Dexamethasone phosphate (DP) is a synthetic corticosteroid widely used in neonatal intensive care units for the prevention and treatment of chronic lung disease. Previous studies have shown that pharmacologic doses of dexamethasone exert a profound suppressive effect on the inflammatory and immune repsonses. Binding studies with glucocorticoids suggest that erythroid progenitors might have glucocorticoid receptors, but the effect of DP on clonogenic maturation of hematopoietic progenitors of preterm infants is not known. Therefore, we obtained circulating CD34+ progenitor cells from umbilical cord blood of four preterm infants (GA=25-30wks) and cultured them in the presence of various concentrations of DP and Erythropoietin (Epo) and appropriate controls. The numbers of Erythroid Colony-Forming Unit (CFU-E) and Burst-Forming Unit(BFU-E) and granulocyte macrophage (GM) colonies detected at each DP concentration were expressed as a percentage of the number detected without DP. (Values are mean ± SD, *p<0.05) Table DP also reduced erythroid colony size, in a dose-dependent fashion. No such reductions were evident using progenitors of healthy adults.Conclusions: DP, at pharmacologic concentrations, markedly decreases both erythroid and GM colony formation from progenitor cells obtained from preterm infants. Further study is required to determine the in vivo effect of DP treatment on hematopoiesis in preterm infants.

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