Developing a theoretical evolutionary framework to solve the mystery of parturition initiation

KDM6B-dependent epigenetic programming of uterine fibroblasts in early pregnancy regulates parturition timing in mice

Current efforts investigating parturition timing mechanisms have focused on the proximal triggers of labor onset generated in late pregnancy. By studying the delayed parturition phenotype of mice with uterine fibroblast deficiencies in the histone H3K27me3 demethylase KDM6B, we provide evidence that parturition timing is regulated by events that take place in early pregnancy. Immediately after copulation, uterine fibroblasts engage in a locus-specific epigenetic program that abruptly adjusts H3K27me3 levels across their genome. In the absence of KDM6B, many of the adjusted loci over-accumulate H3K27me3. This over-accumulation leads to nearby genes being misexpressed in mid-to-late gestation, a delayed effect partly attributable to a second locus-specific but KDM6B-independent process initiated within uterine fibroblasts soon after implantation. This second process employs progressive H3K27me3 loss to temporally structure post-midgestational patterns of gene induction. Further dissection of the ways uterine programming controls parturition timing may have relevance to human pregnancy complications such as preterm labor.

Progesterone regulation of cervix ripening in preterm and term birth

The cervix functions both as gatekeeper barrier to maintain pregnancy and virtually vanish for birth at term in mammals. The period of remodeling well-before term is characterized by an inflammatory process associated with reduced cell nuclei density and cross-linked collagen, as well as increased density of resident macrophages in cervix stroma. Contemporarily, progesterone (P4) is at or near peak concentrations in maternal circulation. The functional or actual loss of response to P4 is thought to drive the process that enhances uterine contractile activity for labor and parturition at term. The objective of the present study was to determine if actual or functional loss of P4 regulated cytomorphological characteristics associated with prepartum cervix ripening at term and with preterm birth. On day 16 of pregnancy. Ovaries were removed to eliminate the main source of P4 production and a silastic capsule implanted (with vehicle or P4, Ovx or Ovx+P4, respectively). Controls received a vehicle-filled capsule, while a P4 capsule was implanted into an addition group of Intact mice to ensure sustained concentrations throughout pregnancy (Intact+P4). Pups were born in controls at term (days 19-20 postbreeding), but deliveries were preterm in Ovx mice within 24h (day 17). In the Ovx+P4 group, births were delayed to term and post-term in most Intact+P4 mice with adverse pregnancy outcomes commonplace. Characteristics of cell nuclei and degradation of cross-linked collagen were advanced with preterm birth in Ovx mice compared to controls that gave birth by at term. Treatment of Ovx mice with P4 blocked preterm birth, but parturition was complicated by dystocia. In addition, P4 given to ovary-intact mice sustained peak pregnancy concentrations, but had minimal effects on cytoarchitecture of the prepartum cervix stroma except term birth was forestalled with dystocia and fetal morbidity. Density of resident macrophages in the cervix stroma in term Ovx+P4 mice was reduced along with area of macrophage stain versus postpartum controls. Thus, analyses of cervix cellular cytoarchitecture provided useful biomarkers of local inflammation to assessment the ripening process for preterm and term parturition. Collectively, findings suggest a functional loss of prepartum cervix responses to progesterone are part of a final common mechanism for parturition across mammals.

Summary

Loss of response to progesterone withdrawal is associated with cervix ripening while some cytoarchitectural characteristics of remodeling are regulated to block preterm birth and dystocia at term.

Adiponectin and Glucocorticoids Modulate Risk for Preterm Birth: The Healthy Start Study

CONTEXT

Adiponectin is a potent uterine tocolytic that decreases with gestational age, suggesting it could be a maternal metabolic quiescence factor. Maternal stress can influence preterm birth risk, and adiponectin levels may be stress responsive.

OBJECTIVE

We characterized associations between adiponectin and glucocorticoids with preterm birth and modeled their predictive utility. We hypothesized maternal plasma adiponectin and cortisol are inversely related and lower adiponectin and higher cortisol associate with preterm birth.

METHODS

We performed a nested case-control study using biobanked fasting maternal plasma. We included low-risk singleton pregnancies, and matched 1:3 (16 preterm, 46 term). We quantified high molecular weight (HMW), low molecular weight (LMW), and total adiponectin using an enzyme-linked immunosorbent assay. We validated a high-performance liquid chromatography-tandem mass spectrometry serum assay for use in plasma, to simultaneously measure cortisol, cortisone, and 5 related steroid hormones. We used linear/logistic regression to compare group means and machine learning for predictive modeling.

RESULTS

The preterm group had lower mean LMW adiponectin (3.07 μg/mL vs 3.81 μg/mL at 15 weeks (w) 0 days (d), P = .045) and higher mean cortisone (34.4 ng/mL vs 29.0 ng/mL at 15w0d, P = .031). The preterm group had lower cortisol to cortisone and lower LMW adiponectin to cortisol ratios. We found HMW adiponectin, cortisol to cortisone ratio, cortisone, maternal height, age, and prepregnancy body mass index most strongly predicted preterm birth (area under the receiver operator curve = 0.8167). In secondary analyses, we assessed biomarker associations with maternal self-reported psychosocial stress. Lower perceived stress was associated with a steeper change in cortisone in the term group.

CONCLUSION

Overall, metabolic and stress biomarkers are associated with preterm birth in this healthy cohort. We identify a possible mechanistic link between maternal stress and metabolism for pregnancy maintenance.

Perspective on using non-human primates in Exposome research

The physiological and pathological changes in the human body caused by environmental pressures are collectively referred to as the Exposome. Human society is facing escalating environmental pollution, leading to a rising prevalence of associated diseases, including respiratory diseases, cardiovascular diseases, neurological disorders, reproductive development disorders, among others. Vulnerable populations to the pathogenic effects of environmental pollution include those in the prenatal, infancy, and elderly stages of life. Conducting Exposome mechanistic research and proposing effective health interventions are urgent in addressing the current severe environmental pollution. In this review, we address the core issues and bottlenecks faced by current Exposome research, specifically focusing on the most toxic ultrafine nanoparticles. We summarize multiple research models being used in Exposome research. Especially, we discuss the limitations of rodent animal models in mimicking human physiopathological phenotypes, and prospect advantages and necessity of non-human primates in Exposome research based on their evolutionary relatedness, anatomical and physiological similarities to human. Finally, we declare the initiation of NHPE (Non-Human Primate Exposome) project for conducting Exposome research using non-human primates and provide insights into its feasibility and key areas of focus. SYNOPSIS: Non-human primate models hold unique advantages in human Exposome research.

Review on new approach methods to gain insight into the feto-maternal interface physiology

Non-human animals represent a large and important feature in the history of biomedical research. The validity of their use, in terms of reproducible outcomes and translational confidence to the human situation, as well as ethical concerns surrounding that use, have been and remain controversial topics. Over the last 10 years, the communities developing microphysiological systems (MPS) have produced new approach method (NAMs) such as organoids and organs-on-a-chip. These alternative methodologies have shown indications of greater reliability and translatability than animal use in some areas, represent more humane substitutions for animals in these settings, and - with continued scientific effort - may change the conduct of basic research, clinical studies, safety testing, and drug development. Here, we present an introduction to these more human-relevant methodologies and suggest how a suite of pregnancy associated feto-maternal interface system-oriented NAMs may be integrated as reliable partial-/full animal replacements for investigators, significantly aid animal-/environmental welfare, and improve healthcare outcomes.

Lab partners: oocytes, embryos and company. A personal view on aspects of oocyte maturation and the development of monozygotic twins

The present review addresses the oocyte and the preimplantation embryo, and is intended to highlight the underlying principle of the "nature versus/and nurture" question. Given the diversity in mammalian oocyte maturation, this review will not be comprehensive but instead will focus on the porcine oocyte. Historically, oogenesis was seen as the development of a passive cell nursed and determined by its somatic compartment. Currently, the advanced analysis of the cross-talk between the maternal environment and the oocyte shows a more balanced relationship: Granulosa cells nurse the oocyte, whereas the latter secretes diffusible factors that regulate proliferation and differentiation of the granulosa cells. Signal molecules of the granulosa cells either prevent the precocious initiation of meiotic maturation or enable oocyte maturation following hormonal stimulation. A similar question emerges in research on monozygotic twins or multiples: In Greek and medieval times, twins were not seen as the result of the common course of nature but were classified as faults. This seems still valid today for the rare and until now mainly unknown genesis of facultative monozygotic twins in mammals. Monozygotic twins are unique subjects for studies of the conceptus-maternal dialogue, the intra-pair similarity and dissimilarity, and the elucidation of the interplay between nature and nurture. In the course of in vivo collections of preimplantation sheep embryos and experiments on embryo splitting and other microsurgical interventions we recorded observations on double blastocysts within a single zona pellucida, double inner cell masses in zona-enclosed blastocysts and double germinal discs in elongating embryos. On the basis of these observations we add some pieces to the puzzle of the post-zygotic genesis of monozygotic twins and on maternal influences on the developing conceptus.

Time-varying effects are common in genetic control of gestational duration

Preterm birth is a major burden to neonatal health worldwide, determined in part by genetics. Recently, studies discovered several genes associated with this trait or its continuous equivalent-gestational duration. However, their effect timing, and thus clinical importance, is still unclear. Here, we use genotyping data of 31 000 births from the Norwegian Mother, Father and Child cohort (MoBa) to investigate different models of the genetic pregnancy 'clock'. We conduct genome-wide association studies using gestational duration or preterm birth, replicating known maternal associations and finding one new fetal variant. We illustrate how the interpretation of these results is complicated by the loss of power when dichotomizing. Using flexible survival models, we resolve this complexity and find that many of the known loci have time-varying effects, often stronger early in pregnancy. The overall polygenic control of birth timing appears to be shared in the term and preterm, but not very preterm, periods and exploratory results suggest involvement of the major histocompatibility complex genes in the latter. These findings show that the known gestational duration loci are clinically relevant and should help design further experimental studies.

Genetic effects on the timing of parturition and links to fetal birth weight

The timing of parturition is crucial for neonatal survival and infant health. Yet, its genetic basis remains largely unresolved. We present a maternal genome-wide meta-analysis of gestational duration (n = 195,555), identifying 22 associated loci (24 independent variants) and an enrichment in genes differentially expressed during labor. A meta-analysis of preterm delivery (18,797 cases, 260,246 controls) revealed six associated loci and large genetic similarities with gestational duration. Analysis of the parental transmitted and nontransmitted alleles (n = 136,833) shows that 15 of the gestational duration genetic variants act through the maternal genome, whereas 7 act both through the maternal and fetal genomes and 2 act only via the fetal genome. Finally, the maternal effects on gestational duration show signs of antagonistic pleiotropy with the fetal effects on birth weight: maternal alleles that increase gestational duration have negative fetal effects on birth weight. The present study provides insights into the genetic effects on the timing of parturition and the complex maternal-fetal relationship between gestational duration and birth weight.

Circumvention of luteolysis reveals parturition pathways in mice dependent upon innate type 2 immunity

Although mice normally enter labor when their ovaries stop producing progesterone (luteolysis), parturition can also be triggered in this species through uterus-intrinsic pathways potentially analogous to the ones that trigger parturition in humans. Such pathways, however, remain largely undefined in both species. Here, we report that mice deficient in innate type 2 immunity experienced profound parturition delays when manipulated endocrinologically to circumvent luteolysis, thus obliging them to enter labor through uterus-intrinsic pathways. We found that these pathways were in part driven by the alarmin IL-33 produced by uterine interstitial fibroblasts. We also implicated important roles for uterine group 2 innate lymphoid cells, which demonstrated IL-33-dependent activation prior to labor onset, and eosinophils, which displayed evidence of elevated turnover in the prepartum uterus. These findings reveal a role for innate type 2 immunity in controlling the timing of labor onset through a cascade potentially relevant to human parturition.

IL-33 is alarmin the uterus for labor

Timely labor is critical for both infant and maternal health, yet the mechanisms underlying the initiation of childbirth remain unclear. In this issue of Immunity, Siewiera et al. demonstrate a vital role for innate type 2 immune responses in controlling uterus-intrinsic onset of labor in mice.¹.

Time-varying effects are common in genetic control of gestational duration

Preterm birth is a major burden to neonatal health worldwide, determined in part by genetics. Recently, studies discovered several genes associated with this trait or its continuous equivalent - gestational duration. However, their effect timing, and thus clinical importance, is still unclear. Here, we use genotyping data of 31,000 births from the Norwegian Mother, Father and Child cohort (MoBa) to investigate different models of the genetic pregnancy "clock". We conduct genome-wide association studies using gestational duration or preterm birth, replicating known maternal associations and finding one new foetal variant. We illustrate how the interpretation of these results is complicated by the loss of power when dichotomizing. Using flexible survival models, we resolve this complexity and find that many of the known loci have time-varying effects, often stronger early in pregnancy. The overall polygenic control of birth timing appears to be shared in the term and preterm, but not very preterm periods, and exploratory results suggest involvement of the major histocompatibility complex genes in the latter. These findings show that the known gestational duration loci are clinically relevant, and should help design further experimental studies.

Childbirth fear in the USA during the COVID-19 pandemic: key predictors and associated birth outcomes

Background and objectives

Childbirth fear, which has been argued to have an adaptive basis, exists on a spectrum. Pathologically high levels of childbirth fear is a clinical condition called tokophobia. As a chronic stressor in pregnancy, tokophobia could impact birth outcomes. Many factors associated with tokophobia, including inadequate labor support, were exacerbated by the COVID-19 pandemic.

Methodology

We used longitudinally collected data from a convenience sample of 1775 pregnant persons in the USA to evaluate the association between general and COVID-19 pandemic-related factors and tokophobia using the fear of birth scale. We also assessed associations between tokophobia, low birth weight and preterm birth when adjusting for cesarean section and other covariates among a subset of participants (N = 993).

Results

Tokophobia was highly prevalent (62%). Mothers who self-identified as Black (odds ratio (OR) = 1.90), had lower income (OR = 1.39), had less education (OR = 1.37), had a high-risk pregnancy (OR = 1.65) or had prenatal depression (OR = 4.95) had significantly higher odds of tokophobia. Concerns about how COVID-19 could negatively affect maternal and infant health and birth experience were also associated with tokophobia (ORs from 1.51 to 1.79). Tokophobia was significantly associated with increased odds of giving birth preterm (OR = 1.93).

Conclusions and implications

Tokophobia increases the odds of preterm birth and is more prevalent among individuals who are Black, have a lower income, and have less education. Tokophobia may, therefore, be an underappreciated contributor to inequities in US birth outcomes. The COVID-19 pandemic likely compounded these effects.

A Nested Case-Control Study of Allopregnanolone and Preterm Birth in the Healthy Start Cohort

Context

Chronic stress is a risk factor for preterm birth; however, objective measures of stress in pregnancy are limited. Maternal stress biomarkers may fill this gap. Steroid hormones and neurosteroids such as allopregnanolone (ALLO) play important roles in stress physiology and pregnancy maintenance and therefore may be promising for preterm birth prediction.

Objective

We evaluated maternal serum ALLO, progesterone, cortisol, cortisone, pregnanolone, and epipregnanolone twice in gestation to evaluate associations with preterm birth.

Methods

We performed a nested case-control study using biobanked fasting serum samples from the Healthy Start prebirth cohort. We included healthy women with a singleton pregnancy and matched preterm cases with term controls (1:1; N = 27 per group). We used a new HPLC-tandem mass spectrometry assay to quantify ALLO and five related steroids. We used ANOVA, Fisher exact, χ², t test, and linear and logistic regression as statistical tests.

Results

Maternal serum ALLO did not associate with preterm birth nor differ between groups. Mean cortisol levels were significantly higher in the preterm group early in pregnancy (13w0d-18w0d; P < 0.05) and higher early pregnancy cortisol associated with increased odds of preterm birth (at 13w0d; odds ratio, 1.007; 95% CI, 1.0002-1.014). Progesterone, cortisone, pregnanolone, and epipregnanolone did not associate with preterm birth.

Conclusion

The findings from our pilot study suggest potential utility of cortisol as a maternal serum biomarker for preterm birth risk assessment in early pregnancy. Further evaluation using larger cohorts and additional gestational timepoints for ALLO and the other analytes may be informative.

Epithelial to mesenchymal transition (EMT) of feto-maternal reproductive tissues generates inflammation: a detrimental factor for preterm birth

Human pregnancy is a delicate and complex process where multiorgan interactions between two independent systems, the mother, and her fetus, maintain pregnancy. Intercellular interactions that can define homeostasis at the various cellular level between the two systems allow uninterrupted fetal growth and development until delivery. Interactions are needed for tissue remodeling during pregnancy at both fetal and maternal tissue layers. One of the mechanisms that help tissue remodeling is via cellular transitions where epithelial cells undergo a cyclic transition from epithelial to mesenchymal (EMT) and back from mesenchymal to epithelial (MET). Two major pregnancy-associated tissue systems that use EMT, and MET are the fetal membrane (amniochorion) amnion epithelial layer and cervical epithelial cells and will be reviewed here. EMT is often associated with localized inflammation, and it is a well-balanced process to facilitate tissue remodeling. Cyclic transition processes are important because a terminal state or the static state of EMT can cause accumulation of proinflammatory mesenchymal cells in the matrix regions of these tissues and increase localized inflammation that can cause tissue damage. Interactions that determine homeostasis are often controlled by both endocrine and paracrine mediators. Pregnancy maintenance hormone progesterone and its receptors are critical for maintaining the balance between EMT and MET. Increased intrauterine oxidative stress at term can force a static (terminal) EMT and increase inflammation that are physiologic processes that destabilize homeostasis that maintain pregnancy to promote labor and delivery of the fetus. However, conditions that can produce an untimely increase in EMT and inflammation can be pathologic. These tissue damages are often associated with adverse pregnancy complications such as preterm prelabor rupture of the membranes (pPROM) and spontaneous preterm birth (PTB). Therefore, an understanding of the biomolecular processes that maintain cyclic EMT-MET is critical to reducing the risk of pPROM and PTB. Extracellular vesicles (exosomes of 40-160 nm) that can carry various cargo are involved in cellular transitions as paracrine mediators. Exosomes can carry a variety of biomolecules as cargo. Studies specifically using exosomes from cells undergone EMT can carry a pro-inflammatory cargo and in a paracrine fashion can modify the neighboring tissue environment to cause enhancement of uterine inflammation.

Fetal inflammatory response at the fetomaternal interface: A requirement for labor at term and preterm

Human parturition at term and preterm is an inflammatory process synchronously executed by both fetomaternal tissues to transition them from a quiescent state t an active state of labor to ensure delivery. The initiators of the inflammatory signaling mechanism can be both maternal and fetal. The placental (fetal)-maternal immune and endocrine mediated homeostatic imbalances and inflammation are well reported. However, the fetal inflammatory response (FIR) theories initiated by the fetal membranes (amniochorion) at the choriodecidual interface are not well established. Although immune cell migration, activation, and production of proparturition cytokines to the fetal membranes are reported, cellular level events that can generate a unique set of inflammation are not well discussed. This review discusses derangements to fetal membrane cells (physiologically and pathologically at term and preterm, respectively) in response to both endogenous and exogenous factors to generate inflammatory signals. In addition, the mechanisms of inflammatory signal propagation (fetal signaling of parturition) and how these signals cause immune imbalances at the choriodecidual interface are discussed. In addition to maternal inflammation, this review projects FIR as an additional mediator of inflammatory overload required to promote parturition.

Abnormal respiratory progenitors in fibrotic lung injury

Recent advances in single-cell RNA sequencing (scRNA-seq) and epithelium lineage labeling have yielded identification of multiple abnormal epithelial progenitor populations during alveolar type 2 (ATII) cell differentiation into alveolar type 1 (ATI) cells during regenerative lung post-fibrotic injury. These abnormal cells include basaloid/basal-like cells, ATII transition cells, and persistent epithelial progenitors (PEPs). These cells occurred and accumulated during the regeneration of distal airway and alveoli in response to both chronic and acute pulmonary injury. Among the alveolar epithelial progenitors, PEPs express a distinct Krt8+ phenotype that is rarely found in intact alveoli. However, post-injury, the Krt8+ phenotype is seen in dysplastic epithelial cells. Fully understanding the characteristics and functions of these newly found, injury-induced abnormal behavioral epithelial progenitors and the signaling pathways regulating their phenotype could potentially point the way to unique therapeutic targets for fibrosing lung diseases. This review summarizes recent advances in understanding these epithelial progenitors as they relate to uncovering regenerative mechanisms.

Evolutionary transcriptomics implicates new genes and pathways in human pregnancy and adverse pregnancy outcomes

Evolutionary changes in the anatomy and physiology of the female reproductive system underlie the origins and diversification of pregnancy in Eutherian ('placental') mammals. This developmental and evolutionary history constrains normal physiological functions and biases the ways in which dysfunction contributes to reproductive trait diseases and adverse pregnancy outcomes. Here, we show that gene expression changes in the human endometrium during pregnancy are associated with the evolution of human-specific traits and pathologies of pregnancy. We found that hundreds of genes gained or lost endometrial expression in the human lineage. Among these are genes that may contribute to human-specific maternal-fetal communication (HTR2B) and maternal-fetal immunotolerance (PDCD1LG2) systems, as well as vascular remodeling and deep placental invasion (CORIN). These data suggest that explicit evolutionary studies of anatomical systems complement traditional methods for characterizing the genetic architecture of disease. We also anticipate our results will advance the emerging synthesis of evolution and medicine ('evolutionary medicine') and be a starting point for more sophisticated studies of the maternal-fetal interface. Furthermore, the gene expression changes we identified may contribute to the development of diagnostics and interventions for adverse pregnancy outcomes.