Fetal-maternal communication: the role of Notch signalling in embryo implantation

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. Blastocyst-endometrial 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.