Gene expression patterns in human placenta

The Molecular Biology of Placental Transport of Calcium to the Human Foetus

From fertilisation to delivery, calcium must be transported into and within the foetoplacental unit for intracellular signalling. This requires very rapid, precisely located Ca2+ transfers. In addition, from around the eighth week of gestation, increasing amounts of calcium must be routed directly from maternal blood to the foetus for bone mineralisation through a flow-through system, which does not impact the intracellular Ca2+ concentration. These different processes are mediated by numerous membrane-sited Ca2+ channels, transporters, and exchangers. Understanding the mechanisms is essential to direct interventions to optimise foetal development and postnatal bone health and to protect the mother and foetus from pre-eclampsia. Ethical issues limit the availability of human foetal tissue for study. Our insight into the processes of placental Ca2+ handling is advancing rapidly, enabled by developing genetic, analytical, and computer technology. Because of their diverse sources, the reports of new findings are scattered. This review aims to pull the data together and to highlight areas of uncertainty. Areas needing clarification include trafficking, membrane expression, and recycling of channels and transporters in the placental microvilli; placental metabolism of vitamin D in gestational diabetes and pre-eclampsia; and the vascular effects of increased endothelial Orai expression by pregnancy-specific beta-1-glycoproteins PSG1 and PSG9.

Integrated proteomic and transcriptomic landscape of human placenta in small for gestational age infants

Small for gestational age (SGA) infants affected by placental insufficiency are exposed to the risk of stillbirth and long-term complications. Based on RNA-seq and mass spectrometry, we identified dysregulated RNAs and proteins from the comparisons of SGA placental tissues and controls. We revealed two SGA-relevant co-expression modules (SRMs) that also significantly distinguished SGA from controls. Then we performed an integrated analysis of transcriptomic and proteomic profiles to trace their links to SGA as well as their significant correlations. For the core functional molecules we screened, we revealed their potential upstream regulators and validated them experimentally in an independent cohort. Overall, we pointed out insights into different molecular pathways for the pathological mechanisms of SGA and indicated potential target molecules that may be drivers of placental aberrations in the SGA infants.

The central role of creatine and polyamines in fetal growth restriction

Placental insufficiency often correlates with fetal growth restriction (FGR), a condition that has both short- and long-term effects on the health of the newborn. In our study, we analyzed placental tissue from infants with FGR and from infants classified as small for gestational age (SGA) or appropriate for gestational age (AGA), performing comprehensive analyses that included transcriptomics and metabolomics. By examining villus tissue biopsies and 3D trophoblast organoids, we identified significant metabolic changes in placentas associated with FGR. These changes include adaptations to reduced oxygen levels and modifications in arginine metabolism, particularly within the polyamine and creatine phosphate synthesis pathways. Specifically, we found that placentas with FGR utilize arginine to produce phosphocreatine, a crucial energy reservoir for ATP production that is essential for maintaining trophoblast function. In addition, we found polyamine insufficiency in FGR placentas due to increased SAT1 expression. SAT1 facilitates the acetylation and subsequent elimination of spermine and spermidine from trophoblasts, resulting in a deficit of polyamines that cannot be compensated by arginine or polyamine supplementation alone, unless SAT1 expression is suppressed. Our study contributes significantly to the understanding of metabolic adaptations associated with placental dysfunction and provides valuable insights into potential therapeutic opportunities for the future.

Sexual dimorphism in lipidomic changes in maternal blood and placenta associated with obesity and gestational diabetes: A discovery study

INTRODUCTION

The placenta uses lipids and other nutrients to support its own metabolism hence impacting the type and amount of these substrates available to the growing fetus. Maternal obesity and gestational diabetes (GDM) can disrupt placental lipid metabolism and thus lead to altered fetal growth contributing to adverse pregnancy outcomes and developmentally programing the offspring for disease in later life. Understanding obesity and GDM driven changes in placental lipid metabolism is thus important.

METHODS

We collected maternal plasma and placental villous tissue following elective cesarean section at term from women who were lean (pre-pregnancy BMI 18.5-24.9), obese (BMI>30) or obese with type A2 GDM n = 8 each group (4 male and 4 female placentas). Fatty acid composition of different lipid classes was analyzed by LC-MS/MS analysis. Significant changes in GDM vs obese, GDM vs lean, and obese vs lean were determined in both a fetal sex-dependent and independent manner.

RESULTS

In placenta 436 lipids were identified, among which 85 showed significant changes. We report significant changes in placental triglyceride, phosphatidylcholine, and phosphatidylinositol lipids containing essential fatty acids- DHA and AA in GDM, with male placentas driving these changes. In maternal plasma, 284 lipids were identified with 14 showing significant changes, but we observed no changes based on fetal sex.

DISCUSSION

Maternal obesity and GDM impact placental lipid composition in a sexually dimorphic manner. The alteration in specific lipid classes can impact cellular energetics and placental function.

Single-cell and spatial transcriptomics: Discovery of human placental development and disease

The human placenta is a vital organ, encompassing many distinct cell types, that maintains the growth and development of the fetus and is essential for substance exchange, defense, synthesis, and immunity. Abnormalities in placental cells can lead to various pregnancy complications, but the mechanisms remain largely unclear. Single-cell and spatial transcriptomics technologies have been developed in recent years to demonstrate placental cell heterogeneity and spatial molecular localization. Here, we review and summarize the current literature, demonstrating these technologies and showing the heterogeneity of various placenta cells and cell-cell communication of normal human placenta, as well as placenta-related diseases, such as preeclampsia, gestational diabetes mellitus, advanced maternal age, recurrent pregnancy loss, and placenta accreta spectrum disorders. Meanwhile, current weaknesses and future direction were discussed.

Maternal stress during pregnancy alters circulating small extracellular vesicles and enhances their targeting to the placenta and fetus

BACKGROUND

Maternal psychological distress during pregnancy can negatively impact fetal development, resulting in long-lasting consequences for the offspring. These effects show a sex bias. The mechanisms whereby prenatal stress induces functional and/or structural changes in the placental-fetal unit remain poorly understood. Maternal circulating small extracellular vesicles (sEVs) are good candidates to act as "stress signals" in mother-to-fetus communication. Using a repetitive restraint-based rat model of prenatal stress, we examined circulating maternal sEVs under stress conditions and tested whether they could target placental-fetal tissues.

RESULTS

Our mild chronic maternal stress during pregnancy paradigm induced anhedonic-like behavior in pregnant dams and led to intrauterine growth restriction (IUGR), particularly in male fetuses and placentas. The concentration and cargo of maternal circulating sEVs changed under stress conditions. Specifically, there was a significant reduction in neuron-enriched proteins and a significant increase in astrocyte-enriched proteins in blood-borne sEVs from stressed dams. To study the effect of repetitive restraint stress on the biodistribution of maternal circulating sEVs in the fetoplacental unit, sEVs from pregnant dams exposed to stress or control protocol were labeled with DiR fluorescent die and injected into pregnant females previously exposed to control or stress protocol. Remarkably, maternal circulating sEVs target placental/fetal tissues and, under stress conditions, fetal tissues are more receptive to sEVs.

CONCLUSION

Our results suggest that maternal circulating sEVs can act as novel mediators/modulators of mother-to-fetus stress communication. Further studies are needed to identify placental/fetal cellular targets of maternal sEVs and characterize their contribution to stress-induced sex-specific placental and fetal changes.

The Implications of a "Flat" Oral Glucose Tolerance Test Curve in Pregnancy

OBJECTIVE

 This study aimed to determine whether pregnant women who have "flat" oral glucose tolerance test (OGTT) curves in pregnancy are at increased risk of maternal or neonatal adverse outcomes.

STUDY DESIGN

 We conducted a retrospective cohort study of the perinatal outcomes of pregnant women whose 100-g OGTT curve was "flat," defined by a fasting serum glucose level below 95 mg/dL and the remaining values below 100 mg/dL. We compared their perinatal outcomes to women whose OGTT curve was "normal." The primary outcomes compared were the prevalence of macrosomic and small for gestational age (SGA) neonates. Secondary outcomes included hypertensive disorders of pregnancy (HDP), prelabor anemia, thrombocytopenia, intrauterine fetal demise, placental abruption, indicated induction of labor, meconium-stained amniotic fluid, mode of delivery, postpartum hemorrhage, blood product transfusion, postpartum readmission, neonatal gender, gestational age at delivery, preterm birth, birth weight, low birth weight, umbilical artery pH < 7.1, Apgar score <7 at 5 minutes, neonatal intensive care unit admission, neonatal respiratory and infectious morbidity, and hypoglycemia. Composite adverse maternal and neonatal outcomes were also evaluated.

RESULTS

 There were 1,060 patients in the study group and 10,591 patients in the control group. Patients with a flat OGTT were younger (28.3 vs. 29.8, p < 0.001) and less likely to be over 35 years old (14.1 vs. 23.4%, p < 0.001). They had a reduced risk of delivering a macrosomic neonate (11.4 vs. 15.1%, OR = 0.7 [0.58-0.89], p = 0.001) and having an unplanned cesarean delivery (7.5 vs. 10.2%, OR = 0.8 [0.58-0.96], p = 0.002). There was no difference in the rate of composite adverse maternal (14.0 vs. 15.4%, OR = 0.9 [0.7-1.0], p = 0.1) or neonatal outcome (5.3 vs. 4.5%, OR = 1.2 [0.9-1.5], p = 0.15). Neonates had a slightly lower mean birth weight (3,474 vs. 3,505 g, p = 0.04) but the rate of SGA was similar in the two groups (2.5 vs. 1.8%, OR = 1.3 [0.9-2.0], p = 0.08).

CONCLUSION

 Pregnant women whose OGTT curve is flat have a lower risk of delivering macrosomic neonates and undergoing unplanned cesarean delivery and are not at increased risk of adverse maternal or neonatal outcomes. More research is required to evaluate the relationship between different OGTT curves and the fetal growth rate.

KEY POINTS

· Patients with a "flat" OGTT have a reduced risk of macrosomia.. · Patients with a "flat" OGTT have a reduced risk of cesarean delivery.. · Patients with a "flat" OGTT are not at increased risk of growth restriction..

Intrauterine Shaping of Fetal Microbiota

Mechanisms resulting from the physiological immaturity of the digestive system in children delivered before 32 weeks of gestation and, in particular, different interactions between the microbiome and the body have not been fully elucidated yet. Next-generation sequencing methods demonstrated the presence of bacterial DNA in the placenta and amniotic fluid, which may reflect bacterial populations that initiate intestinal colonization in utero. Numerous studies confirmed the hypothesis stating that intestinal bacteria played an important role in the pathogenesis of necrotizing enterocolitis (NEC) early- and late-onset neonatal sepsis (EONS and LONS). The model and scale of disorders within the intestinal microbiome are the subject of active research in premature infants. Neonatal meconium was primarily used as an indicator defining the environment in utero, as it is formed before birth. Metagenomic results and previous data from microbiological bacterial cultures showed a correlation between the time from birth to sample collection and the detection of bacteria in the neonatal meconium. Therefore, it may be determined that the colonization of the newborn's intestines is influenced by numerous factors, which may be divided into prenatal, perinatal, and postnatal, with particular emphasis put on the mode of delivery and contact with the parent immediately after birth. Background: The aim of this review was to collect available data on the intrauterine shaping of the fetal microbiota. Methods: On 13 March 2024, the available literature in the PubMed National Library of Medicine search engine was reviewed using the following selected keywords: "placental microbiome", "intestinal bacteria in newborns and premature infants", and "intrauterine microbiota". Results: After reviewing the available articles and abstracts and an in-depth analysis of their content, over 100 articles were selected for detailed elaboration. We focused on the origin of microorganisms shaping the microbiota of newborns. We also described the types of bacteria that made up the intrauterine microbiota and the intestinal microbiota of newborns. Conclusions: The data presented in the review on the microbiome of both term newborns and those with a body weight below 1200 g indicate a possible intrauterine colonization of the fetus depending on the duration of pregnancy. The colonization occurs both via the vaginal and intestinal route (hematogenous route). However, there are differences in the demonstrated representatives of various types of bacteria, phyla Firmicutes and Actinobacteria in particular, taking account of the distribution in their abundance in the individual groups of pregnancy duration. Simultaneously, the distribution of the phyla Actinobacteria and Proteobacteria is consistent. Considering the duration of pregnancy, it may also be concluded that the bacterial flora of vaginal origin dominates in preterm newborns, while the flora of intestinal origin dominates in term newborns. This might explain the role of bacterial and infectious factors in inducing premature birth with the rupture of fetal membranes.

Potential Roles of the GRF Transcription Factors in Sorghum Internodes during Post-Reproductive Stages

Growth-regulating factor (GRF) is a plant-specific family of transcription factors crucial for meristem development and plant growth. Sorghum (Sorghum bicolor L. Moench) is a cereal species widely used for food, feed and fuel. While sorghum stems are important biomass components, the regulation of stem development and the carbohydrate composition of the stem tissues remain largely unknown. Here, we identified 11 SbGRF-encoding genes and found the SbGRF expansion driven by whole-genome duplication events. By comparative analyses of GRFs between rice and sorghum, we demonstrated the divergence of whole-genome duplication (WGD)-derived OsGRFs and SbGRFs. A comparison of SbGRFs' expression profiles supports that the WGD-duplicated OsGRFs and SbGRFs experienced distinct evolutionary trajectories, possibly leading to diverged functions. RNA-seq analysis of the internode tissues identified several SbGRFs involved in internode elongation, maturation and cell wall metabolism. We constructed co-expression networks with the RNA-seq data of sorghum internodes. Network analysis discovered that SbGRF1, 5 and 7 could be involved in the down-regulation of the biosynthesis of cell wall components, while SbGRF4, 6, 8 and 9 could be associated with the regulation of cell wall loosening, reassembly and/or starch biosynthesis. In summary, our genome-wide analysis of SbGRFs reveals the distinct evolutionary trajectories of WGD-derived SbGRF pairs. Importantly, expression analyses highlight previously unknown functions of several SbGRFs in internode elongation, maturation and the potential involvement in the metabolism of the cell wall and starch during post-anthesis stages.

Changes in maternal blood and placental lipidomic profile in obesity and gestational diabetes: Evidence for sexual dimorphism

Introduction

Obesity and gestational diabetes (GDM) are associated with adverse pregnancy outcomes and program the offspring for cardiometabolic disease in a sexually dimorphic manner. The placenta transfers lipids to the fetus and uses these substrates to support its own metabolism impacting the amount of substrate available to the growing fetus.

Methods

We collected maternal plasma and placental villous tissue following elective cesarean section at term from women who were lean (pre-pregnancy BMI 18.5-24.9), obese (BMI>30) and type A2 GDM (matched to obese BMI) with male or female fetus (n=4 each group). Lipids were extracted and fatty acid composition of different lipid classes were analyzed by LC-MS/MS analysis. Significant changes in GDM vs obese, GDM vs lean, and obese vs lean were determined using t-test with a Tukey correction set at p<0.05.

Results

In placental samples 436 lipids were identified, among which 85 showed significant changes. Of note only in male placentas significant decreases in C22:6 - docosahexaenoic acid (DHA) in phosphatidylcholine (PC) and triglyceride lipid species were seen when comparing tissue from GDM women to lean. In maternal plasma we observed no effect of obesity. GDM or fetal sex.

Conclusion

This is the first study assessing fatty acid composition of lipids in matched maternal plasma and placental tissue from lean, obese, and GDM women stratified by fetal sex. It highlights how GDM affects distribution of fatty acids in lipid classes changes in a sexually dimorphic manner in the placenta.

Revealing the molecular landscape of human placenta: a systematic review and meta-analysis of single-cell RNA sequencing studies

BACKGROUND

With increasing significance of developmental programming effects associated with placental dysfunction, more investigations are devoted to improving the characterization and understanding of placental signatures in health and disease. The placenta is a transitory but dynamic organ adapting to the shifting demands of fetal development and available resources of the maternal supply throughout pregnancy. Trophoblasts (cytotrophoblasts, syncytiotrophoblasts, and extravillous trophoblasts) are placental-specific cell types responsible for the main placental exchanges and adaptations. Transcriptomic studies with single-cell resolution have led to advances in understanding the placenta's role in health and disease. These studies, however, often show discrepancies in characterization of the different placental cell types.

OBJECTIVE AND RATIONALE

We aim to review the knowledge regarding placental structure and function gained from the use of single-cell RNA sequencing (scRNAseq), followed by comparing cell-type-specific genes, highlighting their similarities and differences. Moreover, we intend to identify consensus marker genes for the various trophoblast cell types across studies. Finally, we will discuss the contributions and potential applications of scRNAseq in studying pregnancy-related diseases.

SEARCH METHODS

We conducted a comprehensive systematic literature review to identify different cell types and their functions at the human maternal-fetal interface, focusing on all original scRNAseq studies on placentas published before March 2023 and published reviews (total of 28 studies identified) using PubMed search. Our approach involved curating cell types and subtypes that had previously been defined using scRNAseq and comparing the genes used as markers or identified as potential new markers. Next, we reanalyzed expression matrices from the six available scRNAseq raw datasets with cell annotations (four from first trimester and two at term), using Wilcoxon rank-sum tests to compare gene expression among studies and annotate trophoblast cell markers in both first trimester and term placentas. Furthermore, we integrated scRNAseq raw data available from 18 healthy first trimester and nine term placentas, and performed clustering and differential gene expression analysis. We further compared markers obtained with the analysis of annotated and raw datasets with the literature to obtain a common signature gene list for major placental cell types.

OUTCOMES

Variations in the sampling site, gestational age, fetal sex, and subsequent sequencing and analysis methods were observed between the studies. Although their proportions varied, the three trophoblast types were consistently identified across all scRNAseq studies, unlike other non-trophoblast cell types. Notably, no marker genes were shared by all studies for any of the investigated cell types. Moreover, most of the newly defined markers in one study were not observed in other studies. These discrepancies were confirmed by our analysis on trophoblast cell types, where hundreds of potential marker genes were identified in each study but with little overlap across studies. From 35 461 and 23 378 cells of high quality in the first trimester and term placentas, respectively, we obtained major placental cell types, including perivascular cells that previously had not been identified in the first trimester. Importantly, our meta-analysis provides marker genes for major placental cell types based on our extensive curation.

WIDER IMPLICATIONS

This review and meta-analysis emphasizes the need for establishing a consensus for annotating placental cell types from scRNAseq data. The marker genes identified here can be deployed for defining human placental cell types, thereby facilitating and improving the reproducibility of trophoblast cell annotation.

Sex-biased regulatory changes in the placenta of native highlanders contribute to adaptive fetal development

Compared with lowlander migrants, native Tibetans have a higher reproductive success at high altitude though the underlying mechanism remains unclear. Here, we compared the transcriptome and histology of full-term placentas between native Tibetans and Han migrants. We found that the placental trophoblast shows the largest expression divergence between Tibetans and Han, and Tibetans show decreased immune response and endoplasmic reticulum stress. Remarkably, we detected a sex-biased expression divergence, where the male-infant placentas show a greater between-population difference than the female-infant placentas. The umbilical cord plays a key role in the sex-biased expression divergence, which is associated with the higher birth weight of the male newborns of Tibetans. We also identified adaptive histological changes in the male-infant placentas of Tibetans, including larger umbilical artery wall and umbilical artery intima and media, and fewer syncytial knots. These findings provide valuable insights into the sex-biased adaptation of human populations, with significant implications for medical and genetic studies of human reproduction.

Maternal obesity and placental function: impaired maternal-fetal axis

The prevalence of maternal obesity rapidly increases, which represents a major public health concern worldwide. Maternal obesity is characteristic by metabolic dysfunction and chronic inflammation. It is associated with health problems in both mother and offspring. Increasing evidence indicates that the placenta is an axis connecting maternal obesity with poor outcomes in the offspring. In this brief review, we have summarized the current data regarding deregulated placental function in maternal obesity. The data show that maternal obesity induces numerous placental defects, including lipid and glucose metabolism, stress response, inflammation, immune regulation and epigenetics. These placental defects affect each other and result in a stressful intrauterine environment, which transduces and mediates the adverse effects of maternal obesity to the fetus. Further investigations are required to explore the exact molecular alterations in the placenta in maternal obesity, which may pave the way to develop specific interventions for preventing epigenetic and metabolic programming in the fetus.

FGR-associated placental insufficiency and capillary angiogenesis involves disruptions in human placental miRNAs and mRNAs

Fetal growth restriction (FGR) is one of the most common pregnancy complications culminating in adverse fetal outcome, including preterm birth, neonatal mortality and stillbirth. Compromised placental development and function, especially disruption in angiogenesis and inadequate nutrient supply are contributing factors. Fetal sex also influences placental function. Knowledge of gene expression changes and epigenetic factors contributing to placental dysfunction in FGR pregnancies will help identify biomarkers and help target interventions. This study tested the hypothesis that FGR pregnancies are associated with disruptions in miRNA - an epigenetic factor and mRNAs involving key mediators of angiogenesis and microvessel development. Changes in expression of key genes/proteins involved in placental dysfunction by RT-PCR and immunohistochemistry and miRNA changes by RNA sequencing were undertaken with term placenta from 12 control and 20 FGR pregnancies. Findings showed changes in expression of genes involved in steroidogenesis, steroid action, IGF family members, inflammatory cytokines and angiogenic factors in FGR pregnancies. In addition, upregulation of MIR451A and downregulation of MIR543 in placentas from FGR group with female newborns and upregulation of MIR520G in placentas from FGR group with male newborns were also noted. MIR451A and MIR543 have been implicated in angiogenesis. Consistent with gene changes, CD34, the microvessel angiogenesis marker, also showed reduced staining only in female FGR group. These findings provide evidence that epigentically regulated gene expression changes in angiogenesis and capillary development influence placental impairment in FGR pregnancies. Our preliminary observations also support for these changes to be driven in a sex-specific manner.

Differential gene expression in two consecutive pregnancies between same sex siblings and implications on maternal constraint

The objective of this study was to investigate how placental gene expression differs in two consecutive pregnancies in same sex siblings, and its possible association with the "maternal constraint" hypothesis. Material was gathered from the BASIC study (Biological, Affect, Stress, Imaging, and Cognition in Pregnancy and the Puerperium), a population based prospective study that was started in 2009 in Uppsala. Over 900 specimens of placenta biopsies were collected and out of these 10 women gave birth twice, to the same sex child, and were included in this study. The total RNA was isolated and prepared from frozen villous tissue from the placenta and further analyzed by use of Ion AmpliSeq Human Transcriptome Gene Expression kit. A total of 234 genes differed significantly between the first and second pregnancy placentas, when adjusting for delivery mode, maternal BMI and gestational age. Of special interest was the down-regulated group of genes in the second pregnancy. Exemplified by Pentraxin 3, SRY-Box Transcription Factor 9, and Serum Amyloid A1, which all were associated with biological processes involved in the immune system and inflammation. Further, protein-protein interaction analysis visualized them as hub genes interacting with several of the other differentially expressed genes. How these altered gene expressions affect maternal constraint during pregnancy needs further validation in lager study cohorts and also future validation in functional assays.

Sex differences in growth and mortality in pregnancy-associated hypertension

BACKGROUND

It is hypothesized that male fetuses prioritize growth, resulting in increased mortality, whereas females reduce growth in the presence of adversity. Preeclampsia reflects a chronic condition, in which fetuses have the opportunity to adjust growth. If females reduce their growth in response to preeclampsia, but males attempt to maintain growth at the cost of survival, we predict that differences in birthweight between preeclamptic and non-preeclamptic pregnancies will be greater among females, whereas differences in mortality will be greater among males.

METHODS

We analysed data from the Centers for Disease Control and Prevention. We compared pregnancies with pregnancy-associated hypertension (PAH) and controls.

RESULTS

The difference in birthweight between pregnancies affected by PAH and controls varied by fetal sex and gestational age. Among pregnancies of White individuals, at 34-35 weeks, the difference between PAH and controls was higher among females, as predicted. However, this pattern was reversed earlier in pregnancy and around term. Such variation was not significant in Black pregnancies. In both Black and White pregnancies, early in gestation, males had lower odds of death in PAH pregnancies, but higher odds of death in control pregnancies, counter to our prediction. Later, males had higher odds of death in PAH and controls, although the increased odds of death in males was not higher in PAH pregnancies than in controls. Overall, the difference in birthweight between surviving and non-surviving infants was greater in males than in females, opposite to our prediction.

CONCLUSIONS

The impact of PAH on birthweight and survival varies widely throughout gestation. Differences in birthweight and survival between male and female PAH and controls are generally not consistent with the hypothesis that males prioritize fetal growth more than females, and that this is a cause of increased mortality in males.

Sex-based disparities in DNA methylation and gene expression in late-gestation mouse placentas

BACKGROUND

The placenta is vital for fetal development and its contributions to various developmental issues, such as pregnancy complications, fetal growth restriction, and maternal exposure, have been extensively studied in mice. The placenta forms mainly from fetal tissue and therefore has the same biological sex as the fetus it supports. Extensive research has delved into the placenta's involvement in pregnancy complications and future offspring development, with a notable emphasis on exploring sex-specific disparities. However, despite these investigations, sex-based disparities in epigenetic (e.g., DNA methylation) and transcriptomic features of the late-gestation mouse placenta remain largely unknown.

METHODS

We collected male and female mouse placentas at late gestation (E18.5, n = 3/sex) and performed next-generation sequencing to identify genome-wide sex differences in transcription and DNA methylation.

RESULTS

Our comparison between male and female revealed 358 differentially expressed genes (DEGs) on autosomes, which were associated with signaling pathways involved in transmembrane transport and the responses to viruses and external stimuli. X chromosome DEGs (n = 39) were associated with different pathways, including those regulating chromatin modification and small GTPase-mediated signal transduction. Differentially methylated regions (DMRs) were more common on the X chromosomes (n = 3756) than on autosomes (n = 1705). Interestingly, while most X chromosome DMRs had higher DNA methylation levels in female placentas and tended to be included in CpG dinucleotide-rich regions, 73% of autosomal DMRs had higher methylation levels in male placentas and were distant from CpG-rich regions. Several DEGs were correlated with DMRs. A subset of the DMRs present in late-stage placentas were already established in mid-gestation (E10.5) placentas (n = 348 DMRs on X chromosome and 19 DMRs on autosomes), while others were acquired later in placental development.

CONCLUSION

Our study provides comprehensive lists of DEGs and DMRs between male and female that collectively cause profound differences in the DNA methylation and gene expression profiles of late-gestation mouse placentas. Our results demonstrate the importance of incorporating sex-specific analyses into epigenetic and transcription studies to enhance the accuracy and comprehensiveness of their conclusions and help address the significant knowledge gap regarding how sex differences influence placental function.

Genome-wide identification of transcriptional enhancers during human placental development and association with function, differentiation, and disease†

The placenta is a dynamic organ that must perform a remarkable variety of functions during its relatively short existence in order to support a developing fetus. These functions include nutrient delivery, gas exchange, waste removal, hormone production, and immune barrier protection. Proper placenta development and function are critical for healthy pregnancy outcomes, but the underlying genomic regulatory events that control this process remain largely unknown. We hypothesized that mapping sites of transcriptional enhancer activity and associated changes in gene expression across gestation in human placenta tissue would identify genomic loci and predicted transcription factor activity related to critical placenta functions. We used a suite of genomic assays [i.e., RNA-sequencing (RNA-seq), Precision run-on-sequencing (PRO-seq), and Chromatin immunoprecipitation-sequencing (ChIP-seq)] and computational pipelines to identify a set of >20 000 enhancers that are active at various time points in gestation. Changes in the activity of these enhancers correlate with changes in gene expression. In addition, some of these enhancers encode risk for adverse pregnancy outcomes. We further show that integrating enhancer activity, transcription factor motif analysis, and transcription factor expression can identify distinct sets of transcription factors predicted to be more active either in early pregnancy or at term. Knockdown of selected identified transcription factors in a trophoblast stem cell culture model altered the expression of key placental marker genes. These observations provide a framework for future mechanistic studies of individual enhancer-transcription factor-target gene interactions and have the potential to inform genetic risk prediction for adverse pregnancy outcomes.

Labour and premature delivery differentially affect the expression of the endocannabinoid system in the human placenta

Plasma concentrations of N-arachidonyletholamine (AEA), N-oleoylethanolamide (OEA) and N-palmitoylethanolamide (PEA) increase at term and can predict when a woman is likely to go into labour. We hypothesised that increased plasma AEA concentrations in women in preterm and term labour might also be increased and have a function in the placenta at the end of pregnancy. Here we examined the expression of the N-acylethanolamine-modulating enzymes fatty acid amide hydrolase (FAAH) and N-acyl-phosphatidylethanolamine-specific phospholipase-D (NAPE-PLD) and of the cannabinoid receptors (CB1 and CB2) in the placenta and their activation in an in vitro model of the third-trimester placenta to determine if those expressions change with labour and have functional significance. Expression of CB1, CB2, FAAH and NAPE-PLD was examined by immunohistochemistry (IHC) and RT-qPCR in placental samples obtained from four patient groups: preterm not in labour (PTNL), term not in labour (TNL), preterm in labour (PTL) and term in labour (TL). Additionally, the effects of AEA on a third-trimester human cell line (TCL-1) were evaluated. All ECS components were present in the third-trimester placenta, with NAPE-PLD and CB2 being the key modulated proteins in terms of expression. Functionally, AEA reduced TCL-1 cell numbers through the actions of the CB2 receptor whilst CB1 maintained placental integrity through the expression of the transcription regulators histone deacetylase 3, thyroid hormone receptor β 1 and the modulation of 5α reductase type 1. The placenta in the third trimester and at term is different from the placenta in the first trimester with respect to the expression of CB1, CB2, FAAH and NAPE-PLD, and the expression of these proteins is affected by labour. These data suggest that early perturbation of some ECS components in the placenta may cause AEA-induced PTL and thus PTB.

Sex-based differences in placental DNA methylation profiles related to gestational age: an NIH ECHO meta-analysis

The placenta undergoes many changes throughout gestation to support the evolving needs of the foetus. There is also a growing appreciation that male and female foetuses develop differently in utero, with unique epigenetic changes in placental tissue. Here, we report meta-analysed sex-specific associations between gestational age and placental DNA methylation from four cohorts in the National Institutes of Health (NIH) Environmental influences on Child Health Outcomes (ECHO) Programme (355 females/419 males, gestational ages 23-42 weeks). We identified 407 cytosine-guanine dinucleotides (CpGs) in females and 794 in males where placental methylation levels were associated with gestational age. After cell-type adjustment, 55 CpGs in females and 826 in males were significant. These were enriched for biological processes critical to the immune system in females and transmembrane transport in males. Our findings are distinct between the sexes: in females, associations with gestational age are largely explained by differences in placental cellular composition, whereas in males, gestational age is directly associated with numerous alterations in methylation levels.

The Proteome Landscape of Human Placentas for Monochorionic Twins with Selective Intrauterine Growth Restriction

In perinatal medicine, intrauterine growth restriction (IUGR) is one of the greatest challenges. The etiology of IUGR is multifactorial, but most cases are thought to arise from placental insufficiency. However, identifying the placental cause of IUGR can be difficult due to numerous confounding factors. Selective IUGR (sIUGR) would be a good model to investigate how impaired placentation affects fetal development, as the growth discordance between monochorionic twins cannot be explained by confounding genetic or maternal factors. Herein, we constructed and analyzed the placental proteomic profiles of IUGR twins and normal cotwins. Specifically, we identified a total of 5481 proteins, of which 233 were differentially expressed (57 up-regulated and 176 down-regulated) in IUGR twins. Bioinformatics analysis indicates that these differentially expressed proteins (DEPs) are mainly associated with cardiovascular system development and function, organismal survival, and organismal development. Notably, 34 DEPs are significantly enriched in angiogenesis, and diminished placental angiogenesis in IUGR twins has been further elaborately confirmed. Moreover, we found decreased expression of metadherin (MTDH) in the placentas of IUGR twins and demonstrated that MTDH contributes to placental angiogenesis and fetal growth in vitro. Collectively, our findings reveal the comprehensive proteomic signatures of placentas for sIUGR twins, and the DEPs identified may provide in-depth insights into the pathogenesis of placental dysfunction and subsequent impaired fetal growth.

Unlocking the potential of RNA-based therapeutics in the lung: current status and future directions

Awareness of RNA-based therapies has increased after the widespread adoption of mRNA vaccines against SARS-CoV-2 during the COVID-19 pandemic. These mRNA vaccines had a significant impact on reducing lung disease and mortality. They highlighted the potential for rapid development of RNA-based therapies and advances in nanoparticle delivery systems. Along with the rapid advancement in RNA biology, including the description of noncoding RNAs as major products of the genome, this success presents an opportunity to highlight the potential of RNA as a therapeutic modality. Here, we review the expanding compendium of RNA-based therapies, their mechanisms of action and examples of application in the lung. The airways provide a convenient conduit for drug delivery to the lungs with decreased systemic exposure. This review will also describe other delivery methods, including local delivery to the pleura and delivery vehicles that can target the lung after systemic administration, each providing access options that are advantageous for a specific application. We present clinical trials of RNA-based therapy in lung disease and potential areas for future directions. This review aims to provide an overview that will bring together researchers and clinicians to advance this burgeoning field.

Sex difference of pre- and post-natal exposure to six developmental neurotoxicants on intellectual abilities: a systematic review and meta-analysis of human studies

BACKGROUND

Early life exposure to lead, mercury, polychlorinated biphenyls (PCBs), polybromide diphenyl ethers (PBDEs), organophosphate pesticides (OPPs), and phthalates have been associated with lowered IQ in children. In some studies, these neurotoxicants impact males and females differently. We aimed to examine the sex-specific effects of exposure to developmental neurotoxicants on intelligence (IQ) in a systematic review and meta-analysis.

METHOD

We screened abstracts published in PsychINFO and PubMed before December 31st, 2021, for empirical studies of six neurotoxicants (lead, mercury, PCBs, PBDEs, OPPs, and phthalates) that (1) used an individualized biomarker; (2) measured exposure during the prenatal period or before age six; and (3) provided effect estimates on general, nonverbal, and/or verbal IQ by sex. We assessed each study for risk of bias and evaluated the certainty of the evidence using Navigation Guide. We performed separate random effect meta-analyses by sex and timing of exposure with subgroup analyses by neurotoxicant.

RESULTS

Fifty-one studies were included in the systematic review and 20 in the meta-analysis. Prenatal exposure to developmental neurotoxicants was associated with decreased general and nonverbal IQ in males, especially for lead. No significant effects were found for verbal IQ, or postnatal lead exposure and general IQ. Due to the limited number of studies, we were unable to analyze postnatal effects of any of the other neurotoxicants.

CONCLUSION

During fetal development, males may be more vulnerable than females to general and nonverbal intellectual deficits from neurotoxic exposures, especially from lead. More research is needed to examine the nuanced sex-specific effects found for postnatal exposure to toxic chemicals.

A Critical Review on the Opportunity to Use Placenta and Innovative Biomonitoring Methods to Characterize the Prenatal Chemical Exposome

Adverse effects associated with chemical exposures during pregnancy include several developmental and reproductive disorders. However, considering the tens of thousands of chemicals present on the market, the effects of chemical mixtures on the developing fetus is still likely underestimated. In this critical review, we discuss the potential to apply innovative biomonitoring methods using high-resolution mass spectrometry (HRMS) on placenta to improve the monitoring of chemical exposure during pregnancy. The physiology of the placenta and its relevance as a matrix for monitoring chemical exposures and their effects on fetal health is first outlined. We then identify several key parameters that require further investigations before placenta can be used for large-scale monitoring in a robust manner. Most critical is the need for standardization of placental sampling. Placenta is a highly heterogeneous organ, and knowledge of the intraplacenta variability of chemical composition is required to ensure unbiased and robust interindividual comparisons. Other important variables include the time of collection, the sex of the fetus, and mode of delivery. Finally, we discuss the first applications of HRMS methods on the placenta to decipher the chemical exposome and describe how the use of placenta can complement biofluids collected on the mother or the fetus.

Prepregnancy obesity and risk of placental inflammation at term: a selection bias analysis

PURPOSE

Placental histopathology is a resource for investigating obesity-associated pregnancy conditions. However, studies oversample adverse pregnancies, biasing findings. We examine the association between prepregnancy obesity (risk factor for inflammation) and histologic placental inflammation (correlated with impaired infant neurodevelopment) and how selection bias may influence the association.

METHODS

Singleton term deliveries between 2008 and 2012 from the Magee Obstetric Maternal and Infant database were analyzed. Prepregnancy body mass index (BMI) was categorized as underweight, lean (referent), overweight, and obese. Outcomes were diagnoses of acute (acute chorioamnionitis and fetal inflammation) and chronic placental inflammation (chronic villitis). Risk ratios for associations between BMI and placental inflammation were estimated using selection bias approaches: complete case, exclusion of pregnancy complications, multiple imputation, and inverse probability weighting. E-values approximated how susceptible estimates were to residual selection bias.

RESULTS

Across methods, obesity was associated with an 8-15% lower risk of acute chorioamnionitis, a 7%-14% lower risk of acute fetal inflammation, and a 12%-30% higher risk of chronic villitis relative to lean women. E-values indicated modest residual selection bias could explain away associations, though few measured indications of placental evaluations met this threshold.

CONCLUSIONS

Obesity may contribute to placental inflammation, and we highlight robust methods to analyze clinical data susceptible to selection bias.

Regulation of sexually dimorphic placental adaptation in LPS exposure-induced intrauterine growth restriction

BACKGROUND

Sexual dimorphism in placental physiology affects the functionality of placental adaptation during adverse pregnancy. Defects of placental function compromise fetal programming, affecting the offspring's adult life. However, studies focusing on the relationship between sex-specific placental adaptation and consequent fetal maldevelopment under sub-optimal uterus milieu are still elusive.

METHODS

Here, we investigated the effects of maternal lipopolysaccharide (LPS) exposure between placental sex. Pregnant ICR mice received intraperitoneal injection of phosphate-buffered saline or 100, 200, and 400 µg/kg LPS on the gestational day (GD) 15.5. To determine whether prenatal maternal LPS exposure resulted in complicated pregnancy outcomes, survival rate of embryos was calculated and the growth of embryos and placentas was examined. To elucidate global transcriptomic changes occurring in the placenta, total RNA-sequencing (RNA-seq) was performed in female and male placentas.

RESULTS

LPS administration induced placental inflammation in both sexes at GD 17.5. Prenatal infection resulted in growth retardation in both sexes of embryos, and especially more prevalently in male. Impaired placental development was observed in a sex-specific manner. LPS 400 µg/kg reduced the percentage area of the labyrinth in females and junctional zone in males, respectively. RNA-sequencing revealed widespread sexually dimorphic transcriptional changes in placenta. In particular, representative changes were involved in biological processes such as trophoblast differentiation, nutrient/ion transporter, pregnancy, and immune system.

CONCLUSIONS

Our results present the sexually dimorphic responses of placental physiology in intrauterine growth restriction model and provide tentative relationship further to be elucidated between sex-biased placental functional change and long-term effects on the offspring's later life.

Sex differences in innate and adaptive immunity impact fetal, placental, and maternal health†

The differences between males and females begin shortly after birth, continue throughout prenatal development, and eventually extend into childhood and adult life. Male embryos and fetuses prioritize proliferation and growth, often at the expense of the fetoplacental energy reserves. This singular focus on growth over adaptability leaves male fetuses and neonates vulnerable to adverse outcomes during pregnancy and birth and can have lasting impacts throughout life. Beyond this prioritization of growth, male placentas and fetuses also respond to infection and inflammation differently than female counterparts. Pregnancies carrying female fetuses have a more regulatory immune response, whereas pregnancies carrying male fetuses have a stronger inflammatory response. These differences can be seen as early as the innate immune response with differences in cytokine and chemokine signaling. The sexual dimorphism in immunity then continues into the adaptive immune response with differences in T-cell biology and antibody production and transfer. As it appears that these sex-specific differences are amplified in pathologic pregnancies, it stands to reason that differences in the placental, fetal, and maternal immune responses in pregnancy contribute to increased male perinatal morbidity and mortality. In this review, we will describe the genetic and hormonal contributions to the sexual dimorphism of fetal and placental immunity. We will also discuss current research efforts to describe the sex-specific differences of the maternal-fetal interface and how it impacts fetal and maternal health.

The Maternal Microbiome and Gestational Diabetes Mellitus: Cause and Effect

Gestational diabetes mellitus (GDM) is a growing public health concern that affects many pregnancies globally. The condition is associated with adverse maternal and neonatal outcomes including gestational hypertension, preeclampsia, placental abruption, preterm birth, stillbirth, and fetal growth restriction. In the long-term, mothers and children have an increased risk of developing metabolic diseases such as type 2 diabetes and cardiovascular disease. Accumulating evidence suggest that alterations in the maternal microbiome may play a role in the pathogenesis of GDM and adverse pregnancy outcomes. This review describes changes in the maternal microbiome during the physiological adaptations of pregnancy, GDM and adverse maternal and neonatal outcomes. Findings from this review highlight the importance of understanding the link between the maternal microbiome and GDM. Furthermore, new therapeutic approaches to prevent or better manage GDM are discussed. Further research and clinical trials are necessary to fully realize the therapeutic potential of the maternal microbiome and translate these findings into clinical practice.

The Placenta: A Maternofetal Interface

The placenta is the gatekeeper between the mother and the fetus. Over the first trimester of pregnancy, the fetus is nourished by uterine gland secretions in a process known as histiotrophic nutrition. During the second trimester of pregnancy, placentation has evolved to the point at which nutrients are delivered to the placenta via maternal blood (hemotrophic nutrition). Over gestation, the placenta must adapt to these variable nutrient supplies, to alterations in maternal physiology and blood flow, and to dynamic changes in fetal growth rates. Numerous questions remain about the mechanisms used to transport nutrients to the fetus and the maternal and fetal determinants of this process. Growing data highlight the ability of the placenta to regulate this process. As new technologies and omics approaches are utilized to study this maternofetal interface, greater insight into this unique organ and its impact on fetal development and long-term health has been obtained.

Neonatal immune signatures differ by sex regardless of neurodevelopmental disorder status: Macrophage migration inhibitory factor (MIF) alone reveals a sex by diagnosis interaction effect

Immune dysregulation, including aberrant peripheral cytokine/chemokine levels, is implicated in neurodevelopmental disorders (NDD) such as autism spectrum disorder (ASD). While the diagnosis of ASD is more common in males compared to females, sex effects in immune dysregulation related to neurodevelopment remain understudied. The aim of this exploratory study was to determine whether there are sex-specific effects in neonatal immune dysregulation with respect to an ASD or delayed development (DD) diagnosis. We utilized the data from the Early Markers for Autism study, a population based case-control study of prenatal and neonatal biomarkers of ASD. The immune profile of newborns later diagnosed with ASD (n = 482, 91 females), DD (n = 140, 61 females) and sex-matched general population controls (GP; n = 378, 67 females) were analyzed using neonatal bloodspots (NBS) via 42-plex multiplex assay. Multiple linear regression analysis was performed to identify whether sex was associated with differences in cytokine/chemokine levels of children with ASD, DD, and GP. A sex by diagnosis interaction effect was observed only for the chemokine macrophage migration inhibitory factor (MIF), with males displaying higher levels of NBS MIF than females in the GP control group (p = 0.02), but not in ASD (p = 0.52) or DD (p = 0.29) groups. We found that regardless of child diagnosis, newborn bloodspot eluates from females had a significantly higher concentration than males with the same diagnosis of the chemokines granulocyte chemotactic protein 2 (GCP-2; p < 0.0001), macrophage inflammatory protein 2-alpha (GROβ; p = 0.002), interferon-inducible t-cell alpha chemoattractant (I-TAC; p < 0.0001), stromal cell-derived factor 1 alpha and beta (SDF-1α-β; p = 0.03), innate inflammatory chemokines interferon-gamma induced protein 10 (IP-10; p = 0.02), macrophage inflammatory protein 1-alpha (MIP-1α; p = 0.02), and Th1-related pro-inflammatory cytokine interleukin-12 active heterodimer (IL-12p70; p = 0.002). In contrast, males had a higher concentration than females of secondary lymphoid-tissue chemokine (6CKINE; p = 0.02), monocyte chemotactic protein 1 (MCP-1; p = 0.005) and myeloid progenitor inhibitory factor 1 (MPIF-1; p = 0.03). Results were similar when analyses were restricted to NBS from DD and ASD further classified as ASD with intellectual disability (ID), ASD without ID, and DD (GCP-2, p = 0.007; I-TAC, p = 0.001; IP-10, p = 0.005; IL-12p70, p = 0.03 higher in females; MPIF-1, p = 0.03 higher in male). This study is the first to examine sex differences in neonatal cytokine/chemokine concentrations, and whether these differences are associated with neurodevelopmental outcomes. Results highlight the importance of considering sex as a critical factor in understanding the immune system as it relates to child development.

Sexual dimorphism in placental development and function: Comparative physiology with an emphasis on the pig

Across mammalian species, it has been demonstrated that sex influences birth weight, with males being heavier than females; a characteristic that can be observed from early gestation. Male piglets are more likely to be stillborn and have greater preweaning mortality than their female littermates, despite the additional maternal investment into male fetal growth. Given the conserved nature of the genome between the sexes, it is hypothesized that these developmental differences between males and females are most likely orchestrated by differential placental adaptation. This review summarizes the current understanding of fetal sex-specific differences in placental and endometrial structure and function, with an emphasis on pathways found to be differentially regulated in the pig including angiogenesis, apoptosis, and proliferation. Given the importance of piglet sex in agricultural enterprises, and the potential for skewed litter sex ratios, it is imperative to improve understanding of the relationship between fetal sex and molecular signaling in both the placenta and endometria across gestation.

Fetal sex and risk of pregnancy-associated malaria in Plasmodium falciparum-endemic regions: a meta-analysis

In areas of moderate to intense Plasmodium falciparum transmission, malaria in pregnancy remains a significant cause of low birth weight, stillbirth, and severe anaemia. Previously, fetal sex has been identified to modify the risks of maternal asthma, pre-eclampsia, and gestational diabetes. One study demonstrated increased risk of placental malaria in women carrying a female fetus. We investigated the association between fetal sex and malaria in pregnancy in 11 pregnancy studies conducted in sub-Saharan African countries and Papua New Guinea through meta-analysis using log binomial regression fitted to a random-effects model. Malaria infection during pregnancy and delivery was assessed using light microscopy, polymerase chain reaction, and histology. Five studies were observational studies and six were randomised controlled trials. Studies varied in terms of gravidity, gestational age at antenatal enrolment and bed net use. Presence of a female fetus was associated with malaria infection at enrolment by light microscopy (risk ratio 1.14 [95% confidence interval 1.04, 1.24]; P = 0.003; n = 11,729). Fetal sex did not associate with malaria infection when other time points or diagnostic methods were used. There is limited evidence that fetal sex influences the risk of malaria infection in pregnancy.

Transcriptomic profiling reveals differential cellular response to copper oxide nanoparticles and polystyrene nanoplastics in perfused human placenta

The growing nanoparticulate pollution (e.g. engineered nanoparticles (NPs) or nanoplastics) has been shown to pose potential threats to human health. In particular, sensitive populations such as pregnant women and their unborn children need to be protected from harmful environmental exposures. However, developmental toxicity from prenatal exposure to pollution particles is not yet well studied despite evidence of particle accumulation in human placenta. Our study aimed to investigate how copper oxide NPs (CuO NPs; 10-20 nm) and polystyrene nanoplastics (PS NPs; 70 nm) impact on gene expression in ex vivo perfused human placental tissue. Whole genome microarray analysis revealed changes in global gene expression profile after 6 h of perfusion with sub-cytotoxic concentrations of CuO (10 µg/mL) and PS NPs (25 µg/mL). Pathway and gene ontology enrichment analysis of the differentially expressed genes suggested that CuO and PS NPs trigger distinct cellular response in placental tissue. While CuO NPs induced pathways related to angiogenesis, protein misfolding and heat shock responses, PS NPs affected the expression of genes related to inflammation and iron homeostasis. The observed effects on protein misfolding, cytokine signaling, and hormones were corroborated by western blot (accumulation of polyubiquitinated proteins) or qPCR analysis. Overall, the results of the present study revealed extensive and material-specific interference of CuO and PS NPs with placental gene expression from a single short-term exposure which deserves increasing attention. In addition, the placenta, which is often neglected in developmental toxicity studies, should be a key focus in the future safety assessment of NPs in pregnancy.

Metformin Impacts Human Syncytiotrophoblast Mitochondrial Function from Pregnancies Complicated by Obesity and Gestational Diabetes Mellitus in a Sexually Dimorphic Manner

Maternal obesity and gestational diabetes mellitus (GDM) are associated with placental dysfunction, small for gestational age (SGA) offspring, and programming of adult-onset disease. We examine how metformin, commonly used to treat type A2 GDM, affects placental metabolism as well as mitochondrial content and function. Syncytiotrophoblasts (STBs) were prepared from placentas of male and female fetuses collected at term cesarean section from lean (pre-pregnancy BMI < 25), obese (BMI > 30), and obese A2GDM women. Metformin treatment (0.001-10 mM) of STB caused no change in non-mitochondrial respiration but significant concentration-dependent (1 and 10 mM) decreases in basal, maximal, and ATP-linked respiration and spare capacity. Respiration linked to proton leak was significantly increased in STB of male A2GDM placentas at low metformin concentrations. Metformin concentrations ≥1 mM increased glycolysis in STB from placentas from lean women, but only improved glycolytic capacity in female STB. Whereas metformin had little effect on superoxide generation from male STB of any group, it gave a concentration-dependent decrease in superoxide generation from female STB of lean and obese women. Fewer mitochondria were observed in STB from obese women and male STB from lean women with increasing metformin concentration. Metformin affects STB mitochondrial function in a sexually dimorphic manner but at concentrations above those reported in maternal circulation (approximately 0.01 mM) in women treated with metformin for GDM.

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.

Placental Changes and Neuropsychological Development in Children-A Systematic Review

Placental dysfunction may increase the offspring's later-life disease risk. The objective of this systematic review was to describe associations between pathological placental changes and neuropsychological outcomes in children after the neonatal period. The inclusion criteria were human studies; original research; direct placental variables; neuropsychological outcomes; and analysis between their associations. The exclusion criterion was the offspring's age-0-28 days or >19 years. The MEDLINE and EMBASE databases were last searched in May 2022. We utilized the ROBINS-I for the risk of bias assessment and performed a narrative synthesis. In total, 3252 studies were identified, out of which 16 were included (i.e., a total of 15,862 participants). Half of the studies were performed on children with neonatal complications, and 75% of the studies reported an association between a placental change and an outcome; however, following the completion of the funnel plots, a risk of publication bias was indicated. The largest study described a small association between placental size and a risk of psychiatric symptoms in boys only. Inconsistency between the studies limited the evidence in this review. In general, no strong evidence was found for an association between pathological placental changes and childhood neuropsychological outcomes after the neonatal period. However, the association between placental size and mental health in boys indicates a placental sexual dimorphism, thereby suggesting an increased vulnerability for male fetuses.

The ANGPTL3-4-8 Axis in Normal Gestation and in Gestational Diabetes, and Its Potential Involvement in Fetal Growth

Dyslipidemia in gestational diabetes has been associated with worse perinatal outcomes. The ANGPTL3-4-8 axis regulates lipid metabolism, especially in the transition from fasting to feeding. In this study, we evaluated the response of ANGPTL3, 4, and 8 after the intake of a mixed meal in women with normal glucose tolerance and gestational diabetes, and we assessed their gene expressions in different placental locations. Regarding the circulating levels of ANGPTL3, 4, and 8, we observed an absence of ANGPTL4 response after the intake of the meal in the GDM group compared to its presence in the control group. At the placental level, we observed a glucose tolerance-dependent expression pattern of ANGPTL3 between the two placental sides. When we compared the GDM pregnancies with the control pregnancies, a downregulation of the maternal side ANGPTL3 expression was observed. This suggests a dysregulation of the ANGPTL3-4-8 axis in GDM, both at the circulating level after ingestion and at the level of placental expression. Furthermore, we discerned that the expressions of ANGPTL3, 4, and 8 were related to birth weight and placental weight in the GDM group, but not in the control group, which suggests that they may play a role in regulating the transplacental passage of nutrients.

Oxidative stress on vessels at the maternal-fetal interface for female reproductive system disorders: Update

Considerable evidence shows that oxidative stress exists in the pathophysiological process of female reproductive system diseases. At present, there have been many studies on oxidative stress of placenta during pregnancy, especially for preeclampsia. However, studies that directly focus on the effects of oxidative stress on blood vessels at the maternal-fetal interface and their associated possible outcomes are still incomplete and ambiguous. To provide an option for early clinical prediction and therapeutic application of oxidative stress in female reproductive system diseases, this paper briefly describes the composition of the maternal-fetal interface and the molecular mediators produced by oxidative stress, focuses on the sources of oxidative stress and the signaling pathways of oxidative stress at the maternal-fetal interface, expounds the adverse consequences of oxidative stress on blood vessels, and deeply discusses the relationship between oxidative stress and some pregnancy complications and other female reproductive system diseases.

Sex differences in early and term placenta are conserved in adult tissues

BACKGROUND

Pregnancy complications vary based on the fetus's genetic sex, which may, in part, be modulated by the placenta. Furthermore, developmental differences early in life can have lifelong health outcomes. Yet, sex differences in gene expression within the placenta at different timepoints throughout pregnancy and comparisons to adult tissues remains poorly characterized.

METHODS

Here, we collect and characterize sex differences in gene expression in term placentas (≥ 36.6 weeks; 23 male XY and 27 female XX). These are compared with sex differences in previously collected first trimester placenta samples and 42 non-reproductive adult tissues from GTEx.

RESULTS

We identify 268 and 53 sex-differentially expressed genes in the uncomplicated late first trimester and term placentas, respectively. Of the 53 sex-differentially expressed genes observed in the term placentas, 31 are also sex-differentially expressed genes in the late first trimester placentas. Furthermore, sex differences in gene expression in term placentas are highly correlated with sex differences in the late first trimester placentas. We found that sex-differential gene expression in the term placenta is significantly correlated with sex differences in gene expression in 42 non-reproductive adult tissues (correlation coefficient ranged from 0.892 to 0.957), with the highest correlation in brain tissues. Sex differences in gene expression were largely driven by gene expression on the sex chromosomes. We further show that some gametologous genes (genes with functional copies on X and Y) will have different inferred sex differences if the X-linked gene expression in females is compared to the sum of the X-linked and Y-linked gene expression in males.

CONCLUSIONS

We find that sex differences in gene expression are conserved in late first trimester and term placentas and that these sex differences are conserved in adult tissues. We demonstrate that there are sex differences associated with innate immune response in late first trimester placentas but there is no significant difference in gene expression of innate immune genes between sexes in healthy full-term placentas. Finally, sex differences are predominantly driven by expression from sex-linked genes.

Precision-cut rat placental slices as a model to study sex-dependent inflammatory response to LPS and Poly I:C

Introduction

Maternal inflammation in pregnancy represents a major hallmark of several pregnancy complications and a significant risk factor for neurodevelopmental and neuropsychiatric disorders in the offspring. As the interface between the mother and the fetus, the placenta plays a crucial role in fetal development and programming. Moreover, studies have suggested that the placenta responds to an inflammatory environment in a sex-biased fashion. However, placenta-mediated immunoregulatory mechanisms are still poorly understood.

Methods

Therefore, we have developed a model of ex vivo precision-cut placental slices from the rat term placenta to study acute inflammatory response. Rat placental slices with a precise thickness of 200 µm were generated separately from male and female placentas. Inflammation was stimulated by exposing the slices to various concentrations of LPS or Poly I:C for 4 and 18 hours.

Results

Treatment of placental slices with LPS significantly induced the expression and release of proinflammatory cytokines TNF-α, IL-6, and IL-1β. In contrast, Poly I:C treatment resulted in a less-pronounced inflammatory response. Interestingly, the female placenta showed higher sensitivity to LPS than male placenta. Anti-inflammatory agents, curcumin, 1α,25- dihydroxyvitamin D3, and progesterone attenuated the LPS-induced proinflammatory cytokine response at both mRNA and protein levels.

Discussion

We conclude that rat placental slices represent a novel alternative model to study the role of sexual dimorphism in the acute inflammatory response and immune activation in pregnancy.

Placental Transcriptome Profiling in Subtypes of Diabetic Pregnancies Is Strongly Confounded by Fetal Sex

The placenta is a temporary organ with a unique structure and function to ensure healthy fetal development. Placental dysfunction is involved in pre-eclampsia (PE), fetal growth restriction, preterm birth, and gestational diabetes mellitus (GDM). A diabetic state affects maternal and fetal health and may lead to functional alterations of placental metabolism, inflammation, hypoxia, and weight, amplifying the fetal stress. The placental molecular adaptations to the diabetic environment and the adaptive spatio-temporal consequences to elevated glucose or insulin are largely unknown (2). We aimed to identify gene expression signatures related to the diabetic placental pathology of placentas from women with diabetes mellitus. Human placenta samples (n = 77) consisting of healthy controls, women with either gestational diabetes mellitus (GDM), type 1 or type 2 diabetes, and women with GDM, type 1 or type 2 diabetes and superimposed PE were collected. Interestingly, gene expression differences quantified by total RNA sequencing were mainly driven by fetal sex rather than clinical diagnosis. Association of the principal components with a full set of clinical patient data identified fetal sex as the single main explanatory variable. Accordingly, placentas complicated by type 1 and type 2 diabetes showed only few differentially expressed genes, while possible effects of GDM and diabetic pregnancy complicated by PE were not identifiable in this cohort. We conclude that fetal sex has a prominent effect on the placental transcriptome, dominating and confounding gene expression signatures resulting from diabetes mellitus in settings of well-controlled diabetic disease. Our results support the notion of placenta as a sexual dimorphic organ.

Maternal Underweight and Obesity Are Associated with Placental Pathologies in Human Pregnancy

Maternal underweight and obesity are prevalent conditions, associated with chronic, low-grade inflammation, poor fetal development, and long-term adverse outcomes for the child. The placenta senses and adapts to the pregnancy environment in an effort to support optimal fetal development. However, the mechanisms driving these adaptations, and the resulting placental phenotypes, are poorly understood. We hypothesised that maternal underweight and obesity would be associated with increased prevalence of placental pathologies in term and preterm pregnancies. Data from 12,154 pregnancies were obtained from the Collaborative Perinatal Project, a prospective cohort study conducted from 1959 to 1974. Macro- and microscopic placental pathologies were analysed across maternal prepregnancy body mass index (BMI) to assess differences in the presence of pathologies among underweight, overweight, and obese BMI groups compared to normal weight reference BMI at term and preterm. Placental pathologies were also assessed across fetal sex. Pregnancies complicated by maternal obesity had placentae with increased fetal inflammation at preterm, and increased inflammation of maternal gestational tissues at term. In term pregnancies, increasing maternal BMI associated with increased maternal vascular malperfusion (MVM), odds of an appropriately mature placenta for gestational age, and placental weight, and decreased placental efficiency. Male placentae, independent of maternal BMI, had increased inflammation, MVM, and placental efficiency than female placentae, particularly at term. Maternal underweight and obesity are not inert conditions for the placenta, and the histomorphological changes driven by suboptimal maternal BMI may serve as indicators of adversities experienced in utero and potential predictors of future health trajectories.

Glucose and oxygen in the early intrauterine environment and their role in developmental abnormalities

The early life environment can have profound impacts on the developing conceptus in terms of both growth and morphogenesis. These impacts can manifest in a variety of ways, including congenital fetal anomalies, placental dysfunction with subsequent effects on fetal growth, and adverse perinatal outcomes, or via effects on long-term health outcomes that may not be detected until later childhood or adulthood. Two key examples of environmental influences on early development are explored: maternal hyperglycaemia and gestational hypoxia. These are increasingly common pregnancy exposures worldwide, with potentially profound impacts on population health. We explore what is known regarding the mechanisms by which these environmental exposures can impact early intrauterine development and thus result in adverse outcomes in the immediate, short, and long term.

Genetic regulation of newborn telomere length is mediated and modified by DNA methylation

Telomere length at birth determines later life telomere length and potentially predicts ageing-related diseases. However, the genetic and epigenetic settings of telomere length in newborns have not been analyzed. In addition, no study yet has reported how the interplay between genetic variants and genome-wide cytosine methylation explains the variation in early-life telomere length. In this study based on 281 mother-newborn pairs from the ENVIRONAGE birth cohort, telomere length and whole-genome DNA methylation were assessed in cord blood and 26 candidate single nucleotide polymorphism related to ageing or telomere length were genotyped. We identified three genetic variants associated with cord blood telomere length and 57 cis methylation quantitative trait loci (cis-mQTLs) of which 22 mQTLs confirmed previous findings and 35 were newly identified. Five SNPs were found to have significant indirect effects on cord blood telomere length via the mediating CpGs. The association between rs911874 (SOD2) and newborn telomere length was modified by nearby DNA methylation indicated by a significant statistical interaction. Our results suggest that DNA methylation in cis might have a mediation or modification effect on the genetic difference in newborn telomere length. This novel approach warrants future follow-up studies that are needed to further confirm and extend these findings.

Reduced cell invasion may be a characteristic of placental defects in pregnant women of advanced maternal age at single-cell level

The mechanisms underlying pregnancy complications caused by advanced maternal age (AMA) remain unclear. We analyzed the cellular signature and transcriptomes of human placentas in AMA women to elucidate these mechanisms. Placental tissues from two AMA women and two controls were used for single-cell RNA-sequencing (scRNA-seq). Controls consisted of AMA women who did not experience any pregnancy complications and pregnant women below the age of 35 years without pregnancy complications. Trophoblast cells were obtained from the placentas of another six pregnant women (three AMA women and three controls), and in-vitro transwell assays were conducted to observe the cell invasion ability. Thirty additional samples (from 15 AMA women and 15 controls) were analyzed to verify the specific expression of serine protease inhibitor clade E member 1 (SERPINE1). Preliminary study of the role of SERPINE1 in cell invasion was carried out with HTR8-S/Vneo cells. High-quality transcriptomes of 27 ‍607 cells were detected. Three types of trophoblast cells were detected, which were further classified into eight subtypes according to differences in gene expression and Gene Ontology (GO) function. We identified 110 differentially expressed genes (DEGs) in trophoblast cells between the AMA and control groups, and the DEGs were enriched in multiple pathways related to cell invasion. In-vitro transwell assays suggested that the invading trophoblast cells in AMA women were reduced. SERPINE1 was specifically expressed in the trophoblast, and its expression was higher in AMA women (P<0.05). Transfection of human SERPINE1 (hSERPINE1) into HTR8-S/Vneo trophoblast cells showed fewer invading cells in the hSERPINE1 group. Impaired cell invasion may underlie the increased risk of adverse pregnancy outcomes in AMA women. Abnormal expression of SERPINE1 in extravillous trophoblast (EVT) cells appears to play an important role.

Sex at the interface: the origin and impact of sex differences in the developing human placenta

The fetal placenta is a source of hormones and immune factors that play a vital role in maintaining pregnancy and facilitating fetal growth. Cells in this extraembryonic compartment match the chromosomal sex of the embryo itself. Sex differences have been observed in common gestational pathologies, highlighting the importance of maternal immune tolerance to the fetal compartment. Over the past decade, several studies examining placentas from term pregnancies have revealed widespread sex differences in hormone signaling, immune signaling, and metabolic functions. Given the rapid and dynamic development of the human placenta, sex differences that exist at term (37–42 weeks gestation) are unlikely to align precisely with those present at earlier stages when the fetal–maternal interface is being formed and the foundations of a healthy or diseased pregnancy are established. While fetal sex as a variable is often left unreported in studies performing transcriptomic profiling of the first-trimester human placenta, four recent studies have specifically examined fetal sex in early human placental development. In this review, we discuss the findings from these publications and consider the evidence for the genetic, hormonal, and immune mechanisms that are theorized to account for sex differences in early human placenta. We also highlight the cellular and molecular processes that are most likely to be impacted by fetal sex and the evolutionary pressures that may have given rise to these differences. With growing recognition of the fetal origins of health and disease, it is important to shed light on sex differences in early prenatal development, as these observations may unlock insight into the foundations of sex-biased pathologies that emerge later in life.

Placental sex differences exist from early prenatal development, and may help explain sex differences in pregnancy outcomes.

Transcriptome profiling of early to mid-gestation placenta reveals that immune signaling is a hub of early prenatal sex differences.

Differentially expressed genes between male and female placenta fall into the following functional associations: chromatin modification, transcription, splicing, translation, signal transduction, metabolic regulation, cell death and autophagy regulation, ubiquitination, cell adhesion and cell–cell interaction.

Placental sex differences likely reflect the interaction of cell-intrinsic chromosome complement with extrinsic endocrine signals from the fetal compartment that accompany gonadal differentiation.

Understanding the mechanisms behind sex differences in placental development and function will provide key insight into molecular targets that can be modulated to improve sex-biased obstetrical complications.

Sex-dependent differential transcript expression in the placenta of growth restricted infants

INTRODUCTION

The pathological decrease of fetal growth during gestation can lead to subsequent poor health outcomes for the fetus. This process is commonly controlled by the placenta, the interface between mother and baby during gestation. Sex-specific gene expression has been implicated in placental function, therefore, there is a need to determine if it is important during reduced fetal growth. We therefore aimed to characterise placental gene expression at term to evaluate sex-specific genetic changes that occur in small for gestational age (SGA) infants.

METHODS

RNA-sequencing of twelve human placental tissue samples collected from pregnancies yielding either term appropriate for gestational age (AGA) or SGA infants identified at delivery. Candidate genes associated with fetal size and fetal sex were identified using differential gene expression and weighted gene co-expression network analyses. Single-cell sequencing data was used for candidate validation and to estimate candidate transcript expression in specific placental cell populations.

RESULTS

Differential gene expression and weighted gene co-expression network analyses identified 403 candidate transcripts associated with SGA infants. One hundred and three of these transcripts showed sex-specific expression. . Published placental sequencing datasets were used to validate the key expression results from the twelve placental samples initially studied; the sex-independent transcript expression for genes involved in cell cycle processes in males (7 transcripts) and endoplasmic reticulum stress in females (17 transcripts).

DISCUSSION

This study identified the activation of multiple molecular mechanisms involved in the placental response to an adverse environmental stressor. Mechanisms such as disrupted protein synthesis were shared between infant biological sex when comparing AGA to SGA, whilst other pathways such as cell cycle and endoplasmic reticulum stress appear as independent/specific to either males or females when investigating reduced fetal growth. This data suggests that sexual dimorphism is an important consideration when examining placental dysfunction and poor fetal growth.

Sex-specific association between placental inflammatory cytokine mRNA expression and preschoolers' behavioral development: The Ma'anshan birth cohort study

BACKGROUND

Placental inflammation may contribute to brain abnormalities and childhood neuropsychiatric disorders, but limited knowledge is available on the association of placental inflammatory cytokine levels and offspring's behavioral development. This study aimed to examine the sex-specific association between placental inflammatory cytokine mRNA expression and preschoolers' behavioral development.

METHODS

3474 pregnant women were recruited as the initial study population in the Ma'anshan birth cohort (MABC) study. Placentas (n = 2519) were collected during childbirth, and the mRNA expression of IL-8, IL-1β, CRP, TNF-α, IL-6, IL-10, and IL-4 was assessed. The Child Behavior Checklist 1.5-5 (CBCL 1.5-5) was used to assess children's behavioral development at 4 years old. A T-score ≥ 60 on summary scales or a score ≥ 65 on syndrome scales was regarded as the borderline clinical range. Multiple linear regression models and binary logistic regression models were applied to explore the sex-specific associations between placental inflammatory cytokines mRNA transcript levels and preschoolers' behavioral development.

RESULTS

Sex-specific associations between placental inflammatory cytokines mRNA expression and preschoolers' behavioral development were observed. There was a positive association between IL-8 and CBCL scores for boys on anxious/depressed problems, aggressive behaviors, externalizing problems and total problems. Logistic regression models showed that high levels of IL-8 were associated with a higher risk of girls' emotionally reactive problems and sleep problems compared to low/medium levels. High TNF-α was correlated with increased sleep problem scores in boys, and medium TNF-α (vs. low levels) was associated with an increased risk of girls' externalizing problems. Medium levels of CRP, IL-1β, and IL-6 were found to be associated with a decreased risk of girls' behavioral problems compared to low/high levels. For anti-inflammatory cytokines, medium IL-10 and IL-4 (vs. low levels) were observed to be associated with a lower risk of internalizing problems in boys and externalizing problems in girls, respectively. High IL-10 was correlated with decreased attention problem scores in boys.

CONCLUSION

This study indicates that placental inflammatory cytokine mRNA expression of IL-8, CRP, TNF-α, IL-1β, IL-4 and IL-10 may be associated with preschoolers' behavioral development in a sex-specific manner.

Epiblast inducers capture mouse trophectoderm stem cells in vitro and pattern blastoids for implantation in utero

The embryo instructs the allocation of cell states to spatially regulate functions. In the blastocyst, patterning of trophoblast (TR) cells ensures successful implantation and placental development. Here, we defined an optimal set of molecules secreted by the epiblast (inducers) that captures in vitro stable, highly self-renewing mouse trophectoderm stem cells (TESCs) resembling the blastocyst stage. When exposed to suboptimal inducers, these stem cells fluctuate to form interconvertible subpopulations with reduced self-renewal and facilitated differentiation, resembling peri-implantation cells, known as TR stem cells (TSCs). TESCs have enhanced capacity to form blastoids that implant more efficiently in utero due to inducers maintaining not only local TR proliferation and self-renewal, but also WNT6/7B secretion that stimulates uterine decidualization. Overall, the epiblast maintains sustained growth and decidualization potential of abutting TR cells, while, as known, distancing imposed by the blastocyst cavity differentiates TR cells for uterus adhesion, thus patterning the essential functions of implantation.