Abstract
Background aims. The distinction between hematopoietic stem cells (HSC) and endothelial progenitor cells (EPC) is poorly defined. Co-expression of CD34 antigen with vascular endothelial growth factor (VEGF) receptor (VEGFR2) is currently used to define EPC (Citation). Methods. We evaluated the phenotypic and genomic characteristics of peripheral blood-derived CD34+ cells in 22 granulocyte–colony-stimulating factor (G-CSF)-mobilized patients with severe coronary artery disease and assessed the influence of cell selection and storage on CD34+ cell characteristics. Results. The median CD34+ cell contents in the products before and after enrichment with the Isolex 300i Magnetic Cell Selection System were 0.2% and 82.5%, respectively. Cell-cycle analysis showed that 80% of CD34+ cells were in G0 stage; 70% of the isolated CD34+ cells co-expressed CD133, a marker for more immature progenitors. However, less than 5% of the isolated CD34+ cells co-expressed the notch receptor Jagged-1 (CD339) and only 2% of the isolated CD34+ population were positive for VEGFR2 (CD309). Molecular assessment of the isolated CD34+ cells demonstrated extremely low expression of VEGFR2 and endothelial nitric oxide synthase (eNOS) and high expression of VEGF-A. Overnight storage at 4°C did not significantly affect CD34+ cell counts and viability. Storage in liquid nitrogen for 7 weeks did not affect the percentage of CD34+ cells but was associated with a 26% drop in cell viability. Conclusions. We have demonstrated that the majority of isolated CD34+ cells consist of immature and quiescent cells that lack prototypic markers of EPC. High VEGF-A gene expression might be one of the mechanisms for CD34+ cell-induced angiogenesis.
Acknowledgments
Supported by NIH grants CA102824 and a grant from Baxter Healthcare Inc.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.