Endometrial extracellular matrix components do not change over the course of embryonic diapause and reactivation in the roe deer (Capreolus capreolus)

Abstract

Embryo implantation is a critical step for successful pregnancy establishment as it requires the synchronization and interaction of the developing blastocyst and the endometrium. A large percentage of unsuccessful pregnancies can be attributed to implantation failure. In cattle, around 30% of losses are thought to occur during the peri-implantation period (Wiltbank et al., 2016). Embryo implantation involves major changes within the endometrium relating to the type of placentation. In species undergoing invasive forms of implantation, including rodents, lagomorphs humans, or dogs [reviewed in (Carter, 2020) and (Kowalewski et al., 2021)], the embryo erodes the uterine epithelium and connective tissue, and thereby, comes into more intimate contact with maternal uterine structures.In ruminants, suidae and equidae, non-invasive appositioning of the embryo to the uterine epithelium gives rise to a synepitheliochorial or epitheliochorial placenta [reviewed in (Chavatte-Palmer & Tarrade, 2016)]. In any case, remodelling of the endometrial tissue to allow conceptus attachment is required. The modification of the extracellular matrix (ECM) is crucial for altering the tissue architecture (Lu et al., 2011). Moreover, the property of the ECM contributes to the distribution of growth factors and other signalling molecules (Kirkpatrick et al., 2004). Co-occurring changes in cell morphology are mediated through the cytoskeleton, which is connected to the ECM through integrin receptors and linker proteins (Whitby et al., 2020). Not surprisingly, changes in expression and/or