In vitro response of myelodysplastic megakaryocytopoiesis to megakaryocyte growth and development factor (MGDF)

To evaluate a potential therapeutic role for megakaryocyte growth and development factor (MGDF) in myelodysplastic syndromes (MDS) we compared the in vitro response of normal and myelodysplastic megakaryopoiesis to MGDF on bone marrow mononuclear cells from nine MDS patients and four healthy donors in a short term liquid culture system. The cells were incubated with MGDF alone (1 ng/ml, 10 ng/ml and 100 ng/ml) and in combination with 20 ng/ml stem cell factor, 2 U/ml erythropoietin (EPO) and 100 ng/ml interleukin-3 (IL-3). Cytospins were prepared after 4 days and 10 days for CD61 APAAP staining. In addition, the ploidy of propidium iodide stained CD61 positive cells were detected by flow cytometry. The CD61+ cell number significantly increased (13-fold after 4 days, 56-fold after 10 days of culture) when MGDF (100 ng/ml) was added to the normal bone marrow (NBM) cultures (P=0.0003; P=0.0001). In the MDS cultures the absolute number of endomitotic cells as well as the percentage of polyploid cells remained significantly lower than in NBM after 10 days (P=0.0001). The effect of MGDF on polyploidization of MDS cells was significantly dose dependent (P=0.0051). We found no correlation between peripheral platelet count, cellularity of the bone marrow, number of bone marrow megakaryocytes or FAB-subtype and response to MGDF. Additional administration of IL-3 resulted in a left-shift of megakaryopoiesis in both groups. Even though the response of myelodysplastic megakaryocytic progenitors to MGDF shows inter-individual variations, it is significantly impaired overall. Our data suggest that higher doses of MGDF may be able to ameliorate thrombocytopenia in a subgroup of MDS patients.