Hydroxyurea promotes the reduction of spontaneous BFU-e to normal levels in SS and S/beta thalassemic patients

We have studied the effects of hydroxyurea on growth and differentiation of early erythroid progenitor cells (BFU-e) from peripheral blood of sickle c ell disease patients (five SS and two Hb S/beta -thalassemia) in the presen ce or absence of exogenous stimulating factors. When the mononuclear cells from the sickle cell disease patients were cultured at diagnosis (before hy droxyurea treatment), there was an increased number of BFU-e in relation to controls (p < 0.05, Wilcoxon test) when cells were grown in the presence o r absence of 5637 conditioned medium and erythropoietin. Colonies that deve loped in the absence of added growth factors were considered "spontaneous". A significant difference was observed after hydroxyurea treatment in the n umber of BFU-e obtained in the presence and absence of stimulus, with a hig her reduction in the spontaneous BFU-e number. As expected, there was an in creased Hb F level in these patients when compared with their pretreatment levels. There was no correlation between spontaneous BFU-e and hemoglobin l evels in all patients studied.