Successful embryo implantation requires synchronous development and communication between the blastocyst and the endometrium, however the mechanisms of communication in humans are virtually unknown. Recent studies have revealed that microRNAs (miRs) are present in bodily fluids and secreted by cells in culture. We have identified that human blastocysts differentially secrete miRs in a pattern associated with their implantation outcome. miR-661 was the most highly expressed miR in blastocyst culture media (BCM) from blastocysts that failed to implant (non-implanted) compared to blastocysts that implanted (implanted). Our results indicate a possible role for Argonaute 1 in the transport of miR-661 in non-implanted BCM and taken up by primary human endometrial epithelial cells (HEECs). miR-661 uptake by HEEC reduced trophoblast cell line spheroid attachment to HEEC via PVRL1. Our results suggest that human blastocysts alter the endometrial epithelial adhesion, the initiating event of implantation, via the secretion of miR, abnormalities in which result in implantation failure.

The establishment of a successful pregnancy requires the implantation of a competent blastocyst into a 'receptive' endometrium, facilitating the formation of a functional placenta. Inadequate or inappropriate implantation and placentation is a major reason for infertility and is thought to lead to first-trimester miscarriage, placental insufficiency and other obstetric complications. Blastocystendometrial interactions are critical for implantation and placental formation. The Notch signalling family is a receptor-ligand family that regulates cellular processes as diverse as proliferation, apoptosis, differentiation, invasion and adhesion. Notch signalling is achieved via cell-cell interaction; thus, via Notch, cells can have direct effects on the fate of their neighbours. Recently, a number of studies have identified Notch receptors and ligands in the endometrium, blastocyst and placenta. This review collates current knowledge of this large receptor-ligand family and explores the role of Notch signalling during implantation and placentation, drawing on information from both human and animal studies. Overall, the evidence suggests that Notch signalling is a critical component of fetal-maternal communication during implantation and placentation and that abnormal Notch expression is associated with impaired placentation and pre-eclampsia.Reproduction (2014) 147 R75-R86

Preeclampsia (PE) is a pregnancy-specific disorder characterized by hypertension and proteinuria after 20 wk gestation. Abnormal extravillous trophoblast (EVT) invasion and remodeling of uterine spiral arterioles is thought to contribute to PE development. Interleukin-11 (IL11) impedes human EVT invasion in vitro and is elevated in PE decidua in women. We demonstrate that IL11 administered to mice causes development of PE features. Immunohistochemistry shows IL11 compromises trophoblast invasion, spiral artery remodeling, and placentation, leading to increased systolic blood pressure (SBP), proteinuria, and intrauterine growth restriction, although nonpregnant mice were unaffected. Real-time PCR array analysis identified pregnancy-associated plasma protein A2 (PAPPA2), associated with PE in women, as an IL11 regulated target. IL11 increased PAPPA2 serum and placental tissue levels in mice. In vitro, IL11 compromised primary human EVT invasion, whereas siRNA knockdown of PAPPA2 alleviated the effect. Genes regulating uterine natural killer (uNK) recruitment and differentiation were down-regulated and uNK cells were reduced after IL11 treatment in mice. IL11 withdrawal in mice at onset of PE features reduced SBP and proteinuria to control levels and alleviated placental labyrinth defects. In women, placental IL11 immunostaining levels increased in PE pregnancies and in serum collected from women before development of early-onset PE, shown by ELISA. These results indicate that elevated IL11 levels result in physiological changes at the maternal-fetal interface, contribute to abnormal placentation, and lead to the development of PE. Targeting placental IL11 may provide a new treatment option for PE.placenta | trophoblast | cytokines | pregnancy P reeclampsia (PE) is a pregnancy-induced disorder characterized by hypertension and proteinuria, unique to humans, affecting ∼8% of pregnancies (1). The etiology is poorly understood (2); nevertheless, there is substantial evidence showing abnormal placentation is the key underlying cause. During pregnancy, highly invasive extravillous trophoblasts (EVT) acquire vascular-like properties to remodel uterine spiral arterioles. This creates low-resistance, large-diameter vessels that promote uteroplacental blood supply to sustain fetal growth (3, 4). It is widely accepted that inadequate trophoblast invasion and impaired uterine spiral artery remodeling is an initiating factor in the development of PE (5). This is thought to impair uteroplacental arterial flow and lead to placental oxidative stress (6). PE is associated with increased placental secretion of proinflammatory cytokines (7) and angiogenic regulators (8), thought to contribute to widespread maternal endothelial dysfunction. The clinical symptoms of PE are hypertension, proteinuria, and peripheral and/or cerebral edema. Symptoms can differentially manifest during the second (early-onset, EO), or third (late-onset, LO) trimester (9). In addition to the maternal symptoms, PE is also frequently associated with prematurit...

This study was supported by the National Health and Medical Research Council of Australia (Fellowship support #550905, #611827) and project grants by Monash IVF, Australia. There are no conflicts of interest to be declared.