Marilen Benner

CHAPTER 6 154 Attachment Implantation Apposition Selection Placentation: Villi development Decidual reaction Endometrial contribution Key processes Interaction with invading trophoblast Adaptation upon blastocyst encounter Pinopode formation Cytoskeleton remodeling Change in receptor expression Epithelial permeability Lymphocyte attraction Vascularization uNK cell attraction of trophoblast Induction of lymphocytes L-selectin receptor L-selectin Pinopodes Signalling between blastocyst and endometrium for succesful attachment Invasion and trophoblast di erentiation initiate placenta formation Spiral artery remodeling instrumental for fetal and placental development IVS IVS Decidua uNK ... ... ... endo- vascular troph. Possible impact of microbiota on various levels? Figure 1. Illustration of key elements in blastocyst-endometrium interaction needed for a receptive endometrium. Due to its important contributions during early placentation, the endometrium is key to healthy pregnancy. During the window of opportunity, day 19-24 of the menstrual cycle, the endometrium resides in a receptive state that allows selection, apposition and attachment of a healthy blastocyst. Implantation is marked by invasive growth and differentiation of trophoblast cells. Proper interaction of invading trophoblast and local immunity is needed to achieve correct villi development and a healthy placenta. All these highly regulated properties of the endometrium needed in the initial phase of pregnancy are possibly affected by uterine microbiota. IVS , intervillous space; uNK, uterine natural killer cell.