Human IL-3 stimulates endothelial cell motility and promotes in vivo new vessel formation

Angiogenesis is a critical process for growth of new capillary blood vessel s from preexisting capillaries and postcapillary venules, both in physiolog ical and pathological conditions. Endothelial cell proliferation is a major component of angiogenesis and it is regulated by several growth factors. I t has been previously shown that the human hemopoietic growth factor IL-3 ( hIL-3), predominantly produced by activated T lymphocytes, stimulates both endothelial cell proliferation and functional activation. In the present st udy, we report that hIL-3 is able to induce directional migration and tube formation of HUVEC, The in vivo neoangiogenetic effect of hIL-3 was also de monstrated in a murine model in which Matrigel was used for the delivery of the cytokine, suggesting a role of hIL-3 in sustaining neoangiogenesis, Ch allenge of HUVEC with hIL-3 lead to the synthesis of platelet-activating fa ctor (PAF), which was found to act as secondary mediator for hIL-3-mediated endothelial cell motility but not for endothelial cell proliferation. Cons istent with the role of STAT5 proteins in regulating IL-3-mediated mitogeni c signals, we herein report that, in hIL-3-stimulated HUVEC, the recruitmen t of STAT5A and STAT5B, by the beta common (beta(c)) subunit of the IL-3R, was not affected by PAF receptor blockade.