Preimplantation Period Of Pregnancy Research Articles

Desmosomes are reduced in the mouse uterine luminal epithelium during the preimplantation period of pregnancy: a mechanism for facilitation of implantation.

Dynamic regulation of intercellular junctions is an essential aspect of many developmental, reproductive, and physiological processes. We have shown that expression of the desmosomal protein desmoplakin decreases in the luminal uterine epithelium during the preimplantation period of pregnancy in mice. By the time of implantation (between Days 4.5 and 5 of pregnancy), desmoplakin protein can barely be detected by SDS-PAGE and Western blotting, and by immunocytochemistry, it is restricted to well-spaced, punctate dots at the apicolateral junction. Using confocal XZ series and electron microscope quantitation, both the density and distribution of desmosomes along the lateral cell surfaces of luminal epithelial cells were observed to change during early pregnancy. On Day 1 of pregnancy, desmosomes were found at high density in the apicolateral junctional complex, being present here in 79% of ultrathin sections examined, whereas on Day 5, the density was much reduced (present in only 18% of ultrathin sections examined). Desmosomes were found along the lateral surfaces, at or below the level of the nucleus, in 15% of ultrathin sections examined on Day 1 of pregnancy but in only 1% on Day 5. Desmoplakin mRNA declined during the first 4-5 days of pregnancy, along with the protein, suggesting that these changes are controlled at the level of mRNA. This study shows that desmosomes are regulated during early pregnancy, and we propose that a reduction in desmosome adhesion facilitates penetration of the luminal epithelium by trophoblast cells at implantation.

Seminal transforming growth factor beta1 stimulates granulocyte-macrophage colony-stimulating factor production and inflammatory cell recruitment in the murine uterus.

Mating in rodents evokes an inflammatory-like reaction within the uterine endometrium, characterized by extensive infiltration and activation of macrophages, dendritic cells, and granulocytes. This response is initiated when seminal vesicle gland-derived factors in the ejaculate stimulate uterine epithelial cells to release proinflammatory cytokines including granulocyte-macrophage colony-stimulating factor (GM-CSF). Experiments in which seminal vesicle secretions were fractionated by Sephacryl S-400 chromatography and assayed in vitro for GM-CSF-stimulating activity revealed that the seminal moiety coeluted with transforming growth factor beta1 (TGFbeta1) in the 150-440-kDa range and was neutralized by anti-TGFbeta1 antibodies. Comparable amounts of recombinant TGFbeta1 stimulated GM-CSF release in cultures of uterine epithelial cells from estrous mice and, when instilled into the uterine lumen, caused an increase in GM-CSF content and an infiltration of leukocytes into the endometrium similar to the postmating response. These results show that seminal vesicular fluid contains TGFbeta1 at levels sufficient to be the primary causative agent in the postmating inflammatory cascade through induction of GM-CSF synthesis by uterine epithelial cells. Seminal TGFbeta1 is thus implicated as a key factor in initiation of the remodeling events and immunological changes that occur in the uterus during the preimplantation period of pregnancy.

Leucocyte distribution in the uterus during the preimplantation period of pregnancy and phagocyte recruitment to sites of blastocyst attachment in mice

Antibodies to antigen F4/80 were used to identify monocyte-lineage cells in the preimplantation uterus and within and between early implantation sites, in intact pregnancy and using a model of delayed implantation, in mice. Neutrophils were identified by morphology and lymphocytes by immunocytochemistry and morphology. Macrophages and neutrophils were found throughout the endometrium on day 2 of pregnancy but were concentrated under the luminal epithelium. Macrophages were evenly distributed throughout the endometrium on days 3-4. Neutrophils were rarely seen on days 3-4, but lymphocytes were found throughout the endometrium, often in groups associated with glands or the luminal epithelium. Within attachment sites, a group of neutrophils was always seen associated with the luminal epithelium within implantation chambers on day 5 or, in ovariectomized, progestagen-maintained animals, at 20 h after a nidatory dose of 20 ng oestradiol. Macrophages were scarce in the subepithelial region of attachment sites and were absent from decidual tissue. 5C6, a monoclonal antibody that binds to a functional epitope of the type 3 complement receptor (CR3), a leucocyte adhesion integrin, was given before nidatory oestradiol. Treatment with 5C6 failed to modify the neutrophil recruitment to attachment sites and had no effect on the implantation rate in ovariectomized, progestagen-maintained animals given nidatory oestradiol.

Stage-specific effects of cadmium on preimplantation embryo development and implantation in the mouse

The effects of cadmium (Cd) exposure during the preimplantation period of pregnancy on the subsequent development and implantation of mouse embryos were examined. Injection of a high dose of Cd (38 μmol Cd/kg body wt.) on day 2 (D1 = vaginal plug), when the embryo is at the two-cell stage, had little effect on the initiation and maintenance of pregnancy when examined on D8. The initiation of implantation (localized sites of increased uterine vascular permeability) in a similarly treated group of mice was assessed in the morning of D5, and these sites were absent in 62% of the animals examined. Thus, Cd treatment on D2 delayed temporarily, but did not prevent implantation and was not embryolethal. In marked contrast, the same dose Cd administered on D4 caused pregnancy failure in all mice examined on D8. No implantation sites were detected on D5 and the few blastocysts recovered were degenerating. To explore the mechanisms underlying these in vivo stage-specific effects of Cd, preimplantation embryos (two-cell, four-cell, eight-cell and morulae) were exposed in vitro to a high concentration of Cd (50 μM) for 8 h followed by reculture to monitor their potential to develop to the blastocysts stage. Two-cell embryos were remarkably resistant to Cd, but toxicity increased with development, and morulae readily degenerated after Cd exposure. Analysis of the accumulation of 109Cd (50 μM) by preimplantation embryos showed little or none in two-cell embryos, but rapid accumulation and efflux of this metal by blastocysts. Removal of the zona pellucida had no influence on Cd accumulation. Nifedine (500 nM), a potent voltage-gated calcium channel blocker, and zinc (Zn; 100-fold molar excess) each significantly reduced (≈ 50% in 2 h) Cd accumulation by blastocysts, whereas N-ethylymaleimide (NEM; 20 μM) increased it. These results provide evidence that pregnancy failure after Cd exposure during the preimplantation period reflects a direct embryotoxic effect of Cd, although maternal injury by Cd may also contribute. Resistance to Cd at the two-cell stage (D2) reflects a lack of uptake of this metal, whereas sensitivity to Cd at the blastocyst stage (D4) reflects the ability to accumulate Cd.

Granulocyte-macrophage colony stimulating factor (GM-CSF): one of a family of epithelial cell-derived cytokines in the preimplantation uterus.

Granulocyte-macrophage colony stimulating factor (GM-CSF) is one of a number of lympho-haemapoietic cytokines, including CSF-1, interleukin-6 (IL-6) and leukaemia inhibitory factor (LIF) now known to be synthesized by epithelial cells in the murine uterus. GM-CSF synthesis is regulated primarily by the ovarian steroid hormone oestrogen, but is also subject to modulation by factors including a seminal component of seminal vesicle origin which stimulates a 20-fold increase in luminal fluid content at mating, and bacterial lipopolysaccharide (LPS) and the T-lymphocyte and natural killer (NK) cell product interferon-gamma (IFN gamma). In the non-pregnant mouse GM-CSF synthesis peaks at oestrus. Synthesis is maintained at comparable or moderately higher levels during the preimplantation period of pregnancy and in the non-decidualized endometrium during mid gestation. An embryotrophic activity is suggested by studies in vitro that indicate that GM-CSF stimulates attachment and outgrowth of blastocysts. It is postulated that GM-CSF is of major importance to the physiology of pregnancy through its role as a component of a local cytokine circuit acting to recruit and regulate function of endometrial leukocytes, and by its action as interlocutor and important effector arm in embryo-maternal interactions during gestation.

Localization of antigen defined by a monoclonal antibody to human 32-kDa insulin-like growth factor-binding protein in the sheep uterus at preimplantation stages of pregnancy

Employing a murine monoclonal antibody to pregnancy-associated endometrial alpha I-globulin, a 32-kDa insulin-like, growth factor-binding protein (IGF-BP) and major product of the decidualized endometrium in the human, reactivity has been detected in the luminal epithelium of the sheep endometrium during the preimplantation period of pregnancy. Staining was associated with supranuclear regions of the cytoplasm. Reactivity was restricted to the pregnant uterus and was distributed throughout the luminal epithelium in both caruncular and intercaruncular regions. The reactivity was absent from endometrial glands in intercaruncular regions. Staining was first detected at day 10, peaked at day 14 of gestation and was absent by day 16. The implications of the induction of the production of this protein by the preimplantation blastocyst in the luminal epithelium is discussed with reference to the potential role of IGF-BP in IGF action in the embryo.

Effects of dietary picolinate on mice deprived of tryptophan, niacin and vitamin B-6.

Tryptophan (Trp) is usually catabolized to CO2, H2O and urea in mammals. Quantitatively, minor branches from this pathway lead to the production of picolinate (PA) and NAD+. Although niacin is a required nutrient when NAD+ synthesis from Trp is insufficient, it is not known if dietary PA is beneficial in such conditions. Two kinds of experiment were used to investigate the effects of dietary PA. First, mice were fed on a diet deficient in Trp for six weeks to diminish endogenous PA synthesis and stores. After this time the body mass of the mice was reduced by approximately 30%. Tryptophan-deficient mice subsequently fed a nutritionally complete diet gained weight more rapidly during the first but not subsequent week(s) of recovery when PA was added to their food. Second, mice were fed on a diet deficient in Trp, niacin and vitamin B-6 during the preimplantation period of pregnancy in an attempt to acutely lower PA synthesis and perhaps alter the embryos thus produced. The rate at which preimplantation blastocysts formed trophoblastic outgrowths when cultured in vitro was stimulated by dietary PA only if these blastocysts came from mice fed on a nutritionally deficient diet. The results suggest that PA serves as a beneficial nutrient under some conditions where its endogenous synthesis may be diminished.

Effect of chorionic gonadotrophin on the pre-implantation period of pregnancy in rats.

King (1938) reported that the injection of human chorionic gonadotrophin (hcg) into rats on or before the day of implantation did not interfere with gestation, but that when given after implantation it resulted in the prolongation of pregnancy. Subsequently, Rosenfeld, Lapan & Baron (1941) confirmed that hcg inhibits parturition, but King's findings concerning the pre-implantation period remain unchallenged. The present work was designed to re-examine the effect of hcg on the pre-implantation stage of pregnancy in the light of the hypothesis that implantation in the rat must be preceded by an `oestrogen surge' stimulated by gonadotrophins (Shelesnyak, 1960; Psychoyos, 1963; Zeilmaker, 1963). Nulliparous female Sprague-Dawley rats weighing 180 to 230 g were placed overnight with either normal or vasectomized males. Pregnancy or