Mechanobiology of adhesion during implantation and early placentation
Lead supervisor: R. Leube, Co-supervisor: A.-S. Smith, Junior supervisor: V. Buck Uniklinik RWTH Aachen, Institute of Molecular and Cellular Anatomy (MOCA)
Hypothesis: Blastocyst implantation involves hormone-dependent changes in endometrial adhesion and ECM properties that facilitate trophoblast invasion via mechanobiological feedback.
Examining mechanobiological aspects of endometrial receptivity. (From left to right) During implantation and early placentation uterine endometrial glands are invaded by embryo-derived extravillous trophoblast cells (EVT). Endometrial glands are isolated from endometrial biopsies as speroids and tubules or are generated in vitro in soft matrices. Trophoblast cell invasion into endometrial spheroids is studied by microscopy in vitro. Immunofluorescence microscopy shows HLA-G-positive trophoblast cells invading an endometrial spheroid. (Microscopic images from47 and unpublished)
Background: Implantation is a unique and highly species-specific process. In humans, maternal receptivity is highest during the "window of implantation" between days 19 and 23 of the menstrual cycle. During early implantation embryonic trophectoderm invades maternal endometrial epithelium first from the top upon initial contact, but soon after also from the bottom during gland invasion. Focusing on gland invasion, we observed redistribution of cell-ECM and cell-cell junctions in endometrial glands during the window of implantation46 presumably reflecting reduced endometrial epithelial polarization and cohesiveness. To study the underlying molecular mechanisms, we have developed co-culture systems of human endometrial spheroids and tubules derived from cell lines and endometrial biopsies that are confronted with human trophoblast cells47. Aims: We want to investigate the influence of endometrial polarization, ECM and hormonal stimulation on the adhesion and transmigration of immortalized human extravillous trophoblast cells. Using different co-culture arrangements we focus on the following aspects: How do polarization and hormonal stimulation of endometrial epithelial cells affect cell-cell adhesion and mechanical stability and how do these changes affect trophoblast cell adhesion and invasion? How do endometrial basement membrane and surrounding connective tissue stiffness affect trophoblast cell invasion? Approach: We will use human endometrial epithelial cell lines and primary endometrial cells derived from uterine biopsies at different stages of the menstrual cycle in 2D and 3D confrontation assays. Based on the observation that established endometrial epithelial cell lines differ in their degree of polarization, we have collected initial evidence that this corresponds to different degrees of receptivity, i.e. trophoblast invasiveness46,47. Further analyses involve immunofluorescence microscopy of whole mounts and time-lapse fluorescence microscopy of fluorescently labeled cells. Mechanical properties are determined in cooperation with A2 and D3. The resulting data are used for modeling by A4.