Maternal growth restriction and stress exposure in rats differentially alters expression of components of the placental glucocorticoid barrier and nutrient transporters

Maternal preconception stress produces sex-specific effects at the maternal:fetal interface to impact offspring development and phenotypic outcomes†

Entering pregnancy with a history of adversity, including adverse childhood experiences and racial discrimination stress, is a predictor of negative maternal and fetal health outcomes. Little is known about the biological mechanisms by which preconception adverse experiences are stored and impact future offspring health outcomes. In our maternal preconception stress (MPS) model, female mice underwent chronic stress from postnatal days 28-70 and were mated 2 weeks post-stress. Maternal preconception stress dams blunted the pregnancy-induced shift in the circulating extracellular vesicle proteome and reduced glucose tolerance at mid-gestation, suggesting a shift in pregnancy adaptation. To investigate MPS effects at the maternal:fetal interface, we probed the mid-gestation placental, uterine, and fetal brain tissue transcriptome. Male and female placentas differentially regulated expression of genes involved in growth and metabolic signaling in response to gestation in an MPS dam. We also report novel offspring sex- and MPS-specific responses in the uterine tissue apposing these placentas. In the fetal compartment, MPS female offspring reduced expression of neurodevelopmental genes. Using a ribosome-tagging transgenic approach we detected a dramatic increase in genes involved in chromatin regulation in a PVN-enriched neuronal population in females at PN21. While MPS had an additive effect on high-fat-diet (HFD)-induced weight gain in male offspring, both MPS and HFD were necessary to induce significant weight gain in female offspring. These data highlight the preconception period as a determinant of maternal health in pregnancy and provides novel insights into mechanisms by which maternal stress history impacts offspring developmental programming.

Developmental transcriptomic patterns can be altered by transgenic overexpression of Uty

The genetic material encoded on X and Y chromosomes provides the foundation by which biological sex differences are established. Epigenetic regulators expressed on these sex chromosomes, including Kdm6a (Utx), Kdm5c, and Ddx3x have far-reaching impacts on transcriptional control of phenotypic sex differences. Although the functionality of UTY (Kdm6c, the Y-linked homologue of UTX), has been supported by more recent studies, its role in developmental sex differences is not understood. Here we test the hypothesis that UTY is an important transcriptional regulator during development that could contribute to sex-specific phenotypes and disease risks across the lifespan. We generated a random insertion Uty transgenic mouse (Uty-Tg) to overexpress Uty. By comparing transcriptomic profiles in developmental tissues, placenta and hypothalamus, we assessed potential UTY functional activity, comparing Uty-expressing female mice (XX + Uty) with wild-type male (XY) and female (XX) mice. To determine if Uty expression altered physiological or behavioral outcomes, adult mice were phenotypically examined. Uty expression masculinized female gene expression patterns in both the placenta and hypothalamus. Gene ontology (GO) and gene set enrichment analysis (GSEA) consistently identified pathways including immune and synaptic signaling as biological processes associated with UTY. Interestingly, adult females expressing Uty gained less weight and had a greater glucose tolerance compared to wild-type male and female mice when provided a high-fat diet. Utilizing a Uty-overexpressing transgenic mouse, our results provide novel evidence as to a functional transcriptional role for UTY in developing tissues, and a foundation to build on its prospective capacity to influence sex-specific developmental and health outcomes.

Maternal-fetal cross-talk via the placenta: influence on offspring development and metabolism

Compelling epidemiological and animal experimental data demonstrate that cardiometabolic and neuropsychiatric diseases originate in a suboptimal intrauterine environment. Here, we review evidence suggesting that altered placental function may, at least in part, mediate the link between the maternal environment and changes in fetal growth and development. Emerging evidence indicates that the placenta controls the development and function of several fetal tissues through nutrient sensing, modulation of trophoblast nutrient transporters and by altering the number and cargo of released extracellular vesicles. In this Review, we discuss the development and functions of the maternal-placental-fetal interface (in humans and mice) and how cross-talk between these compartments may be a mechanism for in utero programming, focusing on mechanistic target of rapamycin (mTOR), adiponectin and O-GlcNac transferase (OGT) signaling. We also discuss how maternal diet and stress influences fetal development and metabolism and how fetal growth restriction can result in susceptibility to developing chronic disease later in life. Finally, we speculate how interventions targeting placental function may offer unprecedented opportunities to prevent cardiometabolic disease in future generations.

Physiological and pathological evidence of O-GlcNAcylation regulation during pregnancy related process

O-GlcNAcylation is a dynamic and reversible post-translational modification (PTM) controlled by the enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Changes in its expression lead to a breakdown in cellular homeostasis, which is linked to several pathological processes. Placentation and embryonic development are periods of high cell activity, and imbalances in cell signaling pathways can result in infertility, miscarriage, or pregnancy complications. O-GlcNAcylation is involved in cellular processes such as genome maintenance, epigenetic regulation, protein synthesis/degradation, metabolic pathways, signaling pathways, apoptosis, and stress response. Trophoblastic differentiation/invasion and placental vasculogenesis, as well as zygote viability and embryonic neuronal development, are all dependent on O-GlcNAcylation. This PTM is required for pluripotency, which is a required condition for embryonic development. Further, this pathway is a nutritional sensor and cell stress marker, which is primarily measured by the OGT enzyme and its product, protein O-GlcNAcylation. Yet, this post-translational modification is enrolled in metabolic and cardiovascular adaptations during pregnancy. Finally, evidence of how O-GlcNAc impacts pregnancy during pathological conditions such as hyperglycemia, gestational diabetes, hypertension, and stress disorders are reviewed. Considering this scenario, progress in understanding the role of O- GlcNAcylation in pregnancy is required.

Transcriptomic profiling of the developing brain revealed cell-type and brain-region specificity in a mouse model of prenatal stress

BACKGROUND

Prenatal stress (PS) is considered as a risk factor for many mental disorders. PS-induced transcriptomic alterations may contribute to the functional dysregulation during brain development. Here, we used RNA-seq to explore changes of gene expression in the mouse fetal brain after prenatal exposure to chronic unpredictable mild stress (CUMS).

RESULTS

We compared the stressed brains to the controls and identified groups of significantly differentially expressed genes (DEGs). GO analysis on up-regulated DEGs revealed enrichment for the cell cycle pathways, while down-regulated DEGs were mostly enriched in the neuronal pathways related to synaptic transmission. We further performed cell-type enrichment analysis using published scRNA-seq data from the fetal mouse brain and revealed cell-type-specificity for up- and down-regulated DEGs, respectively. The up-regulated DEGs were highly enriched in the radial glia, while down-regulated DEGs were enriched in different types of neurons. Cell deconvolution analysis further showed altered cell fractions in the stressed brain, indicating accumulation of neuroblast and impaired neurogenesis. Moreover, we also observed distinct brain-region expression pattern when mapping DEGs onto the developing Allen brain atlas. The up-regulated DEGs were primarily enriched in the dorsal forebrain regions including the cortical plate and hippocampal formation. Surprisingly, down-regulated DEGs were found excluded from the cortical region, but highly expressed on various regions in the ventral forebrain, midbrain and hindbrain.

CONCLUSION

Taken together, we provided an unbiased data source for transcriptomic alterations of the whole fetal brain after chronic PS, and reported differential cell-type and brain-region vulnerability of the developing brain in response to environmental insults during the pregnancy.

Pregnant biglycan knockout mice have altered cardiorenal adaptations and a shorter gestational length, but do not develop a pre-eclamptic phenotype

INTRODUCTION

Pre-eclampsia complicates 4.6% of pregnancies and is linked to impaired placentation; likely due to dysregulated vasculogenesis/angiogenesis. Proteoglycans, such as biglycan, are located on the endothelial surface of fetal capillaries. Biglycan is reduced in the placenta of pregnancies complicated by fetal growth restriction and pre-eclampsia. Importantly, biglycan stimulates angiogenesis in numerous tissues. Therefore, this study investigated whether biglycan knockdown in mice results in a pre-eclamptic phenotype.

METHODS

Wild-type (WT) and Bgn-/- mice underwent cardiorenal measurements prior to and during pregnancy. One cohort of mice underwent post-mortem on gestational day 18 (E18) and another cohort underwent post-mortem on postnatal day 1 (PN1), with maternal and offspring tissues of relevance collected.

RESULTS

Bgn-/- dams had increased heart rate (+9%, p < 0.037) and reduced systolic (-11%, p < 0.001), diastolic (-15%, p < 0.001), and mean arterial (-12%, p < 0.001) pressures at all ages investigated compared to WT. Additionally, Bgn-/- dams had reduced urine flow rate (-64%, p < 0.001) as well as reduced urinary excretions (-49%, p < 0.004) during late gestation compared to WT. Bgn-/- pups had higher body weight (+8%, p = 0.004; E18 only) and a higher liver-to-brain weight ratio (+43%, p < 0.001). Placental weight was unaltered with only minor changes in vasculogenic and angiogenic gene abundances detected, which did not correlate to changes in protein expression.

DISCUSSION

This study demonstrated that total knockdown of biglycan is not associated with features of pre-eclampsia.

Betamethasone administration during pregnancy is associated with placental epigenetic changes with implications for inflammation

BACKGROUND

Glucocorticoids (GCs) play a pivotal role in fetal programming. Antenatal treatment with synthetic GCs (sGCs) in individuals in danger of preterm labor is common practice. Adverse short- and long-term effects of antenatal sGCs have been reported, but their effects on placental epigenetic characteristics have never been systematically studied in humans.

RESULTS

We tested the association between exposure to the sGC betamethasone (BET) and placental DNA methylation (DNAm) in 52 exposed cases and 84 gestational-age-matched controls. We fine-mapped associated loci using targeted bisulfite sequencing. The association of placental DNAm with gene expression and co-expression analysis on implicated genes was performed in an independent cohort including 494 placentas. Exposure to BET was significantly associated with lower placenta DNAm at an enhancer of FKBP5. FKBP5 (FK506-binding protein 51) is a co-chaperone that modulates glucocorticoid receptor activity. Lower DNAm at this enhancer site was associated with higher expression of FKBP5 and a co-expressed gene module. This module is enriched for genes associated with preeclampsia and involved in inflammation and immune response.

CONCLUSIONS

Our findings suggest that BET exposure during pregnancy associates with few but lasting changes in placental DNAm and may promote a gene expression profile associated with placental dysfunction and increased inflammation. This may represent a pathway mediating GC-associated negative long-term consequences and health outcomes in offspring.

Protective role of IL33 signaling in negative pregnancy outcomes associated with lipopolysaccharide exposure

Interleukin 33 (IL33) signaling has been implicated in the establishment and maintenance of pregnancy and in pregnancy disorders. The goal of this project was to evaluate the role of IL33 signaling in rat pregnancy. The rat possesses hemochorial placentation with deep intrauterine trophoblast invasion; features also characteristic of human placentation. We generated and characterized a germline mutant rat model for IL33 using CRISPR/Cas9 genome editing. IL33 deficient rats exhibited deficits in lung responses to an inflammatory stimulus (Sephadex G-200) and to estrogen-induced uterine eosinophilia. Female rats deficient in IL33 were fertile and exhibited pregnancy outcomes (gestation length and litter size) similar to wild-type rats. Placental weight was adversely affected by the disruption of IL33 signaling. A difference in pregnancy-dependent adaptations to lipopolysaccharide (LPS) exposure was observed between wild-type and IL33 deficient pregnancies. Pregnancy in wild-type rats treated with LPS did not differ significantly from pregnancy in vehicle-treated wild-type rats. In contrast, LPS treatment decreased fetal survival rate, fetal and placental weights, and increased fetal growth restriction in IL33 deficient rats. In summary, a new rat model for investigating IL33 signaling has been established. IL33 signaling participates in the regulation of placental development and protection against LPS-induced fetal and placental growth restriction.

Maternal exercise alters rat fetoplacental stress response: Minimal effects of maternal growth restriction and high-fat feeding

INTRODUCTION

Fetal growth restriction complicates 10% of pregnancies and increases offspring (F1) risk of metabolic disorders, including obesity and gestational diabetes mellitus (GDM). This disease predisposition can be passed onto the next generation (F2). Importantly, the risk of pregnancy complications in obese women can be exacerbated by a stressful pregnancy. Exercise can reduce adiposity and improve health outcomes in obese women and those with GDM. This study investigated the impacts of maternal growth restriction, obesity, exercise, and stress on fetal and placental endocrine function.

METHODS

Uteroplacental insufficiency (Restricted) or sham (Control) surgery was induced on embryonic day (E) 18 in F0 Wistar-Kyoto rats. F1 offspring were fed a Chow or High-fat (HFD) diet from weaning and, at 16 weeks, were randomly allocated an exercise protocol; Sedentary, Exercised prior to and during pregnancy (Exercise), or Exercised only during pregnancy (PregEx). Females were mated and further randomly allocated to either undergo (Stress), or not undergo (Unstressed), physiological measurements during pregnancy. On E20, F2 fetal plasma (steroid hormones), tissues (brain, liver), and placentae (morphology, stress genes) were collected.

RESULTS

Maternal growth restriction and high-fat feeding had minimal impact on fetoplacental endocrine function. PregEx and Exercise increased cross-sectional labyrinth and junctional zone areas. PregEx, but not Exercise, increased fetal deoxycorticosterone concentrations and reduced placental Hsd11b2 and Nr3c2 gene abundance. Maternal stress increased fetal corticosterone concentrations in Sedentary HFD dams and increased placental cross-sectional areas in PregEx mothers.

DISCUSSION

PregEx and Stress independently dysregulates the endocrine status of the developing fetus, which may program future disease.

Maternal stress in relation to sex-specific expression of placental genes involved in nutrient transport, oxygen tension, immune response, and the glucocorticoid barrier

INTRODUCTION

Murine models provide evidence that maternal stress during pregnancy can influence placenta morphology and function, including altered expression of genes involved in the maintenance and progression of pregnancy and fetal development. Corresponding research evaluating the impact of maternal stress on placental gene expression in humans is limited. We examined maternal stress in relation to placental expression of 17 candidate genes in a community-based sample.

METHODS

Participants included 60 mother-newborn pairs enrolled in the PRogramming of Intergenerational Stress Mechanisms pregnancy cohort based at the Mount Sinai Hospital in New York City. Placentas were collected immediately following delivery and gene expression was measured using a qPCR-based platform. Maternal experiences of traumatic and non-traumatic stress were measured using the Life Stressor Checklist-Revised (LSC-R) administered during a mid-pregnancy interview. We used multivariable linear regression to examine associations between LSC-R scores and expression of each gene in separate models in the sample overall and stratified by fetal sex.

RESULTS

Higher maternal stress was associated with significantly increased placental expression of the nutrient sensor gene OGT, the glucose transporter gene GLUT1, and the hypoxia sensor gene HIF3A. In models stratified by fetal sex, significant associations remained only among males.

DISCUSSION

This study represents one of the most comprehensive examinations of maternal lifetime traumatic and non-traumatic stress in relation to placental gene expression in human tissue. Our findings support that maternal stress may alter sex-specific placental expression of genes involved in critical developmental processes.

Glucocorticoids as Mediators of Adverse Outcomes of Prenatal Stress

A number of prenatal experiences are associated with adverse outcomes after birth, ranging from cardiovascular problems to psychiatric disease. Prenatal stress is associated with neurodevelopmental alterations that persist after birth and manifest at the behavioral level, for example, increased fearfulness, and at the physiological one, that is, brain structural and functional changes. Understanding the mechanisms that drive these lasting effects may help in preventing long-term negative outcomes of prenatal stress. Elevated glucocorticoid signaling in utero may be one of the key mediators of prenatal stress effects on the offspring. In this review, we summarize how prenatal glucocorticoids may impact the activity of the fetal hypothalamic-pituitary-adrenal (HPA) axis, disrupt neurodevelopmental processes and alter the epigenetic landscape of the fetus. We also discuss the need to take into consideration the interaction of these processes with the offspring's genetic landscape.

Sex-specific regulation of stress-induced fetal glucocorticoid surge by the mouse placenta

Antenatal stress increases the prevalence of diseases in later life, which shows a strong sex-specific effect. However, the underlying mechanisms remain unknown. Maternal glucocorticoids can be elevated by stress and are potential candidates to mediate the effects of stress on the offspring sex-specifically. A comprehensive evaluation of dynamic maternal and placental mechanisms modulating fetal glucocorticoid exposure upon maternal stress was long overdue. Here, we addressed this gap in knowledge by investigating sex-specific responses to midgestational stress in mice. We observed increased levels of maternal corticosterone, the main glucocorticoid in rodents, along with higher corticosteroid-binding globulin levels at midgestation in C57Bl/6 dams exposed to sound stress. This resulted in elevated corticosterone in female fetuses, whereas male offspring were unaffected. We identified that increased placental expression of the glucocorticoid-inactivating enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2; Hsd11b2 gene) and ATP-binding cassette transporters, which mediate glucocorticoid efflux toward maternal circulation, protect male offspring from maternal glucocorticoid surges. We generated mice with an Hsd11b2 placental-specific disruption (Hsd11b2^PKO) and observed moderately elevated corticosterone levels in offspring, along with increased body weight. Subsequently, we assessed downstream glucocorticoid receptors and observed a sex-specific differential modulation of placental Tsc22d3 expression, which encodes the glucocorticoid-induced leucine zipper protein in response to stress. Taken together, our observations highlight the existence of unique and well-orchestrated mechanisms that control glucocorticoid transfer, exposure, and metabolism in the mouse placenta, pinpointing toward the existence of sex-specific fetal glucocorticoid exposure windows during gestation in mice.

Exercise initiated during pregnancy in rats born growth restricted alters placental mTOR and nutrient transporter expression

KEY POINTS

Fetal growth is dependent on effective placental nutrient transportation, which is regulated by mammalian target of rapamycin (mTOR) complex 1 modulation of nutrient transporter expression. These transporters are dysregulated in pregnancies affected by uteroplacental insufficiency and maternal obesity. Nutrient transporters and mTOR were altered in placentae of mothers born growth restricted compared to normal birth weight dams, with maternal diet- and fetal sex-specific responses. Exercise initiated during pregnancy downregulated mTOR protein expression, despite an increase in mTOR activation in male associated placentae, and reduced nutrient transporter gene abundance, which was also dependent on maternal diet and fetal sex. Limited changes were characterized with exercise initiated before and continued throughout pregnancy in nutrient transporter and mTOR expression. Maternal exercise during pregnancy differentially regulated mTOR and nutrient transporters in a diet- and sex-specific manner, which likely aimed to improve late gestational placental growth and neonatal survival.

ABSTRACT

Adequate transplacental nutrient delivery is essential for fetoplacental development. Intrauterine growth restriction and maternal obesity independently alter placental nutrient transporter expression. Although exercise is beneficial for maternal health, limited studies have characterized how the timing of exercise initiation influences placental nutrient transport. Therefore, this study investigated the impact of maternal exercise on placental mechanistic target of rapamycin (mTOR) and nutrient transporter expression in growth restricted mothers and whether these outcomes were dependent on maternal diet or fetal sex. Uteroplacental insufficiency or sham surgery was induced on embryonic day (E) 18 in Wistar-Kyoto rats. F1 offspring were fed a chow or high-fat diet from weaning and at 16 weeks were randomly allocated to an exercise protocol: sedentary, exercised prior to and during pregnancy, or exercised during pregnancy only. Females were mated with normal males (20 weeks) and F2 placentae collected at E20. Exercise during pregnancy only, reduced mTOR protein expression in all groups and increased mTOR activation in male associated placentae. Exercise during pregnancy only, decreased the expression of amino acid transporters in a diet- and sex-specific manner. Maternal growth restriction altered mTOR and system A amino acid transporter expression in a sex- and diet-specific manner. These data highlight that maternal exercise initiated during pregnancy alters placental mTOR expression, which may directly regulate amino acid transporter expression, to a greater extent than exercise initiated prior to and continued during pregnancy, in a diet- and fetal sex-dependent manner. These findings highlight that the timing of exercise initiation is important for optimal placental function.

Effect of pyrroloquinoline quinone disodium in female rats during gestating and lactating on reproductive performance and the intestinal barrier functions in the progeny

The objective of this study was to investigate the effects of dietary pyrroloquinoline quinone disodium (PQQ·Na2) supplementation on the reproductive performance and intestinal barrier functions of gestating and lactating female Sprague–Dawley (SD) rats and their offspring. Dietary supplementation with PQQ·Na2increased the number of implanted embryos per litter during gestation and lactation at GD 20 and increased the number of viable fetuses per litter, and the weight of uterine horns with fetuses increased at 1 d of newborn. The mRNA expression levels of catalase (CAT), glutathione peroxidase (GPx2), superoxide dismutase (SOD1), solute carrier family 2 member 1 (Slc2a1) and solute carrier family 2 member 3 (Slc2a3) in the placenta were increased with dietary PQQ·Na2supplementation. Dietary supplementation with PQQ·Na2in gestating and lactating rats increased the CAT, SOD and GPx activities of the jejunal mucosa of weaned rats on PD 21. Dietary supplementation with PQQ·Na2in female rats affected the expression of tight junction proteins (claudin, zonula occludens-1(ZO-1) andoccludin) in the jejunal mucosa of their offspring by increasing the expression ofZO-1mRNA in the expression ofZO-1and claudin mRNA in the jejunal mucosa of weaned rats on PD 21. In conclusion, dietary supplementation with PQQ·Na2in gestating and lactating female rats had positive effects on their reproductive performance and on the intestinal barrier of weaned rats.

O-GlcNAc Modification During Pregnancy: Focus on Placental Environment

Successful placentation is a key event for fetal development, which commences following embryo implantation into the uterine wall, eliciting decidualization, placentation, and remodeling of blood vessels to provide physiological exchange between embryo-fetus and mother. Several signaling pathways are recruited to modulate such important processes and specific proteins that regulate placental function are a target for the glycosylation with O-linked β-N-acetylglucosamine (O-GlcNAc), or O-GlcNAcylation. This is a reversible post-translational modification on nuclear and cytoplasmic proteins, mainly controlled by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). O-GlcNAcylation has been implicated as a modulator of proteins, both in physiological and pathological conditions and, more recently, O-GlcNAc has also been shown to be an important modulator in placental tissue. In this mini-review, the interplay between O-GlcNAcylation of proteins and placental function will be addressed, discussing the possible implications of this post-translational modification through placental development and pregnancy.