Cellular events during ovine implantation and impact for gestation

Abstract

The establishment of pregnancy in sheep includes elongation of the blastocyst into a filamentous conceptus, pregnancy recognition, production of histotroph, attachment of the conceptus to the endometrium for implantation, and development of synepitheliochorial placentation. These processes are complex, and this review describes some of the molecular events that underlie and support successful pregnancy. The free-floating sheep blastocyst elongates into a filamentous conceptus and metabolizes, or is responsive to, molecules supplied by the endometrium as histotroph. Amongst these molecules are SPP1, glucose and fructose, and arginine that stimulate the MTOR nutrient sensing system. The placental trophectoderm of elongating conceptuses initiate pregnancy recognition and implantation. The mononucleate cells of the trophectoderm secrete IFNT, which acts on the endometrial LE to block increases in estrogen receptor α to preclude oxytocin receptor expression, thereby preventing oxytocin from inducing luteolytic pulses of PGF2α. In addition, IFNT increases expression of IFN stimulated genes in the endometrial stroma, including ISG15, a functional ubiquitin homologue. Implantation is the initial step in placentation, and includes sequential pre-contact, apposition, and adhesion phases. Implantation in sheep includes downregulation of Muc1 and interaction of GLYCAM1, galectin 15 (LGALS15) and SPP1 with lectins and integrins (αvβ3). Sheep have synepitheliochorial placentation in which mononucleate trophectoderm cells fuse to form binucleate cells (BNCs). BNCs migrate and fuse with endometrial LE cells to form trinucleate syncytial cells, and these syncytia enlarge through continued BNC fusion to form syncytial plaques that form the interface between endometrial and placental tissues within the placentome. The placentae of sheep organize into placentomal and interplacentomal regions. In placentomes there is extensive interdigitation of endometrial and placental tissues to provide hemotrophic nutrition to the fetus. In interplacentomal regions there is epitheliochorial attachment of endometrial LE to trophectoderm, mediated through focal adhesion assembly, and areolae that take up histotroph secreted by endometrial GE.

Proteomic profile of pre‐implantational ovine embryos produced in vivo

“…Sixteen miRNA were identified and associated with biological processes such cell cycle control, embryonic stem cell proliferation and differentiation, and signalling pathways such MAPK, p53 and Wnt. These pathways play key roles during blastocyst elongation, pregnancy recognition, production of histotroph, attachment of the conceptus to the endometrium for implantation and development of synepitheliochorial placentation (Johnson et al., 2018). Also, analysis of the interaction among miRNA and embryo‐expressed genes suggest the modulation of the uterine immune environment.…”

Melatonin as a Smart Protector of Pregnancy in Dairy Cows

“…Day 16 is the time associated with the start of the process of pregnancy recognition in dairy cows. Other luminal endometrial epithelial cells throughout the uterine horn not adjacent to the trophoblast cells would remain coated with mucin [ 46 ]. Cells harvested locally within the uterine horn of projected pregnancy provided a population of cells differentially expressing a complement of antioxidant/antiapoptotic genes associated with pregnancy statuses (pregnant, pregnant–lost embryos and nonpregnant), and expression of these genes were associated with ISG15 expression + and ─in peripheral blood cells.…”

Consequences of twinning induction to Noemi ewes by a recombinant human follicle-stimulating hormone compared with pituitary-derived porcine follicle-stimulating hormone on follicular dynamics, maternal biochemical attributes, and neonatal traits

“…Congestion of embryos within a limited uterine space might have a profound effect on placental and fetal development, possibly leading to compromised pregnancies associated with poor placental development [30]. There also appears to found immune factors at an early gestation that might regulate the future embryonic development within uterus [31]. The differences in the responses due to the source of FSH would be explained from the point of the purity and specificity of the FSH molecules derived by genetic engineering.…”