Effects of anoxia on megakaryocyte progenitors derived from cord blood CD34pos cells.
BACKGROUND
Severe hypoxic insults to the fetus and neonate are associated with the development of thrombocytopenia. The thrombocytopenia in some cases is the result of disseminated intravascular coagulation, but that mechanism fails to account for all, perhaps the majority, of cases.


OBJECTIVE
We hypothesized that human fetal megakaryocyte (Mk) progenitors are directly adversely affected by transient anoxia.


METHODS
To test this, we isolated CD34pos cells from the umbilical cord blood of 10 healthy term neonates, and exposed these to 0% or 20% O2 for 24 h, with or without recombinant thrombopoietin (rTpo, 50 ng/mL). After 24 h, a portion of the CD34pos cells were harvested for flow cytometric evaluation of apoptosis. The remaining cells were cultured for an additional 10-12 days, under normoxic conditions, in a collagen-based serum-free system containing rTpo, IL-3, and IL-6. In this way, we sought to determine the effect of transient anoxia on clonogenic capacity of Mk progenitors.


RESULTS
Contrary to our hypothesis, anoxia did not increase either apoptosis or cell death of the CD34pos cells. The addition of rTpo was protective, with a significant decrease in apoptosis and cell death (P < 0.0001), and an increase in the number of Mk colonies cultured (P = 0.04). There was no difference between the normoxic and anoxic groups in proliferative potential of the Mk progenitor cells.


CONCLUSIONS
The thrombocytopenia observed in neonates following an acute hypoxic event is not likely due to a direct deleterious effect of hypoxia on Mk progenitors.
Saxonhouse
Matthew A
MA
Department of Pediatrics, University of Florida, Gainesville, FL, USA. saxonma@peds.ufl.edu
Rimsza
Lisa M
LM
Christensen
Robert D
RD
Hutson
Alan D
AD
Stegner
Joseph
J
Koenig
Joyce M
JM
Sola
Martha C
MC
D018952:Antigens, CD34 / Q000032:analysis; D017209:Apoptosis / Q000187:drug effects; D015687:Cell Hypoxia; D002478:Cells, Cultured / Q000187:drug effects; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D005312:Fetal Blood / Q000166:cytology*; D005311:Fetal Hypoxia / Q000150:complications / Q000503:physiopathology; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D066298:In Vitro Techniques; D007231:Infant, Newborn; D007377:Interleukin-3 / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D008533:Megakaryocytes / Q000187:drug effects*; D010100:Oxygen / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D013921:Thrombocytopenia / Q000209:etiology / Q000503:physiopathology; D013926:Thrombopoietin / Q000494:pharmacology
D018952:Antigens, CD34; D016895:Culture Media, Serum-Free; D007377:Interleukin-3; D015850:Interleukin-6; D011994:Recombinant Proteins; D013926:Thrombopoietin; D010100:Oxygen