title: Effects of hypoxia on megakaryocyte progenitors obtained from the umbilical cord blood of term and preterm neonates.
abstract: BACKGROUND
  Placental insufficiency is associated with early-onset thrombocytopenia in preterm neonates. Prior studies demonstrated a reduction in circulating megakaryocyte (Mk) progenitors, suggesting decreased platelet production. We hypothesized that decreased Mk production is the result of a direct inhibitory effect of hypoxia on the proliferation of Mk progenitors, or a hypoxia-induced change in the fetal hematopoietic environment.
  
  
  OBJECTIVE
  To test the effects of hypoxia on the clonogenic maturation of Mk progenitors obtained from term and preterm cord blood CD34(pos) cells, either cultured alone or in conjunction with CD34(neg) light density mononuclear cells (LDMCs).
  
  
  METHODS
  CD34(pos) cells and CD34(neg) LDMCs were isolated from the cord blood of term and preterm deliveries, and mobilized peripheral blood CD34(pos) cells were obtained from healthy adults. CD34(pos) cells were then cultured alone or co-cultured with CD34(neg) LDMCs in a semisolid, serum-free media containing rTpo, IL-3, and IL-6. Cultures were exposed to 20%, 5%, or 1% oxygen for 10-12 days. Mk colonies were then quantified following immunohistochemical staining.
  
  
  RESULTS
  Pure CD34(pos) cells from preterm (n = 5) and term (n = 5) neonates and from adults (n = 4) generated similar numbers of Mk colonies in all three oxygen concentrations. However, the number of Mk colonies in preterm co-cultures was progressively lower with decreasing O(2) concentrations.
  
  
  CONCLUSIONS
  Hypoxia did not appear to directly inhibit colony formation of Mk progenitors from preterm and term cord blood CD34(pos) cells. However, co-culture studies showed a decrease in Mk colony formation with hypoxia, suggesting an indirect inhibitory effect of hypoxia on Mk clonogenic maturation mediated by non-progenitor cells in the hematopoietic microenvironment.
authors.affiliation: Department of Pediatrics, University of Florida, Gainesville, 32610-0296, USA. Saxonma@peds.ufl.edu
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Saxonhouse
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Rimsza
authors.forename: Gary
authors.initials: G
authors.lastname: Stevens
authors.forename: Nazanin
authors.initials: N
authors.lastname: Jouei
authors.forename: Robert D
authors.initials: RD
authors.lastname: Christensen
authors.forename: Martha C
authors.initials: MC
authors.lastname: Sola
mesh_terms: D018952:Antigens, CD34 / Q000032:analysis; D002455:Cell Division; D015687:Cell Hypoxia; D002478:Cells, Cultured; D018920:Coculture Techniques; D005312:Fetal Blood / Q000166:cytology*; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood*; D008533:Megakaryocytes / Q000502:physiology*; D010100:Oxygen / Q000008:administration & dosage
chemical_list: D018952:Antigens, CD34; D010100:Oxygen