Effects of hypoxia on megakaryocyte progenitors obtained from the umbilical cord blood of term and preterm neonates.
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.
Saxonhouse
Matthew A
MA
Department of Pediatrics, University of Florida, Gainesville, 32610-0296, USA. Saxonma@peds.ufl.edu
Rimsza
Lisa M
LM
Stevens
Gary
G
Jouei
Nazanin
N
Christensen
Robert D
RD
Sola
Martha C
MC
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
D018952:Antigens, CD34; D010100:Oxygen