New insights into the molecular endocrinology of parturition

Vaginal Progesterone to Prevent Spontaneous Preterm Birth in Women With a Sonographic Short Cervix: The Story of the PREGNANT Trial

The PREGNANT trial was a randomized, placebo-controlled, multicenter trial designed to determine the efficacy and safety of vaginal progesterone (VP) to reduce the risk of birth < 33 weeks and of neonatal complications in women with a sonographic short cervix (10 to 20 mm) in the mid-trimester (19 to 23 6/7 wk). Patients allocated to receive VP had a 45% lower rate of preterm birth (8.9% vs 16.1%; relative risk = 0.55; 95% CI: 0.33-0.92). Neonates born to mothers allocated to VP had a 60% reduction in the rate of respiratory distress syndrome. This article reviews the background, design, execution, interpretation, and impact of the PREGNANT Trial.

The great obstetrical syndromes and the placenta

Although historically pre-eclampsia, preterm birth, abruption, fetal growth restriction and stillbirth have been viewed as clinically distinct entities, a growing body of literature has demonstrated that the placenta and its development is the root cause of many cases of these conditions. This has led to the term 'the great obstetrical syndromes' being coined to reflect this common origin. Although these conditions mostly manifest in the second half of pregnancy, a failure to complete deep placentation (the transition from histiotrophic placentation to haemochorial placenta at 10-18 weeks of gestation via a second wave of extravillous trophoblast invasion), is understood to be key to the pathogenesis of the great obstetrical syndromes. While the reasons that the placenta fails to achieve deep placentation remain active areas of investigation, maternal inflammation and thrombosis have been clearly implicated. From a clinical standpoint these mechanisms provide a biological explanation of how low-dose aspirin, which affects the COX-1 receptor (thrombosis) and the COX-2 receptor (inflammation), prevents not just pre-eclampsia but all the components of the great obstetrical syndromes if initiated early in pregnancy. The optimal dose of low-dose aspirin that is maximally effective in pregnancy remains a question open for further research. Additionally, other candidate medications have been identified that may also prevent pre-eclampsia, and further study of them may offer therapeutic options beyond low-dose aspirin. Interestingly, three of the eight identified compounds (hydroxychloroquine, metformin and pravastatin) are known to decrease inflammation.

Lunar Cycle, Climate, and Onset of Parturition in Domestic Dromedary Camels: Implications of Species-Specific Metabolic Economy and Social Ecology

Given energy costs for gestating and caring for male offspring are higher than those of female newborns, external environmental conditions might be regarded as likely to affect the timing of delivery processes differentially depending on the sex of the newborn calf to be delivered. The aim of the present paper is to evaluate the association between environmental stressors such as the moon phase and weather-related factors and the onset of labor in female dromedaries. A binary logistic regression model was developed to find the most parsimonious set of variables that are most effective in predicting the probability for a gravid female dromedary to give birth to a male or a female calf, assuming that higher gestational costs and longer labor times are ascribed to the production of a male offspring. Although the differences in the quantitative distribution of spontaneous onset of labor across lunar phases and the mean climate per onset event along the whole study period were deemed nonsignificant (p > 0.05), a non-negligible prediction effect of a new moon, mean wind speed and maximum wind gust was present. At slightly brighter nights and lower mean wind speeds, a calf is more likely to be male. This microevolutionary response to the external environment may have been driven by physiological and behavioral adaptation of metabolic economy and social ecology to give birth to cooperative groups with the best possible reduction of thermoregulatory demands. Model performance indexes then highlighted the heterothermic character of camels to greatly minimize the impact of the external environment. The overall results will also enrich the general knowledge of the interplay between homeostasis and arid and semi-arid environments.

Role of intraluteal and intrauterine prostaglandin signaling in LH-induced luteolysis in pregnant rats

Luteal dysfunctions lead to fertility disorders and pregnancy complications. Normal luteal function is regulated by many factors, including luteinizing hormone (LH). The luteotropic roles of LH have been widely investigated but its role in the process of luteolysis has received little attention. LH has been shown to have luteolytic effects during pregnancy in rats and the role of intraluteal prostaglandins (PGs) in LH-mediated luteolysis has been demonstrated by others. However, the status of PG signaling in the uterus during LH-mediated luteolysis remains unexplored. In this study, we utilized the repeated LH administration (4×LH) model for luteolysis induction. We have examined the effect of LH-mediated luteolysis on the expression of genes involved in luteal/uterine PG synthesis, luteal PGF_2α signaling, and uterine activation during different stages (mid and late) of pregnancy. Further, we analyzed the effect of overall PG synthesis machinery blockage on LH-mediated luteolysis during late pregnancy. Unlike the midstage of pregnancy, the expression of genes involved in PG synthesis, PGF_2α signaling, and uterine activation in late-stage pregnant rats' luteal and uterine tissue increase 4×LH. Since the cAMP/PKA pathway mediates LH-mediated luteolysis, we analyzed the effect of inhibition of endogenous PG synthesis on the cAMP/PKA/CREB pathway, followed by the analysis of the expression of markers of luteolysis. Inhibition of endogenous PG synthesis did not affect the cAMP/PKA/CREB pathway. However, in the absence of endogenous PGs, luteolysis could not be activated to the full extent. Our results suggest that endogenous PGs may contribute to LH-mediated luteolysis, but this dependency on endogenous PGs is pregnancy-stage dependent. These findings advance our understanding of the molecular pathways that regulate luteolysis.

Combination of histochemical analyses and micro-MRI reveals regional changes of the murine cervix in preparation for labor

The cervix is responsible for maintaining pregnancy, and its timely remodeling is essential for the proper delivery of a baby. Cervical insufficiency, or "weakness", may lead to preterm birth, which causes infant morbidities and mortalities worldwide. We used a mouse model of pregnancy and term labor, to examine the cervical structure by histology (Masson Trichome and Picrosirius Red staining), immunohistochemistry (Hyaluronic Acid Binding Protein/HABP), and ex-vivo MRI (T2-weighted and diffusion tensor imaging), focusing on two regions of the cervix (i.e., endocervix and ectocervix). Our results show that mouse endocervix has a higher proportion of smooth muscle cells and collagen fibers per area, with more compact tissue structure, than the ectocervix. With advanced gestation, endocervical changes, indicative of impending delivery, are manifested in fewer smooth muscle cells, expansion of the extracellular space, and lower presence of collagen fibers. MRI detected three distinctive zones in pregnant mouse endocervix: (1) inner collagenous layer, (2) middle circular muscular layer, and (3) outer longitudinal muscular layer. Diffusion MRI images detected changes in tissue organization as gestation progressed suggesting the potential application of this technique to non-invasively monitor cervical changes that precede the onset of labor in women at risk for preterm delivery.

Essential Role of Complement in Pregnancy: From Implantation to Parturition and Beyond

The complement cascade was identified over 100 years ago, yet investigation of its role in pregnancy remains an area of intense research. Complement inhibitors at the maternal-fetal interface prevent inappropriate complement activation to protect the fetus. However, this versatile proteolytic cascade also favorably influences numerous stages of pregnancy, including implantation, fetal development, and labor. Inappropriate complement activation in pregnancy can have adverse lifelong sequelae for both mother and child. This review summarizes the current understanding of complement activation during all stages of pregnancy. In addition, consequences of complement dysregulation during adverse pregnancy outcomes from miscarriage, preeclampsia, and pre-term birth are examined. Finally, future research directions into complement activation during pregnancy are considered.

Progesterone Prolongs Viability and Anti-inflammatory Functions of Explanted Preterm Ovine Amniotic Membrane

Amniotic membrane (AM) is considered an important medical device with many applications in regenerative medicine. The therapeutic properties of AM are due to its resistant extracellular matrix and to the large number of bioactive molecules released by its cells. An important goal that still remains to be achieved is the identification of cultural and preservation protocols able to maintain in time the membrane morphology and the biological properties of its cells. Recently, our research group demonstrated that progesterone (P₄) is crucial in preventing the loss of the epithelial phenotype of amniotic epithelial cells in vitro. Followed by this premise, it has been evaluated whether P₄ may also affect AM properties in a short-term culture. Results confirm that P₄ preserves AM integrity and architecture with respect to untreated AM, which showed alterations in morphology. Transmission electron microscopy (TEM) analyses demonstrate that P₄ also maintains unaltered cell-cell junctions, nuclear status, and intracellular organelles. On the contrary, an untreated AM experienced an extensive cell death and a strong reduction of immunomodulatory properties, measured in terms of anti-inflammatory cytokine expression and secretion. Overall, these results could open to new strategies to ameliorate the protocols for cryopreservation and tissue culture, which represent preliminary stages of AM application in regenerative medicine.

Mouse models of preterm birth: suggested assessment and reporting guidelines

Preterm birth affects approximately 1 out of every 10 births in the United States, leading to high rates of mortality and long-term negative health consequences. To investigate the mechanisms leading to preterm birth so as to develop prevention strategies, researchers have developed numerous mouse models of preterm birth. However, the lack of standard definitions for preterm birth in mice limits our field's ability to compare models and make inferences about preterm birth in humans. In this review, we discuss numerous mouse preterm birth models, propose guidelines for experiments and reporting, and suggest markers that can be used to assess whether pups are premature or mature. We argue that adoption of these recommendations will enhance the utility of mice as models for preterm birth.

Cellular immune responses in amniotic fluid of women with preterm labor and intra-amniotic infection or intra-amniotic inflammation

PROBLEM

Preterm birth is commonly preceded by preterm labor, a syndrome that is causally linked to both intra-amniotic infection and intra-amniotic inflammation. However, the stereotypical cellular immune responses in these two clinical conditions are poorly understood.

METHOD OF STUDY

Amniotic fluid samples (n = 26) were collected from women diagnosed with preterm labor and intra-amniotic infection (amniotic fluid IL-6 concentrations ≥2.6 ng/mL and culturable microorganisms, n = 10) or intra-amniotic inflammation (amniotic fluid IL-6 concentrations ≥2.6 ng/mL without culturable microorganisms, n = 16). Flow cytometry was performed to evaluate the phenotype and number of amniotic fluid leukocytes. Amniotic fluid concentrations of classical pro-inflammatory cytokines, type 1 and type 2 cytokines, and T-cell chemokines were determined using immunoassays.

RESULTS

Women with spontaneous preterm labor and intra-amniotic infection had (a) a greater number of total leukocytes, including neutrophils and monocytes/macrophages, in amniotic fluid; (b) a higher number of total T cells and CD4⁺ T cells, but not CD8⁺ T cells or B cells, in amniotic fluid; and (c) increased amniotic fluid concentrations of IL-6, IL-1β, and IL-10, compared to those with intra-amniotic inflammation. However, no differences in amniotic fluid concentrations of T-cell cytokines and chemokines were observed between these two clinical conditions.

CONCLUSION

The cellular immune responses observed in women with preterm labor and intra-amniotic infection are more severe than in those with intra-amniotic inflammation, and neutrophils, monocytes/macrophages, and CD4⁺ T cells are the main immune cells responding to microorganisms that invade the amniotic cavity. These findings provide insights into the intra-amniotic immune mechanisms underlying the human syndrome of preterm labor.

Evaluation of serum C-reactive protein concentration as a marker of impending parturition and correlation with progesterone profile in peri-partum bitches

C-reactive protein (CRP) is one of the major acute phase proteins in dogs. It is produced by the liver and rapidly increases in response to an inflammatory stimulus. The aim of this study was to measure CRP concentrations around parturition and to verify whether this protein could be useful, together with progesterone (P), to detect the onset of parturition in bitches. The CRP and P concentrations were measured in 66 serum samples from 28 healthy pregnant bitches, collected between -5 and +2 days from parturition (day of parturition = day 0). The effect of 'days from parturition', parity, and litter size on P and CRP concentration was analyzed and the correlation between CRP and P values was calculated. The P and CRP values were affected by 'days from parturition'. While P decreased during the last days of pregnancy, CRP concentration was greater than the normal range (0-1.07 mg/dl) starting the parturition day with the increase starting on day -1. The CRP concentration profiles during the days around parturition have not been previously reported in dogs. The increase in CRP very near the time of parturition and the low magnitude of the increase do not allow for it to be useful in clinical practice to assess the onset of parturition in the bitch.

Vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix: a meta-analysis of individual patient data

BACKGROUND

The efficacy of vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix has been questioned after publication of the OPPTIMUM study.

OBJECTIVE

To determine whether vaginal progesterone prevents preterm birth and improves perinatal outcomes in asymptomatic women with a singleton gestation and a midtrimester sonographic short cervix.

STUDY DESIGN

We searched MEDLINE, EMBASE, LILACS, and CINAHL (from their inception to September 2017); Cochrane databases; bibliographies; and conference proceedings for randomized controlled trials comparing vaginal progesterone vs placebo/no treatment in women with a singleton gestation and a midtrimester sonographic cervical length ≤25 mm. This was a systematic review and meta-analysis of individual patient data. The primary outcome was preterm birth <33 weeks of gestation. Secondary outcomes included adverse perinatal outcomes and neurodevelopmental and health outcomes at 2 years of age. Individual patient data were analyzed using a 2-stage approach. Pooled relative risks with 95% confidence intervals were calculated. Quality of evidence was assessed using the GRADE methodology.

RESULTS

Data were available from 974 women (498 allocated to vaginal progesterone, 476 allocated to placebo) with a cervical length ≤25 mm participating in 5 high-quality trials. Vaginal progesterone was associated with a significant reduction in the risk of preterm birth <33 weeks of gestation (relative risk, 0.62; 95% confidence interval, 0.47-0.81; P = .0006; high-quality evidence). Moreover, vaginal progesterone significantly decreased the risk of preterm birth <36, <35, <34, <32, <30, and <28 weeks of gestation; spontaneous preterm birth <33 and <34 weeks of gestation; respiratory distress syndrome; composite neonatal morbidity and mortality; birthweight <1500 and <2500 g; and admission to the neonatal intensive care unit (relative risks from 0.47-0.82; high-quality evidence for all). There were 7 (1.4%) neonatal deaths in the vaginal progesterone group and 15 (3.2%) in the placebo group (relative risk, 0.44; 95% confidence interval, 0.18-1.07; P = .07; low-quality evidence). Maternal adverse events, congenital anomalies, and adverse neurodevelopmental and health outcomes at 2 years of age did not differ between groups.

CONCLUSION

Vaginal progesterone decreases the risk of preterm birth and improves perinatal outcomes in singleton gestations with a midtrimester sonographic short cervix, without any demonstrable deleterious effects on childhood neurodevelopment.

Progestin withdrawal at parturition in the mare

Mammalian pregnancies need progestogenic support and birth requires progestin withdrawal. The absence of progesterone in pregnant mares, and the progestogenic bioactivity of 5α-dihydroprogesterone (DHP), led us to reexamine progestin withdrawal at foaling. Systemic pregnane concentrations (DHP, allopregnanolone, pregnenolone, 5α-pregnane-3β, 20α-diol (3β,20αDHP), 20α-hydroxy-5α-dihydroprogesterone (20αDHP)) and progesterone) were monitored in mares for 10days before foaling (n=7) by liquid chromatography-mass spectrometry. The biopotency of dominant metabolites was assessed using luciferase reporter assays. Stable transfected Chinese hamster ovarian cells expressing the equine progesterone receptor (ePGR) were transfected with an MMTV-luciferase expression plasmid responsive to steroid agonists. Cells were incubated with increasing concentrations (0-100nM) of progesterone, 20αDHP and 3α,20βDHP. The concentrations of circulating pregnanes in periparturient mares were (highest to lowest) 3α,20βDHP and 20αDHP (800-400ng/mL respectively), DHP and allopregnanolone (90 and 30ng/mL respectively), and pregnenolone and progesterone (4-2ng/mL). Concentrations of all measured pregnanes declined on average by 50% from prepartum peaks to the day before foaling. Maximum activation of the ePGR by progesterone occurred at 30nM; 20αDHP and 3α,20βDHP were significantly less biopotent. At prepartum concentrations, both 20αDHP and 3α,20βDHP exhibited significant ePGR activation. Progestogenic support of pregnancy declines from 3 to 5days before foaling. Prepartum peak concentrations indicate that DHP is the major progestin, but other pregnanes like 20αDHP are present in sufficient concentrations to play a physiological role in the absence of DHP. The authors conclude that progestin withdrawal associated with parturition in mares involves cessation of pregnane synthesis by the placenta.

Progesterone prevents epithelial-mesenchymal transition of ovine amniotic epithelial cells and enhances their immunomodulatory properties

The in vitro expansion is detrimental to therapeutic applications of amniotic epithelial cells (AEC), an emerging source of fetal stem cells. This study provides molecular evidences of progesterone (P4) role in preventing epithelial-mesenchymal transition (EMT) in ovine AEC (oAEC). oAEC amplified under standard conditions spontaneously acquired mesenchymal properties through the up-regulation of EMT-transcription factors. P4 supplementation prevented phenotype shift by inhibiting the EMT-inducing mechanism such as the autocrine production of TGF-β and the activation of intracellular-related signaling. The effect of P4 still persisted for one passage after steroid removal from culture as well as steroid supplementation promptly reversed mesenchymal phenotype in oAEC which have experienced EMT during amplification. Furthermore, P4 promoted an acute up-regulation of pluripotent genes whereas enhanced basal and LPS-induced oAEC anti-inflammatory response with an increase in anti-inflammatory and a decrease in pro-inflammatory cytokines expression. Altogether, these results indicate that P4 supplementation is crucial to preserve epithelial phenotype and to enhance biological properties in expanded oAEC. Therefore, an innovative cultural approach is proposed in order to improve therapeutic potential of this promising source of epithelial stem cells.

Analysis of Free Hemoglobin Level and Hemoglobin Peptides from Human Puerperal Uterine Secretions

OBJECTIVE

Hemocidins are a novel class of antibacterial peptides generated proteolytically from hemoglobin. These peptides play a particularly important role in maintaining vaginal homeostasis during menstrual bleeding. To investigate the hemoglobin fragmentation process during the last stages of pregnancy, we examined uterine secretion (lochia) samples from a group of 22 healthy women who underwent cesarean delivery at term.

METHODS

Patients were divided into three groups: (1) the elective cesarean deliveries without symptoms of spontaneous labor, (2) the nonelective cesarean deliveries with spontaneous beginning of labor, and (3) the nonelective cesarean deliveries during advanced labor. The samples were subjected to chromatographic estimation of free hemoglobin and peptides. In three representative patients the identification of all lochial peptides was performed.

RESULTS

All samples contained a significant amount of free hemoglobin and its level increased with labor progression. The presence of peptide fractions was also detected in most lochia samples. They were confirmed to be human hemoglobin fragments, almost identical to the recently described bactericidal hemocidins from menstrual discharge. The level of peptides also increased during labor. The subgroup with advanced labor demonstrated the highest amount of hemocidins.

CONCLUSIONS

The presented results prove that proteolysis of free hemoglobin in the female upper reproductive tract begins together with the clinical symptoms of normal labor. We speculate that cesarean delivery affects molecular mechanisms involved in antibacterial hemocidins generation and, in effect, might be responsible for the increased risk of gynecologic infections in cesarean deliveries.

Role of collectins and complement protein C1q in pregnancy and parturition

Collectins such as surfactant proteins SP-A, SP-D, and mannan-binding lectin (MBL), as well as complement protein C1q are evolutionarily conserved innate immune molecules. They are known to opsonize a range of microbial pathogens (bacteria, fungi, virus, and parasites) and trigger effector clearance mechanisms involving phagocytosis and/or complement activation. Collectins and C1q have also attracted attention in studies involving pregnancy as they are expressed in the female reproductive tissues during pregnancy; a unique state of immune suppression with increased susceptibility to infectious diseases. Recent studies are beginning to unravel their functional significance in implantation, placentation, pregnancy maintenance and parturition in normal and adverse pregnancies. Collectins and C1q, expressed in gestational tissues during pregnancy, might alter the status of mother's immune response to the allogenic fetus and the microenvironment, thereby serving as important regulators of fetus-mother interaction. Here, we discuss the functional roles that have been assigned to SP-A, SP-D, MBL and C1q in pregnancy and parturition.

A Cross-Species Analysis of Animal Models for the Investigation of Preterm Birth Mechanisms

BACKGROUND

Spontaneous preterm birth is the leading cause of neonatal morbidity and mortality worldwide. The ability to examine the exact mechanisms underlying this syndrome in humans is limited. Therefore, the study of animal models is critical to unraveling the key physiologic mechanisms that control the timing of birth. The purpose of this review is to facilitate enhanced assimilation of the literature on animal models of preterm birth by a broad range of investigators.

METHODS

Using classical systematic and informatics search techniques of the available literature through 2012, a database of intact animal models was generated. Research librarians generated a list of articles using multiple databases. From these articles, a comprehensive list of Medical Subject Headings (MeSH) was created. Using mathematical modeling, significant MeSH descriptors were determined, and a MEDLINE search algorithm was created. The articles were reviewed for mechanism of labor induction categorized by species.

RESULTS

Existing animal models of preterm birth comprise specific interventions to induce preterm birth, as no animal model was identified that exhibits natural spontaneous preterm birth at an incidence comparable to that of the humans. A search algorithm was developed which when used results in a comprehensive list of agents used to induce preterm delivery in a host of animal species. The evolution of 3 specific animal models--sheep, mice, and rats--has demonstrated a clear shift in focus in the literature from endocrine to inflammatory agents of preterm birth induction.

CONCLUSION

The process of developing a search algorithm to provide efficient access to information on animal models of preterm birth illustrates the need for a more precise organization of the literature to allow the investigator to focus on distinctly maternal versus fetal outcomes.

Molecular Regulation of Parturition: A Myometrial Perspective

The molecular mechanisms that maintain quiescence of the myometrium throughout most of pregnancy and promote its transformation to a highly coordinated contractile unit culminating in labor are complex and intertwined. During pregnancy, progesterone (P4) produced by the placenta and/or ovary serves a dominant role in maintaining myometrial quiescence by blocking proinflammatory response pathways and expression of so-called "contractile" genes. In the majority of placental mammals, increased uterine contractility near term is heralded by an increase in circulating estradiol-17β (E2) and/or increased estrogen receptor α (ERα) activity and a sharp decline in circulating P4 levels. However, in women, circulating levels of P4 and progesterone receptors (PR) in myometrium remain elevated throughout pregnancy and into labor. This has led to the concept that increased uterine contractility leading to term and preterm labor is mediated, in part, by a decline in PR function. The biochemical mechanisms for this decrease in PR function are also multifaceted and interwoven. In this paper, we focus on the molecular mechanisms that mediate myometrial quiescence and contractility and their regulation by the two central hormones of pregnancy, P4 and estradiol-17β. The integrative roles of microRNAs also are considered.

Functional and morphological development of the womb throughout life

The uterus undergoes changes throughout a woman's life, beginning with her own embryonic development when she is still in the womb, commencing a monthly cycle at the onset of adulthood, and undergoing dramatic changes during pregnancy and parturition. The impact of preterm labour and other perinatal health problems is significant, both in human and financial terms; therefore the study of the physiological and regulatory changes which the uterus undergoes can be of enormous potential benefit. Here we briefly review the current state of knowledge, with an emphasis on the importance of changes in connectivity in the uterine smooth muscle cell network and on recent mathematical modelling work aimed at elucidating the role of spatial heterogeneity in this connected network.

Antimicrobial peptides in the female reproductive tract: a critical component of the mucosal immune barrier with physiological and clinical implications

BACKGROUND

At the interface of the external environment and the mucosal surface of the female reproductive tract (FRT) lies a first-line defense against pathogen invasion that includes antimicrobial peptides (AMP). Comprised of a unique class of multifunctional, amphipathic molecules, AMP employ a wide range of functions to limit microbial invasion and replication within host cells as well as independently modulate the immune system, dampen inflammation and maintain tissue homeostasis. The role of AMP in barrier defense at the level of the skin and gut has received much attention as of late. Given the far reaching implications for women's health, maternal and fetal morbidity and mortality, and sexually transmissible and polymicrobial diseases, we herein review the distribution and function of key AMP throughout the female reproductive mucosa and assess their role as an essential immunological barrier to microbial invasion throughout the reproductive cycle of a woman's lifetime.

METHODS

A comprehensive search in PubMed/Medline was conducted related to AMP general structure, function, signaling, expression, distribution and barrier function of AMP in the FRT, hormone regulation of AMP, the microbiome of the FRT, and AMP in relation to implantation, pregnancy, fertility, pelvic inflammatory disease, complications of pregnancy and assisted reproductive technology.

RESULTS

AMP are amphipathic peptides that target microbes for destruction and have been conserved throughout all living organisms. In the FRT, several major classes of AMP are expressed constitutively and others are inducible at the mucosal epithelium and by immune cells. AMP expression is also under the influence of sex hormones, varying throughout the menstrual cycle, and dependent on the vaginal microbiome. AMP can prevent infection with sexually transmissible and opportunistic pathogens of the female reproductive tissues, although emerging understanding of vaginal dysbiosis suggests induction of a unique AMP profile with increased susceptibility to these pathogens. During pregnancy, AMP are key immune effectors of the fetal membranes and placenta and are dysregulated in states of intrauterine infection and other complications of pregnancy.

CONCLUSIONS

At the level of the FRT, AMP serve to inhibit infection by sexually and vertically transmissible as well as by opportunistic bacteria, fungi, viruses, and protozoa and must do so throughout the hormone flux of menses and pregnancy. Guarding the exclusive site of reproduction, AMP modulate the vaginal microbiome of the lower FRT to aid in preventing ascending microbes into the upper FRT. Evolving in parallel with, and in response to, pathogenic insults, AMP are relatively immune to the resistance mechanisms employed by rapidly evolving pathogens and play a key role in barrier function and host defense throughout the FRT.

Uterine endoplasmic reticulum stress and its unfolded protein response may regulate caspase 3 activation in the pregnant mouse uterus

We have previously proposed that uterine caspase-3 may modulate uterine contractility in a gestationally regulated fashion. The objective of this study was to determine the mechanism by which uterine caspase-3 is activated and consequently controlled in the pregnant uterus across gestation. Utilizing the mouse uterus as our gestational model we examined the intrinsic and extrinsic apoptotic signaling pathways and the endoplasmic reticulum stress response as potential activators of uterine caspase-3 at the transcriptional and translational level. Our study revealed robust activation of the uterine myocyte endoplasmic reticulum stress response and its adaptive unfolded protein response during pregnancy coinciding respectively with increased uterine caspase-3 activity and its withdrawal to term. In contrast the intrinsic and extrinsic apoptotic signaling pathways remained inactive across gestation. We speculate that physiological stimuli experienced by the pregnant uterus likely potentiates the uterine myocyte endoplasmic reticulum stress response resulting in elevated caspase-3 activation, which is isolated to the pregnant mouse myometrium. However as term approaches, activation of an elevated adaptive unfolded protein response acts to limit the endoplasmic reticulum stress response inhibiting caspase-3 resulting in its decline towards term. We speculate that these events have the capacity to regulate gestational length in a caspase-3 dependent manner.

Dietary phytophenols curcumin, naringenin and apigenin reduce infection-induced inflammatory and contractile pathways in human placenta, foetal membranes and myometrium

A tenet of contemporary obstetrics is that a significant proportion of preterm births involve bacterial infection. Bacterial endotoxin induces pro-inflammatory cytokines, prostaglandins and proteases via the pro-inflammatory pathway nuclear factor-κB (NF-κB), which plays a key role in initiating uterine contractions and rupture of foetal membranes. In non-gestational tissues, the phytophenols curcumin, naringenin and apigenin exert anti-inflammatory properties via inhibition of NF-κB. The aim of this study was to determine whether these treatments regulate pro-inflammatory and pro-labour mediators in human gestational tissues. Placenta, foetal membranes and myometrium were treated with curcumin, naringenin and apigenin in the presence of lipopolysaccharide (LPS) or interleukin (IL)-1β. In placenta and foetal membranes, all treatments significantly reduced LPS-stimulated release and gene expression of pro-inflammatory cytokines IL-6 and IL-8; placenta decreased cyclooxygenase (COX-2) mRNA expression, subsequent release of prostaglandins PGE2 and PGF2α and expression and activity of matrix-degrading enzyme matrix metalloproteinase (MMP)-9. In myometrial cells, all treatments attenuated IL-1β-induced COX-2 expression, release of PGE2 and PGF2α and expression and activity of MMP-9. Although naringenin significantly attenuated IL-1β-induced IL-6 and IL-8 mRNA expression and release, there was no effect of curcumin and apigenin. LPS-stimulated release of 8-isoprostane, a marker of oxidative stress, was attenuated by all treatments. NF-κB p65 DNA-binding activity was also decreased using these treatments. In conclusion, curcumin, naringenin and apigenin exert anti-inflammatory properties in human gestational tissues by inhibiting the transcriptional activity of NF-κB. Further studies should be undertaken to define a possible implication of these natural spices in the management of preterm labour and delivery.

Demystifying animal models of adverse pregnancy outcomes: touching bench and bedside

This represents an overview of the use of animal models to study the adverse pregnancy outcomes seen in humans. The purpose is to entice clinicians to utilize some of this information to seek out the literature and have more meaningful and profitable discussions with their academic colleagues and enhance transdisciplinary research in reproductive health.

Mice deficient in surfactant protein A (SP-A) and SP-D or in TLR2 manifest delayed parturition and decreased expression of inflammatory and contractile genes

Previously we obtained compelling evidence that the fetus provides a critical signal for the initiation of term labor through developmental induction of surfactant protein (SP)-A expression by the fetal lung and secretion into amniotic fluid (AF). We proposed that interactions of AF macrophage (Mϕ) Toll-like receptors (TLRs) with SP-A, at term, or bacterial components, at preterm, result in their activation and migration to the pregnant uterus. Herein the timing of labor in wild-type (WT) C57BL/6 mice was compared with mice homozygous null for TLR2, SP-A, SP-D, or doubly deficient in SP-A and SP-D. Interestingly, TLR2(-/-) females manifested a significant (P < 0.001) delay in timing of labor compared with WT as well as reduced expression of the myometrial contraction-associated protein (CAP) gene, connexin-43, and Mϕ marker, F4/80, at 18.5 d postcoitum (dpc). Whereas in first pregnancies, SP-A(-/-), SP-D(-/-), and SP-A/D(-/-) females delivered at term (∼19.5 dpc), in second pregnancies, parturition was delayed by approximately 12 h in SP-A(-/-) (P = 0.07) and in SP-A/D(-/-) (P <0.001) females. Myometrium of SP-A/D(-/-) females expressed significantly lower levels of IL-1β, IL-6, and CAP genes, connexin-43, and oxytocin receptor at 18.5 dpc compared with WT. F4/80(+) AF Mϕs from TLR2(-/-) and SP-A/D(-/-) mice expressed significantly lower levels of both proinflammatory and antiinflammatory activation markers (e.g. IL-1β, IL-6, ARG1, YM1) compared with gestation-matched WT AF Mϕs. These novel findings suggest that the pulmonary collectins acting via TLR2 serve a modulatory role in the timing of labor; their relative impact may be dependent on parity.

Spontaneous abortion and preterm labor and delivery in nonhuman primates: evidence from a captive colony of chimpanzees (Pan troglodytes)

BACKGROUND

Preterm birth is a leading cause of perinatal mortality, yet the evolutionary history of this obstetrical syndrome is largely unknown in nonhuman primate species.

METHODOLOGY/PRINCIPAL FINDINGS

We examined the length of gestation during pregnancies that occurred in a captive chimpanzee colony by inspecting veterinary and behavioral records spanning a total of thirty years. Upon examination of these records we were able to confidently estimate gestation length for 93 of the 97 (96%) pregnancies recorded at the colony. In total, 78 singleton gestations resulted in live birth, and from these pregnancies we estimated the mean gestation length of normal chimpanzee pregnancies to be 228 days, a finding consistent with other published reports. We also calculated that the range of gestation in normal chimpanzee pregnancies is approximately forty days. Of the remaining fifteen pregnancies, only one of the offspring survived, suggesting viability for chimpanzees requires a gestation of approximately 200 days. These fifteen pregnancies constitute spontaneous abortions and preterm deliveries, for which the upper gestational age limit was defined as 2 SD from the mean length of gestation (208 days).

CONCLUSIONS/SIGNIFICANCE

The present study documents that preterm birth occurred within our study population of captive chimpanzees. As in humans, pregnancy loss is not uncommon in chimpanzees, In addition, our findings indicate that both humans and chimpanzees show a similar range of normal variation in gestation length, suggesting this was the case at the time of their last common ancestor (LCA). Nevertheless, our data suggest that whereas chimpanzees' normal gestation length is ∼20-30 days after reaching viability, humans' normal gestation length is approximately 50 days beyond the estimated date of viability without medical intervention. Future research using a comparative evolutionary framework should help to clarify the extent to which mechanisms at work in normal and preterm parturition are shared in these species.

Inflammatory gene regulatory networks in amnion cells following cytokine stimulation: translational systems approach to modeling human parturition

A majority of the studies examining the molecular regulation of human labor have been conducted using single gene approaches. While the technology to produce multi-dimensional datasets is readily available, the means for facile analysis of such data are limited. The objective of this study was to develop a systems approach to infer regulatory mechanisms governing global gene expression in cytokine-challenged cells in vitro, and to apply these methods to predict gene regulatory networks (GRNs) in intrauterine tissues during term parturition. To this end, microarray analysis was applied to human amnion mesenchymal cells (AMCs) stimulated with interleukin-1β, and differentially expressed transcripts were subjected to hierarchical clustering, temporal expression profiling, and motif enrichment analysis, from which a GRN was constructed. These methods were then applied to fetal membrane specimens collected in the absence or presence of spontaneous term labor. Analysis of cytokine-responsive genes in AMCs revealed a sterile immune response signature, with promoters enriched in response elements for several inflammation-associated transcription factors. In comparison to the fetal membrane dataset, there were 34 genes commonly upregulated, many of which were part of an acute inflammation gene expression signature. Binding motifs for nuclear factor-κB were prominent in the gene interaction and regulatory networks for both datasets; however, we found little evidence to support the utilization of pathogen-associated molecular pattern (PAMP) signaling. The tissue specimens were also enriched for transcripts governed by hypoxia-inducible factor. The approach presented here provides an uncomplicated means to infer global relationships among gene clusters involved in cellular responses to labor-associated signals.

Toll-like receptors in pregnancy disorders and placental dysfunction

The Toll receptor was originally identified as a regulator of embryogenesis in Drosophila. Toll-like receptors (TLRs) in mammals recognize infectious agents and other danger signals. Activation of TLRs on trophoblast influences immune cell recruitment, cytokine secretion, and decidual responses to invading pathogens during pregnancy. Importantly, biological effects of TLR signal transduction at multiple maternal-fetal interfaces may contribute to several pregnancy pathologies associated with placental dysfunction, including pre-eclampsia, intrauterine growth restriction, and preterm labor. We herein discuss mechanisms by which TLRs regulate the maternal immune response during normal and abnormal gestation, and we highlight recent data that assign a role to TLRs in the pathophysiology of selected pregnancy-associated complications.

Secreted surfactant protein A from fetal membranes induces stress fibers in cultured human myometrial cells

In the present study, we investigated the ability of human fetal membranes (amnion and choriodecidua) to regulate human maternal uterine cell functions through the secretion of surfactant protein (SP)-A and SP-D at the end of pregnancy. We detected the expression of both SP-A (SP-A1 and SP-A2) and SP-D by quantitative reverse transcription polymerase chain reaction. Immunohistochemistry revealed that human fetal membranes expressed both SP-A and SP-D. By Western blot analysis, we demonstrated that SP-A protein expression was predominant in choriodecidua, whereas the amnion predominantly expressed SP-D. Only the secretion of SP-A was evidenced in the culture supernatants of amnion and choriodecidua explants by immunodot blot and confirmed by Western blot. Exogenous human purified SP-A induced stress fiber formation in cultured human myometrial cells via a pathway involving Rho-kinase. Conditioned medium from choriodecidua and amnion explants mimicked the SP-A effect. Treatment of myometrial cells with SP-A-depleted conditioned medium from choriodecidua or amnion explants failed to change the actin dynamic. These data indicate that SP-A released by human fetal membranes is able to exert a paracrine regulation of F-actin filament organization in myometrial cells.

Surfactant protein-A as an anti-inflammatory component in the amnion: implications for human pregnancy

The mechanism of mouse parturition is thought to involve myometrial infiltration by amniotic fluid (AF) macrophages, activated by surfactant protein-A (SP-A). In humans, the concentration of AF SP-A decreases during labor, and no fetal macrophages are found in the myometrium after labor. Therefore, it appears that the mechanisms of labor in mice and humans are different. We investigated a potential role for SP-A in human pregnancy and parturition by examining SP-A expression patterns in AF and amnion. High molecular mass (>250 kDa) oligomeric SP-A was increased in AF with advancing gestation. Interestingly, these oligomers were more abundant in placental amnion before labor at term, while they increased primarily in reflected amnion during labor (p < 0.05). Immunoblotting showed a binding of high molecular mass SP-A in AF to amnion. In C57BL/6 mice, oligomeric SP-A was also readily detected in AF from E15 onwards, but not in amnion. Macrophage density in mice myometrium did not change with advancing gestational age. Microarray analysis of human amnion explants incubated with SP-A revealed a molecular signature of inhibited cytokine-cytokine receptor interaction with downregulation of IL-1beta, CXCL2, and CXCL5 mRNA expression. The findings in this study strongly suggest that SP-A signals amniotic anti-inflammatory response via AF during pregnancy. We propose that an SP-A interaction among AF, placental amnion, and reflected amnion is a unique mechanism for immunoregulation in human pregnancy akin to that established in lung biology. However, AF SP-A and fetal macrophages by themselves do not seem to be exclusive effectors of parturition in humans.

Critical appraisal and clinical utility of atosiban in the management of preterm labor

Preterm birth is the major cause of perinatal morbidity and mortality in the developed world, and spontaneous preterm labor is the commonest cause of preterm birth. Interventions to treat women in spontaneous preterm labor have not reduced the incidence of preterm births but this may be due to increased risk factors, inclusion of births at the limits of viability, and an increase in the use of elective preterm birth. The role of antibiotics remains unproven. In the largest of the randomized controlled trials, evaluating the use of antibiotics for the prevention of preterm births in women in spontaneous preterm labor, antibiotics against anaerobes and bacterial vaginosis-related organisms were not included, and no objective evidence of abnormal genital tract flora was obtained. Atosiban and nifedipine are the main tocolytic agents used to treat women in spontaneous preterm labor, but atosiban is the tocolytic agent with the fewest maternal - fetal side effects. A well conducted randomized controlled trial comparing atosiban with nifedipine for their effectiveness and safety is needed.

Nuclear factor-kappa B localization and function within intrauterine tissues from term and preterm labor and cultured fetal membranes

BACKGROUND

The objective of this study was to quantify the nuclear localization and DNA binding activity of p65, the major transactivating nuclear factor-kappa B (NF-kappaB) subunit, in full-thickness fetal membranes (FM) and myometrium in the absence or presence of term or preterm labor.

METHODS

Paired full-thickness FM and myometrial samples were collected from women in the following cohorts: preterm no labor (PNL, N = 22), spontaneous preterm labor (PTL, N = 21), term no labor (TNL, N = 23), and spontaneous term labor (STL, N = 21). NF-kappaB p65 localization was assessed by immunohistochemistry, and DNA binding activity was evaluated using an enzyme-linked immunosorbent assay (ELISA)-based method.

RESULTS

Nuclear p65 labeling was rare in amnion and chorion, irrespective of clinical context. In decidua, nuclear p65 labeling was greater in the STL group relative to the TNL cohort, but there were no differences among the TNL, PTL, and PNL cohorts. In myometrium, diffuse p65 nuclear labeling was significantly associated with both term and preterm labor. There were no significant differences in ELISA-based p65 binding activity in amnion, choriodecidual, and myometrial specimens in the absence or presence of term labor. However, parallel experiments using cultured term fetal membranes demonstrated high levels of p65-like binding even the absence of cytokine stimulation, suggesting that this assay may be of limited value when applied to tissue specimens.

CONCLUSIONS

These results suggest that the decidua is an important site of NF-kappaB regulation in fetal membranes, and that mechanisms other than cytoplasmic sequestration may limit NF-kappaB activation prior to term.

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.

The cyclopentenone 15-deoxy-delta 12,14-prostaglandin J(2) delays lipopolysaccharide-induced preterm delivery and reduces mortality in the newborn mouse

Intrauterine infection is a common trigger for preterm birth and is also a risk factor for the subsequent development of neurodevelopmental abnormalities in the neonate. Bacterial lipopolysaccharide (LPS) binds to toll-like receptor-4 (TLR-4) to activate proinflammatory signaling pathways, which are implicated in both preterm delivery and antenatal brain injury. The transcription factor nuclear factor-kappaB (NF-kappaB) is a key player in the orchestration of the inflammatory response and has a central role in parturition. Here we show that intrauterine administration of TLR-4-specific LPS to pregnant mice results in the activation of NF-kappaB in the maternal uterus and the fetal brain, up-regulation of proinflammatory proteins cyclooxygenase-2, chemokine ligand 1, ChemoKine (C-C motif) ligand 2, and cytosolic phospholipase A(2) in myometrium, and induction of preterm delivery. 15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) is an antiinflammatory prostaglandin that plays a role in promoting the resolution of inflammation. We report that coadministration of 15d-PGJ(2) and LPS to pregnant mice delays LPS-induced preterm delivery and confers protection from LPS-induced fetal mortality. This is associated with inhibition of myometrial NF-kappaB, cytosolic phospholipase A(2), and c-Jun N-terminal kinase activation, and of inflammatory protein synthesis. Therefore 15d-PGJ(2) has anti-inflammatory effects via inhibition of multiple aspects of inflammation-driven TRL-4 signaling pathway. Thus, 15d-PGJ(2) or compounds with similar antiinflammatory functions may have potential as therapeutic agents in the management of preterm labor with the added advantage of preventing detrimental effects to the fetus that may result from infection/inflammation.

The concentration of surfactant protein-A in amniotic fluid decreases in spontaneous human parturition at term

OBJECTIVE

The fetus is thought to play a central role in the onset of labor. Pulmonary surfactant protein (SP)-A, secreted by the maturing fetal lung, has been implicated in the mechanisms initiating parturition in mice. The present study was conducted to determine whether amniotic fluid concentrations of SP-A and SP-B change during human parturition.

STUDY DESIGN

Amniotic fluid SP-A and SP-B concentrations were measured with a sensitive and specific ELISA in the following groups of pregnant women: (1) mid-trimester of pregnancy, between 15 and 18 weeks of gestation (n = 29), (2) term pregnancy not in labor (n = 28), and (3) term pregnancy in spontaneous labor (n = 26). Non-parametric statistics were used for analysis.

RESULTS

SP-A was detected in all amniotic fluid samples. SP-B was detected in 24.1% (7/29) of mid-trimester samples and in all samples at term. The median amniotic fluid concentrations of SP-A and SP-B were significantly higher in women at term than in women in the mid-trimester (SP-A term no labor: median 5.6 microg/mL, range 2.2-15.2 microg/mL vs. mid-trimester: median 1.64 microg/mL, range 0.1-4.7 microg/mL, and SP-B term no labor: median 0.54 microg/mL, range 0.17-1.99 microg/mL vs. mid-trimester: median 0 microg/mL, range 0-0.35 microg/mL; both p < 0.001). The median amniotic fluid SP-A concentration in women at term in labor was significantly lower than that in women at term not in labor (term in labor: median 2.7 microg/mL, range 1.2-10.1 microg/mL vs. term no labor: median 5.6 microg/mL, range 2.2-15.2 microg/mL; p < 0.001). There was no significant difference in the median amniotic fluid SP-B concentrations between women in labor and those not in labor (term in labor: median 0.47 microg/mL, range 0.04-1.32 microg/mL vs. term no labor: median 0.54 microg/mL, range 0.17-1.99 microg/mL; p = 0.2).

CONCLUSION

The amniotic fluid concentration of SP-A decreases in spontaneous human parturition at term.

Angiogenesis gene expression in mouse uterus during the common pathway of parturition

OBJECTIVE

The objective of the study was to investigate changes in the expression of angiogenesis-related genes during the common terminal pathway of parturition including spontaneous labor at term, as well as preterm labor (PTL), induced by either bacteria or ovariectomy.

STUDY DESIGN

Preterm pregnant mice (14.5 days of gestation) were treated with the following: (1) intrauterine injection of media; (2) intrauterine injection of heat-inactivated Escherichia coli; (3) ovariectomy; and (4) sham operation. Tissues from mice at term (19.5 days of gestation) were collected at term not in labor, term in labor, and 12 hours postpartum. Angiogenesis-related gene expression levels were quantitated by the measurement of specific mRNAs in uterine tissue by RT-qPCR and analyzed by repeated-measures analysis of variance.

RESULTS

The following results were found: (1) microarray analysis of the uterine transcriptome indicated an enrichment for the gene ontology category of angiogenesis in bacteria-induced PTL samples (P < or = .093); (2) several genes related to angiogenesis demonstrated significantly increased expression in samples in either term spontaneous labor or preterm labor; and (3) qRT-PCR measurements demonstrated that spontaneous term labor and preterm labor induced by either bacteria or ovariectomy all substantially increased the expression of multiple angiogenesis-related genes (P < or = .0003; Angpt2, Ctgf, Cyr61, Dscr1, Pgf, Serpine1, Thbs1, and Wisp 1).

CONCLUSION

Spontaneous labor at term, as well as pathologically induced preterm labor, all result in greatly increased expression of angiogenesis-related genes in the uterus.

Cytokine networks and the regulation of uterine function in pregnancy and parturition

Complex cytokine networks play an important role in a wide range of reproductive and pregnancy related processes. Here, we review the current knowledge concerning the impact of cytokines on uterine physiology and pathophysiology. Cytokines influence a range of uterine functions during the menstrual cycle, implantation, pregnancy and labour. The synergistic interactions between individual cytokines are intricate and dynamic, and modulated by pregnancy hormones. It is not surprising therefore, that perturbations to cytokine signalling are associated with adverse pregnancy outcomes, such as miscarriage, pre-eclampsia, preterm labour and foetal brain injury. Further insight into the complexity of cytokine networks will be required to develop novel therapeutic strategies for the treatment of cytokine imbalances in pregnancy.

Histone deacetylase inhibitors exert time-dependent effects on nuclear factor-kappaB but consistently suppress the expression of proinflammatory genes in human myometrial cells

Premature activation of the inflammatory processes that mediate human parturition leads to preterm birth, a major clinical problem associated with neonatal morbidity and mortality. Histone deacetylase inhibitors (HDACi) are currently in clinical trials for the treatment of inflammatory disorders. Recent evidence suggests that there may be a therapeutic use for HDACi in the management of preterm birth, with administration of HDACi to pregnant mice shown to delay delivery. Because NF-kappaB is a key orchestrator of the inflammatory response and plays a pivotal role in parturition, it is important to understand how administration of HDACi might affect NF-kappaB activity in human uterine tissues. We show here that the effects of HDACi on nuclear factor-kappaB (NF-kappaB) in human myometrial cells are time-dependent. Short-term exposure to HDACi enhanced interleukin (IL)-1beta-induced NF-kappaB activity as a result of potentiating IkappaB kinase (IKK)beta activity, thereby leading to persistent turnover of IkappaBalpha/epsilon proteins and prolonging NF-kappaB phosphorylation, nuclear localization, and DNA binding. Conversely, long-term HDACi treatments resulted in repression of NF-kappaB DNA binding. Nevertheless, both short- and long-term HDACi treatments inhibited the expression of four labor-associated proinflammatory genes (COX-2, IL-8, IL-6, and RANTES), and this was associated with repression of the proinflammatory transcription factor c-Jun. Together, our data indicate that HDACi exert anti-inflammatory effects in human myometrium and may thus be useful in achieving a myometrial gene expression profile that favors uterine quiescence. However, coadministration of an IKKbeta inhibitor may be both necessary and sufficient to circumvent potential induction of labor-associated pathways that could result from HDACi-induced augmentation of NF-kappaB activity.

Pathological interactions with the timing of birth and uterine activation

The physiological processes that regulate the onset of parturition and birth are slowly being elucidated, and the points at which pathology can intervene are becoming more apparent. The data support the view that multiple pathways lead to myometrial activation. The clinical corollary is that combinations of tocolytics that operate via different mechanisms may be more effective than single agents. It may also be necessary to divide preterm labour into groups based on underlying mechanisms and to tailor therapy accordingly.

Progesterone receptor isoforms profile, modulate matrix metalloproteinase 2 expression in the decidua

OBJECTIVE

This study explores the effect of progesterone and the role of the progesterone receptor (PR) profile on matrix metalloproteinase (MMP)-2 expression in human decidua.

STUDY DESIGN

Zymography was conducted for MMP secretion. Semiquantitative reverse transcriptase-polymerase chain reaction was performed to examine MMP2 transcripts. Progesterone's effect on the MMP2 promoter was determined testing luciferase activity. The role of PR isoform on MMP2 expression was studied using human PR complementary DNA encoding PR isoforms PRA, PRB, or PRC.

RESULTS

In decidua with overexpressed PRB, progesterone decreased MMP2 expression. Progesterone increased pro-MMP2 expression in decidua with overexpressed PRA or PRC. MMP2 promoter activity was unchanged following transfection with human PRA in the absence or presence of progesterone. Decreased promoter activity was observed following transfection with human PRB or human PRC. Progesterone increased promoter activity with overexpressed human PRC.

CONCLUSION

Progesterone hampers MMP2 expression in the decidua via PRB. PRA has a repressive effect on PRB, whereas PRC seems to have a repressive effect on both PRA and PRB.

The effect of progesterone on gelatinase expression in the decidua and fetal membranes before and after contractions

OBJECTIVE

This study was aimed to explore the effect of progesterone on gelatinase expression in the decidua and fetal membranes before and after contractions.

STUDY DESIGN

Zymography was conducted for matrix metalloproteinase (MMP) secretion. Semiquantitative reverse transcriptase-polymerase chain reaction was performed to examine MMP2 transcripts, and the effect of progesterone on MMP2 promoter activity was determined with the use of luciferase activity.

RESULTS

Progesterone decreased pro-MMP2 secretion, expression, and promoter activity in decidua before contractions began. The effect of progesterone was reversed completely by mifepristone (RU486). Progesterone failed to inhibit MMP2 expression in the amnion and chorion before contractions began. After contractions, progesterone failed to inhibit MMP2 expression in both the decidua and fetal membranes.

CONCLUSION

MMP2 expression is inhibited by progesterone only in the decidua and only before contractions begin.

Progesterone withdrawal: key to parturition

Whereas the essential role of progesterone in the maintenance of pregnancy is accepted generally, the mechanisms that suppress progesterone's function near term to allow labor and delivery of the conceptus are still shrouded in uncertainty. In most subprimate placental mammals, the withdrawal of progesterone before the initiation of labor is manifest by a significant drop in circulating progesterone levels, which is due to either luteolysis or changes in placental steroidogenesis, which shunts precursors towards estrogen production. No such events can be demonstrated in human pregnancy. In this review, we shall present a brief historic background of the research that led to the concepts of "progesterone block" and its withdrawal, based on experiments with rabbits and laboratory rodents, and discuss some of the more recent ideas about "functional progesterone withdrawal," in an attempt to bridge the apparent differences between the regulation of parturition in human and subprimate mammals.

Oxysterol nuclear receptor LXRbeta regulates cholesterol homeostasis and contractile function in mouse uterus

The uterus is an organ where lipid distribution plays a critical role for its function. Here we show that nuclear receptor for oxysterols LXRbeta prevents accumulation of cholesteryl esters in mouse myometrium by controlling expression of genes involved in cholesterol efflux and storage (abca1 and abcg1). Upon treatment with an LXR agonist that mimics activation by oxysterols, expression of these target genes was increased in wild-type mice, whereas under basal conditions, lxralpha;beta(-/-) mice exhibited a marked decrease in abcg1 accumulation. This change resulted in a phenotype of cholesteryl ester accumulation. Besides, a defect of contractile activity induced by oxytocin or PGF2alpha was observed in mice lacking LXRbeta. These results imply that LXRbeta provides a safety valve to limit cholesteryl ester levels as a basal protective mechanism in the uterus against cholesterol accumulation and is necessary for a correct induction of contractions.

Cross-talk between nuclear receptors and nuclear factor kappaB

A variety of studies have shown that some activated nuclear receptors (NRs), especially the glucorticoid receptor, the estrogen receptor and peroxisome proliferator-activated receptor, can inhibit the activity of the transcription factor nuclear factor kappaB (NF-kappaB), which plays a key role in the control of genes involved in inflammation, cell proliferation and apoptosis. This review describes the molecular mechanisms of cross-talk between NRs and NF-kappaB and the biological relevance of this cross-talk. The importance and mechanistic aspects of selective NR modulation are discussed. Also included are future research prospects, which will lead to a new era in the field of NR research with the aim of specifically inhibiting NF-kappaB-driven gene expression for anti-inflammatory, anti-tumor and immune-modulatory purposes.