Expression of prostanoid receptor genes in baboon chorion and decidua during pregnancy and parturition

Elevated expression of EP4 in human decidua is associated with delayed embryo expulsion during medical abortion by promoting decidual cell proliferation

Purpose: Mifepristone in conjunction with misoprostol, is widely used in China as an effective medical abortifacient. However, a small proportion of women experience the unpleasant side effects of prolonged vaginal bleeding caused by delayed embryo expulsion. The aims of this study were to determine whether the expression levels of prostanoid receptors in human decidua are associated with delayed embryo expulsion in mifepristone-misoprostol induced an early medical abortion.Methods: Discharged decidua tissues were collected from females undergoing an artificial abortion (AA) (n = 28), females with early embryo expulsion during a medical abortion (EEMA) (n = 20) and delayed embryo expulsion in medical abortion (DEMA) (n = 30). The expression levels of prostanoid receptors in human decidua were assessed with immunohistochemistry and real-time PCR methods. Further, the RNAi method was used to silence prostanoid receptors 4 (EP4) in the primary decidual cells and human endometrial adenocarcinoma cell line Ishikawa cells in vitro and cell cycle analysis of these cells was performed.Results: All five prostanoid receptors (EP1-4, FP) were observed in human early pregnancy decidua. The protein and mRNA expression level of EP4 in the DEMA group were all significantly higher than that in the EEMA group. EP4 silence induced G1/S arrest of primary decidual cells and Ishikawa cells in vitro.Conclusions: Elevated expression level of EP4 in human decidua was significantly associated with delayed embryo expulsion in early medical abortion by promoting decidual cell proliferation. Detailed studies on the nature of roles EP4 plays in human decidua will help us to develop more effective prevention and noninvasive intervention approaches for delayed embryo expulsion during a medical abortion.

Expression and regulation of prostaglandin receptors in the human placenta and fetal membranes at term and preterm

Prostaglandins (PGs) play an important role in parturition in many species, including humans. The present study examined the distribution of PG receptor subtypes (EP1-4 and FP) in intrauterine tissues at term and preterm birth. Placentas and fetal membranes were collected from patients at term in labour (n = 12) or not in labour (n = 12). Preterm tissue was collected from three different groups of patients: (1) idiopathic preterm labour (PTL) without chorioamnionitis or betamethasone (BM) treatment (n = 9), (2) idiopathic PTL that received BM with no chorioamnionitis (PTL-BM; n = 9) and (3) pregnancies that were complicated with chorioamnionitis and had no BM (PTL-CHA; n = 6). EP1-4 and FP receptors were localised and levels of expression were determined by western blot analysis. All EP receptors and FP were localised to the amnion, placenta and choriodecidua. Moreover, isolated amnion mesenchymal, amnion epithelial, chorion trophoblast and syncytiotrophoblast cells in primary culture also expressed PG receptors. A significant increase was observed in EP1, EP3 and FP expression in placenta, chorion and amnion with labour. Maternal betamethasone treatment increased EP1, EP3 and FP receptor protein expression and chorioamnionitis decreased expression in all the receptor subtypes. These changes in PG receptors in the fetal membranes are consistent with the development of a feed-forwards cascade mediated through PG action that may contribute to the birth process.

Regional Expression of Prostaglandin E2 and F2alpha Receptors in Human Myometrium, Amnion, and Choriodecidua with Advancing Gestation and Labor1

The change from uterine quiescence to enhanced contractile activity may be due to the differential expression of prostaglandin receptors within the myometrium and fetal membranes, in a temporal and topographically distinct manner. To address this question, we determined the localization and expression of the PGE2 receptor subtypes (PTGER1-4) and the PGF2alpha receptor (PTGFR) in paired upper and lower segment myometrium, amnion, and choriodecidual samples throughout human pregnancy, with and without labor. All receptor subtypes were found throughout the muscle layers in both the upper and lower uterine segments, colocalizing with alpha smooth muscle actin. A change in intracellular localization was observed at term labor, where PTGER1 and PTGER4 were predominately associated with the nucleus. Minimal changes in the expression of the PGE2 and PGF2alpha receptor subtypes were observed with gestational age, labor, or between the upper and lower myometrial segments. Receptor expression in maternal and fetal tissues differed between the receptor subtypes; PTGER1 and PTGER4 were predominately expressed in the fetal membranes, PTGER2 was greatest in the myometrium, whereas PTGER3 and PTGFR were similarly expressed in the myometrium and fetal membranes. Myometrial activation through the prostaglandin receptors is perhaps more subtle and may be mediated by a balance between one or several of the prostaglandin receptor subtypes together with other known contraction associated proteins. Lack of coordination in receptor expression between the myometrium and fetal membranes may indicate different regulatory mechanisms between these tissues, or it may suggest a function for these receptors in the amnion and choriodecidua that is independent of that seen in the myometrium.

Localization and expression of prostaglandin E2 receptors in human placenta and corresponding fetal membranes with labor

OBJECTIVE

The effects of prostaglandin E2 (PGE2) are mediated through G-protein coupled receptors, acting via different second messengers. The aim of this study was to characterize the temporal and tissue specific localization and expression of the PGE2 receptor subtypes (EP1-4) in uteroplacental tissues during human pregnancy.

STUDY DESIGN

Placenta and fetal membranes were collected after delivery at preterm or term, each with or without labor. The localization and expression of the PGE2 receptor subtypes were determined by immunohistochemistry and Western blot.

RESULTS

All 4 receptors were expressed in the placenta and fetal membranes; only EP3 was present in the syncytiotrophoblast layer. EP1 to EP4 were consistently expressed across gestation in the fetal membranes; however, a different cellular localization with labor was observed in the amnion for EP1, EP2, and EP4.

CONCLUSION

The presence of these receptors in the placenta and fetal membranes may indicate autocrine roles for PGE2 in the signaling pathways associated with placental function and parturition.

Morphological events in the primate endometrium in the presence of a preimplantation embryo, detected by the serum preimplantation factor bioassay

BACKGROUND

Hormonal modulation of the endometrium towards receptivity is well established; however, the role of embryonic stimuli in modulation of the endometrium prior to implantation, especially in primates, is unknown. The aim of the present study was to evaluate the endometrial histology when the embryo was present in its vicinity prior to implantation.

METHODS

Preimplantation factor (PIF) bioassay was used as a tool to detect the presence of an embryo in the uterine lumen of mated bonnet monkeys (Macaca radiata) (n=9). The control group comprised seven non-mated animals. The specificity of the PIF bioassay for the presence of an embryo was tested by studies in pregnant humans and monkeys. The effects of embryonic stimuli on the endometrial morphology were analysed by routine haematoxylin-eosin staining. The expressions of CD34, an endothelial cell marker, alpha-smooth muscle actin (alpha-SMA), a marker for blood vessel maturation, and prolactin, a marker of endometrial decidualization, were studied by immunohistochemistry.

RESULTS

That PIF is embryo specific was established by its presence in sera of pregnant humans, monkeys and also in embryo culture media. Six mated bonnet monkeys were found to be PIF positive. Morphologically, the endometria from these PIF-positive animals showed the presence of the pre-epithelial plaque reaction, increased angiogenesis and stromal compaction. The significantly increased number of CD34- and alpha-SMA-positive blood vessels (P<0.05) in the endometria of PIF-positive animals indicated increased angiogenesis in response to embryonic stimuli. The endometrial expression of immunoreactive prolactin was also significantly increased (P<0.05) in the PIF-positive animals, indicating decidualization.

CONCLUSIONS

Using PIF as a marker to detect early pregnancy in bonnet monkeys, we have shown that the embryo induces a pre-epithelial plaque type of reaction, increased angiogenesis and decidual reaction in the endometrium prior to implantation.

Topographical specialization of prostaglandin function in late pregnancy and at parturition in the baboon

Prostaglandins play key central roles in both the maintenance of pregnancy and parturition. Extensive data exist from studies in human pregnancy but the needs of clinical management and the inability to conduct carefully controlled perturbation studies in human pregnancy make it necessary to obtain information from nonhuman primate models. We have used the pregnant baboon to evaluate production, metabolism and receptor mediated actions of prostaglandins in late gestation to demonstrate that expression of key genes is tightly controlled in enzyme-specific, gestation age-specific, tissue-specific and uterine region-specific fashion.