Augmentation of megakaryocytopoiesis within the hematopoietic microenvironment of human granulocyte colony-stimulating factor transgenic mice

Objective Megakaryocytopoiesis was dramatically augmented in human granulocyte colony-stimulating factor transgenic mice (G-Tg) compared to littermates. We examined the characteristics of megakaryocytes and megakaryocyte progenitor cells in these mice. Materials and Methods The numbers of colony-forming unit megakaryocytes (CFU-MK) and megakaryocytes in hematopoietic organs were counted. The megakaryocytes of G-Tg were examined ultrastructurally, and bone marrow transplantation studies using congenic G-Tg (Ly5.2) and C57BL/6 (Ly5.1) were performed. The number of day-14 colony-forming unit spleen (CFU-S) that contained megakaryocytes in [Ly5.1 > G-Tg] and [G-Tg > Ly5.1] mice also was counted. Results The number of CFU-MK increased markedly in the spleen, bone marrow, and peripheral blood. The number of megakaryocytes in the spleen and bone marrow also were increased in G-Tg mice. Ultrastructural analyses revealed that megakaryocytes in G-Tg mice were immature. Bone marrow transplantation studies of [Ly5.1 > G-Tg] mice resulted in a significantly increased number of megakaryocytes compared to [G-Tg > Ly5.1] mice. The number of day-14 CFU-S that contained megakaryocytes was increased markedly in [Ly5.1 > G-Tg] mice compared to [G-Tg > Ly5.1] mice. In vitro differentiation of megakaryocytes in [Ly5.1 > G-Tg] mice was induced by interleukin-11 and thrombopoietin. Conclusion The results showed that the hematopoietic marrow microenvironment of G-Tg is important in augmenting megakaryocytopoiesis. [Ly5.1 > G-Tg] mice are potentially useful as a source of murine megakaryocytes and their progenitors.