Sperm intrusion into the implantation-stage blastocyst and its potential biological significance

The human embryo derives from fusion of oocyte and sperm, undergoes growth and differentiation, resulting in a blastocyst. To initiate implantation, the blastocyst hatches from the zona pellucida, allowing access from external inputs. Modelling of uterine sperm distribution indicates that 200-5000 sperm cells may reach the implantation-stage blastocyst following natural coitus. We show ultrastructural evidence of sperm cells intruding into trophectoderm cells of zona-free blastocysts obtained from the uterus of rhesus monkeys. Interaction between additional sperm and zona-free blastocyst could be an evolutionary feature yielding adaptive processes influencing the developmental fate of embryos. This process bears potential implications in pregnancy success, sperm competition and human health.

Placenta and maternal endothelium during preeclampsia: Disruption of the glycocalyx explains increased inositol phosphoglycans and angiogenic factors in maternal blood

The etiology of the pregnancy syndrome preeclampsia is still unclear, while most hypotheses center on the placenta as the major contributor of the syndrome. Especially changes of the placental metabolism, including the use of glucose to produce energy, are important features. As an example, inositol phosphoglycan P-type molecules, second messengers involved in the glucose metabolism of all cells, can be retrieved from maternal urine of preeclamptic women, even before the onset of clinical symptoms. Alterations in the placental metabolism may subsequently lead to negative effects on the plasma membrane of the placental syncytiotrophoblast. This in turn may have deleterious effects on the glycocalyx of this layer and a disruption of this layer in all types of preeclampsia. The interruption of the glycocalyx in preeclampsia may result in changes of inositol phosphoglycan P-type signaling pathways and the release of these molecules as well as the release of soluble receptors such as sFlt-1 and sEndoglin. The release of placental factors later affects the maternal endothelium and disrupts the endothelial glycocalyx as well. This in turn may pave the way for edema, endothelial dysfunction, coagulation, all typical symptoms of preeclampsia.

mRNA and Protein Expression in Human Fetal Membrane Cells: Potential Biomarkers for Preterm Prelabor Rupture of the Fetal Membranes?

Clinically, unique markers in fetal membrane cells may contribute to the search for biomarkers for preterm prelabor rupture of the fetal membranes (pPROM) in maternal blood. pPROM is associated with overwhelming inflammation and premature cellular senescence causing "biological microfractures" of the fetal membranes. We hypothesize that these pathological processes are associated with the shedding of fetal membrane cells into the maternal circulation. The aim of this study was to identify markers expressed exclusively in fetal membrane cells to facilitate their isolation, characterization, and determination of biomarker potential in maternal blood. We have (1), by their transcriptomic profile, identified markers that are upregulated in amnion and chorion tissue compared to maternal white blood cells, and (2), by immunohistochemistry, confirmed the localization of the differentially expressed proteins in fetal membranes, placenta, and the placental bed of the uterus. RNA sequencing revealed 31 transcripts in the amnion and 42 transcripts in the chorion that were upregulated. Among these, 22 proteins were evaluated by immunohistochemistry. All but two transcripts were expressed both on mRNA and protein level in at least one fetal membrane cell type. Among these remaining 20 proteins, 9 proteins were not significantly expressed in the villous and extravillous trophoblasts of the placenta.

Relapses in Illicit Drug Use Among Probationers: Results in a Risk Group of Public Health Services in Bavaria

Objective: We aimed to identify in this study time trends of relapses in the illicit consumption of narcotics in a special at-risk population of former drug users under a public health perspective. Methods: In a pooled dataset of 14 consecutive calendar years (2006-2019), the use of seven different narcotic substances was studied in 380 persons with a total of 2,928 urine samples which were analyzed using a valid marker system for narcotic residues. Results: During the entire observation period, the relapse rate for cannabinoids and opiates was the highest despite abstinence requirements. It was noticeable that the relapses across all narcotics groups occurred primarily during the first 3 years of the probation period (90%) with a decrease in illegal consumption during the following years of the observation period. Conclusion: Special attention should be paid to probationers at the beginning of the probation period to develop more effective prevention strategies for substance abstinence by all involved actors in public health services.

Automated stereological image analysis approach of the human placenta: Surface areas and vascularization

Detecting and quantifying surface densities of placental villi and their vasculature adds important information on the development of the placenta under different exposures and pathological conditions. Today, a larger number of samples and tissue areas can be examined using automated Artificial Intelligence-based approaches. Although each image series calls for a particular approach, sharing the methods will help in facilitating reproducibility and comparability. Here we show the protocol of a software-based quantification of vessels (number and area) in villous tissues of human placentas, based on scanned images of full-size placental sections.

Maternal COVID-19 causing intrauterine foetal demise with microthrombotic placental insufficiency: a case report

BACKGROUND

Pregnant women have an increased risk of getting infected with SARS-CoV-2 and are more prone to severe illness. Data on foetal demise in affected pregnancies and its underlying aetiology is scarce and pathomechanisms remain largely unclear.

CASE

Herein we present the case of a pregnant woman with COVID-19 and intrauterine foetal demise. She had no previous obstetric or gynaecological history, and presented with mild symptoms at 34 + 3 weeks and no signs of foetal distress. At 35 + 6 weeks intrauterine foetal death was diagnosed. In the placental histopathology evaluation, we found inter- and perivillous fibrin depositions including viral particles in areas of degraded placental anatomy without presence of viral entry receptors and SARS-CoV-2 infection of the placenta.

CONCLUSION

This case demonstrates that maternal SARS-CoV-2 infection in the third trimester may lead to an unfavourable outcome for the foetus due to placental fibrin deposition in maternal COVID-19 disease possibly via a thrombogenic microenvironment, even when the foetus itself is not infected.

Ex Vivo Placental Explant Flow Culture - Mimicking the Dynamic Conditions In Utero

The existing ex vivo placental explant culture models are primarily grounded in static culture systems using well plates. However, these models inadequately reflect the dynamic in utero setting, where the placenta encounters constant slight shear stress due to plasma or blood flow. To address this limitation, a flow culture system has been devised to bring ex vivo placental explant cultivation closer to the in utero flow conditions experienced within the maternal body. Within this approach, placental explants are cultivated in a sequence of five interconnected flow chambers. This setting maintains physiological oxygen concentrations and a consistent flow rate. The collected data reveals that under flow conditions, the preservation of tissue morphology exhibits notable enhancement compared to conventional static methods. This innovative technique introduces a straightforward means of ex vivo placental explant culture, offering a more faithful representation of the dynamic in vivo environment. Moreover, this study introduces new possibilities for investigating the functional dynamics of the feto-maternal interface. By embracing feasible dynamic methodologies, a deeper comprehension of placental biology is facilitated, underscoring its relevance for maternal-fetal health.

Placental physioxia is based on spatial and temporal variations of placental oxygenation throughout pregnancy

For obvious reasons, in vivo measurements of placental oxygenation are extremely rare and hence, scientists need to focus on the few studies that revealed at least some data on the topic. The scarcity of real in vivo data resulted in the development of hypotheses on placental oxygenation that blocked an objective view on the topic for decades. Only now, new hypotheses are emerging adding new views and ideas on the topic. Especially in the field of preeclampsia, hypotheses on placental oxygenation have mislead a whole generation of scientists. This review article displays the available in vivo placental oxygen data from 8 to 40 weeks of gestation. It also compares these physiological oxygen concentrations, called physioxia, with the situation in pre-placental hypoxia, i.e. pregnancies at high altitude. Finally, it summarizes what we know today about oxygen measurements in cases with preeclampsia. In early-onset preeclampsia cases, all in vivo data available today point to increased oxygen values in the intervillous space of the placenta. This is due to a reduced oxygen transfer of the placental barrier from maternal to fetal blood, resulting in hypoxia of fetal blood and the fetus.

CD39 abrogates platelet-derived factors induced IL-1β expression in the human placenta

Tissue insults in response to inflammation, hypoxia and ischemia are accompanied by the release of ATP into the extracellular space. There, ATP modulates several pathological processes, including chemotaxis, inflammasome induction and platelet activation. ATP hydrolysis is significantly enhanced in human pregnancy, suggesting that increased conversion of extracellular ATP is an important anti-inflammatory process in preventing exaggerated inflammation, platelet activation and hemostasis in gestation. Extracellular ATP is converted into AMP, and subsequently into adenosine by the two major nucleotide-metabolizing enzymes CD39 and CD73. Here, we aimed to elucidate developmental changes of placental CD39 and CD73 over gestation, compared their expression in placental tissue from patients with preeclampsia and healthy controls, and analyzed their regulation in response to platelet-derived factors and different oxygen conditions in placental explants as well as the trophoblast cell line BeWo. Linear regression analysis showed a significant increase in placental CD39 expression, while at the same time CD73 levels declined at term of pregnancy. Neither maternal smoking during first trimester, fetal sex, maternal age, nor maternal BMI revealed any effects on placental CD39 and CD73 expression. Immunohistochemistry detected both, CD39 and CD73, predominantly in the syncytiotrophoblast layer. Placental CD39 and CD73 expression were significantly increased in pregnancies complicated with preeclampsia, when compared to controls. Cultivation of placental explants under different oxygen conditions had no effect on the ectonucleotidases, whereas presence of platelet releasate from pregnant women led to deregulated CD39 expression. Overexpression of recombinant human CD39 in BeWo cells decreased extracellular ATP levels after culture in presence of platelet-derived factors. Moreover, platelet-derived factors-induced upregulation of the pro-inflammatory cytokine, interleukin-1β, was abolished by CD39 overexpression. Our study shows that placental CD39 is upregulated in preeclampsia, suggesting an increasing demand for extracellular ATP hydrolysis at the utero-placental interface. Increased placental CD39 in response to platelet-derived factors may lead to enhanced conversion of extracellular ATP levels, which in turn could represent an important anti-coagulant defense mechanism of the placenta.

The challenges of histology education

Generations of students have struggled to learn histology. They have found the subject extremely dry and the nomenclature very challenging. Insidiously, histology is fading from the minds of stakeholders. Unless this is rectified, it is not inconceivable that the subject will be further diluted in the medical curriculum. What contributing factors could there be? Via a survey and focus group discussions, international faculty (n = 111) were asked what the challenges in teaching histology were. Both qualitative and quantitative data were collected and stratified by the number of teaching years. A collaborative teaching session with a pathologist was also delivered to the YLLSoMM1 students (n = 280), who gave opinions about it. Of the international faculty, 85 (±1)% responded. Among those, 60 (±1)% felt that the pedagogy should be reformed (e.g., by gamification). Interestingly, 30 (±1)% opined that organ system histology should be moved into the clinical years. Notably, 70 (±1)% of teachers preferred to teach face to face (FTF) using either microscopes or virtual microscopy. Among the students, 71 (±1)% reported self-teaching from online resources. Significantly, 88 (±1)% of M1 students agreed that having the pathologist co-teach histology was beneficial. Some teachers, and most students, struggle with histology. There is a generational divide in opinions concerning how histology should be taught. The traditionalists wish to maintain the status quo while the reformists want changes. Learners want to be engaged with hybrid approaches aided by the pathologist. They also welcome more clinical context during histology lessons.

Early human trophoblast development: from morphology to function

Human pregnancy depends on the proper development of the embryo prior to implantation and the implantation of the embryo into the uterine wall. During the pre-implantation phase, formation of the morula is followed by internalization of blastomeres that differentiate into the pluripotent inner cell mass lineage, while the cells on the surface undergo polarization and differentiate into the trophectoderm of the blastocyst. The trophectoderm mediates apposition and adhesion of the blastocyst to the uterine epithelium. These processes lead to a stable contact between embryonic and maternal tissues, resulting in the formation of a new organ, the placenta. During implantation, the trophectoderm cells start to differentiate and form the basis for multiple specialized trophoblast subpopulations, all of which fulfilling specific key functions in placentation. They either differentiate into polar cells serving typical epithelial functions, or into apolar invasive cells that adapt the uterine wall to progressing pregnancy. The composition of these trophoblast subpopulations is crucial for human placenta development and alterations are suggested to result in placenta-associated pregnancy pathologies. This review article focuses on what is known about very early processes in human reproduction and emphasizes on morphological and functional aspects of early trophoblast differentiation and subpopulations.

Physical Activity and Sedentary Time in Pregnancy: An Exploratory Study on Oxidative Stress Markers in the Placenta of Women with Obesity

Regular moderate-to-vigorous physical activity (MVPA) and reduced sedentary time (ST) improve maternal glucose metabolism in pregnancy. More MVPA and less ST outside pregnancy increase antioxidant capacity, hence, are beneficial in preventing oxidative stress. The placenta is the first line of defense for the fetus from an adverse maternal environment, including oxidative stress. However, effects of MVPA and ST on oxidative stress markers in the placenta are unknown. The purpose of this study was to assess the association of MVPA and ST in pregnancy with oxidative stress markers in placentas of overweight/obese women (BMI ≥ 29 kg/m2). MVPA and ST were objectively measured with accelerometers at <20 weeks, 24−27 and 35−37 weeks of gestation. Using linear Bayesian multilevel models, the associations of MVPA and ST (mean and changes) with mRNA expression of a panel of 11 oxidative stress related markers were assessed in 96 women. MVPA was negatively correlated with HSP70 mRNA expression in a sex-independent manner and with GCLM expression only in placentas of female fetuses. ST was positively associated with HO-1 mRNA expression in placentas of male neonates. None of the other markers were associated with MVPA or ST. We speculate that increasing MVPA and reducing ST attenuates the oxidative stress state in placentas of obese pregnant women.

(Dis)similarities between the Decidual and Tumor Microenvironment

Placenta-specific trophoblast and tumor cells exhibit many common characteristics. Trophoblast cells invade maternal tissues while being tolerated by the maternal immune system. Similarly, tumor cells can invade surrounding tissues and escape the immune system. Importantly, both trophoblast and tumor cells are supported by an abetting microenvironment, which influences invasion, angiogenesis, and immune tolerance/evasion, among others. However, in contrast to tumor cells, the metabolic, proliferative, migrative, and invasive states of trophoblast cells are under tight regulatory control. In this review, we provide an overview of similarities and dissimilarities in regulatory processes that drive trophoblast and tumor cell fate, particularly focusing on the role of the abetting microenvironments.

Reduced Placental CD24 in Preterm Preeclampsia Is an Indicator for a Failure of Immune Tolerance

INTRODUCTION

CD24 is a mucin-like glycoprotein expressed at the surface of hematopoietic and tumor cells and was recently shown to be expressed in the first trimester placenta. As it was postulated as an immune suppressor, CD24 may contribute to maternal immune tolerance to the growing fetus. Preeclampsia (PE), a major pregnancy complication, is linked to reduced immune tolerance. Here, we explored the expression of CD24 in PE placenta in preterm and term cases.

METHODS

Placentas were derived from first and early second trimester social terminations (N = 43), and third trimester normal term delivery (N = 67), preterm PE (N = 18), and preterm delivery (PTD) (N = 6). CD24 expression was determined by quantitative polymerase chain reaction (qPCR) and Western blotting. A smaller cohort included 3-5 subjects each of term and early PE, and term and preterm delivery controls analyzed by immunohistochemistry.

RESULTS

A higher expression (2.27-fold) of CD24 mRNA was determined in the normal term delivery compared to first and early second trimester cases. The mRNA of preterm PE cases was only higher by 1.31-fold compared to first and early second trimester, while in the age-matched PTD group had a fold increase of 5.72, four times higher compared to preterm PE. The delta cycle threshold (ΔCt) of CD24 mRNA expression in the preterm PE group was inversely correlated with gestational age (r = 0.737) and fetal size (r = 0.623), while correlation of any other group with these parameters was negligible. Western blot analysis revealed that the presence of CD24 protein in placental lysate of preterm PE was significantly reduced compared to term delivery controls (p = 0.026). In immunohistochemistry, there was a reduction of CD24 staining in villous trophoblast in preterm PE cases compared to gestational age-matched PTD cases (p = 0.042). Staining of PE cases at term was approximately twice higher compared to preterm PE cases (p = 0.025) but not different from normal term delivery controls.

CONCLUSION

While higher CD24 mRNA expression levels were determined for normal term delivery compared to earlier pregnancy stages, this expression level was found to be lower in preterm PE cases, and could be said to be linked to reduced immune tolerance in preeclampsia.

Placental Villous Explant Culture 2.0: Flow Culture Allows Studies Closer to the In Vivo Situation

During pregnancy, freely floating placental villi are adapted to fluid shear stress due to placental perfusion with maternal plasma and blood. In vitro culture of placental villous explants is widely performed under static conditions, hoping the conditions may represent the in utero environment. However, static placental villous explant culture dramatically differs from the in vivo situation. Thus, we established a flow culture system for placental villous explants and compared commonly used static cultured tissue to flow cultured tissue using transmission and scanning electron microscopy, immunohistochemistry, and lactate dehydrogenase (LDH) and human chorionic gonadotropin (hCG) measurements. The data revealed a better structural and biochemical integrity of flow cultured tissue compared to static cultured tissue. Thus, this new flow system can be used to simulate the blood flow from the mother to the placenta and back in the most native-like in vitro system so far and thus can enable novel study designs.

Maternal Angiotensin Increases Placental Leptin in Early Gestation via an Alternative Renin-Angiotensin System Pathway: Suggesting a Link to Preeclampsia

[Figure: see text].

The endogenous exposome of the pregnant mother: Placental extracellular vesicles and their effect on the maternal system

During pregnancy, there is an intense crosstalk between mother and placenta. During the entire time of pregnancy, the maternal system deals with a huge amount of foreign (fetal) material released from the placenta, which can be referred to as placental exposome. Besides the release of hormones and growth factors, the placenta releases a variety of extracellular vesicles into maternal blood. These vesicles contain specific molecules including proteins, lipids, DNA as well as miRNA, all of which may have specific sites and modes of action on maternal cells. During normal pregnancy, the fine-tuning of factors and vesicles helps maintaining a viable and healthy pregnancy. However, in pregnancy pathologies such as preeclampsia, quantity and quality of the placenta-derived vesicles are altered leading to a deleterious effect on the maternal vascular system. This review focuses on the different types of placenta-derived extracellular vesicles in pregnancy with special emphasis on the interplay between these placental vesicles and the maternal system. Additionally, it displays new techniques and ideas for the analysis of the placental exposome with placental extracellular vesicles as a key aspect.

Perinatal Derivatives: Where Do We Stand? A Roadmap of the Human Placenta and Consensus for Tissue and Cell Nomenclature

Progress in the understanding of the biology of perinatal tissues has contributed to the breakthrough revelation of the therapeutic effects of perinatal derivatives (PnD), namely birth-associated tissues, cells, and secreted factors. The significant knowledge acquired in the past two decades, along with the increasing interest in perinatal derivatives, fuels an urgent need for the precise identification of PnD and the establishment of updated consensus criteria policies for their characterization. The aim of this review is not to go into detail on preclinical or clinical trials, but rather we address specific issues that are relevant for the definition/characterization of perinatal cells, starting from an understanding of the development of the human placenta, its structure, and the different cell populations that can be isolated from the different perinatal tissues. We describe where the cells are located within the placenta and their cell morphology and phenotype. We also propose nomenclature for the cell populations and derivatives discussed herein. This review is a joint effort from the COST SPRINT Action (CA17116), which broadly aims at approaching consensus for different aspects of PnD research, such as providing inputs for future standards for the processing and in vitro characterization and clinical application of PnD.

Platelet-derived factors impair placental chorionic gonadotropin beta-subunit synthesis

Abstract

During histiotrophic nutrition of the embryo, maternal platelets may be the first circulating maternal cells that find their way into the placental intervillous space through narrow intertrophoblastic gaps within the plugs of spiral arteries. Activation of platelets at the maternal-fetal interface can influence trophoblast behavior and has been implicated in serious pregnancy pathologies. Here, we show that platelet-derived factors impaired expression and secretion of the human chorionic gonadotropin beta-subunit (βhCG) in human first trimester placental explants and the trophoblast cell line BeWo. Impaired βhCG synthesis was not the consequence of hampered morphological differentiation, as assessed by analysis of differentiation-associated genes and electron microscopy. Platelet-derived factors did not affect intracellular cAMP levels and phosphorylation of CREB, but activated Smad3 and its downstream-target plasminogen activator inhibitor (PAI)-1 in forskolin-induced BeWo cell differentiation. While TGF-β type I receptor inhibitor SB431542 did not restore impaired βhCG production in response to platelet-derived factors, Smad3 inhibitor SIS3 interfered with CREB activation, suggesting an interaction of cAMP/CREB and Smad3 signaling. Sequestration of transcription co-activators CBP/p300, known to bind both CREB and Smad3, may limit βhCG production, since CBP/p300 inhibitor C646 significantly restricted its forskolin-induced upregulation. In conclusion, our study suggests that degranulation of maternal platelets at the early maternal-fetal interface can impair placental βhCG production, without substantially affecting morphological and biochemical differentiation of villous trophoblasts.

Key messages

Maternal platelets can be detected on the surface of the placental villi and in intercellular gaps of trophoblast cell columns from gestational week 5 onwards.

Platelet-derived factors impair hCG synthesis in human first trimester placenta.

Platelet-derived factors activate Smad3 in trophoblasts.

Smad3 inhibitor SIS3 interferes with forskolin-induced CREB signaling.

Sequestration of CBP/p300 by activated Smad3 may limit placental hCG production.

Electronic supplementary material

The online version of this article (10.1007/s00109-019-01866-x) contains supplementary material, which is available to authorized users.

Galectin 13 (PP13) Facilitates Remodeling and Structural Stabilization of Maternal Vessels during Pregnancy

Galectins regulate cell growth, proliferation, differentiation, apoptosis, signal transduction, mRNA splicing, and interactions with the extracellular matrix. Here we focus on the galectins in the reproductive system, particularly on a group of six galectins that first appears in anthropoid primates in conjunction with the evolution of highly invasive placentation and long gestation. Of these six, placental protein 13 (PP13, galectin 13) interacts with glycoproteins and glycolipids to enable successful pregnancy. PP13 is related to the development of a major obstetric syndrome, preeclampsia, a life-threatening complication of pregnancy which affects ten million pregnant women globally. Preeclampsia is characterized by hypertension, proteinuria, and organ failure, and is often accompanied by fetal loss and major newborn disabilities. PP13 facilitates the expansion of uterine arteries and veins during pregnancy in an endothelial cell-dependent manner, via the eNOS and prostaglandin signaling pathways. PP13 acts through its carbohydrate recognition domain that binds to sugar residues of extracellular and connective tissue molecules, thus inducing structural stabilization of vessel expansion. Further, decidual PP13 aggregates may serve as a decoy that induces white blood cell apoptosis, contributing to the mother's immune tolerance to pregnancy. Lower first trimester PP13 level is one of the biomarkers to predict the subsequent risk to develop preeclampsia, while its molecular mutations/polymorphisms that are associated with reduced PP13 expression are accompanied by higher rates of preeclampsia We propose a targeted PP13 replenishing therapy to fight preeclampsia in carriers of these mutations.

Placental protein 13 (PP13) stimulates rat uterine vessels after slow subcutaneous administration

Introduction

Reduced concentrations of placental protein 13 (PP13) during the first trimester of human pregnancy are associated with elevated risk for the subsequent development of preeclampsia, which is one of the deadliest obstetrical complications of pregnancy. Previous studies by our group have shown that PP13 lowers blood pressure in pregnant rats, increases the size and weight of pups and placentas, and induces vasodilation of resistance arteries through endothelial signaling pathways involving endothelial nitric oxid synthase and prostaglandin.

Methods

In the present study, the effect of PP13 was investigated in nonpregnant female Sprague Dawley rats (n=27). Osmotic pumps were surgically implanted subcutaneously that released a constant dose of PP13 or saline over 7 days. Most animals were sacrificed 6 days after the end of PP13 release (on day 13), while some were sacrificed immediately at the end of day 7 (the last PP13 release day), to compare the short- and long-term impact of PP13 on vessels’ growth and size.

Results

The uterine vessels were significantly expanded in the group exposed to recombinant PP13 (rPP13) compared to the control (saline) group. Both veins and arteries were significantly expanded by rPP13 with a more pronounced effect after 13 days compared to the corresponding vessels after 7 days. Furthermore, the long-term effect of treatment by rPP13 was more pronounced in the veins compared to the corresponding arteries. The effect of a PP13 variant with a histidine-tag (His-PP13) remained the same between 7 and 13 days.

Conclusion

In conclusion, PP13 might play a key role in the expansive remodeling of the uterine vessels, reflecting what would happen if the rat was pregnant, preparing the uterine vascu-lature for the increase in uteroplacental blood flow, which is necessary for normal pregnancy. We suggest that PP13 could act by NO signaling pathways, a hypothesis that requires future study.

The Critical Role of Abnormal Trophoblast Development in the Etiology of Preeclampsia

Background:

The pregnancy pathology preeclampsia is still among the leading causes of ma-ternal and perinatal morbidity and mortality. At the same time, its etiology is far from being identified and remains obscure in a number of facets.

A number of hypotheses have been developed to explain the altered interplay between placenta and mother leading to the clinical symptoms of preeclampsia. However, none of them offers the opportunity to explain the variability of cases with late-onset versus early-onset, mild versus severe and with or with-out additional fetal growth restriction.

Conclusion:

This paper identifies the weaknesses of the most important current hypothesis and at the same time offers a set of new elucidations including maternal susceptibility, and villous/extravillous trophoblast differentiation to explain the development of preeclampsia. Such elucidations allow following new scientific routes and pathways to untangle the etiology of preeclampsia.

Amnion-derived mesenchymal stem cells improve viability of endothelial cells exposed to shear stress in ePTFE grafts

PURPOSE:

Blood vessel reconstruction is an increasing need of patients suffering from cardiovascular diseases. For the development of microvascular prostheses, efficient endothelialization is mandatory to prevent graft occlusion. Here, we assessed the impact of amnion-derived mesenchymal stem/stromal cells (hAMSC), known for their important angiogenic potential, on the integrity and stability of endothelial cells exposed to shear stress in vascular grafts.

METHODS:

Human placental endothelial cells (hPEC) were cultured at the inner surface of an expanded polytetrafluoroethylene (ePTFE) graft positioned within a bioreactor and exposed to a minimal shear stress of 0.015 dyne/cm² or a physiological shear stress of 0.92 dyne/cm². hAMSC attached to the outer graft surface were able to interact with human placental endothelial cells by paracrine factors.

RESULTS:

Microscopical analysis and evaluation of glucose/lactate metabolism evidenced successful cell seeding of the graft: hPEC formed a stable monolayer, hAMSC showed a continuous growth during 72 h incubation. hAMSC improved the viability of hPEC exposed to 0.015 dyne/cm² as shown by a decreased lactate dehydrogenase release of 13% after 72 h compared to hPEC single culture. The viability-enhancing effect of hAMSC on hPEC was further improved by 13% under physiological shear stress. Angiogenesis array analysis revealed that hPEC exposed to physiological shear stress and hAMSC co-culture reduced the secretion of angiogenin, GRO, MCP-1, and TIMP-2.

CONCLUSION:

hAMSC exerted best survival-enhancing effects on hPEC under exposure to physiological shear stress and modulated endothelial function by paracrine factors. Our data support further studies on the development of grafts functionalized with hAMSC-derived secretomes to enable fast clinical application.

Biology of preeclampsia: Combined actions of angiogenic factors, their receptors and placental proteins

Although massive efforts have been undertaken to elucidate the etiology of the pregnancy syndrome preeclampsia, its developmental origin remains a mystery. Most efforts of the last decade have focused on biomarkers to predict and/or diagnose preeclampsia, including the anti-angiogenic factor sFlt-1 (soluble fms-like tyrosin kinase-1), the angiogenic factor PGF (placental growth factor) and PP13 (placental protein 13). The origins of these marker proteins are still under debate, and so far their actions have only been describe separate from each other. This study will focus on the origins and actions of all three markers during pregnancy and outside pregnancy and will describe a scenario where all three markers act synergistically to rescue the mother from the deleterious effects of the debris that is released from the placenta during preeclampsia. This more holistic approach may open new avenues to think about maternal-fetal interactions and putative therapies.

An updated view on the origin and use of angiogenic biomarkers for preeclampsia

Introduction: The last decade has seen massive efforts towards the identification and the potential use of predictive biomarkers for the pregnancy pathology preeclampsia. The angiogenic factors sFlt-1 and placental growth factor (PGF) have been in focus and have been massively supported. Areas covered: This review describes preeclampsia and intra-uterine growth restriction (IUGR), focusing on sFlt-1 and PGF, their sources during and outside pregnancy and the application of these markers in diseases outside pregnancy. Finally, the specificity of the angiogenic markers for preeclampsia is discussed. Expert commentary: The admixture of the two independent syndromes preeclampsia and IUGR has not helped in identifying the etiologies of either. Rather, it has made the search for new markers and pathways much more complicated as has the constriction on the angiogenic markers. The current markers sFlt-1 and PGF have a clear value once an adverse outcome is diagnosed but are not specific for preeclampsia. Also, they are mostly derived from the maternal vascular system rather than the placenta and are already in use as markers outside pregnancy. A new holistic approach using disease maps and interoperable workflows based on topic-related big data will help in broadening our understanding of the etiology of preeclampsia and hence, develop new markers and therapies.

Impact of vitamin D and vitamin D receptor on the trophoblast survival capacity in preeclampsia

BACKGROUND

Preeclampsia and intra-uterine growth restriction (IUGR) are major health problems during pregnancy affecting both mother and child. Defective placental development and failure of trophoblast differentiation during pregnancy are important aspects in the pathogenesis of both syndromes. Recent studies have shown that autophagy is involved in the trophoblast survival capacity. As vitamin D has a central role in many cellular processes, we studied the relation of vitamin D and autophagy in those processes of preeclampsia and IUGR.

METHODS

Serum and placental samples from four groups of cases; normal term, IUGR, early-onset and late-onset preeclampsia, were analyzed for 25(OH)D vitamin D, sFLT1, PGF, LGALS13 in serum and vitamin D receptor (VDR), MAP1LC3B and BECN1 in placental tissues.

RESULTS

There was a significant difference in the sFLT1/PGF ratio in preeclamptic cases compared to controls and IUGR. There was a significant difference between these groups in the MAP1LC3B/BECN1 ratio as marker of the trophoblast survival capacity with a significantly reduced ratio in villous trophoblast of early-onset preeclampsia. Maternal vitamin D deficiency was found in all pathological pregnancies combined with significantly reduced staining levels of placental VDR in IUGR. Finally, there was a strong and significant negative correlation between the survival capacity (MAP1LC3B/BECN1) and both maternal vitamin D and placental VDR in the preeclampsia groups.

CONCLUSION

Vitamin D and intracellular VDR are strongly related to the trophoblast survival capacity in preeclampsia.

Human trophoblast invasion: new and unexpected routes and functions

Until recently, trophoblast invasion during human placentation was characterized by and restricted to invasion into uterine connective tissues and the uterine spiral arteries. The latter was explained to connect the arteries to the intervillous space of the placenta and to guarantee the blood supply of the mother to the placenta. Today, this picture has dramatically changed. Invasion of endoglandular trophoblast into uterine glands, already starting at the time of implantation, enables histiotrophic nutrition of the embryo prior to perfusion of the placenta with maternal blood. This is followed by invasion of endovenous trophoblasts into uterine veins to guarantee the drainage of fluids from the placenta back into the maternal circulation throughout pregnancy. In addition, invasion of endolymphatic trophoblasts into the lymph vessels of the uterus has been described. Only then, invasion of endoarterial trophoblasts into spiral arteries takes place, enabling hemotrophic nutrition of the fetus starting with the second trimester of pregnancy. This new knowledge paves the way to identify changes that may occur in pathological pregnancies, from tubal pregnancies to recurrent spontaneous abortions.

Pharmacokinetics of placental protein 13 after intravenous and subcutaneous administration in rabbits

Introduction

Human placental protein 13 (PP13) is a galectin predominantly expressed by the placenta. Low serum concentrations of PP13 in early pregnancy indicate a higher risk of developing preeclampsia.

Methods

The pharmacokinetic disposition and bioavailability of PP13 were determined by single intravenous and subcutaneous administration to 12 healthy New Zealand White rabbits. The serum pharmacokinetic values were determined by enzyme-linked immunosorbent assay, and are best described by a two-compartment model.

Results

Both volume of distribution and the area under the curve were dose dependent for the intravenous group (p<0.01). PP13 elimination half-life was also found to be different between the groups (p<0.01). The bioavailability of PP13 following subcutaneous administration was found to be 57%.

Conclusion

This study shows that the concentration of total PP13 released into the maternal circulation during pregnancy might be much higher than previously estimated.

Trophoblast retrieval and isolation from the cervix: origins of cervical trophoblasts and their potential value for risk assessment of ongoing pregnancies

BACKGROUND

Early during human development, the trophoblast lineage differentiates to commence placentation. Where the placenta contacts the uterine decidua, extravillous trophoblast (EVT) cells differentiate and invade maternal tissues. EVT cells, identified by expression of HLA-G, invade into uterine blood vessels (endovascular EVT), as well as glands (endoglandular EVT), and open such luminal structures towards the intervillous space of the placenta. Endoglandular invasion diverts the contents of uterine glands to the intervillous space, while glands near the margin of the placenta that also contain endoglandular EVT cells open into the reproductive tract. Cells of the trophoblast lineage have thus been recovered from the uterine cavity and endocervical canal. An emerging non-invasive technology [trophoblast retrieval and isolation from the cervix (TRIC)] isolates and examines EVT cells residing in the cervix to explore their origin, biology and relationship to pregnancy and fetal status.

OBJECTIVE AND RATIONALE

This review explores the origins and possible uses of trophoblast cells obtained during ongoing pregnancies (weeks 5-20) by TRIC. We hypothesize that endoglandular EVT cells at the margins of the expanding placenta enter the uterine cavity and are carried together with uterine secretion products to the cervix where they can be retrieved from a Papanicolaou (Pap) smear. The advantages of TRIC for investigation of human placentation and prenatal testing will be considered. Evidence from the literature, and from archived in utero placental histological sections, is presented to support these hypotheses.

SEARCH METHODS

We used 52 out of 80 publications that appeared between 1966 and 2017 and were found by searching the PubMed and Google Scholar databases. The studies described trophoblast invasion of uterine vessels and glands, as well as trophoblast cells residing in the reproductive tract. This was supplemented with literature on human placental health and disease.

OUTCOMES

The literature describes a variety of invasive routes taken by EVT cells at the fetal-maternal interface that could displace them into the reproductive tract. Since the 1970s, investigators have attempted to recover trophoblast cells from the uterus or cervix for prenatal diagnostics. Trophoblast cells from Pap smears obtained at 5-20 weeks of gestation have been purified (>95% β-hCG positive) by immunomagnetic isolation with nanoparticles linked to anti-HLA-G (TRIC). The isolated cells contain the fetal genome, and have an EVT-like expression profile. Similar EVT-like cells appear in the lumen of uterine glands and can be observed entering the uterine cavity along the margins of the placenta, suggesting that they are the primary source of cervical trophoblast cells. Cells isolated by TRIC can be used to accurately genotype the embryo/fetus by targeted next-generation sequencing. Biomarker protein expression quantified in cervical trophoblast cells after TRIC correlates with subsequent pregnancy loss, pre-eclampsia and fetal growth restriction. A key remaining question is the degree to which EVT cells in the cervix might differ from those in the basal plate and placental bed.

WIDER IMPLICATIONS

TRIC could one day provide a method of risk assessment for maternal and fetal disease, and reveal molecular pathways disrupted during the first trimester in EVT cells associated with placental maldevelopment. As perinatal interventions emerge for pregnancy disorders and inherited congenital disorders, TRIC could provide a key diagnostic tool for personalized precision medicine in obstetrics.

Correction to: Expression of matrix metalloproteinase 12 is highly specific for non-proliferating invasive trophoblasts in the first trimester and temporally regulated by oxygen-dependent mechanisms including HIF-1A

In the original publication, the contribution of Dr. Christian Eyth as equal first author was not indicated. This has been corrected confirming that U. Hidden and C. Eyth contributed equally to this work.

N-cadherin knockdown leads to disruption of trophoblastic and endothelial cell interaction in a 3D cell culture model - New insights in trophoblast invasion failure

INTRODUCTION

Trophoblast homing to maternal spiral arteries is mandatory for successful placentation. Cell-cell adhesion molecules regulate this process and adhesion molecule expression is altered in impaired placentation. We hypothesize that, similar to immune cell recruitment, trophoblast cell adherence and rolling are primarily mediated by adhesion molecules like, cadherins, immunoglobulins, selectins and their partnering ligands. Here, the interdependence of adhesion molecule expression in trophoblastic cell lines of diverse origin was investigated in relation to their interaction with endothelial cell networks on Matrigel® co-cultures and the effect of specific adhesion molecule knockdown analyzed.

METHODS

Trophoblastic cells were labeled in red and co-cultured with green HUVEC networks on Matrigel®. Association was quantified after collection of fluorescence microscopy pictures using Wimasis® internet platform and software. Expression of adhesion molecules was analyzed by PCR and Western blot, immuno-fluorescence and flow cytometry. The impact of adhesion molecules on trophoblast-endothelial-cell interaction was investigated using siRNA technique.

RESULTS

N-cadherin and CD162 were specifically expressed in the trophoblast cell line HTR-8/SVneo, which closely adhere to and actively migrate toward HUVEC networks on Matrigel®. Suppression of N-cadherin led to a significant alteration in trophoblast-endothelial cell interaction. Expression of VE-cadherin in closely interacting trophoblast cells was not confirmed in vitro.

DISCUSSION

We identified N-cadherin to mediate specific interaction between HUVEC and the migrating trophoblast cells HTR-8/SVneo in a Matrigel® co-culture model. VE-cadherin contribution could not be confirmed in vitro. Our results support the hypothesis that impaired N-cadherin but not VE-cadherin expression is involved in trophoblast recruitment to the maternal endothelium.

Personalized Therapy Against Preeclampsia by Replenishing Placental Protein 13 (PP13) Targeted to Patients With Impaired PP13 Molecule or Function

Hypertensive disorders affect about one third of all people aged 20 and above, and are treated with anti-hypertensive drugs. Preeclampsia (PE) is one form of such disorders that only develops during pregnancy. It affects ten million pregnant women globally and additionally causes fetal loss and major newborn disabilities. The syndrome's origin is multifactorial, and anti-hypertensive drugs are ineffective in treating it. Biomarkers are helpful for predict its development. Generic drugs, such as low dose aspirin, were proven effective in preventing preterm PE. However, it does not cure the majority of cases and many studies are underway for fighting PE with extended use of additional generic drugs, or through new drug development programs. This review focuses on placental protein 13 (PP13). This protein is only expressed in the placenta. Impaired PP13 DNA structure and/or its reduced mRNA expression leads to lower blood PP13 level that predict a higher risk of developing PE. Two polymorphic PP13 variants have been identified: (1) The promoter PP13 variant with an "A/A" genotype in the -98 position (versus "A/C" or "C/C"). Having the "A/A" genotype is coupled to lower PP13 expression, mainly during placental syncytiotrophoblast differentiation and, if associated with obesity and history of previous preeclampsia, it accurately predicts higher risk for developing the disorder. (2) A thymidine deletion at position 221 causes a frame shift in the open reading frame, and the formation of an early stop codon resulting in the formation of DelT221, a truncated variant of PP13. In pregnant rodents, both short- and long- term replenishment of PP13 causes reversible hypotension and vasodilation of uterine vessels. Long-term exposure is also accompanied by the development of larger placentas and newborns. Also, only w/t PP13 is capable of inducing leukocyte apoptosis, providing maternal immune tolerance to pregnancy. Based on published data, we propose a targeted PP13 therapy to fight PE, and consider the design and conduct of animal studies to explore this hypothesis. Accordingly, a new targeted therapy can be implemented in humans combining prediction and prevention.

Disturbed Placental Imprinting in Preeclampsia Leads to Altered Expression of DLX5, a Human-Specific Early Trophoblast Marker

Supplemental Digital Content is available in the text.

Background:

Preeclampsia is a complex and common human-specific pregnancy syndrome associated with placental pathology. The human specificity provides both intellectual and methodological challenges, lacking a robust model system. Given the role of imprinted genes in human placentation and the vulnerability of imprinted genes to loss of imprinting changes, there has been extensive speculation, but no robust evidence, that imprinted genes are involved in preeclampsia. Our study aims to investigate whether disturbed imprinting contributes to preeclampsia.

Methods:

We first aimed to confirm that preeclampsia is a disease of the placenta by generating and analyzing genome-wide molecular data on well-characterized patient material. We performed high-throughput transcriptome analyses of multiple placenta samples from healthy controls and patients with preeclampsia. Next, we identified differentially expressed genes in preeclamptic placentas and intersected them with the list of human imprinted genes. We used bioinformatics/statistical analyses to confirm association between imprinting and preeclampsia and to predict biological processes affected in preeclampsia. Validation included epigenetic and cellular assays. In terms of human specificity, we established an in vitro invasion-differentiation trophoblast model. Our comparative phylogenetic analysis involved single-cell transcriptome data of human, macaque, and mouse preimplantation embryogenesis.

Results:

We found disturbed placental imprinting in preeclampsia and revealed potential candidates, including GATA3 and DLX5, with poorly explored imprinted status and no prior association with preeclampsia. As a result of loss of imprinting, DLX5 was upregulated in 69% of preeclamptic placentas. Levels of DLX5 correlated with classic preeclampsia markers. DLX5 is expressed in human but not in murine trophoblast. The DLX5^high phenotype resulted in reduced proliferation, increased metabolism, and endoplasmic reticulum stress-response activation in trophoblasts in vitro. The transcriptional profile of such cells mimics the transcriptome of preeclamptic placentas. Pan-mammalian comparative analysis identified DLX5 as part of the human-specific regulatory network of trophoblast differentiation.

Conclusions:

Our analysis provides evidence of a true association among disturbed imprinting, gene expression, and preeclampsia. As a result of disturbed imprinting, the upregulated DLX5 affects trophoblast proliferation. Our in vitro model might fill a vital niche in preeclampsia research. Human-specific regulatory circuitry of DLX5 might help explain certain aspects of preeclampsia.

Predicting the Risk to Develop Preeclampsia in the First Trimester Combining Promoter Variant -98A/C of LGALS13 (Placental Protein 13), Black Ethnicity, Previous Preeclampsia, Obesity, and Maternal Age

BACKGROUND

LGALS13 (placental protein 13 [PP13]) promoter DNA polymorphisms was evaluated in predicting preeclampsia (PE), given PP13's effects on hypotension, angiogenesis, and immune tolerance.

METHODS

First-trimester plasma samples (49 term and 18 intermediate) of PE cases matched with 196 controls were collected from King's College Hospital, London, repository. Cell-free DNA was extracted and the LGALS13 exons were sequenced after PCR amplification. Expression of LGALS13 promoter reporter constructs was determined in BeWo trophoblast-like cells with luciferase assays. Adjusted odds ratio (OR) was calculated for the A/A genotype combined with maternal risk factors.

RESULTS

The A/A, A/C, and C/C genotypes in the -98 promoter position were in Hardy-Weinberg equilibrium in the control but not in the PE group (p < 0.036). The dominant A/A genotype had higher frequency in the PE group (p < 0.001). The A/C and C/C genotypes protected from PE (p < 0.032). The ORs to develop term and all PE, calculated for the A/A genotype, previous PE, body mass index (BMI) >35, black ethnicity, and maternal age >40 were 15.6 and 11.0, respectively (p < 0.001). In luciferase assays, the "-98A" promoter variant had lower expression than the "-98C" variant in non-differentiated (-13%, p = 0.04) and differentiated (-26%, p < 0.001) BeWo cells. Forskolin-induced differentiation led to a larger expression increase in the "-98C" variant than in the "-98A" variant (4.55-fold vs. 3.85-fold, p < 0.001).

CONCLUSION

Lower LGALS13 (PP13) expression with the "A" nucleotide in the -98 promoter region position (compared to "C") and high OR calculated for the A/A genotype in the -98A/C promoter region position, history of previous PE, BMI >35, advanced maternal age >40, and black ethnicity could serve to aid in PE prediction in the first trimester.

A comparative study of five physiological key parameters between four different human trophoblast-derived cell lines

The human placenta plays a crucial role as the interface between mother and fetus. It represents a unique tissue that undergoes morphological as well as functional changes on the cellular and tissue level throughout pregnancy. To better understand how the placenta works, a variety of techniques has been developed to re-create this complex physiological barrier in vitro. However, due to the low availability of freshly isolated primary cells, choriocarcinoma cell lines remain the usual suspects as in vitro models for placental research. Here, we present a comparative study on the functional aspects of the choriocarcinoma cell lines BeWo, JAR and Jeg-3, as well as the first trimester trophoblast cell line ACH-3P as placental in vitro barrier models for endocrine and transport studies. Functional assays including tight junction immunostaining, sodium fluorescein retardation, trans epithelial resistance, glucose transport, hormone secretion as well as size-dependent polystyrene nanoparticle transport were performed using the four cell types to evaluate key functional parameters of each cell line to act a relevant in vitro placental barrier model.

Placental protein 13 (PP13)-induced vasodilation of resistance arteries from pregnant and nonpregnant rats occurs via endothelial-signaling pathways

Placental protein 13 (PP13) induces hypotension in rats. This study aims to evaluate PP13 effects on isolated uterine arteries from nonpregnant and mid-pregnant rats. Vessels were isolated, cannulated, and pressurized to 50 mmHg within an arteriograph, preconstricted and exposed to increasing PP13 concentrations (10^-13-10^-8 M). PP13 elicited 38-50% arterial vasodilation with half-maximum response (EC₅₀) = 1 pM. The relaxation was mediated by activating the endothelial-signaling pathways of prostaglandin and nitric oxide (NO). Accordingly, these results encourage evaluation of PP13 as a possible therapy for gestational diseases characterized by insufficient uteroplacental blood flow and/or maternal hypertension.

Increased placental sFlt-1 but unchanged PlGF expression in late-onset preeclampsia

OBJECTIVE

To investigate whether differences between late-onset preeclampsia (PE) and intrauterine growth restriction (IUGR) can be explained by differential placental expression patters of sFlt-1, Flt-1, and placental growth factor (PlGF).

METHODS

Placental tissues and maternal blood samples from seven patients with PE, five IUGR, and seven age-matched controls were studied for mRNA and protein levels as well as protein localization and expression intensity.

RESULTS

Placental PlGF mRNA and protein expression were not altered by placental dysfunction while placental villous trophoblast expression intensity of PlGF was increased.

CONCLUSION

High sFlt-1 concentrations may account for diminished maternal serum PlGF levels.

Challenges and Driving Forces for Business Plans in Biobanking

BACKGROUND

Due to increased utilization of biospecimens for research and emergence of new technologies, the availability and quality of biospecimens and their collection are coming more and more into focus. However, the long-term economic situation of biobanks is still mostly unclear. Also, the common sustainable utilization of various international biobanks is challenging due to local differences in sample processing, law and ethics.

AIM

This article discusses possible strategies to achieve a sustainable utilization of biospecimens as part of the business plan of biobanks.

METHODS

The following questions were addressed as part of a business plan: (1) How can a biobank build up and maintain an up-to-date infrastructure? (2) What kind of funding can support the sustainability of a biobank? (3) Is there an international solution for informed consents to enable sample and data sharing? (4) How can a biobank react during economically unstable periods? (5) Which kind of biobanking research is innovative? (6) What kind of education could be most needful for knowledge transfer in biobanking? (7) Does an expiration date for a biobank make sense according to the period of funding?

CONCLUSION

A strategy for optimal utilization begins with sharing of resources, infrastructure, and investments at the planning stage of a biobank, and continues to the transfer of knowledge and know-how by education. For clinical biobanks in particular, a long-term funding and cost recovery strategy is necessary for sustainable utilization.

Placental expression of sFlt-1 and PlGF in early preeclampsia vs. early IUGR vs. age-matched healthy pregnancies

OBJECTIVE

To investigate whether differences between early preeclampsia and early fetal growth restriction can be explained by differential placental expression patterns of sFlt-1, Flt-1, and PlGF.

METHODS

Placental tissues and maternal blood samples from six cases of preeclampsia, seven IUGR, and six age-matched controls were studied for mRNA and protein levels as well as protein localization and expression intensity.

RESULTS

Neither placental PlGF mRNA and protein expression nor placental villous trophoblast expression intensity of PlGF was altered by placental dysfunction.

CONCLUSION

High sFlt-1 concentrations may account for diminished maternal serum PlGF levels.

DNA methylation heterogeneity defines a disease spectrum in Ewing sarcoma

Developmental tumors in children and young adults carry few genetic alterations, yet they have diverse clinical presentation. Focusing on Ewing sarcoma, we sought to establish the prevalence and characteristics of epigenetic heterogeneity in genetically homogeneous cancers. We performed genome-scale DNA methylation sequencing for a large cohort of Ewing sarcoma tumors and analyzed epigenetic heterogeneity on three levels: between cancers, between tumors, and within tumors. We observed consistent DNA hypomethylation at enhancers regulated by the disease-defining EWS-FLI1 fusion protein, thus establishing epigenomic enhancer reprogramming as a ubiquitous and characteristic feature of Ewing sarcoma. DNA methylation differences between tumors identified a continuous disease spectrum underlying Ewing sarcoma, which reflected the strength of an EWS-FLI1 regulatory signature and a continuum between mesenchymal and stem cell signatures. There was substantial epigenetic heterogeneity within tumors, particularly in patients with metastatic disease. In summary, our study provides a comprehensive assessment of epigenetic heterogeneity in Ewing sarcoma and thereby highlights the importance of considering nongenetic aspects of tumor heterogeneity in the context of cancer biology and personalized medicine.

Expression of CD24 and Siglec-10 in first trimester placenta: implications for immune tolerance at the fetal-maternal interface

During pregnancy, the fetal-maternal interface establishes immune tolerance between the fetus and the mother. CD24, a mucin-like glycoprotein expressed at the surface of hematopoietic cells and diverse tumor cells, is known to interact with the sialic acid-binding immunoglobulin-type lectins (Siglecs). This interaction was assessed as a candidate complex for the immune suppression response in the placenta. CD24 was affinity purified from term placenta and characterized by SDS-PAGE, Western blot and ELISA. Binding of recombinant Siglecs to placental CD24 was evaluated by ELISA. The expression of CD24 and Siglec-10 in first trimester placental tissues was investigated by immunohistochemistry and immunofluorescence. Placental CD24 had an apparent molecular weight of 30-70 kDa consistent with its high degree of N- and O-linked glycosylation. EDTA-sensitive CD24-Siglec-10 interaction via the terminal sialic acid glycan residues of CD24 was observed. CD24 did not interact with Siglec-3 or Siglec-5. During the first trimester, and already in gestational week (GA) 8, CD24 showed high expression in villous and extravillous cytotrophoblasts. There was also a mild expression in stromal cells, while syncytiotrophoblasts were negative. Co-localization of CD24 with Siglec-10 was observed in endometrial glands and in first trimester decidual cells in close vicinity to extracellular trophoblasts. This study is the first to demonstrate the early presence of CD24 in the placenta cytotrophoblast layers, placental bed and maternal uterine glands. The presence of the CD24-Siglec-10 in these regions of fetal-maternal interactions suggests a possible role in mediating immune tolerance at the fetal-maternal interface.