Interaction of the conceptus and endometrium to establish pregnancy in mammals: role of interleukin 1β

Abstract

Implantation and the establishment of pregnancy in mammals involves an intricate interplay of hormones, cytokines, growth factors, proteins, lipids, ions and the extracellular matrix between the uterine epithelium, stroma, immune cells and the conceptus trophectoderm. The divergent nature of implantation in the mouse, human and pig provides not only an interesting contrast in the establishment of pregnancy and early embryonic development but also intriguing similarities with regard to early endometrial-conceptus signaling. An interesting pro-inflammatory cytokine expressed in a number of mammalian species during the period of implantation is interleukin-1β (IL1B). The presence of IL1B might be involved with immunotolerance at the maternal-placental interface and has been proposed as one of the mediators in placental viviparity. The production of IL1B and other proinflammatory cytokines might play a role in establishing pregnancy through modulation of the nuclear factor kappa-B (NFKB) system in a number of species. A model for the regulation of cellular progesterone receptor expression and NFKB activation for endometrial receptivity and conceptus attachment is continuing to evolve and is discussed in the present review.

Fig. 1

Immunohistochemistry for progesterone receptor B (PGRB) in the endometrium on days 8 (a, b) and 12 (c, d) of pregnancy in the pig. Note the loss of PGRB in the luminal epithelium (LE) and surface glandular epithelium (GE) on day 12 when the pig conceptuses would initiate attachment to the uterine surface (ST stroma). Bars 50 μm (from Mathew et al. 2011)

Fig. 2

Image of a hematoxylin-stained cross-section of uterine lumen from a day-12 pregnant pig (a) indicating the location of a conceptus attaching to the uterine luminal epithelium (c, d). b Immunofluorescence for NFKB is localized in the cytoplasm of the luminal epithelium (LE) distal to the conceptus (white arrowhead in a, b). c Enlarged image of a hematoxylin-stained conceptus (Co) attaching to the uterine luminal epithelium on day 12 of pregnancy (yellow arrowhead in a, c). d Immunofluorescence for NFKB has migrated to the nuclei of the LE (yellow arrowhead) near the elongating conceptus indicating that NFKB activation is locally induced by the conceptuses. Bars 50 μm (from Mathew et al. 2011)