CD34 + cells in maternal placental blood are mainly fetal in origin and express endothelial markers

Abstract

Fetal CD34 cells enter the maternal circulation during pregnancy and may persist for decades. These cells are usually depicted as hematopoietic stem/progenitor cells. Our objective was to further determine the phenotype of fetal chimeric CD34 cells in placental maternal blood from the intervillous space (IVS). Human healthy term placentas were analyzed (n=9). All fetuses were male. CD34 cells were identified in the IVS and further characterized as fetal or maternal using X and Y chromosome fluorescence in situ hybridization. The phenotype of fetal cells was further analyzed using anti-CD117 (c-kit), anti-CD133, anti-CD31, anti-von Willebrand factor (vWF), anti-vimentin, anti-CD45 and anti-cytokeratin (CK) antibodies. We used preeclamptic placentas of male (n=3) and healthy placentas of female fetuses (n=3) as controls. As expected fetal cells were easily identified in the IVS and significantly increased in cases of preeclampsia. Most CD34 cells in the IVS were of fetal origin (90%) and were not surrounded by CK staining further showing that they were not in fetal trophoblastic villi. Similarly, about 40% of CD31 and 6% of vimentin cells in the IVS were fetal in origin. No CD117 or CD133 fetal cells were found in the IVS of examined placentas. Besides, all the CD34 cells identified in the IVS were co-labeled with vWF or CD31, suggesting their endothelial origin. These results suggest that most CD34 cells in maternal placental blood at term are fetal in origin from endothelial and not hematopoietic lineages. © 2009 USCAP, Inc All rights reserved.