Expression and regulation of prostaglandin E synthase isoforms in human myometrium with labour

SOX4 exerts contrasting regulatory effects on labor-associated gene promoters in myometrial cells

The uterine muscular layer, or myometrium, undergoes profound changes in global gene expression during its progression from a quiescent state during pregnancy to a contractile state at the onset of labor. In this study, we investigate the role of SOX family transcription factors in myometrial cells and provide evidence for the role of SOX4 in regulating labor-associated genes. We show that Sox4 has elevated expression in the murine myometrium during a term laboring process and in two mouse models of preterm labor. Additionally, SOX4 differentially affects labor-associated gene promoter activity in cooperation with activator protein 1 (AP-1) dimers. SOX4 exerted no effect on the Gja1 promoter; a JUND-specific activation effect at the Fos promoter; a positive activation effect on the Mmp11 promoter with the AP-1 dimers; and surprisingly, we noted that the reporter expression of the Ptgs2 promoter in the presence of JUND and FOSL2 was repressed by the addition of SOX4. Our data indicate SOX4 may play a diverse role in regulating gene expression in the laboring myometrium in cooperation with AP-1 factors. This study enhances our current understanding of the regulatory network that governs the transcriptional changes associated with the onset of labor and highlights a new molecular player that may contribute to the labor transcriptional program.

Up-regulation of cytosolic prostaglandin E synthase in fetal-membrane and amniotic prostaglandin E2 accumulation in labor

Prostaglandin E2 (PGE2) is known to have important roles in labor, but the detailed mechanism underlying the spontaneous human labor remains unknown. Here, we examined the involvement of prostaglandin biosynthetic enzymes and transporter in the accumulation of PGE2 in amniotic fluid in human labor. PGE2 and its metabolites were abundant in amniotic fluid in deliveries at term in labor (TLB), but not at term not in labor (TNL). In fetal-membrane Transwell assays, levels of PGE2 production in both maternal and fetal compartments were significantly higher in the TLB group than the TNL group. In fetal-membrane, the mRNA level of PTGES3, which encodes cytosolic prostaglandin E synthase (cPGES), was significantly higher in TLB than in TNL, but the mRNA levels of the other PGE2-synthase genes were not affected by labor. Moreover, the mRNA level of PTGS2, which encodes cyclooxygenase-2 (COX-2) in the amnion was significantly higher in TLB than in TNL. Western blot analyses revealed that the levels of COX-1 and COX-2 were comparable between the two groups, however, the level of cPGES was relatively higher in TLB than in TNL. COXs, cPGES, and prostaglandin transporter (SLCO2A1) proteins were all expressed in both chorionic trophoblasts and amniotic epithelium. These findings suggest that COXs, cPGES and SLCO2A1 contribute to PGE2 production from fetal-membrane in labor.

The Role(s) of Eicosanoids and Exosomes in Human Parturition

The roles that eicosanoids play during pregnancy and parturition are crucial to a successful outcome. A better understanding of the regulation of eicosanoid production and the roles played by the various end products during pregnancy and parturition has led to our view that accurate measurements of a panel of those end products has exciting potential as diagnostics and prognostics of preterm labor and delivery. Exosomes and their contents represent an exciting new area for research of movement of key biological factors circulating between tissues and organs akin to a parallel endocrine system but involving key intracellular mediators. Eicosanoids and enzymes regulating their biosynthesis and metabolism as well as regulatory microRNAs have been identified within exosomes. In this review, the regulation of eicosanoid production, abundance and actions during pregnancy will be explored. Additionally, the functional significance of placental exosomes will be discussed.

Cyclooxygenase inhibitors for treating preterm labour: What is the molecular evidence? 1

Preterm birth (<37 weeks of gestation) significantly increases the risk of neonatal mortality and morbidity. As many as half of all preterm births occur following spontaneous preterm labour. Since in such cases there are no known reasons for the initiation of labour, treatment of preterm labour (tocolysis) has sought to stop labour contractions and delay delivery. Despite some success, the use of cyclooxygenase (COX) inhibitors is associated with maternal/fetal side effects, and possibly increased risk of preterm birth. Clinical use of these drugs predates the collection of molecular and biochemical evidence in vitro, examining the expression and activity of COX enzymes in pregnant uterine tissues with and without labour. Such evidence is important to the rationale that COX enzymes are, or are not, appropriate targets for the tocolysis. The current study systematically searched existing scientific evidence to address the hypothesis that COX expression/activity is increased with the onset of human labour, in an effort to determine whether there is a rationale for the use of COX inhibitors as tocolytics. Our review identified 44 studies, but determined that there is insufficient evidence to support or refute a role of COX-1/-2 in the onset of preterm labour that supports COX-targeted tocolysis.

Runt-related transcription factor 1 (RUNX1) deficiency attenuates inflammation-induced pro-inflammatory and pro-labour mediators in myometrium

Identifying new targets that regulate myometrial activation are required to develop effective treatments to stop preterm labor. Inflammation, which can be induced by sterile or infective insults, plays a role in initiating and maintaining uterine contractions. Several high throughput transcription screening studies have identified an upregulation of runt-related transcription factor 1 (RUNX1) mRNA expression in myometrium with labor. The role of RUNX1 in labor, however, is not known. We report increased RUNX1 during late gestation which was further augmented in labor, suggesting that RUNX1 may be involved in the transition of the myometrium from a quiescent into a contractile state in preparation for labor. By inhibiting the expression of RUNX1, we have established that RUNX1 induces the expression of pro-inflammatory cytokines, chemokines, adhesion molecules, contraction-associated proteins OXR and PTGFR, the uterotonic PGF_2α, and the ECM remodelling enzyme MMP9. Targeting RUNX1 may be a novel approach to prevent preterm labor.

The expression of genes involved in myometrial contractility changes during ex situ culture of pregnant human uterine smooth muscle tissue

Background: Ex situ analyses of human myometrial tissue has been used to investigate the regulation of uterine quiescence and transition to a contractile phenotype. Following concerns about the validity of cultured primary cells, we examined whether myometrial tissue undergoes culture-induced changes ex situ that may affect the validity of in vitro models. Objectives: To determine whether human myometrial tissue undergoes culture-induced changes ex situ in Estrogen receptor 1 (ESR1), Prostaglandin-endoperoxide synthase 2 (PTGS2) and Oxytocin receptor (OXTR) expression. Additionally, to determine whether culture conditions approaching the in vivo environment influence the expression of these key genes. Methods: Term non-laboring human myometrial tissues were cultured in the presence of specific treatments, including; serum supplementation, progesterone and estrogen, cAMP, PMA, stretch or NF-κB inhibitors. ESR1, PTGS2 and OXTR mRNA abundance after 48 h culture was determined using quantitative RT-PCR. Results: Myometrial tissue in culture exhibited culture-induced up-regulation of ESR1 and PTGS2 and down-regulation of OXTR mRNA expression. Progesterone prevented culture-induced increase in ESR1 expression. Estrogen further up-regulated PTGS2 expression. Stretch had no direct effect, but blocked the effects of progesterone and estrogen on ESR1 and PTGS2 expression. cAMP had no effect whereas PMA further up-regulated PTGS2 expression and prevented decline of OXTR expression. Conclusion: Human myometrial tissue in culture undergoes culture-induced gene expression changes consistent with transition toward a laboring phenotype. Changes in ESR1, PTGS2 and OXTR expression could not be controlled simultaneously. Until optimal culture conditions are determined, results of in vitro experiments with myometrial tissues should be interpreted with caution.

Gestational tissue inflammatory biomarkers at term labor: A systematic review of literature

Parturition at term is characterized by inflammatory overload in both feto-maternal tissues. Despite the large number of individual studies on changes in inflammatory biomarkers linked to labor, a comprehensive profile of them in each of the uterine compartments is not available to better understand their mechanistic contributions to labor. This systematic review investigated the pro- and anti-inflammatory biomarkers reported in intra-uterine tissues (amnion, chorion, decidua, placenta, and myometrium) at term labor. We conducted a systematic review of studies on pro- and anti-inflammatory biomarkers (mRNA and/or protein) reported in feto-maternal tissues during normal human term labor, published in English (1980-2016), in 3 electronic data bases. From a total of 3712 citations, 172 were included for final review. Each tissue expresses a unique set of biomarkers at the time of term labor, but there is significant overlap between tissues. All tissues had IL-6, IL-8, IL-1β, COX-2, PGE-2, TNF-α, and hCAP18 in common at term labor. Common and unique inflammatory biomarkers are expressed in various feto-maternal compartments at term labor. Increase in pro-inflammatory markers in all gestational tissue signifies their harmonious functional role in promoting labor. Anti-inflammatory markers at term labor are hardly reported.

Differential impact of acute and prolonged cAMP agonist exposure on protein kinase A activation and human myometrium contractile activity

KEY POINTS

Over 15 million babies are born prematurely each year with approximately 1 million of these babies dying as a direct result of preterm delivery. β₂ -Adrenoreceptor agonists that act via cAMP can reduce uterine contractions to delay preterm labour, but their ability to repress uterine contractions lasts ≤ 48 h and their use does not improve neonatal outcomes. Previous research has suggested that cAMP inhibits myometrial contractions via protein kinase A (PKA) activation, but this has yet to be demonstrated with PKA-specific agonists. We investigated the role of PKA in mediating cAMP-induced human myometrial relaxation, and the impact of prolonged cAMP elevation on myometrial contractility. Our findings suggest that PKA is not the sole mediator of cAMP-induced myometrial relaxation and that prolonged prophylactic elevation of cAMP alone is unlikely to prevent preterm labour (PTL).

ABSTRACT

Acute cAMP elevation inhibits myometrial contractility, but the mechanisms responsible are not fully elucidated and the long-term effects are uncertain. Both need to be defined in pregnant human myometrium before the therapeutic potential of cAMP-elevating agents in the prevention of preterm labour can be realised. In the present study, we tested the hypotheses that PKA activity is necessary for cAMP-induced myometrial relaxation, and that prolonged cAMP elevation can prevent myometrial contractions. Myometrial tissues obtained from term, pre-labour elective Caesarean sections were exposed to receptor-independent cAMP agonists to determine the relationship between myometrial contractility (spontaneous and oxytocin-induced), PKA activity, HSP20 phosphorylation and expression of contraction-associated and cAMP signalling proteins. Acute (1 h) application of cAMP agonists promoted myometrial relaxation, but this was weakly related to PKA activation. A PKA-specific activator, 6-Bnz-cAMP, increased PKA activity (6.8 ± 2.0 mean fold versus vehicle; P = 0.0313) without inducing myometrial relaxation. Spontaneous myometrial contractility declined after 24 h but was less marked when tissues were constantly exposed to cAMP agonists, especially for 8-bromo-cAMP (4.3 ± 1.2 mean fold versus vehicle; P = 0.0043); this was associated with changes to calponin, cofilin and HSP20 phosphorylated/total protein levels. Oxytocin-induced contractions were unaffected by pre-incubation with cAMP agonists despite treatments being able to enhance PKA activity and HSP20 phosphorylation. These data suggest that cAMP-induced myometrial relaxation is not solely dependent on PKA activity and the ability of cAMP agonists to repress myometrial contractility is lost with prolonged exposure. We conclude that cAMP agonist treatment alone may not prevent preterm labour.

Crosstalk between monocytes and myometrial smooth muscle in culture generates synergistic pro-inflammatory cytokine production and enhances myocyte contraction, with effects opposed by progesterone

Both term and preterm parturition are characterized by an influx of macrophages and neutrophils into the myometrium and cervix, with co-incident increased peripheral blood monocyte activation. Infection and inflammation are strongly implicated in the pathology of preterm labour (PTL), with progesterone considered a promising candidate for its prevention or treatment. In this study, we investigated the effect of monocytes on myometrial smooth muscle cell inflammatory cytokine production both alone and in response to LPS, a TLR4 agonist used to trigger PTL in vivo. We also investigated the effect of monocytes on myocyte contraction. Monocytes, isolated from peripheral blood samples from term pregnant women, were cultured alone, or co-cultured with PHM1-41 myometrial smooth muscle cells, for 24 h. In a third set of experiments, PHM1-41 myocytes were cultured for 24 h in isolation. Cytokine secretion was determined by ELISA or multiplex assays. Co-culture of monocytes and myocytes led to synergistic secretion of pro-inflammatory cytokines and chemokines including IL-6, IL-8 and MCP-1, with the secretion being further enhanced by LPS (100 ng/ml). The synergistic secretion of IL-6 and IL-8 from co-cultures was mediated in part by direct cell–cell contact, and by TNF. Conditioned media from co-cultures stimulated contraction of PHM1-41 myocytes, and the effect was inhibited by progesterone. Both progesterone and IL-10 inhibited LPS-stimulated IL-6 and IL-8 secretion from co-cultures, while progesterone also inhibited chemokine secretion. These data suggest that monocytes infiltrating the myometrium at labour participate in crosstalk that potentiates pro-inflammatory cytokine secretion, an effect that is enhanced by LPS, and can augment myocyte contraction. These effects are all partially inhibited by progesterone.

Anti-inflammatory prostaglandins for the prevention of preterm labour

Preterm birth occurs in 10-12% of pregnancies and is the primary cause of neonatal mortality and morbidity. Tocolytic therapies have long been the focus for the prevention of preterm labour, yet they do not significantly improve neonatal outcome. A direct causal link exists between infection-induced inflammation and preterm labour. As inflammation and infection are independent risk factors for poor neonatal outcome, recent research focus has been shifted towards exploring the potential for anti-inflammatory strategies. Nuclear factor kappa B (NFκB) is a transcription factor that controls the expression of many labour-associated genes including PTGS2 (COX2), prostaglandins (PGs) and the oxytocin receptor (OXTR) as well as key inflammatory genes. Targeting the inhibition of NFκB is therefore an attractive therapeutic approach for both the prevention of preterm labour and for reducing neonatal exposure to inflammation. While PGs are considered to be pro-labour and pro-inflammatory, the cyclopentenone PG 15-deoxy-Δ(12,14)PGJ2 (15d-PGJ2) exhibits anti-inflammatory properties via the inhibition of NFκB in human amniocytes, myocytes and peripheral blood mononuclear cells in vitro. 15d-PGJ2 also delays inflammation-induced preterm labour in the mouse and significantly increases pup survival. This review examines the current understanding of inflammation in the context of labour and discusses how anti-inflammatory PGs may hold promise for the prevention of preterm labour and improved neonatal outcome.

Epigenetics of human myometrium: DNA methylation of genes encoding contraction-associated proteins in term and preterm labor

Preterm birth involves the interaction of societal and environmental factors potentially modulating the length of gestation via the epigenome. An established form of epigenetic regulation is DNA methylation where promoter hypermethylation is associated with gene repression. We hypothesized we would find differences in DNA methylation in the myometrium of women with preterm labor of different phenotypes versus normal term labor. Myometrial tissue was obtained at cesarean section at term with or without labor, preterm without labor, idiopathic preterm labor, and twin gestations with labor. Genomic DNA was isolated, and samples in each group were combined and analyzed on a NimbleGen 2.1M human DNA methylation array. Differences in methylation from -8 to +3 kb of transcription start sites of 22 contraction-associated genes were determined. Cytosine methylation was not present in CpG islands of any gene but was present outside of CpG islands in shores and shelves in 19 genes. No differential methylation was found across the tissue groups for six genes (PTGES3L, PTGER2, PTGER4, PTGFRN, ESR2, and GJA1). For 13 genes, differential methylation occurred in several patterns between tissue groups. We find a correlation between hypomethylation and increased mRNA expression of PTGES/mPGES-1, indicating potential functional relevance of methylation, but no such correlation for PTGS2/COX-2, suggesting other regulatory mechanisms for PTGS2 at labor. The majority of differential DNA methylation of myometrial contraction-associated genes with different labor phenotypes occurs outside of CpG islands in gene promoters, suggesting that the entirety of DNA methylation across the genome should be considered.

Effect of propofol on prostaglandin E2 production and prostaglandin synthase-2 and cyclooxygenase-2 expressions in amniotic membrane cells

PURPOSE

Surgery during pregnancy can be a cause of preterm labor or birth, possibly resulting from anesthetic agents or direct effects of surgery. This study was aimed to investigate the effect of propofol on uterine contractility by examining prostaglandin E2 (PGE2) production and the expression of PGE synthase 2 (PGES2) and cyclooxygenase-2 (COX-2) in amniotic membrane cells.

METHODS

Amniotic membranes were collected from healthy full-term women who underwent cesarean section at 37-40 weeks of gestation. The amniotic cells were cultured in α-modified-Eagle's medium with 10% fetal bovine serum for 24 h at 5% CO2 in a 37 °C incubator. Then, various doses of propofol (0.01-10 μg/ml) were used for treatment for 3 h. PGE2 concentrations in conditioned media were evaluated using ELISA. PGES2 and COX-2 expression were examined using RT-PCR and Western blot. Cell viability and apoptosis were examined by MTT, ATP assays, and the TUNEL method.

RESULTS

PGE2 production significantly decreased at 0.1 and 1.0 μg/ml propofol concentrations compared to controls. COX-2 and PGES2 mRNA expression was decreased in a dose-dependent manner with a significant difference at 0.1 μg/ml propofol compared to controls. The protein expression of COX-2 showed a similar result to mRNA expression, but protein expression of PGES2 was not significantly decreased. No effect of propofol was found in cell viability.

CONCLUSIONS

This study showed that propofol reduced the production of PGE2 and the expression of COX-2 and PGES2 without affecting cell viability.

Effects of PGF2α on the expression of uterine activation proteins in pregnant human myometrial cells from upper and lower segment

CONTEXT

The lower and upper segments of the uterus may play different roles in the process of parturition. The switch from pregnancy to delivery involves changes in expression of uterine activation proteins (UAPs). Prostaglandin (PG) F2α has multiple and complex roles in the birth process in addition to its vital contractile role.

OBJECTIVE

The purpose of this study was to investigate whether PGF2α regulates the expression of UAPs in human myometrium and to compare PGF2α actions in lower and upper segments.

DESIGN

Cultured human myometrial cells from upper and lower segments were treated with PGF2α. Western blotting was used to determine the levels of connexin 43 (CX-43), prostaglandin endoperoxide synthase-2 (PTGS-2; cyclooxygenase-2), oxytocin receptor (OTR), and PGF2α receptor (PTGFR) in the cells. The small interfering RNA approach was used to knock down PTGFR.

RESULTS

PGF2α dose dependently increased CX-43 and PTGS-2 while decreasing PTGFR in upper and lower segments. PGF2α increased OTR in the lower segment while decreasing it in the upper segment. PGF2α lost its effects on PTGS-2 and OTR in PTGFR knockdown cells, but its effect on CX-43 remained. AL8810, a specific antagonist of PTGFR, reversed the actions of PGF2α on UAPs except for CX-43 in the lower segment. Indomethacin reversed the PGF2α-induced effects on CX-43 and PTGS-2, but it did not alter PGF2α-induced PTGFR and OTR expression. The stimulatory effects of PGF2α were enhanced in the presence of IL-1β, which reversed the inhibitory effect of PGF2α on PTGFR.

CONCLUSION

PGF2α regulates UAPs in both upper and lower segment cells through either direct or indirect pathways, indicating that PGF2α uniquely participates in uterine preparation for the onset of labor.

Prostaglandin E2 represses interleukin 1 beta-induced inflammatory mediator output from pregnant human myometrial cells through the EP2 and EP4 receptors

Inflammatory mediators, including prostaglandins, cytokines, and chemokines, are strongly implicated in the mechanism of human labor, though their precise roles remain unknown. Here we demonstrate that interleukin 1 beta (IL-1beta) significantly increased the expression and release of interleukin-8 (CXCL8), monocyte chemotactic protein-1 (CCL2), and granulocyte macrophage colony-stimulating factor (CSF2) by primary human myometrial cells. However, this effect was repressed by prostaglandin E(2) (PGE(2)). As PGE(2) can activate four distinct PGE(2) receptors (EP(1), EP(2), EP(3), and EP(4)) to elicit various responses, we sought to define the EP receptor(s) responsible for this repression. Using selective EP receptor agonists and a selective EP(4) antagonist, we show that PGE(2) mediates the repression of IL-1beta-induced release of CXCL8, CCL2, and CSF2 via activation of the EP(2) and EP(4) receptors. The use of siRNA gene-specific knockdown further confirmed a role for both receptors. Real-time RT-PCR demonstrated that EP(2) was the most highly expressed of all four EP receptors at the mRNA level in human myometrial cells, and immunocytochemistry showed that EP(2) protein is abundantly present throughout the cells. Interestingly, PGE(2) does not appear to reduce mRNA expression of CXCL8, CCL2, and CSF2. Our results demonstrate that PGE(2) can elicit anti-inflammatory responses via activation of the EP(2) and EP(4) receptors in lower segment term pregnant human myometrial cells. Further elucidation of the EP receptor-mediated signaling pathways in the pregnant human uterus may be beneficial for optimizing the maintenance of pregnancy, induction of labor or indeed treatment of preterm labor.

Expression of cystathionine β-synthase and cystathionine γ-lyase in human pregnant myometrium and their roles in the control of uterine contractility

Background

Human uterus undergoes distinct molecular and functional changes during pregnancy and parturition. Hydrogen sulfide (H₂S) has recently been shown to play a key role in the control of smooth muscle tension. The role of endogenous H₂S produced locally in the control of uterine contractility during labour is unknown.

Methodology/Principal Findings

Human myometrium biopsies were obtained from pregnant women undergoing cesarean section at term. Immunohistochemistry analysis showed that cystathionine-γ-lyase (CSE) and cystathionine-β-synthetase (CBS), the principle enzymes responsible for H₂S generation, were mainly localized to smooth muscle cells of human pregnant myometrium. The mRNA and protein expression of CBS as well as H₂S production rate were down-regulated in labouring tissues compared to nonlabouring tissues. Cumulative administration of L-cysteine (10⁻⁷–10⁻² mol/L), a precursor of H₂S, caused a dose-dependent decrease in the amplitude of spontaneous contractions in nonlabouring and labouring myometrium strips. L-cysteine at high concentration (10⁻³ mol/L) increased the frequency of spontaneous contractions and induced tonic contraction. These effects of L-cysteine were blocked by the inhibitors of CBS and CSE. Pre-treatment of myometrium strips with glibenclamide, an inhibitor of ATP-sensitive potassium (K_ATP) channels, abolished the inhibitory effect of L-cysteine on spontaneous contraction amplitude. The effects of L-cysteine on the amplitude of spontaneous contractions and baseline muscle tone were less potent in labouring tissues than that in nonlabouring strips.

Conclusion/Significance

H₂S generated by CSE and CBS locally exerts dual effects on the contractility of pregnant myometrium. Expression of H₂S synthetic enzymes is down-regulated during labour, suggesting that H₂S is one of the factors involved in the transition of pregnant uterus from quiescence to contractile state after onset of parturition.

The Influence of Interleukin (IL)-1β and IL-6 and Tumour Necrosis Factor-α on Prostaglandin Secretion from Porcine Myometrium during the First Third of Pregnancy

The present study was undertaken to determine the effect of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) on prostaglandin (PG)F2α and PGE2 secretion as well as cyclooxygenase-2 (COX-2) protein expression in myometrium collected on days 25, 30 and 40 of pregnancy in pigs. Myometrial slices were incubated for 16 h with IL-1β, IL-6 and TNF-α (1 or 10 ng/ml of medium) or two combinations of the three cytokines (1 or 10 ng/ml of each cytokine per combination). We demonstrated the stimulatory effect of IL-1β and IL-6 on PGF2α and PGE2 secretion from myometrium collected on all examined days of pregnancy, excepting of influence of IL-6 on release of PGF2α by tissue from day 30. In turn, TNF-α was able to stimulate only PGE2 secretion by myometrium of 40-day-pregnant gilts. The three cytokines applied in combination augmented release of PGE2 from myometrium collected on days 30 and 40 of pregnancy. Stimulation of PGE2 secretion by cytokines used individually was more frequent than that of PGF2α. Moreover, an enhancement in PGF2α and/or PGE2 release was accompanied by an increase of COX-2 protein expression. Our study shows the ability of cytokines to stimulate PGF2α and PGE2 release by porcine myometrium from the first third of pregnancy. Obtained data suggest that locally PGs produced in myometrium influencing the uterine contraction activity may be important for the maintenance of myometrial quiescence during pregnancy and confirm also that the complex cytokine network is an important regulatory mechanism of PGs production during pregnancy.

A molecular signature of an arrest of descent in human parturition

OBJECTIVE

This study was undertaken to identify the molecular basis of an arrest of descent.

STUDY DESIGN

Human myometrium was obtained from women in term labor (TL; n = 29) and arrest of descent (AODes; n = 21). Gene expression was characterized using Illumina HumanHT-12 microarrays. A moderated Student t test and false discovery rate adjustment were applied for analysis. Confirmatory quantitative reverse transcription-polymerase chain reaction and immunoblot were performed in an independent sample set.

RESULTS

Four hundred genes were differentially expressed between women with an AODes compared with those with TL. Gene Ontology analysis indicated enrichment of biological processes and molecular functions related to inflammation and muscle function. Impacted pathways included inflammation and the actin cytoskeleton. Overexpression of hypoxia inducible factor-1a, interleukin -6, and prostaglandin-endoperoxide synthase 2 in AODes was confirmed.

CONCLUSION

We have identified a stereotypic pattern of gene expression in the myometrium of women with an arrest of descent. This represents the first study examining the molecular basis of an arrest of descent using a genome-wide approach.

Characterization of the myometrial transcriptome and biological pathways of spontaneous human labor at term

AIMS

to characterize the transcriptome of human myometrium during spontaneous labor at term.

METHODS

myometrium was obtained from women with (n=19) and without labor (n=20). Illumina HumanHT-12 microarrays were utilized. Moderated t-tests and false discovery rate adjustment of P-values were applied. Real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was performed for a select set of differentially expressed genes in a separate set of samples. Enzyme-linked immunosorbent assay and Western blot were utilized to confirm differential protein production in a third sample set.

RESULTS

1) Four hundred and seventy-one genes were differentially expressed; 2) gene ontology analysis indicated enrichment of 103 biological processes and 18 molecular functions including: a) inflammatory response; b) cytokine activity; and c) chemokine activity; 3) systems biology pathway analysis using signaling pathway impact analysis indicated six significant pathways: a) cytokine-cytokine receptor interaction; b) Jak-STAT signaling; and c) complement and coagulation cascades; d) NOD-like receptor signaling pathway; e) systemic lupus erythematosus; and f) chemokine signaling pathway; 4) qRT-PCR confirmed over-expression of prostaglandin-endoperoxide synthase-2, heparin binding epidermal growth factor (EGF)-like growth factor, chemokine C-C motif ligand 2 (CCL2/MCP1), leukocyte immunoglobulin-like receptor, subfamily A member 5, interleukin (IL)-8, IL-6, chemokine C-X-C motif ligand 6 (CXCL6/GCP2), nuclear factor of kappa light chain gene enhancer in B-cells inhibitor zeta, suppressor of cytokine signaling 3 (SOCS3) and decreased expression of FK506 binding-protein 5 and aldehyde dehydrogenase in labor; 5) IL-6, CXCL6, CCL2 and SOCS3 protein expression was significantly higher in the term labor group compared to the term not in labor group.

CONCLUSIONS

myometrium of women in spontaneous labor at term is characterized by a stereotypic gene expression pattern consistent with over-expression of the inflammatory response and leukocyte chemotaxis. Differential gene expression identified with microarray was confirmed with qRT-PCR using an independent set of samples. This study represents an unbiased description of the biological processes involved in spontaneous labor at term based on transcriptomics.

Genes for prostaglandin synthesis, transport and inactivation are differentially expressed in human uterine tissues, and the prostaglandin F synthase AKR1B1 is induced in myometrial cells by inflammatory cytokines

Prostaglandins (PGs) are important factors in the physiology of human parturition and the control of uterine contractility. We have characterized the expression of 15 genes from all stages of the PG pathway in human pregnant and non-pregnant (NP) myometrium and in other uterine tissues at delivery, and the results show patterns indicative of different capacities for PG synthesis and catabolism in each tissue. In placenta, the PG synthase expression profile favours production of PGD₂, PGE₂ and PGF₂, with high levels of PG transporters and catabolic PG dehydrogenase suggesting rapid PG turnover. Choriodecidua is primed for PGE₂, PGF₂ and PGD₂ production and high PG turnover, whereas amnion expresses genes for PGE₂ synthesis with low levels of PG transporters and dehydrogenase. In umbilical cord, PGI₂ synthase is highly expressed. In pregnant myometrium, PGI₂, PGD₂ and PGF₂ synthases are highly expressed, whereas PG dehydrogenase is underexpressed. Myometrium from women with spontaneous or induced labour had higher expression of the PGH₂ synthase PTGS2 than tissue from women not-in-labour. Myometrium from NP women had lower levels of PG synthases and higher levels of PG dehydrogenase than pregnant myometrium. Discriminant function analysis showed that expression of selected genes in myometrium could distinguish groups of women with different modes of labour from each other and from NP women. In cultured myometrial cells, there was a dose-dependent stimulatory effect of interleukin 1β and tumour necrosis factor α on PTGS2, PTGES and AKR1B1 (PGF synthase) expression.

Labour is associated with decreased expression of the PGF2alpha receptor (PTGFR) and a novel PTGFR splice variant in human myometrium but not decidua

The prostaglandin F(2α) receptor (PTGFR) is believed to play a role in the process of parturition. The main support for this comes from animal studies; however, in humans, the evidence is less clear. The gene coding for PTGFR may be subject to alternative splicing to generate alternate variants with different signalling pathways. We have determined regional (upper versus lower segment) and labour-associated expression of PTGFR mRNA and a recently identified splice variant of PTGFR in human myometrium and decidua. We also examined the effect of the inflammatory cytokine interleukin-1β (IL-1β) on PTGFR mRNA expression in a model of cultured human myometrial smooth muscle cells. We identified a PTGFR transcript variant 2 (PTGFR-v2) generated by alternate splicing in human myometrium and decidua. The PTGFR-v2 contains an additional 71 base pair exon, which results in a truncated protein at 297 amino acids compared with the PTGFR transcript variant 1 (PTGFR-v1) at 359 amino acids. In contrast to our hypothesis, we demonstrate that PTGFR-v1 and PTGFR-v2 mRNA expression is not significantly higher in upper segment compared with lower segment paired samples. We also show a labour-associated decrease in PTGFR-v1 and PTGFR-v2 mRNA expression in lower segment myometrial samples. IL-1β-stimulated mRNA expression of both PTGFR variants in a distinct time-dependent manner in myometrial cell cultures. We suggest that the role of the PTGFR in the human uterus requires further validation prior to pursuing it as a target for the treatment of preterm labour. In addition, the presence of distinct variants suggests further levels of gene regulation within the pregnant uterus.

Lipidomic analysis reveals prostanoid profiles in human term pregnant myometrium

Prostanoids modulate the activity of human pregnant myometrium and their functional role can be appreciated through characterisation of prostanoid receptors and tissue concentration of prostanoids. We have applied a lipidomic approach to elucidate the profile of prostanoids in human non-labouring and labouring myometrium. We have identified a total of nineteen prostanoids including prostacyclin, thromboxanes, prostaglandins and dihydro-prostaglandins. Prostacyclin was the predominant prostanoid in both non-labouring and labouring myometria, with PGD(2) and PGF(2alpha) being the second most abundant. Although the total amount of prostanoids was increased in the labouring tissue, PGE(2) and 13,14-dihydro-15-keto-PGE(2) were the only prostanoids to increase significantly at early and late labour (p< or =0.001). Our data suggest that PGF(2alpha) plays an important role in parturition, whilst the increase in PGE(2) could occur to facilitate cervical dilation and relaxation of the lower myometrium during labour. Although the elevation in TXA(2) was less marked than expected, in terms of translation to function even a relatively small increase in the level of this potent spasmogen may have significant effects.

Pro-labour myometrial gene expression: are preterm labour and term labour the same?

Preterm labour (PTL) is the most important cause of neonatal morbidity and mortality. While some causes have been identified, the mechanisms involved remain elusive. This study investigates whether term labour (TL) is an appropriate model for PTL by examining pro-labour gene expression, using quantitative rtPCR, and protein synthesis, using Western analysis, in preterm and term myometrial samples obtained from the upper and lower uterine segments before and after the onset of labour. In the lower segment, the levels of prostaglandin H synthase type-2 (PGHS-2), interleukin-1beta (IL-1beta), IL-6 and IL-8 mRNA expression were significantly higher in TL compared with PTL samples. Compared with non-labour controls, the expression of IL-1beta and IL-8 mRNA was increased in both PTL and TL samples and the expression of PGHS-2 and IL-6 mRNA was increased in TL samples only. In the upper segment, there were no differences between PTL and TL samples and the mRNA expression of PGHS-2 and IL-1beta was increased in TL compared with term no labour samples. No effect of PTL or TL was seen on either oxytocin receptor or connexin-43 mRNA expression or protein levels. The multiple regression analysis and studies in primary cultures of uterine myocytes suggest that the inflammatory cytokines, IL-1beta and tumour necrosis factor-alpha, are the most important regulators of PGHS-2 and IL-8. Our data show that preterm and term labouring myometrium are significantly different and that the most marked labour-induced changes in gene expression are in the lower segment. These changes may occur in response to the release of inflammatory cytokines by the labour-associated inflammatory infiltration.

The effect of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta and IL-6 on chorioamnion secretion of prostaglandins (PG)F 2 alpha and E2 in pigs

The aim of the present study was to determine the effect of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) on prostaglandin (PG)F(2 alpha) and PGE(2) secretion as well as cyclooxygenase-2 (COX-2) protein expression in chorioamnion collected on days 25, 30 and 40 of pregnancy in pigs. Fetal membrane slices were incubated for 16 h with TNF-alpha, IL-1 beta, IL-6 (1 or 10 ng/ml of medium) or two combinations of the three cytokines (1 or 10 ng/ml of each cytokine per combination). We demonstrated the stimulatory effect of TNF-alpha, IL-1 beta and/or IL-6 on PGF(2 alpha) and PGE(2) secretion by the porcine fetal membranes. The medium content of these PGs depended on the cytokine type, treatment dose and day of pregnancy. Cytokine stimulation of PGE(2) was more pronounced than that of PGF(2 alpha). In addition, an increase in PGF(2 alpha) and/or PGE(2) secretion was usually associated with an augmentation of COX-2 protein expression. Our results support the notion concerning the possible role of cytokines in modulating production of PGs by fetal membranes during the first trimester of gestation.

Expression of genes involved in prostaglandin E2 and progesterone production in bovine cumulus–oocyte complexes during in vitro maturation and fertilization

Prostaglandin E2(PGE2) and progesterone appear to be critical mediators of cumulus expansion and the resumption of oocyte meiosis. The aim of this study was to identify the types of prostaglandin E synthase (PTGES) expressed in the bovine cumulus–oocyte complex (COC), to characterize their temporal expression during the periconceptional interval using anin vitromodel of maturation (IVM) and fertilization (IVF), and to compare their expression with the level of steroidogenic gene expression. Real-time RT-PCR analysis revealed that enzymes related to the PGE2biosynthesis pathway were mainly expressed during IVM. Transcripts encoding PTGES1–3 were detected in bovine COCs. Only the expression of PTGES1 significantly increased during IVM whereas that of PTGES2 and PTGES3 remained unchanged. The induction of PTGES1 expression paralleled the induction of prostaglandin G/H synthase-2 (PTGS2) expression and the amounts of PGE2secreted by maturing COCs. Concomitantly, cholesterol side chain cleavage cytochrome P450 expression was significantly upregulated in maturing COCs and the high level of expression persisted in fertilized COCs. The expression of the StAR protein remained constant during IVM and then decreased significantly during IVF. Expression of the progesterone catabolic-related enzyme, 20α-hydroxysteroid dehydrogenase significantly decreased throughout the periconceptional interval. This was associated with a rising level of progesterone released by COCs in the culture media. In conclusion, our results suggest that the periconceptional differentiation of the bovine COC includes the transient induction of PGE2biosynthetic activity via the PTGS2/PTGES1 pathway during the maturation period and the increasing ability to produce progesterone from the immature to the fertilized stages.