Molecular evidence of functional progesterone withdrawal in human myometrium

Inflammatory mechanisms of preterm labor and emerging anti-inflammatory interventions

Preterm birth is a major public health concern, requiring a deeper understanding of its underlying inflammatory mechanisms and to develop effective therapeutic strategies. This review explores the complex interaction between inflammation and preterm labor, highlighting the pivotal role of the dysregulation of inflammation in triggering premature delivery. The immunological environment of pregnancy, characterized by a fragile balance of immune tolerance and resistance, is disrupted in preterm labor, leading to a pathological inflammatory response. Feto-maternal infections, among other pro-inflammatory stimuli, trigger the activation of toll-like receptors and the production of pro-inflammatory mediators, promoting uterine contractility and cervical ripening. Emerging anti-inflammatory therapeutics offer promising approaches for the prevention of preterm birth by targeting key inflammatory pathways. From TLR-4 antagonists to chemokine and interleukin receptor antagonists, these interventions aim to modulate the inflammatory environment and prevent adverse pregnancy outcomes. In conclusion, a comprehensive understanding of the inflammatory mechanisms leading to preterm labor is crucial for the development of targeted interventions in hope of reducing the incidence of preterm birth and improving neonatal health outcomes.

The hormonal control of parturition

Parturition is a complex physiological process that must occur in a reliable manner and at an appropriate gestation stage to ensure a healthy newborn and mother. To this end, hormones that affect the function of the gravid uterus, especially progesterone (P4), 17β-estradiol (E2), oxytocin (OT), and prostaglandins (PGs), play pivotal roles. P4 via the nuclear P4 receptor (PR) promotes uterine quiescence and for most of pregnancy exerts a dominant block to labor. Loss of the P4 block to parturition in association with a gain in prolabor actions of E2 are key transitions in the hormonal cascade leading to parturition. P4 withdrawal can occur through various mechanisms depending on species and physiological context. Parturition in most species involves inflammation within the uterine tissues and especially at the maternal-fetal interface. Local PGs and other inflammatory mediators may initiate parturition by inducing P4 withdrawal. Withdrawal of the P4 block is coordinated with increased E2 actions to enhance uterotonic signals mediated by OT and PGs to promote uterine contractions, cervix softening, and membrane rupture, i.e., labor. This review examines recent advances in research to understand the hormonal control of parturition, with focus on the roles of P4, E2, PGs, OT, inflammatory cytokines, and placental peptide hormones together with evolutionary biology of and implications for clinical management of human parturition.

Decline in corepressor CNOT1 in the pregnant myometrium near term impairs progesterone receptor function and increases contractile gene expression

Progesterone (P4), acting via its nuclear receptor (PR), is critical for pregnancy maintenance by suppressing proinflammatory and contraction-associated protein (CAP)/contractile genes in the myometrium. P4/PR partially exerts these effects by tethering to NF-κB bound to their promot-ers, thereby decreasing NF-κB transcriptional activity. However, the underlying mechanisms whereby P4/PR interaction blocks proinflammatory and CAP gene expression are not fully understood. Herein, we characterized CCR-NOT transcription complex subunit 1 (CNOT1) as a corepressor that also interacts within the same chromatin complex as PR-B. In mouse myome-trium increased expression of CAP genes Oxtr and Cx43 at term coincided with a marked decline in expression and binding of CNOT1 to NF-κB-response elements within the Oxtr and Cx43 promoters. Increased CAP gene expression was accompanied by a pronounced decrease in enrichment of repressive histone marks and increase in enrichment of active histone marks to this genomic region. These changes in histone modification were associated with changes in expression of corresponding histone modifying enzymes. Myometrial tissues from P4-treated 18.5 dpc pregnant mice manifested increased Cnot1 expression at 18.5 dpc, compared to vehicle-treated controls. P4 treatment of PR-expressing hTERT-HM cells enhanced CNOT1 expression and its recruitment to PR bound NF-κB-response elements within the CX43 and OXTR promoters. Furthermore, knockdown of CNOT1 significantly increased expression of contractile genes. These novel findings suggest that decreased expression and DNA-binding of the P4/PR-regulated transcriptional corepressor CNOT1 near term and associated changes in histone modifications at the OXTR and CX43 promoters contribute to the induction of myometrial contractility leading to parturition.

Progesterone inactivation in decidual stromal cells: A mechanism for inflammation-induced parturition

The process of human parturition involves inflammation at the interface where fetal chorion trophoblast cells interact with maternal decidual stromal (DS) cells and maternal immune cells in the decidua (endometrium of pregnancy). This study tested the hypothesis that inflammation at the chorion-decidua interface (CDI) induces labor by negating the capacity for progesterone (P4) to block labor and that this is mediated by inactivation of P4 in DS cells by aldo-keto reductase family 1 member C1 (AKR1C1). In human, Rhesus macaque, and mouse CDI, AKR1C1 expression increased in association with term and preterm labor. In a human DS cell line and in explant cultures of term human fetal membranes containing the CDI, the prolabor inflammatory cytokine, interleukin-1ß (IL-1ß), and media conditioned by LPS-stimulated macrophages increased AKR1C1 expression and coordinately reduced nuclear P4 levels and P4 responsiveness. Loss of P4 responsiveness was overcome by inhibition of AKR1C1 activity, inhibition of AKR1C1 expression, and bypassing AKR1C1 activity with a P4 analog that is not metabolized by AKR1C1. Increased P4 activity in response to AKR1C1 inhibition was prevented by the P4 receptor antagonist RU486. Pharmacologic inhibition of AKR1C1 activity prevented parturition in a mouse model of inflammation-induced preterm parturition. The data suggest that inflammatory stimuli at the CDI drive labor by inducing AKR1C1-mediated P4 inactivation in DS cells and that inhibiting and/or bypassing of AKR1C1-mediated P4 inactivation is a plausible therapeutic strategy to mitigate the risk of inflammation-associated preterm birth.

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

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

EHD1 impaired decidualization of endometrial stromal cells in recurrent implantation failure: role of SENP1 in modulating progesterone receptor signalling†

Recurrent implantation failure (RIF) patients exhibit poor endometrial receptivity and abnormal decidualization with reduced effectiveness and exposure to progesterone, which is an intractable clinical problem. However, the associated molecular mechanisms remain elusive. We found that EH domain containing 1 (EHD1) expression was abnormally elevated in RIF and linked to aberrant endometrial decidualization. Here we show that EHD1 overexpressed in human endometrial stromal cells significantly inhibited progesterone receptor (PGR) transcriptional activity and the responsiveness to progesterone. No significant changes were observed in PGR mRNA levels, while a significant decrease in progesterone receptor B (PRB) protein level. Indeed, EHD1 binds to the PRB protein, with the K388 site crucial for this interaction. Overexpression of EHD1 promotes the SUMOylation and ubiquitination of PRB, leading to the degradation of the PRB protein. Supplementation with the de-SUMOylated protease SENP1 ameliorated EHD1-repressed PRB transcriptional activity. To establish a functional link between EHD1 and the PGR signalling pathway, sg-EHD1 were utilized to suppress EHD1 expression in HESCs from RIF patients. A significant increase in the expression of prolactin and insulin-like growth factor-binding protein 1 was detected by interfering with the EHD1. In conclusion, we demonstrated that abnormally high expression of EHD1 in endometrial stromal cells attenuated the activity of PRB associated with progesterone resistance in a subset of women with RIF.

Integrative analysis of noncoding mutations identifies the druggable genome in preterm birth

Preterm birth affects ~10% of pregnancies in the US. Despite familial associations, identifying at-risk genetic loci has been challenging. We built deep learning and graphical models to score mutational effects at base resolution via integrating the pregnant myometrial epigenome and large-scale patient genomes with spontaneous preterm birth (sPTB) from European and African American cohorts. We uncovered previously unidentified sPTB genes that are involved in myometrial muscle relaxation and inflammatory responses and that are regulated by the progesterone receptor near labor onset. We studied genomic variants in these genes in our recruited pregnant women administered progestin prophylaxis. We observed that mutation burden in these genes was predictive of responses to progestin treatment for preterm birth. To advance therapeutic development, we screened ~4000 compounds, identified candidate molecules that affect our identified genes, and experimentally validated their therapeutic effects on regulating labor. Together, our integrative approach revealed the druggable genome in preterm birth and provided a generalizable framework for studying complex diseases.

Regulation of 20α-Hydroxysteroid Dehydrogenase Expression in Term Pregnant Human Myometrium Ex Vivo

Metabolic inactivation of progesterone within uterine myocytes by 20α-hydroxysteroid dehydrogenase (20α-HSD) has been postulated as a mechanism contributing to functional progesterone withdrawal at term. In humans, 20α-HSD is encoded by the gene AKR1C1. Myometrial AKR1C1 mRNA abundance has been reported to increase significantly during labor at term. In spontaneous preterm labor, however, we previously found no increase in AKR1C1 mRNA level in the myometrium except for preterm labor associated with clinical chorioamnionitis. This suggests that increased 20α-HSD activity is a mechanism through which inflammation drives progesterone withdrawal in preterm labor. In this study, we have determined the effects of various treatments of therapeutic relevance on AKR1C1 expression in pregnant human myometrium in an ex vivo culture system. AKR1C1 expression increased spontaneously during 48 h culture (p < 0.0001), consistent with the myometrium transitioning to a labor-like phenotype ex vivo, as reported previously. Serum supplementation, prostaglandin F2α, phorbol myristate acetate, and mechanical stretch had no effect on the culture-induced increase, whereas progesterone (p = 0.0058) and cAMP (p = 0.0202) further upregulated AKR1C1 expression. In contrast, culture-induced upregulation of AKR1C1 expression was dose-dependently repressed by three histone/protein deacetylase inhibitors: trichostatin A at 5 (p = 0.0172) and 25 µM (p = 0.0115); suberoylanilide hydroxamic acid at 0.5 (p = 0.0070), 1 (p = 0.0045), 2.5 (p = 0.0181), 5 (p = 0.0066) and 25 µM (p = 0.0014); and suberoyl bis-hydroxamic acid at 5 (p = 0.0480) and 25 µM (p = 0.0238). We propose the inhibition of histone/protein deacetylation helps to maintain the anti-inflammatory, pro-quiescence signaling of progesterone in pregnant human myometrium by blocking its metabolic inactivation. Histone deacetylase inhibitors may represent a class of agents that preserve or restore the progesterone sensitivity of the pregnant uterus.

Serpin family E member 1 enhances myometrium contractility by increasing ATP production during labor

The uterine contraction during labor, a process with repetitive hypoxia and high energy consumption, is essential for successful delivery. However, the molecular mechanism of myometrial contraction regulation is unknown. Serpin family E member 1 (SERPINE1), one of the most upregulated genes in laboring myometrium in both transcriptome and proteome, was highlighted in our previous study. Here, we confirmed SERPINE1 is upregulated in myometrium during labor. Blockade of SERPINE1 using small interfering RNA (siRNA) or inhibitor (Tiplaxtinin) under hypoxic conditions in myocytes or myometrium in vitro showed a decrease contractility, which was achieved by regulating ATP production. Chromatin immunoprecipitation (ChIP-seq), Co-immunoprecipitation (Co-IP), and glutathione-S-transferase (GST) pull down explored that the promoter of SERPINE1 is directly activated by hypoxia-inducible factor-1α (HIF-1α) and SERPINE1 interacts with ATP Synthase Peripheral Stalk Subunit F6 (ATP5PF). Together they enhance hypoxia driven myometrial contraction by maintaining ATP production in the key oxidative phosphorylation pathway. The results provide new insight for uterine contraction regulation, and potential novel therapeutic targets for labor management.

Progesterone control of myometrial contractility

During pregnancy, the primary function of the uterus is to be quiescent and not contract, which allows the growing fetus to develop and mature. A uterine muscle layer, myometrium, is composed of smooth muscle cells (SMCs). Before the onset of labor contractions, the uterine SMCs experience a complex biochemical and molecular transformation involving the expression of contraction-associated proteins. Labor is initiated when genes in SMCs are activated in response to a combination of hormonal, inflammatory and mechanical signals. In this review, we provide an overview of molecular mechanisms regulating the process of parturition in humans, focusing on the hormonal control of the myometrium, particularly the steroid hormone progesterone. The primary reason for discussing the regulation of myometrial contractility by progesterone is the importance of the clinical problem of preterm birth. It is thought that the hormonal mechanisms regulating premature uterine contractions represent an untimely triggering of the normal events occurring during term parturition. Yet, our knowledge of the complex and redundant hormonal pathways controlling uterine contractile activity leading to delivery of the neonate remains incomplete. Finally, we introduce recent animal studies using a novel class of drugs, Selective Progesterone Receptor Modulators, targeting progesterone signaling to prevent premature myometrial contractions.

The transition to motherhood: linking hormones, brain and behaviour

We are witnessing a stark increase in scientific interest in the neurobiological processes associated with pregnancy and maternity. Convergent evidence suggests that around the time of labour, first-time mothers experience a specific pattern of neuroanatomical changes that are associated with maternal behaviour. Here we provide an overview of the human neurobiological adaptations of motherhood, focusing on the interplay between pregnancy-related steroid and peptide hormones, and neuroplasticity in the brain. We discuss which brain plasticity mechanisms might underlie the structural changes detected by MRI, which hormonal systems are likely to contribute to such neuroanatomical changes and how these brain mechanisms may be linked to maternal behaviour. This Review offers an overarching framework that can serve as a roadmap for future investigations.

Upregulated TIMP1 facilitates and coordinates myometrial contraction by decreasing collagens and cell adhesive capacity during human labor

Myometrial contraction is one of the key events involved in parturition. Increasing evidence suggests the importance of the extracellular matrix (ECM) in this process, in addition to the functional role of myometrial smooth muscle cells, and our previous study identified an upregulated tissue inhibitor of metalloproteinase 1 (TIMP1) in human laboring myometrium compared to nonlabor samples. This study aimed to further explore the potential role of TIMP1 in myometrial contraction. First, we confirmed increased myometrial TIMP1 levels in labor and during labor with cervical dilation using transcriptomic and proteomic analyses, followed by real-time PCR, western blotting, and immunohistochemistry. Then, a cell contraction assay was performed to verify the decreased contractility after TIMP1 knockdown in vitro. To further understand the underlying mechanism, we used RNA-sequencing analysis to reveal the upregulated genes after TIMP1 knockdown; these genes were enriched in collagen fibril organization, cell adhesion, and ECM organization. Subsequently, a human matrix metalloproteinase (MMP) array and collagen staining were performed to determine the TIMPs, MMPs and collagens in laboring and nonlabor myometrium. A real-time cell adhesion assay was used to detect cell adhesive capacity. The results showed upregulated MMP8 and MMP9, downregulated collagens, and attenuated cell adhesive capacity in laboring myometrium, while lower MMP levels and higher collagen levels and cell adhesive capacity were observed in nonlabor. Moreover, TIMP1 knockdown led to restoration of cell adhesive capacity. Together, these results indicate that upregulated TIMP1 during labor facilitates and coordinates myometrial contraction by decreasing collagen and cell adhesive capacity, which may provide effective strategies for the regulation of myometrial contraction.

Developmental reprogramming of myometrial stem cells by endocrine disruptor linking to risk of uterine fibroids

BACKGROUND

The stage, when tissues and organs are growing, is very vulnerable to environmental influences, but it's not clear how exposure during this time causes changes to the epigenome and increases the risk of hormone-related illnesses like uterine fibroids (UFs).

METHODS

Developmental reprogramming of myometrial stem cells (MMSCs), the putative origin from which UFs originate, was investigated in vitro and in the Eker rat model by RNA-seq, ChIP-seq, RRBS, gain/loss of function analysis, and luciferase activity assays.

RESULTS

When exposed to the endocrine-disrupting chemical (EDC) diethylstilbestrol during Eker rat development, MMSCs undergo a reprogramming of their estrogen-responsive transcriptome. The reprogrammed genes in MMSCs are known as estrogen-responsive genes (ERGs) and are activated by mixed lineage leukemia protein-1 (MLL1) and DNA hypo-methylation mechanisms. Additionally, we observed a notable elevation in the expression of ERGs in MMSCs from Eker rats exposed to natural steroids after developmental exposure to EDC, thereby augmenting estrogen activity.

CONCLUSION

Our studies identify epigenetic mechanisms of MLL1/DNA hypo-methylation-mediated MMSC reprogramming. EDC exposure epigenetically targets MMSCs and leads to persistent changes in the expression of a subset of ERGs, imparting a hormonal imprint on the ERGs, resulting in a "hyper-estrogenic" phenotype, and increasing the hormone-dependent risk of UFs.

Predicting labor onset relative to the estimated date of delivery using smart ring physiological data

The transition from pregnancy into parturition is physiologically directed by maternal, fetal and placental tissues. We hypothesize that these processes may be reflected in maternal physiological metrics. We enrolled pregnant participants in the third-trimester (n = 118) to study continuously worn smart ring devices monitoring heart rate, heart rate variability, skin temperature, sleep and physical activity from negative temperature coefficient, 3-D accelerometer and infrared photoplethysmography sensors. Weekly surveys assessed labor symptoms, pain, fatigue and mood. We estimated the association between each metric, gestational age, and the likelihood of a participant's labor beginning prior to (versus after) the clinical estimated delivery date (EDD) of 40.0 weeks with mixed effects regression. A boosted random forest was trained on the physiological metrics to predict pregnancies that naturally passed the EDD versus undergoing onset of labor prior to the EDD. Here we report that many raw sleep, activity, pain, fatigue and labor symptom metrics are correlated with gestational age. As gestational age advances, pregnant individuals have lower resting heart rate 0.357 beats/minute/week, 0.84 higher heart rate variability (milliseconds) and shorter durations of physical activity and sleep. Further, random forest predictions determine pregnancies that would pass the EDD with accuracy of 0.71 (area under the receiver operating curve). Self-reported symptoms of labor correlate with increased gestational age and not with the timing of labor (relative to EDD) or onset of spontaneous labor. The use of maternal smart ring-derived physiological data in the third-trimester may improve prediction of the natural duration of pregnancy relative to the EDD.

A prolonged latent phase: An early career in oxytocin during birth

•The author, a nurse-midwife scientist, shares her path to the study of the causes and consequences of clinical oxytocin use.•This paper highlights mentors and key research that informed new thinking about the role of oxytocin during parturition.•Future directions for improving maternal care during childbirth are presented, including genetic and epigenetic perspectives.

Preterm labor with and without chorioamnionitis is associated with activation of myometrial inflammatory networks: a comprehensive transcriptomic analysis

BACKGROUND

The onset of preterm labor is associated with inflammation. Previous studies suggested that this is distinct from the inflammation observed during term labor. Our previous work on 44 genes differentially expressed in myometria in term labor demonstrated a different pattern of gene expression from that observed in preterm laboring and nonlaboring myometria. We found increased expression of inflammatory genes in preterm labor associated with chorioamnionitis, but in the absence of chorioamnionitis observed no difference in gene expression in preterm myometria regardless of laboring status, suggesting that preterm labor is associated with different myometrial genes or signals originating from outside the myometrium. Given that a small subset of genes were assessed, this study aimed to use RNA sequencing and bioinformatics to assess the myometrial transcriptome during preterm labor in the presence and absence of chorioamnionitis.

OBJECTIVE

This study aimed to comprehensively determine protein-coding transcriptomic differences between preterm nonlaboring and preterm laboring myometria with and without chorioamnionitis.

STUDY DESIGN

Myometria were collected at cesarean delivery from preterm patients not in labor (n=16) and preterm patients in labor with chorioamnionitis (n=8) or without chorioamnionitis (n=6). Extracted RNA from myometrial tissue was prepared and sequenced using Illumina NovaSeq. Gene expression was quantified by mapping the sequence reads to the human reference genome (hg38). Differential gene expression analysis, gene set enrichment analysis, and weighted gene coexpression network analysis were used to comprehensively interrogate transcriptomic differences and their associated biology.

RESULTS

Differential gene expression analysis comparing preterm patients in labor with chorioamnionitis with preterm patients not in labor identified 931 differentially expressed genes, whereas comparing preterm patients in labor without chorioamnionitis with preterm patients not in labor identified no statistically significant gene expression changes. In contrast, gene set enrichment analysis and weighted gene coexpression network analysis demonstrated that preterm labor with and without chorioamnionitis was associated with enrichment of pathways involved in activation of the innate immune system and inflammation, and activation of G protein-coupled receptors. Key genes identified included chemotactic CYP4F3, CXCL8, DOCK2, and IRF1 in preterm labor with chorioamnionitis and CYP4F3, FCAR, CHUK, and IL13RA2 in preterm labor without chorioamnionitis. There was marked overlap in the pathways enriched in both preterm labor subtypes.

CONCLUSION

Differential gene expression analysis demonstrated that myometria from preterm patients in labor without chorioamnionitis and preterm patients not in labor were transcriptionally similar, whereas the presence of chorioamnionitis was associated with marked gene changes. In contrast, comprehensive bioinformatic analysis indicated that preterm labor with or without chorioamnionitis was associated with innate immune activation. All causes of preterm labor were associated with activation of the innate immune system, but this was more marked in the presence of chorioamnionitis. These data suggest that anti-inflammatory therapy may be relevant in managing preterm labor of all etiologies.

cAMP Compartmentalisation in Human Myometrial Cells

Preterm birth is the leading cause of childhood mortality and morbidity. A better understanding of the processes that drive the onset of human labour is essential to reduce the adverse perinatal outcomes associated with dysfunctional labour. Beta-mimetics, which activate the myometrial cyclic adenosine monophosphate (cAMP) system, successfully delay preterm labour, suggesting a key role for cAMP in the control of myometrial contractility; however, the mechanisms underpinning this regulation are incompletely understood. Here we used genetically encoded cAMP reporters to investigate cAMP signalling in human myometrial smooth muscle cells at the subcellular level. We found significant differences in the dynamics of the cAMP response in the cytosol and at the plasmalemma upon stimulation with catecholamines or prostaglandins, indicating compartment-specific handling of cAMP signals. Our analysis uncovered significant disparities in the amplitude, kinetics, and regulation of cAMP signals in primary myometrial cells obtained from pregnant donors compared with a myometrial cell line and found marked response variability between donors. We also found that in vitro passaging of primary myometrial cells had a profound impact on cAMP signalling. Our findings highlight the importance of cell model choice and culture conditions when studying cAMP signalling in myometrial cells and we provide new insights into the spatial and temporal dynamics of cAMP in the human myometrium.

20α-Hydroxysteroid Dehydrogenase Expression in the Human Myometrium at Term and Preterm Birth: Relationships to Fetal Sex and Maternal Body Mass Index

The mechanism by which human labor is initiated in the presence of elevated circulating progesterone levels remains unknown. Recent evidence indicates that the progesterone-metabolizing enzyme, 20α-hydroxysteroid dehydrogenase (20α-HSD), encoded by the gene AKR1C1, may contribute to functional progesterone withdrawal. We found that AKR1C1 expression significantly increased with labor onset in term myometrium, but not in preterm myometrium. Among preterm laboring deliveries, clinically diagnosed chorioamnionitis was associated with significantly elevated AKR1C1 expression. AKR1C1 expression positively correlated with BMI before labor and negatively correlated with BMI during labor. Analysis by fetal sex showed that AKR1C1 expression was significantly higher in women who delivered male babies compared to women who delivered female babies at term, but not preterm. Further, in pregnancies where the fetus was female, AKR1C1 expression positively correlated with the mother's age and BMI at the time of delivery. In conclusion, the increase in myometrial AKR1C1 expression with term labor is consistent with 20α-HSD playing a role in local progesterone metabolism to promote birth. Interestingly, this role appears to be specific to term pregnancies where the fetus is male. Upregulated AKR1C1 expression in the myometrium at preterm in-labor with clinical chorioamnionitis suggests that increased 20α-HSD activity is a mechanism through which inflammation drives progesterone withdrawal in preterm labor. The link between AKR1C1 expression and maternal BMI may provide insight into why maternal obesity is often associated with dysfunctional labor. Higher myometrial AKR1C1 expression in male pregnancies may indicate fetal sex-related differences in the mechanisms that precipitate labor onset at term.

In Vivo Genome-Wide PGR Binding in Pregnant Human Myometrium Identifies Potential Regulators of Labor

The alterations in myometrial biology during labor are not well understood. The myometrium is the contractile portion of the uterus and contributes to labor, a process that may be regulated by the steroid hormone progesterone. Thus, human myometrial tissues from term pregnant in-active-labor (TIL) and term pregnant not-in-labor (TNIL) subjects were used for genome-wide analyses to elucidate potential future preventive or therapeutic targets involved in the regulation of labor. Using myometrial tissues directly subjected to RNA sequencing (RNA-seq), progesterone receptor (PGR) chromatin immunoprecipitation sequencing (ChIP-seq), and histone modification ChIP-seq, we profiled genome-wide changes associated with gene expression in myometrial smooth muscle tissue in vivo. In TIL myometrium, PGR predominantly occupied promoter regions, including the classical progesterone response element, whereas it bound mainly to intergenic regions in TNIL myometrial tissue. Differential binding analysis uncovered over 1700 differential PGR-bound sites between TIL and TNIL, with 1361 sites gained and 428 lost in labor. Functional analysis identified multiple pathways involved in cAMP-mediated signaling enriched in labor. A three-way integration of the data for ChIP-seq, RNA-seq, and active histone marks uncovered the following genes associated with PGR binding, transcriptional activation, and altered mRNA levels: ATP11A, CBX7, and TNS1. In vitro studies showed that ATP11A, CBX7, and TNS1 are progesterone responsive. We speculate that these genes may contribute to the contractile phenotype of the myometrium during various stages of labor. In conclusion, we provide novel labor-associated genome-wide events and PGR-target genes that can serve as targets for future mechanistic studies.

Is human labor at term an inflammatory condition?†

Parturition at term in normal pregnancy follows a predictable sequence of events. There is some evidence that a state of inflammation prevails in the reproductive tissues during labor at term, but it is uncertain whether this phenomenon is the initiating signal for parturition. The absence of a clear temporal sequence of inflammatory events prior to labor casts doubt on the concept that normal human labor at term is primarily the result of an inflammatory cascade. This review examines evidence linking parturition and inflammation in order to address whether inflammation is a cause of labor, a consequence of labor, or a separate but related phenomenon. Finally, we identify and suggest ways to reconcile inconsistencies regarding definitions of labor onset in published research, which may contribute to the variability in conclusions regarding the genesis and maintenance of parturition. A more thorough understanding of the processes underlying normal parturition at term may lead to novel insights regarding abnormal labor, including spontaneous preterm labor, preterm premature rupture of the fetal membranes, and dysfunctional labor, and the role of inflammation in each.

MYB and ELF3 differentially modulate labor-inducing gene expression in myometrial cells

Spontaneous uterine contractions are initiated when smooth muscle cells (SMCs) within the uterine muscle, or myometrium, transition from a functionally dormant to an actively contractile phenotype at the end of the pregnancy period. We know that this process is accompanied by gestational time point-specific differences in the SMC transcriptome, which can be modulated by the activator protein 1 (AP-1), nuclear factor kappa beta (NF-κβ), estrogen receptor (ER), and progesterone receptor (PR) transcription factors. Less is known, however, about the additional proteins that might assist these factors in conferring the transcriptional changes observed at labor onset. Here, we present functional evidence for the roles of two proteins previously understudied in the SMC context-MYB and ELF3-which can contribute to the regulation of labor-driving gene transcription. We show that the MYB and ELF3 genes exhibit elevated transcript expression levels in mouse and human myometrial tissues during spontaneous term labor. The expression of both genes was also significantly increased in mouse myometrium during preterm labor induced by the progesterone antagonist mifepristone (RU486), but not during infection-simulating preterm labor induced by intrauterine infusion of lipopolysaccharide (LPS). Furthermore, both MYB and ELF3 proteins affect labor-driving gene promoter activity, although in surprisingly opposing ways: Gja1 and Fos promoter activation increases in the presence of MYB and decreases in the presence of ELF3. Collectively, our study adds to the current understanding of the transcription factor network that defines the transcriptomes of SMCs during late gestation and implicates two new players in the control of labor timing.

Preterm Birth and Corticotrophin-Releasing Hormone as a Placental Clock

Preterm birth worldwide remains a significant cause of neonatal morbidity and mortality, yet the exact mechanisms of preterm parturition remain unclear. Preterm birth is not a single condition, but rather a syndrome with a multifactorial etiology. This multifactorial nature explains why individual predictive measures for preterm birth have had limited sensitivity and specificity. One proposed pathway for preterm birth is via placentally synthesized corticotrophin-releasing hormone (CRH). CRH is a peptide hormone that increases exponentially in pregnancy and has been implicated in preterm birth because of its endocrine, autocrine, and paracrine roles. CRH has actions that increase placental production of estriol and of the transcription factor nuclear factor-κB, that likely play a key role in activating the myometrium. CRH has been proposed as part of a placental clock, with early activation of placental production resulting in preterm birth. This article will review the current understanding of preterm birth, CRH as an initiator of human parturition, and the evidence regarding the use of CRH in the prediction of preterm birth.

The role of progesterone receptor isoforms in the myometrium

Myometrial contraction is stringently controlled throughout pregnancy and parturition. Progesterone signaling, effecting through the progesterone receptor (PR), is pivotal in modulating uterine activity. Evidence has shown that two major PR isoforms, PR-A and PR-B, have distinct activities on gene regulation, and the ratio between these isoforms determines the contractility of the myometrium at different gestational stages. Herein, we focus on the regulation of PR activity in the myometrium, especially the differential actions of the two PR isoforms, which maintain uterine quiescence during pregnancy and regulate the switch to a contractile state at the onset of labor. To demonstrate the PR regulatory network and its mechanisms of actions on myometrial activity, we summarized the findings into three parts: Regulation of PR Expression and Isoform Levels, Progesterone Receptor Interacting Factors, and Biological Processes Regulated by Myometrial Progesterone Receptor Isoforms. Recent genomic and epigenomic data, from human specimens and mouse models, are recruited to support the existing knowledge and offer new insights and future directions in myometrial biology.

Progesterone withdrawal and parturition

The steroid hormone progesterone (P4), acting via the nuclear P4 receptors (PRs) in uterine cells, is essential for the establishment and maintenance of pregnancy. P4/PR signaling maintains pregnancy by promoting uterine quiescence and blocking the contractions of labor. Withdrawal of the P4/PR block to labor induces parturition. The success of pregnancy requires the timely birth of a mature neonate to a healthy mother, and to this end, the mechanism by which the P4/PR block is withdrawn, and how that process is physiologically controlled is critical. This review examines current understanding of cell and molecular biology of P4/PR withdrawal in the control of parturition.

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.

Impact of progesterone on innate immunity and cell death after influenza A virus H1N1 2009 infection of lung and placental cells in vitro

The influenza A virus (IAV) 2009 H1N1 pandemic was associated with an increased risk of maternal mortality, preterm birth, and stillbirth. The underlying mechanism for severe maternal lung disease and stillbirth is incompletely understood, but IAV infection is known to activate innate immunity triggering the release of cytokines. Elucidating the impact of progesterone (P4), a key hormone elevated in pregnancy, on the innate immune and inflammatory response to IAV infection is a critical step in understanding the pathogenesis of adverse maternal-fetal outcomes. IAV H1N1 pdm/09 was used to infect cell lines Calu-3 (lung adenoma) and ACH-3P (extravillous trophoblast) with or without P4 (100 nM) at multiplicity of infections (MOI) 0, 0.5, and 3. Cells were harvested at 24 and 48 hours post infection (hpi) and analyzed for cytopathic effects (CPE), replicating virus (TCID50), cytotoxicity (Lactate Dehydrogenase (LDH) assay), and NLRP3 inflammasome activation (caspase-1 activity, fluorometric assay). Activation of antiviral innate immunity was quantified (RT-qPCR, Luminex) by measuring biomarker gene and protein expression of innate immune activation (IFIT1, IFNB), inflammation (IL6), interferon signaling (MXA), chemokines (IL-8, IL-10). Both Calu-3 and ACH-3P were highly permissible to IAV infection at each timepoint as demonstrated by CPE and recovery of replicating virus. In Calu-3, progesterone treatment was associated with a significant increase in cytotoxicity, increased gene expression of IL6, and increased protein expression of IFN-β, IL-6, and IL-18. Conversely, in ACH-3P, progesterone treatment was associated with significantly suppressed cytotoxicity, decreased gene expression of IFNB, IL6 and IL1B, and increased protein expression of IFN-β and IL-6. In both cell lines, caspase-1 activity was significantly decreased after progesterone treatment, indicating NLRP3 inflammasome activation was not underlying the higher cell death in Calu-3. In summary, these data provide evidence that progesterone plays a dual role by ameliorating viral infection in the placenta but exacerbating influenza A virus-associated injury in the lung through nongenomic modulation of the innate immune response.

Vaginal Nanoformulations for the Management of Preterm Birth

Preterm birth (PTB) is a leading cause of infant morbidity and mortality in the world. In 2020, 1 in 10 infants were born prematurely in the United States. The World Health Organization estimates that a total of 15 million infants are born prematurely every year. Current therapeutic interventions for PTB have had limited replicable success. Recent advancements in the field of nanomedicine have made it possible to utilize the vaginal administration route to effectively and locally deliver drugs to the female reproductive tract. Additionally, studies using murine models have provided important insights about the cervix as a gatekeeper for pregnancy and parturition. With these recent developments, the field of reproductive biology is on the cusp of a paradigm shift in the context of treating PTB. The present review focuses on the complexities associated with treating the condition and novel therapeutics that have produced promising results in preclinical studies.

Preterm Birth Therapies to Target Inflammation

Preterm birth (PTB; defined as delivery before 37 weeks of pregnancy) is the leading cause of morbidity and mortality in infants and children aged <5 years, conferring potentially devastating short‐ and long‐term complications. Despite extensive research in the field, there is currently a paucity of medications available for PTB prevention and treatment. Over the past few decades, inflammation in gestational tissues has emerged at the forefront of PTB pathophysiology. Even in the absence of infection, inflammation alone can prematurely activate the main components of parturition resulting in uterine contractions, cervical ripening and dilatation, membrane rupture, and subsequent PTB. Mechanistic studies have identified critical elements of the complex inflammatory molecular pathways involved in PTB. Here, we discuss therapeutic options that target such key mediators with an aim to prevent, postpone, or treat PTB. We provide an overview of more traditional therapies that are currently used or being tested in humans, and we highlight recent advances in preclinical studies introducing novel approaches with therapeutic potential. We conclude that urgent collaborative action is required to address the unmet need of developing effective strategies to tackle the challenge of PTB and its complications.

Myometrial progesterone receptor determines a transcription program for uterine remodeling and contractions during pregnancy

The uterine myometrium expands and maintains contractile quiescence before parturition. While the steroid hormone progesterone blocks labor, the role of progesterone signaling in myometrial expansion remains elusive. This study investigated the myometrial functions of the progesterone receptor, PGR. Pgr ablation in mouse smooth muscle leads to subfertility, oviductal embryo retention, and impaired myometrial adaptation to pregnancy. While gross morphology between mutant and control uteri are comparable, mutant uteri manifest a decrease of 76.6% oxytocin-stimulated contractility in a pseudopregnant context with a reduced expression of intracellular calcium homeostasis genes including Pde5a and Plcb4. At mid-pregnancy, the mutant myometrium exhibits discontinuous myofibers and disarrayed extracellular matrix at the conceptus site. Transcriptome of the mutant mid-pregnant uterine wall manifests altered muscle and extracellular matrix profiles and resembles that of late-pregnancy control tissues. A survey of PGR occupancy, H3K27ac histone marks, and chromatin looping annotates cis-acting elements that may direct gene expression of mid-pregnancy uteri for uterine remodeling. Further analyses suggest that major muscle and matrix regulators Myocd and Ccn2 and smooth muscle building block genes are PGR direct downstream targets. Cataloging enhancers that are topologically associated with progesterone downstream genes reveals distinctive patterns of transcription factor binding motifs in groups of enhancers and identifies potential regulatory partners of PGR outside its occupying sites. Finally, conserved correlations are found between estimated PGR activities and RNA abundance of downstream muscle and matrix genes in human myometrial tissues. In summary, PGR is pivotal to direct the molecular program for the uterus to remodel and support pregnancy.

Birth, love, and fear: Physiological networks from pregnancy to parenthood

Pregnancy and childbirth are among the most dramatic physiological and emotional transformations of a lifetime. Despite their central importance to human survival, many gaps remain in our understanding of the temporal progression of and mechanisms underlying the transition to new parenthood. The goal of this paper is to outline the physiological and emotional development of the maternal-infant dyad from late pregnancy to the postpartum period, and to provide a framework to investigate this development using non-invasive timeseries. We focus on the interaction among neuroendocrine, emotional, and autonomic outputs in the context of late pregnancy, parturition, and post-partum. We then propose that coupled dynamics in these outputs can be leveraged to map both physiologic and pathologic pregnancy, parturition, and parenthood. This approach could address gaps in our knowledge and enable early detection or prediction of problems, with both personalized depth and broad population scale.

The immunobiology of preterm labor and birth: intra-amniotic inflammation or breakdown of maternal-fetal homeostasis

In brief

The syndrome of preterm labor comprises multiple established and novel etiologies. This review summarizes the distinct immune mechanisms implicated in preterm labor and birth and highlights potential strategies for its prevention.

Abstract

Preterm birth, the leading cause of neonatal morbidity and mortality worldwide, results from preterm labor, a syndrome that includes multiple etiologies. In this review, we have summarized the immune mechanisms implicated in intra-amniotic inflammation, the best-characterized cause of preterm labor and birth, as well as novel etiologies non-associated with intra-amniotic inflammation (i.e. formally known as idiopathic). While the intra-amniotic inflammatory responses driven by microbes (infection) or alarmins (sterile) have some overlap in the participating cellular and molecular processes, the distinct natures of these two conditions necessitate the implementation of specific approaches to prevent adverse pregnancy and neonatal outcomes. Intra-amniotic infection can be treated with the correct antibiotics, whereas sterile intra-amniotic inflammation could potentially be treated by administering a combination of anti-inflammatory drugs (e.g. betamethasone, inflammasome inhibitors, etc.). Recent evidence also supports the role of fetal T-cell activation as a newly described trigger for preterm labor and birth in a subset of cases diagnosed as idiopathic. Moreover, herein we also provide evidence of two maternally-driven immune mechanisms responsible for preterm births formerly considered to be idiopathic. First, the impairment of maternal Tregs can lead to preterm birth, likely due to the loss of immunosuppressive activity resulting in unleashed effector T-cell responses. Secondly, homeostatic macrophages were shown to be essential for maintaining pregnancy and promoting fetal development, and the adoptive transfer of homeostatic M2-polarized macrophages shows great promise for preventing inflammation-induced preterm birth. Collectively, in this review, we discuss the established and novel immune mechanisms responsible for preterm birth and highlight the potential targets for novel strategies aimed at preventing the multi-etiological syndrome of preterm labor leading to preterm birth.

A Review of Delayed Delivery Models and the Analysis Method in Mice

In humans, the incidence of post-term delivery is 1–10%. Post-term delivery significantly increases the risk of cesarean section or neonatal intensive care unit (NICU) admission. Despite these serious challenges, the cause of prolonged delivery remains unclear. Several common factors of delayed parturition between mice and humans will help elucidate the mechanisms of pregnancy and labor. At present, gene modification techniques are rapidly developing; however, there are limited reviews available describing the mouse phenotype analysis as a human model for post-term delivery. We classified the delayed-labor mice into nine types according to their causes. In mice, progesterone (P₄) maintains pregnancy, and the most common cause of delayed labor is luteolysis failure. Other contributing factors include humoral molecules in the fetus/placenta, uterine contractile dysfunction, poor cervical ripening, and delayed implantation. The etiology of delayed parturition is overexpression of the pregnancy maintenance mechanism or suppression of the labor induction mechanism. Here, we describe how to investigated their causes using mouse genetic analysis. In addition, we generated a list to identify the causes. Our review will help understand the findings obtained using the mouse model, providing a foundation for conducting more systematic research on delayed delivery.

Progesterone Receptor Signaling in the Uterus Is Essential for Pregnancy Success

The uterus plays an essential role in the reproductive health of women and controls critical processes such as embryo implantation, placental development, parturition, and menstruation. Progesterone receptor (PR) regulates key aspects of the reproductive function of several mammalian species by directing the transcriptional program in response to progesterone (P4). P4/PR signaling controls endometrial receptivity and decidualization during early pregnancy and is critical for the establishment and outcome of a successful pregnancy. PR is also essential throughout gestation and during labor, and it exerts critical roles in the myometrium, mainly by the specialized function of its two isoforms, progesterone receptor A (PR-A) and progesterone receptor B (PR-B), which display distinct and separate roles as regulators of transcription. This review summarizes recent studies related to the roles of PR function in the decidua and myometrial tissues. We discuss how PR acquired key features in placental mammals that resulted in a highly specialized and dynamic role in the decidua. We also summarize recent literature that evaluates the myometrial PR-A/PR-B ratio at parturition and discuss the efficacy of current treatment options for preterm birth.

Expression of the Costimulatory Molecule B7-H4 in the Decidua and Placental Tissues in Patients with Placental Abruption

B7 homolog 4 protein (B7-H4), a member of the B7 family, is a immunomodulatory membrane protein. The aim of the study was to evaluate the expression of this protein in the decidua and placental tissues in case of placental abruption (PA) compared to cases of retained placental tissue (RPT) and controls. Tissue samples were obtained from 47 patients with PA, 60 patients with RPT, and 41 healthy controls. The samples were stained for B7-H4 expression, analyzed by an expert pathologist, and a semi-quantitative scale was applied. A statistical analysis revealed that the expression of B7-H4 was significantly higher in the decidua in PA samples compared to samples from patients with RPT (p-value < 0.001) and healthy controls (p-value < 0.001). The expression of B7-H4 in the placental chorionic villus was significantly higher in PA samples in relation to samples from healthy controls (p-value < 0.001) but not in relation to RPT samples (p-value = 0.0853). This finding suggests that B7-H4 might play an important role in mechanisms restoring reproductive tract homeostasis. Further research is necessary in regard to the role of B7-H4 in PA.

Progesterone receptor genetic variants in pregnant women and fetuses as possible predictors of spontaneous premature birth: A preliminary case-control study

AIM

To evaluate the roles of four selected genetic variations in fetal and maternal progesterone receptor gene (PGR) and to identify women who may have higher or lower odds for spontaneous premature birth compared to the general population.

METHODS

A preliminary case-control study with two groups of pregnant women (with term and premature delivery, 218 in total) and two groups of newborns (term and preterm, 218 in total) was performed. Four single nucleotide polymorphisms (SNPs) of the progesterone receptor gene (rs1042838, rs1042839, rs10895068, and rs1942836) were genotyped.

RESULTS

There was statistically significant difference between cases and controls in the distribution of newborns' allele frequency of minor C allele of the PGR SNP rs1942836 (p = 0.03, Fishers' exact test) in favor of premature birth. A statistically significant difference between the frequency of the mothers' minor T allele of rs1042838 (p = 0.005; chi-squared test) and the mothers' minor T allele of rs1042839 (p = 0.005; chi-squared test) in favor of extremely premature birth has been found. There was a statistically significant difference between the frequency of the newborns' minor C allele of rs1942836 (p = 0.03; chi-squared test) and newborns' heterozygotes CT genotype of rs1942836 (p = 0.03; Fishers' exact test) when comparing the group of term births and the group of early premature birth.

CONCLUSION

Our study suggests that patients with selected genetic variants of the progesterone receptor gene could have greater odds for premature birth compared to term birth. Replication studies with a larger population and different ethnicity are needed in order to confirm these findings.

Protease inhibitor-based antiretroviral therapy in pregnancy: effects on hormones, placenta, and decidua

The use of antiretroviral therapy (ART) in pregnancy is important for maternal health, and has been successful in reducing vertical transmission rates to almost zero in those taking effective ART regimens with good adherence. However, there are reports of higher rates of low birthweight and preterm births in women with HIV, which can be further exacerbated by ART usage in pregnancy. Protease inhibitors, and ritonavir-boosted lopinavir in particular, might directly contribute to placental and uteroplacental pathology in part by altering plasma concentrations of the essential steroid hormones of pregnancy, progesterone and oestradiol. In this Review, we collate the increasing evidence of dysregulated maternal endocrinology, reproductive physiology, and placental compromise associated with protease inhibitors. Based on findings of placental and decidual effects, we recommend that ritonavir-boosted lopinavir should be avoided in pregnancy, in line with US and European guidelines. Long-term follow-up of children exposed to protease inhibitors in utero is also recommended.

The selective progesterone receptor modulator-promegestone-delays term parturition and prevents systemic inflammation-mediated preterm birth in mice

BACKGROUND

Progesterone, acting via its nuclear receptors called progesterone receptors, promotes myometrial relaxation during pregnancy, and suspension of this activity triggers labor. We previously found that 20α-hydroxysteroid dehydrogenase causes a local withdrawal of progesterone in the term and preterm myometrium by converting the progesterone into an inactive form before it accesses the progesterone receptors.

OBJECTIVE

We hypothesized that a selective progesterone receptor modulator called promegestone, which is not metabolized by 20α-hydroxysteroid dehydrogenase, would sustain progesterone receptor signaling and prevent/delay term labor and preterm labor in mice.

STUDY DESIGN

In the term labor mouse model, promegestone (0.2 mg/dam) or a vehicle were administered subcutaneously in timed-pregnant CD-1 mice at gestational days 15, 16, and 17 (term gestational days, 19.5). In the inflammation preterm labor model, pregnant mice received promegestone or a vehicle on gestational days 15, 16, and 17, which was 24 hours before, immediately before, and 24 hours after systemic bacterial endotoxin (50 μg intraperitoneal; lipopolysaccharide group) or vehicle (saline) administration. The maternal and fetal tissues were collected on gestational day 16 6 hours after lipopolysaccharide±promegestone injection and at term gestational day 18.75. The protein levels of 10 cytokines were measured by multiplex immunoassay in maternal plasma and amniotic fluid. Myometrial, decidual, and placental messenger RNA levels of multiple cytokines and procontractile proteins were evaluated by real-time polymerase chain reaction and confirmed by immunoblotting.

RESULTS

Promegestone prevented term labor and maintained mice pregnancy postterm >24 hours. The litter size and fetal weights were not different from the controls. Promegestone prevented systemic bacterial-endotoxin-induced preterm labor in 100% of the mice, blocked uterine contractions, significantly inhibited all systemic inflammation-induced myometrial cytokines, and partially inhibited decidual and placental inflammation. Promegestone did not prevent bacterial-endotoxin-induced fetal toxicity.

CONCLUSION

Promegestone a selective progesterone receptor modulator that binds progesterone receptors with high affinity and is not metabolized by 20α-hydroxysteroid dehydrogenase could completely suppress term parturition and systemic bacterial-endotoxin-induced preterm birth in mice. We suggest that such selective progesterone receptor modulators may represent a potential therapeutic approach to the prevention of preterm labor in women at high risk of preterm birth.

Identification of unusual oxysterols biosynthesised in human pregnancy by charge-tagging and liquid chromatography - mass spectrometry

The aim of this study was to identify oxysterols and any down-stream metabolites in placenta, umbilical cord blood plasma, maternal plasma and amniotic fluid to enhance our knowledge of the involvement of these molecules in pregnancy. We confirm the identification of 20S-hydroxycholesterol in human placenta, previously reported in a single publication, and propose a pathway from 22R-hydroxycholesterol to a C₂₇ bile acid of probable structure 3β,20R,22R-trihydroxycholest-5-en-(25R)26-oic acid. The pathway is evident not only in placenta, but pathway intermediates are also found in umbilical cord plasma, maternal plasma and amniotic fluid but not non-pregnant women.

Preterm labor is a distinct process from term labor following computational analysis of human myometrium

BACKGROUND

The onset of the term human parturition involves myometrial gene expression changes to transform the uterus from a quiescent to a contractile phenotype. It is uncertain whether the same changes occur in the uterus during preterm labor.

OBJECTIVE

This study aimed to compare the myometrial gene expression between term and preterm labor and to determine whether the presence of acute clinical chorioamnionitis or twin gestation affects these signatures.

STUDY DESIGN

Myometrial specimens were collected during cesarean delivery from the following 7 different groups of patients: term not in labor (n=31), term labor (n=13), preterm not in labor (n=21), preterm labor with acute clinical chorioamnionitis (n=6), preterm labor with no acute clinical chorioamnionitis (n=9), twin preterm not in labor (n=8), and twin preterm labor with no acute clinical chorioamnionitis (n=5). RNA was extracted, reverse transcribed and quantitative polymerase chain reactions were performed on 44 candidate genes (with evidence for differential expression in human term labor) using the Fluidigm platform. Computational analysis was performed using 2-class unpaired Wilcoxon tests and principal component analysis.

RESULTS

Computational analysis revealed that gene expression in the preterm myometrium, irrespective of whether in labor or not in labor, clustered tightly and is clearly different from the term labor and term not-in-labor groups. This was true for both singleton and twin pregnancies. Principal component analysis showed that 57% of the variation was explained by 3 principal components. These 44 genes interact in themes of prostaglandin activity and inflammatory signaling known to be important during term labor, but are not a full representation of the myometrium transcriptional activity.

CONCLUSION

The myometrial contractions associated with preterm labor are associated with a pattern of gene expression that is distinct from term labor. Therefore, preterm labor may be initiated by a different myometrial process or processes outside the myometrium.

Histone Deacetylase Inhibitors: Providing New Insights and Therapeutic Avenues for Unlocking Human Birth

The pregnant uterus remains relaxed throughout fetal gestation before transforming to a contractile phenotype at term to facilitate birth. Despite ongoing progress, the precise mechanisms that regulate this phenotypic transformation are not yet understood. This knowledge gap limits our understanding of how dysregulation of uterine smooth muscle biology contributes to life-threatening obstetric complications, including preterm birth, and hampers our ability to develop effective therapeutic intervention strategies. Protein acetylation plays a vital role in regulating protein structure, function, and subcellular localization, as well as gene transcription availability through regulating chromatin condensation. Histone deacetylase inhibitors (HDACis) are a class of compounds that block the removal of acetyl functional groups from proteins and, as such, have profound effects on important cellular events, including phenotypic transformation. A large body of data now demonstrates that HDACis have profound effects on pregnant human myometrium. Studies to date show that HDACis operate through both genomic and non-genomic mechanisms to affect myometrial function and phenotype. Interestingly, the effects of HDACis on pregnant myometrium are largely "pro-relaxation," including the direct inhibition of contractile machinery as well as repression of pro-labor genes. The "dual action" effects of HDACis make them a powerful tool for unlocking the regulatory processes that underpin myometrial phenotypic transformation and raises prospects of their therapeutic applications. Here, we review the new insights into human myometrial biology that have garnered through the application of HDACis and explore their potential therapeutic application toward the development of novel preterm birth prevention strategies.

A Peripheral Immune Signature of Labor Induction

Approximately 1 in 4 pregnant women in the United States undergo labor induction. The onset and establishment of labor, particularly induced labor, is a complex and dynamic process influenced by multiple endocrine, inflammatory, and mechanical factors as well as obstetric and pharmacological interventions. The duration from labor induction to the onset of active labor remains unpredictable. Moreover, prolonged labor is associated with severe complications for the mother and her offspring, most importantly chorioamnionitis, uterine atony, and postpartum hemorrhage. While maternal immune system adaptations that are critical for the maintenance of a healthy pregnancy have been previously characterized, the role of the immune system during the establishment of labor is poorly understood. Understanding maternal immune adaptations during labor initiation can have important ramifications for predicting successful labor induction and labor complications in both induced and spontaneous types of labor. The aim of this study was to characterize labor-associated maternal immune system dynamics from labor induction to the start of active labor. Serial blood samples from fifteen participants were collected immediately prior to labor induction (baseline) and during the latent phase until the start of active labor. Using high-dimensional mass cytometry, a total of 1,059 single-cell immune features were extracted from each sample. A multivariate machine-learning method was employed to characterize the dynamic changes of the maternal immune system after labor induction until the establishment of active labor. A cross-validated linear sparse regression model (least absolute shrinkage and selection operator, LASSO) predicted the minutes since induction of labor with high accuracy (R = 0.86, p = 6.7e-15, RMSE = 277 min). Immune features most informative for the model included STAT5 signaling in central memory CD8⁺ T cells and pro-inflammatory STAT3 signaling responses across multiple adaptive and innate immune cell subsets. Our study reports a peripheral immune signature of labor induction, and provides important insights into biological mechanisms that may ultimately predict labor induction success as well as complications, thereby facilitating clinical decision-making to improve maternal and fetal well-being.

Progesterone-induced blocking factor (PIBF) influences the expression of membrane progesterone receptors (mPRs) on peripheral CD4+ T lymphocyte cells in normal fertile females

PURPOSE

Progesterone-induced blocking factor (PIBF) is a protein secreted by lymphocytes exposed to progesterone (P4). P4 and PIBF have immunomodulatory effects on peripheral CD4⁺ T cells during normal pregnancy. Membrane progesterone receptors (mPRs) may correlate with the immunomodulatory properties of P4 on T cells. Variation in expression of mPRs may influence P4 regulatory performance during pregnancy. On the other hand, PIBF increases in pregnant normal women compared to women who have experienced abortion. The present study aimed to determine whether PIBF, in addition to having a direct influence on the immune system, can affect P4 performance through its effect on mPR expression. Such novel research findings demonstrate the importance of PIBF in the maintenance of pregnancy.

METHODS

Isolated peripheral blood mononuclear cells (PBMCs) from 30 healthy women were stimulated with the mitogen phytohemagglutinin (PHA). Cells were either exposed to various concentrations of PIBF or had no exposure at all in a culture medium at 37 °C for 3 days. The mean fluorescence intensity (MFI) of mPRα and mPRβ was evaluated using polyclonal and monoclonal antibodies on CD4⁺ T cells.

RESULTS

PIBF was able to significantly increase mPR expression on the surface of peripheral CD4⁺ T cells (p ≤ 0.05).

CONCLUSION

This study characterized the effects of PIBF on mPR expression on peripheral CD4⁺ T cells of healthy fertile women. Thus, a decrease in PIBF concentration during abnormal pregnancy can modulate mPR expression and regulatory performance of P4 on T cells. Future research into this issue is likely to open up a new understanding of the etiology of abortion.

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.

Next generation strategies for preventing preterm birth

Preterm birth (PTB) is defined as delivery before 37 weeks of gestation. Globally, 15 million infants are born prematurely, putting these children at an increased risk of mortality and lifelong health challenges. Currently in the U.S., there is only one FDA approved therapy for the prevention of preterm birth. Makena is an intramuscular progestin injection given to women who have experienced a premature delivery in the past. Recently, however, Makena failed a confirmatory trial, resulting the Center for Drug Evaluation and Research's (CDER) recommendation for the FDA to withdrawal Makena's approval. This recommendation would leave clinicians with no therapeutic options for preventing PTB. Here, we outline recent interdisciplinary efforts involving physicians, pharmacologists, biologists, chemists, and engineers to understand risk factors associated with PTB, to define mechanisms that contribute to PTB, and to develop next generation therapies for preventing PTB. These advances have the potential to better identify women at risk for PTB, prevent the onset of premature labor, and, ultimately, save infant lives.

Absorption, distribution, metabolism and excretion of hyaluronic acid during pregnancy: a matter of molecular weight

INTRODUCTION

For many years hyaluronic acid (HA) was mainly used for its hydrating properties. However, new applications have recently arisen, considering the biological properties of HA and its molecular weight. Clinical application of low molecular weight HA (LMW-HA) initially was supported by specific absorption data. The identification of high molecular weight HA (HMW-HA) absorption pathways and the knowledge of its physiological role allowed to evaluate its clinical application. Based on the immunomodulatory properties of HMW-HA and its physiological involvement as signaling molecule, pregnancy represents an interesting context of application.

AREA COVERED

This expert opinion includes in-vitro, in-vivo, ex-vivo and clinical studies on gestational models. It provides an overview of the physiological and the therapeutic role of HMW-HA in pregnancy starting from its metabolism. Indeed, HMW-HA is widely involved in several physiological processes as implantation, immune response, uterine quiescence and cervical remodeling, and therefore is an essential molecule for a successful pregnancy.

EXPERT OPINION

Available evidence suggests that HMW-HA administration can support physiological pregnancy, favoring blastocyst adhesion and development, preventing miscarriage and pre-term birth. For this reason, supplementation in pregnancy should be evaluated.

Landscape of Preterm Birth Therapeutics and a Path Forward

Preterm birth (PTB) remains the leading cause of infant morbidity and mortality. Despite 50 years of research, therapeutic options are limited and many lack clear efficacy. Tocolytic agents are drugs that briefly delay PTB, typically to allow antenatal corticosteroid administration for accelerating fetal lung maturity or to transfer patients to high-level care facilities. Globally, there is an unmet need for better tocolytic agents, particularly in low- and middle-income countries. Although most tocolytics, such as betamimetics and indomethacin, suppress downstream mediators of the parturition pathway, newer therapeutics are being designed to selectively target inflammatory checkpoints with the goal of providing broader and more effective tocolysis. However, the relatively small market for new PTB therapeutics and formidable regulatory hurdles have led to minimal pharmaceutical interest and a stagnant drug pipeline. In this review, we present the current landscape of PTB therapeutics, assessing the history of drug development, mechanisms of action, adverse effects, and the updated literature on drug efficacy. We also review the regulatory hurdles and other obstacles impairing novel tocolytic development. Ultimately, we present possible steps to expedite drug development and meet the growing need for effective preterm birth therapeutics.

Molecular Changes on Maternal-Fetal Interface in Placental Abruption-A Systematic Review

Placental abruption is the separation of the placenta from the lining of the uterus before childbirth. It is an infrequent perinatal complication with serious after-effects and a marked risk of maternal and fetal mortality. Despite the fact that numerous placental abruption risk factors are known, the pathophysiology of this issue is multifactorial and not entirely clear. The aim of this review was to examine the current state of knowledge concerning the molecular changes on the maternal–fetal interface occurring in placental abruption. Only original research articles describing studies published in English until the 15 March 2021 were considered eligible. Reviews, book chapters, case studies, conference papers and opinions were excluded. The systematic literature search of PubMed/MEDLINE and Scopus databases identified 708 articles, 22 of which were analyzed. The available evidence indicates that the disruption of the immunological processes on the maternal–fetal interface plays a crucial role in the pathophysiology of placental abruption. The features of chronic non-infectious inflammation and augmented immunological cytotoxic response were found to be present in placental abruption samples in the reviewed studies. Various molecules participate in this process, with only a few being examined. More advanced research is needed to fully explain this complicated process.