Biological role of the human endometrial organoid secretome on extravillous trophoblast migration and invasion. OP2.

Abstract

Introduction / Background / Objectives: The migration and invasion of extravillous trophoblasts into the endometrium during early pregnancy is crucial to placentation. Dysregulation of trophoblast migration and invasion is associated with various pregnancy complications, e.g. miscarriage, preeclampsia and intrauterine growth restriction (IUGR). Successful placentation requires communication between the endometrium and trophoblasts. The endometrial microenvironment, constituted by luminal and glandular epithelial cells and stromal cells, undergoes cyclical changes regulated by sex hormones. Evidence indicates that the uterine microenvironment exerts important influence over trophoblast cell functions. However, the precise effect and mechanism of the endometrium gland secretome on trophoblast cell functions long remained unidentified due to a lack of suitable research models. This research gap was finally filled by the establishment of an ex vivo three-dimensional (3D) endometrial glandular epithelial organoid system that allowed for long-term expansion. In this study, we adopted the endometrial organoid as a model to simulate the endometrium in the menstrual cycle and early gestation using hormone stimulations. Methods: Human endometrial tissues were obtained from endometrial biopsies with written consent. The endometrial organoids were established in matrix gel using a defined culture condition. The organoids were treated with hormones mimicking the environment of the proliferative phase (estrogen, E2), the secretory phase (E2+ progesterone, P4) and pregnancy (E2+P4+human chorionic gonadotropin, hCG) for 1 week. The spent medium of the organoids was collected for omics studies (mRNA, microRNA [miRNA] and proteome) and used to treat the trophoblasts. After treatment, the cell viability and invasion/migration of the trophoblasts were then determined by CCK8 and Transwell assays, respectively. Results / Outcomes: Endometrial organoids with high expressions of endometrial gland markers, FOXA2, E-cadherin, PAEP, PAX8 and SOX17 were successfully formed and were treated with hormones mimicking the environment of the proliferative phase (E2), the secretory phase (E2+P4) and early pregnancy (E2+P4, hCG) for 1 week. The mRNA, miRNA and proteome expression profiles of endometrium organoids during different physiological phases were analyzed after collecting the secretions. Differentially expressed gene (DEG), miRNAs (DEMs) and secretory proteins (DEPs) were then verified. Networks of miRNA-RNA-protein for organoids and their products were also analyzed. Spent medium from E2+P4+hCG-treated endometrial organoids, which mimics the early pregnant microenvironment, significantly enhanced the migration and invasion of the trophoblasts compared to those obtained from proliferative/ secretory phases. Conversely, the S100A9 blocking antibody significantly impeded the enhancement effect of the conditioned medium from the early pregnancy phase on trophoblast migration and invasion. Meanwhile, none of the treatments, including the blocking antibody, had any effect on trophoblast viability. Conclusion: Using a human endometrial organoid model, we demonstrated that hormonal regulation of the decidual secretome during pregnancy might be crucial for controlling the migration capability and invasiveness of human trophoblasts.