Human myometrial gene expression before and during parturition

Prostaglandin E2 regulates its own inactivating enzyme, 15-PGDH, by EP2 receptor-mediated cervical cell-specific mechanisms

CONTEXT

Prostaglandins play important roles in parturition and have been used to induce cervical ripening and labor. Prior to cervical ripening at term, 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is highly expressed in the cervix and metabolizes cyclooxygenase-2-mediated increases in active prostaglandin E2 (PGE2) to inactive 15-keto PGE2. At term, 15-PGDH gene expression decreases and PGE2 accumulates, leading to cervical ripening and labor. Previously, we found that the cervical isoform of microphthalmia-associated transcription factor (MiTF-CX) serves as a progestational transcription factor that represses IL-8 and hypoxia-mediated increases in cyclooxygenase-2.

OBJECTIVE

We tested the hypothesis that PGE2 regulates its own inactivation through MiTF-CX.

DESIGN

We used human cervical stromal cells to investigate the regulation of 15-PGDH.

SETTING

This was a laboratory-based study using cells from clinical tissue samples.

MAIN OUTCOME MEASURES

We evaluated the mechanisms by which PGE2 regulates 15-PGDH in human cervical stromal cells.

RESULTS

PGE2 repressed MiTF-CX and 15-PGDH, whereas ectopic overexpression of MiTF-CX induced 15-PGDH expression levels. Stabilization of HIF-1α by deferoxamine resulted in concomitant down-regulation of MiTF-CX and 15-PGDH. Ectopic overexpression of MiTF-CX abrogated PGE2- and deferoxamine-mediated loss of MiTF-CX and 15-PGDH. PGE2-induced loss of MiTF-CX and 15-PGDH was mediated through prostaglandin E2 receptor (EP2) receptors (PTGER2), but not cAMP.

CONCLUSIONS

The 15-PGDH gene is a MiTF-CX target gene in cervical stromal cells and is down-regulated by PGE2 through EP2 receptors. The findings suggest that EP2 receptor-specific antagonists may be used as an adjunct to present clinical management for the prevention of preterm cervical ripening and preterm labor.

Transcriptome interrogation of human myometrium identifies differentially expressed sense-antisense pairs of protein-coding and long non-coding RNA genes in spontaneous labor at term

OBJECTIVE

To identify differentially expressed long non-coding RNA (lncRNA) genes in human myometrium in women with spontaneous labor at term.

MATERIALS AND METHODS

Myometrium was obtained from women undergoing cesarean deliveries who were not in labor (n = 19) and women in spontaneous labor at term (n = 20). RNA was extracted and profiled using an Illumina® microarray platform. We have used computational approaches to bound the extent of long non-coding RNA representation on this platform, and to identify co-differentially expressed and correlated pairs of long non-coding RNA genes and protein-coding genes sharing the same genomic loci.

RESULTS

We identified co-differential expression and correlation at two genomic loci that contain coding-lncRNA gene pairs: SOCS2-AK054607 and LMCD1-NR_024065 in women in spontaneous labor at term. This co-differential expression and correlation was validated by qRT-PCR, an experimental method completely independent of the microarray analysis. Intriguingly, one of the two lncRNA genes differentially expressed in term labor had a key genomic structure element, a splice site, that lacked evolutionary conservation beyond primates.

CONCLUSIONS

We provide, for the first time, evidence for coordinated differential expression and correlation of cis-encoded antisense lncRNAs and protein-coding genes with known as well as novel roles in pregnancy in the myometrium of women in spontaneous labor at term.

Neuroendocrinology of pregnancy and parturition

During pregnancy, the maternal brain drives a series of adaptive mechanisms that are fundamental for allowing fetal growth and development, protecting both mother and fetus from adverse programming and timing of parturition. This neuroendocrine concept is even more complex as fetal brain and placenta also participate as regulators of maternal-placental-fetal physiology. The placenta is now seen as a neuroendocrine organ, acting as a source of several neuroactive factors that may exert their biologic effects either locally or by entering maternal and fetal circulation, thus acting in an autocrine, paracrine, and endocrine manner. A variety of hypothalamic neurohormones (GnRH, GHRH, somatostatin, CRH, oxytocin) are expressed in the placenta. When stress occurs during pregnancy, the maternal, fetal, and placental hypothalamic-pituitary-adrenal (HPA) axes are activated to stimulate a series of responses contributing to maintain physiologic conditions while at the same time avoiding the adverse effects of stress on the mother and offspring. However, when stress is excessive, a number of obstetric complications may occur, such as preterm birth, pre-eclampsia and intrauterine growth restriction, related to an impairment of the placental adaptive response.

Assessment of myometrial transcriptome changes associated with spontaneous human labour by high-throughput RNA-seq

The transition of the human uterus from a quiescent to a contractile state takes place over a number of weeks. On such biological time scales, cellular phenotype is modified by changes in the transcriptome, which in turn is under the control of the underlying endocrine, paracrine, and biophysical processes resulting from the ongoing pregnancy. In this study, we characterize the transition of the human myometrial transcriptome at term from not in labour (NIL) to in labour (LAB) using high throughput RNA sequencing (RNA-seq). RNA was isolated from the myometrium of uterine biopsies from patients at term who were not in labour (n = 5) and at term in spontaneous labour (n = 5) without augmentation. A total of 143.6 million separate reads were sequenced, achieving, on average, ∼13 times coverage of the expressed human transcriptome per sample. Principal component analysis indicated that the NIL and LAB transcriptomes could be distinguished as two distinct clusters. A comparison of the NIL and LAB groups, using three different statistical approaches (baySeq, edgeR, and DESeq), demonstrated an overlap of 764 differentially expressed genes. A comparison with currently available microarray data revealed only a partial overlap in differentially expressed genes. We conclude that the described RNA-seq data sets represent the first fully annotated catalogue of expressed mRNAs in human myometrium. When considered together, the full expression repertoire and the differentially expressed gene sets should provide an excellent resource for formulating new hypotheses of physiological function, as well as the discovery of novel therapeutic targets.

Characterization of the myometrial transcriptome in women with an arrest of dilatation during labor

OBJECTIVE

The molecular basis of failure to progress in labor is poorly understood. This study was undertaken to characterize the myometrial transcriptome of patients with an arrest of dilatation (AODIL).

STUDY DESIGN

Human myometrium was prospectively collected from women in the following groups: (1) spontaneous term labor (TL; n=29) and (2) arrest of dilatation (AODIL; n=14). Gene expression was characterized using Illumina® HumanHT-12 microarrays. A moderated Student's t-test and false discovery rate adjustment were used for analysis. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) of selected genes was performed in an independent sample set. Pathway analysis was performed on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database using Pathway Analysis with Down-weighting of Overlapping Genes (PADOG). The MetaCore knowledge base was also searched for pathway analysis.

RESULTS

(1) Forty-two differentially expressed genes were identified in women with an AODIL; (2) gene ontology analysis indicated enrichment of biological processes, which included regulation of angiogenesis, response to hypoxia, inflammatory response, and chemokine-mediated signaling pathway. Enriched molecular functions included transcription repressor activity, heat shock protein (Hsp) 90 binding, and nitric oxide synthase (NOS) activity; (3) MetaCore analysis identified immune response chemokine (C-C motif) ligand 2 (CCL2) signaling, muscle contraction regulation of endothelial nitric oxide synthase (eNOS) activity in endothelial cells, and triiodothyronine and thyroxine signaling as significantly overrepresented (false discovery rate <0.05); (4) qRT-PCR confirmed the overexpression of Nitric oxide synthase 3 (NOS3); hypoxic ischemic factor 1A (HIF1A); Chemokine (C-C motif) ligand 2 (CCL2); angiopoietin-like 4 (ANGPTL4); ADAM metallopeptidase with thrombospondin type 1, motif 9 (ADAMTS9); G protein-coupled receptor 4 (GPR4); metallothionein 1A (MT1A); MT2A; and selectin E (SELE) in an AODIL.

CONCLUSION

The myometrium of women with AODIL has a stereotypic transcriptome profile. This disorder has been associated with a pattern of gene expression involved in muscle contraction, an inflammatory response, and hypoxia. This is the first comprehensive and unbiased examination of the molecular basis of an AODIL.

Promoter RNA links transcriptional regulation of inflammatory pathway genes

Although many long non-coding RNAs (lncRNAs) have been discovered, their function and their association with RNAi factors in the nucleus have remained obscure. Here, we identify RNA transcripts that overlap the cyclooxygenase-2 (COX-2) promoter and contain two adjacent binding sites for an endogenous miRNA, miR-589. We find that miR-589 binds the promoter RNA and activates COX-2 transcription. In addition to miR-589, fully complementary duplex RNAs that target the COX-2 promoter transcript activate COX-2 transcription. Activation by small RNA requires RNAi factors argonaute-2 (AGO2) and GW182, but does not require AGO2-mediated cleavage of the promoter RNA. Instead, the promoter RNA functions as a scaffold. Binding of AGO2 protein/small RNA complexes to the promoter RNA triggers gene activation. Gene looping allows interactions between the promoters of COX-2 and phospholipase A2 (PLA2G4A), an adjacent pro-inflammatory pathway gene that produces arachidonic acid, the substrate for COX-2 protein. miR-589 and fully complementary small RNAs regulate both COX-2 and PLA2G4A gene expression, revealing an unexpected connection between key steps of the eicosanoid signaling pathway. The work demonstrates the potential for RNA to coordinate locus-dependent assembly of related genes to form functional operons through cis-looping.

Corticotropin-releasing hormone interacts with interleukin-1β to regulate prostaglandin H synthase-2 expression in human myometrium during pregnancy and labor

CONTEXT

The onset of labor appears to involve the activation of myometrial inflammatory pathways, and transcription factors such as nuclear factor-κB (NF-κB) control expression of the contraction-associated proteins required to induce a procontractile phenotype. These responses might involve CRH, which integrates immune and neuroendocrine systems.

OBJECTIVES

In human myometrium we investigated cyclooxygenase 2 (PGHS2) expression and regulation by CRH and the proinflammatory cytokine IL-1β before and after labor.

DESIGN

Myometrial tissues obtained from pregnant women at term before (n = 12) or during labor (n = 10) and pathological cases of choriamnionitis-associated term labor (n = 5) were used to isolate primary myocytes and investigate in vitro, CRH effects on basal and IL-1β regulated p65 activation and PGHS2 expression.

RESULTS

In nonlaboring myometrial cells, CRH was unable to induce NF-κB nuclear translocation; however, it altered the temporal dynamics of IL-1β-driven NF-κB nuclear entry by initially delaying entry and subsequently prolonging retention. These CRH-R1-driven effects were associated with a modest inhibitory action in the early phase (within 2 hours) of IL-1β stimulated PGHS2 mRNA expression, whereas prolonged stimulation for 6-18 hours augmented the IL-1β effects. The early-phase effect required intact protein kinase A activity and was diminished after the onset of labor. The presence of chorioamnionitis led to exaggerated PGHS2 mRNA responses to IL-1β but diminished effects of CRH.

CONCLUSIONS

CRH is involved in the inflammatory regulation of PGHS2 expression before and during labor; these actions might be important in priming and preparing the myometrium for labor and cellular adaptive responses to inflammatory mediators.

MicroRNAs--mediators of myometrial contractility during pregnancy and labour

The maintenance of myometrial quiescence and initiation of contractility, which lead to parturition at term and preterm, involve a shifting equilibrium between anti-inflammatory and proinflammatory signalling pathways. Progesterone (P4), acting through the progesterone receptor (PR), has an essential and multifaceted role in the maintenance of myometrial quiescence. This effect of P4-PR signalling is mediated, in part, by its anti-inflammatory actions and capacity to repress the expression of genes that encode proinflammatory cytokines, such as IL-1 and IL-6, and contraction-associated proteins, such as OXTR, GJA1 and PTGS2. By contrast, increased expression of genes that ultimately lead to parturition is mediated by enhanced inflammatory and estradiol-17β (E2) and estrogen receptor α signalling, which reduce PR function, thus further intensifying the inflammatory response. To obtain a more complete understanding of the molecular events that underlie the transition of the pregnant myometrium from a refractory to a contractile state, the roles of microRNAs, their targets, and their transcriptional and hormonal regulation have been investigated. This article reviews the actions of the miR-200 family and their P4-regulated targets-the transcription factors ZEB1, ZEB2 and STAT5B-in the pregnant myometrium, as well as the role of miR-199a-3p and miR-214 and their mutual target PTGS2. The central role of ZEB1 as the mediator of the opposing actions of P4 and E2 on myometrial contractility will be highlighted.

The influence of maternal body mass index on myometrial oxytocin receptor expression in pregnancy

Obese pregnant women have higher rates of dysfunctional labor patterns, need for oxytocin augmentation, labor induction, postdates pregnancy, and cesarean delivery compared to normal weight pregnant women. We tested the hypothesis that myometrial oxytocin receptor (OXTR) gene and protein expression are affected by obesity in pregnancy. Myometrial samples were obtained at the time of cesarean delivery from the upper aspect of the uterine hysterotomy incision and processed for real-time quantitative polymerase chain reaction and Western blot. There were 63 myometrial samples available for analysis. The median body mass index (BMI) at delivery was 31.0 kg/m(2) (interquartile range, 26.0, 40.0 kg/m(2)), and the median gestational age at delivery was 38.0 weeks (interquartile range, 33.0, 39.1 weeks). The OXTR gene expression did not correlate with maternal BMI at delivery by linear regression, and the median OXTR gene expression did not differ between women with a BMI ≤ 30 kg/m(2) and those with a BMI ≥ 40 kg/m(2). The OXTR protein expression was also not affected by maternal BMI. Myometrial OXTR gene expression appears to be independent of BMI at the time of delivery. Dysfunctional labor patterns and increased oxytocin utilization seen in obese women may not be due to differences in OXTR expression, though functional studies are required.

Influence of energy balance on the antimicrobial peptides S100A8 and S100A9 in the endometrium of the post-partum dairy cow

Uterine inflammation occurs after calving in association with extensive endometrial remodelling and bacterial contamination. If the inflammation persists, it leads to reduced fertility. Chronic endometritis is highly prevalent in high-yielding cows that experience negative energy balance (NEB) in early lactation. This study investigated the effect of NEB on the antimicrobial peptides S100A8 and S100A9 in involuting uteri collected 2 weeks post partum. Holstein-Friesian cows (six per treatment) were randomly allocated to two interventions designed to produce mild or severe NEB (MNEB and SNEB) status. Endometrial samples were examined histologically, and the presence of neutrophils, macrophages, lymphocytes and natural killer cells was confirmed using haematoxylin and eosin and immunostaining. SNEB cows had greater signs of uterine inflammation. Samples of previously gravid uterine horn were used to localise S100A8 and S100A9 by immunohistochemistry. Both S100 proteins were present in bovine endometrium with strong staining in epithelial and stromal cells and in infiltrated leucocytes. Immunostaining was significantly higher in SNEB cows along with increased numbers of segmented neutrophils. These results suggest that the metabolic changes of a post-partum cow suffering from NEB delay uterine involution and promote a chronic state of inflammation. We show that upregulation of S100A8 and S100A9 is clearly a key component of the early endometrial response to uterine infection. Further studies are warranted to link the extent of this response after calving to the likelihood of cows developing endometritis and to their subsequent fertility.

The impact of reference gene selection in quantification of gene expression levels in guinea pig cervical tissues and cells

BACKGROUND

Accurate measurements of mRNA expression levels in tissues or cells are crucially dependent on the use of relevant reference genes for normalization of data. In this study we used quantitative real-time PCR and two Excel-based applets (geNorm and BestKeeper) to determine the best reference genes for quantification of target gene mRNA in a complex tissue organ such as the guinea pig cervix.

RESULTS

Gene expression studies were conducted in cervical epithelium and stroma during pregnancy and parturition and in cultures of primary cells from this tissue. Among 15 reference gene candidates examined, both geNorm and BestKeeper found CLF1 and CLTC to be the most stable in cervical stroma and cervical epithelium, ACTB and PPIB in primary stroma cells, and CLTC and PPIB in primary epithelial cells. The order of stability among the remaining candidate genes was not in such an agreement. Commonly used reference such as GAPDH and B2M demonstrated lower stability. Determination of pairwise variation values for reference gene combinations using geNorm revealed that the geometric mean of the two most stable genes provides sufficient normalization in most cases. However, for cervical stroma tissue in which many reference gene candidates displayed low stability, inclusion of three reference genes in the geometric mean may improve accuracy of target gene expression level analyses. Using the top ranked reference genes we examined the expression levels of target gene PTGS2 in cervical tissue and cultured cervical cells. We compared the results with PTGS2 expression normalized to the least stable gene and found significant differences in gene expression, up to 10-fold in some samples, emphasizing the importance of appropriately selecting reference genes.

CONCLUSIONS

We recommend using the geometric mean of CFL1 and CLTC for normalization of qPCR studies in guinea pig cervical tissue studies, ACTB and PPIB in primary stroma cells and CLTC and PPIB in primary epithelial cells from guinea pig.

Time course of defense mechanisms in bovine endometrium in response to lipopolysaccharide

Endometritis caused by uterine infection after calving reduces fertility and causes major economic losses to the dairy industry. This study investigated the time course of an inflammatory response in bovine endometrium triggered by exposure to bacterial endotoxin lipopolysaccharide (LPS). Mixed endometrial epithelial and stromal cells (9:1 ratio) were grown to confluence as a model system and treated with an optimized dose of 100 ng/ml LPS in vitro. Gene expression responses were measured using quantitative PCR, and gene products were investigated using assays of culture medium and Western blotting. Of 17 candidate genes tested initially, LPS treatment for 24 h up-regulated mRNA expression of TLR4 signaling (TLR4, CD14), cytokines (IL1B, TNF), chemokines (IL8, CXCL5), antimicrobial peptides (LAP, S100A8, S100A9, S100A12), and matrix metalloproteinases (MMP1, MMP13). A 48 h, LPS time course study showed that TNF increased first at 1 h, followed by peak expression of IL1B at 6 h, and those of S100A8, S100A12, and LAP at 12 h. The intracellular S100A8 protein content doubled at 12-24 h but with little excretion into the medium. Regarding prostaglandin biosynthesis, PTGES mRNA was slightly higher after LPS exposure, whereas expression of the PGF synthase AKR1B1 was inhibited. Despite this, LPS treatment stimulated the secretion of both PGE₂ and PGF₂(alpha) to a similar extent. These results suggest that the family of S100 Ca²⁺ binding proteins are released from damaged endometrial cells and may play a major antimicrobial role. Prostaglandin synthesis increased during the uterine infection, but we found no evidence that this was associated with a change in the PGE:PGF ratio.

Hypoxia and PGE(2) regulate MiTF-CX during cervical ripening

The mechanisms by which the cervix remains closed during the massive uterine expansion of pregnancy are unknown. IL-8 is important for recruitment of immune cells into the cervical stroma, matrix remodeling, and dilation of the cervix during labor. Previously, we have shown that several cytokine genes transcriptionally repressed in the cervix during gestation are activated during cervical ripening and dilation. IL-8 gene expression is repressed in cervical stromal cells during pregnancy by the transcription factor microphthalmia-associated transcription factor (MiTF-CX). Here, we tested the hypothesis that hypoxia and the transcription factor hypoxia inducible factor-1α (HIF-1α) may regulate MiTF-CX and cervical ripening. Using tissues from women during pregnancy before and after cervical ripening, we show that, during cervical ripening, HIF-1α was stabilized and relocalized to the nucleus. Further, we found that hypoxia and two hypoxia mimetics that stabilize HIF-1α activated the transcriptional repressor differentiated embryo chondrocyte-expressed gene 1, which bound to sites in the MiTF-CX promoter crucial for its positive autoregulation. Ectopic overexpression of MiTF-CX abrogated hypoxia-induced up-regulation of IL-8 gene expression. We also show that activation of HIF-1α induced cyclooxygenase-2 and that prostaglandin E(2) repressed MiTF-CX. We conclude that hypoxia and stabilization of the transcription factor HIF-1α result in up-regulation of differentiated embryo chondrocyte-expressed gene 1, loss of MiTF, and absence of MiTF binding to the IL-8 promoter, which in turn leads to up-regulation of IL-8 gene expression. Hypoxia also up-regulated cyclooxygenase-2, leading to prostaglandin E(2)-mediated loss of MiTF in cervical stromal cells. The results support a pivotal role for hypoxia and HIF-1α in the cervical ripening process during pregnancy.

The core mouse response to infection by neospora caninum defined by gene set enrichment analyses

In this study, the BALB/c and Qs mouse responses to infection by the parasite Neospora caninum were investigated in order to identify host response mechanisms. Investigation was done using gene set (enrichment) analyses of microarray data. GSEA, MANOVA, Romer, subGSE and SAM-GS were used to study the contrasts Neospora strain type, Mouse type (BALB/c and Qs) and time post infection (6 hours post infection and 10 days post infection). The analyses show that the major signal in the core mouse response to infection is from time post infection and can be defined by gene ontology terms Protein Kinase Activity, Cell Proliferation and Transcription Initiation. Several terms linked to signaling, morphogenesis, response and fat metabolism were also identified. At 10 days post infection, genes associated with fatty acid metabolism were identified as up regulated in expression. The value of gene set (enrichment) analyses in the analysis of microarray data is discussed.

The microRNA (miR)-199a/214 cluster mediates opposing effects of progesterone and estrogen on uterine contractility during pregnancy and labor

Progesterone (P(4)) and estradiol-17β (E(2)) play critical and opposing roles in regulating myometrial quiescence and contractility during pregnancy and labor. Although these contrasting hormonal effects are likely mediated via differential regulation of inflammatory and contractile genes, the underlying mechanisms remain incompletely understood. Recently we discovered that targets of the microRNA (miR)-200 family, transcription factors zinc finger E-box binding homeobox (ZEB)-1 and ZEB2, serve as P(4)/progesterone receptor-mediated regulators of uterine quiescence during pregnancy. In the present study, we found that levels of the clustered miRNAs, miR-199a-3p and miR-214, were significantly decreased in laboring myometrium of pregnant mice and humans and in an inflammatory mouse model of preterm labor, whereas the miR-199a-3p/miR-214 target, cyclooxygenase-2, a critical enzyme in synthesis of proinflammatory prostaglandins, was coordinately increased. Overexpression of miR-199a-3p and miR-214 in cultured human myometrial cells inhibited cyclooxygenase-2 protein and blocked TNF-α-induced myometrial cell contractility, suggesting their physiological relevance. Notably, E(2) treatment of ovariectomized mice suppressed, whereas P(4) enhanced uterine miR-199a-3p/214 expression. Intriguingly, these opposing hormonal effects were mediated by ZEB1, which is induced by P(4), inhibited by E(2) and activates miR199a/214 transcription. Together, these findings identify miR-199a-3p/miR-214 as important regulators of myometrial contractility and provide new insight into strategies to prevent preterm birth.

New approaches to molecular diagnostics of prenatal pathology

Analysis of the spectrum of amniotic fluid proteins in physiological and abnormal pregnancy using proteomic analysis allowed detection of a number of difference proteins, that are absent or, alternatively, appear in gestosis. Among absent proteins, there were NADPH-dependent carbonyl reductase, epidermal fatty acid-binding protein, haptoglobin, calgranulins A and B. In contrast to proteomic spectrum of amniotic fluid in physiological pregnancy, 7 new proteins appear during gestosis, 3 of them were identified: C area of immunoglobulin K-chain, breast cancer metastasis suppressor-1, and protein-1 containing AIG2-like domain. Possible effects of revealed differences in proteomic spectrum on development of main disturbances during gestosis are discussed. Difference proteins detected in amniotic fluid may serve as gestosis markers.

Melatonin and the circadian timing of human parturition

Although the onset of spontaneous human parturition has long been known to occur preferentially during the nighttime and early morning hours, no convincing physiological explanation for this pattern has yet been proposed. This review focuses on the circadian timing of mammalian parturition, particularly in the human. It is proposed that differences in the phasing of parturition among different species are likely a function of opposite uterine responses to humoral cues, in particular those coding for time of day. The brain hormone melatonin fulfills many of the prerequisites to serve as a circadian signal for initiating uterine contractions that lead to human parturition. These encompass direct actions of melatonin on myometrial smooth muscle cells that are synergistic with oxytocin in facilitating greater uterine contractions at night. This may not only help to explain the nocturnal phasing of human parturition but also open new avenues for the management of term and preterm labor.

Circadian aspects of mammalian parturition: a review

The identification of circadian clocks in endocrine tissues has added considerable depth and complexity to our understanding of their physiology. A growing body of research reveals circadian clock gene expression in the uterus of non-pregnant and pregnant rodents. This review will focus on the mammalian uterus and its rhythmicity, particularly as it pertains to the circadian timing of parturition. This key event in the reproductive axis shows dramatic species-specific differences in its circadian phase. It is proposed here that these differences in the phasing of mammalian parturition are likely a function of opposite uterine cell responses to humoral cues. The argument will be made that melatonin fulfills many of the criteria to serve as a circadian signal in the initiation of human parturition, including specific actions on uterine smooth muscle cells that are consistent with a role for this hormone in the circadian timing of parturition.

Damage-associated molecular patterns (DAMPs) in preterm labor with intact membranes and preterm PROM: a study of the alarmin HMGB1

OBJECTIVE

Preterm parturition is a syndrome caused by multiple etiologies. Although intra-amniotic infection is causally linked with intrauterine inflammation and the onset of preterm labor, other patients have preterm labor in the absence of demonstrable infection. It is now clear that inflammation may be elicited by activation of the Damage-Associated Molecular Patterns (DAMPs), which include pathogen-associated molecular patterns (PAMPs) as well as "alarmins" (endogenous molecules that signal tissue and cellular damage). A prototypic alarmin is high-mobility group box 1 (HMGB1) protein, capable of inducing inflammation and tissue repair when it reaches the extracellular environment. HMGB1 is a late mediator of sepsis, and blockade of HMGB1 activity reduces mortality in an animal model of endotoxemia, even if administered late during the course of the disorder. The objectives of this study were to: (1) determine whether intra-amniotic infection/inflammation (IAI) is associated with changes in amniotic fluid concentrations of HMGB1; and (2) localize immunoreactivity of HMGB1 in the fetal membranes and umbilical cord of patients with chorioamnionitis.

METHODS

Amniotic fluid samples were collected from the following groups: (1) preterm labor with intact membranes (PTL) with (n=42) and without IAI (n=84); and (2) preterm prelabor rupture of membranes (PROM) with (n=38) and without IAI (n=35). IAI was defined as either a positive amniotic fluid culture or amniotic fluid concentration of interleukin-6 (IL-6) ≥ 2.6ng/mL. HMGB1 concentrations in amniotic fluid were determined by ELISA. Immunofluorescence staining for HMGB1 was performed in the fetal membranes and umbilical cord of pregnancies with acute chorioamnionitis.

RESULTS

(1) Amniotic fluid HMGB1 concentrations were higher in patients with IAI than in those without IAI in both the PTL and preterm PROM groups (PTL IAI: median 3.1 ng/mL vs. without IAI; median 0.98 ng/mL; p <0.001; and preterm PROM with IAI median 7.3 ng/mL vs. without IAI median 2.6 ng/mL; p=0.002); (2) patients with preterm PROM without IAI had a higher median amniotic fluid HMGB1 concentration than those with PTL and intact membranes without IAI (p <0.001); and (3) HMGB1 was immunolocalized to amnion epithelial cells and stromal cells in the Wharton's jelly (prominent in the nuclei and cytoplasm). Myofibroblasts and macrophages of the chorioamniotic connective tissue layer and infiltrating neutrophils showed diffuse cytoplasmic HMGB1 immunoreactivity.

CONCLUSIONS

(1) intra-amniotic infection/inflammation is associated with elevated amniotic fluid HMGB1 concentrations regardless of membrane status; (2) preterm PROM was associated with a higher amniotic fluid HMGB1 concentration than PTL with intact membranes, suggesting that rupture of membranes is associated with an elevation of alarmins; (3) immunoreactive HMGB1 was localized to amnion epithelial cells, Wharton's jelly and cells involved in the innate immune response; and (4) we propose that HMGB1 released from stress or injured cells into amniotic fluid may be responsible, in part, for intra-amniotic inflammation due to non-microbial insults.

Identification of a myometrial molecular profile for dystocic labor

Background

The most common indication for cesarean section (CS) in nulliparous women is dystocia secondary to ineffective myometrial contractility. The aim of this study was to identify a molecular profile in myometrium associated with dystocic labor.

Methods

Myometrial biopsies were obtained from the upper incisional margins of nulliparous women undergoing lower segment CS for dystocia (n = 4) and control women undergoing CS in the second stage who had demonstrated efficient uterine action during the first stage of labor (n = 4). All patients were in spontaneous (non-induced) labor and had received intrapartum oxytocin to accelerate labor. RNA was extracted from biopsies and hybridized to Affymetrix HuGene U133A Plus 2 microarrays. Internal validation was performed using quantitative SYBR Green Real-Time PCR.

Results

Seventy genes were differentially expressed between the two groups. 58 genes were down-regulated in the dystocia group. Gene ontology analysis revealed 12 of the 58 down-regulated genes were involved in the immune response. These included (ERAP2, (8.67 fold change (FC)) HLA-DQB1 (7.88 FC) CD28 (2.60 FC), LILRA3 (2.87 FC) and TGFBR3 (2.1 FC)) Hierarchical clustering demonstrated a difference in global gene expression patterns between the samples from dystocic and non-dystocic labours. RT-PCR validation was performed on 4 genes ERAP2, CD28, LILRA3 and TGFBR3

Conclusion

These findings suggest an underlying molecular basis for dystocia in nulliparous women in spontaneous labor. Differentially expressed genes suggest an important role for the immune response in dystocic labor and may provide important indicators for new diagnostic assays and potential intrapartum therapeutic targets.

Regulation of smooth muscle contraction by the epithelium: role of prostaglandins

As an analog to the endothelium situated next to the vascular smooth muscle, the epithelium is emerging as an important regulator of smooth muscle contraction in many vital organs/tissues by interacting with other cell types and releasing epithelium-derived factors, among which prostaglandins have been demonstrated to play a versatile role in governing smooth muscle contraction essential to the physiological and pathophysiological processes in a wide range of organ systems.

The effects of labor on differential gene expression in parturient women, placentas, and fetuses at term pregnancy

Labor and its associated pain are thought to have unique impacts on parturient women. The goal of this study was to investigate the effects of labor and associated pain on differential gene expression profiles in the maternal, fetal, and placental compartments. We used microarrays to analyze maternal blood (MB), fetal cord blood (CB), and placental tissue samples in pregnant women after term vaginal deliveries (laboring group) and in term pregnant women after scheduled Ceasarean sections (nonlaboring group). The upregulated genes in the MB of the laboring group are involved in cytokine and nuclear factor-kappa B signaling pathways, regulation of the networks of toll-like receptor 4, and suppressor of cytokine signaling 3. Upregulated genes in the CB of the laboring group are involved in responding to stress and stimuli by regulating the network genes of the T-cell receptor beta locus and the FK506 binding protein 8. Differentially expressed genes in the placenta of the laboring group are involved in nitric oxide transport, gas transport, response to hydrostatic pressure, oxygen transport, acute phase responses, and the tumor necrosis factor-mediated signaling pathway, which are important during the transient hypoxemia and hypoperfusion that occur in the placenta during uterine contractions. Interestingly, few of the genes exhibited simultaneous changes in all three compartments, indicating that different pathways and complex interactions may be involved in human labor. In conclusion, human labor and its associated pain elicit unique gene regulatory changes in MB, placenta, and CB.

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.

Effects of progesterone treatment on expression of genes involved in uterine quiescence

An important action of progesterone during pregnancy is to maintain the uterus in a quiescent state and thereby prevent preterm labor. The causes of preterm labor are not well understood, so progesterone action on the myometrium can provide clues about the processes that keep the uterus from contracting prematurely. Accordingly, we have carried out Affymetrix GeneChip analysis of progesterone effects on gene expression in immortalized human myometrial cells cultured from a patient near the end of pregnancy. Progesterone appears to inhibit uterine excitability by a number of mechanisms, including increased expression of calcium and voltage-operated K(+) channels, which dampens the electrical activity of the myometrial cell, downregulation of agents, and receptors involved in myometrial contraction, reduction in cell signal components that lead to increased intracellular Ca(2+) concentrations in response to contractile stimuli, and downregulation of proteins involved in the cross-linking of actin and myosin filaments to produce uterine contractions.

Expression of ATP-sensitive potassium channels in human pregnant myometrium

BACKGROUND

Potassium channels play critical roles in the regulation of cell membrane potential, which is central to the excitability of myometrium. The ATP-sensitive potassium (KATP) channel is one of the most abundant potassium channels in myometrium. The objectives of this study were to investigate the protein expression of KATP channel in human myometrium and determine the levels of KATP channel in lower and upper segmental myometrium before and after onset of labour.

METHODS

Both lower segmental (LS) and upper segmental (US) myometrial biopsies were collected at cesarean section from pregnant women not-in-labour (TNL) or in-labour (TL) at term. Protein expression level and cellular localization of four KATP channel subunits in US and LS myometrium were determined by Western blot analysis and immunohistochemistry, respectively. The contractile activity of myometrial strip was measured under isometric conditions.

RESULTS

Four KATP channel subunits, namely Kir6.1, Kir6.2, SUR1 and SUR2B were identified in pregnant myometrium. While found in vascular myocytes, these subunits appear to be preferentially expressed in myometrial myocytes. Diazoxide, a KATP channel opener, inhibited the spontaneous contractility of pregnant myometrium, suggesting that the KATP channels are functional in human pregnant myometrium. Diazoxide was less potent in TL strips than that in TNL strips. Interestingly, expression of SUR1 was greater in TL than TNL tissues, although no differences were found for SUR2B in these two tissues. For both lower and upper segmental myometrium, Kir6.1 and Kir6.2 were less in TL compared with TNL tissues.

CONCLUSIONS

Functional KATP channels are expressed in human pregnant myometrium. Down-regulation of Kir6.1 and Kir6.2 expression in myometrium may contribute to the enhanced uterine contractility associated with the onset of labour.

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.

Neuroendocrine mechanisms in pregnancy and parturition

The complex mechanisms controlling human parturition involves mother, fetus, and placenta, and stress is a key element activating a series of physiological adaptive responses. Preterm birth is a clinical syndrome that shares several characteristics with term birth. A major role for the neuroendocrine mechanisms has been proposed, and placenta/membranes are sources for neurohormones and peptides. Oxytocin (OT) is the neurohormone whose major target is uterine contractility and placenta represents a novel source that contributes to the mechanisms of parturition. The CRH/urocortin (Ucn) family is another important neuroendocrine pathway involved in term and preterm birth. The CRH/Ucn family consists of four ligands: CRH, Ucn, Ucn2, and Ucn3. These peptides have a pleyotropic function and are expressed by human placenta and fetal membranes. Uterine contractility, blood vessel tone, and immune function are influenced by CRH/Ucns during pregnancy and undergo major changes at parturition. Among the others, neurohormones, relaxin, parathyroid hormone-related protein, opioids, neurosteroids, and monoamines are expressed and secreted from placental tissues at parturition. Preterm birth is the consequence of a premature and sustained activation of endocrine and immune responses. A preterm birth evidence for a premature activation of OT secretion as well as increased maternal plasma CRH levels suggests a pathogenic role of these neurohormones. A decrease of maternal serum CRH-binding protein is a concurrent event. At midgestation, placental hypersecretion of CRH or Ucn has been proposed as a predictive marker of subsequent preterm delivery. While placenta represents the major source for CRH, fetus abundantly secretes Ucn and adrenal dehydroepiandrosterone in women with preterm birth. The relevant role of neuroendocrine mechanisms in preterm birth is sustained by basic and clinic implications.

Analyses of porcine public SNPs in coding-gene regions by re-sequencing and phenotypic association studies

The Porcine SNP database has a huge number of SNPs, but these SNPs are mostly found by computer data-mining procedures and have not been well characterized. We re-sequenced 1,439 porcine public SNPs from four commercial pig breeds and one Korean domestic breed (Korean Native pig, KNP) by using two DNA pools from eight unrelated animals in each breed. These SNPs were from 419 protein-coding genes covering the 18 autosomes, and the re-sequencing in breeds confirmed 690 public SNPs (47.9%) and 226 novel mutations (173 SNPs and 53 insertions/deletions). Thus, totally, 916 variations were found from our study. Of the 916 variations, 148 SNPs (16.2%) were found across all the five breeds, and 199 SNPs (21.7%) were breed specific polymorphisms. According to the SNP locations in the gene sequences, these 916 variations were categorized into 802 non-coding SNPs (785 in intron, 17 in 3'-UTR) and 114 coding SNPs (86 synonymous SNPs, 28 non-synonymous SNPs). The nucleotide substitution analyses for these SNPs revealed that 70.2% were from transitions, 20.0% from transversions, and the remaining 5.79% were deletions or insertions. Subsequently, we genotyped 261 SNPs from 180 genes in an experimental KNP × Landrace F2 cross by the Sequenom MassARRAY system. A total of 33 traits including growth, carcass composition and meat quality were analyzed for the phenotypic association tests using the 132 SNPs in 108 genes with minor allele frequency (MAF)>0.2. The association results showed that five marker-trait combinations were significant at the 5% experiment-wise level (ADCK4 for rear leg, MYH3 for rear leg, Hunter B, Loin weight and Shearforce) and four at the 10% experiment-wise level (DHX38 for average daily gain at live weight, LGALS9 for crude lipid, NGEF for front leg and LIFR for pH at 24 h). In addition, 49 SNPs in 44 genes showing significant association with the traits were detected at the 1% comparison-wise level. A large number of genes that function as enzymes, transcription factors or signalling molecules were considered as genetic markers for pig growth (RNF103, TSPAN31, DHX38, ABCF1, ABCC10, SCD5, KIAA0999 and FKBP10), muscling (HSPA5, PTPRM, NUP88, ADCK4, PLOD1, DLX1 and GRM8), fatness (PTGIS, IDH3B, RYR2 and NOL4) and meat quality traits (DUSP4, LIFR, NGEF, EWSR1, ACTN2, PLXND1, DLX3, LGALS9, ENO3, EPRS, TRIM29, EHMT2, RBM42, SESN2 and RAB4B). The SNPs or genes reported here may be beneficial to future marker assisted selection breeding in pigs.

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.

Cell-free fetal nucleic acids in amniotic fluid

BACKGROUND

Research into cell-free fetal (cff) nucleic acids has primarily focused on maternal plasma; however, cff DNA and RNA are also detectable in other body fluids such as amniotic fluid (AF). In AF, cff DNA is present in much greater concentrations than in maternal plasma and represents a pure fetal sample uncontaminated by maternal- and trophoblast-derived nucleic acids. The aim of this review was to summarize the current knowledge on cff nucleic acids in AF and to outline future research directions.

METHODS

MEDLINE and PREMEDLINE were searched up to August 2010 for original investigations of cell-free RNA or DNA in AF. Sixteen studies were included in the review.

RESULTS

AF cff DNA represents a physiologically separate pool from cff DNA in maternal plasma. The placenta is not a major source of nucleic acids in AF. It is feasible to isolate cff nucleic acids from small volumes of discarded AF supernatant in sufficient quality and quantity to perform microarray studies and downstream applications such as pathway analysis. This 'discovery-driven approach' has resulted in new information on the pathogenesis of Down syndrome and polyhydramnios. There is otherwise a paucity of information relating to the basic biology and clinical applications of cff nucleic acids in AF.

CONCLUSIONS

AF supernatant is a valuable and widely available but under-utilized biological resource. Further studies of cff nucleic acids in AF may lead to new insights into human fetal development and ultimately new approaches to antenatal treatment of human disease.

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.

Isobaric labeling and tandem mass spectrometry: a novel approach for profiling and quantifying proteins differentially expressed in amniotic fluid in preterm labor with and without intra-amniotic infection/inflammation

OBJECTIVE

Examination of the amniotic fluid (AF) proteome has been previously attempted to identify useful biomarkers in predicting the outcome of preterm labor (PTL). Isobaric Tag for Relative and Absolute Quantitation (iTRAQ) labeling allows direct ratiometric comparison of relative abundance of identified protein species among multiplexed samples. The purpose of this study was to apply, for the first time, the combination of iTRAQ and tandem mass spectrometry to identify proteins differentially regulated in AF samples of women with spontaneous PTL and intact membranes with and without intra-amniotic infection/inflammation (IAI).

METHODS

A cross-sectional study was designed and included AF samples from patients with spontaneous PTL and intact membranes in the following groups: (1) patients without IAI who delivered at term (n = 26); (2) patients who delivered preterm without IAI (n = 25); and (3) patients with IAI (n = 24). Proteomic profiling of AF samples was performed using a workflow involving tryptic digestion, iTRAQ labeling and multiplexing, strong cation exchange fractionation, and liquid chromatography tandem mass spectrometry. Twenty-five separate 4-plex samples were prepared and analyzed.

RESULTS

Collectively, 123,011 MS(2) spectra were analyzed, and over 25,000 peptides were analyzed by database search (X!Tandem and Mascot), resulting in the identification of 309 unique high-confidence proteins. Analysis of differentially present iTRAQ reporter peaks revealed many proteins that have been previously reported to be associated with preterm delivery with IAI. Importantly, many novel proteins were found to be up-regulated in the AF of patients with PTL and IAI including leukocyte elastase precursor, Thymosin-like 3, and 14-3-3 protein isoforms. Moreover, we observed differential expression of proteins in AF of patients who delivered preterm in the absence of IAI in comparison with those with PTL who delivered at term including Mimecan precursor, latent-transforming growth factor beta-binding protein isoform 1L precursor, and Resistin. These findings have been confirmed for Resistin in an independent cohort of samples using ELISA. Gene ontology enrichment analysis was employed to reveal families of proteins participating in distinct biological processes. We identified enrichment for host defense, anti-apoptosis, metabolism/catabolism and cell and protein mobility, localization and targeting.

CONCLUSIONS

(1) Proteomics with iTRAQ labeling is a profiling tool capable of revealing differential expression of proteins in AF; (2) We discovered 82 proteins differentially expressed in three clinical subgroups of premature labor, 67 which were heretofore unknown. Of particular importance is the identification of proteins differentially expressed in AF from women who delivered preterm in the absence of IAI. This is the first report of the positive identification of biomarkers in this subgroup of patients.

Metabolomics in premature labor: a novel approach to identify patients at risk for preterm delivery

OBJECTIVE

Biomarkers for preterm labor (PTL) and delivery can be discovered through the analysis of the transcriptome (transcriptomics) and protein composition (proteomics). Characterization of the global changes in low-molecular weight compounds which constitute the 'metabolic network' of cells (metabolome) is now possible by using a 'metabolomics' approach. Metabolomic profiling has special advantages over transcriptomics and proteomics since the metabolic network is downstream from gene expression and protein synthesis, and thus more closely reflects cell activity at a functional level. This study was conducted to determine if metabolomic profiling of the amniotic fluid can identify women with spontaneous PTL at risk for preterm delivery, regardless of the presence or absence of intraamniotic infection/inflammation (IAI).

STUDY DESIGN

Two retrospective cross-sectional studies were conducted, including three groups of pregnant women with spontaneous PTL and intact membranes: (1) PTL who delivered at term; (2) PTL without IAI who delivered preterm; and (3) PTL with IAI who delivered preterm. The first was an exploratory study that included 16, 19, and 20 patients in groups 1, 2, and 3, respectively. The second study included 40, 33, and 40 patients in groups 1, 2, and 3, respectively. Amniotic fluid metabolic profiling was performed by combining chemical separation (with gas and liquid chromatography) and mass spectrometry. Compounds were identified using authentic standards. The data were analyzed using discriminant analysis for the first study and Random Forest for the second.

RESULTS

(1) In the first study, metabolomic profiling of the amniotic fluid was able to identify patients as belonging to the correct clinical group with an overall 96.3% (53/55) accuracy; 15 of 16 patients with PTL who delivered at term were correctly classified; all patients with PTL without IAI who delivered preterm neonates were correctly identified as such (19/19), while 19/20 patients with PTL and IAI were correctly classified. (2) In the second study, metabolomic profiling was able to identify patients as belonging to the correct clinical group with an accuracy of 88.5% (100/113); 39 of 40 patients with PTL who delivered at term were correctly classified; 29 of 33 patients with PTL without IAI who delivered preterm neonates were correctly classified. Among patients with PTL and IAI, 32/40 were correctly classified. The metabolites responsible for the classification of patients in different clinical groups were identified. A preliminary draft of the human amniotic fluid metabolome was generated and found to contain products of the intermediate metabolism of mammalian cells and xenobiotic compounds (e.g. bacterial products and Salicylamide).

CONCLUSION

Among patients with spontaneous PTL with intact membranes, metabolic profiling of the amniotic fluid can be used to assess the risk of preterm delivery in the presence or absence of infection/inflammation.

Changes in rat myometrial plasma membrane protein kinase A are confined to parturition

We have previously shown that pregnant rat myometrial plasma membrane-associated cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA) decreases prior to delivery, coincident with a decline in the inhibitory effect of cAMP on contractant-stimulated parameters. We now find that rat myometrial membrane-associated PKA concentrations in early to mid-pregnancy are equivalent to those in cycling rats. Following the decline associated with parturition, membrane PKA recovers within 1 to 2 days postpartum. Treatment with the antiprogestin onapristone caused a decrease in myometrial membrane PKA catalytic and regulatory subunits compared to untreated controls by 12 hours. This coincided temporally with recently reported increases in electrical and contractile activity. In unilaterally pregnant rats, the decline in plasma membrane PKA was observed in both nonpregnant and pregnant horns but was more rapid in the pregnant horns. These data indicate that the myometrial plasma membrane PKA pattern before and during most of pregnancy is not consistent with progesterone exerting a primary influence on PKA membrane localization. Rather, the fall in membrane PKA associated with parturition may contribute to or be influenced by the increased contractile and electrical activity of labor that is a consequence of the loss of progesterone influence and is not absolutely dependent on the presence of fetuses.

Human effector/initiator gene sets that regulate myometrial contractility during term and preterm labor

OBJECTIVE

Distinct processes govern transition from quiescence to activation during term (TL) and preterm labor (PTL). We sought gene sets that are responsible for TL and PTL, along with the effector genes that are necessary for labor independent of gestation and underlying trigger.

STUDY DESIGN

Expression was analyzed in term and preterm with or without labor (n=6 subjects/group). Gene sets were generated with logic operations.

RESULTS

Thirty-four genes were expressed similarly in PTL/TL but were absent from nonlabor samples (effector set); 49 genes were specific to PTL (preterm initiator set), and 174 genes were specific to TL (term initiator set). The gene ontogeny processes that comprise term initiator and effector sets were diverse, although inflammation was represented in 4 of the top 10; inflammation dominated the preterm initiator set.

CONCLUSION

TL and PTL differ dramatically in initiator profiles. Although inflammation is part of the term initiator and the effector sets, it is an overwhelming part of PTL that is associated with intraamniotic inflammation.

The role of calprotectin in obstetrics and gynecology

The purpose of this article is to create the first complete review concerning the role of calprotectin, a calcium- and zinc-binding protein of the S100/calgranulins family, in obstetrics and gynecology. A Medline search was conducted between 6 and 8 June 2009 using the term calprotectin and its synonyms combined with the following ones: calprotectin, obstetrics and gynecology, breast cancer, ovarian cancer, endometrial cancer, cervical cancer, menstrual cycle, pregnancy, fetal implantation, labor, intra-amniotic inflammation, preeclampsia, HELLP syndrome, Rh(-) incompatibility. We found 46 studies which referred to obstetrics and gynecology. We excluded 11 studies which referred to obstetrics and gynecology but did not include enough information about calprotectin, and another two which referred to calprotectin but were not related to subjects of obstetrics and gynecology. Thus, we ended up with 33 studies which contained sufficient information to extract data for this review. All the articles were written in English. It was found that calprotectin is associated with many physiologic and pathologic processes in obstetrics and gynecology, such as: breast cancer, ovarian cancer, endometrial cancer, cervical cancer, cervical and vaginal physiology, menstrual cycle, pregnancy and labor. The role of calprotectin in these conditions is significant. In conclusion, the role of calprotectin seems to be important in several issues of obstetrics and gynecology. For example, calprotectin could be used as a diagnostic, prognostic or metastatic marker in several types of cancer, as a marker of inflammation and as a pharmaceutical target in many conditions. Further studies must be conducted to elucidate this role.

Global report on preterm birth and stillbirth (2 of 7): discovery science

Background

Normal and abnormal processes of pregnancy and childbirth are poorly understood. This second article in a global report explains what is known about the etiologies of preterm births and stillbirths and identifies critical gaps in knowledge. Two important concepts emerge: the continuum of pregnancy, beginning at implantation and ending with uterine involution following birth; and the multifactorial etiologies of preterm birth and stillbirth. Improved tools and data will enable discovery scientists to identify causal pathways and cost-effective interventions.

Pregnancy and parturition continuum

The biological process of pregnancy and childbirth begins with implantation and, after birth, ends with the return of the uterus to its previous state. The majority of pregnancy is characterized by rapid uterine and fetal growth without contractions. Yet most research has addressed only uterine stimulation (labor) that accounts for <0.5% of pregnancy.

Etiologies

The etiologies of preterm birth and stillbirth differ by gestational age, genetics, and environmental factors. Approximately 30% of all preterm births are indicated for either maternal or fetal complications, such as maternal illness or fetal growth restriction. Commonly recognized pathways leading to preterm birth occur most often during the gestational ages indicated: (1) inflammation caused by infection (22-32 weeks); (2) decidual hemorrhage caused by uteroplacental thrombosis (early or late preterm birth); (3) stress (32-36 weeks); and (4) uterine overdistention, often caused by multiple fetuses (32-36 weeks). Other contributors include cervical insufficiency, smoking, and systemic infections. Many stillbirths have similar causes and mechanisms. About two-thirds of late fetal deaths occur during the antepartum period; the other third occur during childbirth. Intrapartum asphyxia is a leading cause of stillbirths in low- and middle-income countries.

Recommendations

Utilizing new systems biology tools, opportunities now exist for researchers to investigate various pathways important to normal and abnormal pregnancies. Improved access to quality data and biological specimens are critical to advancing discovery science. Phenotypes, standardized definitions, and uniform criteria for assessing preterm birth and stillbirth outcomes are other immediate research needs.

Conclusion

Preterm birth and stillbirth have multifactorial etiologies. More resources must be directed toward accelerating our understanding of these complex processes, and identifying upstream and cost-effective solutions that will improve these pregnancy outcomes.

Are animal models relevant to key aspects of human parturition?

Preterm birth remains the most serious complication of pregnancy and is associated with increased rates of infant death or permanent neurodevelopmental disability. Our understanding of the regulation of parturition remains inadequate. The scientific literature, largely derived from rodent animal models, suggests two major mechanisms regulating the timing of parturition: the withdrawal of the steroid hormone progesterone and a proinflammatory response by the immune system. However, available evidence strongly suggests that parturition in the human has significantly different regulators and mediators from those in most of the animal models. Our objectives are to critically review the data and concepts that have arisen from use of animal models for parturition and to rationalize the use of a new model. Many animal models have contributed to advances in our understanding of the regulation of parturition. However, we suggest that those animals dependent on progesterone withdrawal to initiate parturition clearly have a limitation to their translation to the human. In such models, a linear sequence of events (e.g., luteolysis, progesterone withdrawal, uterine activation, parturition) gives rise to the concept of a "trigger" mechanism. Conversely, we propose that human parturition may arise from the concomitant maturation of several systems in parallel. We have termed this novel concept "modular accumulation of physiological systems" (MAPS). We also emphasize the urgency to determine the precise role of the immune system in the process of parturition in situations other than intrauterine infection. Finally, we accentuate the need to develop a nonprimate animal model whose physiology is more relevant to human parturition. We suggest that the guinea pig displays several key physiological characteristics of gestation that more closely resemble human pregnancy than do currently favored animal models. We conclude that the application of novel concepts and new models are required to advance translational research in parturition.

Expression of the calcium-activated potassium channel in upper and lower segment human myometrium during pregnancy and parturition

BACKGROUND

Large conductance calcium-activated potassium channel (BKCa) plays an important role in the control of uterine contractility during pregnancy. The change from uterine quiescence to enhanced contractile activity may be associated with the spatial and temporal expression of BKCa within myometrium. The objectives of this study were to examine the expression of BKCa alpha- and beta-subunit in upper segment (US) and lower segment (LS) regions of uterus, and to investigate for the possibly differential expression of these proteins in US and LS myometrium obtained from three functional states: (1) non-pregnant (NP); (2) term pregnant not in labour (TNL) and (3) term pregnant in labour (TL).

METHODS

Myometrial biopsies were collected from non-pregnant women at hysterectomy and pregnant women at either elective caesarean section or emergency caesarean section. Protein expression level and cellular localization of BKCa alpha- and beta-subunit in US and LS myometrium were determined by Western blot analysis and immunohistochemistry, respectively.

RESULTS

BKCa alpha- and beta-subunit were predominantly localized to myometrial smooth muscle in both US and LS myometrium obtained from non-pregnant and pregnant patients. The level of BKCa alpha-subunit in US but not in LS was significantly higher in NP myometrium than those measured in myometrium obtained during pregnancy. Lower expression of BKCa alpha-subunit in both US and LS was found in TL than in TNL biopsies. Expression of beta-subunit in both US and LS myometrium was significantly reduced in TL group compared with those measured in TNL group. There was no significant difference in BKCa beta-subunit expression in either US or LS between NP and TNL group.

CONCLUSION

Our results suggest that expression of BKCa alpha- and beta-subunit in pregnant myometrium is reduced during labour, which is consistent with the myometrial activity at the onset of parturition.

Minireview: fetal-maternal hormonal signaling in pregnancy and labor

Mechanisms underlying the initiation of parturition remain unclear. Throughout most of pregnancy, uterine quiescence is maintained by elevated progesterone acting through progesterone receptor (PR). Although in most mammals, parturition is associated with a marked decline in maternal progesterone, in humans, circulating progesterone and uterine PR remain elevated throughout pregnancy, suggesting a critical role for functional PR inactivation in the initiation of labor. Both term and preterm labor in humans and rodents are associated with an inflammatory response. In preterm labor, intraamniotic infection likely provides the stimulus for increased amniotic fluid interleukins and migration of inflammatory cells into the uterus and cervix. However, at term, the stimulus for this inflammatory response is unknown. Increasing evidence suggests that the developing fetus may produce physical and hormonal signals that stimulate macrophage migration to the uterus, with release of cytokines and activation of inflammatory transcription factors, such as nuclear factor kappaB (NF-kappaB) and activator protein 1 (AP-1), which also is activated by myometrial stretch. We postulate that the increased inflammatory response and NF-kappaB activation promote uterine contractility via 1) direct activation of contractile genes (e.g. COX-2, oxytocin receptor, and connexin 43) and 2) impairment of the capacity of PR to mediate uterine quiescence. PR function near term may be compromised by direct interaction with NF-kappaB, altered expression of PR coregulators, increased metabolism of progesterone within the cervix and myometrium, and increased expression of inhibitory PR isoforms. Alternatively, we propose that uterine quiescence during pregnancy is regulated, in part, by PR antagonism of the inflammatory response.

Term labor is associated with a core inflammatory response in human fetal membranes, myometrium, and cervix

OBJECTIVE

Identify overlap of the transcriptome of myometrium and cervix in association with human labor.

STUDY DESIGN

The transcriptional profile of myometrial and cervical biopsies obtained from women in spontaneous labor at term (n = 9) and not in labor (n = 9) were characterized by Affymetrix v2 U133 plus 2 arrays. Common canonical pathways and functional groups were identified by Ingenuity Pathway Analysis.

RESULTS

One hundred ten genes (false discovery rate < 1%) were commonly up-regulated by myometrium and cervix in association with labor and 29 genes (false discovery rate < 1%) down-regulated. Fold change in expression of up-regulated genes was strongly correlated; myometrium vs cervix (r = 0.51; P < .001), with no relationship in down-regulated genes (r = 0.26; P = .16). Canonical pathway analysis established up-regulation of inflammatory pathway signaling, with greatest increases in cellular movement and immune response gene ontology groups.

CONCLUSION

Gestational tissues exhibit a core inflammatory response in association with human parturition, with pathways regulating cellular trafficking dominating.

Changes in global gene expression in rat myometrium in transition from late pregnancy to parturition

The process of parturition involves the complex interplay of factors that change the excitability and contractile activity of the uterus. We have compared the relative gene expression profile of myometrium from rats before parturition (21 days pregnant) and during delivery, using high-density DNA microarray. Of 8,740 sequences available in the array, a total of 3,782 were detected as present. From the sequences that were significantly altered, 59 genes were upregulated and 82 genes were downregulated. We were able to detect changes in genes described to have altered expression level at term, including connexin 43 and 26, cyclooxygenase 2, and oxytocin receptor, as well as novel genes that have been not previously associated with parturition. Quantitative real-time PCR on selected genes further confirmed the microarray data. Here we report for the first time that aquaporin5 (AQP5), a member of the aquaporin water channel family, was dramatically downregulated during parturition (approximately 100-fold by microarray and approximately 50-fold by real-time PCR). The emerging profile highlights biochemical cascades occurring in a period of approximately 36 h that trigger parturition and the initiation of myometrium reverse remodeling postpartum. The microarray analysis uncovered genes that were previously suspected to play a role in parturition. This regulation involves genes from immune/inflammatory response, steroid/lipid metabolism, calcium homeostasis, cell volume regulation, cell signaling, cell division, and tissue remodeling, suggesting the presence of multiple and redundant mechanisms altered in the process of birth.

Proteomic analysis of amniotic fluid to identify women with preterm labor and intra-amniotic inflammation/infection: the use of a novel computational method to analyze mass spectrometric profiling

OBJECTIVE

Examination of the amniotic fluid proteome has been used to identify biomarkers for intra-amniotic inflammation as well as those that may be useful in predicting the outcome of preterm labor. The purpose of this study was to combine a novel computational method of pattern discovery with mass spectrometric proteomic profiling of amniotic fluid to discover biomarkers of intra-amniotic infection/inflammation (IAI).

METHODS

This cross-sectional study included patients with spontaneous preterm labor and intact membranes who delivered at term (n = 59) and those who delivered preterm with IAI (n = 60). Proteomic profiling was performed using surface-enhanced laser desorption/ionization (SELDI) mass spectrometry. A proteomic profile was acquired through multiple simultaneous SELDI conditions, which were combined in a single proteomic 'fingerprint' using a novel computational approach. Classification of patients based on their associated surface-enhanced laser desorption/ionization-time of flight (SELDI-TOF) mass spectra as belonging to either the class of individuals with preterm delivery with IAI or term delivery was accomplished by constructing an empirical model. The first phase in the construction of this empirical model involved the selection of adjustable parameters utilizing a training/testing subset of data. The second phase tested the generalization of the model by utilizing a blinded validation set of patients who were not employed in parameter selection.

RESULTS

Gestational age at amniocentesis was not significantly different between the groups. Thirty-nine unique mass spectrometric peaks discriminated patients with preterm labor/delivery with IAI from those with preterm labor and term delivery. In the testing/training dataset, the classification accuracies (averaged over 100 random draws) were: 91.4% (40.2/44) for patients with preterm delivery with IAI, and 91.2% (40.1/44) for term delivery. The overall accuracy of the classification of patients in the validation dataset was 90.3% (28/31).

CONCLUSIONS

Proteomic analysis of amniotic fluid allowed the identification of mass spectrometry features, which can distinguish patients with preterm labor with IAI from those with preterm labor without inflammation or infection who subsequently delivered at term.

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.

Upregulation of PSCDBP, TLR2, TWIST1, FLJ35382, EDNRB, and RGS12 gene expression in human myometrium at labor

The regulatory mechanisms underlying myometrial smooth muscle contractility during labor are poorly understood. The authors therefore investigated the transcriptional profile of the changes that occur in the human myometrium at term pregnancy when compared with that at labor. Microarray technology was used to identify differentially expressed genes in human myometrium at labor. Real-time fluorescence reversetranscriptase polymerase chain reaction (RT-PCR) was subsequently performed to verify the microarray data. Semiquantitative RT-PCR, Western blotting, and microscopy methodologies were also used. Certain novel genes were found to be upregulated in human myometrium at labor. Of these, PSCDBP, TLR2, TWIST1 , FLJ35382, andRGS12 have not been previously characterized or identified in human myometrium. EDNRB is the other novel labor-associated gene whose reported expression is also upregulated at labor. All 6 genes were expressed on human myometrial smooth muscle cells. These novel upregulated genes are involved in multiple pathways that may be associated with a variety of cellular processes including inflammation, transcriptional regulation, and intracellular signaling.

Estrogen and progesterone metabolism in the cervix during pregnancy and parturition

CONTEXT

Experimental and clinical studies in a variety of nonprimate species demonstrate that progesterone withdrawal leads to changes in gene expression that initiate parturition at term. Mice deficient in 5alpha-reductase type I fail to undergo cervical ripening at term despite the timely onset of luteolysis and progesterone withdrawal in blood.

OBJECTIVE

Our objective was to test the hypothesis that estrogen and progesterone metabolism is regulated in cervical tissues during pregnancy, even in species in which parturition is not characterized by progesterone withdrawal in blood.

DESIGN

Estradiol and progesterone metabolism was quantified in intact cervical tissues from nonpregnant and pregnant women at term before or after labor.

SETTING

The study was conducted at a university hospital.

PATIENTS

Tissues were obtained from five nonpregnant and 21 pregnant women (nine before labor and 12 in labor).

MAIN OUTCOME MEASURES

Enzyme activity measurements, Northern blot analysis, quantitative real-time RT-PCR, and immunohistochemistry were used to quantify steroid hormone metabolizing enzymes in cervical and myometrial tissues.

RESULTS

During pregnancy, 17beta-hydroxysteroid dehydrogenase type 2 was induced in glandular epithelial cells to catalyze the conversion of estradiol to estrone and stroma-derived 20alpha-hydroxyprogesterone to progesterone. During parturition, 17beta-hydroxysteroid dehydrogenase type 2 was down-regulated in endocervical cells, thereby creating a microenvironment favorable for cervical ripening.

CONCLUSIONS

Together, the data indicate that cervical ripening during parturition involves localized regulation of estrogen and progesterone metabolism through a complex relationship between cervical epithelium and stroma, and that steroid hormone metabolism in cervical tissues from pregnant women is unique from that in mice.

Aberrant gene expression patterns in placentomes are associated with phenotypically normal and abnormal cattle cloned by somatic cell nuclear transfer

Transcription profiling of placentomes derived from somatic cell nuclear transfer (SCNT, n = 20), in vitro fertilization (IVF, n = 9), and artificial insemination (AI, n = 9) at or near term development was performed to better understand why SCNT and IVF often result in placental defects, hydrops, and large offspring syndrome (LOS). Multivariate analysis of variance was used to distinguish the effects of SCNT, IVF, and AI on gene expression, taking into account the effects of parturition (term or preterm), sex of fetus, breed of dam, breed of fetus, and pathological finding in the offspring (hydrops, normal, or other abnormalities). Differential expression of 20 physiologically important genes was confirmed with quantitative PCR. The largest effect on placentome gene expression was attributable to whether placentas were collected at term or preterm (i.e., whether the collection was because of disease or to obtain stage-matched controls) followed by placentome source (AI, IVF, or SCNT). Gene expression in SCNT placentomes was dramatically different from AI ( n = 336 genes; 276 >2-fold) and from IVF ( n = 733 genes; 162 >2-fold) placentomes. Functional analysis of differentially expressed genes (DEG) showed that IVF has significant effects on genes associated with cellular metabolism. In contrast, DEG associated with SCNT are involved in multiple pathways, including cell cycle, cell death, and gene expression. Many DEG were shared between the gene lists for IVF and SCNT comparisons, suggesting that common pathways are affected by the embryo culture methods used for IVF and SCNT. However, the many unique gene functions and pathways affected by SCNT suggest that cloned fetuses may be starved and accumulating toxic wastes due to placental insufficiency caused by reprogramming errors. Many of these genes are candidates for hydrops and LOS.

Identification of interleukin-1β regulated genes in uterine smooth muscle cells

We analyzed the response of uterine smooth muscle cells to interleukin-1β (IL-1β). We first showed that PHM1-31 myometrial cells, our cellular model, are contractile. To determine the molecular mechanisms of uterine smooth muscle cell activation by proinflammatory cytokines, we performed genechip expression array profiling studies of PHM1-31 cells in the absence and the presence of IL-1β. In total, we identified 198 known genes whose mRNA levels are significantly modulated (> 2.0-fold change) following IL-1β exposure. We confirmed the expression changes for selected genes by independent mRNA and protein analysis. The group of genes induced by IL-1β includes transcription factors and inflammatory response genes such as nuclear factor of κ light polypeptide gene enhancer in B-cells (NFκB), pentraxin-related gene (PTX3), and tumor necrosis factor α-induced protein 3/A20 (TNFAIP3/A20). We also found up-regulation of chemokines like C-X-C motif ligand 3 (CXCL3) and extracellular matrix remodeling signaling molecules like tenascin C (TNC). Our data suggest that IL-1β elicits the rapid activation of a cellular network of genes particularly implicated in inflammatory response that may create a cellular environment favorable for myometrial cell contraction. Our results provide novel insights into the mechanisms of uterine smooth muscle cell regulation and possibly infection-induced preterm labor.