Extravillous trophoblasts invade more than uterine arteries: evidence for the invasion of uterine veins

Dysregulated GLUT1 results in the pathogenesis of preeclampsia by impairing the function of trophoblast cells

Preeclampsia (PE) is a common placental-origin complication of pregnancy and a major cause of morbidity and mortality among pregnant women and fetuses. However, its pathogenesis has not been elucidated. Effective strategies for prevention, screening, and treatment are still lacking. Studies have indicated that dysfunction of placental trophoblast cells, such as impaired syncytialization, proliferation, and epithelial-mesenchymal transition processes, plays a crucial role in the development of PE. Glucose transporter 1 (GLUT1) is a key protein regulating glucose transport in placental tissues. However, the effect of GLUT1 on the function of trophoblast cells in PE is not well understood. In this study, we found that GLUT1 expression is reduced in PE placental tissues. GLUT1 promotes the syncytialization process by increasing the glucose uptake ability of BeWo cells. Additionally, GLUT1 promotes the proliferation, migration, and invasion capabilities of HTR-8/SVneo cells by regulating MAPK and PI3K/AKT signaling pathways. Overall, these findings provide a new insight into understanding the biological functions of GLUT1, clarifying the pathogenesis of PE, and identifying diagnostic and therapeutic targets for PE.

Cryptochrome 2 Suppresses Epithelial-Mesenchymal Transition by Promoting Trophoblastic Ferroptosis in Unexplained Recurrent Spontaneous Abortion

Unexplained recurrent spontaneous abortion (URSA) is a serious reproductive issue that affects women of childbearing age. Studies have shown a close association between disrupted circadian rhythm and impaired epithelial-mesenchymal transition (EMT) in trophoblasts during URSA, although the underlying mechanism is not known. The current study investigated the regulatory relationship between circadian rhythm gene cryptochrome 2 (CRY2) and ferroptosis on the migratory ability of trophoblast cells. Cell proliferation experiments, wound-healing assays, and expression of related markers were conducted to study EMT. Trophoblastic ferroptosis was confirmed by the expressions of malondialdehyde, glutathione, mitochondrial membrane potential, divalent iron ions, and related genes. The results showed significant increased expression of CRY2 and decreased expression of brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (BMAL1) in the URSA villous tissues, accompanied by iron-dependent oxidative changes and abnormal expression of ferroptosis-related proteins. CRY2 and BMAL1 were co-localized and functioned as a feedback loop, which regulated the dynamic changes of EMT-related markers in trophoblast cells. CRY2 promoted trophoblastic ferroptosis, whereas BMAL1 had the opposite effect. Particularly, the ferroptosis inhibitor (ferrostatin-1) effectively reversed the trophoblastic ferroptosis and EMT inhibition caused by CRY2 overexpression. Collectively, these results suggest that CRY2 regulates trophoblastic ferroptosis and hinders cellular EMT and migratory ability by suppressing BMAL1 expression.

EGR1 modulates EPHB4-induced trophoblast dysfunction in recurrent spontaneous abortion†

Recurrent spontaneous abortion, defined as at least three unexplained abortions occurring before the 20-24 week of pregnancy, has a great impact on women's quality of life. Ephrin receptor B4 has been associated with trophoblast function in preeclampsia. The present study aimed to verify the hypothesis that ephrin receptor B4 regulates the biological functions of trophoblasts in recurrent spontaneous abortion and to explore the upstream mechanism. Ephrin receptor B4 was overexpressed in mice with recurrent spontaneous abortion. Moreover, ephrin receptor B4 inhibited trophoblast proliferation, migration, and invasion while promoting apoptosis. Downregulation of early growth response protein 1 expression in mice with recurrent spontaneous abortion led to ephrin receptor B4 overexpression. Poor expression of WT1-associated protein in mice with recurrent spontaneous abortion reduced the modification of early growth response protein 1 mRNA methylation, resulting in decreased early growth response protein 1 mRNA stability and expression. Overexpression of WT1-associated protein reduced the incidence of recurrent spontaneous abortion in mice by controlling the phenotype of trophoblasts, which was reversed by early growth response protein 1 knockdown. All in all, our findings demonstrate that dysregulation of WT1-associated protein contributes to the instability of early growth response protein 1, thereby activating ephrin receptor B4-induced trophoblast dysfunction in recurrent spontaneous abortion. Our study provides novel insights into understanding the molecular pathogenesis of recurrent spontaneous abortion.

Oncostatin M and STAT3 Signaling Pathways Support Human Trophoblast Differentiation by Inhibiting Inflammatory Stress in Response to IFNγ and GM-CSF

Interleukin-6 (IL-6) superfamily cytokines play critical roles during human pregnancy by promoting trophoblast differentiation, invasion, and endocrine function, and maintaining embryo immunotolerance and protection. In contrast, the unbalanced activity of pro-inflammatory factors such as interferon gamma (IFNγ) and granulocyte-macrophage colony-stimulating factor (GM-CSF) at the maternal-fetal interface have detrimental effects on trophoblast function and differentiation. This study demonstrates how the IL-6 cytokine family member oncostatin M (OSM) and STAT3 activation regulate trophoblast fusion and endocrine function in response to pro-inflammatory stress induced by IFNγ and GM-CSF. Using human cytotrophoblast-like BeWo (CT/BW) cells, differentiated in villous syncytiotrophoblast (VST/BW) cells, we show that beta-human chorionic gonadotrophin (βhCG) production and cell fusion process are affected in response to IFNγ or GM-CSF. However, those effects are abrogated with OSM by modulating the activation of IFNγ-STAT1 and GM-CSF-STAT5 signaling pathways. OSM stimulation enhances the expression of STAT3, the phosphorylation of STAT3 and SMAD2, and the induction of negative regulators of inflammation (e.g., IL-10 and TGFβ1) and cytokine signaling (e.g., SOCS1 and SOCS3). Using STAT3-deficient VST/BW cells, we show that STAT3 expression is required for OSM to regulate the effects of IFNγ in βhCG and E-cadherin expression. In contrast, OSM retains its modulatory effect on GM-CSF-STAT5 pathway activation even in STAT3-deficient VST/BW cells, suggesting that OSM uses STAT3-dependent and -independent mechanisms to modulate the activation of pro-inflammatory pathways IFNγ-STAT1 and GM-CSF-STAT5. Moreover, STAT3 deficiency in VST/BW cells leads to the production of both a large amount of βhCG and an enhanced expression of activated STAT5 induced by GM-CSF, independently of OSM, suggesting a key role for STAT3 in βhCG production and trophoblast differentiation through STAT5 modulation. In conclusion, our study describes for the first time the critical role played by OSM and STAT3 signaling pathways to preserve and regulate trophoblast biological functions during inflammatory stress.

MiR-150-5p contributes to unexplained recurrent spontaneous abortion by targeting VEGFA and downregulating the PI3K/AKT/mTOR signaling pathway

PURPOSE

The purpose of this study is to investigate the function of miR-150-5p in URSA.

METHOD

Twenty-six chorionic villous tissues were collected to examine the expression of miR-150-5p and VEGFA by using quantitative polymerase chain reaction (qPCR) and western blot assay, respectively. Transwell assay was conducted to assess the migration and invasion ability of trophoblast cells. The dual-luciferase reporter assay was applied to determine the relationship between miR-150-5p and VEGFA in vitro. Relevant signaling pathway protein expression level was measured via western blot assay. Signaling transduction inhibitor LY294002 was used to block PI3K/AKT/mTOR signaling pathway. Finally, in vivo the effect of miR-150-5p on embryonic absorption rate was evaluated in mice.

RESULTS

Clinical samples revealed that miR-150-5p expression was significantly elevated in the villous tissues and serum of URSA patients. Moreover, the overexpressing of miR-150-5p could inhibit both HTR-8/SVneo cell and JAR cell migration, invasion, and restrained PI3K/AKT/mTOR signaling pathway by targeting VEGFA in vitro. This inhibitory effect of miR-150-5p could be reversed by overexpressing the gene of vascular epithelial growth factor A (VEGFA). In contrary, inhibition of miR-150-5p significantly enhanced migration, invasion ability of both HTR-8/SVneo and JAR cells, and also could stimulate PI3K/AKT/mTOR signaling pathway. This promoting effect of miR-150-5p could be ameliorated by LY294002 (PI3K inhibitor). Finally, after miR-150-5p overexpression in vivo, the embryo resorption rate in pregnant mice was increased significantly.

CONCLUSIONS

Overall, these findings imply that miR-150-5p is among the key factors that regulate the pathogenesis of URSA.

Fluid shear stress induces a shift from glycolytic to amino acid pathway in human trophoblasts

BACKGROUND

The human placenta, a tissue with a lifespan limited to the period of pregnancy, is exposed to varying shear rates by maternal blood perfusion depending on the stage of development. In this study, we aimed to investigate the effects of fluidic shear stress on the human trophoblast transcriptome and metabolism.

RESULTS

Based on a trophoblast cell line cultured in a fluidic flow system, changes caused by shear stress were analyzed and compared to static conditions. RNA sequencing and bioinformatics analysis revealed an altered transcriptome and enriched gene ontology terms associated with amino acid and mitochondrial metabolism. A decreased GLUT1 expression and reduced glucose uptake, together with downregulated expression of key glycolytic rate-limiting enzymes, hexokinase 2 and phosphofructokinase 1 was observed. Altered mitochondrial ATP levels and mass spectrometry data, suggested a shift in energy production from glycolysis towards mitochondrial oxidative phosphorylation. This shift in energy production could be supported by increased expression of glutamic-oxaloacetic transaminase variants in response to shear stress as well as under low glucose availability or after silencing of GLUT1. The shift towards amino acid metabolic pathways could be supported by significantly altered amino acid levels, like glutamic acid, cysteine and serine. Downregulation of GLUT1 and glycolytic rate-limiting enzymes, with concomitant upregulation of glutamic-oxaloacetic transaminase 2 was confirmed in first trimester placental explants cultured under fluidic flow. In contrast, high fluid shear stress decreased glutamic-oxaloacetic transaminase 2 expression in term placental explants when compared to low flow rates. Placental tissue from pregnancies with intrauterine growth restriction are exposed to high shear rates and showed also decreased glutamic-oxaloacetic transaminase 2, while GLUT1 was unchanged and glycolytic rate-limiting enzymes showed a trend to be upregulated. The results were generated by using qPCR, immunoblots, quantification of immunofluorescent pictures, padlock probe hybridization, mass spectrometry and FRET-based measurement.

CONCLUSION

Our study suggests that onset of uteroplacental blood flow is accompanied by a shift from a predominant glycolytic- to an alternative amino acid converting metabolism in the villous trophoblast. Rheological changes with excessive fluidic shear stress at the placental surface, may disrupt this alternative amino acid pathway in the syncytiotrophoblast and could contribute to intrauterine growth restriction.

ELF1/PRR11/ARP2/3 promoted trophoblast cells proliferation and motility in early pregnancy

BACKGROUND/OBJECTIVE

Early pregnancy loss (EPL) is a common adverse pregnancy outcome with an incidence of approximately 10-30%. There are many factors that cause EPL, among which the lack of proliferation and invasive properties of trophoblast cells can lead to embryonic development. Therefore, in this study, the molecular biology of trophoblast cells was investigated.

METHODS

Placental villous tissues from EPL patients were collected to explore ELF1 and PRR11 gene expression. The proliferation and migration of trophoblast cells were assessed by MTT, crystalline violet staining, and traswell assays, respectively. Western blotting and RT-qPCR were performed to investigate the relationship between ELF1, PRR11, and ARP2/3. F-actin polymerization and FAK activation were evaluated by immunofluorescence and western blotting. Ultimately, ELF1/PRR11/ARP2/3 expression was verified in the EPL mice model RESULTS: ELF1 and PRR11 were lowly expressed in placental villous tissues from EPL. The overexpression of ELF1 and PRR11 promoted proliferation and migration of trophoblast cells. Moreover, while ELF1 bound to the PRR11 promoter and promoted transcriptional activation. Finally, ELF1/PRR11/ARP2/3 showed low expression in the placental tissue of EPL mice.

CONCLUSION

Our study suggested that PRR11 promoted the motility of trophoblast cells by binding to the ARP2/3 complex to promote F-actin polymerization and FAK activation. In addition, ELF1 bound to the initiation site of PRR11 to promote its transcription. ELF1/PRR11/ARP2/3 may play an important role in EPL.

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.

Hyperglycosylated-hCG: Its Role in Trophoblast Invasion and Intrauterine Growth Restriction

Human chorionic gonadotropin (hCG) is produced by the placenta and its roles have been studied for over a century, being the first known pregnancy-related protein. Although its main role is to stimulate the production of progesterone by corpus luteal cells, hCG does not represent just one biologically active molecule, but a group of at least five variants, produced by different cells and each with different functions. The hyperglycosylated variant of hCG (H-hCG) plays a key role in trophoblast invasion, placental development and fetal growth. During trophoblast invasion, H-hCG promotes extravillous cytotrophoblast cells to infiltrate the decidua, and also to colonize and remodel the spiral arteries in to low resistance, larger-diameter vessels. As fetal growth is heavily reliant on nutrient availability, impaired trophoblast invasion and remodeling of the uterine arteries, leads to a defective perfusion of the placenta and fetal growth restriction. Understanding the function of H-hCG in the evolution of the placenta might unveil new ways to manage and treat fetal growth restriction.

Alpha-2-macroglobulin is involved in the occurrence of early-onset pre-eclampsia via its negative impact on uterine spiral artery remodeling and placental angiogenesis

BACKGROUND

Pre-eclampsia (PE) is one of the leading causes of maternal and fetal morbidity/mortality during pregnancy, and alpha-2-macroglobulin (A2M) is associated with inflammatory signaling; however, the pathophysiological mechanism by which A2M is involved in PE development is not yet understood.

METHODS

Human placenta samples, serum, and corresponding clinical data of the participants were collected to study the pathophysiologic mechanism underlying PE. Pregnant Sprague-Dawley rats were intravenously injected with an adenovirus vector carrying A2M via the tail vein on gestational day (GD) 8.5. Human umbilical artery smooth muscle cells (HUASMCs), human umbilical vein endothelial cells (HUVECs), and HTR-8/SVneo cells were transfected with A2M-expressing adenovirus vectors.

RESULTS

In this study, we demonstrated that A2M levels were significantly increased in PE patient serum, uterine spiral arteries, and feto-placental vasculature. The A2M-overexpression rat model closely mimicked the characteristics of PE (i.e., hypertension in mid-to-late gestation, histological and ultrastructural signs of renal damage, proteinuria, and fetal growth restriction). Compared to the normal group, A2M overexpression significantly enhanced uterine artery vascular resistance and impaired uterine spiral artery remodeling in both pregnant women with early-onset PE and in pregnant rats. We found that A2M overexpression was positively associated with HUASMC proliferation and negatively correlated with cell apoptosis. In addition, the results demonstrated that transforming growth factor beta 1 (TGFβ1) signaling regulated the effects of A2M on vascular muscle cell proliferation described above. Meanwhile, A2M overexpression regressed rat placental vascularization and reduced the expression of angiogenesis-related genes. In addition, A2M overexpression reduced HUVEC migration, filopodia number/length, and tube formation. Furthermore, HIF-1α expression was positively related to A2M, and the secretion of sFLT-1 and PIGF of placental origin was closely related to PE during pregnancy or A2M overexpression in rats.

CONCLUSIONS

Our data showed that gestational A2M overexpression can be considered a contributing factor leading to PE, causing detective uterine spiral artery remodeling and aberrant placental vascularization.

Diagnosis of hydatidiform moles using circulating gestational trophoblasts isolated from maternal blood

INTRODUCTION

Identifying hydatidiform moles (HMs) is crucial due to the risk of gestational trophoblastic neoplasia. When a HM is suspected on clinical findings, surgical termination is recommended. However, in a substantial fraction of the cases, the conceptus is actually a non-molar miscarriage. If distinction between molar and non-molar gestations could be obtained before termination, surgical intervention could be minimized.

METHODS

Circulating gestational trophoblasts (cGTs) were isolated from blood from 15 consecutive women suspected of molar pregnancies in gestational week 6-13. The trophoblasts were individually sorted using fluorescence activated cell sorting. STR analysis targeting 24 loci was performed on DNA isolated from maternal and paternal leukocytes, chorionic villi, cGTs, and cfDNA.

RESULTS

With a gestational age above 10 weeks, cGTs were isolated in 87% of the cases. Two androgenetic HMs, three triploid diandric HMs, and six conceptuses with diploid biparental genome were diagnosed using cGTs. The STR profiles in cGTs were identical to the profiles in DNA from chorionic villi. Eight of the 15 women suspected to have a HM prior to termination had a conceptus with a diploid biparental genome, and thus most likely a non-molar miscarriage.

DISCUSSION

Genetic analysis of cGTs is superior to identify HMs, compared to analysis of cfDNA, as it is not hampered by the presence of maternal DNA. cGTs provide information about the full genome in single cells, facilitating estimation of ploidy. This may be a step towards differentiating HMs from non-HMs before termination.

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

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

Maternal Smoking in the First Trimester and its Consequence on the Early Placenta

Smoking during pregnancy increases the risk of adverse pregnancy outcomes, such as stillbirth and fetal growth restriction. This suggests impaired placental function and restricted nutrient and oxygen supply. Studies investigating placental tissue at the end of pregnancy have revealed increased DNA damage as a potential underlying cause, which is driven by various toxic smoke ingredients and oxidative stress induced by reactive oxygen species (ROS). However, in the first trimester, the placenta develops and differentiates, and many pregnancy pathologies associated with reduced placental function originate here. Therefore, we determined DNA damage in a cohort of first-trimester placental samples of verified smokers and nonsmokers. In fact, we observed an 80% increase in DNA breaks (P < .001) and shortened telomeres by 5.8% (P = .04) in placentas exposed to maternal smoking. Surprisingly, there was a decrease in ROS-mediated DNA damage, ie, 8-oxo-guanidine modifications, in placentas of the smoking group (-41%; P = .021), which paralleled the reduced expression of base excision DNA repair machinery, which restores oxidative DNA damage. Moreover, we observed that the increase in placental oxidant defense machinery expression, which usually occurs at the end of the first trimester in a healthy pregnancy as a result of the full onset of uteroplacental blood flow, was absent in the smoking group. Therefore, in early pregnancy, maternal smoking causes placental DNA damage, contributing to placental malfunction and increased risk of stillbirth and fetal growth restriction in pregnant women. Additionally, reduced ROS-mediated DNA damage along with no increase in antioxidant enzymes suggests a delay in the establishment of physiological uteroplacental blood flow at the end of the first trimester, which may further add to a disturbed placental development and function as a result of smoking in pregnancy.

TOP2A deficiency leads to human recurrent spontaneous abortion and growth retardation of mouse pre-implantation embryos

BACKGROUND

Recurrent spontaneous abortion (RSA), is a dangerous pregnancy-related condition and is a subject of debate in the gynaecology and obstetrics communities. The objective of this study was to determine the function of DNA Topoisomerase II Alpha (TOP2A) in RSA and elucidate the underlying molecular mechanisms.

METHODS

In vitro models of TOP2A-knockdown and -overexpression were generated by transfecting specific sh-RNA lentivirus and overexpression plasmid, respectively. An in vitro TOP2A inhibition model was established by culturing mouse embryos at the two-cell stage in a medium containing PluriSIn2, a TOP2A inhibitor. Immunohistochemical staining was used to analyse expression of TOP2A in villi tissues of patients with RSA. Western blotting and qRT-PCR were used to analyse the expression of TOP2A and proteins involved in trophoblast functions, the FOXO signalling pathway, and the development of pre-implantation embryos. 5-Ethynyl-2'-deoxyuridine staining, TUNEL assay and flow cytometry were used to further evaluate the effect of TOP2A on cell proliferation and apoptosis. Transwell and wound healing assays were used to evaluate migration and invasion. Moreover, the effect of TOP2A inhibitor on embryos was determined by immunofluorescence and mitochondrial-related dyes.

RESULTS

Evaluation of clinical samples revealed that the villi tissues of patients that have experienced RSA had lower TOP2A expression compared with that from women who have experienced normal pregnancy (P < 0.01). In vitro, TOP2A knockdown decreased the proliferation, migration, and invasion of trophoblast cell lines, and increased apoptosis and activation of the FOXO signalling pathway (P < 0.05). Conversely, TOP2A overexpression reversed these effects. Moreover, in vivo experiments confirmed that inhibition of TOP2A impairs trophectoderm differentiation, embryonic mitochondrial function as well as the developmental rate; however, no differences were noted in the expression of zygotic genome activation-related genes.

CONCLUSIONS

Collectively, our data suggest that lower TOP2A expression is related to RSA as it inhibits trophoblast cell proliferation, migration, and invasion by activation of the FOXO signalling pathway. Additionally, TOP2A inhibition resulted in impaired development of pre-implantation embryos in mice, which could be attributed to excessive oxidative stress.

Origins of abnormal placentation: why maternal veins must not be forgotten

The importance of uterine microvascular adaptations during placentation in pregnancy has been well established for decades. Inadequate dilatation of spiral arteries is associated with gestational complications, such as preeclampsia and/or intrauterine growth restriction. More recently, it has become clear that trophoblast cells invade and adapt decidual veins and lymphatic vessels 1 month before spiral arteries become patent and before intervillous space perfusion starts. Normal intervillous space hemodynamics is characterized by high volume flow at low velocity and pressure in the interseptal compartments surrounding the chorionic villi, hereby facilitating efficient maternal-fetal exchange. In case of shallow decidual vein dilatation, intervillous arterial supply exceeds venous drainage. This will cause congestion in the interseptal compartments with subsequently reduced perfusion and increased pressure. An efficient mechanism to counteract venous congestion and safeguard the viability of the conceptus is by reducing arterial inflow via shallow dilatation of the spiral arteries. This review made the case for intervillous space congestion as an unexplored trigger for inadequate spiral artery dilatation during the placentation process, eventually leading to abnormal systemic circulatory dysfunctions. An abnormal maternal venous function can result from an abnormal maternal immune response to paternal antigens with an imbalanced release of vasoactive mediators or can exist before conception. To get the full picture of abnormal placentation, maternal veins must not be forgotten.

Induction of human trophoblast stem cells

Cell reprogramming has allowed unprecedented access to human development, from virtually any genome. However, reprogramming yields pluripotent stem cells that can differentiate into all cells that form a fetus, but not extraembryonic annexes. Therefore, a cellular model allowing study of placental development from a broad genomic repertoire is lacking. Here, we describe an optimized protocol to reprogram somatic cells into human induced trophoblast stem cells (hiTSCs) and convert pluripotent stem cells into human converted TSCs (hcTSCs). This protocol enables much-needed genome-specific placental disease modeling. We also detail extravillous trophoblast and syncytiotrophoblast differentiation protocols from hiTSCs and hcTSCs, a necessary step to validate these cells. In total, this protocol takes 4 months and requires advanced cell culture skills, comparable to those necessary for somatic cell reprogramming into human induced pluripotent stem cells.

Accessing the human trophoblast stem cell state from pluripotent and somatic cells

Trophoblasts are specialized epithelial cells that perform critical functions during blastocyst implantation and mediate maternal-fetal communication during pregnancy. However, our understanding of human trophoblast biology remains limited since access to first-trimester placental tissue is scarce, especially between the first and fourth weeks of development. Moreover, animal models inadequately recapitulate unique aspects of human placental physiology. In the mouse system, the isolation of self-renewing trophoblast stem cells has provided a valuable in vitro model system of placental development, but the derivation of analogous human trophoblast stem cells (hTSCs) has remained elusive until recently. Building on a landmark study reporting the isolation of bona fide hTSCs from blastocysts and first-trimester placental tissues in 2018, several groups have developed methods to derive hTSCs from pluripotent and somatic cell sources. Here we review the biological and molecular properties that define authentic hTSCs, the trophoblast potential of distinct pluripotent states, and methods for inducing hTSCs in somatic cells by direct reprogramming. The generation of hTSCs from pluripotent and somatic cells presents exciting opportunities to elucidate the molecular mechanisms of human placental development and the etiology of pregnancy-related diseases.

Palmitic Acid Impedes Extravillous Trophoblast Activity by Increasing MRP1 Expression and Function

Normal function of placental extravillous trophoblasts (EVTs), which are responsible for uteroplacental vascular remodeling, is critical for adequate delivery of oxygen and nutrients to the developing fetus and normal fetal programming. Proliferation and invasion of spiral arteries by EVTs depends upon adequate levels of folate. Multidrug resistance-associated protein 1 (MRP1), which is an efflux transporter, is known to remove folate from these cells. We hypothesized that palmitic acid increases MRP1-mediated folate removal from EVTs, thereby interfering with EVTs' role in early placental vascular remodeling. HTR-8/SVneo and Swan-71 cells, first trimester human EVTs, were grown in the absence or presence of 0.5 mM and 0.7 mM palmitic acid, respectively, for 72 h. Palmitic acid increased ABCC1 gene expression and MRP1 protein expression in both cell lines. The rate of folate efflux from the cells into the media increased with a decrease in migration and invasion functions in the cultured cells. Treatment with N-acetylcysteine (NAC) prevented the palmitic acid-mediated upregulation of MRP1 and restored invasion and migration in the EVTs. Finally, in an ABCC1 knockout subline of Swan-71 cells, there was a significant increase in invasion and migration functions. The novel finding in this study that palmitic acid increases MRP1-mediated folate efflux provides a missing link that helps to explain how maternal consumption of saturated fatty acids compromises the in utero environment.

Human Leukocyte Antigen HLA-C, HLA-G, HLA-F and HLA-E placental profiles are altered in Early Severe Preeclampsia and Preterm Birth with Chorioamnionitis

BACKGROUND

The extravillous trophoblast expresses each of the non-classical MHC class I antigens - HLA-E, F, and G and a single classical class I antigen HLA-C. We recently demonstrated dynamic expression patterns of HLA-C, G and F during early EVT invasion and placentation.

OBJECTIVE

In this study we investigate the hypothesis that the immune inflammatory mediated complications of pregnancy such as early preeclampsia and preterm labor, may show altered expression profiles of non-classical HLA.

STUDY DESIGN

Real time q-PCR, western blot and immunohistochemistry were performed on placental villous tissues and basal plate sections from term non-laboring deliveries, preterm deliveries and severe early onset preeclampsia both with and without small for gestational age neonates.

RESULTS

HLA-G is strongly and exclusively expressed by the EVT within the placental basal plate and its levels increase in pregnancies complicated by severe early onset PE with SGA neonates as compared to healthy term controls. HLA-C shows a similar profile in the EVT of PE pregnancies, but significantly decreases in the villous placenta. HLA-F protein levels are decreased in both EVT and villous placenta of severe early onset PE pregnancies both with and without SGA babies as compared to Term and PTB deliveries. HLA-E decreases in blood vessels in placentas from PE pregnancies as compared to Term and PTB deliveries. HLA-F and HLA-C are increased in the placenta of PTBs with chorioamnionitis as compared to idiopathic PTB.

CONCLUSION

Dysregulation of placental HLA expression at the maternal fetal interface may contribute to the compromised maternal tolerance in PTB with chorioamnionitis and excessive maternal systemic inflammation associated with severe early onset PE.

Transforming growth factor-β signaling governs the differentiation program of extravillous trophoblasts in the developing human placenta

Abnormal placentation has been noticed in a variety of pregnancy complications such as miscarriage, early-onset preeclampsia, and fetal growth restriction. Defects in the developmental program of extravillous trophoblasts (EVTs), migrating from placental anchoring villi into the maternal decidua and its vessels, is thought to be an underlying cause. Yet, key regulatory mechanisms controlling commitment and differentiation of the invasive trophoblast lineage remain largely elusive. Herein, comparative gene expression analyses of HLA-G-purified EVTs, isolated from donor-matched placenta, decidua, and trophoblast organoids (TB-ORGs), revealed biological processes and signaling pathways governing EVT development. In particular, bioinformatics analyses and manipulations in different versatile trophoblast cell models unraveled transforming growth factor-β (TGF-β) signaling as a crucial pathway driving differentiation of placental EVTs into decidual EVTs, the latter showing enrichment of a secretory gene signature. Removal of Wingless signaling and subsequent activation of the TGF-β pathway were required for the formation of human leukocyte antigen-G⁺ (HLA-G⁺) EVTs in TB-ORGs that resemble in situ EVTs at the level of global gene expression. Accordingly, TGF-β-treated EVTs secreted enzymes, such as DAO and PAPPA2, which were predominantly expressed by decidual EVTs. Their genes were controlled by EVT-specific induction and genomic binding of the TGF-β downstream effector SMAD3. In summary, TGF-β signaling plays a key role in human placental development governing the differentiation program of EVTs.

Increased Colocalization and Interaction Between Decidual Protein Kinase A and Insulin-like Growth Factor-Binding Protein-1 in Intrauterine Growth Restriction

Increased phosphorylation of decidual insulin-like growth factor-binding protein-1 (IGFBP-1) can contribute to intrauterine growth restriction (IUGR) by decreasing the bioavailability of insulin-like growth factor-1 (IGF-1). However, the molecular mechanisms regulating IGFBP-1 phosphorylation at the maternal-fetal interface are poorly understood. Protein kinase A (PKA) is required for normal decidualization. Consensus sequences for PKA are present in IGFBP-1. We hypothesized that the expression/interaction of PKA with decidual IGFBP-1 is increased in IUGR. Parallel reaction monitoring-mass spectrometry (PRM-MS) identified multiple PKA peptides (n=>30) co-immunoprecipitating with IGFBP-1 in decidualized primary human endometrial stromal cells (HESC). PRM-MS also detected active PKA^pThr197 and greater site-specific IGFBP-1 phosphorylation^{(pSer119), (pSer98+pSer101) (pSer169+pSer174)} in response to hypoxia. Hypoxia promoted colocalization [dual immunofluorescence (IF)] of PKA with IGFBP-1 in decidualized HESC. Colocalization (IF) and interaction (proximity ligation assay) of PKA and IGFBP-1 were increased in decidua collected from placenta of human IUGR pregnancies (n=8) compared with decidua from pregnancies with normal fetal growth. Similar changes were detected in decidual PKA/IGFBP-1 using placenta from baboons subjected to maternal nutrient reduction (MNR) vs controls (n=3 each). In baboons, these effects were evident in MNR at gestational day 120 prior to IUGR onset. Increased PKA-mediated phosphorylation of decidual IGFBP-1 may contribute to decreased IGF-1 bioavailability in the maternal-fetal interface in IUGR.

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.

(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.

Leveraging Optimized Transcriptomic and Personalized Stem Cell Technologies to Better Understand Syncytialization Defects in Preeclampsia

Understanding the process of human placentation is important to the development of strategies for treatment of pregnancy complications. Several animal and in vitro human model systems for the general study human placentation have been used. The field has expanded rapidly over the past decades to include stem cell-derived approaches that mimic preclinical placental development, and these stem cell-based models have allowed us to better address the physiology and pathophysiology of normal and compromised trophoblast (TB) sublineage development. The application of transcriptomic approaches to these models has uncovered limitations that arise when studying the distinctive characteristics of the large and fragile multinucleated syncytiotrophoblast (STB), which plays a key role in fetal-maternal communication during pregnancy. The extension of these technologies to induced pluripotent stem cells (iPSCs) is just now being reported and will allow, for the first time, a reproducible and robust approach to the study of the developmental underpinnings of late-manifesting diseases such as preeclampsia (PE) and intrauterine growth retardation in a manner that is patient- and disease-specific. Here, we will first focus on the application of various RNA-seq technologies to TB, prior limitations in fully accessing the STB transcriptome, and recent leveraging of single nuclei RNA sequencing (snRNA-seq) technology to improve our understanding of the STB transcriptome. Next, we will discuss new stem-cell derived models that allow for disease- and patient-specific study of pregnancy disorders, with a focus on the study of STB developmental abnormalities in PE that combine snRNA-seq approaches and these new in vitro models.

UHRF1 shapes both the trophoblast invasion and decidual macrophage differentiation in early pregnancy

Trophoblasts play critical roles in establishment and maintenance of a normal pregnancy. Their dysfunction in early pregnancy is closely related to pregnancy-related diseases, including recurrent pregnancy loss (RPL). Epigenetic modifications dynamically change during pregnancy; however, the role of the epigenetic modifier UHRF1 in trophoblast regulation remains unknown. This is the first study to show that UHRF1 expression was localized in the cytoplasm of cytotrophoblasts, syncytiotrophoblasts, and villi columns, and decreased in the villi of patients with RPL. The invasion and cell viability in a UHRF1 knockdown trophoblast cell line were significantly decreased. In addition, the mRNA expression profiles of Swan71 cells were partially altered by UHRF1 knockdown. The altered immune-related genes were screened out and the pro-inflammatory TH1-type chemokine/cytokines CXCL2 and IL-1β were identified as the most promising targets of UHRF1 in the trophoblasts, which were significantly increased in the UHRF1 knockdown Swan71 cells, villi, and serum from patients with RPL. The macrophages treated with the supernatants of UHRF1 knockdown Swan71 cells were polarized to the M1 phenotype and secreted high levels of pro-inflammatory cytokines, which might be driven by the activated MyD88/NF-κB signaling pathway and mediated by the increased expression of CXCR2 and IL-1R1 (CXCL2 and IL-1β receptors, respectively). In addition, the supernatants of UHRF1 knockdown Swan71 cells showed stronger chemotaxis to macrophages than those from the controls. Our findings highlight the previously unknown roles of UHRF1 as one of the key regulators on the trophoblasts and their cross-talk with local immune cells, and demonstrate a potential approach for RPL intervention.

Failure of physiological transformation and spiral artery atherosis: their roles in preeclampsia

Physiological transformation with remodeling of the uteroplacental spiral arteries is key to a successful placentation and normal placental function. It is an intricate process that involves, but is not restricted to, complex interactions between maternal decidual immune cells and invasive trophoblasts in the uterine wall. In normal pregnancy, the smooth muscle cells of the arterial tunica media of uteroplacental spiral arteries are replaced by invading trophoblasts and fibrinoid, and the arterial diameter increases 5- to 10-fold. Poor remodeling of the uteroplacental spiral arteries is linked to early-onset preeclampsia and several other major obstetrical syndromes, including fetal growth restriction, placental abruption, and spontaneous preterm premature rupture of membranes. Extravillous endoglandular and endovenous trophoblast invasions have recently been put forth as potential contributors to these syndromes as well. The well-acknowledged disturbed extravillous invasion of maternal spiral arteries in preeclampsia is summarized, as are briefly novel concepts of disturbed extravillous endoglandular and endovenous trophoblast invasions. Acute atherosis is a foam cell lesion of the uteroplacental spiral arteries associated with poor remodeling. It shares some morphologic features with early stages of atherosclerosis, but several molecular differences between these lesions have also recently been revealed. Acute atherosis is most prevalent at the maternal-fetal interface, at the tip of the spiral arteries. The localization of acute atherosis downstream of poorly remodeled arteries suggests that alterations in blood flow may trigger inflammation and foam cell development. Acute atherosis within the decidua basalis is not, however, confined to unremodeled areas of spiral arteries or to hypertensive disorders of pregnancy and may even be present in some clinically uneventful pregnancies. Given that foam cells of atherosclerotic lesions are known to arise from smooth muscle cells or macrophages activated by multiple types of inflammatory stimulation, we have proposed that multiple forms of decidual vascular inflammation may cause acute atherosis, with or without poor remodeling and/or preeclampsia. Furthermore, we propose that acute atherosis may develop at different gestational ages, depending on the type and degree of the inflammatory insult. This review summarizes the current knowledge of spiral artery remodeling defects and acute atherosis in preeclampsia. Some controversies will be presented, including endovascular and interstitial trophoblast invasion depths, the concept of 2-stage trophoblast invasion, and whether the replacement of maternal spiral artery endothelium by fetal endovascular trophoblasts is permanent. We will discuss the role of acute atherosis in the pathophysiology of preeclampsia and short- and long-term health correlates. Finally, we suggest future opportunities for research on this intriguing uteroplacental interface between the mother and fetus.

WNT and NOTCH signaling in human trophoblast development and differentiation

Correct development of the human placenta and its differentiated epithelial cells, syncytial trophoblasts (STBs) and extravillous trophoblasts (EVTs), is crucial for a successful pregnancy outcome. STBs develop by cell fusion of mononuclear cytotrophoblasts (CTBs) in placental floating villi, whereas migratory EVTs originate from specialized villi anchoring to the maternal decidua. Defects in trophoblast differentiation have been associated with severe pregnancy disorders such as early-onset preeclampsia and fetal growth restriction. However, the evolutionary pathways underlying normal and adverse placentation are poorly understood. Herein, we discuss Wingless (WNT) and NOTCH signaling, two pathways that play pivotal roles in human placenta and trophoblast development. Whereas WNT is necessary for expansion of trophoblast progenitors and stem cells, NOTCH1 is required for proliferation and survival of EVT precursors. Differentiation of the latter is orchestrated by a switch in NOTCH receptor expression as well as by changes in WNT ligands and their downstream effectors.

Intersection of regulatory pathways controlling hemostasis and hemochorial placentation

Hemochorial placentation is characterized by the development of trophoblast cells specialized to interact with the uterine vascular bed. We utilized trophoblast stem (TS) cell and mutant rat models to investigate regulatory mechanisms controlling trophoblast cell development. TS cell differentiation was characterized by acquisition of transcript signatures indicative of an endothelial cell-like phenotype, which was highlighted by the expression of anticoagulation factors including tissue factor pathway inhibitor (TFPI). TFPI localized to invasive endovascular trophoblast cells of the rat placentation site. Disruption of TFPI in rat TS cells interfered with development of the endothelial cell-like endovascular trophoblast cell phenotype. Similarly, TFPI was expressed in human invasive/extravillous trophoblast (EVT) cells situated within first-trimester human placental tissues and following differentiation of human TS cells. TFPI was required for human TS cell differentiation to EVT cells. We next investigated the physiological relevance of TFPI at the placentation site. Genome-edited global TFPI loss-of-function rat models revealed critical roles for TFPI in embryonic development, resulting in homogeneous midgestation lethality prohibiting analysis of the role of TFPI as a regulator of the late-gestation wave of intrauterine trophoblast cell invasion. In vivo trophoblast-specific TFPI knockdown was compatible with pregnancy but had profound effects at the uterine-placental interface, including restriction of the depth of intrauterine trophoblast cell invasion while leading to the accumulation of natural killer cells and increased fibrin deposition. Collectively, the experimentation implicates TFPI as a conserved regulator of invasive/EVT cell development, uterine spiral artery remodeling, and hemostasis at the maternal-fetal interface.

Placental Endocrine Activity: Adaptation and Disruption of Maternal Glucose Metabolism in Pregnancy and the Influence of Fetal Sex

The placenta is an endocrine fetal organ, which secretes a plethora of steroid- and proteo-hormones, metabolic proteins, growth factors, and cytokines in order to adapt maternal physiology to pregnancy. Central to the growth of the fetus is the supply with nutrients, foremost with glucose. Therefore, during pregnancy, maternal insulin resistance arises, which elevates maternal blood glucose levels, and consequently ensures an adequate glucose supply for the developing fetus. At the same time, maternal β-cell mass and function increase to compensate for the higher insulin demand. These adaptations are also regulated by the endocrine function of the placenta. Excessive insulin resistance or the inability to increase insulin production accordingly disrupts physiological modulation of pregnancy mediated glucose metabolism and may cause maternal gestational diabetes (GDM). A growing body of evidence suggests that this adaptation of maternal glucose metabolism differs between pregnancies carrying a girl vs. pregnancies carrying a boy. Moreover, the risk of developing GDM differs depending on the sex of the fetus. Sex differences in placenta derived hormones and bioactive proteins, which adapt and modulate maternal glucose metabolism, are likely to contribute to this sexual dimorphism. This review provides an overview on the adaptation and maladaptation of maternal glucose metabolism by placenta-derived factors, and highlights sex differences in this regulatory network.

Crosstalk Between Trophoblast and Macrophage at the Maternal-Fetal Interface: Current Status and Future Perspectives

The immune tolerance microenvironment is crucial for the establishment and maintenance of pregnancy at the maternal-fetal interface. The maternal-fetal interface is a complex system containing various cells, including lymphocytes, decidual stromal cells, and trophoblasts. Macrophages are the second-largest leukocytes at the maternal-fetal interface, which has been demonstrated to play essential roles in remodeling spiral arteries, maintaining maternal-fetal immune tolerance, and regulating trophoblast's biological behaviors. Many researchers, including us, have conducted a series of studies on the crosstalk between macrophages and trophoblasts at the maternal-fetal interface: on the one hand, macrophages can affect the invasion and migration of trophoblasts; on the other hand, trophoblasts can regulate macrophage polarization and influence the state of the maternal-fetal immune microenvironment. In this review, we systemically introduce the functions of macrophages and trophoblasts and the cell-cell interaction between them for the establishment and maintenance of pregnancy. Advances in this area will further accelerate the basic research and clinical translation of reproductive medicine.

Overexpression of let-7b exerts beneficial effects on the functions of human placental trophoblasts by activating the ERK1/2 signaling pathway

The present work aimed to explore let-7b's molecular mechanisms that regulate the functions of placental trophoblasts and to examine placental let-7b expression in human pre-eclampsia (PE). Human trophoblast HTR-8/SVneo cells underwent transduction with control and let-7b overexpressing lentiviruses, respectively. Cell proliferation assessment utilized cell counting kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) assays. Apoptosis, autophagy, inflammation, epithelial-to-mesenchymal transition (EMT), and ERK1/2 signaling-associated proteins were assessed by immunoblot. Placental tissue samples were collected from women with normal pregnancy (n = 20) and PE patients (n = 14). Let-7b overexpression in HTR-8/SVneo cells remarkably induced cell proliferation and invasion, suppressed apoptosis and autophagy, and resulted in decreased tumor necrosis factorα (TNF-α) expression and increased interleukin 6 (IL-6) expression in trophoblasts. Notably, the beneficial effects of let-7b overexpression, including cell invasion and EMT, were largely reversed by treatment with U0126, an indirect ERK1/2 signaling inhibitor, in these cells. TGF-β receptor type-1 (TGFBR1) overexpression weakened let-7b's functions in ERK pathway activation and invasion in trophoblasts. Placental tissue specimens from PE cases demonstrated significantly lower let-7b expression compared with normal controls. Overexpression of let-7b exerts beneficial effects on the functions of human placental trophoblasts via ERK1/2 signaling, and placental let-7b is downregulated in human PE. These findings suggest let-7b is a promising biomarker for the prospective diagnosis and targeted therapy of PE.

Downregulation of fascin in the first trimester placental villi is associated with early recurrent miscarriage

Inadequate trophoblast proliferation, shallow invasion and exaggerated rate of trophoblast apoptosis are implicated in early recurrent miscarriage (ERM). However, the mechanistic bases of this association have not been fully established. We aimed at investigating the involvement of fascin, an actin-bundling protein, in trophoblast activities and ERM. We found that fascin was downregulated in the cytotrophoblasts (CTBs) and distal cytotrophoblasts (DCTs) of ERM placentae. Knockdown of fascin altered cellular and nucleolar morphology, and inhibited the proliferation but increased apoptosis of trophoblastic HTR8/SVneo cells. Furthermore, fascin knockdown decreased the expression of transcription factors such as Snail1/2, Twist and Zeb1/2, mesenchymal molecules such as Vimentin and N-cadherin, and the protein expression of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphorylates signal transducer and activator of transcript 3 (STAT3). Exposure of HTR-8/SVneo cells to hypoxia reoxygenation (H/R) decreased fascin expression to affect the cells' invasion. Our results indicate for the first time that the downregulation of fascin is involved in the pathogenesis of early recurrent miscarriage; and hence a potential therapeutic target against the disease.

ERK1/2 phosphorylation and IL-6 production are involved in the differential susceptibility to Toxoplasma gondii infection in three types of human (cyto/ syncytio/ extravillous) trophoblast cells

During pregnancy, Toxoplasma gondii can triggers serious manifestations and potentially affect the fetal development. In this scenario, differences in susceptibility of trophoblast cells to T. gondii infection might be evaluated in order to establish new therapeutic approaches capable of interfering in the control of fetal infection by T. gondii. This study aimed to evaluate the susceptibility of cytotrophoblast, syncytiotrophoblast and extravillous trophoblast cells to T. gondii infection. Our data demonstrate that HTR-8/SVneo cells (extravillous trophoblast cells) present higher susceptibility to T. gondii infection when compared to syncytiotrophoblast and cytotrophoblast cells, whereas syncytiotrophoblast was the cell type more resistant to the parasite infection. Also, cytotrophoblast and syncytiotrophoblast cells produced significantly more IL-6 than HTR-8/SVneo cells. On the other hand, HTR-8/SVneo cells showed higher ERK1/2 phosphorylation than cytotrophoblast and syncytiotrophoblast cells. ERK1/2 inhibition reduced T. gondii infection and increased IL-6 production in HTR-8/SVneo cells. Thus, it is plausible to conclude that the greater susceptibility of HTR-8/SVneo cells to infection by T. gondii is related to a higher ERK1/2 phosphorylation and lower levels of IL-6 in these cells compared to other cells, suggesting that these mediators may be important to favor the parasite infection in this type of trophoblastic population.

Examination of FERMT1 expression in placental chorionic villi and its role in HTR8-SVneo cell invasion

Transmembrane integrin receptors mediate cell-extracellular matrix as well as cell-cell adhesion. As placental trophoblast cells undergo differentiation they display changes in integrin expression or switching, but the mechanism(s) of integrin activation that supports this differentiation is still unknown. The Fermitin family of adapter proteins (FERMT 1-3) are integrin activators that mediate integrin-mediated signaling. In this study, we examined the spatiotemporal pattern of expression of FERMT1 in human chorionic villi throughout gestation and its role in HTR8-SVneo substrate adhesion and invasion. Placental villous tissue was obtained from patients undergoing elective terminations at weeks 8-14, as well as from term deliveries at weeks 37-40 and analyzed by immunofluorescence. Additionally, HTR8-SVneo trophoblast cells were transfected with FERMT1-specific siRNA or non-targeting siRNA (control) and used in cell-substrate adhesion as well as invasion assays. FERMT1 was primarily localized to membrane-associated regions at the base or around the periphery of the villous cytotrophoblast and proximal as well as distal cell column trophoblast. FERMT1 was also localized to endothelial cells of blood vessels in chorionic villi. siRNA-mediated depletion of FERMT1 in HTR8-SVneo cells did not markedly alter HTR8-SVneo cell-substrate adhesion but did significantly decrease invasion (P < 0.05) compared to control cells. These novel findings identify the presence of the integrin activator FERMT1 in trophoblast cells and that FERMT1 can regulate HTR8-SVneo cell invasion. FERMT1 may directly influence integrin activation and the subsequent integrin-mediated signaling and differentiation that underlies the acquisition of the invasive trophoblast phenotype in vivo.

Maternal platelets pass interstices of trophoblast columns and are not activated by HLA-G in early human pregnancy

In early human gestation, maternal arterial blood flow into the intervillous space of the developing placenta is obstructed by invaded trophoblasts, which form cellular plugs in uterine spiral arteries. These trophoblast plugs have recently been described to be loosely cohesive with clear capillary-sized channels into the intervillous space by 7 weeks of gestation. Here, we analysed localisation of maternal platelets at the maternal-foetal interface of human first trimester pregnancy, and tested the hypothesis whether HLA-G, which is primarily expressed by extravillous trophoblasts, affects aggregation and adhesion of isolated platelets. Immunohistochemistry of first trimester placental sections localised maternal platelets in vessel-like channels and adjacent intercellular gaps of extravillous trophoblasts in distal parts of columns. Furthermore, this localisation was confirmed by transmission electron microscopy. Neither co-incubation of HLA-G overexpressing JAR cells with isolated platelets, nor incubation with cell-derived soluble HLA-G or recombinant HLA-G affected platelet adhesion and aggregation. Our study suggests that maternal platelets flow through vessel-like channels of distal trophoblast columns and spread into adjacent lateral intercellular gaps, where platelet-derived factors could contribute to trophoblast differentiation into the invasive phenotype.

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.

Hydatidiform mole diagnostics using circulating gestational trophoblasts isolated from maternal blood

Background

In gestational trophoblastic disease, the prognosis is related to the genetic constitution. In some cases, taking a biopsy is contraindicated.

Methods

In a pregnant woman, ultrasound scanning suggested hydatidiform mole. To explore if the genetic constitution can be established without taking a biopsy (or terminating the pregnancy), cell‐free DNA and circulating gestational trophoblasts were isolated from maternal blood before evacuation of the uterus. The evacuated tissue showed the morphology of a complete hydatidiform mole. Without prior whole‐genome amplification, short tandem repeat analysis of 24 DNA markers was performed on the samples, and on DNA isolated from evacuated tissue, and from the blood of the patient and her partner.

Results

Identical genetic results were obtained in each of three circulating gestational trophoblasts and the evacuated tissue, showing that this conceptus had a diploid androgenetic nuclear genome. In contrast, analysis of cell‐free DNA was less informative and less specific due to the inherent presence of cell‐free DNA from the patient.

Conclusion

Our results show that it is possible to isolate and analyze circulating gestational trophoblasts originating in a pregnancy without maternal nuclear genome. For diagnosing gestational trophoblastic diseases, genotyping circulating gestational trophoblasts appears to be superior to analysis of cell‐free DNA.

The endothelial protein C receptor plays an essential role in the maintenance of pregnancy

Placenta-mediated pregnancy complications are a major challenge in the management of maternal-fetal health. Maternal thrombophilia is a suspected risk factor, but the role of thrombotic processes in these complications has remained unclear. Endothelial protein C receptor (EPCR) is an anticoagulant protein highly expressed in the placenta. EPCR autoantibodies and gene variants are associated with poor pregnancy outcomes. In mice, fetal EPCR deficiency results in placental failure and in utero death. We show that inhibition of molecules involved in thrombin generation or in the activation of maternal platelets allows placental development and embryonic survival. Nonetheless, placentae exhibit venous thrombosis in uteroplacental circulation associated with neonatal death. In contrast, maternal EPCR deficiency results in clinical and histological features of placental abruption and is ameliorated with concomitant Par4 deficiency. Our findings unveil a causal link between maternal thrombophilia, uterine hemorrhage, and placental abruption and identify Par4 as a potential target of therapeutic intervention.

Densities of decidual high endothelial venules correlate with T-cell influx in healthy pregnancies and idiopathic recurrent pregnancy losses

STUDY QUESTION

Do high endothelial venules (HEVs) appear in the uterus of healthy and pathological pregnancies?

SUMMARY ANSWER

Our study reveals that HEVs are present in the non-pregnant endometrium and decidua parietalis (decP) but decline upon placentation in decidua basalis (decB) and are less abundant in decidual tissues from idiopathic, recurrent pregnancy losses (RPLs).

WHAT IS KNOWN ALREADY

RPL is associated with a compromised decidual vascular phenotype.

STUDY DESIGN, SIZE, DURATION

Endometrial (n = 29) and first trimester decidual (n = 86, 6-12th week of gestation) tissue samples obtained from endometrial biopsies or elective pregnancy terminations were used to determine the number of HEVs and T cells. In addition, quantification of HEVs and immune cells was performed in a cohort of decidual tissues from RPL (n = 25).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Position and frequency of HEVs were determined in non-pregnant endometrial as well as decidual tissue sections using immunofluorescence (IF) staining with antibodies against E-selectin, intercellular adhesion molecule, von Willebrand factor, ephrin receptor B4, CD34 and a carbohydrate epitope specific to HEVs (MECA-79). Immune cell distribution and characterization was determined by antibodies recognizing CD45 and CD3 by IF staining- and flow cytometry-based analyses. Antibodies against c-c motif chemokine ligand 21 (CCL21) and lymphotoxin-beta were used in IF staining and Western blot analyses of decidual tissues.

MAIN RESULTS AND THE ROLE OF CHANCE

Functional HEVs are found in high numbers in the secretory endometrium and decP but decline in numbers upon placentation in decB (P ≤ 0.001). Decidua parietalis tissues contain higher levels of the HEV-maintaining factor lymphotoxin beta and decP-associated HEVs also express CCL21 (P ≤ 0.05), a potent T-cell chemoattractant. Moreover, there is a positive correlation between the numbers of decidual HEVs and the abundance of CD3+ cells in decidual tissue sections (P ≤ 0.001). In-depth analysis of a RPL tissue collection revealed a decreased decB (P ≤ 0.01) and decP (P ≤ 0.01) HEV density as well as reduced numbers of T cells in decB (P ≤ 0.05) and decP (P ≤ .001) sections when compared with age-matched healthy control samples. Using receiver-operating characteristics analyses, we found significant predictive values for the ratios of CD3/CD45 (P < 0.001) and HEVs/total vessels (P < 0.001) for the occurrence of RPL.

LIMITATIONS, REASONS FOR CAUTION

Analyses were performed in first trimester decidual tissues from elective terminations of pregnancy or non-pregnant endometrium samples from patients diagnosed with non-endometrial pathologies including cervical polyps, ovarian cysts and myomas. First trimester decidual tissues may include pregnancies which potentially would have developed placental disorders later in gestation. In addition, our cohort of non-pregnant endometrium may not reflect the endometrial vascular phenotype of healthy women. Finally, determination of immune cell distributions in the patient cohorts studied may be influenced by the different modes of tissue derivation. Pregnancy terminations were performed by surgical aspiration, endometrial tissues were obtained by biopsies and RPL tissues were collected after spontaneous loss of pregnancy.

WIDER IMPLICATIONS OF THE FINDINGS

In this study, we propose an inherent mechanism by which the endometrium and in particular the decidua control T-cell recruitment. By demonstrating reduced HEV densities and numbers of T cells in decB and decP tissues of RPL samples we further support previous findings reporting an altered vascular phenotype in early pregnancy loss. Altogether, the findings provide important information to further decipher the etiologies of unexplained RPL.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Austrian Science Fund (P31470 B30 to M.K.) and by the Austrian National Bank (17613ONB to J.P.). There are no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

The Maternal-Fetal Interface in Small-for-Gestational-Age Pregnancies Is Associated With a Reduced Quantity of Human Decidual NK Cells With Weaker Functional Ability

Small for gestational age (SGA) refers to a birth weight that is less than the 10th percentile of the mean weight of infants at the same gestational age. This condition is associated with a variety of complications, and a high risk of cardiovascular and cerebrovascular diseases in adulthood. Decidual natural killer (dNK) cells at the maternal–fetal interface have received significant research attention in terms of normal pregnancy or miscarriage; however, data relating to SGA are limited. In this study, we aimed to investigate the characteristics and regulatory role of dNK cells at the maternal–fetal interface in SGA. Using immunofluorescence assays, we found that dNK cells maintained close contact with extra-villous trophoblasts, and the proportion of dNK cells in SGA decreased more than in appropriate for gestational age (AGA). Flow cytometry also showed that there was a significantly lower percentage of dNK cells in SGA (25.01 ± 2.43%) than in AGA (34.25 ± 2.30%) (p = 0.0103). The expression of the inhibitory receptor NKG2A on dNK cells and the secretion levels of both perforin and TGF-β1 from dNK cells were significantly higher in SGA than in AGA, while the cytotoxicity of dNK cells in SGA against K562 cells was attenuated. Compared to AGA, the functional ability of dNK cells in SGA showed significant functional impairment in promoting proliferation, migration, invasion, and tube formation in trophoblast cells or vascular endothelial cells. The abnormal function of dNK cells may affect fetal growth and development, and could therefore participate in the pathogenesis of SGA.

Tracking placental development in health and disease

Pre-eclampsia and fetal growth restriction arise from disorders of placental development and have some shared mechanistic features. Initiation is often rooted in the maldevelopment of a maternal-placental blood supply capable of providing for the growth requirements of the fetus in later pregnancy, without exerting undue stress on maternal body systems. Here, we review normal development of a placental bed with a safe and adequate blood supply and a villous placenta-blood interface from which nutrients and oxygen can be extracted for the growing fetus. We consider disease mechanisms that are intrinsic to the maternal environment, the placenta or the interaction between the two. Systemic signalling from the endocrine placenta targets the maternal endothelium and multiple organs to adjust metabolism for an optimal pregnancy and later lactation. This signalling capacity is skewed when placental damage occurs and can deliver a dangerous pathogenic stimulus. We discuss the placental secretome including glycoproteins, microRNAs and extracellular vesicles as potential biomarkers of disease. Angiomodulatory mediators, currently the only effective biomarkers, are discussed alongside non-invasive imaging approaches to the prediction of disease risk. Identifying the signs of impending pathology early enough to intervene and ameliorate disease in later pregnancy remains a complex and challenging objective.

Go with the Flow-Trophoblasts in Flow Culture

With establishment of uteroplacental blood flow, the perfused fetal chorionic tissue has to deal with fluid shear stress that is produced by hemodynamic forces across different trophoblast subtypes. Amongst many other cell types, trophoblasts are able to sense fluid shear stress through mechanotransduction. Failure in the adaption of trophoblasts to fluid shear stress is suggested to contribute to pregnancy disorders. Thus, in the past twenty years, a significant body of work has been devoted to human- and animal-derived trophoblast culture under microfluidic conditions, using a rather broad range of different fluid shear stress values as well as various different flow systems, ranging from commercially 2D to customized 3D flow culture systems. The great variations in the experimental setup reflect the general heterogeneity in blood flow through different segments of the uteroplacental circulation. While fluid shear stress is moderate in invaded uterine spiral arteries, it drastically declines after entrance of the maternal blood into the wide cavity of the intervillous space. Here, we provide an overview of the increasing body of evidence that substantiates an important influence of maternal blood flow on several aspects of trophoblast physiology, including cellular turnover and differentiation, trophoblast metabolism, as well as endocrine activity, and motility. Future trends in trophoblast flow culture will incorporate the physiological low oxygen conditions in human placental tissue and pulsatile blood flow in the experimental setup. Investigation of trophoblast mechanotransduction and development of mechanosome modulators will be another intriguing future direction.

The Number of Circulating Fetal Extravillous Trophoblasts Varies from Gestational Week 6 to 20

Cell-based non-invasive prenatal testing (cbNIPT) based on circulating fetal extravillous trophoblasts (fEVTs) has shown to be possible in gestational week (GW) 10–13. Prenatal testing is relevant for a wider time period than GW 10–13, but it is unclear if fEVTs are present in sufficient numbers for cbNIPT at other time points during pregnancy. We present the first longitudinal study where the number of circulating fEVTs was determined from the mid first trimester to the mid second, specifically GW 6–8, 12–13, and 19–20. Blood samples from 13 women opting for assisted reproduction were collected at GW 6–8, 12–13, and 19–20. fEVTs were enriched using a magnetic-activated cell sorting system, stained with anti-cytokeratin antibodies, and fEVTs were identified with the use of a MetaSystem fluorescence microscope scanner. Blood samples drawn at GW 6–8 yielded an average of 5.5 fEVTs per 30 mL of blood. This increased significantly to an average of 11.8 in GW 12–13 (P value: 0.0070, Mann-Whitney test), and decreased significantly to an average of 5.3 in GW 19–20 (P value: 0.0063, Mann-Whitney test). In 9 out of 13 cases, the number of fEVTs peaked in GW 12–13 compared to GW 6–8 and GW 19–20. For the majority of cases, fEVTs can be identified at GW 6–8 and GW 19–20, but the highest number of fEVTs is observed at GW 12–13 indicating this is the optimal time point for cbNIPT.

Maternal Obesity Alters Placental Cell Cycle Regulators in the First Trimester of Human Pregnancy: New Insights for BRCA1

In the first trimester of pregnancy, placental development involves a wide range of cellular processes. These include trophoblast proliferation, fusion, and differentiation, which are dependent on tight cell cycle control. The intrauterine environment affects placental development, which also includes the trophoblast cell cycle. In this work, we focus on maternal obesity to assess whether an altered intrauterine milieu modulates expression and protein levels of placental cell cycle regulators in early human pregnancy. For this purpose, we use first trimester placental tissue from lean and obese women (gestational week 5+0-11+6, n = 58). Using a PCR panel, a cell cycle protein array, and STRING database analysis, we identify a network of cell cycle regulators increased by maternal obesity in which breast cancer 1 (BRCA1) is a central player. Immunostaining localizes BRCA1 predominantly to the villous and the extravillous cytotrophoblast. Obesity-driven BRCA1 upregulation is not able to be explained by DNA methylation (EPIC array) or by short-term treatment of chorionic villous explants at 2.5% oxygen with tumor necrosis factor α (TNF-α) (50 mg/mL), leptin (100 mg/mL), interleukin 6 (IL-6) (100 mg/mL), or high glucose (25 nM). Oxygen tension rises during the first trimester, but this change in vitro has no effect on BRCA1 (2.5% and 6.5% O2). We conclude that maternal obesity affects placental cell cycle regulation and speculate this may alter placental development.

CRY2 suppresses trophoblast migration and invasion in recurrent spontaneous abortion

Disruption of circadian rhythms is associated with aberrant trophoblast migration and invasion in recurrent spontaneous abortion (RSA). This study aims to explore the functional role and the mechanisms of cryptochrome 2 (CRY2), a fundamental component of the circadian clock, in regulating trophoblast migration and invasion. Human extravillous trophoblast cell line HTR-8/SVneo was used as a cell model. Cell migration and invasion were examined using wound healing assay and Transwell assay, respectively. The mRNA and protein levels were determined using quantitative real-time polymerase chain reaction and western blot, respectively. Luciferase reporter assay and chromatin immunoprecipitation assay were performed to explore the interaction between c-Myc to the brain and muscle ARNT-like protein 1 (BMAL1) promoter. CRY2 was highly expressed in human villous specimens of RSA. Furthermore, CRY2 overexpression impaired migration and invasion in HTR-8/SVneo cells, whereas CRY2 knockdown yielded the opposite results. Mechanistically, c-Myc bound to the BMAL1 promoter and induced BMAL1 transcription, both of which further activated matrix metalloproteinase 2/9 (MMP2/9) and facilitated migration and invasion in HTR-8/SVneo cells. CRY2 inhibited c-Myc-BMAL1 pathway and impaired migration and invasion of HTR-8/SVneo cells. Collectively, these findings demonstrate that CRY2 suppresses trophoblast migration and invasion via inhibiting c-Myc-BMAL1-MMP2/9 pathway.

Traditional and New Routes of Trophoblast Invasion and Their Implications for Pregnancy Diseases

Historically, invasion of placental trophoblasts was thought to be extremely specific, only invading into the connective tissues of the maternal uterus and finally reaching and transforming the uterine spiral arteries. Only recently, identification of new routes of trophoblast invasion into different structures of the maternal uterus has been achieved. Thorough morphological analysis has resulted in the identification of trophoblasts invading into glands, veins, and lymph vessels of the uterine wall. These new routes pave the way for a re-evaluation of trophoblast invasion during normal placental development. Of course, such new routes of trophoblast invasion may well be altered, especially in pregnancy pathologies such as intra-uterine growth restriction, preeclampsia, early and recurrent pregnancy loss, stillbirth, and spontaneous abortion. Maybe one or more of these pregnancy pathologies show alterations in different pathways of trophoblast invasion, and, thus, etiologies may need to be redefined, and new therapies may be developed.