[en] During the periimplantation period, human chorionic gonadotropin (hCG) plays a key role by increasing the uterine blood flow through uterine vessel vasodilatation but also through angiogenesis. Indeed, we previously demonstrated that hCG contributes to endothelial cell recruitment and vessel formation. OBJECTIVE: In this study, hCG was proposed as an arteriogenic factor that could promote perivascular cell recruitment and vessel stabilization. DESIGN: The aortic ring assay, a three-dimensional ex vivo angiogenesis system mimicking all the steps of the angiogenesis process was used to study the impact of hCG on pericyte recruitment and vessel maturation. SETTING: The study was conducted at a university hospital laboratory. MAIN OUTCOME MEASURES: Perivascular cell proliferation, migration, and apposition were quantified by computerized image analysis. RESULTS: Physiological concentrations of hCG (10-400 IU/ml) significantly enhanced pericyte sprouting and migration and gave rise to the maturation and coverage of endothelial capillaries. In a three-dimensional coculture model of endothelial and perivascular cells, hCG enhanced vessel tube formation and endothelial/mural cell adhesion. In addition, hCG stimulated the proliferation of human umbilical vein endothelial cells and smooth muscle cells. The specificity of these effects was determined by using an anti-hCG blocking antibody. Signaling pathways implicated on this hCG effect is protein kinase A and phospholipase C/protein kinase C dependent for the proliferative effect but only phospholipase C/protein kinase C for the migrative process. CONCLUSIONS: Our findings highlight a novel paracrine role of this early embryonic signal in vessel maturation by stimulating perivascular cell recruitment, migration, and proliferation.