In vivo administration of stem cell factor enhances both proliferation and maturation of murine megakaryocytes

Division of Hematology, University of Florence, Italy.

BACKGROUND. Stem cell factor (SCF) has already been shown to participate in the regulation of erythro- and granulopoiesis. The aim of this study was to define the possible role of SCF in the regulation of megakaryocytopoiesis. METHODS. Stem cell factor activity has been assessed in an in vivo murine model, in which different doses of the factor were either given alone or in association with recombinant human erythropoietin (rhEpo). Mice were sacrificed after a six-day treatment to evaluate the effect of SCF on the number of bone marrow and spleen colony-forming units-megakaryocyte (CFU-Mk), and after a two-day treatment for evaluation of thrombopoietin-like activity. RESULTS. We found that SCF induces a dose-related increase in the number of CFU-Mk in both the bone marrow and spleen of the treated mice, and that in the range of the doses used (from 25 to 200 mg/kg/day) the greatest activity was observed when a dose of 200 mg/kg/day was injected. The effect was enhanced by adding rhEpo to optimal SCF concentrations. SCF also stimulated megakaryocyte maturation as assessed by the megakaryocyte number, the size of acetylcholinesterase-positive cells, 35Sulphur (35S) incorporation into the newly formed platelets. All these parameters were only minimally affected by the addition of rhEpo. CONCLUSIONS. These data suggest that SCF participates in the regulation of megakaryocytopoiesis and that its administration might have a role in the treatment of disorders of platelet production.