ANGIOGENIC FACTORS ARE HEMATOPOIETIC GROWTH-FACTORS AND VICE-VERSA

Angiogenic factors are potent growth factors promoting proliferation and differentiation of vascular endothelial cells. Recent evidence suggest that these factors also promote hematopoietic cell growth. The major group of angiogenic growth factors is the fibroblast growth factor (FGF) family. Two prototypes, acidic FGF and basic FGF, have been demonstrated to interact with granulopoiesis and megakaryocytopoiesis. Basic FGF stimulates granulopoiesis in long term bone marrow cultures while acidic and basic FGF promote megakaryocytopoiesis. These effects are presumably mediated via specific FGF receptors, that have been identified in bone marrow and leukemia cell lines. Besides the FGF family, angiogenic inhibitors such as platelet factor-4 (PF-4) have been found to exhibit an inhibitory effect on megakaryocytopoiesis. In contrast, it has been demonstrated that hematopoietic growth factors including granulocyte-macrophage colony-stimulating factor (GM-CSF), or erythropoietin promote angiogenesis in vivo and in vitro. In light of these recent observations and the common origin of endothelial cells and hematopoietic cells, it is suggested that angiogenic factors are hematopoietic growth factors and vice versa. However, these data must be interpreted with caution and a careful in vivo evaluation should be done before these observed in vivo effects are proven to be significant to the physiopathology of hematopoiesis or angiogenesis.