Polycythemia vera: hormonal modulation of erythropoiesis in vitro.

We performed in vitro culture studies examining the interaction of erythropoietin with red cell progenitors in polycythemia vera. Bone marrow was obtained from five patients with typical disease and from five healthy volunteers, and assayed for erythroid colony formation (CFU-E) by the methylcellulose technique. In cultures without added erythropoietin, a mean eightfold greater cloning efficiency was noted with the polycythemia vera marrows, as compared to normal. There was prominent stimulation of colony formation by erythropoietin, and the shape of the erythropoietin dose-response cruves appeared to be similar in both patients and controls. Anti-erythropoietin antibody reduced the number of CFU-E in cultures not containing added erythropoietin, but did not eliminate them. Dexamethasone (10(-9) M) caused a consistent increase in CFU-E in the patients' cultures. These studies provide evidence for functional erythropoietin and glucocorticosteroid receptor mechanisms on erythroid precursors in polycythemia vera. The observations are consistent with a concept of this disease as a disorder of hematopoietic stem cells in which peripheral erythrocytosis is caused by an expanded erythroid progenitor compartment which maintains responsiveness to hormonal modulation.