Rationale: The pro-angiogenic capacities of endothelial progenitor cells are now well established, and their involvement in neovascularization events in adults has stimulated the research in the field of angiogenic therapy based on transplant of these cells. Current data converge towards the notion of two cell types with endothelial phenotype, defined at least by their kinetics of appearance in culture: early endothelial progenitor cells (CFU-EC or CAC) and late (ECFC). Our team has shown that the therapeutic injection of bone marrow mononuclear cells (BM-MNC) led to neovascularization of the ischemic site in patients with critical limb ischemia, and that the new vessels formed bore the phenotype of ECFC. We initially measured the concentrations of different proteins modulating angiogenesis in patients with ischemic and cardiovascular diseases, or involving vascular abnormalities associated with fibrosis. Thus, the transforming growth factor - ß1 (TGF-ß1) in idiopathic pulmonary fibrosis, the thrombospondin-1 (TSP-1) in peripheral artery disease, and the placental growth factor (PlGF) in patients with cardiovascular diseases [acute coronary syndrome (ACS), patients undergoing valve surgery or coronary artery bypass surgery], emerged as potential plasmatic biomarkers in these pathological settings, and have been studied in the biology of human ECFC.Results: TGF-ß1 plasma level is increased in patients with idiopathic pulmonary fibrosis (IPF) compared to the control population; it exerts a pro-angiogenic effect in vivo (vascularization of Matrigel ®-plugs) and in vitro (proliferation and migration of ECFC) via ALK-1, ALK-5 and TGF-ßRII receptors. TSP-1 plasma level is increased in patients with peripheral artery disease (PAD) compared to the control population. In addition, the new vessels formed in PAD patients treated by local injection of BM-MNC express TSP-1. In murine models of Matrigel ®-plugs and hindlimb ischemia, TSP-1 induces a decrease in plugs vascularization and impaired revascularization of ischemic limb. In vitro, TSP-1 increases ECFC adhesion via an N-terminal dependent mechanism and reduces their angiogenic potential (proliferation and migration) via its binding to CD47 receptor, which activates the SDF-1/CXCR4 signaling pathway. PlGF plasma level is increased in ACS patients compared with the control population and stable angina patients and is also increased in patients undergoing cardiac surgery. PlGF-1 and -2 potentiate ECFC tubulogenesis in vitro via phosphorylation of the VEGFR1 receptor. This effect was abolished when the ECFC VEGFR1 is inhibited by RNA interference or by the chemical compound "4321". In addition this compound "4321" inhibits the vascularization of Matrigel ®-plugs, and revascularization of the ischemic limb in the hindlimb ischemia model.Conclusions: TGF-ß1 is involved in the IPF vascular remodeling through ECFC; TSP-1 is a potential biomarker of angiogenesis induced by ECFC in PAD; the inhibition of the PlGF/VEGFR1 pathway modulates ECFC tubulogenesis, cells involved in the formation of new vessels. We thus identified three proteins that modulate angiogenesis in three different pathological settings characterized by a vascular remodeling and where ECFC are involved in their pathophysiology. These three proteins therefore state as potential plasmatic biomarkers, modulating ECFC angiogenic properties and are able to influence their efficacy as a cell therapy product. These plasmatic biomarkers likely play a role in the homeostasis of those pathologies progress.
