Human placenta and trophoblast development: key molecular mechanisms and model systems

Assessment of serum levels and placental bed tissue expression of IGF-1, bFGF, and PLGF in patients with placenta previa complicated with placenta accreta spectrum disorders

OBJECTIVE

This study aims to detect the serum levels of IGF-1, bFGF, and PLGF and their expressions in placental bed tissues of patients with placenta previa complicated with PAS disorders.

METHODS

This case and control study included 40 multiparous pregnant women with complete placenta previa between 34 weeks and 38 weeks of gestation and they were divided into two groups: 25 patients with PAS (case group) and 15 patients without PAS (control group). The venous blood samples were collected 2 h before the cesarean section, and the placental bed tissues were taken intraoperatively at the placental implantation site and then were histologically examined to evaluate the gravity of the myometrial invasion of the placenta. According to FIGO PAS increasing grading, the 25 patients were also divided into three groups: PAS grade I group, PAS grade II group, and PAS grade III group. The concentrations of IGF-1, bFGF, and PLGF in serum were measured using ELISA, and the mean ratio of the relative mRNA expression of each biomarker in placental bed tissues was calculated using qRT-PCR. The staining intensity and the positive cells were quantitatively measured and expressed as means by using Image J software for IHC analysis.

RESULTS

IGF-1 had low serum levels and high placental bed expression in placenta previa patients with PAS disorders compared to those without PAS (all p < 0.0001). PLGF had high serum levels (p = 0.0200) and high placental bed expression (p < 0.0001) in placenta previa patients with PAS disorders compared to those without PAS. IGF-1 serum levels decreased up to PAS grade II (means were 24.3 ± 4.03, 21.98 ± 3.29, and 22.03 ± 7.31, respectively for PAS grade I, PAS grade II, PAS grade III groups, p = 0.0006). PLGF serum levels increased up to PAS grade II (means were 12.96 ± 2.74, 14.97 ± 2.56, and 14.89 ± 2.14, respectively for the three groups, p = 0.0392). However, IGF-1 and PLGF mRNA placental bed expression increased up to PAS grade III. The relative expression of mRNA means for the three groups was 3.194 ± 1.40, 3.509 ± 0.63, and 3.872 ± 0.70, respectively for IGF-1; and 2.784 ± 1.14, 2.810 ± 0.71, and 2.869 ± 0.48, respectively for PLGF (all p < 0.0001). Their IHC (immunohistochemical) staining also had increasing trends, but p > 0.05. bFGF was not significantly expressed in placenta previa with PAS disorders in most of the analysis sections (p > 0.05).

CONCLUSIONS

Low serum levels and high expression in placental bed tissues of IGF-1, or high serum levels and high expression in placental bed tissues of PLGF, may differentiate placenta previa patients with FIGO PAS grade I and PAS grade II from those without PAS disorders. However, they could not significantly predict the degree of placental invasiveness in FIGO PAS grades II and III.

Is there a relationship between morphokinetic parameters and obstetrical complications? An analysis of singleton live births after single fresh embryo transfer

BACKGROUND

With the advancement in embryology and the introduction of time-lapse monitoring system, the embryologists' goal might be to find not only the embryo with the highest probability of live birth, but also the embryo with the highest probability to progress to a healthy full-term delivery. Thus, we aimed to investigate the association between morphokinetic time-lapse parameters and obstetrical and perinatal complications.

METHODS

A cohort study reviewing fertility and delivery files of all singletone births from IVF patients whose embryos were cultured in a time-lapse monitoring system and had a single fresh embryo transfer at our center between 2013-2019. We conducted multiple comparisons between complicated and uncomplicated pregnancies of each perinatal complication, including: gestational diabetes mellitus (GDM); small for gestational age (SGA); pre-eclamptic toxemia (PET); preterm labor < 37 weeks of gestation (PTL); and third stage of labor complications. A comparison between pregnancies with and without a composite outcome of placental complications including GDM, SGA, PET and PTL was also conducted. Baseline characteristics, treatment and morphokinetic parameters in complicated and uncomplicated gestations were compared. Logistic regression analysis was utilized to adjust results for potential confounders.

RESULTS

One hundred seventy-six single embryo transfers resulted in 176 live births. Morphokinetic time-lapse parameters were similar between the groups, except for a shorter time to full blastulation in the SGA group (tB-tPNf = 75.5 ± 1.3 h vs. 79.5 ± 4.8 in the non-SGA group, p < 0.001), and shorter third cell cycle duration in the PET group (CC3 = 12.4 ± 1.1 h vs. 13.6 ± 2.9 in the non-PET group, p = 0.02). On multivariate regression analysis, none of the morphokinetic parameters were found to be significantly correlated with any of the perinatal complications.

CONCLUSION

Time-lapse morphokinetic parameters of the embryo transferred are not associated with adverse obstetric and perinatal outcomes.

Marmoset and human trophoblast stem cells differ in signaling requirements and recapitulate divergent modes of trophoblast invasion

Early human trophoblast development has remained elusive due to the inaccessibility of the early conceptus. Non-human primate models recapitulate many features of human development and allow access to early postimplantation stages. Here, we tracked the pre- to postimplantation transition of the trophoblast lineage in superficially implanting marmoset embryos in vivo. We differentiated marmoset naive pluripotent stem cells into trophoblast stem cells (TSCs), which exhibited trophoblast-specific transcriptome, methylome, differentiation potential, and long-term self-renewal. Notably, human TSC culture conditions failed to support marmoset TSC derivation, instead inducing an extraembryonic mesoderm-like fate in marmoset cells. We show that combined MEK, TGF-β/NODAL, and histone deacetylase inhibition stabilizes a periimplantation trophoblast-like identity in marmoset TSCs. By contrast, these conditions differentiated human TSCs toward extravillous trophoblasts. Our work presents a paradigm to harness the evolutionary divergence in implantation strategies to elucidate human trophoblast development and invasion.

JPT2 in subclinical hypothyroidism-related miscarriage as a transcription co-factor: involvement of LEPR/STAT3 activation

BACKGROUND AND PURPOSE

Subclinical hypothyroidism (SCH) has been identified to be associated with implantation failure, in which the dysfunction of trophoblast cells is involved. In this study, the transcriptomics of aborted placenta from SCH rats were analyzed. Jupiter microtubule-associated homolog 2 (JPT2) was downregulated in the aborted placenta. This study aims to investigate its role in SCH-associated miscarriage.

METHODS

Spontaneous abortion was observed in SCH rats generated by thyroidectomy combined with levothyroxine administration. The transcriptomics analysis was performed using aborted placenta. Afterward, the effects of JPT2 on trophoblast cells were explored using gain-and loss-of-function experiments.

RESULTS

Transcriptomics analysis showed 1286 downregulated genes and 2300 upregulated genes in the aborted placenta, and JPT2 was significantly downregulated in the aborted placenta from SCH rats. Afterward, gain-and loss-of-function experiments exhibited that overexpression of JPT2 promoted the proliferation, migration, invasion, spheroid formation of HTR-8/SVneo trophoblast cells and their attachment to endometrial stromal cells, while these biological behaviors were suppressed by JPT2 knockdown. Furthermore, JPT2 accelerated the transcription of leptin receptor (LEPR), and activated signal transducer and activator of transcription 3 (STAT3) signal in a transcription factor AP-2γ-dependent manner. In addition, silencing of LEPR abolished the role of JPT2.

CONCLUSION

Our results revealed that JPT2, which was downregulated in the aborted placenta from SCH rats, promoted proliferation, migration, invasion, spheroid formation, and attachment of trophoblast cells via regulating LEPR/STAT3 axis as a transcription co-factor. It is indicated that low expression of JPT2 may contribute to the abortion in individuals with SCH.

NOTUM-mediated WNT silencing drives extravillous trophoblast cell lineage development

Trophoblast stem (TS) cells have the unique capacity to differentiate into specialized cell types, including extravillous trophoblast (EVT) cells. EVT cells invade into and transform the uterus where they act to remodel the vasculature facilitating the redirection of maternal nutrients to the developing fetus. Disruptions in EVT cell development and function are at the core of pregnancy-related disease. WNT-activated signal transduction is a conserved regulator of morphogenesis of many organ systems, including the placenta. In human TS cells, activation of canonical WNT signaling is critical for maintenance of the TS cell stem state and its downregulation accompanies EVT cell differentiation. We show that aberrant WNT signaling undermines EVT cell differentiation. Notum, palmitoleoyl-protein carboxylesterase (NOTUM), a negative regulator of canonical WNT signaling, was prominently expressed in first-trimester EVT cells developing in situ and up-regulated in EVT cells derived from human TS cells. Furthermore, NOTUM was required for optimal human TS cell differentiation to EVT cells. Activation of NOTUM in EVT cells is driven, at least in part, by endothelial Per-Arnt-Sim (PAS) domain 1 (also called hypoxia-inducible factor 2 alpha). Collectively, our findings indicate that canonical Wingless-related integration site (WNT) signaling is essential for maintenance of human trophoblast cell stemness and regulation of human TS cell differentiation. Downregulation of canonical WNT signaling via the actions of NOTUM is required for optimal EVT cell differentiation.

Circ_0015382 Regulates the miR-942-5p/NDRG1 Axis to Suppress Trophoblast Cell Functions

Circular RNAs (circRNAs) are non-coding RNAs that exert vital function in many human diseases, including preeclampsia (PE). Circ_0015382 is considered to be a key regulator of PE progression, so more molecular mechanisms need to be further studied. Real-time quantitative PCR was used to detect the mRNA levels of circ_0015382, miR-942-5p, and N-myc downstream regulated 1 (NDRG1). Western blot analysis was conducted to assess the protein levels. MTT and EdU assays were used to assess cell proliferation. Cell invasion was analyzed by transwell assay. Tube formation assay was conducted to detect cell angiogenesis. Dual-luciferase reporter assay and RNA immunoprecipitation were used to analyze the target relationship between miR-942-5p and circ_0015382 or NDRG1. Our data showed that circ_0015382 and NDRG1 were up-regulated, while miR-942-5p was down-regulated in the placental tissues of PE patients. Trophoblast cell proliferation, invasion, and angiogenesis were promoted by knockdown of circ_0015382. Circ_0015382 could sponge miR-942-5p, and NDRG1 was a target of miR-942-5p. MiR-942-5p inhibitor could reverse the promoting effects of si-circ_0015382 on trophoblast cell functions. Besides, the enhancing effects of miR-942-5p mimic on trophoblast cell proliferation, invasion, and angiogenesis could be eliminated by NDRG1 overexpression. In conclusion, our data showed that circ_0015382 inhibited trophoblast cell proliferation, invasion, and angiogenesis through regulating miR-942-5p/NDRG1 axis, providing a new mechanism for the regulation of PE progression.

Characterizing placental pericytes: Hypoxia and proangiogenic signalling

INTRODUCTION

Pericytes wrap microvessels and interact with endothelial cells to regulate vascular growth. Though pericyte dropout has been reported in pathological human placentae and mouse models of placental pathology, there has been limited investigation of the role and function of placental pericytes in vascular health and pathology. This study aimed to investigate the angiogenic potential of human placental pericytes relative to other villous cell populations.

METHODS

Primary human placental pericytes, human umbilical vein endothelial cells (HUVEC), and BeWo cells ( ± 20 μM forskolin) were cultured in 1 % O2 or ambient air, followed by analysis of secreted angiogenic factors (ELISA). Additionally, the placental pericytes and HUVECs were co-cultured in a 3D sprouting assay to assess the capacity of pericytes to contribute to vascular sprouts.

RESULTS

1 % O2 affected secretion of angiogenic factors in placental pericytes, HUVECs, and syncytialized BeWo cells. Specifically, in placental pericytes, angiopoietin-1 (ANG1) and soluble fms-like tyrosine kinase-1 (sFLT1) were decreased, while vascular endothelial growth factor (VEGF) was increased. In HUVECS, matrix metalloproteinase-2 (MMP2), VEGF, angiopoietin-2 (ANG2), platelet-derived growth factor beta (PDGFB), placental growth factor (PlGF), and sFLT1 were increased. In syncytialized BeWo cells, VEGF, MMP2, PDGFB, PlGF, and sFLT1 secretion were increased. Placental pericytes and HUVECS colocalized to vessel sprouts in the 3-D sprouting assay.

DISCUSSION

Hypoxic conditions altered placental pericyte, endothelial, and syncytialized BeWo secretion of angiogenic factors. We speculate that pericyte dropout and, by extension, the loss of pericyte-derived angiogenic factors in hypoxic conditions may contribute to compromised fetal vascular development observed in placental pathologies.

Human trophoblast organoids for improved prediction of placental ABC transporter-mediated drug transport

ATP-binding cassette (ABC) transporters, the important transmembrane efflux transporters, play an irreplaceable role in the placenta barrier. The disposition and drug-drug interaction of clinical drugs are also closely related to the functions of ABC transporters. The trophoblast is a unique feature of the placenta, which is crucial for normal placentation and maintenance during pregnancy. ABC transporters are abundantly expressed in placental syncytiotrophoblast, especially P-gp, BCRP, and MRPs. However, due to the lack of appropriate modeling systems, the molecular mechanisms of regulation between ABC transporters and trophoblast remains unclear. In this report, trophoblast organoids were cultured from human placental villi and developed into three-dimension structures with cavities. Trophoblast organoids exhibited transporter expression and localization comparable to that in villous tissue, indicating their physiological relevance for modeling drug transport. Moreover, fluorescent substrates can accumulate in organoids and be selectively inhibited by inhibitors, indicating the efflux function of ABC transporters (P-gp, BCRP, MRP1, and MRP2) in organoids. Two commonly used hypertension drugs and three antipsychotics were chosen to further validate this drug transport model and demonstrate varying degrees of inhibitory effects on ABC transporters. Overall, a new drug transport model mediated by ABC transporter has been successfully established based on human trophoblast organoids, which can be used to study drug transport in the placenta.

Assessment of nanotoxicity in a human placenta-on-a-chip from trophoblast stem cells

Maternal exposure to nanoparticles during gestation poses potential risks to fetal development. The placenta, serving as a vital interface for maternal-fetal interaction, plays a pivotal role in shielding the fetus from direct nanoparticle exposure. However, the impact of nanoparticles on placental function is still poorly understood, primarily due to the absence of proper human placental models. In this study, we established a placenta-on-a-chip model capable of recapitulating nanoparticle exposure to assess potential nanotoxicity. The model was assembled by coculturing human trophoblast stem cells (hTSCs) and endothelial cells within a dynamic microsystem. hTSCs exhibited progressive differentiation into syncytiotrophoblasts under continuous fluid flow, forming a bilayered trophoblastic epithelium that mimicking both structural and functional aspects of human placental villi. Copper oxide nanoparticles (CuO NPs) were introduced into the trophoblastic side to simulate maternal blood exposure. Our findings revealed that CuO NPs hindered hTSCs differentiation, leading to diminished hormone secretion and impaired glucose transport. Subsequent analysis indicated that CuO NPs disrupted the autophagic flux in trophoblasts and induced apoptosis. Furthermore, the placenta-on-a-chip model exhibited inflammatory responses to CuO NP exposure, including maternal macrophage activation, inflammatory cytokine secretion, and endothelial barrier disruption. Dysfunction of the placental barrier and the ensuing inflammatory cascades may contribute to aberrant fetal development. Overall, our placenta-on-a-chip model offers a promising platform for assessing nanoparticle exposure-related risks and conducting toxicology studies.

Hypoxia and loss of GCM1 expression prevents differentiation and contact inhibition in human trophoblast stem cells

The placenta develops alongside the embryo and nurtures fetal development to term. During the first stages of embryonic development, due to low blood circulation, the blood and ambient oxygen supply is very low (~1-2% O2) and gradually increases upon placental invasion. While a hypoxic environment is associated with stem cell self-renewal and proliferation, persistent hypoxia may have severe effects on differentiating cells and could be the underlying cause of placental disorders. We find that human trophoblast stem cells (hTSC) thrive in low oxygen, whereas differentiation of hTSC to trophoblast to syncytiotrophoblast (STB) and extravillous trophoblast (EVT) is negatively affected by hypoxic conditions. The pro-differentiation factor GCM1 (human Glial Cell Missing-1) is downregulated in low oxygen, and concordantly there is substantial reduction of GCM1-regulated genes in hypoxic conditions. Knockout of GCM1 in hTSC caused impaired EVT and STB formation and function, reduced expression of differentiation-responsive genes, and resulted in maintenance of self-renewal genes. Treatment with a PI3K inhibitor reported to reduce GCM1 protein levels likewise counteracts spontaneous or directed differentiation. Additionally, chromatin immunoprecipitation of GCM1 showed enrichment of GCM1-specific binding near key transcription factors upregulated upon differentiation including the contact inhibition factor CDKN1C. Loss of GCM1 resulted in downregulation of CDKN1C and corresponding loss of contact inhibition, implicating GCM1 in regulation of this critical process.

Establishment of functional trophoblast organoids from trophoblast cells of bovine placenta

The placenta is an organ that plays a vital role in successful pregnancies, and the failure of early placentation is a significant factor leading to abortion in ruminant species. However, the mechanisms involved in the development and differentiation of bovine placenta remain elusive due to the lack of suitable in vitro placental models. This study aimed to develop an effective method for generating the bovine functional trophoblast organoids by assembling bovine primary trophoblast cells (PBTCs) from the placenta or immortalized bovine placental trophoblast (BTCs) in a 3D culture system in vitro. PBTCs isolated from the 3-month-gestation placenta and BTCs rapidly proliferated and exhibited typical epithelioid morphology in the modified trophoblast organoid medium (TOM) for bovine. Furthermore, PBTCs and BTCs proliferating in the modified TOM were both CK7- and E-cadherin-positive. Both PBTCs or BTCs embedded into Matrigel droplets overlaid with modified TOM proliferated and formed trophoblast organoids after 15 days of culture. Moreover, the expression of syntrophoblast marker genes, including CD71, CD46, and chorionic somatomammotropin hormone 1 (CSH1), was detectable in both organoids derived from different types of trophoblast cells. Notably, the protein expression levels of various genes implicated in the establishment of early pregnancy in endometrial epithelium cells (EECs) was increased following coculture with bovine trophoblast organoids. Collectively, the bovine trophoblast organoids established in our study could serve as robust models for elucidating the essential physical functions of the placenta and the causes of pregnancy failures related to the placenta developmental disorders during early bovine pregnancy.

Integrated transcriptomic analysis and machine learning for characterizing diagnostic biomarkers and immune cell infiltration in fetal growth restriction

Background

Fetal growth restriction (FGR) occurs in 10% of pregnancies worldwide. Placenta dysfunction, as one of the most common causes of FGR, is associated with various poor perinatal outcomes. The main objectives of this study were to screen potential diagnostic biomarkers for FGR and to evaluate the function of immune cell infiltration in the process of FGR.

Methods

Firstly, differential expression genes (DEGs) were identified in two Gene Expression Omnibus (GEO) datasets, and gene set enrichment analysis was performed. Diagnosis-related key genes were identified by using three machine learning algorithms (least absolute shrinkage and selection operator, random forest, and support vector machine model), and the nomogram was then developed. The receiver operating characteristic curve, calibration curve, and decision curve analysis curve were used to verify the validity of the diagnostic model. Using cell-type identification by estimating relative subsets of RNA transcripts (CIBERSORT), the characteristics of immune cell infiltration in placental tissue of FGR were evaluated and the candidate key immune cells of FGR were screened. In addition, this study also validated the diagnostic efficacy of TREM1 in the real world and explored associations between TREM1 and various clinical features.

Results

By overlapping the genes selected by three machine learning algorithms, four key genes were identified from 290 DEGs, and the diagnostic model based on the key genes showed good predictive performance (AUC = 0.971). The analysis of immune cell infiltration indicated that a variety of immune cells may be involved in the development of FGR, and nine candidate key immune cells of FGR were screened. Results from real-world data further validated TREM1 as an effective diagnostic biomarker (AUC = 0.894) and TREM1 expression was associated with increased uterine artery PI (UtA-PI) (p-value = 0.029).

Conclusion

Four candidate hub genes (SCD, SPINK1, TREM1, and HIST1H2BB) were identified, and the nomogram was constructed for FGR diagnosis. TREM1 was not only associated with a variety of key immune cells but also correlated with increased UtA-PI. The results of this study could provide some new clues for future research on the prediction and treatment of FGR.

Gene expression profile of human placental villous pericytes in the first trimester - An analysis by single-cell RNA sequencing

Mesenchymal cells within theplacental villi play a crucial role in shaping the morphology of branching structures and driving the development of blood vessels. However, the markers and functions of placental villous pericytes (PVPs) as distinct subgroups of placental villous mesenchymal cells, remain unclear. Therefore, in this study, the markers and functions of PVPs were investigated. Single-cell sequencing data from the first-trimester placental villi was obtained and the Seurat tool was used to identify PVP markers. Gene Ontology (GO) analysis of specific genes was performed using the DAVID database. The Cellchat tool was employed to investigate the interaction signals between the PVPs and other cells. Expression of the PVP markers was confirmed using immunofluorescence. Presence of extracellular vesicles in the placental villous mesenchyme and PVPs was examined by transmission electron microscopy. Our findings revealed that renin (REN) and amphiregulin (AREG)-positive fibroblasts in the placental villi specifically expressed several classic pericyte markers. In the first trimester, certain conserved functions of pericytes were observed and they displayed tissue-specific functions such as in the integrin-mediated signaling pathway and extracellular exosomes. Moreover, the placental villous mesenchyme was found to be rich in extracellular vesicles. AREG is specifically transcribed in the first trimester PVPs, however, its protein was located in syncytiotrophoblasts. These insights contribute to a comprehensive understanding of early placental development and offer new therapeutic targets for placenta-derived pregnancy complications.

Hypermethylation and low expression of FOXM1 predisposes women to unexplained recurrent miscarriage by impairing trophoblast stem cell proliferation

Recurrent miscarriage (RM) is a distressing pregnancy complication with an unknown etiology. Increasing evidence indicates the relevance of dysregulation of human trophoblast stem cells (hTSCs), which may play a role in the development of RM. However, the potential molecular regulatory mechanism underlying the initiation and maintenance of hTSCs is yet to be fully elucidated. In this study, we performed data analysis and identified Forkhead box M1 (FOXM1) as a potential factor associated with RM. FOXM1 is a typical transcription factor known for its involvement in various pathophysiological processes, while the precise function of FOXM1 functions in hTSCs and RM remains incompletely understood. Utilizing RNA-seq, CUT&Tag, ChIP-qPCR, and sodium bisulfite conversion methods for methylation analysis, we elucidate the underlying regulatory mechanisms of FOXM1 in hTSCs and its implications in RM. Our findings demonstrate the relative high expression of FOXM1 in proliferating cytotrophoblasts (CTBs) compared to differentiated extravillous cytotrophoblasts (EVTs) and syncytiotrophoblasts (STBs). Besides, we provide evidence supporting a significant correlation between FOXM1 downregulation and the incidence of RM. Furthermore, we demonstrate the significant role of FOXM1 in regulating hTSCs proliferation and cell cycle through the transcriptional regulation of CDKN3, CCNB2, CCNA2, MAD2L1 and CDC25C. Notably, we observed a correlation between the downregulation of FOXM1 in RM and hypermethylation in its promoter region. Collectively, these results provide insights into the impact of FOXM1 on trophoblast regulation and offer a novel perspective on RM.

Epigenetic signatures of trophoblast lineage and their biological functions

Trophoblasts play a crucial role in embryo implantation and in interacting with the maternal uterus. The trophoblast lineage develops into a substantial part of the placenta, a temporary extra-embryonic organ, capable of undergoing distinctive epigenetic events during development. The critical role of trophoblast-specific epigenetic signatures in regulating placental development has become known, significantly advancing our understanding of trophoblast identity and lineage development. Scientific efforts are revealing how trophoblast-specific epigenetic signatures mediate stage-specific gene regulatory programming during the development of the trophoblast lineage. These epigenetic signatures have a significant impact on blastocyst formation, placental development, as well as the growth and survival of embryos and fetuses. In evolution, DNA hypomethylation in the trophoblast lineage is conserved, and there is a significant disparity in the control of epigenetic dynamics and the landscape of genomic imprinting. Scientists have used murine and human multipotent trophoblast cells as in vitro models to recapitulate the essential epigenetic processes of placental development. Here, we review the epigenetic signatures of the trophoblast lineage and their biological functions to enhance our understanding of placental evolution, development, and function.

Trophectoderm grade as a predictor of beta human-chorionic gonadotropin rise in early pregnancy

PURPOSE

To evaluate the association, if any, between the grade of the trophectoderm (TE) and the rate at which β-human-chorionic gonadotropin (β-HCG) rises in early pregnancy.

METHODS

This is a retrospective cohort study including 1116 singleton clinical pregnancies resulting from in vitro fertilization with single day 5 blastocyst transfer at an academic fertility center. TE quality was assessed by trained embryologists employing standard criteria. Three groups were formed based on the TE grade: grade A (n = 358), grade B (n = 628), and grade C (n = 130). Main outcome measure was the rise (%) in serum levels of β-HCG (days 12 to 14 post embryo transfer), using the following formula [(β-HCG D14 - β-HCG D12) * 100/β-HCG D12].

RESULTS

Fresh embryo transfers accounted for 64.1% of the population. Overall, in adjusted models there were no significant differences in the β-HCG% rise when comparing the TE grade C group to TE grade A [adjβ (95%CI): 10.09 (- 0.05, 20.22)] or when comparing TE grade Β group to TE grade A [4.46 (- 2.97, 11.88)]. When the analysis was restricted to fresh embryo transfers, significant differences were observed in the % rise of β-HCG when comparing the TE grade C group to TE grade A [adjβ (95%CI): 21.71 (5.67, 37.74)], but not when comparing the TE grade B group to TE grade A [2.68 (- 5.59, 10.95)]. In frozen transfers, there were no significant differences.

CONCLUSION

TE grade appears to impact early pregnancy serum β-HCG levels in the setting of a fresh day 5 embryo transfer, even after adjusting for potential confounders.

Per- and polyfluoroalkyl substances (PFAS) and hypertensive disorders of Pregnancy- integration of epidemiological and mechanistic evidence

BACKGROUND

Hypertensive disorders of pregnancy (HDP) remain a significant global health burden despite medical advancements. HDP prevalence appears to be rising, leading to increased maternal and fetal complications, mortality, and substantial healthcare costs. The etiology of HDP are complex and multifaceted, influenced by factors like nutrition, obesity, stress, metabolic disorders, and genetics. Emerging evidence suggests environmental pollutants, particularly Per- and polyfluoroalkyl substances (PFAS), may contribute to HDP development.

OBJECTIVE

This review integrates epidemiological and mechanistic data to explore the intricate relationship between PFAS exposure and HDP.

EPIDEMIOLOGICAL EVIDENCE

Studies show varying degrees of association between PFAS exposure and HDP, with some demonstrating positive correlations, particularly with preeclampsia. Meta-analyses suggest potential fetal sex-specific differences in these associations.

MECHANISTIC INSIGHTS

Mechanistically, PFAS exposure appears to disrupt vascular hemodynamics, placental development, and critical processes like angiogenesis and sex steroid regulation. Experimental studies reveal alterations in the renin-angiotensin system, trophoblast invasion, oxidative stress, inflammation, and hormonal dysregulation - all of which contribute to HDP pathogenesis. Elucidating these mechanisms is crucial for developing preventive strategies.

THERAPEUTIC POTENTIAL

Targeted interventions such as AT2R agonists, caspase inhibitors, and modulation of specific microRNAs show promise in mitigating adverse outcomes associated with PFAS exposure during pregnancy.

KNOWLEDGE GAPS AND FUTURE DIRECTIONS

Further research is needed to comprehensively understand the full spectrum of PFAS-induced placental alterations and their long-term implications for maternal and fetal health. This knowledge will be instrumental in developing effective preventive and therapeutic strategies for HDP in a changing environmental landscape.

Understanding the intersection between placental development and cancer: Lessons from the tumor suppressor BAP1

The placenta, a pivotal organ in mammalian reproduction, allows nutrient exchange and hormonal signaling between the mother and the developing fetus. Understanding its molecular intricacies is essential for deciphering normal embryonic development and pathological conditions such as tumorigenesis. Here, we explore the multifaceted role of the tumor suppressor BRCA1-associated protein 1 (BAP1) in cancer and placentation. Initially recognized for its tumor-suppressive properties, BAP1 has emerged as a key regulator at the intersection of tumorigenesis and placental development. BAP1 influences crucial cellular processes such as cell death, proliferation, metabolism, and response to hypoxic conditions. By integrating insights from tumor and developmental biology, we illuminate the complex molecular pathways orchestrated by BAP1. This perspective highlights BAP1's significant impact on both cancer and placental development, and suggests novel therapeutic strategies that could improve outcomes for pregnancy disorders and cancer.

EFFECTS OF ARYL HYDROCARBON RECEPTOR LIGAND TCDD ON HUMAN TROPHOBLAST CELL DEVELOPMENT

BACKGROUND

The primary interface between mother and fetus, the placenta, serves two critical functions: extraction of nutrients from the maternal compartment and facilitation of nutrient delivery to the developing fetus. This delivery system also serves as a barrier to environmental exposures. The aryl hydrocarbon receptor (AHR) is an important component of the barrier. AHR signaling is activated by environmental pollutants and toxicants that can potentially affect cellular and molecular processes, including those controlling trophoblast cell development and function.

OBJECTIVES

In this study, we investigated the impact of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an effective AHR ligand, exposure on human trophoblast cells.

METHODS

Human trophoblast stem (TS) cells were used as in vitro model system for investigating the downstream consequences of AHR activation. The actions TCDD were investigated in human TS cells maintained in the stem state or in differentiating TS cells.

RESULTS

TCDD exposure stimulated the expression of CYP1A1 and CYP1B1 in human TS cells. TCDD was effective in stimulating CYP1A1 and CYP1B1 expression and altering gene expression profiles in human TS cells maintained in the stem cell state or induced to differentiate into extravillous trophoblast cells (EVT) or syncytiotrophoblast (ST). These actions were dependent upon the presence of AHR. TCDD exposure did not adversely affect maintenance of the TS cell stem state or the ability of TS cells to differentiate into EVT cells or ST. However, TCDD exposure did promote the biosynthesis of 2 methoxy estradiol (2ME), a biologically active catechol estrogen, with the potential to modify the maternal-fetal interface.

DISCUSSION

Human trophoblast cell responses to TCDD were dependent upon AHR signaling and possessed the potential to shape development and function of the human placentation site.

Glutamine metabolism promotes human trophoblast cell invasion via COL1A1 mediated by PI3K-AKT pathway

Abnormal trophoblast invasion function is an important cause of recurrent spontaneous abortion (RSA). Recent research has revealed a connection between glutamine metabolism and RSA. However, the interplay between these three factors and their related mechanisms remains unclear. To address this issue, we collected villus tissues from 10 healthy women with induced abortion and from 10 women with RSA to detect glutamine metabolism. Then, the trophoblast cell line HTR-8/SVneo was used in vitro to explore the effect of glutamine metabolism on trophoblast cells invasion, which was tested by transwell assay. We found that the concentration of glutamine in the villi of the normal pregnancy group was significantly higher than that in the RSA group. Correspondingly, the expression levels of key enzymes involved in glutamine synthesis and catabolism, including glutamine synthetase and glutaminase, were significantly higher in the villi of the normal pregnancy group. Regarding trophoblast cells, glutamine markedly enhanced the proliferative and invasive abilities of HTR-8/SVneo cells. Additionally, collagen type I alpha 1 (COL1A1) was confirmed to be a downstream target of glutamine, and glutamine also activated the PI3K-AKT pathway in HTR-8/SVneo cells. These findings indicate that glutamine metabolism facilitates the invasion of trophoblasts by up-regulating COL1A1 expression through the activation of the PI3K-AKT pathway, but the specific mechanism of COL1A1 requires further study.

NOTUM-MEDIATED WNT SILENCING DRIVES EXTRAVILLOUS TROPHOBLAST CELL LINEAGE DEVELOPMENT

Trophoblast stem (TS) cells have the unique capacity to differentiate into specialized cell types, including extravillous trophoblast (EVT) cells. EVT cells invade into and transform the uterus where they act to remodel the vasculature facilitating the redirection of maternal nutrients to the developing fetus. Disruptions in EVT cell development and function are at the core of pregnancy-related disease. WNT-activated signal transduction is a conserved regulator of morphogenesis of many organ systems, including the placenta. In human TS cells, activation of canonical WNT signaling is critical for maintenance of the TS cell stem state and its downregulation accompanies EVT cell differentiation. We show that aberrant WNT signaling undermines EVT cell differentiation. Notum, palmitoleoyl-protein carboxylesterase (NOTUM), a negative regulator of canonical WNT signaling, was prominently expressed in first trimester EVT cells developing in situ and upregulated in EVT cells derived from human TS cells. Furthermore, NOTUM was required for optimal human TS cell differentiation to EVT cells. Activation of NOTUM in EVT cells is driven, at least in part, by endothelial PAS domain 1 (also called hypoxia-inducible factor 2 alpha). Collectively, our findings indicate that canonical WNT signaling is essential for maintenance of human trophoblast cell stemness and regulation of human TS cell differentiation. Downregulation of canonical WNT signaling via the actions of NOTUM is required for optimal EVT cell differentiation.

Alteration of Trophoblast Syncytialization by Plasmodium falciparum-Infected Erythrocytes

Malaria during pregnancy has been associated with significant risks to both the mother and the fetus, leading to complications such as anemia, low birth weight, and increased infant mortality. The trophoblast cells, a key component of the placenta, are crucial for nutrient and oxygen exchange between mother and fetus. The differentiation of cytotrophoblasts (CTBs) into syncytiotrophoblasts (STBs) is critical for proper pregnancy development. These cells form the bi-stratified epithelium surrounding the placental villi. While previous studies have described an inflammatory activation of STB cells exposed to Plasmodium falciparum-infected erythrocytes (P. falciparum-IE) or components such as hemozoin (HZ), little is known about the direct effect this parasite may have on the epithelial turnover and function of trophoblast cells. This study aims to contribute to understanding mechanisms leading to placental damage during placental malaria using a BeWo cell line as a differentiation model. It was found that P. falciparum-IE interferes with the fusion of BeWo cells, affecting the differentiation process of trophoblast. A reduction in syncytialization could be associated with the adverse effects of infection in fetal health, altering the remodeling of the trophoblast epithelial barrier and reducing their capacity to exchange substances. However, further studies are necessary to assess alterations in the functionality of this epithelium.

Maternal Vitamin B12 in Pregnancy and Placental Development

Vitamin B12, or cobalamin, is an essential nutrient required for diverse physiological functions secondary to its role as a critical cofactor for two mammalian enzymes, methionine synthase and methylmalonyl-CoA mutase. While essential throughout all life stages, several pathways that require vitamin B12, including hematopoiesis, myelination, and DNA/histone methylation, are particularly critical during pregnancy and fetal development. This narrative review aims to describe vitamin B12 in pregnancy, with emphasis on the placenta's role in ensuring adequate nutrition of the fetus and impacts of vitamin B12 deficiency on placental development and function. Our literature search included preclinical model systems and human cohorts and interventions. Our review identified evidence of B12 deficiency resulting in impaired placental development, greater placental inflammation, and modulation of placental docosahexaenoic acid concentration, collectively suggestive of vitamin B12 deficiency as a determinant of both maternal and fetal health outcomes. Heterogeneity in study design complicated generalization of findings. Future studies should consider selecting a B12 marker that is relatively stable across pregnancy, such as holotranscobalamin, while accounting for important confounders such as maternal folate.

Rapid retinoic acid-induced trophoblast cell model from human induced pluripotent stem cells

A limited number of accessible and representative models of human trophoblast cells currently exist for the study of placentation. Current stem cell models involve either a transition through a naïve stem cell state or precise dynamic control of multiple growth factors and small-molecule cues. Here, we demonstrated that a simple five-day treatment of human induced pluripotent stem cells with two small molecules, retinoic acid (RA) and Wnt agonist CHIR 99021 (CHIR), resulted in rapid, synergistic upregulation of CDX2. Transcriptomic analysis of RA + CHIR-treated cells showed high similarity to primary trophectoderm cells. Multipotency was verified via further differentiation towards cells with syncytiotrophoblast or extravillous trophoblast features. RA + CHIR-treated cells were also assessed for the established criteria defining a trophoblast cell model, and they possess all the features necessary to be considered valid. Collectively, our data demonstrate a facile, scalable method for generating functional trophoblast-like cells in vitro to better understand the placenta.

Modeling the human placenta: in vitro applications in developmental and reproductive toxicology

During its temporary tenure, the placenta has extensive and specialized functions that are critical for pre- and post-natal development. The consequences of chemical exposure in utero can have profound effects on the structure and function of pregnancy-associated tissues and the life-long health of the birthing person and their offspring. However, the toxicological importance and critical functions of the placenta to embryonic and fetal development and maturation have been understudied. This narrative will review early placental development in humans and highlight some in vitro models currently in use that are or can be applied to better understand placental processes underlying developmental toxicity due to in utero environmental exposures.

Unveiling the human fetal-maternal interface during the first trimester: biophysical knowledge and gaps

The intricate interplay between the developing placenta and fetal-maternal interactions is critical for pregnancy outcomes. Despite advancements, gaps persist in understanding biomechanics, transport processes, and blood circulation parameters, all of which are crucial for safe pregnancies. Moreover, the complexity of fetal-maternal interactions led to conflicting data and methodological variations. This review presents a comprehensive overview of current knowledge on fetal-maternal interface structures, with a particular focus on the first trimester. More in detail, the embryological development, structural characteristics, and physiological functions of placental chorionic plate and villi, fetal membranes and umbilical cord are discussed. Furthermore, a description of the main structures and features of maternal and fetal fluid dynamic exchanges is provided. However, ethical constraints and technological limitations pose still challenges to studying early placental development directly, which calls for sophisticated in vitro, microfluidic organotypic models for advancing our understanding. For this, knowledge about key in vivo parameters are necessary for their design. In this scenario, the integration of data from later gestational stages and mathematical/computational simulations have proven to be useful tools. Notwithstanding, further research into cellular and molecular mechanisms at the fetal-maternal interface is essential for enhancing prenatal care and improving maternal and fetal health outcomes.

Leveraging chorionic villus biopsies for the derivation of patient-specific trophoblast stem cells

Human trophoblast stem (TS) cells are an informative in vitro model for the generation and testing of biologically meaningful hypotheses. The goal of this project was to derive patient-specific TS cell lines from clinically available chorionic villus sampling biopsies. Cell outgrowths were captured from human chorionic villus tissue specimens cultured in modified human TS cell medium. Cell colonies emerged early during the culture and cell lines were established and passaged for several generations. Karyotypes of the newly established chorionic villus-derived trophoblast stem (TS CV ) cell lines were determined and compared to initial genetic diagnoses from freshly isolated chorionic villi. Phenotypes of TSCV cells in the stem state and following differentiation were compared to cytotrophoblast-derived TS (TS CT ) cells. TSCV and TSCT cells uniformly exhibited similarities in the stem state and following differentiation into syncytiotrophoblast and extravillous trophoblast cells. Chorionic villus tissue specimens provide a valuable source for TS cell derivation. They expand the genetic diversity of available TS cells and are associated with defined clinical outcomes. TSCV cell lines provide a new set of experimental tools for investigating trophoblast cell lineage development.

Development of systemic and mucosal immune responses against gut microbiota in early life and implications for the onset of allergies

The early microbial colonization of human mucosal surfaces is essential for the development of the host immune system. Already during pregnancy, the unborn child is prepared for the postnatal influx of commensals and pathogens via maternal antibodies, and after birth this protection is continued with antibodies in breast milk. During this critical window of time, which extends from pregnancy to the first year of life, each encounter with a microorganism can influence children's immune response and can have a lifelong impact on their life. For example, there are numerous links between the development of allergies and an altered gut microbiome. However, the exact mechanisms behind microbial influences, also extending to how viruses influence host-microbe interactions, are incompletely understood. In this review, we address the impact of infants' first microbial encounters, how the immune system develops to interact with gut microbiota, and summarize how an altered immune response could be implied in allergies.

Single-cell transcriptomics reveal differences between chorionic and basal plate cytotrophoblasts and trophoblast stem cells

Cytotrophoblast (CTB) of the early gestation human placenta are bipotent progenitor epithelial cells, which can differentiate into invasive extravillous trophoblast (EVT) and multinucleated syncytiotrophoblast (STB). Trophoblast stem cells (TSC), derived from early first trimester placentae, have also been shown to be bipotential. In this study, we set out to probe the transcriptional diversity of first trimester CTB and compare TSC to various subgroups of CTB. We performed single-cell RNA sequencing on six normal placentae, four from early (6-8 weeks) and two from late (12-14 weeks) first trimester, of which two of the early first trimester cases were separated into basal (maternal) and chorionic (fetal) fractions prior to sequencing. We also sequenced three TSC lines, derived from 6-8 week placentae, to evaluate similarities and differences between primary CTB and TSC. CTB clusters displayed notable distinctions based on gestational age, with early first trimester placentae showing enrichment for specific CTB subtypes, further influenced by origin from the basal or chorionic plate. Differential expression analysis of CTB from basal versus chorionic plate highlighted pathways associated with proliferation, unfolded protein response, and oxidative phosphorylation. We identified trophoblast states representing initial progenitor CTB, precursor STB, precursor and mature EVT, and multiple CTB subtypes. CTB progenitors were enriched in early first trimester placentae, with basal plate cells biased toward EVT, and chorionic plate cells toward STB, precursors. Clustering and trajectory inference analysis indicated that TSC were most like EVT precursor cells, with only a small percentage of TSC on the pre-STB differentiation trajectory. This was confirmed by flow cytometric analysis of 6 different TSC lines, which showed uniform expression of proximal column markers ITGA2 and ITGA5. Additionally, we found that ITGA5+ CTB could be plated in 2D, forming only EVT upon spontaneous differentiation, but failed to form self-renewing organoids; conversely, ITGA5-CTB could not be plated in 2D, but readily formed organoids. Our findings suggest that distinct CTB states exist in different regions of the placenta as early as six weeks gestation and that current TSC lines most closely resemble ITGA5+ CTB, biased toward the EVT lineage.

METTL3 shapes m6A epitranscriptomic landscape for successful human placentation

Methyltransferase-like 3 (METTL3), the catalytic enzyme of methyltransferase complex for m6A methylation of RNA, is essential for mammalian development. However, the importance of METTL3 in human placentation remains largely unexplored. Here, we show that a fine balance of METTL3 function in trophoblast cells is essential for successful human placentation. Both loss-of and gain-in METTL3 functions are associated with adverse human pregnancies. A subset of recurrent pregnancy losses and preterm pregnancies are often associated with loss of METTL3 expression in trophoblast progenitors. In contrast, METTL3 is induced in pregnancies associated with fetal growth restriction (FGR). Our loss of function analyses showed that METTL3 is essential for the maintenance of human TSC self-renewal and their differentiation to extravillous trophoblast cells (EVTs). In contrast, loss of METTL3 in human TSCs promotes syncytiotrophoblast (STB) development. Global analyses of RNA m6A modification and METTL3-RNA interaction in human TSCs showed that METTL3 regulates m6A modifications on the mRNA molecules of critical trophoblast regulators, including GATA2, GATA3, TEAD1, TEAD4, WWTR1, YAP1, TFAP2C and ASCL2, and loss of METTL3 leads to depletion of mRNA molecules of these critical regulators. Importantly, conditional deletion of Mettl3 in trophoblast progenitors of an early post-implantation mouse embryo also leads to arrested self-renewal. Hence, our findings indicate that METLL3 is a conserved epitranscriptomic governor in trophoblast progenitors and ensures successful placentation by regulating their self-renewal and dictating their differentiation fate.

A Narrative Review on the Pathophysiology of Preeclampsia

Preeclampsia (PE) is a multifactorial pregnancy disorder characterized by hypertension and proteinuria, posing significant risks to both maternal and fetal health. Despite extensive research, its complex pathophysiology remains incompletely understood. This narrative review aims to elucidate the intricate mechanisms contributing to PE, focusing on abnormal placentation, maternal systemic response, oxidative stress, inflammation, and genetic and epigenetic factors. This review synthesizes findings from recent studies, clinical trials, and meta-analyses, highlighting key molecular and cellular pathways involved in PE. The review integrates data on oxidative stress biomarkers, angiogenic factors, immune interactions, and mitochondrial dysfunction. PE is initiated by poor placentation due to inadequate trophoblast invasion and improper spiral artery remodeling, leading to placental hypoxia. This triggers the release of anti-angiogenic factors such as soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng), causing widespread endothelial dysfunction and systemic inflammation. Oxidative stress, mitochondrial abnormalities, and immune dysregulation further exacerbate the condition. Genetic and epigenetic modifications, including polymorphisms in the Fms-like tyrosine kinase 1 (FLT1) gene and altered microRNA (miRNA) expression, play critical roles. Emerging therapeutic strategies targeting oxidative stress, inflammation, angiogenesis, and specific molecular pathways like the heme oxygenase-1/carbon monoxide (HO-1/CO) and cystathionine gamma-lyase/hydrogen sulfide (CSE/H2S) pathways show promise in mitigating preeclampsia's effects. PE is a complex disorder with multifactorial origins involving abnormal placentation, endothelial dysfunction, systemic inflammation, and oxidative stress. Despite advances in understanding its pathophysiology, effective prevention and treatment strategies remain limited. Continued research is essential to develop targeted therapies that can improve outcomes for both mothers and their babies.

TFEB safeguards trophoblast syncytialization in humans and mice

Nutrient sensing and adaptation in the placenta are essential for pregnancy viability and proper fetal growth. Our recent study demonstrated that the placenta adapts to nutrient insufficiency through mechanistic target of rapamycin (mTOR) inhibition-mediated trophoblast differentiation toward syncytiotrophoblasts (STBs), a highly specialized multinucleated trophoblast subtype mediating extensive maternal-fetal interactions. However, the underlying mechanism remains elusive. Here, we unravel the indispensable role of the mTORC1 downstream transcriptional factor TFEB in STB formation both in vitro and in vivo. TFEB deficiency significantly impaired STB differentiation in human trophoblasts and placenta organoids. Consistently, systemic or trophoblast-specific deletion of Tfeb compromised STB formation and placental vascular construction, leading to severe embryonic lethality. Mechanistically, TFEB conferred direct transcriptional activation of the fusogen ERVFRD-1 in human trophoblasts and thereby promoted STB formation, independent of its canonical function as a master regulator of the autophagy-lysosomal pathway. Moreover, we demonstrated that TFEB directed the trophoblast syncytialization response driven by mTOR complex 1 (mTORC1) signaling. TFEB expression positively correlated with the reinforced trophoblast syncytialization in human fetal growth-restricted placentas exhibiting suppressed mTORC1 activity. Our findings substantiate that the TFEB-fusogen axis ensures proper STB formation during placenta development and under nutrient stress, shedding light on TFEB as a mechanistic link between nutrient-sensing machinery and trophoblast differentiation.

Epigenetic changes regulating the epithelial-mesenchymal transition in human trophoblast differentiation

The phenotype of human placental extravillous trophoblast (EVT) at the end of pregnancy reflects both first trimester differentiation from villous cytotrophoblast (CTB) and later gestational changes, including loss of proliferative and invasive capacity. Invasion abnormalities are central to two major placental pathologies, preeclampsia and placenta accreta spectrum, so characterization of the corresponding normal processes is crucial. In this report, our gene expression analysis, using purified human CTB and EVT cells, highlights an epithelial-mesenchymal transition (EMT) mechanism underlying CTB-EVT differentiation and provides a trophoblast-specific EMT signature. In parallel, DNA methylation profiling shows that CTB cells, already hypomethylated relative to non-trophoblast cell lineages, show further genome-wide hypomethylation in the transition to EVT. However, a small subgroup of genes undergoes gains of methylation (GOM) in their regulatory regions or gene bodies, associated with differential mRNA expression (DE). Prominent in this GOM-DE group are genes involved in the EMT, including multiple canonical EMT markers and the EMT-linked transcription factor RUNX1, for which we demonstrate a functional role in modulating the migratory and invasive capacities of JEG3 trophoblast cells. This analysis of DE associated with locus-specific GOM, together with functional studies of an important GOM-DE gene, highlights epigenetically regulated genes and pathways acting in human EVT differentiation and invasion, with implications for obstetric disorders in which these processes are dysregulated.

KAT8-mediated H4K16ac is essential for sustaining trophoblast self-renewal and proliferation via regulating CDX2

Abnormal trophoblast self-renewal and differentiation during early gestation is the major cause of miscarriage, yet the underlying regulatory mechanisms remain elusive. Here, we show that trophoblast specific deletion of Kat8, a MYST family histone acetyltransferase, leads to extraembryonic ectoderm abnormalities and embryonic lethality. Employing RNA-seq and CUT&Tag analyses on trophoblast stem cells (TSCs), we further discover that KAT8 regulates the transcriptional activation of the trophoblast stemness marker, CDX2, via acetylating H4K16. Remarkably, CDX2 overexpression partially rescues the defects arising from Kat8 knockout. Moreover, increasing H4K16ac via using deacetylase SIRT1 inhibitor, EX527, restores CDX2 levels and promoted placental development. Clinical analysis shows reduced KAT8, CDX2 and H4K16ac expression are associated with recurrent pregnancy loss (RPL). Trophoblast organoids derived from these patients exhibit impaired TSC self-renewal and growth, which are significantly ameliorated with EX527 treatment. These findings suggest the therapeutic potential of targeting the KAT8-H4K16ac-CDX2 axis for mitigating RPL, shedding light on early gestational abnormalities.

SARS-CoV-2 Infection during Delivery Causes Histopathological Changes in the Placenta

BACKGROUND

SARS-CoV-2 can damage human placentas, leading to pregnancy complications, such as preeclampsia and premature birth. This study investigates the histopathological changes found in COVID-19-affected placentas.

MATERIALS AND METHODS

This study included 23 placentas from patients with active COVID-19 during delivery and 22 samples from patients without COVID-19 infection in their medical history. The samples underwent histopathological examination for pathology, such as trophoblast necrosis, signs of vessel damage, or fetal vascular malperfusion.

RESULTS

Newborns from the research group have lower weights and Apgar scores than healthy newborns. In the COVID-19 group, calcifications and collapsed intervillous space were more frequent, and inflammation was more severe than in the healthy group. At the same time, the placenta of SARS-CoV-2-positive patients showed signs of accelerated vascular maturation. Trophoblast necrosis was found only in the placentas of the research group. The expression of CD68+ was elevated in the COVID-19 cohort, suggesting that macrophages constituted a significant part of the inflammatory infiltrate. The increase in lymphocyte B markers was associated with placental infarctions, while high levels of CD3+, specific for cytotoxic T lymphocytes, correlated with vascular injury.

CONCLUSIONS

SARS-CoV-2 is associated with pathological changes in the placenta, including trophoblast necrosis, calcification, and accelerated villous maturation. Those changes appear to be driven by T cells and macrophages, whose increased expression reflects ongoing histiocytic intervillositis in the placenta.

c-FLIP facilitates ZIKV infection by mediating caspase-8/3-dependent apoptosis

c-FLIP functions as a dual regulator of apoptosis and inflammation, yet its implications in Zika virus (ZIKV) infection remain partially understood, especially in the context of ZIKV-induced congenital Zika syndrome (CZS) where both apoptosis and inflammation play pivotal roles. Our findings demonstrate that c-FLIP promotes ZIKV infection in placental cells and myeloid-derived macrophages, involving inflammation and caspase-8/3-mediated apoptosis. Moreover, our observations reveal that c-FLIP augments ZIKV infection in multiple tissues, including blood cell, spleen, uterus, testis, and the brain of mice. Notably, the partial deficiency of c-FLIP provides protection to embryos against ZIKV-induced CZS, accompanied by a reduction in caspase-3-mediated apoptosis. Additionally, we have found a distinctive parental effect of c-FLIP influencing ZIKV replication in fetal heads. In summary, our study reveals the critical role of c-FLIP as a positive regulator in caspase-8/3-mediated apoptosis during ZIKV infection, significantly contributing to the development of CZS.

Identification of HTRA4 as a Transcriptional Target of p63 in Trophoblast

The placenta plays a crucial role in pregnancy success. ΔNp63α (p63), a transcription factor from the TP53 family, is highly expressed in villous cytotrophoblasts (CTBs), the epithelial stem cells of the human placenta, and is involved in CTB maintenance and differentiation. We examined the mechanisms of action of p63 by identifying its downstream targets. Gene expression changes were evaluated following overexpression and knockdown of p63 in the JEG3 choriocarcinoma cell line, using microarray-based RNA profiling. High-temperature requirement A4 (HTRA4), a placenta-specific serine protease involved in trophoblast differentiation and altered in preeclampsia, was identified as a gene reciprocally regulated by p63, and its expression was characterized in primary human placental tissues by RNA-sequencing and in situ hybridization. Potential p63 DNA-binding motifs were identified in the HTRA4 promoter, and p63 occupancy at some of these sites was confirmed using chromatin immunoprecipitation, followed by quantitative PCR in both JEG3 and trophoblast stem cells. These data begin to identify members of the transcriptional network downstream of p63, thus laying the groundwork for probing mechanisms by which this important transcription factor regulates trophoblast stemness and differentiation.

Revealing the molecular landscape of human placenta: a systematic review and meta-analysis of single-cell RNA sequencing studies

BACKGROUND

With increasing significance of developmental programming effects associated with placental dysfunction, more investigations are devoted to improving the characterization and understanding of placental signatures in health and disease. The placenta is a transitory but dynamic organ adapting to the shifting demands of fetal development and available resources of the maternal supply throughout pregnancy. Trophoblasts (cytotrophoblasts, syncytiotrophoblasts, and extravillous trophoblasts) are placental-specific cell types responsible for the main placental exchanges and adaptations. Transcriptomic studies with single-cell resolution have led to advances in understanding the placenta's role in health and disease. These studies, however, often show discrepancies in characterization of the different placental cell types.

OBJECTIVE AND RATIONALE

We aim to review the knowledge regarding placental structure and function gained from the use of single-cell RNA sequencing (scRNAseq), followed by comparing cell-type-specific genes, highlighting their similarities and differences. Moreover, we intend to identify consensus marker genes for the various trophoblast cell types across studies. Finally, we will discuss the contributions and potential applications of scRNAseq in studying pregnancy-related diseases.

SEARCH METHODS

We conducted a comprehensive systematic literature review to identify different cell types and their functions at the human maternal-fetal interface, focusing on all original scRNAseq studies on placentas published before March 2023 and published reviews (total of 28 studies identified) using PubMed search. Our approach involved curating cell types and subtypes that had previously been defined using scRNAseq and comparing the genes used as markers or identified as potential new markers. Next, we reanalyzed expression matrices from the six available scRNAseq raw datasets with cell annotations (four from first trimester and two at term), using Wilcoxon rank-sum tests to compare gene expression among studies and annotate trophoblast cell markers in both first trimester and term placentas. Furthermore, we integrated scRNAseq raw data available from 18 healthy first trimester and nine term placentas, and performed clustering and differential gene expression analysis. We further compared markers obtained with the analysis of annotated and raw datasets with the literature to obtain a common signature gene list for major placental cell types.

OUTCOMES

Variations in the sampling site, gestational age, fetal sex, and subsequent sequencing and analysis methods were observed between the studies. Although their proportions varied, the three trophoblast types were consistently identified across all scRNAseq studies, unlike other non-trophoblast cell types. Notably, no marker genes were shared by all studies for any of the investigated cell types. Moreover, most of the newly defined markers in one study were not observed in other studies. These discrepancies were confirmed by our analysis on trophoblast cell types, where hundreds of potential marker genes were identified in each study but with little overlap across studies. From 35 461 and 23 378 cells of high quality in the first trimester and term placentas, respectively, we obtained major placental cell types, including perivascular cells that previously had not been identified in the first trimester. Importantly, our meta-analysis provides marker genes for major placental cell types based on our extensive curation.

WIDER IMPLICATIONS

This review and meta-analysis emphasizes the need for establishing a consensus for annotating placental cell types from scRNAseq data. The marker genes identified here can be deployed for defining human placental cell types, thereby facilitating and improving the reproducibility of trophoblast cell annotation.

TGFβ signalling: a nexus between inflammation, placental health and preeclampsia throughout pregnancy

BACKGROUND

The placenta is a unique and pivotal organ in reproduction, controlling crucial growth and cell differentiation processes that ensure a successful pregnancy. Placental development is a tightly regulated and dynamic process, in which the transforming growth factor beta (TGFβ) superfamily plays a central role. This family of pleiotropic growth factors is heavily involved in regulating various aspects of reproductive biology, particularly in trophoblast differentiation during the first trimester of pregnancy. TGFβ signalling precisely regulates trophoblast invasion and the cell transition from cytotrophoblasts to extravillous trophoblasts, which is an epithelial-to-mesenchymal transition-like process. Later in pregnancy, TGFβ signalling ensures proper vascularization and angiogenesis in placental endothelial cells. Beyond its role in trophoblasts and endothelial cells, TGFβ signalling contributes to the polarization and function of placental and decidual macrophages by promoting maternal tolerance of the semi-allogeneic foetus. Disturbances in early placental development have been associated with several pregnancy complications, including preeclampsia (PE) which is one of the severe complications. Emerging evidence suggests that TGFβ is involved in the pathogenesis of PE, thereby offering a potential target for intervention in the human placenta.

OBJECTIVE AND RATIONALE

This comprehensive review aims to explore and elucidate the roles of the major members of the TGFβ superfamily, including TGFβs, bone morphogenetic proteins (BMPs), activins, inhibins, nodals, and growth differentiation factors (GDFs), in the context of placental development and function. The review focusses on their interactions within the major cell types of the placenta, namely trophoblasts, endothelial cells, and immune cells, in both normal pregnancies and pregnancies complicated by PE throughout pregnancy.

SEARCH METHODS

A literature search was carried out using PubMed and Google Scholar, searching terms: 'TGF signalling preeclampsia', 'pregnancy TGF signalling', 'preeclampsia tgfβ', 'preeclampsia bmp', 'preeclampsia gdf', 'preeclampsia activin', 'endoglin preeclampsia', 'endoglin pregnancy', 'tgfβ signalling pregnancy', 'bmp signalling pregnancy', 'gdf signalling pregnancy', 'activin signalling pregnancy', 'Hofbauer cell tgfβ signalling', 'placental macrophages tgfβ', 'endothelial cells tgfβ', 'endothelium tgfβ signalling', 'trophoblast invasion tgfβ signalling', 'trophoblast invasion Smad', 'trophoblast invasion bmp', 'trophoblast invasion tgfβ', 'tgfβ preeclampsia', 'tgfβ placental development', 'TGFβ placental function', 'endothelial dysfunction preeclampsia tgfβ signalling', 'vascular remodelling placenta TGFβ', 'inflammation pregnancy tgfβ', 'immune response pregnancy tgfβ', 'immune tolerance pregnancy tgfβ', 'TGFβ pregnancy NK cells', 'bmp pregnancy NK cells', 'bmp pregnancy tregs', 'tgfβ pregnancy tregs', 'TGFβ placenta NK cells', 'TGFβ placenta tregs', 'NK cells preeclampsia', 'Tregs preeclampsia'. Only articles published in English until 2023 were used.

OUTCOMES

A comprehensive understanding of TGFβ signalling and its role in regulating interconnected cell functions of the main placental cell types provides valuable insights into the processes essential for successful placental development and growth of the foetus during pregnancy. By orchestrating trophoblast invasion, vascularization, immune tolerance, and tissue remodelling, TGFβ ligands contribute to the proper functioning of a healthy maternal-foetal interface. However, dysregulation of TGFβ signalling has been implicated in the pathogenesis of PE, where the shallow trophoblast invasion, defective vascular remodelling, decreased uteroplacental perfusion, and endothelial cell and immune dysfunction observed in PE, are all affected by an altered TGFβ signalling.

WIDER IMPLICATIONS

The dysregulation of TGFβ signalling in PE has important implications for research and clinical practice. Further investigation is required to understand the underlying mechanisms, including the role of different ligands and their regulation under pathophysiological conditions, in order to discover new therapeutic targets. Distinguishing between clinically manifested subtypes of PE and studying TGFβ signalling in different placental cell types holistically is an important first step. To put this knowledge into practice, pre-clinical animal models combined with new technologies are needed. This may also lead to improved human research models and identify potential therapeutic targets, ultimately improving outcomes for affected pregnancies and reducing the burden of PE.

Overexpressed Trophoblast Glycoprotein Contributes to Preeclampsia Development by Inducing Abnormal Trophoblast Migration and Invasion Toward the Uterine Spiral Artery

BACKGROUND

Preeclampsia is a significant pregnancy disorder with an unknown cause, mainly attributed to impaired spiral arterial remodeling.

METHODS

Using RNA sequencing, we identified key genes in placental tissues from healthy individuals and preeclampsia patients. Placenta and plasma samples from pregnant women were collected to detect the expression of TPBG (trophoblast glycoprotein). Pregnant rats were injected with TPBG-carrying adenovirus to detect preeclamptic features. HTR-8/SVneo cells transfected with a TPBG overexpression lentiviral vector were used in cell function experiments. The downstream molecular mechanisms of TPBG were explored using RNA sequencing and single-cell RNA sequencing data. TPBG expression was knocked down in the lipopolysaccharide-induced preeclampsia-like rat model to rescue the preeclampsia features. We also assessed TPBG's potential as an early preeclampsia predictor using clinical plasma samples.

RESULTS

TPBG emerged as a crucial differentially expressed gene, expressed specifically in syncytiotrophoblasts and extravillous trophoblasts. Subsequently, we established a rat model with preeclampsia-like phenotypes by intravenously injecting TPBG-expressing adenoviruses, observing impaired spiral arterial remodeling, thus indicating a causal correlation between TPBG overexpression and preeclampsia. Studies with HTR-8/SVneo cells, chorionic villous explants, and transwell assays showed TPBG overexpression disrupts trophoblast/extravillous trophoblast migration/invasion and chemotaxis. Notably, TPBG knockdown alleviated the lipopolysaccharide-induced preeclampsia-like rat model. We enhanced preeclampsia risk prediction in early gestation by combining TPBG expression with established clinical predictors.

CONCLUSIONS

These findings are the first to show that TPBG overexpression contributes to preeclampsia development by affecting uterine spiral artery remodeling. We propose TPBG levels in maternal blood as a predictor of preeclampsia risk. The proposed mechanism by which TPBG overexpression contributes to the occurrence of preeclampsia via its disruptive effect on trophoblast and extravillous trophoblast migration/invasion on uterine spiral artery remodeling, thereby increasing the risk of preeclampsia.

Regulation of placental amino acid transport in health and disease

Abnormal fetal growth, i.e., intrauterine growth restriction (IUGR) or fetal growth restriction (FGR) and fetal overgrowth, is associated with increased perinatal morbidity and mortality and is strongly linked to the development of metabolic and cardiovascular disease in childhood and later in life. Emerging evidence suggests that changes in placental amino acid transport may contribute to abnormal fetal growth. This review is focused on amino acid transport in the human placenta, however, relevant animal models will be discussed to add mechanistic insights. At least 25 distinct amino acid transporters with different characteristics and substrate preferences have been identified in the human placenta. Of these, System A, transporting neutral nonessential amino acids, and System L, mediating the transport of essential amino acids, have been studied in some detail. Importantly, decreased placental Systems A and L transporter activity is strongly associated with IUGR and increased placental activity of these two amino acid transporters has been linked to fetal overgrowth in human pregnancy. An array of factors in the maternal circulation, including insulin, IGF-1, and adiponectin, and placental signaling pathways such as mTOR, have been identified as key regulators of placental Systems A and L. Studies using trophoblast-specific gene targeting in mice have provided compelling evidence that changes in placental Systems A and L are mechanistically linked to altered fetal growth. It is possible that targeting specific placental amino acid transporters or their upstream regulators represents a novel intervention to alleviate the short- and long-term consequences of abnormal fetal growth in the future.

EGFR-targeted ionizable lipid nanoparticles enhance in vivo mRNA delivery to the placenta

The full potential of ionizable lipid nanoparticles (LNPs) as an in vivo nucleic acid delivery platform has not yet been realized given that LNPs primarily accumulate in the liver following systemic administration, limiting their success to liver-centric conditions. The engineering of LNPs with antibody targeting moieties can enable extrahepatic tropism by facilitating site-specific LNP tethering and driving preferential LNP uptake into receptor-expressing cell types via receptor-mediated endocytosis. Obstetric conditions stemming from placental dysfunction, such as preeclampsia, are characterized by overexpression of cellular receptors, including the epidermal growth factor receptor (EGFR), making targeted LNP platforms an exciting potential treatment strategy for placental dysfunction during pregnancy. Herein, an EGFR antibody-conjugated LNP (aEGFR-LNP) platform was developed by engineering LNPs with increasing densities of antibody functionalization. aEGFR-LNPs were screened in vitro in immortalized placental trophoblasts and in vivo in non-pregnant and pregnant mice and compared to non-targeted formulations for extrahepatic, antibody-targeted mRNA LNP delivery to the placenta. Our top performing LNP with an intermediate density of antibody functionalization (1:5 aEGFR-LNP) mediated a ∼twofold increase in mRNA delivery in murine placentas and a ∼twofold increase in LNP uptake in EGFR-expressing trophoblasts compared to non-targeted counterparts. These results demonstrate the potential of antibody-conjugated LNPs for achieving extrahepatic tropism, and the ability of aEGFR-LNPs in promoting mRNA delivery to EGFR-expressing cell types in the placenta.

A genome scale transcriptional regulatory model of the human placenta

Gene regulation is essential to placental function and fetal development. We built a genome-scale transcriptional regulatory network (TRN) of the human placenta using digital genomic footprinting and transcriptomic data. We integrated 475 transcriptomes and 12 DNase hypersensitivity datasets from placental samples to globally and quantitatively map transcription factor (TF)-target gene interactions. In an independent dataset, the TRN model predicted target gene expression with an out-of-sample R2 greater than 0.25 for 73% of target genes. We performed siRNA knockdowns of four TFs and achieved concordance between the predicted gene targets in our TRN and differences in expression of knockdowns with an accuracy of >0.7 for three of the four TFs. Our final model contained 113,158 interactions across 391 TFs and 7712 target genes and is publicly available. We identified 29 TFs which were significantly enriched as regulators for genes previously associated with preterm birth, and eight of these TFs were decreased in preterm placentas.

Demethylase FTO-mediated m6A modification of SIK1 modulates placental cytotrophoblast syncytialization in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) represents a common complication during pregnancy that affects fetoplacental development. We demonstrated the existence of impaired trophoblast syncytialization under hyperglycemic conditions. However, the exact mechanism remains unknown. RNA N6-methyladenosine (m6A) is an emerging regulatory mechanism of mRNA and participates in various biological processes. We described the global m6A modification pattern in T2DM placenta by the combined analysis of methylated RNA immunoprecipitation sequencing (MeRIP-Seq) and RNA sequencing (RNA-Seq). Both the m6A modification and expression of SIK1, which is critical for syncytialization, were significantly decreased in trophoblast exposed to hyperglycemic conditions. In addition, the m6A demethylase fat mass and obesity-associated protein (FTO) affects the expression and mRNA stability of SIK1 by binding to its 3'-untranslated region (UTR) m6A site. This work reveals that the FTO-m6A-SIK1 axis plays critical roles in regulating syncytialization in the placenta.

SP6 controls human cytotrophoblast fate decisions and trophoblast stem cell establishment by targeting MSX2 regulatory elements

The commitment and differentiation of human placental progenitor cytotrophoblast (CT) cells are crucial for a successful pregnancy, but the underlying mechanism remains poorly understood. Here, we identified the transcription factor (TF), specificity protein 6 (SP6), as a human species-specific trophoblast lineage TF expressed in human placental CT cells. Using pluripotent stem cells as a model, we demonstrated that SP6 controls CT generation and the establishment of trophoblast stem cells (TSCs) and identified msh homeobox 2 (MSX2) as the downstream effector in these events. Mechanistically, we showed that SP6 interacts with histone acetyltransferase P300 to alter the landscape of H3K27ac at targeted regulatory elements, thereby favoring transcriptional activation and facilitating CT cell fate decisions and TSC maintenance. Our results established SP6 as a regulator of the human trophoblast lineage and implied its role in placental development and the pathogenies of placental diseases.

Sex-biased regulatory changes in the placenta of native highlanders contribute to adaptive fetal development

Compared with lowlander migrants, native Tibetans have a higher reproductive success at high altitude though the underlying mechanism remains unclear. Here, we compared the transcriptome and histology of full-term placentas between native Tibetans and Han migrants. We found that the placental trophoblast shows the largest expression divergence between Tibetans and Han, and Tibetans show decreased immune response and endoplasmic reticulum stress. Remarkably, we detected a sex-biased expression divergence, where the male-infant placentas show a greater between-population difference than the female-infant placentas. The umbilical cord plays a key role in the sex-biased expression divergence, which is associated with the higher birth weight of the male newborns of Tibetans. We also identified adaptive histological changes in the male-infant placentas of Tibetans, including larger umbilical artery wall and umbilical artery intima and media, and fewer syncytial knots. These findings provide valuable insights into the sex-biased adaptation of human populations, with significant implications for medical and genetic studies of human reproduction.

Mechanisms of YAP1-mediated trophoblast ferroptosis in recurrent pregnancy loss

PURPOSE

The purpose of our study is to investigate the function of YAP1 in the trophoblast ferroptosis and maternal-fetal interface communication of RPL.

METHODS

We collected 25 villous tissues and detected the expression of YAP1. Cell counting kit-8 assay, scratch wound-healing assay, and Matrigel invasion assay were performed to observe the proliferation, migration, and invasion of HTR-8/SVneo and JAR cells. Subsequently, measured the levels of reactive oxygen species (ROS), malondialdehyde (MDA), reduced glutathione (GSH), SLC7A11, SOD2, and GPX4. Ultimately, the use of ferroptosis activator (erastin) and inhibitor (Ferrostatin-1, fer-1) further confirmed the regulation by YAP1. In addition, established an in vitro-induced cell model to study the effect of YAP1 on the decidualization process. Finally, animal models were implemented for further confirmation.

RESULTS

We found that YAP1 was downregulated in RPL patients. Overexpression of YAP1 could significantly enhance the proliferation, migration, and invasion of trophoblasts, and inhibit ferroptosis. Knocking down YAP1 exhibited the opposite effect. Rescue experiments have shown that YAP1 could upregulate the expression of SLC7A11 and GPX4, which are key molecules in the classic pathway of ferroptosis. In addition, the decidualization was impaired when hESCs were treated with conditioned medium of YAP1 knockdown trophoblasts. Moreover, we found that Yap1, Slc7a11, and Gpx4 were downregulated in the RPL mice, along with increased MDA and decreased GSH.

CONCLUSION

Downregulation of YAP1 induces ferroptosis, thereby damaging the trophoblast invasion processes, which also disturbs the communication at the maternal-fetal interface. Our study identified YAP1 as a potential key molecule in the pathogenesis of RPL.

Maternal obesity and placental function: impaired maternal-fetal axis

The prevalence of maternal obesity rapidly increases, which represents a major public health concern worldwide. Maternal obesity is characteristic by metabolic dysfunction and chronic inflammation. It is associated with health problems in both mother and offspring. Increasing evidence indicates that the placenta is an axis connecting maternal obesity with poor outcomes in the offspring. In this brief review, we have summarized the current data regarding deregulated placental function in maternal obesity. The data show that maternal obesity induces numerous placental defects, including lipid and glucose metabolism, stress response, inflammation, immune regulation and epigenetics. These placental defects affect each other and result in a stressful intrauterine environment, which transduces and mediates the adverse effects of maternal obesity to the fetus. Further investigations are required to explore the exact molecular alterations in the placenta in maternal obesity, which may pave the way to develop specific interventions for preventing epigenetic and metabolic programming in the fetus.

Cytochrome c oxidase IV isoform 1 (COX4-1) regulates the proliferation, migration and invasion of trophoblast cells via modulating mitochondrial function

INTRODUCTION

Spontaneous miscarriage is a common complication of early pregnancy. Previous studies have shown that mitochondrial function plays an important role in establishment of a successful pregnancy. Cytochrome c oxidase subunit 4 isoform 1 (COX4I1), a component of electron transport chain complex Ⅳ, is required for coupling the rate of ATP production to energetic requirements. However, there is very limited research on its role in trophoblast biology and how its dysfunction may contribute to spontaneous miscarriage.

METHODS

Placental villi (7-10 weeks gestational age) collected from either induced termination of pregnancy or after spontaneous miscarriage were examined for expression of COX4I1. COX4I1 was knocked down by siRNA transfection of primary isolates of EVT cells. Real-time cell analysis (RTCA) and 5-Ethynyl-2'-deoxyuridine (EdU) were used to detect changes in proliferation ability after COX4I1 knockdown of EVT cells. Migration and invasion indices were determined by RTCA. Mitochondrial morphology was observed via MitoTracker staining. Oxidative phosphorylation, ATP production, and glycolysis in COX4I1-deficient cells and controls were assessed by a cellular energy metabolism analyzer (Seahorse).

RESULTS

In placental villous tissue, COX4I1 expression was significantly decreased in the spontaneous miscarriage group. Knockdown of COX4I1 inhibited EVT cell proliferation, increased the migration and invasion ability and mitochondrial fusion of EVT cells. Mitochondrial respiration and glycolysis were impaired in COX4I1-deficient EVT cells. Knockdown of MMP1 could rescue the increased migration and invasion induced by COX4I1 silencing.

DISCUSSION

Low expression of COX4I1 leads to mitochondrial dysfunction in EVT, resulting in altered trophoblast function, and ultimately to pregnancy loss.

Renalase Levels are Decreased in Maternal Blood and Placental Tissues in Pregnancies Associated with Preterm Preeclampsia

Preeclampsia (PEC) is a complication of pregnancy associated with hypertension and the risk of eclampsia. The pathophysiology of PEC is unknown and identifying factors associated with PEC during pregnancy is crucial for placental, fetal, and maternal health. Renalase (RNLS) is an anti-inflammatory secretory flavoprotein associated with hypertension. Recent data demonstrated a correlation between maternal serum RNLS and PEC, and work from our group identified RNLS expression in the placenta. However, it remains unknown whether RNLS levels in placenta are altered by preeclampsia. Additionally, it is unclear if there is a differential effect of preterm and term PEC on RNLS. We demonstrate that serum RNLS was reduced in preterm cases of PEC. Similarly, placental RNLS was diminished in the chorion of preterm cases of PEC. However, a reduction of RNLS in the decidua was observed with all cases of PEC, while the levels of RNLS within the placental villi were similar in all cases. Overall, we demonstrate that RNLS correlates with PEC both systemically in maternal serum and locally within the placenta, with variable effects on the different layers of the placenta and more pronounced in preterm cases.