The transcriptome of cervical ripening in human pregnancy before the onset of labor at term: identification of novel molecular functions involved in this process

Current status of the position on labor progress prediction for contemporary pregnant women using Friedman curves: An updated review

AIM

Prediction of labor progression is important for maternal and fetal health, as improved accuracy can lead to more timely intervention and improved outcomes. This review aims to outline the importance of predicting the progression of spontaneous parturition, detail the various methods employed to enhance this prediction and provide recommendations for future research.

METHODS

We searched articles relating to labor progression and systematic review articles on Artificial Inteligence (AI) in childbirth management using PubMed. To supplement, Google Scholar was used to find recent guidelines and related documents.

RESULTS

Traditional methods like vaginal examinations, criticized for subjectivity and inaccuracy, are gradually being replaced by ultrasound, considered a more objective and accurate approach. Further advancements have been observed with machine learning and artificial intelligence techniques, which promise to surpass the accuracies of conventional methods. The Friedman curve, developed in 1954, is the standard for assessing labor progress, but its application to Asian women, in particular, remains controversial, and various studies have reported that the actual rate of labor was slower than that indicated by the Friedman curve.

CONCLUSION

There is a need to innovate methodologies for predicting delivery tailored to modern pregnant women, especially when they have different genetic and cultural backgrounds than their Western counterparts, such as Asians. Future research should develop predictive models of labor progression that aim to enhance medical intervention and improve the safety and well-being of both mother and child.

Host-microbiome interactions in distinct subsets of preterm labor and birth

Preterm birth, the leading cause of perinatal morbidity, often follows premature labor, a syndrome whose prevention remains a challenge. To better understand the relationship between premature labor and host-microbiome interactions, we conducted a mechanistic investigation using three preterm birth models. We report that intra-amniotic delivery of LPS triggers inflammatory responses in the amniotic cavity and cervico-vaginal microenvironment, causing vaginal microbiome changes and signs of active labor. Intra-amniotic IL-1α delivery causes a moderate inflammatory response in the amniotic cavity but increasing inflammation in the cervico-vaginal space, leading to vaginal microbiome disruption and signs of active labor. Conversely, progesterone action blockade by RU-486 triggers local immune responses accompanying signs of active labor without altering the vaginal microbiome. Preterm labor facilitates ascension of cervico-vaginal bacteria into the amniotic cavity, regardless of stimulus. This study provides compelling mechanistic insights into the dynamic host-microbiome interactions within the cervico-vaginal microenvironment that accompany premature labor and birth.

Clinical chorioamnionitis at term is characterized by changes in the plasma concentration of CHCHD2/MNRR1, a mitochondrial protein

OBJECTIVE

Mitochondrial dysfunction was observed in acute systemic inflammatory conditions such as sepsis and might be involved in sepsis-induced multi-organ failure. Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 2 (CHCHD2), also known as Mitochondrial Nuclear Retrograde Regulator 1 (MNRR1), a bi-organellar protein located in the mitochondria and the nucleus, is implicated in cell respiration, survival, and response to tissue hypoxia. Recently, the reduction of the cellular CHCHD2/MNRR1 protein, as part of mitochondrial dysfunction, has been shown to play a role in the amplification of inflammatory cytokines in a murine model of lipopolysaccharide-induced systemic inflammation. The aim of this study was to determine whether the plasma concentration of CHCHD2/MNRR1 changed during human normal pregnancy, spontaneous labor at term, and clinical chorioamnionitis at term.

METHODS

We conducted a cross-sectional study that included the following groups: 1) non-pregnant women (n = 17); 2) normal pregnant women at various gestational ages from the first trimester until term (n = 110); 3) women at term with spontaneous labor (n = 50); and 4) women with clinical chorioamnionitis at term in labor (n = 25). Plasma concentrations of CHCHD2/MNRR1 were assessed by an enzyme-linked immunosorbent assay.

RESULTS

1) Pregnant women at term in labor with clinical chorioamnionitis had a significantly higher plasma CHCHD2/MNRR1 concentration than those in labor without chorioamnionitis (p = .003); 2) CHCHD2/MNRR1 is present in the plasma of healthy non-pregnant and normal pregnant women without significant differences in its plasma concentrations between the two groups; 3) there was no correlation between maternal plasma CHCHD2/MNRR1 concentration and gestational age at venipuncture; and 4) plasma CHCHD2/MNRR1 concentration was not significantly different in women at term in spontaneous labor compared to those not in labor.

CONCLUSIONS

CHCHD2/MNRR1 is physiologically present in the plasma of healthy non-pregnant and normal pregnant women, and its concentration does not change with gestational age and parturition at term. However, plasma CHCHD2/MNRR1 is elevated in women at term with clinical chorioamnionitis. CHCHD2/MNRR1, a novel bi-organellar protein located in the mitochondria and the nucleus, is released into maternal plasma during systemic inflammation.

Characteristic impairment of progesterone response in cultured cervical fibroblasts obtained from patients with refractory cervical insufficiency

Preterm birth (PTB) is the leading cause of neonatal mortality, and reducing the PTB rate is one of the most critical issues in perinatal medicine. Cervical insufficiency (CI), a major cause of PTB, is characterised by premature cervical ripening in the second trimester, followed by recurrent pregnancy loss. Although multiple clinical trials have suggested that progesterone inhibits cervical ripening, no studies have focused on progesterone-induced molecular signalling in CI. Here, we established a primary culture system for human uterine cervical fibroblasts using a sample of patients with refractory innate CI who underwent transabdominal cervical cerclage and patients with low Bishop scores who underwent elective caesarean section as controls. RNA sequencing showed that the progesterone response observed in the control group was impaired in the CI group. This was consistent with the finding that progesterone receptor expression was markedly downregulated in CI. Furthermore, the inhibitory effect of progesterone on lipopolysaccharide-induced inflammatory stimuli was also impaired in CI. These results suggest that abnormal cervical ripening in CI is caused by the downregulation of progesterone signalling at the receptor level, and provide a novel insight into the molecular mechanism of PTB.

The latent phase of labor

The latent phase of labor extends from the initiation of labor to the onset of the active phase. Because neither margin is always precisely identifiable, the duration of the latent phase often can only be estimated. During this phase, the cervix undergoes a process of rapid remodeling, which may have begun gradually weeks before. As a consequence of extensive changes in its collagen and ground substance, the cervix softens, becomes thinner and dramatically more compliant, and may dilate modestly. All of these changes prepare the cervix for the more rapid dilatation that will occur during the active phase to follow. For the clinician, it is important to recognize that the latent phase may normally extend for many hours. The normal limit for the duration of the latent phase should be considered to be approximately 20 hours in a nullipara and 14 hours in a multipara. Factors that have been associated with a prolonged latent phase include deficient prelabor or intrapartum cervical remodeling, excessive maternal analgesia or anesthesia, maternal obesity, and chorioamnionitis. Approximately 10% of women with a prolonged latent phase are actually in false labor, and their contractions eventually abate spontaneously. The management of a prolonged latent phase involves either augmenting uterine activity with oxytocin or providing a sedative-induced period of maternal rest. Both are equally effective in advancing the labor to active phase dilatation. A very long latent phase may be a harbinger of other labor dysfunctions.

Spontaneous preterm birth: Involvement of multiple feto-maternal tissues and organ systems, differing mechanisms, and pathways

Survivors of preterm birth struggle with multitudes of disabilities due to improper in utero programming of various tissues and organ systems contributing to adult-onset diseases at a very early stage of their lives. Therefore, the persistent rates of low birth weight (birth weight < 2,500 grams), as well as rates of neonatal and maternal morbidities and mortalities, need to be addressed. Active research throughout the years has provided us with multiple theories regarding the risk factors, initiators, biomarkers, and clinical manifestations of spontaneous preterm birth. Fetal organs, like the placenta and fetal membranes, and maternal tissues and organs, like the decidua, myometrium, and cervix, have all been shown to uniquely respond to specific exogenous or endogenous risk factors. These uniquely contribute to dynamic changes at the molecular and cellular levels to effect preterm labor pathways leading to delivery. Multiple intervention targets in these different tissues and organs have been successfully tested in preclinical trials to reduce the individual impacts on promoting preterm birth. However, these preclinical trial data have not been effectively translated into developing biomarkers of high-risk individuals for an early diagnosis of the disease. This becomes more evident when examining the current global rate of preterm birth, which remains staggeringly high despite years of research. We postulate that studying each tissue and organ in silos, as how the majority of research has been conducted in the past years, is unlikely to address the network interaction between various systems leading to a synchronized activity during either term or preterm labor and delivery. To address current limitations, this review proposes an integrated approach to studying various tissues and organs involved in the maintenance of normal pregnancy, promotion of normal parturition, and more importantly, contributions towards preterm birth. We also stress the need for biological models that allows for concomitant observation and analysis of interactions, rather than focusing on these tissues and organ in silos.

Progesterone and its receptor signaling in cervical remodeling: Mechanisms of physiological actions and therapeutic implications

The remodeling of the cervix from a closed rigid structure to one that can open sufficiently for passage of a term infant is achieved by a complex series of molecular events that in large part are regulated by the steroid hormones progesterone and estrogen. Among hormonal influences, progesterone exerts a dominant role for most of pregnancy to initiate a loss of tissue strength yet maintain competence in a phase termed softening. Equally important are the molecular events that abrogate progesterone function in late pregnancy to allow a loss of tissue competence and strength during cervical ripening and dilation. In this review, we focus on current understanding by which progesterone receptor signaling for the majority of pregnancy followed by a loss/shift in progesterone receptor action at the end of pregnancy, collectively ensure cervical remodeling as necessary for successful parturition.

Microbial and human transcriptome in vaginal fluid at midgestation: Association with spontaneous preterm delivery

BACKGROUND

Intrauterine infection and inflammation caused by microbial transfer from the vagina are believed to be important factors causing spontaneous preterm delivery (PTD). Multiple studies have examined the relationship between the cervicovaginal microbiome and spontaneous PTD with divergent results. Most studies have applied a DNA-based assessment, providing information on the microbial composition but not transcriptional activity. A transcriptomic approach was applied to investigate differences in the active vaginal microbiome and human transcriptome at midgestation between women delivering spontaneously preterm versus those delivering at term.

METHODS

Vaginal swabs were collected in women with a singleton pregnancy at 18 + 0 to 20 + 6 gestational weeks. For each case of spontaneous PTD (delivery <37 + 0 weeks) two term controls were randomized (39 + 0 to 40 + 6 weeks). Vaginal specimens were subject to sequencing of both human and microbial RNA. Microbial reads were taxonomically classified using Kraken2 and RefSeq as a reference. Statistical analyses were performed using DESeq2. GSEA and HUMAnN3 were used for pathway analyses.

RESULTS

We found 17 human genes to be differentially expressed (false discovery rate, FDR < 0.05) in the preterm group (n = 48) compared to the term group (n = 96). Gene expression of kallikrein-2 (KLK2), KLK3 and four isoforms of metallothioneins 1 (MT1s) was higher in the preterm group (FDR < 0.05). We found 11 individual bacterial species to be differentially expressed (FDR < 0.05), most with a low occurrence. No statistically significant differences in bacterial load, diversity or microbial community state types were found between the groups.

CONCLUSIONS

In our mainly white population, primarily bacterial species of low occurrence were differentially expressed at midgestation in women who delivered preterm versus at term. However, the expression of specific human transcripts including KLK2, KLK3 and several isoforms of MT1s was higher in preterm cases. This is of interest, because these genes may be involved in critical inflammatory pathways associated with spontaneous PTD.

Dynamic changes in maternal immune biomarkers during labor in nulliparous vs multiparous women

BACKGROUND

Immunomodulation is observed in human parturition. However, data from longitudinal studies for the prelabor phase and the active phase of labor are lacking, and no study had compared the immune responses during labor between nulliparous and multiparous women.

OBJECTIVE

This study aimed to investigate the temporal changes of immune biomarkers in maternal blood from the prelabor phase to the latent and active phases of labor and to compare the dynamic changes between nulliparous and multiparous women.

STUDY DESIGN

A prospective case-control study was conducted on women who had induction of labor at term followed by vaginal delivery. Maternal blood was serially collected at 3 consecutive time points: (1) before the onset of labor, (2) during the latent phase of labor, and (3) during the active phase of labor. Peripheral immune cells were measured by 4-color flow cytometry, and the plasma concentrations of cytokines and chemokines were measured by cytometric bead arrays. A longitudinal comparison was made to assess the dynamic changes in inflammatory parameters over 3 time points in nulliparous and multiparous women, respectively, and a cross-sectional comparison was made between nulliparous and multiparous women.

RESULTS

A total of 40 women, including 20 nulliparous and 20 multiparous, were included in the study. Prelabor circulating levels of macrophage inflammatory protein-1β, monokine induced by gamma interferon, and interferon gamma-induced protein-10 were higher in multiparous women than in nulliparous women. In the latent phase of labor, the innate immune system in both groups responded with increases in neutrophils and interleukin 6, and the nulliparous women showed a more pronounced response. During the active phase of labor, such innate immune response continued with both groups, with additional increases in natural killer cells, monocyte chemoattractant protein-1, interleukin 8, and interleukin 10. Conversely, the adaptive immune system in nulliparous women showed a reduction in both cytotoxic and helper T cells, whereas the adaptive immune system in multiparous women only had a reduction in helper T cells, showing a smaller reduction.

CONCLUSION

Innate and adaptive immune responses partake in immunomodulation during human parturition. Nulliparous and multiparous women showed different responses in their blood levels of immune cells and biomarkers during the different phases of labor.

Breaking Down the Barrier: The Role of Cervical Infection and Inflammation in Preterm Birth

Approximately 40% of cases of spontaneous preterm birth (sPTB) are associated with ascending intrauterine infections. The cervix serves as a physical and immunological gatekeeper, preventing the ascent of microorganisms from the vagina to the amniotic cavity. The cervix undergoes remodeling during pregnancy. It remains firm and closed from the start until the late third trimester of pregnancy and then dilates and effaces to accommodate the passage of the fetus during delivery. Remodeling proceeds appropriately and timely to maintain the pregnancy until term delivery. However, risk factors, such as acute and chronic infection and local inflammation in the cervix, may compromise cervical integrity and result in premature remodeling, predisposing to sPTB. Previous clinical studies have established bacterial (i.e., chlamydia, gonorrhea, mycoplasma, etc.) and viral infections (i.e., herpesviruses and human papillomaviruses) as risk factors of PTB. However, the exact mechanism leading to PTB is still unknown. This review focuses on: (1) the epidemiology of cervical infections in pregnant patients; (2) cellular mechanisms that may explain the association of cervical infections to premature cervical ripening and PTB; (3) endogenous defense mechanisms of the cervix that protect the uterine cavity from infection and inflammation; and (4) potential inflammatory biomarkers associated with cervical infection that can serve as prognostic markers for premature cervical ripening and PTB. This review will provide mechanistic insights on cervical functions to assist in managing cervical infections during pregnancy.

Inflammatory response elicited by Ureaplasma parvum colonization in human cervical epithelial, stromal, and immune cells

Ureaplasma parvum is a commensal bacterium in the female reproductive tract but has been associated with pregnancy complications such as preterm prelabor rupture of membranes and preterm birth (PTB). However, the pathologic effects of U. parvum in the cervix, which prevents ascending infections during pregnancy, are still poorly understood. To determine the impact of U. parvum on the cervix, ectocervical (ecto) and endocervical (endo) epithelial and stromal cells were incubated with U. parvum. Macrophages were also tested as a proxy for cervical macrophages to determine the antigenicity of U. parvum. The effects of U. parvum, including influence on cell cycle and cell death, antimicrobial peptide (AMP) production, epithelial-to-mesenchymal transition (EMT), and inflammatory cytokine levels, were assessed. U. parvum colonized cervical epithelial and stromal cells 4 h post-infection. Like uninfected control, U. parvum neither inhibited cell cycle progression and nor caused cell death in cervical epithelial and stromal cells. U. parvum increased the production of the AMPs cathelicidin and human β-defensin 3 and exhibited weak signs of EMT evidenced by decreased cytokeratin 18 and increased vimentin expression in cervical epithelial cells. U. parvum induced a proinflammatory environment (cytokines) and increased MMP-9 in cervical epithelial cells but promoted pro- and anti-inflammatory response in cervical stromal cells and macrophages. U. parvum may colonize the cervical epithelial layer, but induction of AMPs and anti-inflammatory response may protect the cervix and may prevent ascending infections that can cause PTB. These findings suggest that U. parvum is a weak inducer of inflammation in the cervix.

Transcriptome changes in maternal peripheral blood during term parturition mimic perturbations preceding spontaneous Preterm birth†

The complex physiologic process of parturition includes the onset of labor, which requires the orchestrated stimulation of a common pathway involving uterine contractility, cervical ripening, and chorioamniotic membrane activation. However, the labor-specific processes taking place in these tissues have limited use as predictive biomarkers unless they can be probed in non-invasive samples, such as the peripheral blood. Herein, we utilized a transcriptomic dataset to assess labor-specific changes in the peripheral blood of women who delivered at term. We identified a set of genes that were differentially expressed with labor and enriched for immunological processes, and these gene expression changes were strongly correlated with results from prior studies, providing in silico validation of our findings. We then identified significant correlations between labor-specific transcriptomic changes in the maternal circulation and those reported in the chorioamniotic membranes, myometrium, and cervix of women at term, demonstrating that tissue-specific labor signatures are partly mirrored in the peripheral blood. Last, we demonstrated a significant overlap between the peripheral blood transcriptomic changes in term parturition and those observed in asymptomatic women prior to the diagnosis of preterm prelabor rupture of membranes who delivered preterm. Collectively, we provide evidence that the normal process of labor at term is characterized by a unique immunological expression signature, which may serve as a useful tool for assessing labor status and potentially identifying women at risk for preterm birth.

Prediction of Spontaneous Preterm Birth in At-risk Women Using Thrombospondin 1 from Cervicovaginal Fluid: A Prospective Observational Study

Introduction Thrombospondin 1, desmoplakin and stratifin are putative biomarkers for the prediction of preterm birth. This study aimed to validate the predictive capability of these biomarkers in patients at risk of preterm birth.

Materials and Methods We included 109 women with symptoms of threatened spontaneous preterm birth between weeks 20 0/7 and 31 6/7 of gestation. Inclusion criteria were uterine contractions, cervical length of less than 25 mm, or a personal history of spontaneous preterm birth. Multiple gestations were also included. Samples of cervicovaginal fluid were taken before performing a digital examination and transvaginal ultrasound. Levels of cervicovaginal thrombospondin 1, desmoplakin and stratifin were quantified by enzyme-linked immunosorbent assays. The primary endpoint was spontaneous preterm birth before 34 + 0 weeks of gestation.

Results Sixteen women (14.7%) delivered before 34 + 0 weeks. Median levels of thrombospondin 1 were higher in samples where birth occurred before 34 weeks vs. ≥ 34 weeks of gestation (4904 vs. 469 pg/mL, p < 0.001). Receiver operator characteristics analysis resulted in an area under the curve of 0.86 (p < 0.0001). At an optimal cut-off value of 2163 pg/mL, sensitivity, specificity, positive predictive value and negative predictive value were 0.94, 0.77, 0.42 and 0.99, respectively, with an adjusted odds ratio of 32.9 (95% CI: 3.1 – 345, p = 0.004). Multiple gestation, cervical length, and preterm labor had no impact on the results. Survival analysis revealed a predictive period of more than eight weeks. Levels of desmoplakin and stratifin did not differ between groups.

Conclusion Thrombospondin 1 allowed long-term risk estimation of spontaneous preterm birth.

Transcriptome and proteome dynamics of cervical remodeling in the mouse during pregnancy

During gestation, the female reproductive tract must maintain pregnancy while concurrently preparing for parturition. Here, we explore the transitions in gene expression and protein turnover (fractional synthesis rates [FSR]) by which the cervix implements a transition from rigid to compliant. Shifts in gene transcription to achieve immune tolerance and alter epithelial cell programs begin in early pregnancy. Subsequently, in mid-to-late pregnancy transcriptional programs emerge that promote structural reorganization of the extracellular matrix (ECM). Stable isotope labeling revealed a striking slowdown of overall FSRs across the proteome on gestation day 6 that reverses in mid-to-late pregnancy. An exception was soluble fibrillar collagens and proteins of collagen assembly, which exhibit high turnover in non-pregnant cervix compared to other tissues and FSRs that continue throughout pregnancy. This finding provides a mechanism to explain how cross-linked collagen is replaced by newly synthesized, less-cross-linked collagens, which allows increased tissue compliance during parturition. The rapid transition requires a reservoir of newly synthesized, less cross-linked collagens, which is assured by the high FSR of soluble collagens in the cervix. These findings suggest a previously unrecognized form of "metabolic flexibility" for ECM in the cervix that underlies rapid transformation in compliance to allow parturition.

Enhanced drug delivery to the reproductive tract using nanomedicine reveals therapeutic options for prevention of preterm birth

Inflammation contributes to nearly 4 million global premature births annually. Here, we used a mouse model of intrauterine inflammation to test clinically used formulations, as well as engineered nanoformulations, for the prevention of preterm birth (PTB). We observed that neither systemic 17a-hydroxyprogesterone caproate (Makena) nor vaginal progesterone gel (Crinone) was sufficient to prevent inflammation-induced PTB, consistent with recent clinical trial failures. However, we found that vaginal delivery of mucoinert nanosuspensions of histone deacetylase (HDAC) inhibitors, in some cases with the addition of progesterone, prevented PTB and resulted in delivery of live pups exhibiting neurotypical development. In human myometrial cells in vitro, the P4/HDAC inhibitor combination both inhibited cell contractility and promoted the anti-inflammatory action of P4 by increasing progesterone receptor B stability. Here, we demonstrate the use of vaginally delivered drugs to prevent intrauterine inflammation-induced PTB resulting in the birth of live offspring in a preclinical animal model.

Human Chorionic Gonadotropin Modulates the Transcriptome of the Myometrium and Cervix in Late Gestation

Human chorionic gonadotropin (hCG) is a critical hormone for the establishment and maintenance of pregnancy. hCG administration prevents the onset of preterm labor in mice; yet, the transcriptomic changes associated with this tocolytic effect that take place in the myometrium and cervix have not been elucidated. Herein, we implemented both discovery and targeted approaches to investigate the transcriptome of the myometrium and cervix after hCG administration. Pregnant mice were intraperitoneally injected with 10 IU of hCG on 13.0, 15.0, and 17.0 days post coitum, and the myometrium and cervix were collected. RNA sequencing was performed to determine differentially expressed genes, enriched biological processes, and impacted KEGG pathways. Multiplex qRT-PCR was performed to investigate the expression of targeted contractility- and inflammation-associated transcripts. hCG administration caused the differential expression of 720 genes in the myometrium. Among the downregulated genes, enriched biological processes were primarily associated with regulation of transcription. hCG administration downregulated key contractility genes, Gja1 and Oxtr, but upregulated the prostaglandin-related genes Ptgfr and Ptgs2 and altered the expression of inflammation-related genes in the myometrium. In the cervix, hCG administration caused differential expression of 3348 genes that were related to inflammation and host defense, among others. The downregulation of key contractility genes and upregulation of prostaglandin-related genes were also observed in the cervix. Thus, hCG exerts tocolytic and immunomodulatory effects in late gestation by altering biological processes in the myometrium and cervix, which should be taken into account when considering hCG as a potential treatment to prevent the premature onset of labor.

Monochorionic twins with selective fetal growth restriction: insight from placental whole-transcriptome analysis

BACKGROUND

The underlying pathomechanism in placenta-related selective fetal growth restriction in monochorionic diamniotic twin pregnancy is not known.

OBJECTIVE

This study aimed to investigate any differences in placental transcriptomic profile between the selectively growth-restricted twins and the normally grown cotwins in monochorionic diamniotic twin pregnancies.

STUDY DESIGN

This was a prospective study of monochorionic diamniotic twin pregnancies complicated by selective fetal growth restriction. Placental biopsy specimens were obtained from the subjects in the delivery suite. The placental transcriptome of the selectively growth-restricted twin was compared with that of the normally grown cotwin. This study was divided into 2 stages: (1) gene discovery phase in which placental tissues from 5 monochorionic diamniotic twin pregnancies complicated by selective fetal growth restriction plus 2 control twin pregnancies underwent transcriptome profiling, and transcriptome profiling was carried out using whole-genome RNA sequencing; and (2) validation phase in which placental tissues from 13 monochorionic diamniotic twin pregnancies with selective fetal growth restriction underwent RNA and protein validation. RNA and protein expression levels of candidate genes were determined using quantitative real-time polymerase chain reaction and immunohistochemistry staining.

RESULTS

A total of 1429 transcripts were differentially expressed in the placentae of selectively growth-restricted twin pairs, where 610 were up-regulated and 819 were down-regulated. Endoplasmic reticulum lectin and mannose 6-phosphate receptor were consistently differentially up-regulated in all placentae of selectively growth-restricted twins. Quantitative real-time polymerase chain reaction and immunohistochemistry staining were used to validate the results (P<.05).

CONCLUSION

The expression of endoplasmic reticulum lectin and mannose 6-phosphate receptor, which are important for angiogenesis and fetal growth, was significantly increased in the placentae of selectively growth-restricted twin of a monochorionic twin pair.

Pregnancy-specific transcriptional changes upon endotoxin exposure in mice

Objectives Pregnant women are more susceptible to certain infections; however, this increased susceptibility is not fully understood. Herein, systems biology approaches were utilized to elucidate how pregnancy modulates tissue-specific host responses to a bacterial product, endotoxin. Methods Pregnant and non-pregnant mice were injected with endotoxin or saline on 16.5 days post coitum (n=8-11 per group). The uterus, cervix, liver, adrenal gland, kidney, lung, and brain were collected 12 h after injection and transcriptomes were measured using microarrays. Heatmaps and principal component analysis were used for visualization. Differentially expressed genes between groups were assessed using linear models that included interaction terms to determine whether the effect of infection differed with pregnancy status. Pathway analysis was conducted to interpret gene expression changes. Results We report herein a multi-organ atlas of the transcript perturbations in pregnant and non-pregnant mice in response to endotoxin. Pregnancy strongly modified the host responses to endotoxin in the uterus, cervix, and liver. In contrast, pregnancy had a milder effect on the host response to endotoxin in the adrenal gland, lung, and kidney. However, pregnancy did not drastically affect the host response to endotoxin in the brain. Conclusions Pregnancy imprints organ-specific host immune responses upon endotoxin exposure. These findings provide insight into the host-response against microbes during pregnancy.

Progesterone Receptor Signaling Selectively Modulates Cytokine-Induced Global Gene Expression in Human Cervical Stromal Cells

Preterm birth (PTB) is the leading cause of morbidity and mortality in infants <1 year of age. Intrauterine inflammation is a hallmark of preterm and term parturition; however, this alone cannot fully explain the pathobiology of PTB. For example, the cervix undergoes a prolonged series of biochemical and biomechanical events, including extracellular matrix (ECM) remodeling and mechanochemical changes, culminating in ripening. Vaginal progesterone (P₄) prophylaxis demonstrates great promise in preventing PTB in women with a short cervix (<25 mm). We used a primary culture model of human cervical stromal fibroblasts to investigate gene expression signatures in cells treated with interleukin-1β (IL-1β) in the presence or absence of P₄ following 17β-estradiol (17β-E₂) priming for 7–10 days. Microarrays were used to measure global gene expression in cells treated with cytokine or P₄ alone or in combination, followed by validation of select transcripts by semiquantitative polymerase chain reactions (qRT-PCR). Primary/precursor (MIR) and mature microRNAs (miR) were quantified by microarray and NanoString^® platforms, respectively, and validated by qRT-PCR. Differential gene expression was computed after data normalization followed by pathway analysis using Kyoto Encyclopedia Genes and Genomes (KEGG), Panther, Gene Ontology (GO), and Ingenuity Pathway Analysis (IPA) upstream regulator algorithm tools. Treatment of fibroblasts with IL-1β alone resulted in the differential expression of 1432 transcripts (protein coding and non-coding), while P₄ alone led to the expression of only 43 transcripts compared to untreated controls. Cytokines, chemokines, and their cognate receptors and prostaglandin endoperoxide synthase-2 (PTGS-2) were among the most highly upregulated transcripts following either IL-1β or IL-1β + P₄. Other prominent differentially expressed transcripts were those encoding ECM proteins, ECM-degrading enzymes, and enzymes involved in glycosaminoglycan (GAG) biosynthesis. We also detected differential expression of bradykinin receptor-1 and -2 transcripts, suggesting (prominent in tissue injury/remodeling) a role for the kallikrein–kinin system in cervical responses to cytokine and/or P₄ challenge. Collectively, this global gene expression study provides a rich database to interrogate stromal fibroblasts in the setting of a proinflammatory and endocrine milieu that is relevant to cervical remodeling/ripening during preparation for parturition.

Inflammasomes: Their Role in Normal and Complicated Pregnancies

Inflammasomes are cytoplasmic multiprotein complexes that coordinate inflammatory responses, including those that take place during pregnancy. Inflammasomes and their downstream mediators caspase-1 and IL-1β are expressed by gestational tissues (e.g., the placenta and chorioamniotic membranes) during normal pregnancy. Yet, only the activation of the NLRP3 inflammasome in the chorioamniotic membranes has been partially implicated in the sterile inflammatory process of term parturition. In vivo and ex vivo studies have consistently shown that the activation of the NLRP3 inflammasome is a mechanism whereby preterm labor and birth occur in the context of microbial- or alarmin-induced inflammation. In the placenta, the activation of the NLRP3 inflammasome is involved in the pathogenesis of preeclampsia and other pregnancy syndromes associated with placental inflammation. This evidence suggests that inhibition of the NLRP3 inflammasome or its downstream mediators may foster the development of novel anti-inflammatory therapies for the prevention or treatment of pregnancy complications.

Genetic landscape of preterm birth due to cervical insufficiency: Comprehensive gene analysis and patient next-generation sequencing data interpretation

Preterm delivery is both a traumatizing experience for the patient and a burden on the healthcare system. A condition distinguishable by its phenotype in prematurity is cervical insufficiency, where certain cases exhibit a strong genetic component. Despite genomic advancements, little is known about the genetics of human cervix remodeling during pregnancy. Using selected gene approaches, a few studies have demonstrated an association of common gene variants with cervical insufficiency. However, until now, no study has employed comprehensive methods to investigate this important subject matter. In this study, we asked: i) are there genes reliably linked to cervical insufficiency and, if so, what are their roles? and ii) what is the proportion of cases of non-syndromic cervical insufficiency attributable to these genetic variations? We performed next-generation sequencing on 21 patients with a clinical presentation of cervical insufficiency. To assist the sequencing data interpretation, we retrieved all known genes implicated in cervical functioning through a systematic literature analysis and additional gene searches. These genes were then classified according to their relation to the questions being posed by the study. Patients' sequence variants were filtered for pathogenicity and assigned a likelihood of being contributive to phenotype development. Gene extraction and analysis revealed 12 genes primarily linked to cervical insufficiency, the majority of which are known to cause collagenopathies. Ten patients carried disruptive variants potentially contributive to the development of non-syndromic cervical insufficiency. Pathway enrichment analysis of variant genes from our cohort revealed an increased variation burden in genes playing roles in tissue mechanical and biomechanical properties, i.e. collagen biosynthesis and cell-extracellular matrix communications. Consequently, the proposed idea of cervical insufficiency being a subtle form of collagenopathy, now strengthened by our genetic findings, might open up new opportunities for improved patient evaluation and management.

The role of noninvasive diagnostic imaging in monitoring pregnancy and detecting patients at risk for preterm birth: a review of quantitative approaches

Preterm birth (PTB) is the leading cause of neonatal morbidity and mortality worldwide. The ability to predict patients at risk for preterm birth remains a major health challenge. The currently available clinical diagnostics such as cervical length and fetal fibronectin may detect only up to 30% of patients who eventually experience a spontaneous preterm birth. This paper reviews ongoing efforts to improve the ability to conduct a risk assessment for preterm birth. In particular, this work focuses on quantitative methods of imaging using ultrasound-based techniques, magnetic resonance imaging, and optical imaging modalities. While ultrasound imaging is the major modality for preterm birth risk assessment, a summary of efforts to adopt other imaging modalities is also discussed to identify the technical and diagnostic limits associated with adopting them in clinical settings. We conclude the review by proposing a new approach using combined photoacoustic, ultrasound, and elastography as a potential means to better assess cervical tissue remodeling, and thus improve the detection of patients at-risk of PTB.

Characterization of an Adapted Murine Model of Intrauterine Inflammation-Induced Preterm Birth

Preterm birth (PTB) affects nearly 15 million infants each year. Of these PTBs, >25% are a result of inflammation or infection. Animal models have improved our understanding of the mechanisms leading to PTB. Prior work has described induction of intrauterine inflammation in mice with a single injection of lipopolysaccharide (LPS). Herein, we have improved the reproducibility and potency of LPS in the model using two injections distal to the cervix. An in vivo imaging system revealed more uniform distribution of Evans Blue Dye using a double distal injection (DDI) approach compared with a single proximal injection (SPI). Endotoxin concentrations in vaginal lavage fluid from SPI dams were significantly higher than from DDI dams. At equivalent LPS doses, DDI consistently induced more PTB than SPI, and DDI showed a linear dose-response, whereas SPI did not. Gene expression in myometrial tissue revealed increased levels of inflammatory markers in dams that received LPS DDI compared with LPS SPI. The SPI group showed more significant overexpression in cervical remodeling genes, likely due to the leakage of LPS from the uterine horns through the cervix. The more reliable PTB induction and uniform uterine exposure provided by this new model will be useful for further studying fetal outcomes and potential therapeutics for the prevention of inflammation-induced PTB.

Single cell transcriptional signatures of the human placenta in term and preterm parturition

More than 135 million births occur each year; yet, the molecular underpinnings of human parturition in gestational tissues, and in particular the placenta, are still poorly understood. The placenta is a complex heterogeneous organ including cells of both maternal and fetal origin, and insults that disrupt the maternal-fetal dialogue could result in adverse pregnancy outcomes such as preterm birth. There is limited knowledge of the cell type composition and transcriptional activity of the placenta and its compartments during physiologic and pathologic parturition. To fill this knowledge gap, we used scRNA-seq to profile the placental villous tree, basal plate, and chorioamniotic membranes of women with or without labor at term and those with preterm labor. Significant differences in cell type composition and transcriptional profiles were found among placental compartments and across study groups. For the first time, two cell types were identified: 1) lymphatic endothelial decidual cells in the chorioamniotic membranes, and 2) non-proliferative interstitial cytotrophoblasts in the placental villi. Maternal macrophages from the chorioamniotic membranes displayed the largest differences in gene expression (e.g. NFKB1) in both processes of labor; yet, specific gene expression changes were also detected in preterm labor. Importantly, several placental scRNA-seq transcriptional signatures were modulated with advancing gestation in the maternal circulation, and specific immune cell type signatures were increased with labor at term (NK-cell and activated T-cell signatures) and with preterm labor (macrophage, monocyte, and activated T-cell signatures). Herein, we provide a catalogue of cell types and transcriptional profiles in the human placenta, shedding light on the molecular underpinnings and non-invasive prediction of the physiologic and pathologic parturition.

Genome-wide association analysis uncovers variants for reproductive variation across dog breeds and links to domestication

BACKGROUND AND OBJECTIVES

The diversity of eutherian reproductive strategies has led to variation in many traits, such as number of offspring, age of reproductive maturity and gestation length. While reproductive trait variation has been extensively investigated and is well established in mammals, the genetic loci contributing to this variation remain largely unknown. The domestic dog, Canis lupus familiaris is a powerful model for studies of the genetics of inherited disease due to its unique history of domestication. To gain insight into the genetic basis of reproductive traits across domestic dog breeds, we collected phenotypic data for four traits, cesarean section rate, litter size, stillbirth rate and gestation length, from primary literature and breeders' handbooks.

METHODOLOGY

By matching our phenotypic data to genomic data from the Cornell Veterinary Biobank, we performed genome-wide association analyses for these four reproductive traits, using body mass and kinship among breeds as covariates.

RESULTS

We identified 12 genome-wide significant associations between these traits and genetic loci, including variants near CACNA2D3 with gestation length, MSRB3 and MSANTD1 with litter size, SMOC2 with cesarean section rate and UFM1 with stillbirth rate. A few of these loci, such as CACNA2D3 and MSRB3, have been previously implicated in human reproductive pathologies, whereas others have been associated with domestication-related traits, including brachycephaly (SMOC2) and coat curl (KRT71).

CONCLUSIONS AND IMPLICATIONS

We hypothesize that the artificial selection that gave rise to dog breeds also influenced the observed variation in their reproductive traits. Overall, our work establishes the domestic dog as a system for studying the genetics of reproductive biology and disease.

LAY SUMMARY

The genetic contributors to variation in mammalian reproductive traits remain largely unknown. We took advantage of the domestic dog, a powerful model system, to test for associations between genome-wide variants and four reproductive traits (cesarean section rate, litter size, stillbirth rate and gestation length) that vary extensively across breeds. We identified associations at a dozen loci, including ones previously associated with domestication-related traits, suggesting that selection on dog breeds also influenced their reproductive traits.

In vivo evidence of inflammasome activation during spontaneous labor at term

OBJECTIVE

Upon inflammasome activation, the adaptor protein of the inflammasome ASC (apoptosis-associated speck-like protein containing a CARD) forms intracellular specks, which can be released into the extracellular space. The objectives of this study were to investigate whether (1) extracellular ASC is present in the amniotic fluid of women who delivered at term; (2) amniotic fluid ASC concentrations are greater in women who underwent spontaneous labor at term than in those who delivered at term in the absence of labor; and (3) amniotic epithelial and mesenchymal cells can form intracellular ASC specks in vitro.

METHODS

This retrospective cross-sectional study included amniotic fluid samples from 41 women who delivered at term in the absence of labor (n = 24) or underwent spontaneous labor at term (n = 17). Amniotic epithelial and mesenchymal cells were also isolated from the chorioamniotic membranes obtained from a separate group of women who delivered at term (n = 3), in which ASC speck formation was assessed by confocal microscopy. Monocytes from healthy individuals were used as positive controls for ASC speck formation (n = 3).

RESULTS

(1) The adaptor protein of the inflammasome ASC is detectable in the amniotic fluid of women who delivered at term; (2) amniotic fluid ASC concentration was higher in women who underwent spontaneous labor at term than in those who delivered at term without labor; and (3) amniotic epithelial and mesenchymal cells are capable of forming ASC specks and/or filaments in vitro.

CONCLUSION

Amniotic fluid ASC concentrations are increased in women who undergo spontaneous labor at term. Amniotic epithelial and mesenchymal cells are capable of forming ASC specks, suggesting that these cells are a source of extracellular ASC in the amniotic fluid. These findings provide in vivo evidence that there is inflammasome activation in the amniotic cavity during the physiological process of labor at term.

Tensile Mechanical Properties and Dynamic Collagen Fiber Re-Alignment of the Murine Cervix are Dramatically Altered Throughout Pregnancy

The cervix is a unique organ able to dramatically change its shape and function by serving as a physical barrier for the growing fetus and then undergoing dramatic dilation allowing for delivery of a term infant. As a result, the cervix endures changing mechanical forces from the growing fetus. There is an emerging concept that the cervix may change or remodel "early" in many cases of spontaneous preterm birth (sPTB). However, the mechanical role of the cervix in both normal and preterm birth remains unclear. Therefore, the primary objective of this study was to determine the mechanical and structural responses of murine cervical tissue throughout a normal gestational time course. In this study, both tissue structural and material properties were determined via a quasi-static tensile load-to-failure test, while simultaneously obtaining dynamic collagen fiber re-alignment via cross-polarization imaging. This study demonstrated that the majority of the mechanical properties evaluated decreased at midgestation and not just at term, while collagen fiber re-alignment occurred earlier in the loading curve for cervices at term. This suggests that although structural changes in the cervix occur throughout gestation, the differences in material properties function in combination with collagen fiber re-alignment as mechanical precursors to regulate term gestation. This work lays a foundation for investigating cervical biomechanics and the role of the cervix in preterm birth.

Neutrophil Extracellular Traps in the Amniotic Cavity of Women with Intra-Amniotic Infection: A New Mechanism of Host Defense

OBJECTIVE

Neutrophil extracellular traps (NETs) control microbial infections through their antimicrobial activities attributed to DNA, histones, granules, and cytoplasmic proteins (eg, elastase). Intra-amniotic infection is characterized by the influx of neutrophils into the amniotic cavity; therefore, the aim of this study was to determine whether amniotic fluid neutrophils form NETs in this inflammatory process.

METHODS

Amniotic fluid samples from women with intra-amniotic infection (n = 15) were stained for bacteria detection using fluorescent dyes. Amniotic fluid neutrophils were purified by filtration. As controls, neutrophils from maternal blood samples (n = 3) were isolated by density gradients. Isolated neutrophils were plated onto glass cover slips for culture with and without 100 nM of phorbol-12-myristate-13-acetate (PMA). NET formation was assessed by 4',6-diamidino-2-phenylindole (DAPI) staining and scanning electron microscopy. Different stages of NET formation were visualized using antibodies against elastase and histone H3, in combination with DAPI staining, by confocal microscopy. Finally, maternal or neonatal neutrophils were added to amniotic fluid samples from women without intra-amniotic infection (n = 4), and NET formation was evaluated by DAPI staining.

RESULTS

(1) NETs were present in the amniotic fluid of women with intra-amniotic infection; (2) all of the amniotic fluid samples had detectable live and dead bacteria associated with the presence of NETs; (3) in contrast to neutrophils from the maternal circulation, amniotic fluid neutrophils did not require PMA stimulation to form NETs; (4) different stages of NET formation were observed by co-localizing elastase, histone H3, and DNA in amniotic fluid neutrophils; and (5) neither maternal nor neonatal neutrophils form NETs in the amniotic fluid of women without intra-amniotic infection.

CONCLUSION

NETs are detectable in the amniotic fluid of women with intra-amniotic infection.

Labor prediction based on the expression patterns of multiple genes related to cervical maturation in human term pregnancy

PROBLEM

This study explored the possibility of evaluating cervical maturation using swabbed cervical cell samples at term pregnancy, and aimed to develop a novel approach to predict labor onset.

METHOD OF STUDY

Women with uncomplicated pregnancies (n=117 from 62 women at term pregnancy) were recruited. Messenger RNA expression levels of cervical cells for ten genes were quantified by qPCR. Principal component analysis (PCA) was conducted, and principal components that significantly contributed to the prediction of days to delivery were determined.

RESULTS

PCA demonstrated that 76% of the expression information from the ten genes can be represented by three principal components (PC1-3). By the multiple regression analysis, PC2 and Bishop score but not PC1 or PC3 were significant variables in the prediction of days to delivery.

CONCLUSION

These findings support the concurrent assessment of multiple gene activities in cervical cells as a promising approach to predict the initiation of labor.

Cervical collagen is reduced in non-pregnant women with a history of cervical insufficiency and a short cervix

INTRODUCTION

Preterm cervical shortening and cervical insufficiency may be caused by a constitutional weakness of the cervix. The aim of this study was to assess the cervical collagen concentration in non-pregnant women with a history of cervical insufficiency or of a short cervix in the second trimester of pregnancy.

MATERIAL AND METHODS

In this case-control study we included non-pregnant women one year or more after pregnancy: 55 controls with a history of normal delivery; 27 women with a history of cervical insufficiency; and 10 women with a history of a short cervix (<5th percentile) and 10 women with a history of a long cervix (>95th percentile) at gestational weeks 18-20. We obtained biopsies (3 × 3-4 mm) from the ectocervix and determined the collagen concentration by measuring the hydroxyproline concentration.

RESULTS

Women with cervical insufficiency had lower collagen concentrations (63.5 ± 5.1%; mean ± SD) compared with controls (68.2 ± 5.4%; p = 0.0004); area under the ROC curve 0.73 (95% CI 0.62-0.84). A cut-off value at 67.6% collagen resulted in a positive likelihood ratio of 3.2, a sensitivity of 60%, and a specificity of 81%. Also, women with a short cervix in the second trimester had lower collagen concentrations in a non-pregnant state (62.1% ± 4.9%) compared with women with a long cervix (67.8% ± 5.0%; p = 0.02).

CONCLUSIONS

Both cervical insufficiency and a short cervix in the second trimester of pregnancy are associated with low cervical collagen concentrations in a non-pregnant state more than one year after pregnancy.

Characterization of visceral and subcutaneous adipose tissue transcriptome in pregnant women with and without spontaneous labor at term: implication of alternative splicing in the metabolic adaptations of adipose tissue to parturition

OBJECTIVE

The aim of this study was to determine gene expression and splicing changes associated with parturition and regions (visceral vs. subcutaneous) of the adipose tissue of pregnant women.

STUDY DESIGN

The transcriptome of visceral and abdominal subcutaneous adipose tissue from pregnant women at term with (n=15) and without (n=25) spontaneous labor was profiled with the Affymetrix GeneChip Human Exon 1.0 ST array. Overall gene expression changes and the differential exon usage rate were compared between patient groups (unpaired analyses) and adipose tissue regions (paired analyses). Selected genes were tested by quantitative reverse transcription-polymerase chain reaction.

RESULTS

Four hundred and eighty-two genes were differentially expressed between visceral and subcutaneous fat of pregnant women with spontaneous labor at term (q-value <0.1; fold change >1.5). Biological processes enriched in this comparison included tissue and vasculature development as well as inflammatory and metabolic pathways. Differential splicing was found for 42 genes [q-value <0.1; differences in Finding Isoforms using Robust Multichip Analysis scores >2] between adipose tissue regions of women not in labor. Differential exon usage associated with parturition was found for three genes (LIMS1, HSPA5, and GSTK1) in subcutaneous tissues.

CONCLUSION

We show for the first time evidence of implication of mRNA splicing and processing machinery in the subcutaneous adipose tissue of women in labor compared to those without labor.

Pathway crosstalk effects: Shrinkage and disentanglement using a Bayesian hierarchical model

Identifying the biological pathways that are related to various clinical phenotypes is an important concern in biomedical research. Based on estimated expression levels and/or p-values, over-representation analysis (ORA) methods provide rankings of pathways, but they are tainted because pathways overlap. This crosstalk phenomenon has not been rigorously studied and classical ORA does not take into consideration: (i) that crosstalk effects in cases of overlapping pathways can cause incorrect rankings of pathways, (ii) that crosstalk effects can cause both excess type I errors and type II errors, (iii) that rankings of small pathways are unreliable and (iv) that type I error rates can be inflated due to multiple comparisons of pathways. We develop a Bayesian hierarchical model that addresses these problems, providing sensible estimates and rankings, and reducing error rates. We show, on both real and simulated data, that the results of our method are more accurate than the results produced by the classical over-representation analysis, providing a better understanding of the underlying biological phenomena involved in the phenotypes under study. The R code and the binary datasets for implementing the analyses described in this article are available online at: http://www.eng.wayne.edu/page.php?id=6402.

Elevated concentration of secretory leukocyte protease inhibitor in the cervical mucus before delivery

BACKGROUND

Cervical remodeling during parturition progresses under exquisite regulation by immunologic mediators and proteases. Secretory leukocyte protease inhibitor is a secretory protein that can function as an antimicrobial peptide, an antiinflammatory molecule, and a protease inhibitor. The involvement of secretory leukocyte protease inhibitor in cervical remodeling before and during parturition is understood poorly.

OBJECTIVE

We aimed to reveal the role of secretory leukocyte protease inhibitor in the cervical remodeling process before normal term delivery and to evaluate its utility as a predictive biomarker for timing of delivery.

STUDY DESIGN

Cervical mucus samples were collected prospectively at weekly prenatal visits from a cohort of pregnant women at term. The secretory leukocyte protease inhibitor concentrations in 95 mucus samples that were obtained from 49 women with uncomplicated pregnancy who subsequently underwent normal vaginal delivery were assessed. Alterations in secretory leukocyte protease inhibitor concentrations at term and the association of secretory leukocyte protease inhibitor levels with the time to delivery were analyzed.

RESULTS

A moderate positive correlation with significance was detected between cervical mucus secretory leukocyte protease inhibitor concentrations and days to delivery (r = 0.38; P = .0001). The secretory leukocyte protease inhibitor concentration was significantly higher in samples that were collected within 7 days of delivery when compared with samples that were collected >7 days before delivery (P = .001). Secretory leukocyte protease inhibitor concentrations were also significantly higher in samples from women with premature rupture of membranes when compared with those without premature rupture of membranes (P = .01), all of whom delivered within 7 days. A logistic regression analysis revealed that the cervical secretory leukocyte protease inhibitor level was a significant parameter for the prediction of the onset of delivery. (P = .017; unit odds ratio, 1.28; 95% confidence interval, 1.07-1.61). A cut-off value of cervical secretory leukocyte protease inhibitor/total protein to predict delivery within 7 days was determined to be 1.62 μg/mg (sensitivity, 0.69; specificity, 0.72) using receiver operating characteristic curve-analysis.

CONCLUSION

Secretory leukocyte protease inhibitor concentrations in the cervical mucus elevate progressively before delivery in uncomplicated term pregnancies. Our findings suggest that cervical secretory leukocyte protease inhibitor is a candidate biomarker for delivery prediction.

A Role for the Inflammasome in Spontaneous Labor at Term

PROBLEM

Inflammasomes are signaling platforms that, upon sensing pathogens and sterile stressors, mediate the release of mature forms of interleukin (IL)-1β and IL-18. The aims of this study were to determine (i) the expression of major inflammasome components in the chorioamniotic membranes in spontaneous labor at term, (ii) whether there are changes in the inflammasome components associated with the activation of caspase-1 and caspase-4, and (iii) whether these events are associated with the release of the mature forms of IL-1β and IL-18.

METHOD OF STUDY

Chorioamniotic membranes were collected from women at term with and without spontaneous labor. mRNA abundance and protein concentrations of inflammasome components, nucleotide-binding oligomerization domain-containing (NOD)1 and NOD2 proteins, caspase-1, caspase-4, IL-1β, and IL-18 were quantified by qRT-PCR (n = 28-29 each), ELISA (n = 10 each) or immunoblotting (n = 8 each), and immunohistochemistry (n = 10 each). Active caspase-1 and caspase-4, as well as mature IL-18, were determined by immunoblotting (n = 4 each), and pro- and mature forms of IL-1β were determined by ELISA (n = 4-7 each).

RESULTS

Inflammasome components and NOD proteins were expressed in the chorioamniotic membranes obtained from women at term. The chorioamniotic membranes from women who underwent labor had (i) higher concentrations of NLRP3 (NOD-like receptor family, pyrin domain-containing protein 3) and NOD1 protein, (ii) greater immunoreactivity for caspase-1 and caspase-4, (iii) a greater quantity of the active form of caspase-1 (p20), and (iv) higher mRNA abundance and protein concentrations of pro- and mature IL-1β. However, mRNA abundance and protein concentrations of the mature form of IL-18 were not increased in tissues from women who underwent labor at term.

CONCLUSIONS

Spontaneous labor at term is characterized by the expression of inflammasome components, which may participate in the activation of caspase-1 and lead to the cleavage and release of mature IL-1β by the chorioamniotic membranes. These results support the participation of the inflammasome in the mechanisms responsible for spontaneous parturition at term.

Neutrophil migration into the placenta: Good, bad or deadly?

Almost 2 decades have passed since the discovery that pregnancy is associated with a basal inflammatory state involving neutrophil activation, and that this is more overt in cases with preeclampsia, than in instances with sepsis. This pivotal observation paved the way for our report, made almost a decade ago, describing the first involvement of neutrophil extracellular traps (NETs) in a non-infectious human pathology, namely preeclampsia, where an abundance of these structures were detected directly in the placental intervillous space.

Despite these remarkable findings, there remains a paucity of interest among reproductive biologists in further exploring the role or involvement of neutrophils in pregnancy and related pathologies. In this review we attempt to redress this deficit by highlighting novel recent findings including the discovery of a novel neutrophil subset in the decidua, the interaction of placental protein 13 (PP13) and neutrophils in modulating spiral artery modification, as well as the use of animal model systems to elucidate neutrophil function in implantation, gestation and parturition. These model systems have been particularly useful in identifying key components implicated in recurrent fetal loss, preeclampsia or new signaling molecules such as sphingolipids. Finally, the recent discovery that anti-phospolipid antibodies can trigger NETosis, supports our hypothesis that these structures may contribute to placental dysfunction in pertinent cases with recurrent fetal loss.

Characterization of Visceral and Subcutaneous Adipose Tissue Transcriptome and Biological Pathways in Pregnant and Non-Pregnant Women: Evidence for Pregnancy-Related Regional-Specific Differences in Adipose Tissue

Objective

The purpose of this study was to compare the transcriptome of visceral and subcutaneous adipose tissues between pregnant and non-pregnant women.

Study Design

The transcriptome of paired visceral and abdominal subcutaneous adipose tissues from pregnant women at term and matched non-pregnant women (n = 11) was profiled with the Affymetrix Human Exon 1.0 ST array. Differential expression of selected genes was validated with the use of quantitative reverse transcription–polymerase chain reaction.

Results

Six hundred forty-four transcripts from 633 known genes were differentially expressed (false discovery rate (FDR) <0.1; fold-change >1.5), while 42 exons from 36 genes showed differential usage (difference in FIRMA scores >2 and FDR<0.1) between the visceral and subcutaneous fat of pregnant women. Fifty-six known genes were differentially expressed between pregnant and non-pregnant subcutaneous fat and three genes in the visceral fat. Enriched biological processes in the subcutaneous adipose tissue of pregnant women were mostly related to inflammation.

Conclusion

The transcriptome of visceral and subcutaneous fat depots reveals pregnancy-related gene expression and splicing differences in both visceral and subcutaneous adipose tissue. Furthermore, for the first time, alternative splicing in adipose tissue has been associated with regional differences and human parturition.

Sterile intra-amniotic inflammation in asymptomatic patients with a sonographic short cervix: prevalence and clinical significance

OBJECTIVE

To determine the frequency and clinical significance of sterile and microbial-associated intra-amniotic inflammation in asymptomatic patients with a sonographic short cervix.

METHODS

Amniotic fluid (AF) samples obtained by transabdominal amniocentesis from 231 asymptomatic women with a sonographic short cervix [cervical length (CL) ≤25 mm] were analyzed using cultivation techniques (for aerobic and anaerobic as well as genital mycoplasmas) and broad-range polymerase chain reaction (PCR) coupled with electrospray ionization mass spectrometry (PCR/ESI-MS). The frequency and magnitude of intra-amniotic inflammation [defined as an AF interleukin (IL)-6 concentration ≥2.6 ng/mL], acute histologic placental inflammation, spontaneous preterm delivery (sPTD), and the amniocentesis-to-delivery interval were examined according to the results of AF cultures, PCR/ESI-MS and AF IL-6 concentrations.

RESULTS

Ten percent (24/231) of patients with a sonographic short cervix had sterile intra-amniotic inflammation (an elevated AF IL-6 concentration without evidence of microorganisms using cultivation and molecular methods). Sterile intra-amniotic inflammation was significantly more frequent than microbial-associated intra-amniotic inflammation [10.4% (24/231) versus 2.2% (5/231); p < 0.001]. Patients with sterile intra-amniotic inflammation had a significantly higher rate of sPTD <34 weeks of gestation [70.8% (17/24) versus 31.6% (55/174); p < 0.001] and a significantly shorter amniocentesis-to-delivery interval than patients without intra-amniotic inflammation [median 35, (IQR: 10-70) versus median 71, (IQR: 47-98) days, (p < 0.0001)].

CONCLUSION

Sterile intra-amniotic inflammation is more common than microbial-associated intra-amniotic inflammation in asymptomatic women with a sonographic short cervix, and is associated with increased risk of sPTD (<34 weeks). Further investigation is required to determine the causes of sterile intra-amniotic inflammation and the mechanisms whereby this condition is associated with a short cervix and sPTD.

Gestational tissue transcriptomics in term and preterm human pregnancies: a systematic review and meta-analysis

BACKGROUND

Preterm birth (PTB), or birth before 37 weeks of gestation, is the leading cause of newborn death worldwide. PTB is a critical area of scientific study not only due to its worldwide toll on human lives and economies, but also due to our limited understanding of its pathogenesis and, therefore, its prevention. This systematic review and meta-analysis synthesizes the landscape of PTB transcriptomics research to further our understanding of the genes and pathways involved in PTB subtypes.

METHODS

We evaluated published genome-wide pregnancy studies across gestational tissues and pathologies, including those that focus on PTB, by performing a targeted PubMed MeSH search and systematically reviewing all relevant studies.

RESULTS

Our search yielded 2,361 studies on gestational tissues including placenta, decidua, myometrium, maternal blood, cervix, fetal membranes (chorion and amnion), umbilical cord, fetal blood, and basal plate. Selecting only those original research studies that measured transcription on a genome-wide scale and reported lists of expressed genetic elements identified 93 gene expression, 21 microRNA, and 20 methylation studies. Although 30 % of all PTB cases are due to medical indications, 76 % of the preterm studies focused on them. In contrast, only 18 % of the preterm studies focused on spontaneous onset of labor, which is responsible for 45 % of all PTB cases. Furthermore, only 23 of the 10,993 unique genetic elements reported to be transcriptionally active were recovered 10 or more times in these 134 studies. Meta-analysis of the 93 gene expression studies across 9 distinct gestational tissues and 29 clinical phenotypes showed limited overlap of genes identified as differentially expressed across studies.

CONCLUSIONS

Overall, profiles of differentially expressed genes were highly heterogeneous both between as well as within clinical subtypes and tissues as well as between studies of the same clinical subtype and tissue. These results suggest that large gaps still exist in the transcriptomic study of specific clinical subtypes as well in the generation of the transcriptional profile of well-studied clinical subtypes; understanding the complex landscape of prematurity will require large-scale, systematic genome-wide analyses of human gestational tissues on both understudied and well-studied subtypes alike.

Galectins: Double-edged Swords in the Cross-roads of Pregnancy Complications and Female Reproductive Tract Inflammation and Neoplasia

Galectins are an evolutionarily ancient and widely expressed family of lectins that have unique glycan-binding characteristics. They are pleiotropic regulators of key biological processes, such as cell growth, proliferation, differentiation, apoptosis, signal transduction, and pre-mRNA splicing, as well as homo- and heterotypic cell-cell and cell-extracellular matrix interactions. Galectins are also pivotal in immune responses since they regulate host-pathogen interactions, innate and adaptive immune responses, acute and chronic inflammation, and immune tolerance. Some galectins are also central to the regulation of angiogenesis, cell migration and invasion. Expression and functional data provide convincing evidence that, due to these functions, galectins play key roles in shared and unique pathways of normal embryonic and placental development as well as oncodevelopmental processes in tumorigenesis. Therefore, galectins may sometimes act as double-edged swords since they have beneficial but also harmful effects for the organism. Recent advances facilitate the use of galectins as biomarkers in obstetrical syndromes and in various malignancies, and their therapeutic applications are also under investigation. This review provides a general overview of galectins and a focused review of this lectin subfamily in the context of inflammation, infection and tumors of the female reproductive tract as well as in normal pregnancies and those complicated by the great obstetrical syndromes.

Clinical chorioamnionitis at term I: microbiology of the amniotic cavity using cultivation and molecular techniques

INTRODUCTION

The objectives of this study were: 1) to determine the amniotic fluid (AF) microbiology of patients with the diagnosis of clinical chorioamnionitis at term using both cultivation and molecular techniques; and 2) to examine the relationship between intra-amniotic inflammation with and without microorganisms and placental lesions consistent with acute AF infection.

METHODS

The AF samples obtained by transabdominal amniocentesis from 46 women with clinical signs of chorioamnionitis at term were analyzed using cultivation techniques (for aerobic and anerobic bacteria as well as genital mycoplasmas) and broad-range polymerase chain reaction (PCR) coupled with electrospray ionization mass spectrometry (PCR/ESI-MS). The frequency of microbial invasion of the amniotic cavity (MIAC), intra-amniotic inflammation [defined as an AF interleukin 6 (IL-6) concentration ≥2.6 ng/mL], and placental lesions consistent with acute AF infection (acute histologic chorioamnionitis and/or acute funisitis) were examined according to the results of AF cultivation and PCR/ESI-MS as well as AF IL-6 concentrations.

RESULTS

1) Culture identified bacteria in AF from 46% (21/46) of the participants, whereas PCR/ESI-MS was positive for microorganisms in 59% (27/46) – combining these two tests, microorganisms were detected in 61% (28/46) of patients with clinical chorioamnionitis at term. Eight patients had discordant test results; one had a positive culture and negative PCR/ESI-MS result, whereas seven patients had positive PCR/ESI-MS results and negative cultures. 2) Ureaplasma urealyticum (n=8) and Gardnerella vaginalis (n=10) were the microorganisms most frequently identified by cultivation and PCR/ESI-MS, respectively. 3) When combining the results of AF culture, PCR/ESI-MS and AF IL-6 concentrations, 15% (7/46) of patients did not have intra-amniotic inflammation or infection, 6.5% (3/46) had only MIAC, 54% (25/46) had microbial-associated intra-amniotic inflammation, and 24% (11/46) had intra-amniotic inflammation without detectable microorganisms. 4) Placental lesions consistent with acute AF infection were significantly more frequent in patients with microbial-associated intra-amniotic inflammation than in those without intra-amniotic inflammation [70.8% (17/24) vs. 28.6% (2/7); P=0.04].

CONCLUSION

Microorganisms in the AF were identified in 61% of patients with clinical chorioamnionitis at term; 54% had microbial-associated intra-amniotic inflammation, whereas 24% had intra-amniotic inflammation without detectable microorganisms.

In vivo experiments reveal the good, the bad and the ugly faces of sFlt-1 in pregnancy

Objective

Soluble fms-like tyrosine kinase (sFlt)-1-e15a, a primate-specific sFlt-1-isoform most abundant in the human placenta in preeclampsia, can induce preeclampsia in mice. This study compared the effects of full-length human (h)sFlt-1-e15a with those of truncated mouse (m)sFlt-1(1-3) used in previous preeclampsia studies on pregnancy outcome and clinical symptoms in preeclampsia.

Methods

Mice were injected with adenoviruses or fiber-mutant adenoviruses overexpressing hsFlt-1-e15a, msFlt-1(1-3) or control GFP under the CMV or CYP19A1 promoters on gestational day 8 (GD8) and GD11. Placentas and pups were delivered by cesarean section, and dams were monitored postpartum. Blood pressure was telemetrically recorded. Urine samples were collected with cystocentesis and examined for albumin/creatinine ratios. Tissue specimens were evaluated for transgene as well as endogenous mFlt-1 and msFlt-1-i13 expression. H&E-, Jones- and PAS-stained kidney sections were histopathologically examined. Placental GFP expression and aortic ring assays were investigated with confocal microscopy.

Results

Mean arterial blood pressure (MAP) was elevated before delivery in hsFlt-1-e15a-treated mice compared to controls (GD18: ΔMAP = 7.8 mmHg, p = 0.009), while ΔMAP was 12.8 mmHg (GD18, p = 0.005) in msFlt-1(1-3)-treated mice. Urine albumin/creatinine ratio was higher in hsFlt-1-e15a-treated mice than in controls (GD18, p = 0.04; PPD8, p = 0.03), and msFlt-1(1-3)-treated mice had marked proteinuria postpartum (PPD8, p = 4×10⁻⁵). Focal glomerular changes were detected in hsFlt-1-e15a and msFlt-1(1-3)-treated mice. Aortic ring microvessel outgrowth was decreased in hsFlt-1-e15a (p = 0.007) and msFlt-1(1-3)-treated (p = 0.02) mice. Full-length msFlt-1-i13 expression was unique for the placenta. In hsFlt-1-e15a-treated mice, the number of pups (p = 0.046), total weight of living pups (p = 0.04) and maternal weights (p = 0.04) were higher than in controls. These differences were not observed in truncated msFlt-1(1-3)-treated mice.

Conclusions

Truncated msFlt-1(1-3) simulated the preeclampsia-promoting effects of full-length hsFlt-1. MsFlt-1(1-3) had strong effect on maternal endothelium but not on placentas and embryos. In contrast, hsFlt-1-e15a induced preeclampsia-like symptoms; however, it also increased litter size. In accord with the predominant placental expression of hsFlt-1-e15a and msFlt-1-i13, full-length sFlt-1 may have a role in the regulation of embryonic development. These observations point to the difference in the biological effects of full-length and truncated sFlt-1 and the changes in the effect of full-length sFlt-1 during pregnancy, and may have important implications in the management of preeclampsia.

Prevalence and clinical significance of sterile intra-amniotic inflammation in patients with preterm labor and intact membranes

PROBLEM

Inflammation and infection play a major role in preterm birth. The purpose of this study was to (i) determine the prevalence and clinical significance of sterile intra-amniotic inflammation and (ii) examine the relationship between amniotic fluid (AF) concentrations of high mobility group box-1 (HMGB1) and the interval from amniocentesis to delivery in patients with sterile intra-amniotic inflammation.

METHOD OF STUDY

AF samples obtained from 135 women with preterm labor and intact membranes were analyzed using cultivation techniques as well as broad-range PCR and mass spectrometry (PCR/ESI-MS). Sterile intra-amniotic inflammation was defined when patients with negative AF cultures and without evidence of microbial footprints had intra-amniotic inflammation (AF interleukin-6 ≥ 2.6 ng/mL).

RESULTS

(i) The frequency of sterile intra-amniotic inflammation was significantly greater than that of microbial-associated intra-amniotic inflammation [26% (35/135) versus 11% (15/135); (P = 0.005)], (ii) patients with sterile intra-amniotic inflammation delivered at comparable gestational ages had similar rates of acute placental inflammation and adverse neonatal outcomes as patients with microbial-associated intra-amniotic inflammation, and (iii) patients with sterile intra-amniotic inflammation and high AF concentrations of HMGB1 (≥8.55 ng/mL) delivered earlier than those with low AF concentrations of HMGB1 (P = 0.02).

CONCLUSION

(i) Sterile intra-amniotic inflammation is more frequent than microbial-associated intra-amniotic inflammation, and (ii) we propose that danger signals participate in sterile intra-amniotic inflammation in the setting of preterm labor.

Immune cells in term and preterm labor

Labor resembles an inflammatory response that includes secretion of cytokines/chemokines by resident and infiltrating immune cells into reproductive tissues and the maternal/fetal interface. Untimely activation of these inflammatory pathways leads to preterm labor, which can result in preterm birth. Preterm birth is a major determinant of neonatal mortality and morbidity; therefore, the elucidation of the process of labor at a cellular and molecular level is essential for understanding the pathophysiology of preterm labor. Here, we summarize the role of innate and adaptive immune cells in the physiological or pathological activation of labor. We review published literature regarding the role of innate and adaptive immune cells in the cervix, myometrium, fetal membranes, decidua and the fetus in late pregnancy and labor at term and preterm. Accumulating evidence suggests that innate immune cells (neutrophils, macrophages and mast cells) mediate the process of labor by releasing pro-inflammatory factors such as cytokines, chemokines and matrix metalloproteinases. Adaptive immune cells (T-cell subsets and B cells) participate in the maintenance of fetomaternal tolerance during pregnancy, and an alteration in their function or abundance may lead to labor at term or preterm. Also, immune cells that bridge the innate and adaptive immune systems (natural killer T (NKT) cells and dendritic cells (DCs)) seem to participate in the pathophysiology of preterm labor. In conclusion, a balance between innate and adaptive immune cells is required in order to sustain pregnancy; an alteration of this balance will lead to labor at term or preterm.

Cervical strain determined by ultrasound elastography and its association with spontaneous preterm delivery

OBJECTIVE

To determine if there is an association between cervical strain, evaluated using ultrasound elastography, and spontaneous preterm delivery (sPTD) <37 weeks of gestation.

METHODS

One hundred and eighty nine (189) women at 16-24 weeks of gestation were evaluated. Ultrasound elastography was used to estimate cervical strain in three anatomical planes: one mid-sagittal in the same plane used for cervical length measurement, and two cross sectional images: one at the level of the internal cervical os, and the other at the level of the external cervical os. In each plane, two regions of interest (endocervix and entire cervix) were examined; a total of six regions of interest were evaluated.

RESULTS

The prevalence of sPTD was 11% (21/189). Strain values from each of the six cervical regions correlated weakly with cervical length (from r=-0.24, P<0.001 to r=-0.03, P=0.69). Strain measurements obtained in a cross sectional view of the internal cervical os were significantly associated with sPTD. Women with strain values ≤25th centile in the endocervical canal (0.19) and in the entire cervix (0.14) were 80% less likely to have a sPTD than women with strain values >25th centile [endocervical: odds ratio (OR) 0.2; 95% confidence interval (CI), 0.03-0.96; entire cervix: OR 0.17; 95% CI, 0.03-0.9]. Additional adjustment for gestational age, race, smoking status, parity, maternal age, pre-pregnancy body mass index, and previous preterm delivery did not appreciably alter the magnitude or statistical significance of these associations. Strain values obtained from the external cervical os and from the sagittal view were not associated with sPTD.

CONCLUSION

Low strain values in the internal cervical os were associated with a significantly lower risk of spontaneous preterm delivery <37 weeks of gestation.

Distinct cervical microRNA profiles are present in women destined to have a preterm birth

OBJECTIVE

Although premature cervical remodeling is involved in preterm birth (PTB), the molecular pathways that are involved have not been elucidated fully. MicroRNAs (miRNAs) that are highly conserved single-stranded noncoding RNAs that play a crucial role in gene regulation have now been identified as important players in disease states. The objective of this study was to determine whether miRNA profiles in cervical cells are different in women who are destined to have a PTB compared with a term birth.

STUDY DESIGN

A nested case-control study was performed. With the use of a noninvasive method, cervical cells were obtained at 2 time points in pregnancy. The cervical cell miRNA expression profiles were compared between women who ultimately had a PTB (n = 10) compared with a term birth (n = 10). MiRNA expression profiles were created with the Affymetrix GeneChip miRNA Array. The data were analyzed with the Significance of Analysis of Microarrays and Principle Components Analyses. A false-discovery rate of 20% was used to determine the most differentially expressed miRNAs. Validation was performed with quantitative polymerase chain reaction. In vitro studies were performed to confirm expression and regulation of select miRNAs.

RESULTS

With a false-discovery rate of 20% of the 5640 miRNAs that were analyzed on the array, 99 miRNAs differed between those with a PTB vs a term birth. Qualitative polymerase chain reaction validated the array findings. In vitro studies confirmed expression of select miRNAs in cervical cells.

CONCLUSION

MiRNA profiles in cervical cells may distinguish women who are at risk for PTB months before the outcome. With the large downstream effects of miRNAs on gene expression, these studies provide a new understanding of the processes that are involved in premature cervical remodeling and allow for the discovery of new therapeutic targets.

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

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Evidence for independent evolution of functional progesterone withdrawal in primates and guinea pigs

Humans and guinea pigs differ from other mammals by maintaining high progesterone levels in pregnancy all the way through birth. Here we investigated the evolutionary history of this condition and conclude that it evolved independently in the human and the guinea pig lineages. Furthermore we investigated the gene expression during cervical re-modelling and found only a small number of gene regulatory events that seem to be common between humans and guinea pigs.

Background and objectives: Cervix remodeling (CRM) is a critical process in preparation for parturition. Early cervix shortening is a powerful clinical predictor of preterm birth, and thus understanding how CRM is regulated is important for the prevention of prematurity. Humans and other primates differ from most other mammals by the maintenance of high levels of systemic progesterone concentrations. Humans have been hypothesized to perform functional progesterone withdrawal (FPW). Guinea pigs are similar to humans in maintaining high-progesterone concentrations through parturition, thus making them a prime model for studying CRM. Here, we analyze the phylogenetic history of FPW and document gene expression in the guinea pig uterine cervix.

Methodology: Data on progesterone withdrawal were collected from the literature, and character evolution was analyzed. Uterine cervix samples were collected from non-pregnant, mid-pregnant and late pregnant guinea pigs. RNA was extracted and sequenced. Relative transcript levels were estimated and compared among sample groups.

Results: The phylogenetic analysis shows that FPW evolved independently in primates and guinea pigs. The transcriptome data confirms that guinea pigs down-regulate progesterone receptor toward parturition, in contrast to humans. Some of the similarities between human and guinea pig are: down-regulation of estrogen receptor, up-regulation of VCAN and IGFBP4 as well as likely involvement of prostaglandins.

Conclusions and implications: (i) FPW in guinea pigs evolved independently from that in primates. (ii) A small set of conserved gene regulatory changes has been detected.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

Analysis and correction of crosstalk effects in pathway analysis

Identifying the pathways that are significantly impacted in a given condition is a crucial step in understanding the underlying biological phenomena. All approaches currently available for this purpose calculate a P-value that aims to quantify the significance of the involvement of each pathway in the given phenotype. These P-values were previously thought to be independent. Here we show that this is not the case, and that many pathways can considerably affect each other's P-values through a "crosstalk" phenomenon. Although it is intuitive that various pathways could influence each other, the presence and extent of this phenomenon have not been rigorously studied and, most importantly, there is no currently available technique able to quantify the amount of such crosstalk. Here, we show that all three major categories of pathway analysis methods (enrichment analysis, functional class scoring, and topology-based methods) are severely influenced by crosstalk phenomena. Using real pathways and data, we show that in some cases pathways with significant P-values are not biologically meaningful, and that some biologically meaningful pathways with nonsignificant P-values become statistically significant when the crosstalk effects of other pathways are removed. We describe a technique able to detect, quantify, and correct crosstalk effects, as well as identify independent functional modules. We assessed this novel approach on data from four experiments involving three phenotypes and two species. This method is expected to allow a better understanding of individual experiment results, as well as a more refined definition of the existing signaling pathways for specific phenotypes.