Expression and regulation of cytosolic prostaglandin E synthase in mouse uterus during the peri-implantation period

Prostaglandin E(2) (PGE(2)) is considered important for blastocyst spacing, implantation, and decidualization in rodent uteri. PGE synthase (PGES) catalyzes the isomerization of PGH(2) to PGE(2). Two isoforms of PGES exist: microsomal PGES (mPGES) and cytosolic PGES (cPGES); however, the expression and regulation of cPGES in the mammalian uterus during early pregnancy are still unknown. The aim of this study was to investigate the differential expression of cPGES in mouse uterus during early pregnancy and its regulation under different conditions using in situ hybridization and immunohistochemistry. A strong level of cPGES mRNA signal was exhibited in the stromal cells at the implantation site on Day 5 of pregnancy, whereas cPGES immunostaining was strongly detected in the luminal epithelium. The signals for both cPGES mRNA and immunostaining were strongly detected in the decidualized cells from Days 6-8 of pregnancy. A basal level of cPGES mRNA signal and immunostaining was exhibited in the uterus in delayed implantation. After delayed implantation was terminated by estrogen treatment and embryo implantation was initiated, cPGES mRNA signal was strongly detected in the stroma underlying the luminal epithelium at the implantation site, and cPGES immunostaining was strongly observed in the luminal epithelium surrounding the implanting blastocyst. A strong cPGES mRNA signal and immunostaining were detected in decidualized cells under artificial decidualization, whereas only a basal level of cPGES mRNA signal and immunostaining were observed in the control horn. Our data suggest that cPGES may play an important role during implantation and decidualization.     

Benzo(a)pyrene inhibits endometrial cell apoptosis in early pregnant mice via the WNT5A pathway

Benzo(a)pyrene (BaP) is an endocrine-disrupting pollutant present in various aspects of daily life, and studies have demonstrated that BaP exerts reproductive toxicity. We previously showed that BaP damages endometrial morphology and decreases the number of implantation sites in early pregnant mice, but the mechanisms underlying these effects remain unclear. The endometrial function is crucial for implantation, which is associated with endometrial cell apoptosis. In this study, we focused on the effect of BaP on endometrial cell apoptosis and the role of WNT signaling during this process. Pregnant mice were gavaged with corn oil (control group) or 0.2 mg·kg⁻¹·day ⁻¹ BaP (treatment group) from Days 1 to 6 of pregnancy. BaP impaired endometrial function by decreasing the expression of HOXA10 and BMP2, two markers of receptivity and decidualization. WNT5A and β-catenin were activated in the BaP group. BaP affected the expression of apoptosis-related proteins and inhibited the apoptosis of endometrial stromal cells. In vitro, human endometrial stromal cells (HESCs) were treated with different concentrations of BaP (dimethyl sulfoxide (DMSO); 5, 10 µM). WNT5A and β-catenin were also upregulated in the BaP treatment group. HESC apoptosis was restrained by BaP. Inhibiting WNT5A by SFRP5 partially restored the effect of BaP on apoptosis. In summary, these results suggested that BaP exposure during early pregnancy activates WNT5A/β-catenin signaling pathway, which inhibits the endometrial cell apoptosis and potentially destroys endometrial function.     

Changes in the temporal and spatial expression of H beta 58 during formation and maturation of the chorioallantoic placenta in the Rat

Cloning and sequencing of a cDNA amplified by RNA fingerprinting at the implantation site of pregnant rats revealed 80% similarity with H beta 58, previously shown to be essential for formation of the chorioallantoic placenta in the mouse. H beta 58 mRNA was detected in the endometrium of hormonally sensitized rats stimulated to undergo decidualization and in the contralateral uterine horns lacking a decidual stimulus, indicating that uterine expression of H beta 58 mRNA did not require decidualization or the presence of a blastocyst. Immunodetection in the early postimplantation uterus (Days 6-8 of pregnancy) showed H beta 58 localized in the luminal and glandular epithelia and some stromal cells. Decidual cells at Day 6 of pregnancy expressed H beta 58, and by Day 9 of pregnancy, the protein localized throughout the maternal decidua. The temporal and spatial distribution of H beta 58 in the developing chorioallantoic placenta was assessed at Days 10, 12, and 14 of pregnancy. Immunoreactive H beta 58 localized to erythroid cells within the developing fetal vasculature of the chorioallantoic primordia at Day 10 of pregnancy. By Day 12, the fetal vasculature extended into the placental labyrinth, and the erythroid stem cells continued to strongly express H beta 58. At Day 14 of pregnancy, immunoreactivity became evident in the trophoblast giant cells and syncytiotrophoblast of the fetal placenta. As the chorioallantoic placenta matured (Day 18), H beta 58 mRNA was 3.6-fold higher in the labyrinth compared with the junctional region. Stable cell lines (HRP/LRP) isolated from the rat labyrinthine placenta expressed H beta 58 mRNA and protein. The expression pattern of H beta maternal and fetal placental tissues and its early expression in fetal erythroid stem cells during formation and maturation of the chorioallantoic placenta suggest that H beta 58 plays key roles in the regulatory networks that control hematopoietic development and placentation.     

Maternal pentraxin 3 deficiency compromises implantation in mice

Reduced litter sizes in mice missing pentraxin 3 (Ptx3) have been attributed to fertilization failure. However, our global gene expression studies showed high uterine Ptx3 expression at the implantation site in mice, suggesting its role in blastocyst implantation. We initiated molecular and genetic studies in mice to explore the importance of uterine Ptx3 in this process. We found that Ptx3 is expressed in a unique and transient fashion at implantation sites. With the initiation of implantation on midnight of Day 4 of pregnancy, Ptx3 is expressed exclusively in stromal cells at the site of blastocysts. On Day 5, its expression is more intense in decidualizing stromal cells, but it disappears on Day 6. The expression again becomes evident in the deciduum on Day 7, followed by a more robust expression on Day 8, particularly at the antimesometrial pole. From Day 9, with the initiation of placentation, Ptx3 expression becomes undetectable. These results suggest a role for PTX3 in implantation and decidualization. Indeed, deletion of Ptx3 results in both compromised implantation and decidualization. Interleukin 1B (IL1B), a known inducer of Ptx3, is also transiently expressed in stromal cells at the implantation site, suggesting that IL1B is an inducer of uterine Ptx3 expression. In fact, uterine Ptx3 expression follows that of Il1b induced by lipopolysaccharide treatment on Day 7 of pregnancy. Collectively, these findings provide evidence for an important role for PTX3 in implantation and decidualization. This study has clinical implications, since PTX3 is expressed in the receptive endometrium, and trophoblast cells influence decidual Ptx3 expression in humans.     

Expression and Function of Kisspeptin during Mouse Decidualization

Background

Plasma kisspeptin levels dramatically increased during the first trimester of human pregnancy, which is similar to pregnancy specific glycoprotein-human chorionic gonadotropin. However, its particular role in the implantation and decidualization has not been fully unraveled. Here, the study was conducted to investigate the expression and function of kisspeptin in mouse uterus during early pregnancy and decidualization.

Methodology/Principal Findings

Quantitative PCR results demonstrated that Kiss1 and GPR54 mRNA levels showed dynamic increase in the mouse uterus during early pregnancy and artificially induced decidualization in vivo. KISS-1 and GPR54 proteins were spatiotemporally expressed in decidualizing stromal cells in intact pregnant females, as well as in pseudopregnant mice undergoing artificially induced decidualization. In the ovariectomized mouse uterus, the expression of Kiss1 mRNA was upregulated after progesterone or/and estradiol treatment. Moreover, in a stromal cell culture model, the expression of Kiss1 and GPR54 mRNA gradually rise with the progression of stromal cell decidualization, whereas the attenuated expression of Kiss1 using small interfering RNA approaches significantly blocked the progression of stromal cell decidualization.

Conclusion

our results demonstrated that Kiss1/GPR54 system was involved in promoting uterine decidualization during early pregnancy in mice.     

Differential expression of prostaglandin E receptor subtype EP2 in rat uterus during early pregnancy

PGE2 is essential for mammalian female reproduction. This study was to examine the expression of EP2 gene in the rat uterus during early pregnancy, delayed implantation and artificial decidualization by in situ hybridization and immunohistochemistry. There was no detectable EP2 mRNA expression in the uterus from days 1 to 4 of pregnancy (day 1 = day of vaginal sperm). A low level of EP2 immunostaining was observed in the luminal and glandular epithelium from days 1 to 4 of pregnancy. Both EP2 mRNA and protein expression were highly detected in the luminal epithelium at implantation sites on day 6 of pregnancy. EP2 expression decreased from day 7 of pregnancy and was undetectable on days 8 and 9 of pregnancy. After delayed implantation was terminated by estrogen treatment and the embryo implanted, both EP2 mRNA and protein expression were strongly observed in the luminal epithelium at the implantation site. There was no detectable EP2 expression in both control and decidualized uteri. In conclusion, these data suggest that EP2 expression at implantation site may play an important role during embryo implantation in rats.     

Decidualization regulates the expression of the endometrial chorionic gonadotropin receptor in the primate

Chorionic gonadotropin (CG) plays an important role in establishing a receptive endometrium by directly modulating the function of both endometrial stromal and epithelial cells in the baboon. The focus of this study was to characterize changes in CG receptor (LHCGR, also known as CG-R) expression during the menstrual cycle and early pregnancy, particularly during decidualization. LHCGR was localized by using a peptide-specific antibody generated against the extracellular domain. Immunostaining was absent in any of the cell types during the proliferative phase of the cycle. In contrast, during the secretory phase, both luminal and glandular epithelial cells stained positively. Stromal staining was confined to the cells around spiral arteries (SAs) and in the basalis layer. This stromal staining pattern persisted at the implantation site between Days 18 and 25 of pregnancy and after CG infusion. However, as pregnancy progressed (Days 40 to 60), staining for LHCGR was dramatically decreased in the stromal cells. These data were confirmed by nonisotopic in situ hybridization. To confirm whether the loss of LHCGR was associated with a decidual response, stromal fibroblasts were decidualized in vitro, and cell lysates obtained after 3, 6, and 12 days of culture were analyzed by Western blotting. LHCGR protein decreased with the onset of decidualization in vitro, confirming the in vivo results. Addition of CG to decidualized cells resulted in the reinduction of LHCGR in the absence of dbcAMP. We propose that CG acting via its R on stromal cells modulates SA in preparation for pregnancy and trophoblast invasion. As pregnancy progresses, further modification of SA by migrating endovascular trophoblasts and subsequent decidualization results in the downregulation of LHCGR. This inhibition of LHCGR expression also coincides with the decrease of measurable CG in peripheral circulation.     

Expression of stathmin family genes in the murine uterus during early pregnancy

Stathmin, a cytosolic phosphoprotein that regulates microtubule dynamics during cell-cycle progression, is abundantly expressed at embryo implantation sites in rats. Here, we characterized the expression of stathmin and its family genes in the murine uterus during the peri-implantation period. Stathmin protein was expressed in the glandular and luminal epithelium, blood vessels, and stromal cells on day 3 of pregnancy. On the day of implantation (day 5), stathmin was mainly localized in blood vessels in the endometrium. On day 7, intense stathmin expression was limited to capillary vessels and secondary decidual cells. Stathmin expression was higher at implantation sites than at uterine segments between implantation sites and increased during oil-induced decidualization. Although the artificially-induced deciduoma weights and number of implantation sites were similar between stathmin-knockout (KO) and wild-type (WT) mice, the stathmin-KO mice had fewer newborn pups (reduced by 30%). The expression of alkaline phosphatase, desmin, and cyclin D3 was attenuated in decidual zones of stathmin-KO mice. Messenger RNA level of the stathmin family gene, SCG10, was high at the time of decidualization in WT and stathmin-KO mice. In contrast, the others of stathmin family members, SCLIP and RB3 were highly expressed in stathmin-KO mice compared to WT mice. These results suggest that stathmin and stathmin family genes are expressed in the murine endometrium with enhanced expression in the implantation or the decidualization process.     

Expression of matrix metalloproteinases 2 and 9 in the mouse uterus during implantation and oil-induced decidualization

During implantation, matrix metalloproteinases are believed to play roles in the tissue remodelling that accompanies decidualization in the endometrium and in embryo invasion. The objective of this study was to characterize further the expression of matrix metalloproteinases 2 and 9 in the mouse uterus during early pregnancy and oil-induced decidualization. mRNA encoding matrix metalloproteinase 2 was detected in pregnant uteri and uteri undergoing oil-induced decidualization by northern blot analyses. The steady-state concentrations of mRNA encoding matrix metalloproteinase 2 did not change significantly in implantation compared with inter-implantation areas on days 5-8 of pregnancy but were significantly lower in stimulated compared with non-stimulated uterine horns during artificially induced decidualization. mRNA encoding matrix metalloproteinase 9 was also detected in uteri undergoing oil-induced decidualization but not in pregnant uteri. Its concentration was significantly greater in uterine horns undergoing oil-induced decidualization compared with control horns. Immunoreactive matrix metalloproteinases 2 and 9 were detected in the uterus during early pregnancy and oil-induced decidualization by immunohistochemistry, localized to the endometrial stroma, but the staining progressively became weaker and was absent in areas that had undergone decidualization. By day 8 of pregnancy and 72 h after the induction of decidualization, matrix metalloproteinase 2 and 9 proteins remained mainly in the region of non-decidualized stromal cells adjacent to the myometrium. In implantation segments, they were also localized to the region of the trophoblast giant cells. The second objective of the present study was to determine whether endometrial stromal cells isolated from uteri sensitized for decidualization express matrix metalloproteinases 2 and 9. Northern blot analyses and gelatin zymography showed that these cultured cells expressed matrix metalloproteinase 2 and 9, and that transforming growth factor beta1 significantly increased matrix metalloproteinase 9 expression. The results of the present study further characterize matrix metalloproteinases 2 and 9 expression in the uterus during implantation and artificially induced decidualization.     

Gamma‐amino butyric acid and the A‐type receptor suppress decidualization of mouse uterine stromal cells by down‐regulating cyclin D3

Uterine decidualization, characterized by stromal cell proliferation and differentiation into polyploid decidual cells, is critical to the establishment of pregnancy in mice, although the mechanism underlying this process remains poorly understood. This study is the first to investigate the expression of gamma‐amino butyric acid (GABA) and the GABA A‐type receptor π subunit (GABPR) in the early‐pregnancy mouse uterus and their roles in decidualization. The expression of GABRP was detected from Day 4 to 8 of pregnancy. The effects of GABA and GABA A‐type receptor on cell proliferation and apoptosis were investigated using the Cell Titer 96® AQueous One Solution Cell Proliferation Assay and flow cytometry. The levels of cyclin D3 protein were measured in cultured stromal cells artificially induced to undergo decidualization, and treated with GABA and a GABA A‐type receptor agonist or antagonist, respectively, at the same time. mRNA expression of gabrp in implantation sites was lower than that in inter‐implanted sites. GABA and GABRP protein were localized in the luminal and glandular epithelium, stromal cells, and decidual cells. In vitro, GABPR protein level was decreased in cultured stromal cells during the decidualization process. The addition of GABA and the GABA A‐type receptor agonist Muscimol inhibited stromal cell proliferation, promoted apoptosis, and arrested cells in S‐phase, followed by decreased expression of cyclin D3. These results show that in mice, GABA was actively involved in inhibiting stromal cell proliferation and suppresses decidualization progress through GABA A‐type receptors by down‐regulating cyclin D3 level. Mol. Reprod. Dev. 80: 59–69, 2013. © 2012 Wiley Periodicals, Inc.     

Decreased NDRG1 expression is associated with pregnancy loss in mice and attenuates the in vitro decidualization of endometrial stromal cells

Embryo implantation is an essential step for a successful pregnancy, and any defect in this process can lead to a range of pregnancy pathologies. The objective of this study was to explore the role of N‐myc downregulated gene 1 (NDRG1) in embryo implantation. It was found that uterine NDRG1 expression has a dynamic pattern during the estrous cycle in nonpregnant mice and that uterine NDRG1 expression was elevated during the implantation process in pregnant mice. The distinct accumulation of NDRG1 protein signals was observed in the primary decidual zone adjacent to the implanting embryo during early pregnancy. Furthermore, uterine NDRG1 expression could be induced by activated implantation or artificial decidualization in mice. Decreased uterine NDRG1 expression was associated with pregnancy loss in mice and was associated with recurrent miscarriages in humans. The in vitro decidualization of both mouse and human endometrial stromal cells (ESCs) was accompanied by increased NDRG1 expression and downregulated NDRG1 expression in ESCs effectively inhibited decidualization. Collectively, these data suggest that NDRG1 plays an important role in decidualization during the implantation process, and the abnormal expression of NDRG1 may be involved in pregnancy loss.