Establishment and differentiation of long-term trophoblast organoid cultures from the human placenta

The human placenta is essential for successful reproduction. There is great variation in the anatomy and development of the placenta in different species, meaning that animal models provide limited information about human placental development and function. Until recently, it has been impossible to isolate trophoblast cells from the human placenta that proliferate in vitro. This has limited our ability to understand pregnancy disorders. Generating an in vitro model that recapitulates the unique features of the human placenta has been challenging. The first in vitro model system of human trophoblast that could be cultured long term and differentiated to syncytiotrophoblast (SCT) and extravillous trophoblast (EVT) was a two-dimensional (2D) culture system of human trophoblast stem cells. Here, we describe a protocol to isolate trophoblast from first-trimester human placentas that can be grown long term in a three-dimensional (3D) organoid culture system. Trophoblast organoids can be established within 2-3 weeks, passaged every 7-10 d, and cultured for over a year. The structural organization of these human trophoblast organoids closely resembles the villous placenta with a layer of cytotrophoblast (VCT) that differentiates into superimposed SCT. Altering the composition of the medium leads to differentiation of the trophoblast organoids into HLA-G+ EVT cells which rapidly migrate and invade through the Matrigel droplet in which they are cultured. Our previous research confirmed that there is similarity between the trophoblast organoids and in vivo placentas in their transcriptomes and ability to produce placental hormones. This organoid culture system provides an experimental model to investigate human placental development and function as well as interactions of trophoblast cells with the local and systemic maternal environment.

Activation of multiple receptors stimulates extracellular vesicle release from trophoblast cells

Reports of the stimulated release of extracellular vesicles (EVs) are few, and the mechanisms incompletely understood. To our knowledge, the possibility that the activation of any one of the multitudes of G-protein-coupled receptors (GPCRs) expressed by a single cell-type might increase EV release has not been explored. Recently, we identified the expression of cholecystokinin (CCK), gastrin, gastrin/cholecystokinin types A and/or B receptors (CCKAR and/or -BR), and the bitter taste receptor, TAS2R14 in the human and mouse placenta. specifically, trophoblast. These GPCR(s) were also expressed in four different human trophoblast cell lines. The current objective was to employ two of these cell lines-JAR choriocarcinoma cells and HTR-8/SVneo cells derived from first-trimester human villous trophoblast-to investigate whether CCK, TAS2R14 agonists, and other GPCR ligands would each augment EV release. EVs were isolated from the cell-culture medium by filtration and ultracentrifugation. The preparations were enriched in small EVs (<200 nm) as determined by syntenin western blot before and after sucrose gradient purification, phycoerythrin (PE)-ADAM10 antibody labeling, and electron microscopy. Activation of TAS2R14, CCKBR, cholinergic muscarinic 1 & 3, and angiotensin II receptors, each increased EV release by 4.91-, 2.79-, 1.87-, and 3.11-fold, respectively (all p < .05 versus vehicle controls), without significantly changing EV diameter. A progressive increase of EV concentration in conditioned medium was observed over 24 hr consistent with the release of preformed EVs and de novo biogenesis. Compared to receptor-mediated stimulation, EV release by the calcium ionophore, A23187, was less robust (1.63-fold, p = .08). Diphenhydramine, a TAS2R14 agonist, enhanced EV release in JAR cells at a concentration 10-fold below that required to increase intracellular calcium. CCK activation of HTR-8/SVneo cells, which did not raise intracellular calcium, increased EV release by 2.06-fold (p < .05). Taken together, these results suggested that other signaling pathways may underlie receptor-stimulated EV release besides, or in addition to, calcium. To our knowledge, the finding that the activation of multiple GPCRs can stimulate EV release from a single cell-type is unprecedented and engenders a novel thesis that each receptor may orchestrate intercellular communication through the release of EVs containing a subset of unique cargo, thus mobilizing a specific integrated physiological response by a network of neighboring and distant cells.

Inspired by the human placenta: a novel 3D bioprinted membrane system to create barrier models

Barrier organ models need a scaffold structure to create a two compartment culture. Technical filter membranes used most often as scaffolds may impact cell behaviour and present a barrier themselves, ultimately limiting transferability of test results. In this work we present an alternative for technical filter membrane systems: a 3D bioprinted biological membrane in 24 well format. The biological membrane, based on extracellular matrix (ECM), is highly permeable and presents a natural 3D environment for cell culture. Inspired by the human placenta we established a coculture of a trophoblast-derived cell line (BeWo b30), together with primary placental fibroblasts within the biological membrane (simulating villous stroma) and primary human placental endothelial cells-representing three cellular components of the human placental villus. All cell types maintained their cell type specific marker expression after two weeks of coculture on the biological membrane. In permeability assays the trophoblast layer developed a barrier on the biological membrane, which was even more pronounced when cocultured with fibroblasts. In this work we present a filter membrane free scaffold, we characterize its properties and assess its suitability for cell culture and barrier models. Further we show a novel placenta inspired model in a complex bioprinted coculture. In the absence of an artificial filter membrane, we demonstrate barrier architecture and functionality.

Keratins are asymmetrically inherited fate determinants in the mammalian embryo

To implant in the uterus, the mammalian embryo first specifies two cell lineages: the pluripotent inner cell mass that forms the fetus, and the outer trophectoderm layer that forms the placenta1. In many organisms, asymmetrically inherited fate determinants drive lineage specification2, but this is not thought to be the case during early mammalian development. Here we show that intermediate filaments assembled by keratins function as asymmetrically inherited fate determinants in the mammalian embryo. Unlike F-actin or microtubules, keratins are the first major components of the cytoskeleton that display prominent cell-to-cell variability, triggered by heterogeneities in the BAF chromatin-remodelling complex. Live-embryo imaging shows that keratins become asymmetrically inherited by outer daughter cells during cell division, where they stabilize the cortex to promote apical polarization and YAP-dependent expression of CDX2, thereby specifying the first trophectoderm cells of the embryo. Together, our data reveal a mechanism by which cell-to-cell heterogeneities that appear before the segregation of the trophectoderm and the inner cell mass influence lineage fate, via differential keratin regulation, and identify an early function for intermediate filaments in development.

Placental Trophoblast-Inspired Lipid Bilayers for Cell-Free Investigation of Molecular Interactions

The placenta plays a key role in regulating the maternal-fetal transport but it is a difficult organ to study due to a lack of existing in vitro models. Lipid bilayers inspired by the placenta can provide a facile new in vitro tool with promise for screening molecular transport across this important organ. Here we developed lipid bilayers that mimic the composition of human placental trophoblast cells at different times during the course of pregnancy. Mass spectrometry identified five major lipid classes (phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin) present at varying concentrations in trophoblasts representative of the first and third trimesters and full-term placenta. We successfully developed supported and suspended lipid bilayers mimicking these trophoblast lipid compositions and then demonstrated the utility of these synthetic placenta models for investigating molecular interactions. Specifically, we investigated the interactions with di(2-ethylhexyl) phthalate (DEHP), a common plasticizer and environmental toxicant, and amphotericin B, a common yet toxic, antifungal therapeutic. Overall, we observed that DEHP adsorbs and potentially embeds itself within all placental lipid bilayers, with varying levels of interaction. For both amphotericin B and a liposomal formulation of amphotericin B, AmBisome, we noted lower levels of permeation in transport studies with bilayers and trophoblast cells compared with DEHP, likely driven by differences in size. AmBisome interacted less with both the supported and suspended placental lipid bilayers in comparison to amphotericin B, suggesting that drug delivery carriers can vary the impact of a pharmaceutical agent on these lipid structures. We found that the apparent permeability observed in suspended bilayers was approximately an order of magnitude less than those observed for trophoblast monolayers, which is typical of lipid bilayers. Ultimately, these placenta mimetic lipid bilayers can serve as a platform for the rapid initial screening of molecular interactions with the maternal-fetal interface to better inform future testing.

Naive Human Embryonic Stem Cells Can Give Rise to Cells with a Trophoblast-like Transcriptome and Methylome

Human embryonic stem cells (hESCs) readily differentiate to somatic or germ lineages but have impaired ability to form extra-embryonic lineages such as placenta or yolk sac. Here, we demonstrate that naive hESCs can be converted into cells that exhibit the cellular and molecular phenotypes of human trophoblast stem cells (hTSCs) derived from human placenta or blastocyst. The resulting "transdifferentiated" hTSCs show reactivation of core placental genes, acquisition of a placenta-like methylome, and the ability to differentiate to extravillous trophoblasts and syncytiotrophoblasts. Modest differences are observed between transdifferentiated and placental hTSCs, most notably in the expression of certain imprinted loci. These results suggest that naive hESCs can differentiate to extra-embryonic lineage and demonstrate a new way of modeling human trophoblast specification and placental methylome establishment.

Delta-9-tetrahydrocannabinol disrupts mitochondrial function and attenuates syncytialization in human placental BeWo cells

The psychoactive component in cannabis, delta-9-tetrahydrocannabinol, can restrict fetal growth and development. Delta-9-tetrahydrocannabinol has been shown to negatively impact cellular proliferation and target organelles like the mitochondria resulting in reduced cellular respiration. In the placenta, mitochondrial dysfunction leading to oxidative stress prevents proper placental development and function. A key element of placental development is the proliferation and fusion of cytotrophoblasts to form the syncytium that comprises the materno-fetal interface. The impact of delta-9-tetrahydrocannabinol on this process is not well understood. To elucidate the nature of the mitochondrial dysfunction and its consequences on trophoblast fusion, we treated undifferentiated and differentiated BeWo human trophoblast cells, with 20 µM delta-9-tetrahydrocannabinol for 48 hr. At this concentration, delta-9-tetrahydrocannabinol on BeWo cells reduced the expression of markers involved in syncytialization and mitochondrial dynamics, but had no effect on cell viability. Delta-9-tetrahydrocannabinol significantly attenuated the process of syncytialization and induced oxidative stress responses in BeWo cells. Importantly, delta-9-tetrahydrocannabinol also caused a reduction in the secretion of human chorionic gonadotropin and the production of human placental lactogen and insulin growth factor 2, three hormones known to be important in facilitating fetal growth. Furthermore, we also demonstrate that delta-9-tetrahydrocannabinol attenuated mitochondrial respiration, depleted adenosine triphosphate, and reduced mitochondrial membrane potential. These changes were also associated with an increase in cellular reactive oxygen species, and the expression of stress responsive chaperones, HSP60 and HSP70. These findings have important implications for understanding the role of delta-9-tetrahydrocannabinol-induced mitochondrial injury and the role this might play in compromising human pregnancies.

Modeling human trophoblast, the placental epithelium at the maternal fetal interface

Appropriate human trophoblast lineage specification and differentiation is crucial for the establishment of normal placentation and maintenance of pregnancy. However, due to the lack of proper modeling systems, the molecular mechanisms of these processes are still largely unknown. Much of the early studies in this area have been based on animal models and tumor-derived trophoblast cell lines, both of which are suboptimal for modeling this unique human organ. Recent advances in regenerative and stem cell biology methods have led to development of novel in vitro model systems for studying human trophoblast. These include derivation of human embryonic and induced pluripotent stem cells and establishment of methods for the differentiation of these cells into trophoblast, as well as the more recent derivation of human trophoblast stem cells. In addition, advances in culture conditions, from traditional two-dimensional monolayer culture to 3D culturing systems, have led to development of trophoblast organoid and placenta-on-a-chip model, enabling us to study human trophoblast function in context of more physiologically accurate environment. In this review, we will discuss these various model systems, with a focus on human trophoblast, and their ability to help elucidate the key mechanisms underlying placental development and function. This review focuses on model systems of human trophoblast differentiation, including advantages and limitations of stem cell-based culture, trophoblast organoid, and organ-on-a-chip methods and their applications in understanding placental development and disease.

Atypical protein kinase C iota (PKCλ/ι) ensures mammalian development by establishing the maternal-fetal exchange interface

In utero mammalian development relies on the establishment of the maternal-fetal exchange interface, which ensures transportation of nutrients and gases between the mother and the fetus. This exchange interface is established via development of multinucleated syncytiotrophoblast cells (SynTs) during placentation. In mice, SynTs develop via differentiation of the trophoblast stem cell-like progenitor cells (TSPCs) of the placenta primordium, and in humans, SynTs are developed via differentiation of villous cytotrophoblast (CTB) progenitors. Despite the critical need in pregnancy progression, conserved signaling mechanisms that ensure SynT development are poorly understood. Herein, we show that atypical protein kinase C iota (PKCλ/ι) plays an essential role in establishing the SynT differentiation program in trophoblast progenitors. Loss of PKCλ/ι in the mouse TSPCs abrogates SynT development, leading to embryonic death at approximately embryonic day 9.0 (E9.0). We also show that PKCλ/ι-mediated priming of trophoblast progenitors for SynT differentiation is a conserved event during human placentation. PKCλ/ι is selectively expressed in the first-trimester CTBs of a developing human placenta. Furthermore, loss of PKCλ/ι in CTB-derived human trophoblast stem cells (human TSCs) impairs their SynT differentiation potential both in vitro and after transplantation in immunocompromised mice. Our mechanistic analyses indicate that PKCλ/ι signaling maintains expression of GCM1, GATA2, and PPARγ, which are key transcription factors to instigate SynT differentiation programs in both mouse and human trophoblast progenitors. Our study uncovers a conserved molecular mechanism, in which PKCλ/ι signaling regulates establishment of the maternal-fetal exchange surface by promoting trophoblast progenitor-to-SynT transition during placentation.

Investigation of human trophoblast invasion in vitro

BACKGROUND

In humans, inadequate trophoblast invasion into the decidua is associated with the 'great obstetrical syndromes' which include pre-eclampsia, foetal growth restriction (FGR) and stillbirth. The mechanisms regulating invasion remain poorly understood, although interactions with the uterine environment are clearly of central importance. Extravillous trophoblast (EVT) cells invade the uterus and transform the spiral arteries. Progress in understanding how they invade has been limited due to the lack of good in vitro models. Firstly, there are no non-malignant cell lines that have an EVT phenotype. Secondly, the invasion assays used are of limited use for the small numbers of primary EVT available from first-trimester placentas. We discuss recent progress in this field with the generation of new EVT lines and invasion assays using microfluidic technology.

OBJECTIVE AND RATIONALE

Our aim is to describe the established models used to study human trophoblast invasion in vivo and in vitro. The difficulties of obtaining primary cells and cell lines that recapitulate the phenotype of EVT are discussed together with the advantages and pitfalls of the different invasion assays. We compare these traditional end point assays to microfluidic assays where the dynamics of migration can be measured.

SEARCH METHODS

Relevant studies were identified by PubMed search, last updated on February 2020. A search was conducted to determine the number of journal articles published using the cell lines JEG-3, BeWo, JAR, HTR-8/Svneo, Swan-71 and primary human extravillous trophoblast in the last 5 years.

OUTCOMES

Deep trophoblast invasion into the maternal decidua is a particular feature of human pregnancy. This invasion needs to be finely regulated to allocate resources between mother and baby. A reliable source of EVT is needed to study in vitro how the uterine environment regulates this process. First, we critically discuss the issues with the trophoblast cell lines currently used; for example, most of them lack expression of the defining marker of EVT, HLA-G. Recently, advances in human stem cell and organoid technology have been applied to extraembryonic tissues to develop trophoblast cell lines that can grow in two (2D) and three dimensions (3D) and differentiate to EVT. This means that the 'trophoblast' cell lines currently in use should rapidly become obsolete. Second, we critically discuss the problems with assays to study trophoblast invasion. These lack physiological relevance and have simplified migration dynamics. Microfluidic assays are a powerful tool to study cell invasion because they require only a few cells, which are embedded in 3D in an extracellular matrix. Their major advantage is real-time monitoring of cell movement, enabling detailed analysis of the dynamics of trophoblast migration.

WIDER IMPLICATIONS

Trophoblast invasion in the first trimester of pregnancy remains poorly understood despite the importance of this process in the pathogenesis of pre-eclampsia, FGR, stillbirth and recurrent miscarriage. The new technologies described here will allow investigation into this critical process.

Circ_0085296 suppresses trophoblast cell proliferation, invasion, and migration via modulating miR-144/E-cadherin axis

BACKGROUND

Circular RNAs (circRNAs) have been revealed to be important regulators in the biological behavior of cells, and aberrant circRNAs may be associated with the etiology of pre-eclampsia (PE). However, the role and underlying molecular mechanisms of circ_0085296 in PE remain unclear.

METHODS

The expression of circ_0085296, microRNA (miR)-144, and E-cadherin was detected using quantitative real-time polymerase chain reaction and western blot, respectively. Cell proliferation, migration, and invasion were analyzed by cell counting kit-8, colony formation and transwell assay. The interaction between miR-144 and circ_0085296 or E-cadherin was analyzed by the dual-luciferase reporter assay and pull-down assay.

RESULTS

Circ_0085296 was elevated in PE placental tissues, knockdown of circ_0085296 promoted trophoblast cell proliferation, invasion, and migration, while circ_0085296 up-regulation showed opposite effects. MiR-144 was down-regulated in PE placental tissues, and restoration of miR-144 induced proliferation, invasion, and migration in trophoblast cells. Further mechanistic analysis found miR-144 directly bound to circ_0085296 and E-cadherin, and circ_0085296 functioned as a sponge of miR-144 to regulate E-cadherin expression. Furthermore, miR-144 inhibition or E-cadherin overexpression attenuated the effectsof circ_0085296 on cell processes in trophoblast cells.

CONCLUSION

Circ_0085296 inhibited trophoblast cell proliferation, invasion, and migration via regulating miR-144/E-cadherin axis, providing a novel insight into the pathogenesis of PE and a new prospective therapeutic target for PE patients.

TET1 and 5-Hydroxymethylation Preserve the Stem Cell State of Mouse Trophoblast

The ten-eleven translocation factor TET1 and its conferred epigenetic modification 5-hydroxymethylcytosine (5hmC) have important roles in maintaining the pluripotent state of embryonic stem cells (ESCs). We previously showed that TET1 is also essential to maintain the stem cell state of trophoblast stem cells (TSCs). Here, we establish an integrated panel of absolute 5hmC levels, genome-wide DNA methylation and hydroxymethylation patterns, transcriptomes, and TET1 chromatin occupancy in TSCs and differentiated trophoblast cells. We show that the combined presence of 5-methylcytosine (5mC) and 5hmC correlates with transcriptional activity of associated genes. Hypoxia can slow down the global loss of 5hmC that occurs upon differentiation of TSCs. Notably, unlike in ESCs and epiblast cells, most TET1-bound regions overlap with active chromatin marks and TFAP2C binding sites and demarcate putative trophoblast enhancer regions. These chromatin modification and occupancy patterns are highly informative to identify novel candidate regulators of the TSC state.

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5hmC to 5mC ratios correlate with gene activity in TS cells

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TS cell differentiation-associated loss of 5hmC is slowed down in hypoxia

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TET1 binding in TS cells forms long-range interactions with key trophoblast genes

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Intergenic TET1 binding sites in TS cells demarcate putative trophoblast enhancers

Autophagy suppression of trophoblast cells induces pregnancy loss by activating decidual NK cytotoxicity and inhibiting trophoblast invasion

BACKGROUND

The crosstalk between trophoblast cells and decidual NK cells plays an important role in the establishment and maintenance of normal pregnancy. Recent studies reported that autophagy can induce immune tolerance at the maternal fetal interface, while the mechanism remains unclear.

METHODS

Autophagy levels in the villi of normal and recurrent spontaneous abortion (RSA) patients were detected by transmission electron microscopy. After co-cultured with trophoblast cells pretreated with 3-MA or rapamycin, NK cells were collected and the expression of killer receptors was detected by flow cytometry (FCM). The invasiveness of trophoblasts was tested by Cell invasion assay.

RESULTS

Compared with elective pregnancy termination patients, the level of autophagy in the villi of RSA patients was significantly decreased. Inducing the autophagy level in trophoblast cells with rapamycin could significantly inhibit the cytotoxicity of NK cells in the co-culture system, and supplement of IGF-2 could rectify this effect. Meanwhile, autophagy suppression of trophoblasts reduced the level of Paternally Expressed Gene 10 (PEG10), leading to the impairment of trophoblast cell invasion. In addition, NK cells educated by autophagy-inhibited trophoblasts further decreased the proliferation and invasiveness of trophoblasts. In pregnant mice model, injection with 3-MA promoted the cytotoxicity of uterine NK cells, and increased the embryo absorption rate.

CONCLUSION

Autophagy suppression of trophoblasts increase the cytotoxicity of NK cells and damage the trophoblasts invasion possibly by targeting IGF-2 and PEG10, respectively, which ultimately leads to miscarriage. Video Abstarct.

Annexin A1/Formyl Peptide Receptor Pathway Controls Uterine Receptivity to the Blastocyst

Embryo implantation into the uterine wall is a highly modulated, complex process. We previously demonstrated that Annexin A1 (AnxA1), which is a protein secreted by epithelial and inflammatory cells in the uterine microenvironment, controls embryo implantation in vivo. Here, we decipher the effects of recombinant AnxA1 in this phenomenon by using human trophoblast cell (BeWo) spheroids and uterine epithelial cells (Ishikawa; IK). AnxA1-treated IK cells demonstrated greater levels of spheroid adherence and upregulation of the tight junction molecules claudin-1 and zona occludens-1, as well as the glycoprotein mucin-1 (Muc-1). The latter effect of AnxA1 was not mediated through IL-6 secreted from IK cells, a known inducer of Muc-1 expression. Rather, these effects of AnxA1 involved activation of the formyl peptide receptors FPR1 and FPR2, as pharmacological blockade of FPR1 or FPR1/FPR2 abrogated such responses. The downstream actions of AnxA1 were mediated through the ERK1/2 phosphorylation pathway and F-actin polymerization in IK cells, as blockade of ERK1/2 phosphorylation reversed AnxA1-induced Muc-1 and claudin-1 expression. Moreover, FPR2 activation by AnxA1 induced vascular endothelial growth factor (VEGF) secretion by IK cells, and the supernatant of AnxA1-treated IK cells evoked angiogenesis in vitro. In conclusion, these data highlight the role of the AnxA1/FPR1/FPR2 pathway in uterine epithelial control of blastocyst implantation.

Placentation and hormonal maintenance of pregnancy in the impala (Aepyceros melampus)

INTRODUCTION

The impala is a widely distributed African ungulate. Detailed studies of the placenta and ovaries in impala undertaken in the 1970s did not address the endocrine functions of the placenta.

METHODS

The uteri of 25 pregnant impala estimated to be between 49 and 113 days of the 190 day gestation were examined grossly, histologically and immunohistochemically.

RESULTS

A single corpus luteum was present in either maternal ovary but the conceptus was always situated in the right uterine horn. The fetal membranes extended to the tips of both uterine horns. The amnion was in intimate contact with, but not fused to, the allantochorion. Placentation was typically ruminant with fetal macrocotyledons attached to the rows of maternal caruncles. The fetal villi were highly branched, especially in the centre of each placentome where the attenuated maternal epithelium lining the placental crypts was absent in some places. Both the corpus luteum and the uninucleate trophoblast cells of the interplacentomal allantochorion stained strongly for 3-β hydroxysteroid dehydrogenase, and progestagen concentrations in allantoic and amniotic fluids increased significantly as gestation progressed, with a tendency to do likewise in maternal serum. Binucleate trophoblast cells stained positively for bovine placental lactogen, but neither the placenta nor the maternal corpus luteum showed evidence of oestrogen synthesis.

DISCUSSION

Despite exhibiting the same basic type of placentation, both the gross and histological structure of the impala placenta, along with its immunohistochemical properties, demonstrates that great variation exists across ruminant placentas.

Deletion of atypical chemokine receptor 3 (ACKR3) increases immune cells at the fetal-maternal interface

Establishment of immune cell populations and adaptations in immune cells are critical aspects during pregnancy that lead to protection of the semi-allogenic fetus. Appropriate immune cell activation and trophoblast migration are regulated in part by chemokines, the availability of which can be fine-tuned by decoy receptors. Atypical chemokine receptor 3 (ACKR3), previously named C-X-C chemokine receptor 7 (CXCR7), is a chemokine decoy receptor expressed in placenta, but little is known about how this receptor affects placental development. In this study, we investigated the phenotypic characteristics of placentas from Ackr3^-/- embryos to determine how Ackr3 contributes to early placentation. In placentas from Ackr3^-/- embryos, we observed an increase in decidual compaction and in the size of the uterine natural killer cell population. Ackr3 knockdown in trophoblast cells led to a decrease in trophoblast migration. These findings suggest that this decoy receptor may therefore be an important factor in normal placentation.

The Transcription Factor OVOL2 Represses ID2 and Drives Differentiation of Trophoblast Stem Cells and Placental Development in Mice

Trophoblasts are the first cell type to be specified during embryogenesis, and they are essential for placental morphogenesis and function. Trophoblast stem (TS) cells are the progenitor cells for all trophoblast lineages; control of TS cell differentiation into distinct trophoblast subtypes is not well understood. Mice lacking the transcription factor OVO-like 2 (OVOL2) fail to produce a functioning placenta, and die around embryonic day 10.5, suggesting that OVOL2 may be critical for trophoblast development. Therefore, our objective was to determine the role of OVOL2 in mouse TS cell fate. We found that OVOL2 was highly expressed in mouse placenta and differentiating TS cells. Placentas and TS cells lacking OVOL2 showed poor trophoblast differentiation potential, including increased expression of stem-state associated genes (Eomes, Esrrb, Id2) and decreased levels of differentiation-associated transcripts (Gcm1, Tpbpa, Prl3b1, Syna). Ectopic OVOL2 expression in TS cells elicited precocious differentiation. OVOL2 bound proximate to the gene encoding inhibitor of differentiation 2 (ID2), a dominant negative helix-loop-helix protein, and directly repressed its activity. Overexpression of ID2 was sufficient to reinforce the TS cell stem state. Our findings reveal a critical role of OVOL2 as a regulator of TS cell differentiation and placental development, in-part by coordinating repression of ID2.

High-purity isolation of rare single cells from blood using a tiered microchip system

We present a two-tiered microchip system to capture and retrieve rare cells from blood samples with high purity. The first module of the system is a high throughput microfluidic interface that is used to immunomagnetically isolate targeted rare cells from whole blood, and discard > 99.999% of the unwanted leukocytes. The second module is a microwell array that furthers the purification by magnetically guiding each cell into a separate well concurrently, and allows individual retrieval of each cell. We demonstrate the design of the system as well as its characterization by experiments using model cell lines that represent circulating fetal trophoblasts. Our results show that single cells can be retrieved with efficiencies and purities as high as 100% within 145 mins.

Silencing DAPK3 blocks the autophagosome-lysosome fusion by mediating SNAP29 in trophoblast cells under high glucose treatment

Autophagy plays an essential role in gestational diabetes mellitus (GDM). Death-associated protein kinase-3 (DAPK3) regulates a variety of cellular functions; however, the relationship between DAPK3 and autophagy is unknown. In this study, we aim to investigate whether DAPK3 is associated with autophagy in GDM, and we found that DAPK3 was upregulated in the placenta of GDM patients and extravillous trophoblast cells under high-glucose conditions. Silencing DAPK3 decreased the assembly of the STX17-SNAP29-VAMP8 complex, leading to the blockade of autophagosome-lysosome fusion by mediating synaptosomal-associated protein 29 (SNAP29). Moreover, knockdown of DAPK3 ameliorates cell invasion and mediates autophagy in high glucose, and does not alter the expression of autophagy-related genes in normal glucose. Our study demonstrates the significance of DAPK3 in autophagy and GDM, which may provide new insights into the molecular mechanisms regulating trophoblast invasion.

Derivation of trophoblast stem cells from naïve human pluripotent stem cells

Naïve human pluripotent stem cells (hPSCs) provide a unique experimental platform of cell fate decisions during pre-implantation development, but their lineage potential remains incompletely characterized. As naïve hPSCs share transcriptional and epigenomic signatures with trophoblast cells, it has been proposed that the naïve state may have enhanced predisposition for differentiation along this extraembryonic lineage. Here we examined the trophoblast potential of isogenic naïve and primed hPSCs. We found that naïve hPSCs can directly give rise to human trophoblast stem cells (hTSCs) and undergo further differentiation into both extravillous and syncytiotrophoblast. In contrast, primed hPSCs do not support hTSC derivation, but give rise to non-self-renewing cytotrophoblasts in response to BMP4. Global transcriptome and chromatin accessibility analyses indicate that hTSCs derived from naïve hPSCs are similar to blastocyst-derived hTSCs and acquire features of post-implantation trophectoderm. The derivation of hTSCs from naïve hPSCs will enable elucidation of early mechanisms that govern normal human trophoblast development and associated pathologies.

Pinopodes: Recent advancements, current perspectives, and future directions

Successful embryo implantation is a complex and highly regulated process involving precise synchronization between the fetal-derived trophoblast cells and maternal uterine luminal epithelium. Multiple endocrine-driven factors are important for controlling the timely receptivity of the uterus, and this complexity underscores implantation failure as a major cause of recurrent infertility associated with assisted reproductive technologies. One particular cellular structure often hypothesized to promote receptivity is the pinopode or uterodome - a hormonally regulated, large cellular protrusion on the uterine epithelial surface. Recent clinical studies associate pinopodes with favorable fertility outcomes in women, and because they are directly linked to an increase in progesterone levels, the potential utility of these hormone-regulated cell biological structures in predicting or improving implantation in a clinical setting holds promise. In this review, we aim to generate interest in pinopodes from the broader cell biology and endocrinology communities, re-examine methodologies in pinopode research, and identify priorities for future investigation of pinopode structure and function in women's reproductive health.

Function of CCL5 in maternal-fetal interface of pig during early pregnancy

Chemokines refer to chemoattractant cytokines, which have crucial functions in inflammation and immune responses in multiple cellular processes. In the present study, we described the potential role of porcine CCL5 in embryo implantation and fetal-maternal environment during early pregnancy. We first carried out phylogenetic analysis of porcine CCL5, and analyzed the cell specific localization of CCL5 and its receptor CCR3 in a kinetic approach within porcine estrous cycles and early gestation stage. In addition, CCL5 stimulated porcine uterine luminal epithelial (pLE) and porcine trophectoderm (pTr) cell proliferations, and cell cycle progressions via AKT and MAPK intracellular signaling tractions. Furthermore, CCL5 attenuated tunicamycin-induced endoplasmic reticulum (ER) stress signaling, and lipopolysaccharides-triggered inflammatory responses in pLE and pTr cells. Taken together, our study showed that CCL5 is involved in the placental development or promotes the placental development.

Aspirin modulates STOX1 expression and reverses STOX1-induced insufficient proliferation and migration of trophoblast cells

BACKGROUND

A major cause of preeclampsia is the placental ischemia caused by insufficient trophoblast cells, invading into the spiral artery. Storkhead-box protein 1 (STOX1) is highly associated with preeclampsia. Meanwhile, low-dose aspirin for patients with preeclampsia is effective in reducing the incidence of preeclampsia. The aim of the present study was to explore the underlying mechanism, and the relationship between STOX1 and aspirin in preeclampsia.

METHODS

The human choriocarcinoma cell line JEG-3 was employed to mimic trophoblast cells and establish a model for trophoblast cells overexpressing STOX1 and knockdown of JEG cell lines, which were treated with aspirin afterwards. Cell counting kit-8 (CCK-8) assay was utilized to estimate cell proliferation and optimal concentration of aspirin for further experiments. Meanwhile, transwell assay was used to detect migration, and flow cytometry was used to measure apoptosis. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blotting were applied to analyze the expression levels of STOX1 and related genes.

RESULTS

Overexpression of STOX1 inhibited proliferation of JEG-3 cells through epidermal growth factor (EGF), vascular EGF (VEGF), and transforming growth factor beta 1 (TGF-β1) proteins, while suppressed migration through MMP2, MMP9, and E-cadherin proteins. In contrast, apoptosis of JEG-3 cells was elevated by STOX1 through Bcl-2, Bax, and Cox-2 proteins. Furthermore, we found that aspirin modulated the expression level of STOX1 and reversed proliferation and migration of STOX1-induced insufficient trophoblast cells.

CONCLUSION

The present study suggested that inhibition of the expression of STOX1 could promote the effects of aspirin in the treatment of preeclampsia.

Trophoblast cell differentiation in the bovine placenta: differentially expressed genes between uninucleate trophoblast cells and trophoblast giant cells are involved in the composition and remodeling of the extracellular matrix and O-glycan biosynthesis

BACKGROUND

In the bovine placenta, intimate fetomaternal contacts are restricted to discrete placentomes. Here, widely branched fetal chorionic villi interdigitate with corresponding maternal caruncular crypts. The fetal trophoblast epithelium covering the chorionic villi consists of approximately 80% uninucleate trophoblast cells (UTCs) and 20% binuclear trophoblast giant cells (TGCs). The weakly invasive TGCs migrate toward the caruncle epithelium and eventually fuse with individual epithelial cells to form short-lived fetomaternal hybrid cells. In this way, molecules of fetal origin are transported across the placental barrier and released into the maternal compartment. The UTC/TGC ratio in the trophoblast remains almost constant because approximately as many new TGCs are produced from UTCs as are consumed by the fusions. The process of developing TGCs from UTCs was insufficiently understood. Therefore, we aimed to detect differentially expressed genes (DEGs) between UTCs and TGCs and identify molecular functions and biological processes regulated by DEGs.

RESULTS

We analyzed gene expression patterns in virtually pure UTC and TGC isolates using gene arrays and detected 3193 DEGs (p < 0.05; fold change values < - 1.5 or > 1.5). Of these DEGs, 1711 (53.6%) were upregulated in TGCs and 1482 (46.4%) downregulated. Gene Ontology (GO) analyses revealed that molecular functions and biological processes regulated by DEGs are related to the extracellular matrix (ECM) and its interactions with cellular receptors, cell migration and signal transduction. Furthermore, there was some evidence that O-glycan biosynthesis in TGCs may produce sialylated short-chain O-glycans (Tn antigen, core 1 O-glycans), while the synthesis of other O-glycan core structures required for the formation of complex (i.e., branched and long-chain) O-glycans appears to be decreased in TGCs.

CONCLUSION

The differentiation of UTCs into TGCs particularly regulates genes that enable trophoblast cells to interact with their environment. Significant differences between UTCs and TGCs in ECM composition indicate reduced anchoring of TGCs in the surrounding matrix, which might contribute to their migration and their weakly invasive interaction with the maternal endometrium. Furthermore, increased expression of sialylated short chain O-glycans by TGCs could facilitate the modulation of maternal immune tolerance.

Complex patterns of cell growth in the placenta in normal pregnancy and as adaptations to maternal diet restriction

The major milestones in mouse placental development are well described, but our understanding is limited to how the placenta can adapt to damage or changes in the environment. By using stereology and expression of cell cycle markers, we found that the placenta grows under normal conditions not just by hyperplasia of trophoblast cells but also through extensive polyploidy and cell hypertrophy. In response to feeding a low protein diet to mothers prior to and during pregnancy, to mimic chronic malnutrition, we found that this normal program was altered and that it was influenced by the sex of the conceptus. Male fetuses showed intrauterine growth restriction (IUGR) by embryonic day (E) 18.5, just before term, whereas female fetuses showed IUGR as early as E16.5. This difference was correlated with differences in the size of the labyrinth layer of the placenta, the site of nutrient and gas exchange. Functional changes were implied based on up-regulation of nutrient transporter genes. The junctional zone was also affected, with a reduction in both glycogen trophoblast and spongiotrophoblast cells. These changes were associated with increased expression of Phlda2 and reduced expression of Egfr. Polyploidy, which results from endoreduplication, is a normal feature of trophoblast giant cells (TGC) but also spongiotrophoblast cells. Ploidy was increased in sinusoidal-TGCs and spongiotrophoblast cells, but not parietal-TGCs, in low protein placentas. These results indicate that the placenta undergoes a range of changes in development and function in response to poor maternal diet, many of which we interpret are aimed at mitigating the impacts on fetal and maternal health.