STEM-CELL FACTOR IMPROVEMENT OF PROLIFERATION AND MAINTENANCE OF HEMATOPOIETIC PROGENITORS IN MYELODYSPLASTIC SYNDROMES

Human recombinant stem cell factor (rSCF) was tested for its capabilit y of improving the defective growth of hemopoietic progenitors in 28 c ases of myelodysplastic syndromes (MDS). In vitro growth and response to rSCF were quite variable. However, in most cases, rSCF stimulated C FU-GM growth induced by rG-CSF, rGM-CSF, rlL-3, 5637 conditioned mediu m (50-1400% enhancement). rSCF effect was slightly more evident on day 14 CFU-GM and in the presence of rlL-3. BFU-E growth induced by rEPO or rlL-3+rEPO was enhanced by rSCF in about 50% of cases, in linear co rrelation with the levels of patients' hemoglobin. rSCF did not increa se CFU-E growth, whereas it slightly stimulated CFU-MI( in 33% of the cases. EPO, SCF and, particularly, their combination, enhanced the rec overy of normal CFU-E and BFU-E after 7 days of liquid culture. This w as less evident in cultures of MDS patients. Conversely, CFU-GM genera tion in long term liquid cultures, although highly variable, was stimu lated by rSCF and, above all, by rSCF + rG - CSF, similarly to what wa s observed with normal bone marrow samples. SCF seems to enhance in vi tro erythropoiesis only in MDS cases presenting without severe anemia. It has little effect on megakaryocytopoiesis, while it seems to be mo re active on CFU-GM growth and maintenance.