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

Role of Platelet Activating Factor as a Mediator of Inflammatory Diseases and Preterm Delivery

Nearly 70% of preterm deliveries occur spontaneously, and the clinical pathways involved include preterm labor and preterm premature rupture of membranes. Prediction of preterm delivery is considered crucial due to the significant effects of preterm birth on health and the economy at both the personal and community levels. Although similar inflammatory processes occur in both term and preterm delivery, the premature activation of these processes or exaggerated inflammatory response triggered by infection or sterile factors leads to preterm delivery. Platelet activating factor (PAF) is a phosphoglycerylether lipid mediator of inflammation that is implicated in infections, cancers, and various chronic diseases and disorders including cardiovascular, renal, cerebrovascular, and central nervous system diseases. In gestational tissues, PAF mediates the inflammatory pathways that stimulate the effector mechanisms of labor, including myometrial contraction, cervical dilation, and fetal membrane rupture. Women with preterm labor and preterm premature rupture of membranes have increased levels of PAF in their amniotic fluid. In mice, the intrauterine or intraperitoneal administration of carbamyl PAF activates inflammation in gestational tissues, thereby eliciting preterm delivery. This review summarizes recent research on PAF as an important inflammatory mediator in preterm delivery and in other inflammatory disorders, highlighting its potential value for prediction, intervention, and prevention of these diseases.

New approach methods on the bench side to accelerate clinical trials during pregnancy

INTRODUCTION

Pregnant women are therapeutic orphans as they are excluded from clinical drug development and therapeutic trials. We identify limitations in conducting clinical trials and propose two 'New Approach Methods'(NAMs) to overcome them.

AREAS COVERED

NAMs have proven invaluable tools in basic and clinical research to understand human health and disease better, elucidate mechanisms, and study the efficacy and toxicity of therapeutics that have not been possible through animal-based methodologies. The lack of humanized experimental models of FMi and drugs that can safely and effectively cross FMi to reduce the risk of adverse pregnancy has hindered progress in the field of reproductive pharmacology. This report discusses two technological advancements in perinatal research and medicine to accelerate clinical trials during pregnancy. (1) We have developed a humanized microphysiologic system, an Organ-on-a-chip (OOC) platform, to study FMi and their utility in pharmacological studies, and (2) use of extracellular vesicles (EVs) as drug delivery vehicles that are immunologically inert and can cross the fetomaternal barriers.

EXPERT OPINION

We provide an overview of NAMs that can accelerate preclinical trials and develop drugs to cross the feto-maternal barriers to reduce the risk of adverse pregnancy outcomes like preterm birth.

Phenanthroline relaxes uterine contractions induced by diverse contractile agents by decreasing cytosolic calcium concentration

Uterine contractions during labor and preterm labor are influenced by a complex interplay of factors, including hormones and inflammatory mediators. This complexity may contribute to the limited efficacy of current tocolytics for preterm labor, a significant challenge in obstetrics with 15 million cases annually and approximately 1 million resulting deaths worldwide. We have previously shown that the myometrium expresses bitter taste receptors (TAS2Rs) and that their activation leads to uterine relaxation. Here, we investigated whether the selective TAS2R5 agonist phenanthroline can induce relaxation across a spectrum of human uterine contractions and whether the underlying mechanism involves changes in intracellular Ca2+ signaling. We performed experiments using samples from pregnant women undergoing scheduled cesarean delivery, assessing responses to various inflammatory mediators and oxytocin with and without phenanthroline. Our results showed that phenanthroline concentration-dependently inhibited contractions induced by PGF2α, U46619, 5-HT, endothelin-1 and oxytocin. Furthermore, in hTERT-infected human myometrial cells exposed to uterotonics, phenanthroline effectively suppressed the increase in intracellular Ca2+ concentration induced by PGF2α, U46619, oxytocin, and endothelin-1. These results suggest that the selective TAS2R5 agonist may not only significantly reduce uterine contractions but also decrease intracellular Ca2+ levels. This study highlights the potential development of TAS2R5 agonists as a new class of uterine relaxants, providing a novel avenue for improving the management of preterm labor.

Are fetal microchimerism and circulating fetal extracellular vesicles important links between spontaneous preterm delivery and maternal cardiovascular disease risk?

Trafficking and persistence of fetal microchimeric cells (fMCs) and circulating extracellular vesicles (EVs) have been observed in animals and humans, but their consequences in the maternal body and their mechanistic contributions to maternal physiology and pathophysiology are not yet fully defined. Fetal cells and EVs may help remodel maternal organs after pregnancy-associated changes, but the cell types and EV cargos reaching the mother in preterm pregnancies after exposure to various risk factors can be distinct from term pregnancies. As preterm delivery-associated maternal complications are rising, revisiting this topic and formulating scientific questions for future research to reduce the risk of maternal morbidities are timely. Epidemiological studies report maternal cardiovascular risk as one of the major complications after preterm delivery. This paper suggests a potential link between fMCs and circulating EVs and adverse maternal cardiovascular outcomes post-pregnancies, the underlying mechanisms, consequences, and methods for and how this link might be assessed.

Endocrine-disrupting compounds and their impact on human placental function: evidence from placenta organ-on-chip studies

The effects of endocrine-disrupting compounds (EDCs) on the placenta, a critical gestational organ for xenobiotic protection, are well reported; however, models to determine the role of EDCs in placental disruption are limited. An advanced 2nd-trimester human placenta organ-on-chip model (2TPLA-OOC) was developed and validated, with six representative cells of the maternal and the fetal interface interconnected with microchannels. Various EDCs (150 ng mL-1 each of bisphenol A, bisphenol S, and polybrominated diphenyl ethers-47 and -99) were gradually propagated across the chip for 72 hours, and their various effects were determined. Cigarette smoke extract (CSE), an environmental risk factor, was used as a positive control. EDCs produced overall oxidative stress in the placental/decidual cells, induced cell-specific endocrine effects, caused limited (<10%) apoptosis/necrosis in trophoblasts and mesenchymal cells, induced localized inflammation but an overall anti-inflammatory shift, did not change immune cell migration from stroma to decidua, and did not affect placental nutrient transport. Overall, (1) the humanized 2TPLA-OOC recreated the placental organ and generated data distinct from the trophoblast and other cells studied in isolation, and (2) at doses associated with adverse pregnancies, EDCs produced limited and localized insults, and the whole organ compensated for the exposure.

Gestational age at birth in pregnancies with antenatal corticosteroid administration in relation to risk factors: a retrospective cohort study

Background

The aim was to investigate gestational age at birth of women after induction of fetal lung maturation (antenatal corticosteroids = ACS) because of imminent preterm birth (PTB), and to quantify incidence of late PTB (gestational age < 260 days) and extreme immaturity (gestational age < 196 days) in relation to several diagnoses (PPROM, placental bleeding, premature labor, preeclampsia, oligohydramnios, amniotic infection syndrome (AIS), cervical insufficiency) and risk factors (age > 35, history of preterm delivery, multifetal gestation, gestational diabetes, hypertension, nicotine abuse).

Methods

The study was designed as a retrospective cohort trial, in which the data of all births taking place in 2016 in the German federal state Rhineland-Palatinate were evaluated. Frequency analyses, subgroup analysis (Chi-square tests and Friedman's tests), as well as multinomial logistic regressions and linear regressions were used to determine odds ratios (OR).

Results

In total, N = 1,544 patients were included who had been hospitalized due to an imminent PTB and had received ACS, of whom 52% had a late PTB and 8% a PTB with extreme immaturity. Regarding the gestational age at birth, there were only minor differences between the individual risk factors and diagnoses, only AIS patients showed a significantly lower gestational age (mean: 207 days). A significantly increased risk of PTB with extreme immaturity was found in patients with AIS (OR = 5.57) or placental bleeding (OR = 2.10).

Conclusion

There is a need for further research in order to be able to apply therapeutic measures more accurately in relation to risk factors and diagnoses.

A genome-wide and candidate gene association study of preterm birth in Korean pregnant women

Preterm birth (PTB) refers to delivery before 37 weeks of gestation. Premature neonates exhibit higher neonatal morbidity and mortality rates than term neonates; therefore, it is crucial to predict and prevent PTB. Advancements enable the prediction and prevention of PTB using genetic approaches, especially by investigating its correlation with single nucleotide polymorphisms (SNPs). We aimed to identify impactive and relevant SNPs for the prediction of PTB via whole-genome sequencing analyses of the blood of 31 pregnant women with PTB (n = 13) and term birth (n = 18) who visited the Ewha Womans University Mokdong Hospital from November 1, 2018 to February 29, 2020. A genome-wide association study was performed using PLINK 1.9 software and 256 SNPs were selected and traced through protein-protein interactions. Moreover, a validation study by genotyping was performed on 60 other participants (preterm birth, n = 30; term birth, n = 30) for 25 SNPs related to ion channel binding and receptor complex pathways. Odds ratios were calculated using additive, dominant, and recessive genetic models. The risk of PTB in women with the AG allele of rs2485579 (gene name: RYR2) was significantly 4.82-fold increase, and the risk of PTB in women with the AG allele of rs7903957 (gene name: TBX5) was significantly 0.25-fold reduce. Our results suggest that rs2485579 (in RYR2) can be a genetic marker of PTB, which is considered through the association with abnormal cytoplasmic Ca2+ concentration and dysfunctional uterine contraction due to differences of RYR2 in the sarcoplasmic reticulum.

Association between interleukin-6 and preterm birth: a meta-analysis

BACKGROUND

Interleukin (IL)-6 is a pro-inflammatory cytokine that plays an important role in preterm birth (PTB), Several meta-analyses investigated the association between IL-6 and PTB, but definitive conclusion has not yet been achieved. This updated meta-analysis aimed to ascertain the association between IL-6 and PTB by examining IL-6 levels in both normal birth and PTB groups.

MATERIAL AND METHODS

Prospective cohort studies were retrieved in PubMed, Embase, and the Cochrane library from their inception until 18 February 2020. The primary outcome was the association between IL-6 and PTB, and secondary outcomes were the association between IL-6 and spontaneous PTB.

RESULTS

Nine studies involving 1904 patients were included. Overall, IL-6 from different sample types (maternal blood, amniotic fluid and cervicovaginal fluid) was associated with PTB (standard mean difference [SMD]: 0.86, 95% confidence interval [CI]: 0.32 to 1.39, p < 0.001). Furthermore, the association was significant for IL-6 only in amniotic fluid (SMD: 1.87, 95%CI: 0.82 to 2.93, p < 0.001) and cervicovaginal fluid (SMD: 0.46, 95%CI: 0.09 to 0.84, p = 0.022), but not significant in maternal blood (SMD: -0.11, 95%CI: -0.57 to 0.34, p = 0.623). In addition, IL-6 was also associated with spontaneous PTB (SMD: 1.57, 95% CI: 0.18 to 2.95, p < 0.001).

CONCLUSIONS

Based on the available evidence, IL-6 in amniotic fluid and cervicovaginal fluid might be useful for predicting preterm birth.

Intrauterine growth restriction, prematurity, and low birth weight: risk phenotypes of neonatal death, Rio de Janeiro State, Brazil

Intrauterine growth restriction and prematurity determine low birth weight. The combination of the three conditions results in different neonatal phenotypes that interfere with child survival. Neonatal prevalence, survival and mortality were estimated according to neonatal phenotypes in the cohort of live births in 2021 in the state of Rio de Janeiro, Brazil. In this study, live births of multiple pregnancies, with congenital anomalies and inconsistencies in the information of weight and gestational age were excluded. The Intergrowth curve was used to classify weight adequacy. Mortality (< 24 hours, 1-6 and 7-27 days) and survival (Kaplan-Meier) were estimated. In total, 6.8%, 5.5%, and 9.5% of the 174,399 live births were low birth weight, small for gestational age (SGA), and premature, respectively. Considering low birth weight live births, 39.7% were SGA and 70% were premature. The neonatal phenotypes were heterogeneous according to maternal, delivery, pregnancy, and newborn characteristics. The mortality rate per 1,000 live births was high for low birth weight premature newborns, both SGA (78.1) and AGA (adequate for gestational age: 61.1), at all specific ages. Reductions in the survival rate were observed when comparing non-low birth weight and AGA term live births. The estimated prevalence values were lower than those of other studies, partly due to the exclusion criteria adopted. The neonatal phenotypes identified children who were more vulnerable and at higher risk of death. Prematurity contributed more to mortality than SGA, and its prevention is necessary to reduce neonatal mortality in the state of Rio de Janeiro.

Barriers to progress in pregnancy research: How can we break through?

Healthy pregnancies are fundamental to healthy populations, but very few therapies to improve pregnancy outcomes are available. Fundamental concepts-for example, placentation or the mechanisms that control the onset of labor-remain understudied and incompletely understood. A key issue is that research efforts must capture the complexity of the tripartite maternal-placental-fetal system, the dynamics of which change throughout gestation. Studying pregnancy disorders is complicated by the difficulty of creating maternal-placental-fetal interfaces in vitro and the uncertain relevance of animal models to human pregnancy. However, newer approaches include trophoblast organoids to model the developing placenta and integrated data-science approaches to study longer-term outcomes. These approaches provide insights into the physiology of healthy pregnancy, which is the first step to identifying therapeutic targets in pregnancy disorders.