Maternal circulating CD34+VEGFR-2+ and CD133+VEGFR-2+ progenitor cells increase during normal pregnancy but are reduced in women with preeclampsia

Abstract

Circulating endothelial progenitor cells (EPCs) may contribute to vascular endothelial cell homeostasis, and low levels of these cells are predictive of cardiovascular disease. We hypothesized that circulating EPCs increase in number during uncomplicated pregnancy but are reduced in women with preeclampsia. Peripheral blood was obtained from pregnant women and from nulligravidas in cross-sectional design. Cells expressing CD34 or CD133, in combination with vascular endothelial growth factor receptor-2 (VEGFR-2), were enumerated by flow cytometry. Both CD34(+)VEGFR-2(+) (doubly positive) and CD133(+)VEGFR-2( +) cells were significantly increased during the second and third trimesters of uncomplicated pregnancy compared to the first trimester. First trimester and nulligravida groups did not differ. Endothelial progenitor cells, quantified by flow cytometry or by circulating angiogenic cell (CAC) culture assay, were significantly reduced in women with preeclampsia compared to third trimester controls. Circulating EPCs appear to increase during normal pregnancy, and comparatively reduced numbers of these cells exist during preeclampsia.

Figure 1

CD34⁺VEGFR-2⁺ cells (left panel) and CD133⁺VEGFR-2⁺ cells (right panel) detected in peripheral blood by flow cytometry. Whole blood was stained with antihuman monoclonal antibodies and processed as described in the text. Gates were drawn on the lymphocyte population based on side-scatter and CD45 characteristics. Within these gates, CD34⁺ and CD133⁺ elements expressing VEGFR-2 (KDR) were analyzed. Percentage positive cells were defined by setting lower limits on the basis of negative isotype controls. CD34⁺VEGFR-2⁺ and CD133⁺VEGFR-2⁺ cells are located in the upper right quadrants. VEGFR-2 indicates vascular endothelial growth factor receptor-2; KDR = kinase insert domain receptor.

Figure 2

Scatterplot showing the quantity (number) of CD34/VEGFR-2-doubly positive endothelial progenitor cells (EPCs) in maternal peripheral blood during normal pregnancy and preeclampsia. Endothelial progenitor cells increased significantly over time during normal pregnancy, with highest levels during the third trimester. Endothelial progenitor cells were significantly lower on average during preeclampsia compared to third trimester controls. Triangles indicate women who were in labor at the time of blood sampling. VEGFR-2 indicates vascular endothelial growth factor receptor-2.

Figure 3

Scatterplot showing the quantity (number) of CD133/VEGFR-2-doubly positive endothelial progenitor cells (EPCs) in maternal peripheral blood during normal pregnancy and preeclampsia. Endothelial progenitor cells increased significantly over time during normal pregnancy, with highest levels during the third trimester. Endothelial progenitor cells were significantly lower on average during preeclampsia compared to third trimester controls. Triangles indicate women who were in labor at the time of blood sampling. VEGFR-2 indicates vascular endothelial growth factor receptor-2.

Figure 4

Scatterplot showing the quantity (number) of adherent, Ulex lectin, 1,1′-dioctadecyl-3,3,3,3′ β-tetramethylindo-carbocyanine perchlorate (DiI)-labeled acetylated low-density lipo-protein (DiI-Ac-LDL), and dihydrochloride (DAPI)-triply positive cells in culture (circulating angiogenic cells, CACs) during the third trimester. Each symbol corresponds to the average of at least 2 randomly selected, high-power fluorescence microscopic fields from each of 2 culture wells per patient. The thick horizontal bars denote the median value for each group.