The in vitro effect of pegylated recombinant human megakaryocyte growth and development factor (PEGrHuMGDF) on megakaryopoiesis in patients with aplastic anaemia

development factor (rHuMGDF), a truncated form of the Mpl ligand, stimulate s megakaryopoiesis both in vitro and in vivo. We describe the in vitro effe ct of pegylated recombinant human MGDF (PEGrHuMGDF) alone and in combinatio n with other haemopoietic growth factors (G-CSF GM-CSF IL3, IL6, erythropoi etin, SCF) on megakaryopoiesis in bone marrow from 11 normal subjects and 1 9 patients with aplastic anaemia (AA), We used semi-solid cultures to asses s megakaryocyte colony growth (CFU-Mk) and 7d suspension cultures to assess production of platelet glycoprotein IIIa (CD61) positive cells, CFU-Mk gro wth from normal marrow increased 3-4-fold and CD6+ve cells in suspension cu lture increased 8-10-fold with the addition of 10 ng/ml PEGrHuMGDF In norma l subjects growth factor combinations further increased responses in suspen sion culture, PEGrHuMGDF + SCP, PEGrHuMGDF + IL3 and PEGrKuMGDF + SCF + IL3 + Epo (P < 0.05). IL6, GM-CSF, G-CSF or Epo added with PEGrHuMGDF did not consistently give this increase. CFU-Mk growth from AA marrow remained very low in the presence of PEGrHuMGDF with or without the addition of other gr owth factors. CD61+ve cells in suspension culture were, however, increased in the presence of PEGrHuMGDF alone in 12/19 AA cases. Of the 12 patients r esponsive to PEGrHuMGDF, nine were tested with additional growth factors an d further responses were seen in six, rn the AA cases PEGrHuMGDF+SCF and PE GrHuMGDF+SCF+IL3+Epo gave the highest responses. These data suggest that PE GrHuMGDF, alone or in combination with SCF and/or IL3, can enhance megakary ocyte proliferation in some patients with aplastic anaemia and may therefor e have a role in the treatment of thrombocytopenia in these cases.