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The specific interaction of blastocyst-derived human chorionic gonadotropin (hCG) and endometrial LH/hCG-R constitutes a fundamental component of the molecular dialogue at the materno-fetal interface. From our observations and studies from other groups, hCG was indeed shown to play a significant role in implantation and tolerance of the embryo, decidual differentiation and remodeling, as well as in placentation. The profile pattern of LH/hCG-R expression by endometrial epithelium correlates with the theoretical timing of the implantation window. Studies are currently being conducted in assisted medical procreation and in an animal model of implantation to establish the index of LH/hCG-R expression as a new biomarker of uterine receptivity for embryo implantation. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The present study investigated the first interaction that occurs between the blastocyst and endometrium during implantation. Given the ethical objections to studying implantation in humans, a mouse model was used to study the dialogue between luteinising hormone (LH) and luteinising hormone receptor (LHCGR). Several studies performed on LHCGR-knockout mice have generated controversy regarding the importance of the dialogue between LH and LHCGR during implantation. There has been no demonstration of a bioactive LH-like signal produced by the murine blastocyst. The first aim of the present study was to examine and quantify, using radioimmunoassay, the generation of a bioactive LH signal by the murine blastocyst. We went on to examine and quantify endometrial Lhcgr expression to validate the mouse model. Expression of LHCGR in mouse uteri was demonstrated using immunohistochemistry and western blot analysis. To quantify the expression of Lh in the mouse blastocyst and Lhcgr in the endometrium, reverse transcription-polymerase chain reaction (RT-PCR) and real-time quantitative (q) RT-PCR were performed. The results demonstrate that Lhcgr expression in BALB/c mouse endometrial epithelium is increased at the time of implantation and indicate that LHCGR may contribute to the implantation process. In support of this hypothesis, we identified a bioactive LH signal at the time of murine blastocyst implantation.

The success of implantation depends on a receptive endometrium, a normal blastocyst and synchronized cross-talk at the maternal-fetal interface. The progression of pregnancy then requires immunological tolerance which allows conceptus survival. A cascade of cytokines mediates this dialogue and is crucial in the cross-talk between the immune and endocrine systems. The first known human embryo-derived signal is chorionic gonadotropin (hCG) by which the embryo profoundly influences immunological tolerance and angiogenesis at the maternal-fetal interface. hCG levels coincide with the development of trophoblast tolerance. Indeed, it increases the number of uterine natural killer cells that play a key role in the establishment of pregnancy. hCG also intervenes in the development of local immune tolerance through the cellular system of apoptosis via Fas/Fas-Ligand. It modulates the Th1/Th2 balance and acts on complement C3 and C4A/B factors modulating decidual immunity. The transient tolerance evident during gestation is at least partially achieved via the presence of regulatory T cells which are attracted by hCG at the fetal-maternal interface. Finally, hCG treatment of activated dendritic cells results in an up-regulation of MHC class II, IL-10 and IDO expression, reducing the ability to stimulate T cell proliferation. Successful implantation requires an extensive endometrial angiogenesis in the implantation site. Recent data demonstrate angiogenic effects of hCG via its interaction with endometrial and endothelial LH/hCG receptors. Our review focuses on these functions of hCG, giving new insight into the endocrine-immune dialogue that exists between the conceptus and immune cells within the receptive endometrium at the time of implantation., (Copyright (c) 2010 Elsevier Ireland Ltd. All rights reserved.)

Context: 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.