Comparative Analysis of Methods for Assessment of Circulating Endothelial Progenitor Cells Indicated Heterogeneity of Subpopulations at Various Stages of Differentiation

Abstract number: OR139

Deutsch¹ V, Shmilovich^2,3 H, Abashidze^2,3 A, Miller^2,3 H, Keren^2,3 G, Katz¹ B, George^2,3 J

^{2,3 11}The Hematology Institute, Tel Aviv Medical Center, Solid squareSolid square, Solid squareSolid square ^2,32The Department of Cardiology, Tel Aviv Medical Center, Solid squareSolid square, Solid squareSolid square

The cells of the vasculature are derived from pluripotent hemangioblasts, which also give rise to blood. Angiogenesis, the formation of new blood vessels results from the proliferation and migration of mature endothelial cells from existing blood vessels or from the recently described, but not yet well characterized endothelial progenitor cells (EPCs). The number and properties of EPC in disease states is of considerable interest due to the promising therapeutic potential of these cells. EPCs have been shown to be mobilized from the bone marrow and contribute to angiogenesis following vascular injury, organ ischaemia and tumor progression. However, mechanisms that drive the EPC response to injury remain elusive and the lack of definitions of EPC subpopulations and the many methods used by different groups to identify these cells make correlation of results difficult. To better understand the potential of these cells, we performed a comparative analysis of several methods used for assessing circulating EPC in 40 healthy individuals and correlated them with humoral factors known to influence their numbers. Peripheral blood mononuclear cells were obtained and evaluated by flow cytometry for CD34, CD45, CD133 and KDR, and colony forming unit (CFU) numbers and adhesive properties were assessed. Levels of circulating vascular endothelial growth factor (VEGF), erythropoietin and C-reactive protein were determined and correlated with each of the EPC markers. CD34/KDR numbers correlated with CD34/CD133/KDR but not with CD34/CD133 (which includes hematopoietic progenitors). CFU numbers negatively correlated with CD34/CD133, perhaps due to hematopoietic cells. The VEGFR2 positive cells (CD34/KDR and CD34/CD133/KDR) correlated with VEGF serum levels. The number of EPC adhering to fibronectin and endothelial-cells correlated with CFU numbers but not with EPC membrane markers. Our results indicate for the first time that EPC, like hematopoietic precursors may be a heterogeneous cell population comprised of progenitors at various stages of differentiation, having varied proliferative capacity. These data also suggest that co-expression of CD34, CD133 and KDR-VEGFR2 is appropriate for defining a population of circulating EPC whereas CFU are more likely to reflect the proliferative capacity of the progenitors.