Thrombopoietin stimulates VEGF release from c-Mpl-expressing cell lines and haematopoietic progenitors

Vascular endothelial growth factor (VEGF) production was analysed in megakaryocytic cell lines and CD34⁺ haematopoietic progenitors following treatment with thrombopoietin (TPO). In CMK cells TPO caused a time- and dose-dependent increase in the levels of VEGF released into the medium. A similar effect was observed in UT-7/mpl cells transfected with the TPO receptor c-Mpl, but not in parental UT-7 cells. In CD34⁺ haematopoietic progenitor cell cultures TPO stimulated VEGF mRNA expression and VEGF protein release. Production of VEGF in CD34⁺ cultures increased with TPO-induced megakaryocytic differentiation, but not with erythroid or myelomonocytic differentiation induced respectively by erythropoietin and granulocyte-macrophage colony-stimulating factor. These results demonstrate that TPO stimulates VEGF release in c-Mpl-expressing cells and suggest that this process is an integral feature of the megakaryocytic differentiation programme.