Effect of a stromal cell derived hematopoietic factor on human bone marrow progenitor cells

Conditioned media (KM-102CM and KM-103CM) obtained from two different human bone marrow stromal cell lines (KM-102 and KM-103) were analysed for their ability to stimulate human hematopoietic stem cells. Both KM-102CM and KM-103CM stimulate the formation of granulocyte-monocyte colony forming unit (CFU-C) and erythroid burst forming unit (BFU-E) colonies in the presence of erythropoietin, and also maintain the long term proliferation of stem cells in vitro. When KM-102CM and KM-103CM were fractionated by DEAE-cellulose chromatography and treated with antiserum against granulocyte-monocyte colony stimulating factor (GM-CSF) these colony stimulating activity (CSA) and burst promoting activity (BPA) contained in these media were neutralized by the antiserum and thus proved to be basically identical to GM-CSF. These results showed that the GM-CSF produced by the marrow stromal cells can maintain and proliferate the hematopoietic progenitor cells in the long term and thus gave us an evidence of one of the regulatory functions of the marrow stromal cells in hematopoiesis.