Changes in vitelline and utero-placental hemodynamics: implications for cardiovascular development

Origin and flow-mediated remodeling of the murine and human extraembryonic circulation systems

The transduction of mechanical stimuli produced by blood flow is an important regulator of vascular development. The vitelline and umbilico-placental circulations are extraembryonic vascular systems that are required for proper embryonic development in mammalian embryos. The morphogenesis of the extraembryonic vasculature and the cardiovascular system of the embryo are hemodynamically and molecularly connected. Here we provide an overview of the establishment of the murine and human vitelline and umbilico-placental vascular systems and how blood flow influences various steps in their development. A deeper comprehension of extraembryonic vessel development may aid the establishment of stem-cell based embryo models and provide novel insights to understanding pregnancy complications related to the umbilical cord and placenta.

Atlas of fetal metabolism during mid-to-late gestation and diabetic pregnancy

Mounting evidence suggests metabolism instructs stem cell fate decisions. However, how fetal metabolism changes during development and how altered maternal metabolism shapes fetal metabolism remain unexplored. We present a descriptive atlas of in vivo fetal murine metabolism during mid-to-late gestation in normal and diabetic pregnancy. Using 13C-glucose and liquid chromatography-mass spectrometry (LC-MS), we profiled the metabolism of fetal brains, hearts, livers, and placentas harvested from pregnant dams between embryonic days (E)10.5 and 18.5. Our analysis revealed metabolic features specific to a hyperglycemic environment and signatures that may denote developmental transitions during euglycemic development. We observed sorbitol accumulation in fetal tissues and altered neurotransmitter levels in fetal brains isolated from hyperglycemic dams. Tracing 13C-glucose revealed disparate fetal nutrient sourcing depending on maternal glycemic states. Regardless of glycemic state, histidine-derived metabolites accumulated in late-stage fetal tissues. Our rich dataset presents a comprehensive overview of in vivo fetal tissue metabolism and alterations due to maternal hyperglycemia.

Fetal Aortic and Umbilical Doppler Flow Velocity Waveforms in Pregnancy: The Concept of Aortoumbilical Column

Low impedance within the uteroplacental circulation is crucial for fetal development. Flow velocity waveforms (FVW) have been established for the aortic and umbilical arteries in low-risk pregnancies during the second half of pregnancy, but data regarding early gestation is limited. Both vascular territories exhibit higher impedance patterns in pregnancies complicated by fetal growth restriction (FGR), hypertensive disorders, fetal anemia, and chromosomal abnormalities. Early identification of these complications is critical in obstetric practice, to reduce perinatal morbidity and mortality through prevention and close antenatal surveillance. Available data suggest that aortic and umbilical impedances follow the same variation pattern as pregnancy progresses. This observation implies that both vessels may be considered as a single artery, referred to as the "aortoumbilical column". Our hypothesis posits that changes in the hemodynamic pattern of this column could identify high-risk pregnancies, particularly those complicated by preeclampsia, FGR, intrauterine fetal demise, fetal aneuploidies, and fetal anemia. Understanding vascular embryogenesis and the FVWs of the aortic and umbilical arteries enables comprehension of impedance changes throughout normal pregnancies. The continuous variation in impedance along a single vessel supports our concept of the aortoumbilical column. Deviations from the regular pattern could assist in identifying compromised fetuses during early pregnancy. Further research on normal aortoumbilical column FVW and the development of reference charts is necessary to consider this arterial column as a screening tool in clinical practice.

Additional Anomalies in Children with Gastroschisis and Omphalocele: A Retrospective Cohort Study

BACKGROUND

Congenital abdominal wall defects might be associated with other anomalies, such as atresia in gastroschisis and cardiac anomalies in omphalocele patients. However, in the current literature, an overview of these additional anomalies and potential patient-specific risk factors is missing. Therefore, we aimed to assess the prevalence of associated anomalies and their patient-specific risk factors in patients with gastroschisis and omphalocele.

METHODS

A mono-center retrospective cohort study between 1997 and 2023 was performed. Outcomes were the presence of any additional anomalies. Risk factors were analyzed via logistic regression analysis.

RESULTS

In total, 122 patients were included, of whom 82 (67.2%) had gastroschisis, and 40 (32.8%) had omphalocele. Additional anomalies were identified in 26 gastroschisis patients (31.7%) and in 27 omphalocele patients (67.5%). In patients with gastroschisis, intestinal anomalies were most identified (n = 13, 15.9%), whereas, in patients with omphalocele, cardiac anomalies were most identified (n = 15, 37.5%). Logistic regression showed that cardiac anomalies were associated with complex gastroschisis (OR: 8.5; CI-95%: 1.4-49.5).

CONCLUSIONS

In patients with gastroschisis and omphalocele, intestinal and cardiac anomalies were most identified, respectively. Cardiac anomalies were found to be a risk factor for patients with complex gastroschisis. Therefore, regardless of the type of gastroschisis and/or omphalocele, postnatal cardiac screening remains important.

Environmental Exposures and Congenital Heart Disease

Congenital heart disease (CHD) is the most common congenital abnormality worldwide, affecting 8 to 12 infants per 1000 births globally and causing >40% of prenatal deaths. However, its causes remain mainly unknown, with only up to 15% of CHD cases having a determined genetic cause. Exploring the complex relationship between genetics and environmental exposures is key in understanding the multifactorial nature of the development of CHD. Multiple population-level association studies have been conducted on maternal environmental exposures and their association with CHD, including evaluating the effect of maternal disease, medication exposure, environmental pollution, and tobacco and alcohol use on the incidence of CHD. However, these studies have been done in a siloed manner, with few examining the interplay between multiple environmental exposures. Here, we broadly and qualitatively review the current literature on maternal and paternal prenatal exposures and their association with CHD. We propose using the framework of the emerging field of the exposome, the environmental complement to the genome, to review all internal and external prenatal environmental exposures and identify potentiating or alleviating synergy between exposures. Finally, we propose mechanistic pathways through which susceptibility to development of CHD may be induced via the totality of prenatal environmental exposures, including the interplay between placental and cardiac development and the internal vasculature and placental morphology in early stages of pregnancy.

Generation of Pericytic-Vascular Progenitors from Tankyrase/PARP-Inhibitor-Regulated Naïve (TIRN) Human Pluripotent Stem Cells

Tankyrase/PARP inhibitor-regulated naïve human pluripotent stem cells (TIRN-hPSC) represent a new class of human stem cells for regenerative medicine that can differentiate into multi-lineage progenitors with improved in vivo functionality. Chemical reversion of conventional, primed hPSC to a TIRN-hPSC state alleviates dysfunctional epigenetic donor cell memory, lineage-primed gene expression, and potentially disease-associated aberrations in their differentiated progeny. Here, we provide methods for the reversion of normal or diseased patient-specific primed hPSC to TIRN-hPSC and describe their subsequent differentiation into embryonic-like pericytic-endothelial "naïve" vascular progenitors (N-VP). N-VP possess improved vascular functionality, high epigenetic plasticity, maintain greater genomic stability, and are more efficient in migrating to and re-vascularizing ischemic tissues than those generated from primed isogenic hPSC. We also describe detailed methods for the ocular transplantation and quantitation of vascular engraftment of N-VP into the ischemia-damaged neural retina of a humanized mouse model of ischemic retinopathy. The application of TIRN-hPSC-derived N-VP will advance vascular cell therapies of ischemic retinopathy, myocardial infarction, and cerebral vascular stroke.

A prospective cohort study on association of first-trimester serum biomarkers and risk of isolated foetal congenital heart defects

BACKGROUND

This study aims to assess the association between first-trimester biomarkers in foetuses with a non-chromosomal congenital heart defect (CHD) and compares it to the matched healthy foetuses.

METHOD

Nuchal Translucency (NT), Pregnancy-Associated Plasma Protein-A (PAPP-A) and free beta-human Chorionic Gonadotropin (β-hCG) were evaluated in 56 isolated foetal heart defects and 224 controls. The CHDs were further divided into Critical CHD (C-CHD) and Non-critical CHD (N-CHD) groups.

RESULTS

The multiple of the median (MoM) values for PAPP-A were significantly lower (0.87 MoM vs. 0.92 MoM; p = 0.008) in the total CHD group than in controls. The median of foetal NT values was significantly higher in the total CHDs than in controls (1.16 MoM vs. 1.03 MoM; p < 0.001), especially for C-CHDs (1.28 MoM; P < 0.001). There were no significant differences in terms of PAPP-A (p = 0.779) and foetal NT values (p = 0.760) between the N-CHDs and control groups. There were no significant differences within the groups based on free β-hCG, except for a lower β-hCG in C-CHD group than in the control group (0.95 MoM vs. 1.11 MoM; p = 0.022).

CONCLUSION

Lower PAPP-A levels and increased NT thickness were associated with an increased risk of CHDs, especially the critical type of CHDs.Clinical significanceMaternal serum PAPP-A, measured in the first trimester, is significantly lower in CHD.Foetal NT is significantly thicker in foetuses with CHD, especially those with critical CHD.Maternal serum β-hCG was only decreased among critical CHD group.

Congenital heart defects and umbilical cord abnormalities, an unknown association?

INTRODUCTION

Few studies exist that research the association between umbilical cord characteristics with cardiac malformations. In this study, we describe a population of newborns with congenital heart defects (CHD) and the frequency of presentation of umbilical cord (UC) alterations, based upon the hypothesis that the continuity of the cardio-placental circuit can be affected by similar noxas during early development.

METHODS

We carried out a descriptive study at a hospital in Bogota based on clinical records from newborns with congenital heart disease with placental and UC pathology results. Group analyses were done according to the major categories of the ICD-10.

RESULTS

We analyzed 122 cases and found that the most frequent alterations where hypercoiling (27.9%) and abnormal UC insertion (16.4%). Additionally, in almost every group of CHD, more than 65%of patients had some type of cord alteration.

CONCLUSION

We discovered a high frequency of UC alterations in patients with CHD. This outcome suggests that a possible association exists between the two phenomena, further research is needed.

A missense mutation of ErbB2 produces a novel mouse model of stillbirth associated with a cardiac abnormality but lacking abnormalities of placental structure

Background

In humans, stillbirth describes the death of a fetus before birth after 28 weeks gestation, and accounts for approximately 2.6 million deaths worldwide annually. In high-income countries, up to half of stillbirths have an unknown cause and are described as “unexplained stillbirths”; this lack of understanding impairs efforts to prevent stillbirth. There are also few animal models of stillbirth, but those that have been described usually have significant placental abnormalities. This study describes a novel mutant murine model of fetal death with atrial conduction block due to an ErbB2 missense mutation which is not associated with abnormal placental morphology.

Methods

Phenotypic characterisation and histological analysis of the mutant mouse model was conducted. The mRNA distribution of the early cardiomyocyte marker Nkx2-5 was assessed via in situ hybridisation. Cardiac structure was quantified and cellular morphology evaluated by electron microscopy. Immunostaining was employed to quantify placental structure and cell characteristics on matched heterozygous and homozygous mutant placental samples.

Results

There were no structural abnormalities observed in hearts of mutant embryos. Comparable Nkx2-5 expression was observed in hearts of mutants and controls, suggesting normal cardiac specification. Additionally, there was no significant difference in the weight, placenta dimensions, giant cell characteristics, labyrinth tissue composition, levels of apoptosis, proliferation or vascularisation between placentas of homozygous mutant mice and controls.

Conclusion

Embryonic lethality in the ErbB2 homozygous mutant mouse cannot be attributed to placental pathology. As such, we conclude the ErbB2^M802R mutant is a model of stillbirth with a non-placental cause of death. The mechanism of the atrial block resulting from ErbB2 mutation and its role in embryonic death is still unclear. Studying this mutant mouse model could identify candidate genes involved in stillbirth associated with structural or functional cardiac defects.

The Impact of Infection in Pregnancy on Placental Vascular Development and Adverse Birth Outcomes

Healthy fetal development is dependent on nutrient and oxygen transfer via the placenta. Optimal growth and function of placental vasculature is therefore essential to support in utero development. Vasculogenesis, the de novo formation of blood vessels, and angiogenesis, the branching and remodeling of existing vasculature, mediate the development and maturation of placental villi, which form the materno-fetal interface. Several lines of evidence indicate that systemic maternal infection and consequent inflammation can disrupt placental vasculogenesis and angiogenesis. The resulting alterations in placental hemodynamics impact fetal growth and contribute to poor birth outcomes including preterm delivery, small-for-gestational age (SGA), stillbirth, and low birth weight (LBW). Furthermore, pathways involved in maternal immune activation and placental vascularization parallel those involved in normal fetal development, notably neurovascular development. Therefore, immune-mediated disruption of angiogenic pathways at the materno-fetal interface may also have long-term neurological consequences for offspring. Here, we review current literature evaluating the influence of maternal infection and immune activation at the materno-fetal interface and the subsequent impact on placental vascular function and birth outcome. Immunomodulatory pathways, including chemokines and cytokines released in response to maternal infection, interact closely with the principal pathways regulating placental vascular development, including the angiopoietin-Tie-2, vascular endothelial growth factor (VEGF), and placental growth factor (PlGF) pathways. A detailed mechanistic understanding of how maternal infections impact placental and fetal development is critical to the design of effective interventions to promote placental growth and function and thereby reduce adverse birth outcomes.

The NuRD chromatin-remodeling complex enzyme CHD4 prevents hypoxia-induced endothelial Ripk3 transcription and murine embryonic vascular rupture

Physiological hypoxia can trigger transcriptional events that influence many developmental processes during mammalian embryogenesis. One way that hypoxia affects transcription is by engaging chromatin-remodeling complexes. We now report that chromodomain helicase DNA binding protein 4 (CHD4), an enzyme belonging to the nucleosome remodeling and deacetylase (NuRD) chromatin-remodeling complex, is required for transcriptional repression of the receptor-interacting protein kinase 3 (Ripk3)-a critical executor of the necroptosis cell death program-in hypoxic murine embryonic endothelial cells. Genetic deletion of Chd4 in murine embryonic endothelial cells in vivo results in upregulation of Ripk3 transcripts and protein prior to vascular rupture and lethality at midgestation, and concomitant deletion of Ripk3 partially rescues these phenotypes. In addition, CHD4 binds to and prevents acetylation of the Ripk3 promoter in cultured endothelial cells grown under hypoxic conditions to prevent excessive Ripk3 transcription. These data demonstrate that excessive RIPK3 is detrimental to embryonic vascular integrity and indicate that CHD4 suppresses Ripk3 transcription when the embryonic environment is particularly hypoxic prior to the establishment of fetal-placental circulation at midgestation. Altogether, this research provides new insights into regulators of Ripk3 transcription and encourages future studies into the mechanism by which excessive RIPK3 damages embryonic blood vessels.

Secondary Placental Defects in Cxadr Mutant Mice

The Coxsackie virus and adenovirus receptor (CXADR) is an adhesion molecule known for its role in virus-cell interactions, epithelial integrity, and organogenesis. Loss of Cxadr causes numerous embryonic defects in mice, notably abnormal development of the cardiovascular system, and embryonic lethality. While CXADR expression has been reported in the placenta, the precise cellular localization and function within this tissue are unknown. Since impairments in placental development and function can cause secondary cardiovascular abnormalities, a phenomenon referred to as the placenta-heart axis, it is possible placental phenotypes in Cxadr mutant embryos may underlie the reported cardiovascular defects and embryonic lethality. In the current study, we determine the cellular localization of placental Cxadr expression and whether there are placental abnormalities in the absence of Cxadr. In the placenta, CXADR is expressed specifically by trophoblast labyrinth progenitors as well as cells of the visceral yolk sac (YS). In the absence of Cxadr, we observed altered expression of angiogenic factors coupled with poor expansion of trophoblast and fetal endothelial cell subpopulations, plus diminished placental transport. Unexpectedly, preserving endogenous trophoblast Cxadr expression revealed the placental defects to be secondary to primary embryonic and/or YS phenotypes. Moreover, further tissue-restricted deletions of Cxadr suggest that the secondary placental defects are likely influenced by embryonic lineages such as the fetal endothelium or those within the extraembryonic YS vascular plexus.

Near to One's Heart: The Intimate Relationship Between the Placenta and Fetal Heart

The development of the fetal heart is exquisitely controlled by a multitude of factors, ranging from humoral to mechanical forces. The gatekeeper regulating many of these factors is the placenta, an external fetal organ. As such, resistance within the placental vascular bed has a direct influence on the fetal circulation and therefore, the developing heart. In addition, the placenta serves as the interface between the mother and fetus, controlling substrate exchange and release of hormones into both circulations. The intricate relationship between the placenta and fetal heart is appreciated in instances of clinical placental pathology. Abnormal umbilical cord insertion is associated with congenital heart defects. Likewise, twin-to-twin transfusion syndrome, where monochorionic twins have unequal sharing of their placenta due to inter-twin vascular anastomoses, can result in cardiac remodeling and dysfunction in both fetuses. Moreover, epidemiological studies have suggested a link between placental phenotypic traits and increased risk of cardiovascular disease in adult life. To date, the mechanistic basis of the relationships between the placenta, fetal heart development and later risk of cardiac dysfunction have not been fully elucidated. However, studies using environmental exposures and gene manipulations in experimental animals are providing insights into the pathways involved. Likewise, surgical instrumentation of the maternal and fetal circulations in large animal species has enabled the manipulation of specific humoral and mechanical factors to investigate their roles in fetal cardiac development. This review will focus on such studies and what is known to date about the link between the placenta and heart development.

Development of the Human Placenta and Fetal Heart: Synergic or Independent?

The placenta is the largest fetal organ, and toward the end of pregnancy the umbilical circulation receives at least 40% of the biventricular cardiac output. It is not surprising, therefore, that there are likely to be close haemodynamic links between the development of the placenta and the fetal heart. Development of the placenta is precocious, and in advance of that of the fetus. The placenta undergoes considerable remodeling at the end of the first trimester of pregnancy, and its vasculature is capable of adapting to environmental conditions and to variations in the blood supply received from the mother. There are two components to the placental membranes to consider, the secondary yolk sac and the chorioallantoic placenta. The yolk sac is the first of the extraembryonic membranes to be vascularized, and condensations in the mesenchyme at ~17 days post-conception (p.c.) give rise to endothelial and erythroid precursors. A network of blood vessels is established ~24 days p.c., with the vitelline vein draining through the region of the developing liver into the sinus venosus. Gestational sacs of early pregnancy failures often display aberrant development of the yolk sac, which is likely to be secondary to abnormal fetal development. Vasculogenesis occurs in the villous mesenchyme of the chorioallantoic placenta at a similarly early stage. Nucleated erythrocytes occupy the lumens of the placental capillaries and end-diastolic flow is absent in the umbilical arterial circulation throughout most of the first trimester, indicating a high resistance to blood flow. Resistance begins to fall in the umbilico-placental circulation around 12–14 weeks. During normal early pregnancy the placental capillary network is plastic, and considerable remodeling occurs in response to the local oxygen concentration, and in particular to oxidative stress. In pregnancies complicated by preeclampsia and/or fetal growth restriction, utero-placental malperfusion induces smooth muscle cells surrounding the placental arteries to dedifferentiate and adopt a proliferative phenotype. This change is associated with increased umbilical resistance measured by Doppler ultrasound, and is likely to exert a major effect on the developing heart through the afterload. Thus, both the umbilical and maternal placental circulations may impact on development of the heart.

Placentation defects are highly prevalent in embryonic lethal mouse mutants

Large-scale phenotyping efforts have demonstrated that approximately 25-30% of mouse gene knockouts cause intra-uterine lethality. Analysis of these mutants has largely focussed on the embryo but not the placenta, despite the critical role of this extra-embryonic organ for developmental progression. Here, we screened 103 embryonic lethal and subviable mouse knockout lines from the Deciphering the Mechanisms of Developmental Disorders programme (https://dmdd.org.uk) for placental phenotypes. 68% of lines that are lethal at or after mid-gestation exhibited placental dys-morphologies. Early lethality (E9.5-E14.5) is almost always associated with severe placental malformations. Placental defects strongly correlate with abnormal brain, heart and vascular development. Analysis of mutant trophoblast stem cells and conditional knockouts suggests primary gene function in trophoblast for a significant number of factors that cause embryonic lethality when ablated. Our data highlight the hugely under-appreciated importance of placental defects in contributing to abnormal embryo development and suggest key molecular nodes governing placentation.

Acute alcohol exposure during mouse gastrulation alters lipid metabolism in placental and heart development: Folate prevention

Background

Embryonic acute exposure to ethanol (EtOH), lithium, and homocysteine (HCy) induces cardiac defects at the time of exposure; folic acid (FA) supplementation protects normal cardiogenesis (Han et al., 2009, 2012; Serrano et al., 2010). Our hypothesis is that EtOH exposure and FA protection relate to lipid and FA metabolism during mouse cardiogenesis and placentation.

Methods

On the morning of conception, pregnant C57BL/6J mice were placed on either of two FA‐containing diets: a 3.3 mg health maintenance diet or a high FA diet of 10.5 mg/kg. Mice were injected a binge level of EtOH, HCy, or saline on embryonic day (E) 6.75, targeting gastrulation. On E15.5, cardiac and umbilical blood flow were examined by ultrasound. Embryonic cardiac tissues were processed for gene expression of lipid and FA metabolism; the placenta and heart tissues for neutral lipid droplets, or for medium chain acyl‐dehydrogenase (MCAD) protein.

Results

EtOH exposure altered lipid‐related gene expression on E7.5 in comparison to control or FA‐supplemented groups and remained altered on E15.5 similarly to changes with HCy, signifying FA deficiency. In comparison to control tissues, the lipid‐related acyl CoA dehydrogenase medium length chain gene and its protein MCAD were altered with EtOH exposure, as were neutral lipid droplet localization in the heart and placenta.

Conclusion

EtOH altered gene expression associated with lipid and folate metabolism, as well as neutral lipids, in the E15.5 abnormally functioning heart and placenta. In comparison to controls, the high FA diet protected the embryo and placenta from these effects allowing normal development. Birth Defects Research (Part A) 106:749–760, 2016. © 2016 The Authors Birth Defects Research Part A: Clinical and Molecular Teratology Published by Wiley Periodicals, Inc.

Probing the Electrophysiology of the Developing Heart

Many diseases that result in dysfunction and dysmorphology of the heart originate in the embryo. However, the embryonic heart presents a challenging subject for study: especially challenging is its electrophysiology. Electrophysiological maturation of the embryonic heart without disturbing its physiological function requires the creation and deployment of novel technologies along with the use of classical techniques on a range of animal models. Each tool has its strengths and limitations and has contributed to making key discoveries to expand our understanding of cardiac development. Further progress in understanding the mechanisms that regulate the normal and abnormal development of the electrophysiology of the heart requires integration of this functional information with the more extensively elucidated structural and molecular changes.

Extraembryonic but not embryonic SUMO-specific protease 2 is required for heart development

SUMO-specific protease 2 (SENP2) activities to remove SUMO from its substrates is essential for development of trophoblast stem cells, niches and lineages. Global deletion of SENP2 leads to midgestation lethality, and causes severe defects in the placenta which is accompanied by embryonic brain and heart abnormalities. Because of the placental deficiencies, the role of SENP2 in development of the embryonic tissues has not been properly determined. The brain and heart abnormalities may be secondary to placental insufficiency. Here we have created a new mouse strain permitting conditional inactivation of SENP2. Mice homozygous for germline deletion of the conditional allele exhibit trophoblast defects and embryonic abnormalities resembling the global SENP2 knockout. However, tissue-specific disruptions of SENP2 demonstrate its dispensable role in embryogenesis. Placental expression of SENP2 is necessary and sufficient for embryonic heart and brain development. Using a protease deficient model, we further demonstrate the requirement of SENP2-dependent SUMO modification in development of all major trophoblast lineages. SENP2 regulates sumoylation of Mdm2 which controls p53 activities critical for G-S transition of mitotic division and endoreduplication in trophoblast proliferation and differentiation, respectively. The differentiation of trophoblasts is also dependent on SENP2-mediated activation of p57^Kip2, a CDK-specific inhibitor required for endoreduplication.

Physiology of the fetal and transitional circulation

The fetal circulation is an entirely transient event, not replicated at any point in later life, and functionally distinct from the pediatric and adult circulations. Understanding of the physiology of the fetal circulation is vital for accurate interpretation of hemodynamic assessments in utero, but also for management of circulatory compromise in premature infants, who begin extrauterine life before the fetal circulation has finished its maturation. This review summarizes the key classical components of circulatory physiology, as well as some of the newer concepts of physiology that have been appreciated in recent years. The immature circulation has significantly altered function in all aspects of circulatory physiology. The mechanisms and significance of these differences are also discussed, as is the impact of these alterations on the circulatory transition of infants born prematurely.