Human myometrial gene expression before and during parturition

ADRB3 adrenergic receptor is a key regulator of human myometrial apoptosis and inflammation during chorioamnionitis

The pathophysiology underlying preterm labor triggered by inflammatory conditions such as chorioamnionitis remains largely unclear. It has already been suggested that beta-3 adrenergic (ADRB3) agonists might be of interest in the pharmacological management of preterm labor. Although there is evidence implicating ADRB receptors in the control of inflammation, there are minimal data relating specifically to ADRB3. To explore the cellular consequences of chorioamnionitis and detect apoptosis, we first performed immunostaining and Western blot experiments on human myometrial samples obtained from women with confirmed chorioamnionitis. We then developed an in vitro model of chorioamnionitis by incubating the myometrial samples obtained from uncomplicated pregnancies with Escherichia coli lipopolysaccharide (LPS). We observed that chorioamnionitis was associated with a significant increase in cleaved CASP3 protein expression, as well as chromatin condensation, which were reproduced experimentally by LPS stimulation (10 microg/ml, 48 h). Lipopolysaccharide stimulation of normal human myometrium also induced CASP3 transcripts, increased the proapoptotic marker BAX, and decreased the antiapoptotic marker BCL2. Lipopolysaccharide-induced apoptosis was antagonized by neutralization of secreted tumor necrosis factor by a specific antibody. Furthermore, LPS stimulation increased medium culture levels of proinflammatory cytokines interleukin 6 (IL6) and IL8. Lipopolysaccharide-induced apoptosis and cytokine production were prevented by the new and potent ADRB3 agonist SAR150640 in a concentration-dependent manner. SAR150640 by itself did not exhibit any effect on apoptosis or cytokine production in control tissues. This study shows that chorioamnionitis is associated with apoptosis of human myometrial cells. It emphasizes the potential therapeutic interest of ADRB3 agonists in the field of preterm labor and other inflammatory conditions.

MYOMETRIAL ACTIVATION – COORDINATION, CONNECTIVITY AND CONTRACTILITY

One of the most important stages of pregnancy is the activation of uterine contractions that result in the expulsion of the fetus. The timely onset of labour is clearly important for a healthy start to life but incomplete understanding of the precise mechanisms regulating labour onset have prohibited the development of effective and safe treatments for preterm labour. This review explores the activation of the myometrium at labour onset, focussing on mechanisms of uterine contractility, including those proteins that play an important role in smooth muscle contractility. The review primarily focuses on human work but in the absence of human data describes animal studies. A broad overview of myometrial contraction mechanisms is provided before discussing more detailed aspects and identifying areas where uncertainty remains. Also discussed is the recent application of ‘omics’ based approaches to parturition research, which has facilitated an increase in the understanding of myometrial activation.

Identification of 9 uterine genes that are regulated during mouse pregnancy and exhibit abnormal levels in the cyclooxygenase-1 knockout mouse

BACKGROUND

Preterm birth is the leading cause of all infant mortality. In 2004, 12.5% of all births were preterm. In order to understand preterm labor, we must first understand normal labor. Since many of the myometrial changes that occur during pregnancy are similar in mice and humans and mouse gestation is short, we have studied the uterine genes that change in the mouse during pregnancy. Here, we used microarray analysis to identify uterine genes in the gravid mouse that are differentially regulated in the cyclooxygenase-1 knockout mouse model of delayed parturition.

METHODS

Gestational d18.0 uteri (n = 4) were collected from pregnant wild-type and cyclooxygenase-1 knockout mice. Part of the uterus was used for frozen sections and RNA was isolated from the remainder. Microarray analysis was performed at the Indiana University School of Medicine Genomic Core and analyzed using the Microarray Data Portal. Northern analysis was performed to confirm microarray data and the genes localized in the gravid uterus by in situ hybridization.

RESULTS

We identified 277 genes that are abnormally expressed in the gravid d18.0 cyclooxygenase-1 knockout mouse. Nine of these genes are also regulated in the normal murine uterus during the last half of gestation. Many of these genes are involved in the immune response, consistent with an important role of the immune system in parturition. Expression of 4 of these genes; arginase I, IgJ, Tnfrsf9 and troponin; was confirmed by Northern analysis to be mis-regulated during pregnancy in the knockout mouse. In situ hybridization of these genes demonstrated a similar location in the gravid wild-type and Cox-1 knockout mouse uteri.

CONCLUSION

To our knowledge, this is the first work to demonstrate the uterine location of these 4 genes in the mouse during late pregnancy. There are several putative transcription factor binding sites that are shared by many of the 9 genes identified here including; estrogen and progesterone response elements and Ets binding sites. In summary, this work identifies 9 uterine murine genes that may play a role in parturition. The function of these genes is consistent with an important role of the immune system in parturition.

Towards understanding the myometrial physiome: approaches for the construction of a virtual physiological uterus

Premature labour (PTL) is the single most significant factor contributing to neonatal morbidity in Europe with enormous attendant healthcare and social costs. Consequently, it remains a major challenge to alleviate the cause and impact of this condition. Our ability to improve the diagnosis and treatment of women most at risk of PTL is, however, actually hampered by an incomplete understanding of the ways in which the functions of the uterine myocyte are integrated to effect an appropriate biological response at the multicellular whole organ system. The level of organization required to co-ordinate labouring uterine contractile effort in time and space can be considered immense. There is a multitude of what might be considered mini-systems involved, each with their own regulatory feedback cycles, yet they each, in turn, will influence the behaviour of a related system. These include, but are not exclusive to, gestational-dependent regulation of transcription, translation, post-translational modifications, intracellular signaling dynamics, cell morphology, intercellular communication and tissue level morphology.

We propose that in order to comprehend how these mini-systems integrate to facilitate uterine contraction during labour (preterm or term) we must, in concert with biological experimentation, construct detailed mathematical descriptions of our findings. This serves three purposes: firstly, providing a quantitative description of series of complex observations; secondly, proferring a database platform that informs further testable experimentation; thirdly, advancing towards the establishment of a virtual physiological uterus and in silico clinical diagnosis and treatment of PTL.

Alternative splicing: an important mechanism for myometrial gene regulation that can be manipulated to target specific genes associated with preterm labour

Considerable effort has been expended in attempting to distinguish genes that contribute to initiating the onset of term and preterm labour (PTL) from those that change in expression as a consequence of the progression of labour. The ability to define more clearly the genes involved in triggering labour contractions should lead to the development of new effective and safer strategies to prevent preterm birth. There is ample evidence to suggest that specific genes are co-ordinately regulated within the upper and lower regions of the myometrium prior to and during parturition and many of these genes are regulated by alternative pre-mRNA splicing. This mini-review highlights that expression of a range of different splicing factors, with defined roles in pre-mRNA splicing, is both temporally and spatially regulated within the uterine smooth muscle during pregnancy and labour. Moreover, several of these splicing factors play key roles in controlling the differential expression of specific regulatory proteins involved in uterine signalling and uterine quiescence. In addition, antisense morpholino oligonucleotide manipulation of pre-mRNA splicing may have potential in defining and targeting uterine pro-labour genes and thus contribute to the development of new therapeutic approaches to prevent PTL.

Functional genomics of the pregnant uterus: from expectations to reality, a compilation of studies in the myometrium

Background

Studies on the human myometrium have reported on different microarrays containing different sets of genes or ESTs. However each study profiled only a small number of patients due to various constraints. More profiling information would be an addition to our knowledge base of parturition.

Methods

We compiled from five human studies, transcriptional differences between the non pregnant myometrium (NP), preterm myometrium (PTNIL), term myometrium not in labor (TNIL) and term myometrium in labor (TIL). Software modules developed by the Draghici's group at Wayne State University (Detroit, MI, USA) were used to propose a hierarchical list of several KEGG pathways most likely adjusted to changes observed in microarray experiments.

Results

The differential expression of 118 genes could be dispatched in 14 main KEGG pathways that were the most representative of the changes seen in NP and PTNIL, versus TNIL or TIL. Despite the potential of multiple pitfalls inherent to the use of the microarray technology, gene module analysis of the myometrial transcriptome reveals the activation of precise signaling pathways, some of which may have been under evaluated.

Conclusion

The remodelling and maturation processes that the uterus undergoes in pregnancy appear clearly as phenomena which last during the full course of gestation. It is attested by the nature of the main signaling pathways represented, in the comparison of the PTNIL versus TNIL uterus. Comparatively, the onset of labor is a phenomenon which remains less well characterized by these methods of analysis, possibly because it is a phenomenon occurring in too short a window to have been grasped by the studies carried out up to now.

Steroid hormone control of myometrial contractility and parturition

The precise temporal control of uterine contractility is essential for the success of pregnancy. For most of pregnancy, progesterone acting through genomic and non-genomic mechanisms promotes myometrial relaxation. At parturition the relaxatory actions of progesterone are nullified and the combined stimulatory actions of estrogens and other factors such as myometrial distention and immune/inflammatory cytokines, transform the myometrium to a highly contractile and excitable state leading to labor and delivery. This review addresses current understanding of how progesterone and estrogens affect the contractility of the pregnancy myometrium and how their actions are coordinated and controlled as part of the parturition cascade.

Biomechanical Properties of the Lower Uterine Segment Above and Below the Reflection of the Urinary Bladder Flap

OBJECTIVE

To test the hypothesis that differences in the matrix arrangement of the lower uterine segment (above and below the reflection of the bladder flap) translate to differences in biomechanical or structural properties of the uterine wall.

METHODS

We enrolled prospectively 40 women at term randomized to a bladder flap (n=21) versus no bladder flap (n=19) at the time of a cesarean delivery for dystocia. Tensile properties of tissue biopsies from the upper and lower edges of the hysterotomy incision were quantitated using a stretching regimen designed to mimic labor. Parameters such as slope, yield point, and break point were analyzed in relationship to biochemical (total collagen, sulfated glycosaminoglycans, pyridinoline-deoxypyridinoline) and histological (collagen birefringence) properties of the tissue.

RESULTS

The lower edge of the hysterotomy had a higher collagen content than the upper, independently of whether the hysterotomy site was above or below the reflection of the bladder (P<.001 for edge level, P=.8 for bladder flap). The pyridinoline-to-collagen ratio (a reflection of collagen cross-linking) was significantly decreased in the lower edge of the hysterotomy, independently of a bladder flap (P<.001). Neither collagen birefringence nor the amount of sulfated glycosaminoglycans differed among sites. There were no significant differences in biomechanical properties between the upper and lower edges of the hysterotomy, whether or not a bladder flap was created.

CONCLUSION

The lower uterine segment of women with dystocia maintains its overall biomechanical properties despite significant quantitative and qualitative differences in fibrillar collagen between the upper and lower edge of the hysterotomy incision.

LEVEL OF EVIDENCE

II.

Involvement of nuclear factor-kB activation through RhoA/Rho-kinase pathway in LPS-induced IL-8 production in human cervical stromal cells

Interleukin-8 (IL-8) is a chemokine that recruits and activates neutrophils in stromal tissue and plays an essential role in cervical ripening. Nuclear factor-kB (NF-kB) is known to be important for the up-regulation of IL-8 gene expression. We examined the molecular mechanisms responsible for NF-kB activation in IL-8 production in cervical stromal cells. Lipopolysaccharide (LPS) and IL-1beta stimulated IL-8 production by cervical stromal cells in a dose-dependent manner. Pretreatment of cervical stromal cells with inhibitors of RhoA (C3 transferase exoenzyme), Rho-kinase (Y-27632) or NF-kB (BAY11-7082) effectively blocked LPS-induced IL-8 release. In contrast, IL-1beta-induced IL-8 production was significantly blocked by BAY11-7082, but not by C3 transferase exoenzyme or Y-27632. Pull-down assays showed that LPS activated RhoA, but IL-1beta caused only a lower level of activation. Transfection of the cervical stromal cells with RhoA small interfering RNA (siRNA) inhibited LPS-stimulated IL-8 production, whereas IL-1beta-induced IL-8 production was not significantly inhibited by knockdown of RhoA with siRNA. Using an NF-kB transcription reporter vector, luciferase assays demonstrated that incubation with LPS or IL-1beta induced the activation of NF-kB in cervical stromal cells. Activation of NF-kB by LPS was inhibited by treatment with C3 exoenzyme, Y-27632 or RhoA siRNA. However, inhibition of the RhoA/Rho-kinase pathway did not attenuate the activation of NF-kB by IL-1beta. These results suggest that LPS-induced IL-8 production is accompanied by enhanced NF-kB activation through the RhoA/Rho-kinase pathway in human cervical cells.

The use of high-dimensional biology (genomics, transcriptomics, proteomics, and metabolomics) to understand the preterm parturition syndrome

High-dimensional biology (HDB) refers to the simultaneous study of the genetic variants (DNA variation), transcription (messenger RNA [mRNA]), peptides and proteins, and metabolites of an organ, tissue, or an organism in health and disease. The fundamental premise is that the evolutionary complexity of biological systems renders them difficult to comprehensively understand using only a reductionist approach. Such complexity can become tractable with the use of "omics" research. This term refers to the study of entities in aggregate. The current nomenclature of "omics" sciences includes genomics for DNA variants, transcriptomics for mRNA, proteomics for proteins, and metabolomics for intermediate products of metabolism. Another discipline relevant to medicine is pharmacogenomics. The two major advances that have made HDB possible are technological breakthroughs that allow simultaneous examination of thousands of genes, transcripts, and proteins, etc., with high-throughput techniques and analytical tools to extract information. What is conventionally considered hypothesis-driven research and discovery-driven research (through "omic" methodologies) are complementary and synergistic. Here we review data which have been derived from: 1) genomics to examine predisposing factors for preterm birth; 2) transcriptomics to determine changes in mRNA in reproductive tissues associated with preterm labour and preterm prelabour rupture of membranes; 3) proteomics to identify differentially expressed proteins in amniotic fluid of women with preterm labour; and 4) metabolomics to identify the metabolic footprints of women with preterm labour likely to deliver preterm and those who will deliver at term. The complementary nature of discovery science and HDB is emphasised.

Preterm Birth: A Review of Genetic Factors and Future Directions for Genetic Study

Preterm birth remains the leading cause of neonatal morbidity and mortality and is likely the result of interactions between specific genes and the maternal or fetal environment. The strong familial clustering of disease with documented increased risks in patients with a personal or family history of preterm birth and the racial disparities in the incidence of preterm birth support a genetic component of this condition. New technologies such as microarray, single nucleotide polymorphism analysis, and proteomics will lead to the eventual identification and characterization of the genetic etiology of preterm birth.

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

Since the controversies regarding the use of non-steroidal anti-inflammatory drugs (NSAIDs) and selective cyclo-oxygenase (COX)-2 antagonists for the treatment of preterm labour (PTL), more emphasis has been placed on investigating the terminal synthases involved in the production of prostaglandins (PGs) to allow more targeted therapy in PTL. Prostaglandin E(2) (PGE(2)) is synthesized by one of three enzymes, cytosolic prostaglandin E synthase (cPGES), microsomal PGES-1 (mPGES-1) and microsomal PGES-2 (mPGES-2). We have determined (i) the immuno-localization of all three PGES enzymes in lower segment pregnant human myometrium, (ii) the expression of PGES and COX-2 mRNA expression at term and preterm gestation with and without labour and (iii) the effect of interleukin (IL)-1beta on COX-2 and PGES mRNA and protein expression in human myometrial smooth muscle (HMSM) cell cultures. We show mPGES-1 protein located predominantly in myometrial and vascular smooth muscle cells (SMCs), whilst mPGES-2 protein is largely in stromal cells surrounding the SMC and cPGES is diffusely located throughout the myometrium. Expression of mPGES-2 mRNA increased with term labour and PTL and expression of COX-2 and mPGES-1 mRNA with term labour, whereas cPGES expression did not change. IL-1beta stimulated release of PGE(2) by HMSM cells and increased COX-2 and mPGES-1 mRNA and protein expression. Thus, COX-2 expression and mPGES-1 expression are co-ordinately up-regulated in lower segment myometrium with term labour and with IL-1beta treatment in HMSM cells.

The transcriptome of the uterine cervix before and after spontaneous term parturition

OBJECTIVE

This study was designed to identify genes differentially expressed in the human uterine cervix after spontaneous term labor.

STUDY DESIGN

The transcriptome of cervical tissue was characterized using Affymetrix HG-U133 plus 2 microarrays. Samples were collected from patients at term not in labor (n = 7) and after spontaneous labor (n = 9). Microarray statistical analysis included robust multiarray average, reduction of invariant probes, and permutation analysis for differential expression. Real-time quantitative reverse transcriptase-polymerase chain reaction assays of selected genes were performed on a new set of samples from term patients without labor (n = 10) and patients after spontaneous labor (n = 9).

RESULTS

(1) The cervical transcriptome of term patients without labor was dramatically different from that of patients who underwent labor; (2) unique genes (n = 1192) were differentially expressed in the cervical tissue from patients after spontaneous labor, compared with that of the term patients without labor (false discovery rate less than 0.05, absolute fold change greater than 2); (3) Gene Ontology analysis indicated that multiple "Biological Process" categories were enriched, including "response to biotic stimulus," "apoptosis," "epidermis development," and "steroid metabolism"; (4) of major interest, genes involved in neutrophil chemotaxis were dramatically up-regulated in specimens from women after spontaneous labor; (5) real-time quantitative reverse transcriptase-polymerase chain reaction confirmed the increased expression of interleukin-8, interleukin-6, and vascular endothelial growth factor in patients after spontaneous labor; and (6) Toll-like receptor-3 and Toll-like receptor-5 showed decreased gene expression in patients after spontaneous labor. This was confirmed by real-time quantitative reverse transcriptase-polymerase chain reaction.

CONCLUSION

(1) Cervical dilatation in term labor is associated with a stereotypic gene expression pattern determined by microarray, which is characterized by overexpression of genes involved in neutrophil chemotaxis, apoptosis, extracellular matrix regulation, and steroid metabolism; (2) Toll-like receptor-3 and Toll-like receptor-5 are differentially regulated during spontaneous parturition at term; and (3) this study provides an unbiased and comprehensive description of the changes in the cervical transcriptome before and after spontaneous term labor.

Proteomics, Part II: The Emerging Role of Proteomics Over Genomics in Spontaneous Preterm Labor/Birth

Conventional wisdom holds that complications of immature organ systems such as respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, and bronchopulmonary dysplasia are the primary causes of the high neonatal morbidity and mortality attendant preterm delivery. However, recent evidence suggests that a major cause of prematurity-associated neonatal pathology is the fetal and neonatal response to inflammation/infection. Although functional genomics offered the promise of providing answers to many of these questions, the identification of the genes intrinsic to human parturition proved to be a difficult task. Proteomic profiling of the amniotic fluid (AF) provides a precise means for detection of inflammation by revealing the presence of 4 biomarkers (defensins-2 and -1, calgranulin-C, and calgranulin-A) that are highly predictive of intrauterine inflammation (MR score). The MR score is especially useful as it presents a gradient of disease activity progressing from "absent" to "mild" to "severe" inflammation. Thus, it provides the ability to identify patients who may benefit from interventions in utero in a modern diagnostic-therapeutic framework.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to explain that the cause or causes of preterm delivery are still unknown, recall that functional genomics has not given the answer to these causes, and state that proteomic profiling of amniotic fluid, through mass-restricted (MR) scoring, may be predictive of intrauterine inflammation and allow for potential diagnosis and potential therapy.

Progesterone receptor plays a major antiinflammatory role in human myometrial cells by antagonism of nuclear factor-kappaB activation of cyclooxygenase 2 expression

Spontaneous labor in women and in other mammals is likely mediated by a concerted series of biochemical events that negatively impact the ability of the progesterone receptor (PR) to regulate target genes that maintain myometrial quiescence. In the present study, we tested the hypothesis that progesterone/PR inhibits uterine contractility by blocking nuclear factor kappaB (NF-kappaB) activation and induction of cyclooxygenase-2 (COX-2), a contractile gene that is up-regulated in labor. To uncover mechanisms for regulation of uterine COX-2, immortalized human fundal myometrial cells were treated with IL-1beta +/- progesterone. IL-1beta alone caused a marked up-regulation of COX-2 mRNA, whereas treatment with progesterone suppressed this induction. This was also observed in human breast cancer (T47D) cells. In both cell lines, this inhibitory effect of progesterone was blocked by RU486. Using chromatin immunoprecipitation, we observed that IL-1beta stimulated recruitment of NF-kappaB p65 to both proximal and distal NF-kappaB elements of the COX-2 promoter; these effects were diminished by coincubation with progesterone. The ability of progesterone to inhibit COX-2 expression in myometrial cells was associated with rapid induction of mRNA and protein levels of inhibitor of kappaBalpha, a protein that blocks NF-kappaB transactivation. Furthermore, small interfering RNA-mediated ablation of both PR-A and PR-B isoforms in T47D cells greatly enhanced NF-kappaB activation and COX-2 expression. These effects were observed in the absence of exogenous progesterone, suggesting a ligand-independent action of PR. Based on these findings, we propose that PR may inhibit NF-kappaB activation of COX-2 gene expression and uterine contractility via ligand-dependent and ligand-independent mechanisms.

Identification of interactive gene networks: a novel approach in gene array profiling of myometrial events during guinea pig pregnancy

OBJECTIVE

The transition from myometrial quiescence to activation is poorly understood, and the analysis of array data is limited by the available data mining tools. We applied functional analysis and logical operations along regulatory gene networks to identify molecular processes and pathways underlying quiescence and activation.

STUDY DESIGN

We analyzed some 18,400 transcripts and variants in guinea pig myometrium at stages corresponding to quiescence and activation, and compared them to the nonpregnant (control) counterpart using a functional mapping tool, MetaCore (GeneGo, St Joseph, MI) to identify novel gene networks composed of biological pathways during mid (MP) and late (LP) pregnancy.

RESULTS

Genes altered during quiescence and or activation were identified following gene specific comparisons with myometrium from nonpregnant animals, and then linked to curated pathways and formulated networks. The MP and LP networks were subtracted from each other to identify unique genomic events during those periods. For example, changes 2-fold or greater in genes mediating protein biosynthesis, programmed cell death, microtubule polymerization, and microtubule based movement were noted during the transition to LP.

CONCLUSION

We describe a novel approach combining microarrays and genetic data to identify networks associated with normal myometrial events. The resulting insights help identify potential biomarkers and permit future targeted investigations of these pathways or networks to confirm or refute their importance.

Gene and protein expression in the myometrium in pregnancy and labor

Microarray technologies widen our comprehension of the major structural and metabolic transformations which affect the myometrium from the very beginning of pregnancy until parturition. The results are coherent with the mass of information which was accumulated previously, primarily on the basis of studies of selected critical factors. They highlight the activation of precise signaling pathways, some of which may have been previously under evaluated. The remodelling and maturation processes that the myometrium undergoes in pregnancy appear clearly as phenomena which last during the full course of gestation. Comparatively, the onset of labor is perhaps the phenomenon which remains the least well described by these methods of analysis. Nevertheless, genomic studies constitute a necessary first step of orientation and help establishing new links between the generic signaling pathways that are activated during the normal or pathological gestation. These studies also represent an indicative step that will have to be paralleled, in the future, with the results of the systematic proteomic analysis of the myometrium.

Transgene Insertion on Mouse Chromosome 6 Impairs Function of the Uterine Cervix and Causes Failure of Parturition1

The molecular mechanisms controlling the initiation of parturition remain largely undefined. We report a new animal model in which parturition does not occur. A line of mice expressing a human apolipoprotein B (APOB) gene fail to deliver their young if the transgene is present in homozygous (Tg/Tg), but not in heterozygous (Tg/Wt), form. Cloning and mapping of the transgene insertion locus indicate that 10 copies of the 80-kilobase APOB genomic fragment inserted into mouse chromosome 6 result in a small, 390-base pair deletion of mouse genomic DNA. Nine other lines expressing the transgene have normal labor, suggesting that transgene insertion in this mutant line disrupted a mouse gene crucial for successful parturition. The pathophysiology of parturition failure in these animals was defined using physiological, endocrinological, and morphological techniques. Results indicate that luteolysis occurs in Tg/Tg mice but is delayed by 1 day. Delivery did not occur in mutant mice at term after spontaneous luteolysis or even after removal of progesterone action by ovariectomy or antiprogestin treatment. Biomechanical and functional studies of the uterus and cervix revealed that the primary cause of failed parturition in Tg/Tg mice was not inadequate uterine contractions of labor but, rather, a rigid, inelastic cervix at term that was abnormally rich in neutrophils and tissue monocytes. Characterization of the transgene insertional mutant, Tg/Tg, indicates that progesterone withdrawal is insufficient to complete parturition in the presence of inadequate cervical ripening at term.

Intraperitoneal infusion of proinflammatory cytokines does not cause activation of the rat uterus during late gestation

Increased concentrations of IL-1beta and TNF-alpha have been associated with parturition. However, the role of these cytokines is unknown. Before parturition, the uterus undergoes a process of activation, during which there are significant changes in expression of genes associated with increased uterine contractility, including the receptors for oxytocin (OT) and prostaglandin (PG)F(2alpha) (FP), PGH(2) synthase isoform 2 (PGHS2), the gap junction protein connexin-43 (Cx-43), and the inducible isoform of nitric oxide synthase (iNOS). To determine whether IL-1beta or TNF-alpha was part of the causal mechanism for increased uterine contractions, we placed osmotic pumps infusing IL-1beta or TNF-alpha into the peritoneal cavity of late pregnant rats (gestation day 19) and measured the effects on uterine contractility and on the uterine concentrations of mRNA for the contraction-associated genes 24 h later. Maternal serum concentrations of IL-1beta and TNF-alpha were increased significantly. By day 21, the control animals had significant increases (P < or = 0.05) in mRNA for OT, FP, PGHS2, and Cx-43, a decrease (P < or = 0.05) in iNOS, and an increase (P < or = 0.05) in uterine sensitivity and responsiveness to OT. Infusion of IL-1beta or TNF-alpha had no effect on uterine contractility or on expression of the activation-associated genes. We conclude that intraperitoneal infusion of IL-1beta or TNF-alpha resulting in significantly increased maternal serum cytokine levels does not cause uterine activation. The role of proinflammatory cytokines in the mechanism of parturition remains unclear.

Identifying genetic networks underlying myometrial transition to labor

BACKGROUND

Early transition to labor remains a major cause of infant mortality, yet the causes are largely unknown. Although several marker genes have been identified, little is known about the underlying global gene expression patterns and pathways that orchestrate these striking changes.

RESULTS

We performed a detailed time-course study of over 9,000 genes in mouse myometrium at defined physiological states: non-pregnant, mid-gestation, late gestation, and postpartum. This dataset allowed us to identify distinct patterns of gene expression that correspond to phases of myometrial 'quiescence', 'term activation', and 'postpartum involution'. Using recently developed functional mapping tools (HOPACH (hierarchical ordered partitioning and collapsing hybrid) and GenMAPP 2.0), we have identified new potential transcriptional regulatory gene networks mediating the transition from quiescence to term activation.

CONCLUSIONS

These results implicate the myometrium as an essential regulator of endocrine hormone (cortisol and progesterone synthesis) and signaling pathways (cyclic AMP and cyclic GMP stimulation) that direct quiescence via the transcriptional upregulation of both novel and previously associated regulators. With term activation, we observe the upregulation of cytoskeletal remodeling mediators (intermediate filaments), cell junctions, transcriptional regulators, and the coordinate downregulation of negative control checkpoints of smooth muscle contractile signaling. This analysis provides new evidence of multiple parallel mechanisms of uterine contractile regulation and presents new putative targets for regulating myometrial transformation and contraction.