elucidated. Therefore, we investigated the number and functional activity of EPCs in patients with HHcy. METHODS: Human EPCs were isolated and cultured from patients with HHcy (n = 30) and matched volunteers (n = 30). Circulating EPCs were enumerated as AC133+ KDR+ cells via fluorescence-activated cell sorter analysis. Additionally, EPC were expanded from human blood in vitro and identified by DiI-acLDL uptake and lectin staining by direct fluorescent staining under a laser scanning confocal microscope. EPC migration activities were determined by modified Boyden chamber assay. EPC adhesion assay was performed by replating cells on fibronectin-coated dishes and then counting adherent cells. RESULTS: A significant decrease was observed in circulating EPC (AC133+ KDR+ cells) numbers in patients with HHcy compared with control subjects (63.9 +/- 11.7 cells/mL vs. 91.5 +/- 14.2 cells/mL blood, p <0.01). In addition, the numbers of EPCs also decreased in patients with HHcy after ex vivo cultivation (36.1 +/- 6.5 vs. 51.5 +/- 8.3 EPCs/x200 field, p <0.01). Both circulating EPCs and differentiated EPCs were inversely correlated with total homocysteine levels. In addition, EPCs from patients with HHcy were significantly impaired in their migratory capacity and ability to adhere to fibronectin compared with controls. CONCLUSIONS: The present study demonstrated that EPC numbers and functional capacity were impaired in patients with HHcy.