Placental development: lessons from mouse mutants

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

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

CORE CONSERVED TRANSCRIPTIONAL REGULATORY NETWORKS DEFINE THE INVASIVE TROPHOBLAST CELL LINEAGE

The invasive trophoblast cell lineage in rat and human share crucial responsibilities in establishing the uterine-placental interface of the hemochorial placenta. These observations have led to the rat becoming an especially useful animal model to study hemochorial placentation. However, our understanding of similarities or differences between regulatory mechanisms governing rat and human invasive trophoblast cell populations is limited. In this study, we generated single-nucleus (sn) ATAC-seq data from gestation day (gd) 15.5 and 19.5 rat uterine-placental interface tissues and integrated the data with single-cell RNA-seq data generated at the same stages. We determined the chromatin accessibility profiles of invasive trophoblast, natural killer, macrophage, endothelial, and smooth muscle cells, and compared invasive trophoblast chromatin accessibility to extravillous trophoblast (EVT) cell accessibility. In comparing chromatin accessibility profiles between species, we found similarities in patterns of gene regulation and groups of motifs enriched in accessible regions. Finally, we identified a conserved gene regulatory network in invasive trophoblast cells. Our data, findings and analysis will facilitate future studies investigating regulatory mechanisms essential for the invasive trophoblast cell lineage.

Dynamic antagonism between key repressive pathways maintains the placental epigenome

DNA and Histone 3 Lysine 27 methylation typically function as repressive modifications and operate within distinct genomic compartments. In mammals, the majority of the genome is kept in a DNA methylated state, whereas the Polycomb repressive complexes regulate the unmethylated CpG-rich promoters of developmental genes. In contrast to this general framework, the extra-embryonic lineages display non-canonical, globally intermediate DNA methylation levels, including disruption of local Polycomb domains. Here, to better understand this unusual landscape's molecular properties, we genetically and chemically perturbed major epigenetic pathways in mouse trophoblast stem cells. We find that the extra-embryonic epigenome reflects ongoing and dynamic de novo methyltransferase recruitment, which is continuously antagonized by Polycomb to maintain intermediate, locally disordered methylation. Despite its disorganized molecular appearance, our data point to a highly controlled equilibrium between counteracting repressors within extra-embryonic cells, one that can seemingly persist indefinitely without bistable features typically seen for embryonic forms of epigenetic regulation.

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

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

A differentiation roadmap of murine placentation at single-cell resolution

The placenta is one of the most important yet least understood organs. Due to the limitations of conventional research approaches, we are still far from a comprehensive understanding of mouse placentation, especially regarding the differentiation of trophoblast lineages at the early developmental stage. To decipher cell compositions and developmental processes, we systematically profile the single-cell transcriptomes of trophoblast cells from extraembryonic tissues (embryonic day 7.5 (E7.5) and E8.5) and placentae (E9.5-E14.5) at one-day intervals. We identify distinct trophoblast cell types during mouse placentation, including unreported progenitor cells and intermediate precursor cells. An updated differentiation roadmap of mouse trophoblast lineages is presented following systematic transcriptome analyses. Based on transcriptomic regulatory network inference, we specify transcription factors responsible for the regulation of dynamic developmental processes during lineage diversification. We map lineage differentiation trajectories and find that sinusoid trophoblast giant cells arise from the subpopulation of ectoplacental cone cells. We provide a comprehensive single-cell data resource to shed light on future mechanistic studies of the gene regulatory networks governing hemochorial placentation.

Cellular Senescence, a Novel Area of Investigation for Metastatic Diseases

Metastasis is a systemic condition and the major challenge among cancer types, as it can lead to multiorgan vulnerability. Recently, attention has been drawn to cellular senescence, a complex stress response condition, as a factor implicated in metastatic dissemination and outgrowth. Here, we examine the current knowledge of the features required for cells to invade and colonize secondary organs and how senescent cells can contribute to this process. First, we describe the role of senescence in placentation, itself an invasive process which has been linked to higher rates of invasive cancers. Second, we describe how senescent cells can contribute to metastatic dissemination and colonization. Third, we discuss several metabolic adaptations by which senescent cells could promote cancer survival along the metastatic journey. In conclusion, we posit that targeting cellular senescence may have a potential therapeutic efficacy to limit metastasis formation.

The maternal microbiome promotes placental development in mice

The maternal microbiome is an important regulator of gestational health, but how it impacts the placenta as the interface between mother and fetus remains unexplored. Here we show that the maternal gut microbiota supports placental development in mice. Depletion of the maternal gut microbiota restricts placental growth and impairs feto-placental vascularization. The maternal gut microbiota modulates metabolites in the maternal and fetal circulation. Short-chain fatty acids (SCFAs) stimulate angiogenesis-related tube formation by endothelial cells and prevent abnormalities in placental vascularization in microbiota-deficient mice. Furthermore, in a model of maternal malnutrition, gestational supplementation with SCFAs prevents placental growth restriction and vascular insufficiency. These findings highlight the importance of host-microbial symbioses during pregnancy and reveal that the maternal gut microbiome promotes placental growth and vascularization in mice.

Role of functional fatty acids in modulation of reproductive potential in livestock

Fatty acids are not only widely known as energy sources, but also play important roles in many metabolic pathways. The significance of fatty acids in modulating the reproductive potential of livestock has received greater recognition in recent years. Functional fatty acids and their metabolites improve follicular development, oocyte maturation and embryo development, as well as endometrial receptivity and placental vascular development, through enhancing energy supply and precursors for the synthesis of their productive hormones, such as steroid hormones and prostaglandins. However, many studies are focused on the impacts of individual functional fatty acids in the reproductive cycle, lacking studies involved in deeper mechanisms and optimal fatty acid requirements for specific physiological stages. Therefore, an overall consideration of the combination and synergy of functional fatty acids and the establishment of optimal fatty acid requirement for specific stages is needed to improve reproductive potential in livestock.

Estrogen Actions in Placental Vascular Morphogenesis and Spiral Artery Remodeling: A Comparative View between Humans and Mice

Estrogens, mainly 17β-estradiol (E2), play a critical role in reproductive organogenesis, ovulation, and fertility via estrogen receptors. E2 is also a well-known regulator of utero-placental vascular development and blood-flow dynamics throughout gestation. Mouse and human placentas possess strikingly different morphological configurations that confer important reproductive advantages. However, the functional interplay between fetal and maternal vasculature remains similar in both species. In this review, we briefly describe the structural and functional characteristics, as well as the development, of mouse and human placentas. In addition, we summarize the current knowledge regarding estrogen actions during utero-placental vascular morphogenesis, which includes uterine angiogenesis, the control of trophoblast behavior, spiral artery remodeling, and hemodynamic adaptation throughout pregnancy, in both mice and humans. Finally, the estrogens that are present in abnormal placentation are also mentioned. Overall, this review highlights the importance of the actions of estrogens in the physiology and pathophysiology of placental vascular development.

ELAC2 Functions as a Key Gene in the Early Development of Placental Formation Based on WGCNA

The placenta plays a crucial role in mammalian fetal growth. The most important cell type in the placenta is the trophoblast cell. Many genes have been reported to play important functions in the differentiation of early placental trophoblast cells. Weighted gene co-expression network analysis (WGCNA) is a systematic biological method for describing the correlation patterns among genes across microarray samples. We used WGCNA to screen placental trophoblast development-related genes, and through experimental confirmation, we showed that, among these genes, ELAC2 may play an important regulatory role in the early development of mammalian placental formation. ELAC2 regulates early placental trophoblast differentiation by affecting cell migration and cell proliferation. In addition, ELAC2 may be involved in regulating cell migration processes in a manner that affects epithelial mesenchymal transition (EMT).

The Vast Utility of Drosophila Oogenesis

In this chapter, we highlight examples of the diverse array of developmental, cellular, and biochemical insights that can be gained by using Drosophila melanogaster oogenesis as a model tissue. We begin with an overview of ovary development and adult oogenesis. Then we summarize how the adult Drosophila ovary continues to advance our understanding of stem cells, cell cycle, cell migration, cytoplasmic streaming, nurse cell dumping, and cell death. We also review emerging areas of study, including the roles of lipid droplets, ribosomes, and nuclear actin in egg development. Finally, we conclude by discussing the growing conservation of processes and signaling pathways that regulate oogenesis and female reproduction from flies to humans.

DNA Methylation and Histone Modification Are the Possible Regulators of Preimplantation Blastocyst Activation in Mice

Under ovarian hormone control, dormant blastocysts obtain implantation capacity (known as blastocyst activation) through their global gene expression. After the activated blastocysts communicate with the receptive uterus, the implantation-competent blastocysts start the implantation. Although dormant and activated blastocysts have different gene expression levels, the regulatory mechanisms underlying these transcriptions remain unclear. Hence, this study aimed to analyze epigenetic marks in dormant and activated blastocysts. In mice, blastocyst dormancy is artificially induced by daily progesterone injection without estrogen supplementation after peri-implantation ovariectomy; when estrogen is administered concomitantly, blastocyst activation and implantation occur. These phenomena demonstrate a mouse model of delayed implantation. We collected dormant and activated blastocysts from a delayed implantation mouse model. RNA-seq, methylated DNA immunoprecipitation (MeDIP)-seq, and chromatin immunoprecipitation (ChIP)-seq for H3K4 me3 and H3K27 me3 were performed using dormant and activated blastocysts. Cell cycle-related transcripts were affected during blastocyst activation. DNA methylations were accumulated in downregulated genes in the activated blastocysts. Histone H3 trimethylations were globally altered between the dormant and activated blastocysts. Dormant and activated blastocysts have unique methylation patterns on DNA and histone H3, with high correlation to gene expression. DNA methylation and histone modification can regulate preimplantation blastocyst activation.

Identifying novel regulators of placental development using time-series transcriptome data

The placenta serves as a connection between the mother and the fetus during pregnancy, providing the fetus with oxygen, nutrients, and growth hormones. However, the regulatory mechanisms and dynamic gene interaction networks underlying early placental development are understudied. Here, we generated RNA-sequencing data from mouse fetal placenta at embryonic days 7.5, 8.5, and 9.5 to identify genes with timepoint-specific expression, then inferred gene interaction networks to analyze highly connected network modules. We determined that timepoint-specific gene network modules were associated with distinct developmental processes, and with similar expression profiles to specific human placental cell populations. From each module, we identified hub genes and their direct neighboring genes, which were predicted to govern placental functions. We confirmed that four novel candidate regulators identified through our analyses regulate cell migration in the HTR-8/SVneo cell line. Overall, we predicted several novel regulators of placental development expressed in specific placental cell types using network analysis of bulk RNA-sequencing data. Our findings and analysis approaches will be valuable for future studies investigating the transcriptional landscape of early development.

Mouse models of Zika virus transplacental transmission

Seven years after the onset of the Zika virus (ZIKV) epidemic in the Americas, longitudinal studies are beginning to demonstrate that children infected in utero and born without severe birth defects exhibit motor skill deficits at up to 3 years of age. Long term health and socioeconomic impacts of fetal ZIKV infection appear imminent. ZIKV continues to circulate in low levels much as the virus did for decades prior to the 2015 epidemic, and the timing of the ZIKV outbreak is unknown. Thus, in the continued absence of ZIKV vaccines or antivirals, small animal models of ZIKV transplacental transmission have never been more necessary to test antiviral strategies for both mother and fetuses, and to elucidate mechanisms of immunity at the maternal-fetal interface. Here we review the state of ZIKV transplacental transmission models, highlight key unanswered questions, and set goals for the next generation of mouse models.

CCR5 contributes to adverse outcomes during malaria in pregnancy

CCR5 is a chemokine receptor that mediates cell recruitment to sites of inflammation. It has been previously reported that the expression of CCR5 is increased in the placentas of women with malaria, a disease characterized by causing deliveries with low birth weight among other complications. CCR5 has been associated with pathology of protozoan infections during pregnancy but its role during malaria in pregnancy has not been elucidated. In the present work, we assessed the pregnancy outcome, placental structure, and levels of inflammatory markers of pregnant C57BL/6 and CCR5-/- mice infected or not with Plasmodium berghei NK65, with the purpose of determine the role of CCR5 in pregnancy associated malaria complications. We demonstrated that the expression of CCR5 mRNA increases in late pregnancy placentas of C57BL/6 when compared to uninfected controls. Infected pregnant C57BL/6 mice showed preterm birth, decreased fetal weight, placental inefficiency, and reduced placental vascular space. On the other hand, CCR5 deficiency led to increased levels of maternal parasitemia, reduced fetal weight and placental inefficiency compared to C57BL/6 mice. However, the infection did not cause additional changes in these parameters or in the incidence of preterm delivery in infected CCR5-/- mice in relation to C57BL/6 mice, showing that CCR5 may contribute to the adverse effects caused by infection during pregnancy. This improvement in pregnancy outcome, observed in infected CCR5-/- mice, was accompanied by lower placental levels of the inflammatory markers, such as TNF and NAG. Furthermore, it was observed that the placentas of CCR5-/- animals showed structural differences in relation to C57BL/6 mice, which could improve the efficiency of maternal-fetal exchanges, reflecting on fetal weight. Taken together, these results indicate that CCR5 expression contributes to the adverse outcomes caused by malaria in late pregnancy.

Mechanisms and function of de novo DNA methylation in placental development reveals an essential role for DNMT3B

DNA methylation is a repressive epigenetic modification that is essential for development, exemplified by the embryonic and perinatal lethality observed in mice lacking de novo DNA methyltransferases (DNMTs). Here we characterise the role for DNMT3A, 3B and 3L in gene regulation and development of the mouse placenta. We find that each DNMT establishes unique aspects of the placental methylome through targeting to distinct chromatin features. Loss of Dnmt3b results in de-repression of germline genes in trophoblast lineages and impaired formation of the maternal-foetal interface in the placental labyrinth. Using Sox2-Cre to delete Dnmt3b in the embryo, leaving expression intact in placental cells, the placental phenotype was rescued and, consequently, the embryonic lethality, as Dnmt3b null embryos could now survive to birth. We conclude that de novo DNA methylation by DNMT3B during embryogenesis is principally required to regulate placental development and function, which in turn is critical for embryo survival.

The inter- and multi- generational epigenetic alterations induced by maternal cadmium exposure

Exposure to cadmium during pregnancy, from environmental or lifestyle factors, has been shown to have detrimental fetal and placental developmental effects, along with negatively impacting maternal health during gestation. Additionally, prenatal cadmium exposure places the offspring at risk for developing diseases in infancy, adolescence, and adulthood. Although given much attention, the underlying mechanisms of cadmium-induced teratogenicity and disease development remain largely unknown. Epigenetic changes in DNA, RNA and protein modifications have been observed during cadmium exposure, which implies a scientific premise as a conceivable mode of cadmium toxicity for developmental origins of health and disease (DOHaD). This review aims to examine the literature and provide a comprehensive overview of epigenetic alterations induced by prenatal cadmium exposure, within the developing fetus and placenta, and the continued effects observed in childhood and across generations.

Biochemistry and pathophysiology of the Transient Potential Receptor Vanilloid 6 (TRPV6) calcium channel

TRPV6 is a Transient Receptor Potential Vanilloid (TRPV) cation channel with high selectivity for Ca²⁺ ions. First identified in 1999 in a search for the gene which mediates intestinal Ca²⁺ absorption, its far more extensive repertoire as a guardian of intracellular Ca²⁺ has since become apparent. Studies on TRPV6-deficient mice demonstrated additional important roles in placental Ca²⁺ transport, fetal bone development and male fertility. The first reports of inherited deficiency in newborn babies appeared in 2018, revealing its physiological importance in humans. There is currently strong evidence that TRPV6 also contributes to the pathogenesis of some common cancers. The recently reported association of TRPV6 deficiency with non-alcoholic chronic pancreatitis suggests a role in normal pancreatic function. Over time and with greater awareness of TRPV6, other disease-associations are likely to emerge. Powerful analytical tools have provided invaluable insights into the structure and operation of TRPV6. Its roles in Ca²⁺ signaling and carcinogenesis, and the use of channel inhibitors in cancer treatment are being intensively investigated. This review first briefly describes the biochemistry and physiology of the channel, and analytical methods used to investigate these. The focus subsequently shifts to the clinical disorders associated with abnormal expression and the underlying pathophysiology. The aims of this review are to increase awareness of this channel, and to draw together findings from a wide range of sources which may help to formulate new ideas for further studies.

Protocol to isolate and culture primary mouse feto-placental endothelial cells

In the mouse, feto-placental endothelial cells (FPEC) line the inner surface of the feto-placental blood vessels located within placental labyrinthine zone and play critical roles in placental development and function. Here, we present a detailed protocol for isolation and culture of primary mouse FPEC, as well as two complementary methods (immunohistochemistry staining and flow cytometry analysis) to assess their purity. These cells are suitable for downstream ex vivo studies to investigate their functional properties, both in normal and pathological contexts. For complete details on the use and execution of this protocol, please refer to Sandovici et al. (2022).

Mesothelial fusion mediates chorioallantoic membrane formation

In amniotic vertebrates (birds, reptiles and mammals), an extraembryonic structure called the chorioallantoic membrane (CAM) functions as respiratory organ for embryonic development. The CAM is derived from fusion between two pre-existing membranes, the allantois, a hindgut diverticulum and a reservoir for metabolic waste, and the chorion which marks the embryo's external boundary. Modified CAM in eutherian mammals, including humans, gives rise to chorioallantoic placenta. Despite its importance, little is known about cellular and molecular mechanisms mediating CAM formation and maturation. In this work, using the avian model, we focused on the early phase of CAM morphogenesis when the allantois and chorion meet and initiate fusion. We report here that chicken chorioallantoic fusion takes place when the allantois reaches the size of 2.5-3.0 mm in diameter and in about 6 hours between E3.75 and E4. Electron microscopy and immunofluorescence analyses suggested that before fusion, in both the allantois and chorion, an epithelial-shaped mesothelial layer is present, which dissolves after fusion, presumably by undergoing epithelial-mesenchymal transition. The fusion process per se, however, is independent of allantoic growth, circulation, or its connection to the developing mesonephros. Mesoderm cells derived from the allantois and chorion can intermingle post-fusion, and chorionic ectoderm cells exhibit a specialized sub-apical intercellular interface, possibly to facilitate infiltration of allantois-derived vascular progenitors into the chorionic ectoderm territory for optimal oxygen transport. Finally, we investigated chorioallantoic fusion-like process in primates, with limited numbers of archived human and fresh macaque samples. We summarize the similarities and differences of CAM formation among different amniote groups and propose that mesothelial epithelial-mesenchymal transition mediates chorioallantoic fusion in most amniotic vertebrates. Further study is needed to clarify tissue morphogenesis leading to chorioallantoic fusion in primates. Elucidating molecular mechanisms regulating mesothelial integrity and epithelial-mesenchymal transition will also help understand mesothelial diseases in the adult, including mesothelioma, ovarian cancer and fibrosis. This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'.

GATA3 mediates nonclassical β-catenin signaling in skeletal cell fate determination and ectopic chondrogenesis

Skeletal precursors are mesenchymal in origin and can give rise to distinct sublineages. Their lineage commitment is modulated by various signaling pathways. The importance of Wnt signaling in skeletal lineage commitment has been implicated by the study of β-catenin-deficient mouse models. Ectopic chondrogenesis caused by the loss of β-catenin leads to a long-standing belief in canonical Wnt signaling that determines skeletal cell fate. As β-catenin has other functions, it remains unclear whether skeletogenic lineage commitment is solely orchestrated by canonical Wnt signaling. The study of the Wnt secretion regulator Gpr177/Wntless also raises concerns about current knowledge. Here, we show that skeletal cell fate is determined by β-catenin but independent of LEF/TCF transcription. Genomic and bioinformatic analyses further identify GATA3 as a mediator for the alternative signaling effects. GATA3 alone is sufficient to promote ectopic cartilage formation, demonstrating its essential role in mediating nonclassical β-catenin signaling in skeletogenic lineage specification.

Adgrg1 is a new transcriptional target of Hand1 during trophoblast giant cell differentiation

The placenta, forming the maternal-fetal interface, is essential for the survival and development of the fetus. It has been shown that the basic helix-loop-helix (bHLH) transcription factor Hand1 plays an important role in trophoblast giant cells (TGCs) differentiation during placental development in mice. However, the underlying molecular mechanism remains elusive. We hereby report that Adgrg1 (GPR56), a G protein coupled receptor, was a new transcriptional target of Hand1. Hand1 activated the expression of Adgrg1 by binding to its promoter region during TGCs differentiation. Double in situ hybridization revealed co-expression of Hand1 and Adgrg1 in Prl2c2⁺ TGCs located in the junctional zone of the placenta. Knockdown of Adgrg1 not only led to increased Prl2c2 expression, but also the improvement of cell migration and invasion during TGC differentiation. Moreover, the ligand of Adgrg1, Tgm2, was expressed in Prl2c2⁺ TGCs located in the placental junctional zone and Tgm2 Knockdown increased cell migration and invasion, suggesting Tgm2 is a potential ligand involved in the functions of Adgrg1 during TGC differentiation in the manners of autocrine. Collectively, these results demonstrate that Adgrg1 is a new transcriptional target of Hand1, affecting Prl2c2 expression as well as cell migration and invasion during TGCs differentiation. As a transmembrane receptor, Adgrg1 perhaps could act as a potential therapeutic target for placental-associated diseases caused by abnormal trophoblast migration and invasion, providing new insights for the preventions and therapies of placenta-related diseases.

The intricate nature of senescence in development and cell plasticity

Cellular senescence, a stable form of cell cycle arrest, accompanied by pronounced secretory activity, has functional roles in both physiological and pathological conditions. Although senescence has been linked for a long time with cancer and ageing, recent studies have revealed a functional role of senescence in development, regeneration and reprogramming. Notably, the transient presence of senescent cells may be beneficial, in contrast to the potential deleterious effects of persistent senescence in aged or chronically damaged tissues. We will discuss how senescence contributes to embryonic development, cell plasticity and tissue regeneration, as a highly coordinated and programmed cellular state.

Gestational Exposure to Cyfluthrin through Endoplasmic Reticulum (ER) Stress-Mediated PERK Signaling Pathway Impairs Placental Development

Cyfluthrin, a typical type II pyrethroid pesticide, is widely used in house hygiene and agricultural pest control. Several epidemiological investigations have found that maternal pyrethroid exposure is connected to adverse pregnancy outcomes. However, the underlying mechanisms remain to be elucidated. Thus, we evaluated the effect of cyfluthrin exposure during pregnancy on placenta development in vivo. In the current study, Pregnant SD rats were randomly divided into four groups and administered 6.25, 12.5, and 25 mg/kg body weight cyfluthrin or an equivalent volume of corn oil by gavage from GD0 to GD19. The results have shown that gestational exposure to cyfluthrin exerted no effect on the fetal birth defect, survival to PND4, or fetal resorption and death. However, live fetuses and implantation sites significantly decreased in the high-dose cyfluthrin-treated group. Moreover, a significant reduction in placenta weight and diameter was observed in rats. Correspondingly, the fetal weight and crown-rump length from dams exposed to cyfluthrin were reduced. Cyfluthrin-treat groups, the total area of the placenta, spongiotrophoblast area, and labyrinth area had abnormal changes. Meanwhile, the area of blood sinusoid and CD34-positive blood vessel numbers in the placenta were considerably reduced, as well as abnormal expression of placental pro-angiogenic and anti-angiogenic factors in dams exposed to cyfluthrin. Further observation by transmission electron microscopy revealed significant changes in the ultrastructure of the medium-dose and high-dose groups. Additional experiments showed gestational exposure to cyfluthrin inhibited proliferation and induced apoptosis of placentas, as decreased PCNA-positive cells and increased TUNEL-positive cells. Furthermore, western blot and qPCR analysis revealed that gestational exposure to medium-dose and high-dose cyfluthrin increased the expression of GRP78, and three downstream mRNA and proteins (p-eIF2α, ATF4, and CHOP) of the PERK signaling, indicating that endoplasmic reticulum (ER) stress-mediated PERK/eIF2α/ATF4/CHOP signaling pathway in rat placentas was activated. Our study demonstrated that gestational exposure to cyfluthrin leads to placental developmental disorder, which might be associated with ER stress-mediated PERK signaling pathway.

Paternal epigenetic influences on placental health and their impacts on offspring development and disease

Our efforts to understand the developmental origins of birth defects and disease have primarily focused on maternal exposures and intrauterine stressors. Recently, research into non-genomic mechanisms of inheritance has led to the recognition that epigenetic factors carried in sperm also significantly impact the health of future generations. However, although researchers have described a range of potential epigenetic signals transmitted through sperm, we have yet to obtain a mechanistic understanding of how these paternally-inherited factors influence offspring development and modify life-long health. In this endeavor, the emerging influence of the paternal epigenetic program on placental development, patterning, and function may help explain how a diverse range of male exposures induce comparable intergenerational effects on offspring health. During pregnancy, the placenta serves as the dynamic interface between mother and fetus, regulating nutrient, oxygen, and waste exchange and coordinating fetal growth and maturation. Studies examining intrauterine maternal stressors routinely describe alterations in placental growth, histological organization, and glycogen content, which correlate with well-described influences on infant health and adult onset of disease. Significantly, the emergence of similar phenotypes in models examining preconception male exposures indicates that paternal stressors transmit an epigenetic memory to their offspring that also negatively impacts placental function. Like maternal models, paternally programmed placental dysfunction exerts life-long consequences on offspring health, particularly metabolic function. Here, focusing primarily on rodent models, we review the literature and discuss the influences of preconception male health and exposure history on placental growth and patterning. We emphasize the emergence of common placental phenotypes shared between models examining preconception male and intrauterine stressors but note that the direction of change frequently differs between maternal and paternal exposures. We posit that alterations in placental growth, histological organization, and glycogen content broadly serve as reliable markers of altered paternal developmental programming, predicting the emergence of structural and metabolic defects in the offspring. Finally, we suggest the existence of an unrecognized developmental axis between the male germline and the extraembryonic lineages that may have evolved to enhance fetal adaptation.

Dysregulation of Placental Lipid Hydrolysis by High-Fat/High-Cholesterol Feeding and Gestational Diabetes Mellitus in Mice

Advanced maternal age and obesity are the main risk factors to develop gestational diabetes mellitus (GDM). Obesity is a consequence of the increased storage of triacylglycerol (TG). Cytosolic and lysosomal lipid hydrolases break down TG and cholesteryl esters (CE) to release fatty acids (FA), free cholesterol, and glycerol. We have recently shown that intracellular lipases are present and active in the mouse placenta and that deficiency of lysosomal acid lipase alters placental and fetal lipid homeostasis. To date, intracellular lipid hydrolysis in GDM has been poorly studied despite the important role of FA in this condition. Therefore, we hypothesized that intracellular lipases are dysregulated in pregnancies complicated by maternal high-fat/high-cholesterol (HF/HCD) feeding with and without GDM. Placentae of HF/HCD-fed mice with and without GDM were more efficient, indicating increased nutrient transfer to the fetus. The increased activity of placental CE but not TG hydrolases in placentae of dams fed HF/HCD with or without GDM resulted in upregulated cholesterol export to the fetus and placental TG accumulation. Our results indicate that HF/HCD-induced dysregulation of placental lipid hydrolysis contributes to fetal hepatic lipid accumulation and possibly to fetal overgrowth, at least in mice.

Role of microRNAs in trophoblast invasion and spiral artery remodeling: Implications for preeclampsia

It is now well-established that microRNAs (miRNAs) are important regulators of gene expression. The role of miRNAs in placental development and trophoblast function is constantly expanding. Trophoblast invasion and their ability to remodel uterine spiral arteries are essential for proper placental development and successful pregnancy outcome. Many miRNAs are reported to be dysregulated in pregnancy complications, especially preeclampsia and they exert various regulatory effects on trophoblasts. In this review, we provide a brief overview of miRNA biogenesis and their mechanism of action, as well as of trophoblasts differentiation, invasion and spiral artery remodeling. We then discuss the role of miRNAs in trophoblasts invasion and spiral artery remodeling, focusing on miRNAs that have been thoroughly investigated, especially using multiple model systems. We also discuss the potential role of miRNAs in the pathogenesis of preeclampsia.

A Uterus-Inspired Niche Drives Blastocyst Development to the Early Organogenesis

The fundamental physical features such as the mechanical properties and microstructures of the uterus need to be considered when building in vitro culture platforms to mimic the uterus for embryo implantation and further development but have long been neglected. Here, a uterus-inspired niche (UN) constructed by grafting collagen gels onto polydimethylsiloxane based on a systematic investigation of a series of parameters (varying concentrations and thicknesses of collagen gel) is established to intrinsically specify and simulate the mechanics and microstructures of the mouse uterus. This brand-new and unique system is robust in supporting embryo invasion, as evidenced by the special interaction between the embryos and the UN system and successfully promoting E3.5 embryo development into the early organogenesis stage. This platform serves as a powerful tool for developmental biology and tissue engineering.

Maternal Ezh1/2 deficiency in oocyte delays H3K27me2/3 restoration and impairs epiblast development responsible for embryonic sub-lethality in mouse

How maternal Ezh1 and Ezh2 function in H3K27 methylation in vivo in pre-implantation embryos and during embryonic development is not clear. Here, we have deleted Ezh1 and Ezh2 alone or simultaneously from mouse oocytes. H3K27me3 was absent in oocytes without Ezh2 alone, while both H3K27me2 and H3K27me3 were absent in Ezh1/Ezh2 (Ezh1/2) double knockout (KO) oocytes. The effects of Ezh1/2 maternal KO were inherited in zygotes and early embryos, in which restoration of H3K27me3 and H3K27me2 was delayed by the loss of Ezh2 alone or of both Ezh1 and Ezh2. However, the ablation of both Ezh1 and Ezh2, but not Ezh1 or Ezh2 alone, led to significantly decreased litter size due to growth retardation post-implantation. Maternal Ezh1/2 deficiency caused compromised H3K27me3 and pluripotent epiblast cells in late blastocysts, followed by defective embryonic development. By using RNA-seq, we examined crucial developmental genes in maternal Ezh1/2 KO embryos and identified 80 putatively imprinted genes. Maternal Ezh1/2-H3K27 methylation is inherited in offspring embryos and has a critical effect on fetal and placental development. Thus, this work sheds light on maternal epigenetic modifications during embryonic development.

Deoxynivalenol exposure during pregnancy has adverse effects on placental structure and immunity in mice model

Deoxynivalenol (DON), a highly prevalent food contaminant, is known to induce reproductive and immunotoxicity in humans upon exposure. The present study focused on the consequences of exposure to DON during pregnancy for placental barrier and immune function, as well as fetal survival. Female mice received diets contaminated with DON (6.25 and 12.5 mg/kg of diet), starting immediately after mating until the end of the experiment. On day 17 of pregnancy the animals were killed, and maternal and fetal samples were collected for further analysis. Feeding on DON-contaminated diets decreased fetal survival, and DON was detected at significant levels in the fetus. Placentae from DON-exposed mice revealed a reduction in expression of junctional proteins, ZO-1, E-cadherin and claudins, upregulation of AHR mRNA expressions, and increase in IFN-ꝩ, IL-6 and IL-4 production. In conclusion, results of this study demonstrate harmful effects of DON on the course of pregnancy and fetal survival, which might be due to immunological changes in maternal immune organs and placenta. Altogether, these data underline the importance of the quality of maternal diet during pregnancy as they clearly demonstrate the potential harmful effects of a commonly present food-contaminant.

Abnormal growth and morphogenesis of placenta at term is linked to adverse fetal development after perigestational alcohol consumption up to early gestation in mouse

BACKGROUND

Gestation alcohol consumption produces fetal growth restriction and malformations by affecting the embryo-fetal development. Recently a relationship between abnormal placentation and fetal malformation and intrauterine growth retardation has been suggested. However, the effects of perigestational alcohol ingestion up to early pregnancy on the placenta at term and its association with fetal abnormalities are little known.

METHODS

In female mice, ethanol 10% in water was administered for 15 days previous and up to days 4 (D4), 8 (D8), or 10 (D10) of gestation (TF), and gestation continues without ethanol exposure. Control females (CF) received ethanol-free water. At day 18, feto-placental units and implantation sites were studied.

RESULTS

TF had increased resorptions and only fetuses from D8-TF and D10-TF had significantly increased weights versus CF. D4 and D10-TF-placentas had significantly reduced weights. All TF had increased junctional zone (JZ) and reduced labyrinth (Lab) areas (PAS-histology and morphometry) compared with CF. Fetuses with mainly with craniofacial abnormalities and skeletal defects (Alizarin red staining), significantly increase; while the fetal bone density (alizarin color intensity, ImageJ) was reduced in D4, D8 and D10-TF versus CF. Although all TF-placentas were histo-structural affected, TF-abnormal fetuses had the most severe placental anomalies, with junctional abundant glycogenic cells into the labyrinth, disorganized labyrinthine vascularization with signs of leukocyte infiltrates and feto-maternal blood mix.

CONCLUSIONS

Perigestational alcohol consumption up to early gestation induces at term fetal growth alterations, dysmorphology and defective skeleton, linked to deficient growth and abnormal morphogenesis of placenta, highlighting insight into the prenatal etiology of FASD.

Mice lacking DCAF2 in placenta die at the gastrulation stage

UV-damaged DNA-binding protein 1 (DDB1) and cullin 4-associated factor 2 (DCAF2, also known as DTL or CDT2) is an evolutionarily highly conserved substrate recognition factor in the cullin 4 RING E3 ubiquitin ligase (CRL4) complex. This complex degrades multiple DNA replication and cell cycle-associated proteins to maintain genome stability. To clarify the function of DCAF2 in vivo, we used Cre recombinase driven by the Elf5 promoter to generate knockout mouse model that was specifically deleted Dcaf2 in the trophoblast lineage (Elf5-Cre; Dcaf2^fl/fl, Dcaf2 cKO). Here, we show that mice with the genotype Elf5-Cre; Dcaf2^fl/+ are normal and fertile. However, after mating of Elf5-Cre; Dcaf2^fl/+ mice with Dcaf2^fl/fl, no Dcaf2 cKO pups were born. Timed pregnancy studies have shown that Dcaf2 cKO mice developed abnormally on embryonic day 5.5 and died at gastrulation stage. It is worth noting that the extraembryonic ectoderm of Dcaf2 cKO mice is severely reduced or missing and leading to embryonic death. We also proved that stronger DNA damage accumulated in the trophoblastic cells of Dcaf2 cKO mice at E8.5. In addition, higher expression of Caspase-3 was found in the embryonic and trophoblastic cells of these cKO mice. In general, our research shows that the placental DCAF2 is crucial to the formation of gastrula.

Mid-pregnancy poly(I:C) viral mimic disrupts placental ABC transporter expression and leads to long-term offspring motor and cognitive dysfunction

Limited information is available about the effect of mid-pregnancy viral infections on the placental expression of efflux transporters and offspring behavior. We hypothesized that maternal exposure to polyinosinic-polycytidylic acid [poly(I:C)], a synthetic double-stranded RNA viral mimic, would impair placental cell turnover, the expression of selected ABC transporters and adult offspring behavior. C57BL/6 mice were administered poly(I:C) (10 mg/Kg;ip) or vehicle at gestational day (GD) 13.5 (mid-pregnancy). Dams were euthanized for blood collection 4 h after injection, fetal and placental collection at GD18.5 or allowed to deliver spontaneously at term. At GD 13.5, poly(I:C) induced an acute pro-inflammatory response characterized by an increase in maternal plasma levels of IL-6, CXCL-1 and CCL-2/MCP-1. At GD 18.5, poly(I:C) decreased cell proliferation/death in the labyrinthine and increased cell death in the junctional zones, characterizing a disruption of placental cell turnover. Abca1 and Abcg1 immunolabelling was decreased in the labyrinthine zone, whereas Abca1, Abcg1 and breast cancer resistance transporter (Bcrp) expression increased in the junctional zone. Moreover, adult offspring showed motor and cognitive impairments in the Rotarod and T-water maze tests. These results indicate that viral infection during mid-pregnancy may disrupt relevant placental efflux transporters, as well as placental cell turnover and offspring behavior in adult life.

Embryonic vascular establishment requires protein C receptor-expressing endothelial progenitors

Vascular establishment is one of the early events in embryogenesis. It is believed that vessel-initiating endothelial progenitors cluster to form the first primitive vessel. Understanding the molecular identity of these progenitors is crucial in order to elucidate lineage hierarchy. In this study, we identify protein C receptor (Procr) as an endothelial progenitor marker and investigate the role of Procr+ progenitors during embryonic vascular development. Using a ProcrmGFP-2A-lacZ reporter, we reveal a much earlier Procr expression (embryonic day 7.5) than previously acknowledged (embryonic day 13.5). Genetic fate-mapping experiments using ProcrCre and ProcrCreER demonstrate that Procr+ cells give rise to blood vessels throughout the entire embryo proper. Single-cell RNA-sequencing analyses place Procr+ cells at the start of endothelial commitment and maturation. Furthermore, targeted ablation of Procr+ cells results in failure of vessel formation and early embryonic lethality. Notably, genetic fate mapping and scRNA-seq pseudotime analysis support the view that Procr+ progenitors can give rise to hemogenic endothelium. In this study, we establish a Procr expression timeline and identify Procr+ vessel-initiating progenitors, and demonstrate their indispensable role in establishment of the vasculature during embryo development.

A Single-Cell Characterization of Human Post-implantation Embryos Cultured In Vitro Delineates Morphogenesis in Primary Syncytialization

Implantation of the human blastocyst is a milestone event in embryonic development. The trophoblast is the first cell lineage to differentiate during implantation. Failures in trophoblast differentiation during implantation are correlated to the defects of pregnancy and embryonic growth. However, many gaps remain in the knowledge of human embryonic development, especially regarding trophoblast morphogenesis and function. Herein, we performed single-cell RNA sequencing (scRNA-seq) analysis on human post-implantation embryos cultured in vitro. A hierarchical model was established, which was characterized by the sequential development of two primitive cytotrophoblast cell (pCTB) subtypes, two primitive syncytiotrophoblast subtypes, and migrative trophoblast cells (MTB) after the trophectoderm . Further analysis characterized cytoskeleton transition of trophoblast cells and morphogenesis, such as irregular nuclei, cell cycle arrest, and cellular aging during implantation. Moreover, we found syncytialization of hTSCs could mimic the morphogenesis, serving as a powerful tool for further understanding of the mechanism during the implantation stage of pregnancy. Our work allows for the reconstruction of trophoblast cell transcriptional transition and morphogenesis during implantation and provides a valuable resource to study pathologies in early pregnancy, such as recurrent implantation failure.

Transcription factor networks in trophoblast development

The placenta sustains embryonic development and is critical for a successful pregnancy outcome. It provides the site of exchange between the mother and the embryo, has immunological functions and is a vital endocrine organ. To perform these diverse roles, the placenta comprises highly specialized trophoblast cell types, including syncytiotrophoblast and extravillous trophoblast. The coordinated actions of transcription factors (TFs) regulate their emergence during development, subsequent specialization, and identity. These TFs integrate diverse signaling cues, form TF networks, associate with chromatin remodeling and modifying factors, and collectively determine the cell type-specific characteristics. Here, we summarize the general properties of TFs, provide an overview of TFs involved in the development and function of the human trophoblast, and address similarities and differences to their murine orthologs. In addition, we discuss how the recent establishment of human in vitro models combined with -omics approaches propel our knowledge and transform the human trophoblast field.

Inflammatory responses in the placenta upon SARS-CoV-2 infection late in pregnancy

The effect of SARS-CoV-2 infection on placental function is not well understood. Analysis of placentas from women who tested positive at delivery showed SARS-CoV-2 genomic and subgenomic RNA in 22 out of 52 placentas. Placentas from two mothers with symptomatic COVID-19 whose pregnancies resulted in adverse outcomes for the fetuses contained high levels of viral Alpha variant RNA. The RNA was localized to the trophoblasts that cover the fetal chorionic villi in direct contact with maternal blood. The intervillous spaces and villi were infiltrated with maternal macrophages and T cells. Transcriptome analysis showed an increased expression of chemokines and pathways associated with viral infection and inflammation. Infection of placental cultures with live SARS-CoV-2 and spike protein-pseudotyped lentivirus showed infection of syncytiotrophoblast and, in rare cases, endothelial cells mediated by ACE2 and Neuropilin-1. Viruses with Alpha, Beta, and Delta variant spikes infected the placental cultures at significantly greater levels.

The Regulatory Roles of Chemerin-Chemokine-Like Receptor 1 Axis in Placental Development and Vascular Remodeling During Early Pregnancy

Chemerin is an adipokine that regulates metabolism in pregnancy. An elevation of serum chemerin level is associated with pregnancy complications. Consistently, we demonstrated that the chemerin expression was increased in placenta of preeclamptic patients at deliveries. The G protein-coupled receptor chemokine-like receptor 1 (CMKLR1) mediates the actions of chemerin. The functions of the chemerin-CMKLR1 axis in maintaining pregnancy are still unknown. In this study, we demonstrated that CMKLR1 was expressed in the decidual natural killer (dNK) cells and chorionic villi of human. Chemerin suppressed the proliferation of the dNK cells in vitro. Specific antagonist of CMKLR1, α-Neta abolished the suppressive effect of spent medium from chemerin-treated dNK cells culture on extravillous trophoblast invasion. Activation of the chemerin-CMKLR1 axis promoted fusion and differentiation of human cytotrophoblast to syncytiotrophoblast in vitro. We generated Cmklr1 knockout mice and showed that the Cmklr1 deficiency negatively affected pregnancy outcome in terms of number of implantation sites, litter size and fetal weight at birth. Histologically, the Cmklr1 deficiency impaired formation of the syncytiotrophoblast layer II, induced enlargement of the maternal lacunae in the labyrinth, increased the diameter of the spiral arteries and increased trophoblast invasion in the decidua. The Cmklr1 deficient placenta also displayed an increased number of dNK cells and serum IL-15 level. In summary, the chemerin-CMKLR1 axis regulated placental development and spiral artery remodeling in early pregnancy.

Molecular regulation of trophoblast stem cell self-renewal and giant cell differentiation by the Hippo components YAP and LATS1

Background

Trophoblast stem cells (TSCs), the precursors of trophoblast cells of placenta, possess the potential to differentiate into various trophoblastic subtypes in vitro. Establishment of extraembryonic trophoblastic lineage is preceded by the “outside versus inside” positional information in preimplantation embryos, critically synchronized by the Hippo components. Abundant expression of Hippo effector YAP in TSCs and differentiated cells with paucity of information on Hippo regulation of TSC proliferation/differentiation led us test the hypothesis that Hippo dynamics is one of the regulators of  TSC proliferation/differentiation.

Methods

Blastocyst-derived murine TSCs were used. Dynamics of Hippo components were analyzed using immunofluorescence, western blotting, immunoprecipitation, qRT-PCR. Interaction studies were performed using full-length and deletion constructs. BrdU incorporation assay, flow cytometry-based polyploidy analysis and confocal microscopy were used to decipher the underlying mechanism.

Results

YAP translocates to the nucleus in TSCs and utilizes its WW₂ domain to interact with the PPQY motif of the stemness factor, CDX2. YAP limits TSC proliferation with associated effect on CDX2 target CyclinD1. Trophoblast giant cells (TGC) differentiation is associated with cytoplasmic retention of YAP, heightened pYAP^Ser127, decrease in the level of the core Hippo component, LATS1, which thereby impedes LATS1-LIMK2 association. Decreased LATS1-LIMK2 complex formation in TGCs was associated with elevated pLIMK2^Thr505 as well as its target pCOFILIN^Ser3. Precocious overexpression of LATS1 during trophoblast differentiation decreased TGC marker, Prl2c2, diminished pLIMK2^Thr505 and inactive COFILIN (pCOFILIN^Ser3) while COFILIN-phosphatase, CHRONOPHIN remained unchanged. LATS1 overexpression inhibited trophoblast endoreduplication with smaller-sized TGC-nuclei, lower ploidy level and disintegrated actin filaments. Inhibition of LIMK2 activity recapitulated the effects of LATS1 overexpression in trophoblast cells.

Conclusion

These results unveil a multilayered regulation of trophoblast self-renewal and differentiation by the Hippo components.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02844-w.

Screening of Organophosphate Flame Retardants with Placentation-Disrupting Effects in Human Trophoblast Organoid Model and Characterization of Adverse Pregnancy Outcomes in Mice

BACKGROUND

Abnormal placental development may result in adverse pregnancy outcomes and metabolic diseases in adulthood; however, it remains unknown whether and how xenobiotics affect human placentation.

OBJECTIVES

This study aimed to screen and identify placentation-disrupting chemicals in commonly used organophosphate flame retardants (OPFRs) and, if identified, to investigate potential adverse effects on placentation in relation to adverse pregnancy outcomes and metabolic disorder in offspring in mice.

METHODS

We devised a high-throughput immunofluorescence screening assay based on human trophoblast organoids and used it to screen OPFRs that inhibit the proliferation of organoids. One identified chemical was assessed for its effects on placentation by evaluating villous cytotrophoblasts, syncytiotrophoblasts, and extravillous trophoblasts using immunofluorescence and a mitochondrial stress test after 2 d of exposure. A 10-d exposure study was further performed to observe the dynamic effect of the OPFR on the structure of the organoids. RNA-sequencing and western blotting experiments were performed to explore the associated pathways, and a potential binding protein was identified by immunoprecipitation and in vitro kinase activity assays. Animal studies were performed to determine whether the findings in organoids could be replicated in mice and to observe adverse pregnancy outcomes.

RESULTS

The proliferation of organoids exposed to three aryl-OPFRs was significantly lower than the proliferation of control organoids. Further analysis demonstrated that one such chemical, 2-ethylhexyl-diphenyl phosphate (EHDPP), disrupted placentation in organoids. Mechanistically, EHDPP interfered with insulin-like growth factor 1 receptor (IGF1R) to inhibit aerobic respiration. Mice exposed to EHDPP at a physiological human concentrations exhibited immature and mature placental disorders, which correlated with fetal growth restriction, implantation failure, stillbirth, and impaired glucose tolerance.

CONCLUSIONS

The human trophoblast organoid model showed that the commonly used OPFRs disrupted placentation via IGF1R, indicating that its use may contribute to adverse pregnancy outcomes and metabolic disorders in offspring. https://doi.org/10.1289/EHP10273.

Programming of cardiometabolic health: the role of maternal and fetal hyperinsulinaemia

Obesity and gestational diabetes during pregnancy have multiple short- and long-term consequences for both mother and child. One common feature of pregnancies complicated by maternal obesity and gestational diabetes is maternal hyperinsulinaemia, which has effects on the mother and her adaptation to pregnancy. Even though insulin does not cross the placenta insulin can act on the placenta as well affecting placental growth, angiogenesis and lipid metabolism. Obese and gestational diabetic pregnancies are often characterised by maternal hyperglycaemia resulting in exposure of the fetus to high levels of glucose, which freely crosses the placenta. This leads to stimulation of fetal ß-cells and insulin secretion in the fetus. Fetal hyperglycaemia/hyperinsulinaemia has been shown to cause multiple complications in fetal development, such as altered growth trajectories, impaired neuronal and cardiac development and early exhaustion of the pancreas. These changes could increase the susceptibility of the offspring to develop cardiometabolic diseases later in life. In this review, we aim to summarize and review the mechanisms by which maternal and fetal hyperinsulinaemia impact on (i) maternal health during pregnancy; (ii) placental and fetal development; (iii) offspring energy homeostasis and long-term cardiometabolic health; (iv) how interventions can alleviate these effects.

Keratin filaments mediate the expansion of extra-embryonic membranes in the post-gastrulation mouse embryo

Mesoderm arises at gastrulation and contributes to both the mouse embryo proper and its extra-embryonic membranes. Two-photon live imaging of embryos bearing a keratin reporter allowed recording filament nucleation and elongation in the extra-embryonic region. Upon separation of amniotic and exocoelomic cavities, keratin 8 formed apical cables co-aligned across multiple cells in the amnion, allantois, and blood islands. An influence of substrate rigidity and composition on cell behavior and keratin content was observed in mesoderm explants. Embryos lacking all keratin filaments displayed a deflated extra-embryonic cavity, a narrow thick amnion, and a short allantois. Single-cell RNA sequencing of sorted mesoderm cells and micro-dissected amnion, chorion, and allantois, provided an atlas of transcriptomes with germ layer and regional information. It defined the cytoskeleton and adhesion expression profile of mesoderm-derived keratin 8-enriched cells lining the exocoelomic cavity. Those findings indicate a novel role for keratin filaments in the expansion of extra-embryonic structures and suggest mechanisms of mesoderm adaptation to the environment.

Interplay between HTRA1 and classical signalling pathways in organogenesis and diseases

The high temperature requirement factor A1 (HTRA1) is a serine protease which modulates an array of signalling pathways driving basal biological processes. HTRA1 plays a significant role in cell proliferation, migration and fate determination, in addition to controlling protein aggregates through refolding, translocation or degradation. The mutation of HTRA1 has been implicated in a plethora of disorders and this has also led to its growing interest as drug therapy target. This review details the involvement of HTRA1 in certain signalling pathways, namely the transforming growth factor beta (TGF-β), canonical Wingless/Integrated (WNT) and NOTCH signalling pathways during organogenesis and various disease pathogenesis such as preeclampsia, age-related macular degeneration (AMD), small vessel disease and cancer. We have also explored possible avenues of exploiting the serine proteases for therapeutic management of these disorders.

Thyroid hormone enhances stem cell maintenance and promotes lineage-specific differentiation in human embryonic stem cells

Background

Thyroid hormone triiodothyronine (T3) is essential for embryogenesis and is commonly used during in vitro fertilization to ensure successful implantation. However, the regulatory mechanisms of T3 during early embryogenesis are largely unknown.

Method

To study the impact of T3 on hPSCs, cell survival and growth were evaluated by measurement of cell growth curve, cloning efficiency, survival after passaging, cell apoptosis, and cell cycle status. Pluripotency was evaluated by RT-qPCR, immunostaining and FACS analysis of pluripotency markers. Metabolic status was analyzed using LC–MS/MS and Seahorse XF Cell Mito Stress Test. Global gene expression was analyzed using RNA-seq. To study the impact of T3 on lineage-specific differentiation, cells were subjected to T3 treatment during differentiation, and the outcome was evaluated using RT-qPCR, immunostaining and FACS analysis of lineage-specific markers.

Results

In this report, we use human pluripotent stem cells (hPSCs) to show that T3 is beneficial for stem cell maintenance and promotes trophoblast differentiation. T3 enhances culture consistency by improving cell survival and passaging efficiency. It also modulates cellular metabolism and promotes energy production through oxidative phosphorylation. T3 helps maintain pluripotency by promoting ERK and SMAD2 signaling and reduces FGF2 dependence in chemically defined culture. Under BMP4 induction, T3 significantly enhances trophoblast differentiation.

Conclusion

In summary, our study reveals the impact of T3 on stem cell culture through signal transduction and metabolism and highlights its potential role in improving stem cell applications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02799-y.

Maternal Prepregnancy 5-Hydroxytryptamine Exposure Affects the Early Development of the Fetus

In recent decades, the increasing incidence of depression has contributed to an increase in the use of serotonergic drugs, such as antidepressants, which predisposes humans to serotonin syndrome. Serotonin syndrome is caused by elevated serotonin levels in the central and peripheral nervous systems. It has been well documented that the development of offspring can be affected by maternal exposure to environmental challenges, such as stress, diseases, or an unhealthy diet during pregnancy. Serotonin, also called 5-hydroxytryptamine (5-HT), is widely expressed in the female reproductive system and plays an important role in the development of follicles and embryos. However, whether the suffering of the mother from serotonin syndrome before pregnancy affects fetal development is still uncertain. In the present study, to explore the effect of maternal prepregnancy 5-HT exposure on the fetus, intraperitoneal injection of 5-HT was used to change maternal prepregnancy 5-HT levels. It was found that maternal prepregnancy 5-HT exposure significantly reduced the body weight and liver weight and the levels of estrogen and progesterone in female mice. Although there was no significant difference in the cleavage rate and blastocyst rate between the 5-HT and control groups, maternal prepregnancy 5-HT exposure increased the percentage of embryo resorption, decreased placental weight, and led to placental inflammation at E13.5. Notably, 5-HT exposure caused weight loss in the offspring at 2 weeks. These results suggested that maternal prepregnancy 5-HT exposure could affect the development of the offspring, which was partly caused by reduced hormonal secretion and placental inflammation.

Progesterone Attenuates SIRT1-Deficiency-Mediated Pre-Eclampsia

Pre-eclampsia is a severe hypertensive disorder of pregnancy (HDP), mainly characterized by new-onset hypertension with proteinuria after 20-week gestation. Sirtuin1 (SIRT1), a class III histone deacetylase, is associated with the regulation of various pathophysiological processes, including inflammation, immune response, metabolism, and autophagy. However, the effect of SIRT1 in the pathogenesis of pre-eclampsia remains to be elucidated. In this study, we found that the expression of SIRT1 was relatively lower in the placentas and serum samples of pre-eclampsia patients. Typical pre-eclampsia-like symptoms, such as hypertension, proteinuria, fetal growth restriction, kidney injury, and a narrow placental labyrinth layer, were observed in SIRT1 knockdown (SIRT1^+/−) mice. Of note, these performances could be improved after the intraperitoneal injection of SIRT1 agonist SRT2104. More importantly, we found that the efficacy of progesterone on attenuating symptoms of PE was profoundly better than that of metformin in SIRT1^+/− mice. In addition, our results suggested that progesterone can promote the invasion and inhibit the apoptosis of trophoblasts. These data suggest that SIRT1 plays an important role in pre-eclampsia and that progesterone alleviates pre-eclampsia-like symptoms mediated by SIRT1 deficiency.

Exposure to two-dimensional ultrathin Ti3C2 (MXene) nanosheets during early pregnancy impairs neurodevelopment of offspring in mice

Background

Two-dimensional ultrathin Ti₃C₂ (MXene) nanosheets have been extensively explored for various biomedical applications. However, safety issues and the effects of Ti₃C₂ on human health remain poorly understood.

Results

To explore the influence on foetal or offspring after exposure to Ti₃C₂ nanosheets, we established a mouse model exposed to different doses of Ti₃C₂ nanosheets during early pregnancy in this study. We found that Ti₃C₂ nanosheets had negligible effect on the reproductive ability of maternal mice, including average pregnancy days, number of new-borns, and neonatal weight, etc. Unexpectedly, abnormal neurobehavior and pathological changes in the cerebral hippocampus and cortex in adult offspring were observed following Ti₃C₂ nanosheet treatment. In further studies, it was found that Ti₃C₂ exposure led to developmental and functional defects in the placenta, including reduced area of labyrinth, disordered secretion of placental hormones, and metabolic function derailment. The long-chain unsaturated fatty acids were significantly higher in the placenta after Ti₃C₂ exposure, especially docosahexaenoic acid (DHA) and linoleic acid. The metabolic pathway analysis showed that biosynthesis of unsaturated fatty acids was upregulated while linoleic acid metabolism was downregulated.

Conclusions

These developmental and functional defects, particularly metabolic function derailment in placenta may be the cause for the neuropathology in the offspring. This is the first report about the effects of Ti₃C₂ nanosheet exposure on pregnancy and offspring. The data provides a better understanding of Ti₃C₂ nanosheets safety. It is suggested that future studies should pay more attention to the long-term effects of nanomaterials exposure, including the health of offspring in adulthood, rather than only focus on short-term effects, such as pregnancy outcomes. Metabolomics could provide clues for finding the prevention targets of the biological negative effect of Ti₃C₂ nanosheets.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01313-z.

Vaginal Exposure to Candida albicans During Early Gestation Results in Adverse Pregnancy Outcomes via Inhibiting Placental Development

Vulvovaginal candidiasis (VVC) is considered the second most common cause of vaginitis after bacterial vaginosis and the most common lower genital tract infection during pregnancy. Candida albicans (C. albicans), an opportunistic pathogen, is the major species causing VVC. Recently, increasing researches have shown that lower reproductive tract infection during pregnancy can lead to various adverse pregnancy outcomes. However, the underlying mechanisms are not fully understood. Hence, we successfully established a mouse model of vaginal C. albicans infection and characterized the adverse pregnancy outcomes. C. albicans infection strikingly increased abortion rate and decreased litter size. Further analysis of placental development demonstrated that placental structure was abnormal, including that the area of spongiotrophoblast (Spo) and labyrinth (Lab) was reduced, and the formation of placental vessel was decreased in Lab zone. Accordingly, the expression of marker genes during placental development was downregulated. Collectively, the above findings revealed that vaginal C. albicans infection during pregnancy can inhibit placental development and ultimately lead to adverse pregnancy outcomes. This study enhances our comprehension of the effect of VVC on pregnancy, and placental dysplasia as a feasible orientation to explore VVC during pregnancy.

Maternal but not fetoplacental health can be improved by metformin in a murine diet-induced model of maternal obesity and glucose intolerance

Maternal obesity is a global problem that increases the risk of short- and long-term adverse outcomes for mother and child, many of which are linked to gestational diabetes mellitus. Effective treatments are essential to prevent the transmission of poor metabolic health from mother to child. Metformin is an effective glucose lowering drug commonly used to treat gestational diabetes mellitus; however, its wider effects on maternal and fetal health are poorly explored. In this study we used a mouse (C57Bl6/J) model of diet-induced (high sugar/high fat) maternal obesity to explore the impact of metformin on maternal and feto-placental health. Metformin (300 mg kg-1  day-1 ) was given to obese females via the diet and was shown to achieve clinically relevant concentrations in maternal serum (1669 ± 568 nM in late pregnancy). Obese dams developed glucose intolerance during pregnancy and had reduced uterine artery compliance. Metformin treatment of obese dams improved maternal glucose tolerance, reduced maternal fat mass and restored uterine artery function. Placental efficiency was reduced in obese dams, with increased calcification and reduced labyrinthine area. Consequently, fetuses from obese dams weighed less (P < 0.001) at the end of gestation. Despite normalisation of maternal parameters, metformin did not correct placental structure or fetal growth restriction. Metformin levels were substantial in the placenta and fetal circulation (109.7 ± 125.4 nmol g-1 in the placenta and 2063 ± 2327 nM in fetal plasma). These findings reveal the distinct effects of metformin administration during pregnancy on mother and fetus and highlight the complex balance of risk vs. benefits that are weighed in obstetric medical treatments. KEY POINTS: Maternal obesity and gestational diabetes mellitus have detrimental short- and long-term effects for mother and child. Metformin is commonly used to treat gestational diabetes mellitus in many populations worldwide but the effects on fetus and placenta are unknown. In a mouse model of diet-induced obesity and glucose intolerance in pregnancy we show reduced uterine artery compliance, placental structural changes and reduced fetal growth. Metformin treatment improved maternal metabolic health and uterine artery compliance but did not rescue obesity-induced changes in the fetus or placenta. Metformin crossed the placenta into the fetal circulation and entered fetal tissue. Metformin has beneficial effects on maternal health beyond glycaemic control. However, despite improvements in maternal physiology, metformin did not prevent fetal growth restriction or placental ageing. The high uptake of metformin into the placental and fetal circulation highlights the potential for direct immediate effects of metformin on the fetus with possible long-term consequences postnatally.