The uterus consists of heterogeneous cells, including myometrium and endometrium that consist of luminal, glandular epithelial cells and stromal cells. It is a dynamic tissue that undergoes coordinated changes under the influence of ovarian steroid hormones, progesterone (P4) and estrogen (E2) during the menstrual cycle and to support successful pregnancy. During these phenomena, the tight regulation of P4 and E2 is required to maintain uterus health and support embryo development. In early pregnancy, temporal E2 stimuli and P4 priming are essential for embryo implantation. Establishment of uterine receptivity by the sequential actions of E2 and P4 on uterine cells is critical for successful embryo apposition, attachment, implantation, and pregnancy maintenance. Cellular E2 and P4 actions can occur directly on a specific cell type and indirectly via paracrine activity mediated by another cell type. Infertility and pregnancy loss are major public health concerns for reproductive-age females. Dysregulation of E2 and P4 action can result in infertility and pregnancy loss in females.
