Stem cell factor stimulates the in vitro growth of bone marrow cells from aplastic anemia patients

Aplastic anemia (AA) is a rare human bone marrow disorder of unknown etiology manifested by a strongly impaired growth of hematopoietic precursors. In this study, we examined the ability of recombinant human stem cell factor (SCF) to stimulate proliferation in vitro of bone marrow cells from 15 AA patients. All patients had been previously treated with antilymphocyte globulin (ALG). SCF, in combination with erythropoietin (Epo), interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and granulocyte colony-stimulating factor (G-CSF), increased the number of hematopoietic colonies formed in a semisolid medium by AA marrows. Maximal colony numbers reached 30% of the numbers observed with normal bone marrow cells. Proliferation of AA cells cultured in a liquid medium containing SCF together with Epo, IL-3, GM-CSF, and G-CSF approached 70% of the control level, as measured by 3H-thymidine incorporation. The effect of the combination of SCF with the other growth factors was more than 10 times stronger than that of the growth factors alone. The most marked effect of SCF was on the generation of erythroid colonies by precursor cells. The results demonstrate synergism between CSF and other hematopoietic growth factors, resulting in the most efficient stimulation of the in vitro growth of AA bone marrow cells described to date. Use of SCF, either alone or in combination with other factors, may be of potential value in treatment of AA.