Erythropoietin-stimulated erythropoiesis in long-term bone marrow culture.

The proliferation of multipotential haematopoietic stem cells (CFU-S) is possible in some long-term bone marrow cultures. Granulocyte and macrophage progenitor (CFU-C) and megakaryocyte precursor cells (CFU-M) are present in these cultures and undergo full development into mature cells. In contrast, while immature erythroid progenitors ('early' BFU-E) are maintained in long-term culture, none of the more differentiated progeny (CFU-E) have been detected, and no morphologically recognisable erythroid cells have been observed. We now describe a modified culture system in which the 'early' BFU-E develop into 'late' BFU-E in response to added erythropoietin. Further maturation of these cells into CFU-E and non-nucleated erythrocytes can be achieved by mechanical agitation of the long-term cultures or by transferring the cells into dishes which do not allow cell attachment to occur.