Epigenetics and the placenta

The one-carbon metabolism as an underlying pathway for placental DNA methylation - a systematic review

Epigenetic modifications, including DNA methylation, are proposed mechanisms explaining the impact of parental exposures to foetal development and lifelong health. Micronutrients including folate, choline, and vitamin B12 provide methyl groups for the one-carbon metabolism and subsequent DNA methylation processes. Placental DNA methylation changes in response to one-carbon moieties hold potential targets to improve obstetrical care. We conducted a systematic review on the associations between one-carbon metabolism and human placental DNA methylation. We included 22 studies. Findings from clinical studies with minimal ErasmusAGE quality score 5/10 (n = 15) and in vitro studies (n = 3) are summarized for different one-carbon moieties. Next, results are discussed per study approach: (1) global DNA methylation (n = 9), (2) genome-wide analyses (n = 4), and (3) gene specific (n = 14). Generally, one-carbon moieties were not associated with global methylation, although conflicting outcomes were reported specifically for choline. Using genome-wide approaches, few differentially methylated sites associated with S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), or dietary patterns. Most studies taking a gene-specific approach indicated site-specific relationships depending on studied moiety and genomic region, specifically in genes involved in growth and development including LEP, NR3C1, CRH, and PlGF; however, overlap between studies was low. Therefore, we recommend to further investigate the impact of an optimized one-carbon metabolism on DNA methylation and lifelong health.

A follow up investigation of placental pathology, responsive parenting, and preschool children's executive functioning and language development

Despite documented effects linking underlying placental diseases and neurological impairments in children, little is known about the long-term effects of placental pathology on children's neurocognitive outcomes. In addition, maternal responsivity, known to positively influence early postnatal cognitive development, may act to protect children from putative adverse effects of placental pathology. The current study is a follow up of medically healthy, term born, preschool age children, born with placental pathology. A sample of 118 children (45 comparison children with normal placental findings, 73 born with placental pathology) were followed when children were 3-4 years old. In comparison to children born to mothers with normal placentas, placental pathology was associated with poorer performance in the executive function involving cognitive flexibility, but not inhibitory control or receptive language. Maternal responsivity was observed to be marginally protective on the impact of placental pathology risk on cognitive flexibility, but this was not seen for either inhibitory control or receptive language.

MiR-135a-5p regulates window of implantation by suppressing pinopodes development and decidualization of endometrial stromal cells

PURPOSE

The window of implantation (WOI) is a brief period during which the endometrium is receptive to embryo implantation. This study investigated the relationship between miR-135a-5p and endometrial receptivity.

METHODS

Peripheral blood was collected on the day of ovulation and the 5th day after ovulation for high-throughput sequencing from women who achieved clinical pregnancy through natural cycle frozen embryo transfer. RT-qPCR assessed miR-135a-5p expression in the endometrium tissue or cells during the mouse implantation window or decidualization. Scanning electron microscopy was utilized to observe pinopode morphology and quantity in mice overexpressing miR-135a-5p during the WOI. Human endometrial stromal cells (HESC) and artificial induction of mouse uterine decidualization were used to explore whether miR-135a-5p overexpression inhibits decidualization by regulating HOXA10 and BMPR2. Furthermore, the impact of miR-135a-5p on HESC proliferation and HTR8/SVneo invasion was explored.

RESULTS

A total of 54 women were enrolled in the study. bioinformatics analysis and animal models demonstrated that miR-135a-5p was significantly downregulated during the WOI, and its high expression can lead to abnormal pregnancy outcomes. Overexpression of miR-135a-5p resulted in the absence of pinopode in mouse endometrial tissue during the WOI. High miR-135a-5p levels were found to potentially inhibit endometrial tissue decidualization by downregulating HOXA10 and BMPR2 expression. Finally, CEBPD was identified as a potential regulator of miR-135a-5p, which would explain the decreased miR-135a-5p expression during the WOI.

CONCLUSION

MiR-135a-5p expression is significantly downregulated during the WOI. High miR-135a-5p levels suppress pinopode development and endometrial tissue decidualization through HOXA10 and BMPR2, contributing to inadequate endometrial receptivity.

A review of single-cell transcriptomics and epigenomics studies in maternal and child health

Single-cell sequencing technologies enhance our understanding of cellular dynamics throughout pregnancy. We outlined the workflow of single-cell sequencing techniques and reviewed single-cell studies in maternal and child health. We conducted a literature review of single cell studies on maternal and child health using PubMed. We summarized the findings from 16 single-cell atlases of the human and mammalian placenta across gestational stages and 31 single-cell studies on maternal exposures and complications including infection, obesity, diet, gestational diabetes, pre-eclampsia, environmental exposure and preterm birth. Single-cell studies provides insights on novel cell types in placenta and cell type-specific marks associated with maternal exposures and complications.

Risk factors for placenta accreta spectrum in pregnancies conceived after frozen-thawed embryo transfer in a hormone replacement cycle

OBJECTIVE

Assisted reproductive technology (ART), especially frozen-thawed embryo transfer (FET) in a hormone replacement cycle (HRC), is a risk factor for placenta accreta spectrum (PAS). This study aimed to clarify the risk factors for PAS related to the maternal background and ART techniques in pregnancies achieved after FET in an HRC.

STUDY DESIGN

We performed a case-control study in two tertiary perinatal centres in Japan. Among 14,028 patients who delivered at ≥24 weeks of gestation or were transferred after delivery to two tertiary perinatal centres between 2010 and 2021, 972 conceived with ART and 13,056 conceived without ART. PAS was diagnosed on the basis of the FIGO classification for the clinical diagnosis of PAS or retained products of conception after delivery at ≥24 weeks of gestation. We excluded women with fresh embryo transfer, FET with a spontaneous ovulatory cycle, a donor oocyte cycle, and missing details of the ART treatment. Finally, among women who conceived after FET in an HRC, 62 with PAS and 340 without PAS were included in this study. Multivariate logistic regression models were used for case-control comparisons, with adjustment for maternal age at delivery, parity, endometriosis or adenomyosis, the number of previous uterine surgeries of caesarean section, myomectomy, endometrial polypectomy or endometrial curettage, placenta previa, the stage of transferred embryos, and endometrial thickness at the initiation of progestin administration.

RESULTS

PAS was associated with ≥2 previous uterine surgeries (adjusted odds ratio, 3.57; 95 % confidence interval, 1.60-7.97) and the stage of embryo transfer (blastocysts: adjusted odds ratio, 2.89; 95 % confidence interval, 1.15-7.26). In patients with <2 previous uterine surgeries, PAS was associated with an endometrial thickness of <7.0 mm (adjusted odds ratio, 5.18; 95 % confidence interval, 1.10-24.44).

CONCLUSION

Multiple uterine surgeries and the transfer of blastocysts are risk factors for PAS in pregnancies conceived after FET in an HRC. In women with <2 previous uterine surgeries, a thin endometrium before FET is also a risk factor for PAS in these pregnancies.

Effect of Granzyme K, FasL and Interferon-γ Expression in Placentas with Preeclampsia

This study aimed to investigate the cytotoxic activity of decidual lymphocytes and the mRNA/protein expression of cytotoxic proteins in various cell types in the context of preeclampsia (PE) compared to those of healthy pregnancies. We analyzed fresh decidua basalis tissue and tissue embedded in paraffin (FFPE) from PE pregnancies (n = 15) and compared them with those of healthy pregnancies (n = 15) of the corresponding gestational age. Using double immunofluorescence staining, we observed differences in the intensity and distribution of staining for granzyme K (GZMK) and FasL in extravillous trophoblasts. RT-qPCR analysis of FFPE placental tissue showed that GZMK mRNA expression was statistically higher (p < 0.0001) in PE compared to that of healthy controls. On the contrary, there was a low expression (p < 0.001) of FasL mRNA in PE compared to controls, while there was no statistically significant difference for IFN-γ mRNA between PE and controls. Although the level of cytotoxic activity changed depending on the ratio of effector and target cells, there was no significant difference observed between PE and controls in this in vitro study. In conclusion, in PE, extravillous trophoblasts exhibited increased expression of GZMK and decreased expression of FasL. These changes may contribute to impaired trophoblast invasion. However, these alterations did not appear to affect the cytotoxic properties of decidual lymphocytes. Additionally, the possibility of cell sorter separation of decidual lymphocytes would greatly contribute to a better understanding of single cells' genetic profiles.

Ambient air pollution and adverse birth outcomes: A review of underlying mechanisms

Epidemiological data provide varying degrees of evidence for associations between prenatal exposure to ambient air pollutants and adverse birth outcomes (suboptimal measures of fetal growth, preterm birth and stillbirth). To assess further certainty of effects, this review examines the experimental literature base to identify mechanisms by which air pollution (particulate matter, nitrogen dioxide and ozone) could cause adverse effects on the developing fetus. It likely that this environmental insult impacts multiple biological pathways important for sustaining a healthy pregnancy, depending upon the composition of the pollutant mixture and the exposure window owing to changes in physiologic maturity of the placenta, its circulations and the fetus as pregnancy ensues. The current body of evidence indicates that the placenta is a target tissue, impacted by a variety of critical processes including nitrosative/oxidative stress, inflammation, endocrine disruption, epigenetic changes, as well as vascular dysregulation of the maternal-fetal unit. All of the above can disturb placental function and, as a consequence, could contribute to compromised fetal growth as well increasing the risk of stillbirth. Furthermore, given that there is often an increased inflammatory response associated with preterm labour, inflammation is a plausible mechanism mediating the effects of air pollution on premature delivery. In the light of increased urbanisation and an ever-changing climate, both of which increase ambient air pollution and negatively affect vulnerable populations such as pregnant individuals, it is hoped that the collective evidence may contribute to decisions taken to strengthen air quality policies, reductions in exposure to air pollution and subsequent improvements in the health of those not yet born.

Do IVF culture conditions have an impact on neonatal outcomes? A systematic review and meta-analysis

PURPOSE

Are embryo culture conditions, including type of incubator, oxygen tension, and culture media, associated with obstetric or neonatal complications following in vitro fertilization (IVF)?

METHODS

A systematic search of MEDLINE, EMBASE, and Cochrane Library was performed from January 01, 2008, until October 31, 2021. The studies reporting quantitative data on at least one of the primary outcomes (birthweight and preterm birth) for the exposure group and the control group were included. For oxygen tension, independent meta-analysis was performed using Review Manager, comparing hypoxia/normoxia. For culture media, a network meta-analysis was carried out using R software, allowing the inclusion of articles comparing two or more culture media.

RESULTS

After reviewing 182 records, 39 full-text articles were assessed for eligibility. A total of 28 studies were kept for review. Meta-analysis about the impact of incubator type on perinatal outcomes could not be carried out because of a limited number of studies. For oxygen tension, three studies were included. The pairwise meta-analysis comparing hypoxia/normoxia did not show any statistical difference for birthweight and gestational age at birth. For culture media, 18 studies were included. The network meta-analysis failed to reveal any significant impact of different culture media on birthweight or preterm birth.

CONCLUSION

No difference was observed for neonatal outcomes according to the embryo culture conditions evaluated in this review. Further research is needed about the safety of IVF culture conditions as far as future children's health is concerned.

Dynamic and distinct histone modifications facilitate human trophoblast lineage differentiation

The placenta serves as an essential organ for fetal growth throughout pregnancy. Histone modification is a crucial regulatory mechanism involved in numerous biological processes and development. Nevertheless, there remains a significant gap in our understanding regarding the epigenetic regulations that influence trophoblast lineage differentiation, a fundamental aspect of placental development. Here, through comprehensive mapping of H3K4me3, H3K27me3, H3K9me3, and H3K27ac loci during the differentiation of trophoblast stem cells (TSCs) into syncytiotrophoblasts (STs) and extravillous trophoblasts (EVTs), we reveal dynamic reconfiguration in H3K4me3 and H3K27ac patterns that establish an epigenetic landscape conducive to proper trophoblast lineage differentiation. We observe that broad H3K4me3 domains are associated with trophoblast lineage-specific gene expression. Unlike embryonic stem cells, TSCs lack robust bivalent domains. Notably, the repression of ST- and EVT-active genes in TSCs is primarily attributed to the weak H3K4me3 signal rather than bivalent domains. We also unveil the inactivation of TSC enhancers precedes the activation of ST enhancers during ST formation. Our results provide a comprehensive global map of diverse histone modifications, elucidating the dynamic histone modifications during trophoblast lineage differentiation.

Exercise enhances placental labyrinth trophoblast development by activation of PGC-1α and FNDC5/irisin†

Placental chorion/labyrinth trophoblasts are energy demanding which is met by the mitochondrial oxidative phosphorylation. Exercise enhances placental development and mitochondrial biogenesis, but the underlying mechanisms remain poorly understood. To address, female C57BL/6 J mice were randomly assigned into two groups: a control group and an exercise (EX) group. All animals were acclimated to treadmill exercise for 1 week before mating, but only the EX group was subjected to daily exercise during pregnancy from embryonic day (E) 1.5 to E16.5. Placenta were collected at E18.5 for biochemical and histochemical analyses, and primary trophoblast cells were isolated from the E18.5 placenta for further analyses. The data showed that exercise during pregnancy promoted the expression of syncytiotrophoblast cell markers, indicating trophoblast cell differentiation, which was closely associated with elevated mitochondrial biogenesis and oxidative metabolism in the E18.5 placenta. In addition, exercise during pregnancy activated peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α), which was associated with upregulated placental α-ketoglutarate and the expression of isocitrate dehydrogenases and ten-eleven translocations, facilitating DNA demethylation of the Pgc1a promoter. Furthermore, exercise upregulated fibronectin type III domain containing 5 expression and the secretion of its cleaved form, irisin, which is known to activate PGC-1α. These data suggest that exercise-induced activation of PGC-1α, via epigenetic modifications, is responsible for promoting mitochondrial energy metabolism and chorion/labyrinth trophoblast development.

Major postpartum haemorrhage after frozen embryo transfer: A population-based study

OBJECTIVE

To investigate the effect on major postpartum haemorrhage (PPH) of mode of conception, differentiating between naturally conceived pregnancies, fresh embryo in vitro fertilisation (fresh-IVF) and frozen embryo transfer (frozen-IVF).

DESIGN

Retrospective cohort study.

SETTING

The French Burgundy Perinatal Network database, including all deliveries from 2006 to 2020, was linked to the regional blood centre database.

POPULATION OR SAMPLE

In all, 244 336 women were included, of whom 240 259 (98.3%) were singleton pregnancies.

METHODS

The main analyses were conducted in singleton pregnancies, including 237 608 naturally conceived, 1773 fresh-IVF and 878 frozen-IVF pregnancies. Multivariate logistic regression models adjusted on maternal age, body mass index, smoking, parity, induction of labour, hypertensive disorders, diabetes, placenta praevia and/or accreta, history of caesarean section, mode of delivery, birthweight, birth place and year of delivery, were used.

MAIN OUTCOME MEASURES

Major PPH was defined as PPH requiring blood transfusion and/or emergency surgery and/or interventional radiology.

RESULTS

The prevalence of major PPH was 0.74% (n = 1749) in naturally conceived pregnancies, 1.92% (n = 34) in fresh-IVF pregnancies, and 3.30% (n = 29) in frozen-IVF pregnancies. The risk of major PPH was higher in frozen-IVF pregnancies than in both naturally conceived pregnancies (adjusted odds ratio [aOR] 2.63, 95% CI 1.68-4.10) and fresh-IVF pregnancies (aOR 2.78, 95% CI 1.44-5.35).

CONCLUSIONS

We found that frozen-IVF pregnancies have a higher risk of major PPH and they should be subject to increased vigilance in the delivery room.

Gestational diabetes mellitus: genetic factors, epigenetic alterations, and microbial composition

Gestational diabetes mellitus (GDM) is a common metabolic disorder, usually diagnosed during the third trimester of pregnancy that usually disappears after delivery. In GDM, the excess of glucose, fatty acids, and amino acids results in foetuses large for gestational age. Hyperglycaemia and insulin resistance accelerate the metabolism, raising the oxygen demand, and creating chronic hypoxia and inflammation. Women who experienced GDM and their offspring are at risk of developing type-2 diabetes, obesity, and other metabolic or cardiovascular conditions later in life. Genetic factors may predispose the development of GDM; however, they do not account for all GDM cases; lifestyle and diet also play important roles in GDM development by modulating epigenetic signatures and the body's microbial composition; therefore, this is a condition with a complex, multifactorial aetiology. In this context, we revised published reports describing GDM-associated single-nucleotide polymorphisms (SNPs), DNA methylation and microRNA expression in different tissues (such as placenta, umbilical cord, adipose tissue, and peripheral blood), and microbial composition in the gut, oral cavity, and vagina from pregnant women with GDM, as well as the bacterial composition of the offspring. Altogether, these reports indicate that a number of SNPs are associated to GDM phenotypes and may predispose the development of the disease. However, extrinsic factors (lifestyle, nutrition) modulate, through epigenetic mechanisms, the risk of developing the disease, and some association exists between the microbial composition with GDM in an organ-specific manner. Genes, epigenetic signatures, and microbiota could be transferred to the offspring, increasing the possibility of developing chronic degenerative conditions through postnatal life.

Modeling placental development and disease using human pluripotent stem cells

Our current knowledge of the cellular and molecular mechanisms of placental epithelial cells, trophoblast, primarily came from the use of mouse trophoblast stem cells and tumor-derived or immortalized human trophoblast cell lines. This was mainly due to the difficulties in maintaining primary trophoblast in culture and establishing human trophoblast stem cell (hTSC) lines. However, in-depth characterization of these cellular models and in vivo human trophoblast have revealed significant discrepancies. For the past two decades, multiple groups have shown that human pluripotent stem cells (hPSCs) can be differentiated into trophoblast, and thus could be used as a model for normal and disease trophoblast differentiation. During this time, trophoblast differentiation protocols have evolved, enabling researchers to study cellular characteristics at trophectoderm (TE), trophoblast stem cells (TSC), syncytiotrophoblast (STB), and extravillous trophoblast (EVT) stages. Recently, several groups reported methods to derive hTSC from pre-implantation blastocyst or early gestation placenta, and trophoblast organoids from early gestation placenta, drastically changing the landscape of trophoblast research. These culture conditions have been rapidly applied to generate hPSC-derived TSC and trophoblast organoids. As a result of these technological advancements, the field's capacity to better understand trophoblast differentiation and their involvement in pregnancy related disease has greatly expanded. Here, we present in vitro models of human trophoblast differentiation, describing both primary and hPSC-derived TSC, maintained as monolayers and 3-dimensional trophoblast organoids, as a tool to study early placental development and disease in multiple settings.

Long-Term Effects of ART on the Health of the Offspring

Assisted reproductive technologies (ART) significantly increase the chance of successful pregnancy and live birth in infertile couples. The different procedures for ART, including in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), intrauterine insemination (IUI), and gamete intrafallopian tube transfer (GIFT), are widely used to overcome infertility-related problems. In spite of its inarguable usefulness, concerns about the health consequences of ART-conceived babies have been raised. There are reports about the association of ART with birth defects and health complications, e.g., malignancies, high blood pressure, generalized vascular functional disorders, asthma and metabolic disorders in later life. It has been suggested that hormonal treatment of the mother, and the artificial environment during the manipulation of gametes and embryos may cause genomic and epigenetic alterations and subsequent complications in the health status of ART-conceived babies. In the current study, we aimed to review the possible long-term consequences of different ART procedures on the subsequent health status of ART-conceived offspring, considering the confounding factors that might account for/contribute to the long-term consequences.

Altered distribution of fatty acid exerting lipid metabolism and transport at the maternal-fetal interface in fetal growth restriction

INTRODUCTION

Fetal growth restriction (FGR) is a common complication of pregnancy. Lipid metabolism and distribution may contribute to the progression of FGR. However, the metabolism-related mechanisms of FGR remain unclear. The aim of this study was to identify metabolic profiles associated with FGR, as well as probable genes and signaling pathways.

METHODS

Metabolomic profiles at the maternal-fetal interface (including the placenta, maternal and fetal serum) from pregnant women with (n = 35) and without (n = 35) FGR were analyzed by gas chromatography-mass spectrometry (GC-MS). Combined with differentially expressed genes (DEGs) from the GSE35574 dataset, analysis was performed for differential metabolites, and identified by the Metabo Analyst dataset. Finally, the pathology and screened DEGs were further identified.

RESULTS

The results showed that fatty acids (FAs) accumulated in the placenta and decreased in fetal blood in FGR cases compared to controls. The linoleic acid metabolism was the focus of placental differential metabolites and genes enrichment analysis. In this pathway, phosphatidylcholine can interact with PLA2G2A and PLA2G4C, and 12(13)-EpOME can interact with CYP2J2. PLA2G2A and CYP2J2 were elevated, and PLA2G4C was decreased in the FGR placenta.

DISCUSSION

In conclusion, accumulation of FAs in the placental ischemic environments, may involve linoleic acid metabolism, which may be regulated by PLA2G2A, CYP2J2, and PLA2G4C. This study may contribute to understanding the underlying metabolic and molecular mechanisms of FGR.

Pregnancy, infection, and epigenetic regulation: A complex scenario

A unique immunological condition, pregnancy ensures fetus from maternal rejection, allows adequate fetal development, and protects against microorganisms. Infections during pregnancy may lead to devastating consequences for pregnant women and fetuses, resulting in the mother's death, miscarriage, premature childbirth, or neonate with congenital infection and severe diseases and defects. Epigenetic (heritable changes in gene expression) mechanisms like DNA methylation, chromatin modification, and gene expression modulation during gestation are linked with the number of defects in the fetus and adolescents. The feto-maternal crosstalk for fetal survival during the entire gestational stages are tightly regulated by various cellular pathways, including epigenetic mechanisms that respond to both internal as well outer environmental factors, which can influence the fetal development across the gestational stages. Due to the intense physiological, endocrinological, and immunological changes, pregnant women are more susceptible to bacterial, viral, parasitic, and fungal infections than the general population. Microbial infections with viruses (LCMV, SARS-CoV, MERS-CoV, and SARS-CoV-2) and bacteria (Clostridium perfringens, Coxiella burnetii, Listeria monocytogenes, Salmonella enteritidis) further increase the risk to maternal and fetal life and developmental outcome. If the infections remain untreated, the possibility of maternal and fetal death exists. This article focused on the severity and susceptibility to infections caused by Salmonella, Listeria, LCMV, and SARS-CoV-2 during pregnancy and their impact on maternal health and the fetus. How epigenetic regulation during pregnancy plays a vital role in deciding the fetus's developmental outcome under various conditions, including infection and other stress. A better understanding of the host-pathogen interaction, the characterization of the maternal immune system, and the epigenetic regulations during pregnancy may help protect the mother and fetus from infection-mediated outcomes.

Understanding PPARγ and Its Agonists on Trophoblast Differentiation and Invasion: Potential Therapeutic Targets for Gestational Diabetes Mellitus and Preeclampsia

The increasing incidence of pregnancy complications, particularly gestational diabetes mellitus (GDM) and preeclampsia (PE), is a cause for concern, as they can result in serious health consequences for both mothers and infants. The pathogenesis of these complications is still not fully understood, although it is known that the pathologic placenta plays a crucial role. Studies have shown that PPARγ, a transcription factor involved in glucose and lipid metabolism, may have a critical role in the etiology of these complications. While PPARγ agonists are FDA-approved drugs for Type 2 Diabetes Mellitus, their safety during pregnancy is not yet established. Nevertheless, there is growing evidence for the therapeutic potential of PPARγ in the treatment of PE using mouse models and in cell cultures. This review aims to summarize the current understanding of the mechanism of PPARγ in placental pathophysiology and to explore the possibility of using PPARγ ligands as a treatment option for pregnancy complications. Overall, this topic is of great significance for improving maternal and fetal health outcomes and warrants further investigation.

Integration of nutrigenomics, melatonin, serotonin and inflammatory cytokines in the pathophysiology of pregnancy-specific urinary incontinence in women with gestational diabetes mellitus

Gestational diabetes mellitus is an important public health problem and has been associated with the development of pregnancy-specific urinary incontinence. The interaction is related to hyperglycemia, and inflammatory and hormonal patterns, which favor functional alterations in different organs and systems. Several genes associated with human diseases have been identified and partially characterized. Most of these genes are known to cause monogenic diseases. However, about 3 % of diseases do not fit the monogenic theory due to the complex interactions between multiple genes and environmental factors, as in chronic metabolic diseases such as diabetes. The nutritional, immunological, and hormonal patterns associated with changes in maternal metabolism may influence and contribute to greater susceptibility to urinary tract disorders. However, early systematic reviews have not yielded consistent findings for these associations. This literature review summarizes important new findings from integrating nutrigenomics, hormones, and cytokines in women with Gestational diabetes mellitus and pregnancy-specific urinary incontinence. Changes in maternal metabolism due to hyperglycemia can generate an inflammatory environment with increased inflammatory cytokines. This environment modulated by inflammation can alter tryptophan uptake through food and thus influence the production of serotonin and melatonin. As these hormones seem to have protective effects against smooth muscle dysfunction and to restore the impaired contractility of the detrusor muscle, it is assumed that these changes may favor the onset of urinary incontinence specific to pregnancy.

Circulating biomarkers associated with placental dysfunction and their utility for predicting fetal growth restriction

Fetal growth restriction (FGR) leading to low birth weight (LBW) is a major cause of neonatal morbidity and mortality worldwide. Normal placental development involves a series of highly regulated processes involving a multitude of hormones, transcription factors, and cell lineages. Failure to achieve this leads to placental dysfunction and related placental diseases such as pre-clampsia and FGR. Early recognition of at-risk pregnancies is important because careful maternal and fetal surveillance can potentially prevent adverse maternal and perinatal outcomes by judicious pregnancy surveillance and careful timing of birth. Given the association between a variety of circulating maternal biomarkers, adverse pregnancy, and perinatal outcomes, screening tests based on these biomarkers, incorporating maternal characteristics, fetal biophysical or circulatory variables have been developed. However, their clinical utility has yet to be proven. Of the current biomarkers, placental growth factor and soluble fms-like tyrosine kinase 1 appear to have the most promise for placental dysfunction and predictive utility for FGR.

Expression of Glucose Transporters 1 and 3 in the Placenta of Pregnant Women with Gestational Diabetes Mellitus

BACKGROUND

The annual prevalence of gestational diabetes mellitus-characterized by an increase in blood glucose in pregnant women-has been increasing worldwide. The goal of this study was to evaluate the expression of glucose transporter 1 (GLUT1) and glucose transporter 3 (GLUT3) in the placenta of women with gestational diabetes mellitus.

METHODS

Sixty-five placentas from women admitted to the King Saud University Medical City, Riyadh, Saudi Arabia, were analyzed; 34 and 31 placentas were from healthy pregnant women and women with gestational diabetes, respectively. The expressions of GLUT1 and GLUT3 were assessed using RT-PCR, Western blotting, and immunohistochemical methods. The degree of apoptosis in the placental villi was estimated via a TUNEL assay.

RESULTS

The results of the protein expression assays and immunohistochemical staining showed that the levels of GLUT1 and GLUT3 were significantly higher in the placentas of pregnant women with gestational diabetes than those in the placentas of healthy pregnant women. In addition, the findings showed an increase in apoptosis in the placenta of pregnant women with gestational diabetes compared to that in the placenta of healthy pregnant women. However, the results of gene expression assays showed no significant difference between the two groups.

CONCLUSIONS

Based on these results, we conclude that gestational diabetes mellitus leads to an increased incidence of apoptosis in the placental villi and alters the level of GLUT1 and GLUT3 protein expressions in the placenta of women with gestational diabetes. Understanding the conditions in which the fetus develops in the womb of a pregnant woman with gestational diabetes may help researchers understand the underlying causes of the development of chronic diseases later in life.

Dynamics of the Equine Placental DNA Methylome and Transcriptome from Mid- to Late Gestation

The placenta is a temporary organ that is essential for the survival of the fetus, with a lifelong effect on the health of both the offspring and the dam. The functions of the placenta are controlled by its dynamic gene expression during gestation. In this study, we aimed to investigate the equine placental DNA methylome as one of the fundamental mechanisms that controls the gene expression dynamic. Chorioallantois samples from four (4M), six (6M), and ten (10M) months of gestation were used to map the methylation pattern of the placenta. Globally, methylation levels increased toward the end of gestation. We identified 921 differentially methylated regions (DMRs) between 4M and 6M, 1225 DMRs between 4M and 10M, and 1026 DMRs between 6M and 10M. A total of 817 genes carried DMRs comparing 4M and 6M, 978 comparing 4M and 10M, and 804 comparing 6M and 10M. We compared the transcriptomes between the samples and found 1381 differentially expressed genes (DEGs) when comparing 4M and 6M, 1428 DEGs between 4M and 10M, and 741 DEGs between 6M and 10M. Finally, we overlapped the DEGs and genes carrying DMRs (DMRs-DEGs). Genes exhibiting (a) higher expression, low methylation and (b) low expression, high methylation at different time points were identified. The majority of these DMRs-DEGs were located in introns (48.4%), promoters (25.8%), and exons (17.7%) and were involved in changes in the extracellular matrix; regulation of epithelial cell migration; vascularization; and regulation of minerals, glucose, and metabolites, among other factors. Overall, this is the first report highlighting the dynamics in the equine placenta methylome during normal pregnancy. The findings presented serve as a foundation for future studies on the impact of abnormal methylation on the outcomes of equine pregnancies.

Altered Epigenetic Profiles in the Placenta of Preeclamptic and Intrauterine Growth Restriction Patients

Intrauterine growth restriction (IUGR) and preeclampsia (PE) are placental pathologies known to complicate pregnancy and cause neonatal disorders. To date, there is a limited number of studies on the genetic similarity of these conditions. DNA methylation is a heritable epigenetic process that can regulate placental development. Our objective was to identify methylation patterns in placental DNA from normal, PE and IUGR-affected pregnancies. DNA was extracted, and bisulfite was converted, prior to being hybridized for the methylation array. Methylation data were SWAN normalized and differently methylated regions were identified using applications within the USEQ program. UCSC's Genome browser and Stanford's GREAT analysis were used to identify gene promoters. The commonality among affected genes was confirmed by Western blot. We observed nine significantly hypomethylated regions, two being significantly hypomethylated for both PE and IGUR. Western blot confirmed differential protein expression of commonly regulated genes. We conclude that despite the uniqueness of methylation profiles for PE and IUGR, the similarity of some methylation alterations in pathologies could explain the clinical similarities observed with these obstetric complications. These results also provide insight into the genetic similarity between PE and IUGR and suggest possible gene candidates plausibly involved in the onset of both conditions.

Association of Placental Pathologic Findings with the Severity of Necrotizing Enterocolitis in Preterm infants - A Matched Case-Control Study

OBJECTIVE

To determine the association of placental pathology with the severity of necrotizing enterocolitis (NEC) in preterm infants.

METHODS

This single-center matched case-control study included infants with NEC (n = 107) and gestational age and birth weight-matched controls (n = 130), born between 2013 and 2020. Placentas were evaluated according to the Amsterdam Placental Workshop Group Consensus Statement.

RESULTS

Acute histologic chorioamnionitis with the fetal response was significantly more common in infants with surgical NEC vs. medical NEC (35.4% vs. 15.3%; p = 0.02). On regression model, infants with multiple placental pathologies (OR 2.16; 95% CI 1.01 - 4.73; p = 0.04) and maternal vascular malperfusion (OR 2.2; 95% CI 1.12 - 4.51; p = 0.02) had higher odds of either medical or surgical NEC than controls.

CONCLUSION

Infants with multiple placental lesions, including placental inflammatory and vascular lesions, were at higher risk of medical or surgical NEC in the postnatal period.

Gse1, a component of the CoREST complex, is required for placenta development in the mouse

Gse1 is a component of the CoREST complex that acts as an H3K4 and H3K9 demethylase and regulates gene expression. Here, we examined the expression and role of Gse1 in mouse development. Gse1 is expressed in male and female germ cells and plays both maternal and zygotic roles. Thus, maternal deletion of Gse1 results in a high incidence of prenatal death, and zygotic deletion leads to embryonic lethality from embryonic day 12.5 (E12.5) and perinatal death. Gse1 is expressed in the junctional zone and the labyrinth of the developing placenta. Cultured trophoblast stem cells lacking Gse1 showed impaired in vitro cell differentiation into spongiotrophoblasts. Gse1 mutant (Gse1^Δex3/Δex3) placenta begins to exhibit histological defects from E14.5, being deficient in MCT4⁺ syncytiotrophoblast II. The number of various cell types was largely maintained in the mutant placenta at E10.5, but several genes were upregulated in giant trophoblasts at E10.5. Placenta-specific deletion of Gse1 with Tat-Cre suggested that defects in Gse1^Δex3/Δex3 embryos are due to placental function deficiency. These results suggest that Gse1 is required for placental development in mice, and in turn, is essential for embryonic development.

Epigenetic Mechanisms Involved in the Effects of Maternal Hyperhomocysteinemia on the Functional State of Placenta and Nervous System Plasticity in the Offspring

According to modern view, susceptibility to diseases, specifically to cognitive and neuropsychiatric disorders, can form during embryonic development. Adverse factors affecting mother during the pregnancy increase the risk of developing pathologies. Despite the association between elevated maternal blood homocysteine (Hcy) and fetal brain impairments, as well as cognitive deficits in the offspring, the role of brain plasticity in the development of these pathologies remains poorly studied. Here, we review the data on the negative impact of hyperhomocysteinemia (HHcy) on the neural plasticity, in particular, its possible influence on the offspring brain plasticity through epigenetic mechanisms, such as changes in intracellular methylation potential, activity of DNA methyltransferases, DNA methylation, histone modifications, and microRNA expression in brain cells. Since placenta plays a key role in the transport of nutrients and transmission of signals from mother to fetus, its dysfunction due to aberrant epigenetic regulation can affect the development of fetal CNS. The review also presents the data on the impact of maternal HHcy on the epigenetic regulation in the placenta. The data presented in the review are not only interesting from purely scientific point of view, but can help in understanding the role of HHcy and epigenetic mechanisms in the pathogenesis of diseases, such as pregnancy pathologies resulting in the delayed development of fetal brain, cognitive impairments in the offspring during childhood, and neuropsychiatric and neurodegenerative disorders later in life, as well as in the search for approaches for their prevention using neuroprotectors.

N6-methyladenosine modifications in maternal-fetal crosstalk and gestational diseases

As a medium among pregnant women, environment and fetus, placenta owns powerful and delicate epigenetic processes to regulate gene expression and maintain cellular homeostasis. N6-methyladenosine (m6A) is the most prevalent modification that determines the fate of RNA, and its dynamic reversibility indicates that m6A may serve as a sensitive responder to environmental stimuli. Emerging evidence suggests that m6A modifications play an essential role in placental development and maternal-fetal crosstalk, and are closely related to gestational diseases. Herein, we summarized the latest techniques for m6A sequencing and highlighted current advances of m6A modifications in maternal-fetal crosstalk and the underlying mechanisms in gestational diseases. Therefore, proper m6A modifications are important in placental development, but its disturbance mainly caused by various environmental factors can lead to abnormal placentation and function with possible consequences of gestational diseases, fetal growth and disease susceptibility in adulthood.

Comparing endometrial preparation methods in frozen embryo transfers - Does a previous live birth make a difference?

RESEARCH QUESTION

Does the outcome of a medicated or natural endometrial preparation for a frozen cycle differ if a patient has previously experienced a failed fresh cycle?

DESIGN

Retrospective matched case-controlled study to investigate frozen embryo transfer (FET) outcomes in women undergone medicated or natural endometrial preparation, with adjustment to the history of previous live birth. 878 frozen cycles were included for analysis, over a period of 2 years.

RESULTS

After adjusting for the number of embryos transferred, endometrial thickness and the number of previous embryo transfers, there was no difference in live birth rate (LBR) between medicated-FET and natural-FET groups regardless of the previous fertility outcome (p = 0.08).

CONCLUSIONS

A previous live birth does not affect the outcome of a subsequent frozen cycle, regardless of whether medicated- or natural endometrial preparation is used.

Maternal exposure to a glyphosate-based herbicide impairs placental development through endoplasmic reticulum stress in mice

Glyphosate-based herbicides (GBHs) are the most widely used agrochemicals worldwide, increasing the risk of their occurrence in the environment. This study aimed to explore effects and mechanisms of GBH exposure on placental development in vivo during pregnancy in mice. Pregnant mice received GBH by gavage at 0, 5, and 50 mg⋅kg^-1⋅day^-1 doses from gestational day (GD) 1 to GD 13 and were sacrificed on GD 13 or GD19. Our data indicated that GBH administration significantly increased the number of resorbed fetuses, reduced the weight of fetuses and placentas, and inhibited placental growth, as evident from decreased placental total area and spongiotrophoblast area on GD 19. GBH treatment also inhibited proliferation and induced apoptosis of placenta via upregulation of Bax, cleaved caspase-3 and -12 expression, and downregulation of B cell lymphoma (Bcl)-2 expression. Further study showed that GBH exposure significantly increased expression levels of glucose-regulated protein 78 (GRP78), protein kinase RNA-like endoplasmic reticulum kinase (PERK), and C/EBP homologous protein (CHOP) mRNAs and proteins and triggered oxidative stress in placenta on GD 13 and GD 19. In conclusion, our findings suggest that maternal exposure to GBH can impair placental development through the endoplasmic reticulum stress-mediated activation of GRP78/PERK/CHOP signaling pathway in mice.

Correlation of placental pathology with the postoperative outcomes and white matter injury in preterm infants following necrotizing enterocolitis

BACKGROUND

To determine the association of placental pathologic lesions with postoperative outcomes, survival, and white matter injury (WMI) in preterm infants with NEC.

METHODS

A retrospective chart review of 107 neonates with NEC (Bell stage > IIa) from Jan 2013- June 2020 was completed. Demographic, clinical, and outcome data were compared between infants with or without placental pathologic lesions.

RESULTS

In this cohort, 59/107 (55%) infants had medical NEC, and 48 (45%) had surgical NEC. The infants had a mean gestational age of 28.1±3.7 weeks and a birth weight of 1103±647 g. Maternal vascular malperfusion (82/107, 76.6%) and acute histological chorioamnionitis (42, 39.3%) were the most common pathological placental lesions. Acute histologic chorioamnionitis with fetal inflammatory response was more common in infants with surgical NEC vs. medical NEC (35.4% vs. 15.3%; p = 0.02). The NEC Infants with WMI on brain MRI scans had a significantly higher incidence of acute histological chorioamnionitis (52% vs. 27.8%; P = 0.04). No significant differences in mortality, length of stay and postoperative outcomes in neonates with and without acute histologic chorioamnionitis with fetal inflammatory response were noted. On unadjusted logistic regression, acute histologic chorioamnionitis without fetal inflammatory response was also associated with higher odds of WMI (OR 2.81; 95% CI 1.05-7.54; p = 0.039).

CONCLUSION

Acute histological chorioamnionitis without fetal inflammatory response was associated with higher odds of WMI in infants with NEC, with no significant impact on mortality and other postoperative outcomes.

Gestational exposure to perfluoroalkyl substances is associated with placental DNA methylation and birth size

DNA methylation is one potential mechanism for the effects of gestational exposure to perfluoroalkyl substances (PFASs) on fetal growth. We investigated 180 pregnant women who participated in a cohort study conducted in Tangshan City, Northern China, and determined the concentrations of 11 PFASs and the methylation of two genes related to fetal growth [insulin-like growth factor 2 (IGF2) and nuclear receptor subfamily 3 group C member 1 (NR3C1)] and one surrogate marker for global methylation [long interspersed nuclear element-1 (LINE-1)] in placenta tissue. Multiple linear regression analysis was performed to examine the associations of log transformed PFASs with the DNA methylation and birth size. Weighted quantile sum regression was used to determine the mixture effect of PFASs. After adjusting for potential confounders, perfluorooctane sulfonate (PFOS) was negatively associated with the overall methylation of LINE-1. PFASs mixture was negatively associated with the methylation of all CpG loci of LINE-1 and overall methylation of NR3C1. Perfluorootanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), and the PFASs mixture showed negative associations with head circumference. After stratified by newborns' sex, PFOA, PFNA and the PFASs mixture was negatively associated with overall methylation of LINE-1 only in the male subgroup and the methylation of all CpG loci of LINE-1 was negatively associated with ponderal index only in the female subgroup. The interaction of newborns' sex with PFOS and PFOA on overall methylation of IGF2 was statistically significant and so was the interaction of sex with PFOS on overall methylation of LINE-1. These findings suggested that intrauterine exposure to PFASs affected placental DNA methylation and reduced fetal growth, which might be modified by sex.

Risk of Hypertensive Disorders in Pregnancy After Fresh and Frozen Embryo Transfer in Assisted Reproduction: A Population-Based Cohort Study With Within-Sibship Analysis

BACKGROUND

Frozen embryo transfer (frozen-ET) is increasingly common because of improved cryopreservation methods and elective freezing of all embryos. Frozen-ET is associated with higher risk of hypertensive disorders in pregnancy than both natural conception and fresh embryo transfer (fresh-ET), but whether this is attributable to parental factors or treatment is unknown.

METHODS

Using the Medical Birth Registries of Denmark (1994-2014), Norway, and Sweden (1988-2015), linked to data from national quality registries and databases on assisted reproduction, we designed a population-based cohort study with within-sibship comparison. We included 4 426 691 naturally conceived, 78 300 fresh-ET, and 18 037 frozen-ET singleton pregnancies, of which 33 209 sibships were conceived using different conception methods. Adjusted odds ratios (aOR) of hypertensive disorders in pregnancy for fresh-ET and frozen-ET versus natural conception with 95% CI were estimated using multilevel logistic regression, where random effects provided conventional population-level estimates and fixed effects gave within-sibship estimates. Main models included adjustment for birth year, maternal age, parity, and country.

RESULTS

Risk of hypertensive disorders in pregnancy was higher after frozen-ET compared to natural conception, both at population-level (7.4% versus 4.3%, aOR, 1.74 [95% CI, 1.61-1.89]) and within sibships (aOR, 2.02 [95% CI, 1.72-2.39]). For fresh-ET, risk was similar to natural conception, both at population-level (aOR, 1.02 [95% CI, 0.98-1.07]) and within sibships (aOR, 0.99 [95% CI, 0.89-1.09]).

CONCLUSIONS

Frozen-ET was associated with substantially higher risk of hypertensive disorders in pregnancy, even after accounting for shared parental factors within sibships.

Assisted Reproductive Technology without Embryo Discarding or Freezing in Women ≥40 Years: A 5-Year Retrospective Study at a Single Center in Italy

The protocols commonly used in assisted reproductive technology (ART) consist of long-term embryo culture up to the blastocyst stage after the insemination of all mature oocytes, the freezing of all the embryos produced, and their subsequent transfer one by one. These practices, along with preimplantation genetic testing, although developed to improve the live birth rate (LBR) and reduce the risk of multiple pregnancies, are drawing attention to the possible increase in obstetric and perinatal risks, and adverse epigenetic consequences in offspring. Furthermore, ethical-legal concerns are growing regarding the increase in cryopreservation and storage of frozen embryos. In an attempt to reduce the risk associated with prolonged embryo culture and avoid embryo storage, we have chosen to inseminate a limited number of oocytes not exceeding the number of embryos to be transferred, after two days or less of culture. We retrospectively analyzed 245 ICSI cycles performed in 184 infertile couples with a female partner aged ≥40 from January 2016 to July 2021. The results showed a fertilization rate of 95.7%, a miscarriage rate of 48.9%, and a LBR of 10% with twin pregnancies of 16.7%. The cumulative LBR in our group of couples was 13%. No embryos were frozen. In conclusion, these results suggest that oocyte selection and embryo transfer at the cleaving stage constitute a practice that has a LBR comparable to that of the more commonly used protocols in older women who have reduced ovarian reserve.

The Placental Function Beyond Pregnancy: Insights from Latin America

Currently, more than 100,000 papers had been published studying the placenta in both physiological and pathological contexts. However, relevant health conditions affecting placental function, mostly found in low-income countries, should be evaluated deeper. This review will raise some - of what we think necessary - points of discussion regarding challenging topics not fully understood, including the paternal versus maternal contribution on placental genes imprinting, placenta-brain communication, and some environmental conditions affecting the placenta. The discussions are parts of an international effort to fulfil some gaps observed in this area, and Latin-American research groups currently evaluate that.

Dietary Impacts on Gestational Diabetes: Connection between Gut Microbiome and Epigenetic Mechanisms

Gestational diabetes mellitus (GDM) is one of the most common obstetric complications due to an increased level of glucose intolerance during pregnancy. The prevalence of GDM increases due to the obesity epidemic. GDM is also associated with an increased risk of gestational hypertension and preeclampsia resulting in elevated maternal and perinatal morbidity and mortality. Diet is one of the most important environmental factors associated with etiology of GDM. Studies have shown that the consumption of certain bioactive diets and nutrients before and during pregnancy might have preventive effects against GDM leading to a healthy pregnancy outcome as well as beneficial metabolic outcomes later in the offspring's life. Gut microbiome as a biological ecosystem bridges the gap between human health and diseases through diets. Maternal diets affect maternal and fetal gut microbiome and metabolomics profiles, which consequently regulate the host epigenome, thus contributing to later-life metabolic health in both mother and offspring. This review discusses the current knowledge regarding how epigenetic mechanisms mediate the interaction between maternal bioactive diets, the gut microbiome and the metabolome leading to improved metabolic health in both mother and offspring.

The emerging role of epigenetic regulation in the progression of silicosis

Silicosis is one of the most severe occupational diseases worldwide and is characterized by silicon nodules and diffuse pulmonary fibrosis. However, specific treatments for silicosis are still lacking at present. Therefore, elucidating the pathogenesis of silicosis plays a significant guiding role for its treatment and prevention. The occurrence and development of silicosis are accompanied by many regulatory mechanisms, including epigenetic regulation. The main epigenetic regulatory mechanisms of silicosis include DNA methylation, non-coding RNA (ncRNA), and histone modifications. In recent years, the expression and regulation of genes related to silicosis have been explored at epigenetic level to reveal its pathogenesis further, and the identification of aberrant epigenetic markers provides new biomarkers for prediction and diagnosis of silicosis. Here, we summarize the studies on the role of epigenetic changes in the pathogenesis of silicosis to give some clues for finding specific therapeutic targets for silicosis.

Non-coding RNAs: The link between maternal malnutrition and offspring metabolism

Early life nutrition is associated with the development and metabolism in later life, which is known as the Developmental Origin of Health and Diseases (DOHaD). Epigenetics have been proposed as an important explanation for this link between early life malnutrition and long-term diseases. Non-coding RNAs (ncRNAs) may play a role in this epigenetic programming. The expression of ncRNAs (such as long non-coding RNA H19, microRNA-122, and circular RNA-SETD2) was significantly altered in specific tissues of offspring exposed to maternal malnutrition. Changes in these downstream targets of ncRNAs lead to abnormal development and metabolism. This review aims to summarize the existing knowledge on ncRNAs linking the maternal nutrition condition and offspring metabolic diseases, such as obesity, type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD).

Epigenetics Beyond Fetal Growth Restriction: A Comprehensive Overview

Fetal growth restriction is a pathological condition occurring when the fetus does not reach the genetically determined growth potential. The etiology of fetal growth restriction is expected to be multifactorial and include fetal, maternal, and placental factors, the latter being the most frequent cause of isolated fetal growth restriction. Severe fetal growth restriction has been related to both an increased risk of perinatal morbidity and mortality, and also a greater susceptibility to developing diseases (especially cardio-metabolic and neurological disorders) later in life. In the last decade, emerging evidence has supported the hypothesis of the Developmental Origin of Health and Disease, which states that individual developmental 'programming' takes place via a delicate fine tuning of fetal genetic and epigenetic marks in response to a large variety of 'stressor' exposures during pregnancy. As the placenta is the maternal-fetal interface, it has a crucial role in fetal programming, such that any perturbation altering placental function interferes with both in-utero fetal growth and also with the adult life phenotype. Several epigenetic mechanisms have been highlighted in modulating the dynamic placental epigenome, including alterations in DNA methylation status, post-translational modification of histones, and non-coding RNAs. This review aims to provide a comprehensive and critical overview of the available literature on the epigenetic background of fetal growth restriction. A targeted research strategy was performed using PubMed, MEDLINE, Embase, and The Cochrane Library up to January 2022. A detailed and fully referenced synthesis of available literature following the Scale for the Assessment of Narrative Review Articles guidelines is provided. A variety of epigenetic marks predominantly interfering with placental development, function, and metabolism were found to be potentially associated with fetal growth restriction. Available evidence on the role of environmental exposures in shaping the placental epigenome and the fetal phenotype were also critically discussed. Because of the highly dynamic crosstalk between epigenetic mechanisms and the extra level of complexity in interpreting the final placental transcriptome, a full comprehension of these phenomenon is still lacking and advances in multi-omics approaches are urgently needed. Elucidating the role of epigenetics in the developmental origins of health and disease represents a new challenge for the coming years, with the goal of providing early interventions and prevention strategies and, hopefully, new treatment opportunities.

Wildfire Smoke Exposure during Pregnancy: A Review of Potential Mechanisms of Placental Toxicity, Impact on Obstetric Outcomes, and Strategies to Reduce Exposure

Climate change is accelerating the intensity and frequency of wildfires globally. Understanding how wildfire smoke (WS) may lead to adverse pregnancy outcomes and alterations in placental function via biological mechanisms is critical to mitigate the harms of exposure. We aim to review the literature surrounding WS, placental biology, biological mechanisms underlying adverse pregnancy outcomes as well as interventions and strategies to avoid WS exposure in pregnancy. This review includes epidemiologic and experimental laboratory-based studies of WS, air pollution, particulate matter (PM), and other chemicals related to combustion in relation to obstetric outcomes and placental biology. We summarized the available clinical, animal, and placental studies with WS and other combustion products such as tobacco, diesel, and wood smoke. Additionally, we reviewed current recommendations for prevention of WS exposure. We found that there is limited data specific to WS; however, studies on air pollution and other combustion sources suggest a link to inflammation, oxidative stress, endocrine disruption, DNA damage, telomere shortening, epigenetic changes, as well as metabolic, vascular, and endothelial dysregulation in the maternal-fetal unit. These alterations in placental biology contribute to adverse obstetric outcomes that disproportionally affect the most vulnerable. Limiting time outdoors, wearing N95 respirator face masks and using high quality indoor air filters during wildfire events reduces exposure to related environmental exposures and may mitigate morbidities attributable to WS.

Placental DNA Methylation in pregnancies complicated by maternal diabetes and/or obesity: State of the Art and research gaps

SUMMARYMaternal diabetes and/or obesity in pregnancy are undoubtedly associated with later disease-risk in the offspring. The placenta, interposed between the mother and the fetus, is a potential mediator of this risk through epigenetic mechanisms, including DNA methylation. In recent years, multiple studies have identified differentially methylated CpG sites in the placental tissue DNA in pregnancies complicated by diabetes and obesity. We reviewed all published original research relevant to this topic and analyzed our findings with the focus of identifying overlaps, contradictions and gaps. Most studies focused on the association of gestational diabetes and/or hyperglycemia in pregnancy and DNA methylation in placental tissue at term. We identified overlaps in results related to specific candidate genes, but also observed a large research gap of pregnancies affected by type 1 diabetes. Other unanswered questions relate to analysis of specific placental cell types and the timing of DNA methylation change in response to diabetes and obesity during pregnancy. Maternal metabolism is altered already in the first trimester involving structural and functional changes in the placenta, but studies into its effects on placental DNA methylation during this period are lacking and urgently needed. Fetal sex is also an important determinant of pregnancy outcome, but only few studies have taken this into account. Collectively, we provide a reference work for researchers working in this large and evolving field. Based on the results of the literature review, we formulate suggestions for future focus of placental DNA methylation studies in pregnancies complicated by diabetes and obesity.

The role of BMP4 signaling in trophoblast emergence from pluripotency

The Bone Morphogenetic Protein (BMP) signaling pathway has established roles in early embryonic morphogenesis, particularly in the epiblast. More recently, however, it has also been implicated in development of extraembryonic lineages, including trophectoderm (TE), in both mouse and human. In this review, we will provide an overview of this signaling pathway, with a focus on BMP4, and its role in emergence and development of TE in both early mouse and human embryogenesis. Subsequently, we will build on these in vivo data and discuss the utility of BMP4-based protocols for in vitro conversion of primed vs. naïve pluripotent stem cells (PSC) into trophoblast, and specifically into trophoblast stem cells (TSC). PSC-derived TSC could provide an abundant, reproducible, and ethically acceptable source of cells for modeling placental development.

Prenatal exposure to air pollution and the risk of eczema in childhood: a systematic review and meta-analysis

An increasing number of studies investigated the association between air pollution during pregnancy and the risk of eczema in offspring. However, no meta-analysis has confirmed the existence and size of their association to date. We systematically searched PubMed, Web of Science, Cochrane Library, and Embase databases to select the observational controlled studies published from the inception date to October 16, 2021. Quality evaluation was guided by the Newcastle-Ottawa Scale (NOS). Sensitivity analysis was applied to assess the impact of each included study on the combined effects, and publication bias was examined by Begg's tests and Egger's tests. A total of 12 articles involving 69,374 participants met our eligibility criteria. A significant association between the maternal exposure to NO₂ (per 10 μg/m³ increased) and childhood eczema was observed, with a pooled risk estimate of 1.13 (95% CI: 1.06-1.19), but no association was observed between exposure to PM₁₀, PM_2.5, and SO₂ and the risk of eczema in offspring. Besides, the effect of maternal NO₂ exposure on childhood eczema was significant in the first and second trimesters, but not in the third trimester. There was notable variability in geographic location (p = 0.037) and air pollutant concentration (p = 0.031) based on meta-regression. Our findings indicated that prenatal exposure to NO₂ was a risk factor for elevated risk of eczema in childhood, especially in the first and second trimesters. Further studies with larger sample sizes considering different constituents of air pollution and various exposure windows are needed to validate these associations.

Associations between antenatal maternal asthma status and placental DNA methylation

INTRODUCTION

Maternal asthma in pregnancy is associated with adverse perinatal and child health outcomes; however, mechanisms are poorly understood.

METHODS

The PRogramming of Intergenerational Stress Mechanisms (PRISM) prospective pregnancy cohort characterized asthma history during pregnancy via questionnaires and quantified placental DNAm using the Illumina Infinium HumanMethylation450 BeadChip. We performed epigenome-wide association analyses (n = 223) to estimate associations between maternal active or inactive asthma, as compared to never asthma, and placental differentially methylated positions (DMPs) and differentially variable positions (DVPs). Models adjusted for maternal pre-pregnancy body mass index, smoking status, parity, age and education level and child sex. P-values were FDR-adjusted.

RESULTS

One hundred and fifty-nine (71.3%) pregnant women reported no history of asthma (never asthma), 15 (6.7%) reported inactive, and 49 (22%) reported active antenatal asthma. Women predominantly self-identified as Black/Hispanic Black [88 (39.5%)] and Hispanic/non-Black [42 (18.8%)]. We identified 10 probes at FDR<0.05 and 4 probes at FDR<0.10 characterized by higher variability in maternal active asthma compared to never asthma mapping to GPX3, LHPP, PECAM1, ATAD3C, and ARHGEF4 and 2 probes characterized by lower variation mapping to CHMP4A and C5orf24. Amongst women with inactive asthma, we identified 52 probes, 41 at FDR<0.05 and an additional 11 at FDR <0.10, with higher variability compared to never asthma; BMP4, LHPP, PHYHIPL, and ZSCAN23 were associated with multiple DVPs. No associations were observed with DMPs.

DISCUSSION

We observed alterations in placental DNAm in women with antenatal asthma, as compared to women without a history of asthma. Further research is needed to understand the impact on fetal development.

Changes in gene expression in rat placenta at gestational day 16.5 in response to hyperglycemia

Gestational diabetes mellitus (GDM) is a serious pregnancy complication. Hyperglycemia induces abnormal placental development and function. However, the mechanism is unclear. Previous research showed streptozocin (STZ) injection sustained hyperglycemia throughout pregnancy in rodents. Our current results showed that the placenta from hyperglycemic STZ-treated rats was about 20% heavier than that of controls. The relative thickness of each layer of the placenta was also significantly different on gestational day (GD) 16.5. Gene expression was analyzed by RNA sequencing to explore reasons for the abnormal placenta. In total, 2100 differential expressed genes (DEGs), including 1327 up-regulated and 773 down-regulated genes, were identified. Gene ontogeny (GO) analysis revealed DEGs involved in developmental process, growth, metabolic process, cell junction, molecular transducer activity and signaling. By KEGG analysis, DEGs were mainly related to the endocrine system, development, signal transduction and cell growth and death. The KEGG results were partly consistent with GO results, with DEGs mainly focused on biochemical signal pathways such as cell growth and death (e.g., Abl1, Bbc3 and Camk2d), and signal transduction (e.g., Abl1, Ceacam1 and Arnt). These genes may play a dominant role in abnormal cell proliferation and signaling disorders. These results suggest that DEGs play a role in diabetic-induced placental abnormalities. One or more of these DEGs may be involved in the etiology of placental weight increase caused by hyperglycemia.

The impact of single-step and sequential embryo culture systems on obstetric and perinatal outcomes in singleton pregnancies: the Massachusetts Outcomes Study of Assisted Reproductive Technology

OBJECTIVE

To compare the obstetric and perinatal outcomes of deliveries conceived with embryos from single-step vs. sequential culture media systems.

DESIGN

Historical cohort of Massachusetts vital records linked to assisted reproductive technology clinic data from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System and laboratory embryology data from two large academic hospital fertility centers.

SETTING

Not applicable.

PATIENTS

Patients with singleton live birth deliveries between 2004 and 2017 conceived with autologous assisted reproductive technology cycles with fresh blastocyst transfer using either single-step (n = 1,058) or sequential (n = 474) culture media systems.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Associations of single-step vs. sequential culture with obstetric outcomes (mode of delivery, placental abnormalities, pregnancy-induced hypertension, and gestational diabetes) and perinatal outcomes (preterm birth, low birthweight, small-for-gestational-age, and large-for-gestational-age [LGA]) were assessed with multivariate logistic modeling, adjusted for maternal age, race/ethnicity, education, parity, insurance type, protein supplementation, oxygen concentration, fertilization method, and number of transferred embryos.

RESULTS

Compared with sequential culture, single-step culture was associated with increased odds of LGA (adjusted odds ratio 2.1, 95% confidence interval 1.04-4.22). There were no statistically significant differences between single-step and sequential culture media systems in the odds of placental abnormalities, pregnancy-induced hypertension, gestational diabetes, prematurity, small-for-gestational-age, or low birthweight.

CONCLUSIONS

Single-step culture is associated with increased odds of LGA, indicating that embryo culture media systems may affect perinatal outcomes.

Placental genomics mediates genetic associations with complex health traits and disease

As the master regulator in utero, the placenta is core to the Developmental Origins of Health and Disease (DOHaD) hypothesis but is historically understudied. To identify placental gene-trait associations (GTAs) across the life course, we perform distal mediator-enriched transcriptome-wide association studies (TWAS) for 40 traits, integrating placental multi-omics from the Extremely Low Gestational Age Newborn Study. At $$P \; < \; 2.5\times {10}^{-6}$$ P < 2.5 × 10 − 6 , we detect 248 GTAs, mostly for neonatal and metabolic traits, across 176 genes, enriched for cell growth and immunological pathways. In aggregate, genetic effects mediated by placental expression significantly explain 4 early-life traits but no later-in-life traits. 89 GTAs show significant mediation through distal genetic variants, identifying hypotheses for distal regulation of GTAs. Investigation of one hypothesis in human placenta-derived choriocarcinoma cells reveal that knockdown of mediator gene EPS15 upregulates predicted targets SPATA13 and FAM214A, both associated with waist-hip ratio in TWAS, and multiple genes involved in metabolic pathways. These results suggest profound health impacts of placental genomic regulation in developmental programming across the life course.

Reliability of a novel approach for reference-based cell type estimation in human placental DNA methylation studies

The placenta is a central organ during early development, influencing trajectories of health and disease. DNA methylation (DNAm) studies of human placenta improve our understanding of how its function relates to disease risk. However, DNAm studies can be biased by cell type heterogeneity, so it is essential to control for this in order to reduce confounding and increase precision. Computational cell type deconvolution approaches have proven to be very useful for this purpose. For human placenta, however, an assessment of the performance of these estimation methods is still lacking. Here, we examine the performance of a newly available reference-based cell type estimation approach and compare it to an often-used reference-free cell type estimation approach, namely RefFreeEWAS, in placental genome-wide DNAm samples taken at birth and from chorionic villus biopsies early in pregnancy using three independent studies comprising over 1000 samples. We found both reference-free and reference-based estimated cell type proportions to have predictive value for DNAm, however, reference-based cell type estimation outperformed reference-free estimation for the majority of data sets. Reference-based cell type estimations mirror previous histological knowledge on changes in cell type proportions through gestation. Further, CpGs whose variation in DNAm was largely explained by reference-based estimated cell type proportions were in the proximity of genes that are highly tissue-specific for placenta. This was not the case for reference-free estimated cell type proportions. We provide a list of these CpGs as a resource to help researchers to interpret results of existing studies and improve future DNAm studies of human placenta.

Sperm Histone H3 Lysine 4 tri-methylation serves as a metabolic sensor of paternal obesity and is associated with the inheritance of metabolic dysfunction

Objective

Parental environmental exposures can strongly influence descendant risks for adult disease. How paternal obesity changes the sperm chromatin leading to the acquisition of metabolic disease in offspring remains controversial and ill-defined. The objective of this study was to assess (1) whether obesity induced by a high-fat diet alters sperm histone methylation; (2) whether paternal obesity can induce metabolic disturbances across generations; (3) whether there could be cumulative damage to the sperm epigenome leading to enhanced metabolic dysfunction in descendants; and (4) whether obesity-sensitive regions associate with embryonic epigenetic and transcriptomic profiles. Using a genetic mouse model of epigenetic inheritance, we investigated the role of histone H3 lysine 4 methylation (H3K4me3) in the paternal transmission of metabolic dysfunction. This transgenic mouse overexpresses the histone demethylase enzyme KDM1A in the developing germline and has an altered sperm epigenome at the level of histone H3K4 methylation. We hypothesized that challenging transgenic sires with a high-fat diet would further erode the sperm epigenome and lead to enhanced metabolic disturbances in the next generations.

Methods

To assess whether paternal obesity can have inter- or transgenerational impacts, and if so to identify potential mechanisms of this non-genetic inheritance, we used wild-type C57BL/6NCrl and transgenic males with a pre-existing altered sperm epigenome. To induce obesity, sires were fed either a control or high-fat diet (10% or 60% kcal fat, respectively) for 10–12 weeks, then bred to wild-type C57BL/6NCrl females fed a regular diet. F₁ and F₂ descendants were characterized for metabolic phenotypes by examining the effects of paternal obesity by sex, on body weight, fat mass distribution, the liver transcriptome, intraperitoneal glucose, and insulin tolerance tests. To determine whether obesity altered the F₀ sperm chromatin, native chromatin immunoprecipitation-sequencing targeting H3K4me3 was performed. To gain insight into mechanisms of paternal transmission, we compared our sperm H3K4me3 profiles with embryonic and placental chromatin states, histone modification, and gene expression profiles.

Results

Obesity-induced alterations in H3K4me3 occurred in genes implicated in metabolic, inflammatory, and developmental processes. These processes were associated with offspring metabolic dysfunction and corresponded to genes enriched for H3K4me3 in embryos and overlapped embryonic and placenta gene expression profiles. Transgenerational susceptibility to metabolic disease was only observed when obese F₀ had a pre-existing modified sperm epigenome. This coincided with increased H3K4me3 alterations in sperm and more severe phenotypes affecting their offspring.

Conclusions

Our data suggest sperm H3K4me3 might serve as a metabolic sensor that connects paternal diet with offspring phenotypes via the placenta. This non-DNA-based knowledge of inheritance has the potential to improve our understanding of how environment shapes heritability and may lead to novel routes for the prevention of disease. This study highlights the need to further study the connection between the sperm epigenome, placental development, and children's health.

Summary sentence

Paternal obesity impacts sperm H3K4me3 and is associated with placenta, embryonic and metabolic outcomes in descendants.

•

Sperm H3K4me3 serves as a metabolic sensor of HFD-induced obesity.

•

Obesity-altered sperm H3K4me3 corresponds to embryonic transcription and chromatin profiles.

•

HFD- and KDM1A-induced cumulative sperm epimutations enhanced F₁ metabolic dysfunction.

•

Sperm epimutations may influence placenta function inducing F₁ metabolic phenotypes.

Placental Dysfunction in Assisted Reproductive Pregnancies: Perinatal, Neonatal and Adult Life Outcomes

Obstetric and newborn outcomes of assisted reproductive technology (ART) pregnancies are associated with significative prevalence of maternal and neonatal adverse health conditions, such as cardiovascular and metabolic diseases. These data are interpreted as anomalies in placentation involving a dysregulation of several molecular factors and pathways. It is not clear which extent of the observed placental alterations are the result of ART and which originate from infertility itself. These two aspects probably act synergically for the final obstetric risk. Data show that mechanisms of inappropriate trophoblast invasion and consequent altered vascular remodeling sustain several clinical conditions, leading to obstetric and perinatal risks often found in ART pregnancies, such as preeclampsia, fetal growth restriction and placenta previa or accreta. The roles of factors such as VEGF, GATA3, PIGF, sFLT-1, sEndoglin, EGFL7, melatonin and of ART conditions, such as short or long embryo cultures, trophectoderm biopsy, embryo cryopreservation, and supraphysiologic endometrium preparation, are discussed. Inflammatory local conditions and epigenetic influence on embryos of ART procedures are important research topics since they may have important consequences on obstetric risk. Prevention and treatment of these conditions represent new frontiers for clinicians and biologists involved in ART, and synergic actions with researchers at molecular levels are advocated.

Genome-Wide Placental Gene Methylations in Gestational Diabetes Mellitus, Fetal Growth and Metabolic Health Biomarkers in Cord Blood

Gestational diabetes mellitus (GDM) "program" an elevated risk of metabolic syndrome in the offspring. Epigenetic alterations are a suspected mechanism. GDM has been associated with placental DNA methylation changes in some epigenome-wide association studies. It remains unclear which genes or pathways are affected, and whether any placental differential gene methylations are correlated to fetal growth or circulating metabolic health biomarkers. In an epigenome-wide association study using the Infinium MethylationEPIC Beadchip, we sought to identify genome-wide placental differentially methylated genes and enriched pathways in GDM, and to assess the correlations with fetal growth and metabolic health biomarkers in cord blood. The study samples were 30 pairs of term placentas in GDM vs. euglycemic pregnancies (controls) matched by infant sex and gestational age at delivery in the Shanghai Birth Cohort. Cord blood metabolic health biomarkers included insulin, C-peptide, proinsulin, IGF-I, IGF-II, leptin and adiponectin. Adjusting for maternal age, pre-pregnancy BMI, parity, mode of delivery and placental cell type heterogeneity, 256 differentially methylated positions (DMPs,130 hypermethylated and 126 hypomethylated) were detected between GDM and control groups accounting for multiple tests with false discovery rate <0.05 and beta-value difference >0.05. WSCD2 was identified as a differentially methylated gene in both site- and region-level analyses. We validated 7 hypermethylated (CYP1A2, GFRA1, HDAC4, LIMS2, NAV3, PAX6, UPK1B) and 10 hypomethylated (DPP10, CPLX1, CSMD2, GPR133, NRXN1, PCSK9, PENK, PRDM16, PTPRN2, TNXB) genes reported in previous epigenome-wide association studies. We did not find any enriched pathway accounting for multiple tests. DMPs in 11 genes (CYP2D7P1, PCDHB15, ERG, SIRPB1, DKK2, RAPGEF5, CACNA2D4, PCSK9, TSNARE1, CADM2, KCNAB2) were correlated with birth weight (z score) accounting for multiple tests. There were no significant correlations between placental gene methylations and cord blood biomarkers. In conclusions, GDM was associated with DNA methylation changes in a number of placental genes, but these placental gene methylations were uncorrelated to the observed metabolic health biomarkers (fetal growth factors, leptin and adiponectin) in cord blood. We validated 17 differentially methylated placental genes in GDM, and identified 11 differentially methylated genes relevant to fetal growth.