title: Factors modulating circulation of hematopoietic progenitor cells in cord blood and neonates.
abstract: BACKGROUND
  Hematopoietic progenitor cells (HPC) circulate at high levels at birth and disappear rapidly afterwards, but the underlying mechanism it is not known. The aim of this study was to assess circulating HPC in cord blood at different gestational ages and shortly after birth and concomitantly study the biologic markers involved in this phenomenon.
  
  
  METHODS
  All samples were analyzed for CD34(+) cells, colony-forming units (CFU) and cytokines.
  
  
  RESULTS
  The results obtained confirmed a slight decrease in HPC concentration during the late stage of fetal life (R(2)=0.41). After birth, CD34(+) cells showed a rapid decline from circulation: 25+/-29% at 3 h, 51+/-42% at 12 h and 80+/-48% at 60 h. CFU cleared following a similar pattern. Cord plasma showed higher concentrations of stem cell factor (SCF), fetal liver tyrosine kinase 3-ligand (FLT3l), erythrpoietin (EPO), granulocyte colony-stimulating factor (G-CSF) and interleukin-11 (IL-11) compared with an adult control. Interestingly, the EPO concentration in newborn plasma correlated with the kinetics of HPC decline after birth. Moreover, we observed an up-regulation of l-selectin and a down-regulation of CXCR4 expression in CD34(+) cells 3 h after birth.
  
  
  CONCLUSIONS
  These data combined suggest that an active homing process results in the clearance of HPC from the circulation immediately after birth.
authors.affiliation: Gynecology and Obstetrics Service, Hospital Universitari Sant Joan de Deu, Esplugues de Llobregat, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Gonzalez
authors.forename: L
authors.initials: L
authors.lastname: Amat
authors.forename: C
authors.initials: C
authors.lastname: Azqueta
authors.forename: J A
authors.initials: JA
authors.lastname: Madrigal
authors.forename: J M
authors.initials: JM
authors.lastname: Laïlla
authors.forename: J
authors.initials: J
authors.lastname: Garcia
authors.forename: S
authors.initials: S
authors.lastname: Querol
mesh_terms: D000328:Adult; D018952:Antigens, CD34 / Q000378:metabolism; D001775:Blood Circulation; D002452:Cell Count; D004921:Erythropoietin / Q000097:blood; D005260:Female; D005312:Fetal Blood / Q000166:cytology* / Q000502:physiology*; D005865:Gestational Age; D016179:Granulocyte Colony-Stimulating Factor / Q000097:blood; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D007231:Infant, Newborn; D017370:Interleukin-11 / Q000097:blood; D019041:L-Selectin / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000097:blood; D019718:Receptors, CXCR4 / Q000378:metabolism; D019089:Stem Cell Factor / Q000097:blood
chemical_list: D018952:Antigens, CD34; C527276:CXCR4 protein, human; C508611:IL11 protein, human; D017370:Interleukin-11; D008565:Membrane Proteins; D019718:Receptors, CXCR4; D019089:Stem Cell Factor; C084881:flt3 ligand protein; D004921:Erythropoietin; D019041:L-Selectin; D016179:Granulocyte Colony-Stimulating Factor