Single-cell profiling of the human decidual immune microenvironment in patients with recurrent pregnancy loss

Inhibition of NFAT promotes loss of tissue resident uterine natural killer cells and attendant pregnancy complications in humans

Uterine natural killer cells (uNKs) are a tissue resident lymphocyte population that are critical for pregnancy success. Although mouse models have demonstrated that NK deficiency results in abnormal placentation and poor pregnancy outcomes, the generalizability of this knowledge to humans remains unclear. Here we identify uterus transplant (UTx) recipients as a human population with reduced uNK cells and altered pregnancy phenotypes. We show that the NK reduction in UTx correlates with impaired transcriptional programming of NK tissue residency arising from the inhibition of NFAT-mediated signaling. Our observations suggest that NFAT-dependent genes modulate multiple molecular tissue residency programs in uNKs. These include early residency programs involving AP-1-family transcription factors and TGF-β-mediated upregulation of surface integrins. Collectively, our data identify a previously undescribed role for NFAT in uterine NK tissue residency and provide novel mechanistic insights into the biologic basis of pregnancy complications due to alteration of tissue resident NK subsets in humans.

One Sentence Summary

Role of NFAT in uterine NK cell tissue residency.

Development of a humanized mouse model with functional human materno-fetal interface immunity

Materno-fetal immunity possesses specialized characteristics to ensure pathogen clearance while maintaining tolerance to the semiallogeneic fetus. Most of our understanding on human materno-fetal immunity is based on conventional rodent models that may not precisely represent human immunological processes owing to the huge evolutionary divergence. Herein, we developed a pregnant human immune system (HIS) mouse model through busulfan preconditioning, which hosts multilineage human immune subset reconstitution at the materno-fetal interface. Human materno-fetal immunity exhibits a tolerogenic feature at the midgestation stage (embryonic day [E] 14.5), and human immune regulatory subsets were detected in the decidua. However, the immune system switches to an inflammatory profile at the late gestation stage (E19). A cell-cell interaction network contributing to the alternations in the human materno-fetal immune atmosphere was revealed based on single-cell RNA-Seq analysis, wherein human macrophages played crucial roles by secreting several immune regulatory mediators. Furthermore, depletion of Treg cells at E2.5 and E5.5 resulted in severe inflammation and fetus rejection. Collectively, these results demonstrate that the pregnant HIS mouse model permits the development of functional human materno-fetal immunity and offers a tool for human materno-fetal immunity investigation to facilitate drug discovery for reproductive disorders.

CD36-mediated arachidonic acid influx from decidual stromal cells increases inflammatory macrophages in miscarriage

Spontaneous abortion is associated with aberrant lipid metabolism, but the underlying mechanisms remain unclear. Here, we show that lipids are accumulated in decidual stromal cells (DSCs) and macrophages (dMφs) in women with miscarriage and mouse abortion-prone models. Moreover, we show that excessive lipids from DSCs are transferred to dMφs via a CD36-dependent mechanism that induces inflammation in dMφs. In particular, DSC-derived arachidonic acid (AA) is internalized by dMφs via CD36, which activates cyclooxygenase 2-dependent prostaglandin E2 production and interleukin (IL)-1β expression. In mice, AA injection induces miscarriage, whereas conditional knockout of Cd36 in dMφs ameliorates AA-induced embryo loss. Additionally, DSC-derived prolactin (PRL) inhibits CD36-mediated lipid intake in dMφs, and PRL administration reduces embryo loss in pregnant mice treated with CD36+ Mφs. Our findings reveal a critical interplay between DSCs and dMφs in dysregulated lipid metabolism that may contribute to miscarriage, in which PRL may be harnessed as a therapeutic agent.

High concentration of estrogen resulted by COH may affect the secretion of pro-angiogenic factors in uNK cells by downregulating the expression of IL-11 in decidual stromal cells

OBJECTIVE

High serum estrogen concentrations after controlled ovarian hyperstimulation (COH) and fresh embryo transfers are associated with the increased risk of pregnancy complications resulting from aberrant placentation. Uterine natural killer (uNK) cells are important for establishment of pregnancy and normal placentation. It has been found that the proliferation and function of uNK cells are compromised by COH. However, the underlying role of high concentration of estrogen following COH in the abnormalities of uNK cells is poorly understood.

METHODS

Expression of cytokines and immunophenotype study of uNK was performed by flow cytometry analysis. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to quantify RNA expression; Western blot was performed to quantify protein levels.

RESULTS

The secretion level of pro-angiogenic factors in uNK cells is significantly reduced by co-culture with decidual stromal cells (DSCs) induced by high estrogen. It was discovered that COH and supraphysiologic levels of estrogen downregulated IL-11 in decidual tissue of mice. Additionally, we found that the downregulation of IL-11 is a major factor contributing to the downregulation of VEGF and PLGF in uNK cells. Moreover, we found that uNK cells may acquire IL-11Rα sequentially during differentiation and that only a portion of uNK cells are IL-11Rα positive. Lastly, we discovered that IL-11 may regulate VEGF and PLGF secretion in uNK cells via the ERK signaling pathway.

CONCLUSION

These results suggested the downregulation of IL-11 expression in DSCs caused by high estrogen levels affects the secretion of pro-angiogenic factors in uNK cells, which provided an explanation for the pregnancy complications caused by COH.

Single-cell transcriptomic analysis of immune cell dynamics in the healthy human endometrium

The microenvironment of the endometrial immune system is crucial to the success of placental implantation and healthy pregnancy. However, the functionalities of immune cells across various stages of the reproductive cycle have yet to be fully comprehended. To address this, we conducted advanced bioinformatic analysis on 230,049 high-quality single-cell transcriptomes from healthy endometrial samples obtained during the proliferative, secretory, early pregnancy, and late pregnancy stages. Our investigation has unveiled that proliferative natural killer (NK) cells, a potential source of endometrial NK cells, exhibit the most robust proliferative and differentiation potential during non-pregnant stages. We have also identified similar differentiation trajectories of NK cells originating from proliferative NK cells across four stages. Notably, during early pregnancy, NK cells demonstrate the highest oxidative phosphorylation metabolism activity, and, in conjunction with macrophages and T cells, exhibit the strongest type II interferon response. With spatial transcriptome data, we have discerned that the most robust immune-non-immune interactions are associated with the promotion and inhibition of cell proliferation, differentiation and migration during four stages. Furthermore, we have compiled lists of stage-specific risk genes implicated in reproductive diseases, which hold promise as potential disease biomarkers. Our study provides insights into the dynamics of the endometrial immune microenvironment during different reproductive cycle stages, thus serving as a reference for detecting pathological changes during pregnancy.

Spatial transcriptomics of fetal membrane-Decidual interface reveals unique contributions by cell types in term and preterm births

During pregnancy, two fetomaternal interfaces, the placenta-decidua basalis and the fetal membrane-decidua parietals, allow for fetal growth and maturation and fetal-maternal crosstalk, and protect the fetus from infectious and inflammatory signaling that could lead to adverse pregnancy outcomes. While the placenta has been studied extensively, the fetal membranes have been understudied, even though they play critical roles in pregnancy maintenance and the initiation of term or preterm parturition. Fetal membrane dysfunction has been associated with spontaneous preterm birth (PTB, < 37 weeks gestation) and preterm prelabor rupture of the membranes (PPROM), which is a disease of the fetal membranes. However, it is unknown how the individual layers of the fetal membrane decidual interface (the amnion epithelium [AEC], the amnion mesenchyme [AMC], the chorion [CTC], and the decidua [DEC]) contribute to these pregnancy outcomes. In this study, we used a single-cell transcriptomics approach to unravel the transcriptomics network at spatial levels to discern the contributions of each layer of the fetal membranes and the adjoining maternal decidua during the following conditions: scheduled caesarian section (term not in labor [TNIL]; n = 4), vaginal term in labor (TIL; n = 3), preterm labor with and without rupture of membranes (PPROM; n = 3; and PTB; n = 3). The data included 18,815 genes from 13 patients (including TIL, PTB, PPROM, and TNIL) expressed across the four layers. After quality control, there were 11,921 genes and 44 samples. The data were processed by two pipelines: one by hierarchical clustering the combined cases and the other to evaluate heterogeneity within the cases. Our visual analytical approach revealed spatially recognized differentially expressed genes that aligned with four gene clusters. Cluster 1 genes were present predominantly in DECs and Cluster 3 centered around CTC genes in all labor phenotypes. Cluster 2 genes were predominantly found in AECs in PPROM and PTB, while Cluster 4 contained AMC and CTC genes identified in term labor cases. We identified the top 10 differentially expressed genes and their connected pathways (kinase activation, NF-κB, inflammation, cytoskeletal remodeling, and hormone regulation) per cluster in each tissue layer. An in-depth understanding of the involvement of each system and cell layer may help provide targeted and tailored interventions to reduce the risk of PTB.

Immunologic insights in recurrent spontaneous abortion: Molecular mechanisms and therapeutic interventions

Recurrent spontaneous abortion refers to the occurrence of two or more spontaneous abortions before or during the early stages of pregnancy. The immune system plays a crucial role in the maintenance of pregnancy and embryo implantation. Various immune cells, cytokines, and immune regulatory pathways are involved in the complex immune balance required for a stable pregnancy. Studies suggest that immune abnormalities may be associated with some recurrent spontaneous abortion cases, particularly those involving the dysregulation of immune cell function, autoimmune responses, and placental immunity. In terms of treatment, interventions targeting immune mechanisms are crucial. Various therapeutic approaches, including immunomodulatory drugs, immunoadsorption therapies, and immunocellular therapies, are continually being researched and developed. These approaches aim to restore the immune balance, enhance the success rate of pregnancies, and provide more effective treatment options for patients with recurrent spontaneous abortion.

Deciphering decidual deficiencies in recurrent spontaneous abortion and the therapeutic potential of mesenchymal stem cells at single-cell resolution

BACKGROUND

Recurrent spontaneous abortion (RSA) is a challenging condition that affects the health of women both physically and mentally, but its pathogenesis and treatment have yet to be studied in detail. In recent years, Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) have been shown to be effective in treating various diseases. Current understanding of RSA treatment using WJ-MSCs is limited, and the exact mechanisms of WJ-MSCs action in RSA remains largely unclear. In this study, we explored the decidual deficiencies in RSA and the therapeutic potential of WJ-MSCs at single-cell resolution.

METHODS

Three mouse models were established: a normal pregnancy group, an RSA group, and a WJ-MSC treatment group. Decidual tissue samples were collected for single-cell RNA sequencing (scRNA-seq) and functional verification, including single-cell resolution in situ hybridization on tissues (SCRINSHOT) and immunofluorescence.

RESULTS

We generated a single-cell atlas of decidual tissues from normal pregnant, RSA, and WJ-MSC-treated mice and identified 14 cell clusters in the decidua on day 14. Among these cell populations, stromal cells were the most abundant cell clusters in the decidua, and we further identified three novel subclusters (Str_0, Str_1, and Str_2). We also demonstrated that the IL17 and TNF signaling pathways were enriched for upregulated DEGs of stromal cells in RSA mice. Intriguingly, cell-cell communication analysis revealed that Str_1 cell-related gene expression was greatly reduced in the RSA group and rescued in the WJ-MSC treatment group. Notably, the interaction between NK cells and other cells in the RSA group was attenuated, and the expression of Spp1 (identified as an endometrial toleration-related marker) was significantly reduced in the NK cells of the RSA group but could be restored by WJ-MSC treatment.

CONCLUSION

Herein, we implemented scRNA-seq to systematically evaluate the cellular heterogeneity and transcriptional regulatory networks associated with RSA and its treatment with WJ-MSCs. These data revealed potential therapeutic targets of WJ-MSCs to remodel the decidual subpopulations in RSA and provided new insights into decidua-derived developmental defects at the maternal-foetal interface.

Interleukin-10: a novel metabolic inducer of macrophage differentiation and subsequently contributing to improved pregnancy outcomes of mice by orchestrating oxidative phosphorylation metabolism†

Metabolism regulates the phenotype and function of macrophages. After recruitment to local tissues, monocytes are influenced by the local microenvironment and differentiate into various macrophages depending on different metabolic pathways. However, the metabolic mechanisms underlying decidual macrophage differentiation remain unknown. Interleukin-10 (IL-10) is an important decidual macrophage inducer and promotes oxidative phosphorylation (OXPHOS) of bone marrow-derived macrophages. In this study, we mainly investigate the metabolic changes involved in IL-10-generated macrophages from monocytes using in vitro models. We demonstrate that exposure of monocytes (either peripheral or THP-1) to IL-10 altered the phenotype and function of resultant macrophages that are linked with OXPHOS changes. Interleukin-10 enhanced the mitochondrial complex I and III activity of THP-1 cell-differentiated macrophages and increased the mitochondrial membrane potential, intracellular adenosine triphosphate, and reactive oxygen species levels. Oxidative phosphorylation blockage with oligomycin changed the cell morphology of IL-10-generated macrophages and the expression levels of cytokines, such as transforming growth factor beta, tumor necrosis factor-alpha, interferon gamma, and IL-10, apart from changes in the expression level of the surface markers CD206, CD209, and CD163. Moreover, in vivo IL-10 administration reduced the lipopolysaccharide (LPS)-induced embryo resorption rate, and this effect was diminished when OXPHOS was inhibited, demonstrating that OXPHOS is important for the improved pregnancy outcomes of IL-10 in LPS-induced abortion-prone mice. Our findings provide deep insights into the roles of IL-10 in macrophage biology and pregnancy maintenance. Nevertheless, the direct evidence that OXPHOS is involved in decidual macrophage differentiation needs further investigations.

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.

Human CD56+CD39+ dNK cells support fetal survival through controlling trophoblastic cell fate: immune mechanisms of recurrent early pregnancy loss

Decidual natural killer (dNK) cells are the most abundant immune cells at the maternal-fetal interface during early pregnancy in both mice and humans, and emerging single-cell transcriptomic studies have uncovered various human dNK subsets that are disrupted in patients experiencing recurrent early pregnancy loss (RPL) at early gestational stage, suggesting a connection between abnormal proportions or characteristics of dNK subsets and RPL pathogenesis. However, the functional mechanisms underlying this association remain unclear. Here, we established a mouse model by adoptively transferring human dNK cells into pregnant NOG (NOD/Shi-scid/IL-2Rγnull) mice, where human dNK cells predominantly homed into the uteri of recipients. Using this model, we observed a strong correlation between the properties of human dNK cells and pregnancy outcome. The transfer of dNK cells from RPL patients (dNK-RPL) remarkably worsened early pregnancy loss and impaired placental trophoblast cell differentiation in the recipients. These adverse effects were effectively reversed by transferring CD56+CD39+ dNK cells. Mechanistic studies revealed that CD56+CD39+ dNK subset facilitates early differentiation of mouse trophoblast stem cells (mTSCs) towards both invasive and syncytial pathways through secreting macrophage colony-stimulating factor (M-CSF). Administration of recombinant M-CSF to NOG mice transferred with dNK-RPL efficiently rescued the exacerbated pregnancy outcomes and fetal/placental development. Collectively, this study established a novel humanized mouse model featuring functional human dNK cells homing into the uteri of recipients and uncovered the pivotal role of M-CSF in fetal-supporting function of CD56+CD39+ dNK cells during early pregnancy, highlighting that M-CSF may be a previously unappreciated therapeutic target for intervening RPL.

Decrease in peripheral natural killer cell level during early pregnancy predicts live birth among women with unexplained recurrent pregnancy loss: a prospective cohort study

BACKGROUND

Previous studies have suggested that trophoblast cells inhibit the proliferation of peripheral natural killer cells and that the level of peripheral natural killer cells decrease in the middle and late pregnancy stage among healthy women. The change in peripheral natural killer cell level during early pregnancy and the relationship between the change in peripheral natural killer cell level and pregnancy outcomes among women with unexplained recurrent pregnancy loss have not been sufficiently explored.

OBJECTIVE

This study aimed to characterize the level of prepregnancy peripheral natural killer cells in comparison with those in early pregnancy among women with unexplained recurrent pregnancy loss and to determine if the change in the level of peripheral natural killer cells from prepregnancy to early pregnancy can predict pregnancy outcomes.

STUDY DESIGN

In this prospective cohort study, 1758 women with recurrent pregnancy loss were recruited between January 2017 and December 2021 among whom 252 women with unexplained recurrent pregnancy loss had prepregnancy and early pregnancy (4-6 weeks gestation) peripheral natural killer cell measurements. These 252 women were divided into 2 groups, namely those with a lower gestational peripheral natural killer cell level (group 1) when compared with prepregnancy levels and those who did not (group 2). The respective outcomes of these groups in terms of live birth and pregnancy loss were comparatively analyzed using chi-square and Student's t tests. Candidate factors that could influence live birth were selected using the Akaike information criterion. The participates were then randomly divided into training and testing groups. A multivariable logistic regression analysis was performed and a nomogram was created to assess the possibility of live birth. The predictive accuracy was determined by the area under the receiver operating characteristic curve and validated by plotting the predicted probabilities and the observed probabilities. A Hosmer-Lemeshow test was used to assess the goodness of fit.

RESULTS

When early gestational peripheral natural killer cell levels were compared with prepregnancy peripheral natural killer cell levels, 61.5% (154) of women had a comparatively lower early-gestational peripheral natural killer cell level and 38.9% (98) of women had an increase or no change in the peripheral natural killer cell level. The live birth rate in group 1 was 89.0% (137/154), which was significantly higher than the rate of 49.0% (48/98) in group 2 (P<.001). A decrease in the peripheral natural killer cell level (odds ratio, 1.36; 95% confidence interval, 1.22-1.55; P<.001) and the anti-Muellerian hormone level (odds ratio, 1.41; 95% confidence interval, 1.14-1.81; P=.003) were important predicting factors for a higher live birth rate. Female body mass index (odds ratio, 0.97; 95% confidence interval, 0.82-1.15; P=.763) and parity (odds ratio, 1.61; 95% confidence interval, 0.71-4.12; P=.287) also were predicting factors. Furthermore, the area under the receiver operating characteristic curve of the model to diagnose of live birth was 0.853 with a sensitivity of 81.6% and a specificity of 78.0% using the training data set. And the Hosmer-Lemeshow test showed that the model was a good fit (p=6.068).

CONCLUSION

We report a comparative decrease in the peripheral natural killer cell levels in early gestation when compared with prepregnancy cell levels in more than 60% of women with unexplained recurrent pregnancy loss at 4 to 6 weeks of gestation. When compared with prepregnancy peripheral natural killer cell levels, a decrease in the peripheral natural killer cell level during early pregnancy might be a useful predictor of the live birth rate among women with unexplained recurrent pregnancy loss.

Immune rebalancing at the maternal-fetal interface of maternal SARS-CoV-2 infection during early pregnancy

The current coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2) remains a threat to pregnant women. However, the impact of early pregnancy SARS-CoV-2 infection on the maternal-fetal interface remains poorly understood. Here, we present a comprehensive analysis of single-cell transcriptomics and metabolomics in placental samples infected with SARS-CoV-2 during early pregnancy. Compared to control placentas, SARS-CoV-2 infection elicited immune responses at the maternal-fetal interface and induced metabolic alterations in amino acid and phospholipid profiles during the initial weeks post-infection. However, subsequent immune cell activation and heightened immune tolerance in trophoblast cells established a novel dynamic equilibrium that mitigated the impact on the maternal-fetal interface. Notably, the immune response and metabolic alterations at the maternal-fetal interface exhibited a gradual decline during the second trimester. Our study underscores the adaptive immune tolerance mechanisms and establishment of immunological balance during the first two trimesters following maternal SARS-CoV-2 infection.

A Galectin-9-Driven CD11chigh Decidual Macrophage Subset Suppresses Uterine Vascular Remodeling in Preeclampsia

BACKGROUND

Preeclampsia is a serious disease of pregnancy that lacks early diagnosis methods or effective treatment, except delivery. Dysregulated uterine immune cells and spiral arteries are implicated in preeclampsia, but the mechanistic link remains unclear.

METHODS

Single-cell RNA sequencing and spatial transcriptomics were used to identify immune cell subsets associated with preeclampsia. Cell-based studies and animal models including conditional knockout mice and a new preeclampsia mouse model induced by recombinant mouse galectin-9 were applied to validate the pathogenic role of a CD11chigh subpopulation of decidual macrophages (dMφ) and to determine its underlying regulatory mechanisms in preeclampsia. A retrospective preeclampsia cohort study was performed to determine the value of circulating galectin-9 in predicting preeclampsia.

RESULTS

We discovered a distinct CD11chigh dMφ subset that inhibits spiral artery remodeling in preeclampsia. The proinflammatory CD11chigh dMφ exhibits perivascular enrichment in the decidua from patients with preeclampsia. We also showed that trophoblast-derived galectin-9 activates CD11chigh dMφ by means of CD44 binding to suppress spiral artery remodeling. In 3 independent preeclampsia mouse models, placental and plasma galectin-9 levels were elevated. Galectin-9 administration in mice induces preeclampsia-like phenotypes with increased CD11chigh dMφ and defective spiral arteries, whereas galectin-9 blockade or macrophage-specific CD44 deletion prevents such phenotypes. In pregnant women, increased circulating galectin-9 levels in the first trimester and at 16 to 20 gestational weeks can predict subsequent preeclampsia onset.

CONCLUSIONS

These findings highlight a key role of a distinct perivascular inflammatory CD11chigh dMφ subpopulation in the pathogenesis of preeclampsia. CD11chigh dMφ activated by increased galectin-9 from trophoblasts suppresses uterine spiral artery remodeling, contributing to preeclampsia. Increased circulating galectin-9 may be a biomarker for preeclampsia prediction and intervention.

Reconstructing developmental trajectories using latent dynamical systems and time-resolved transcriptomics

The snapshot nature of single-cell transcriptomics presents a challenge for studying the dynamics of cell fate decisions. Metabolic labeling and splicing can provide temporal information at single-cell level, but current methods have limitations. Here, we present a framework that overcomes these limitations: experimentally, we developed sci-FATE2, an optimized method for metabolic labeling with increased data quality, which we used to profile 45,000 embryonic stem (ES) cells differentiating into neural tube identities. Computationally, we developed a two-stage framework for dynamical modeling: VelvetVAE, a variational autoencoder (VAE) for velocity inference that outperforms all other tools tested, and VelvetSDE, a neural stochastic differential equation (nSDE) framework for simulating trajectory distributions. These recapitulate underlying dataset distributions and capture features such as decision boundaries between alternative fates and fate-specific gene expression. These methods recast single-cell analyses from descriptions of observed data to models of the dynamics that generated them, providing a framework for investigating developmental fate decisions.

Genome Editing of Plant Mitochondrial and Chloroplast Genomes

Plastids (including chloroplasts) and mitochondria are remnants of endosymbiotic bacteria, yet they maintain their own genomes, which encode vital components for photosynthesis and respiration, respectively. Organellar genomes have distinctive features, such as being present as multicopies, being mostly inherited maternally, having characteristic genomic structures and undergoing frequent homologous recombination. To date, it has proven to be challenging to modify these genomes. For example, while CRISPR/Cas9 is a widely used system for editing nuclear genes, it has not yet been successfully applied to organellar genomes. Recently, however, precise gene-editing technologies have been successfully applied to organellar genomes. Protein-based enzymes, especially transcription activator-like effector nucleases (TALENs) and artificial enzymes utilizing DNA-binding domains of TALENs (TALEs), have been successfully used to modify these genomes by harnessing organellar-targeting signals. This short review introduces and discusses the use of targeted nucleases and base editors in organellar genomes, their effects and their potential applications in plant science and breeding.

Single-cell transcriptomic analysis of decidual immune cell landscape in the occurrence of adverse pregnancy outcomes induced by Toxoplasma gondii infection

BACKGROUND

Toxoplasma gondii is an obligate intracellular parasite that can lead to adverse pregnancy outcomes, particularly in early pregnancy. Previous studies have illustrated the landscape of decidual immune cells. However, the landscape of decidual immune cells in the maternal-fetal microenvironment during T. gondii infection remains unknown.

METHODS

In this study, we employed single-cell RNA sequencing to analyze the changes in human decidual immune cells following T. gondii infection. The results of scRNA-seq were further validated with flow cytometry, reverse transcription-polymerase chain reaction, western blot, and immunofluorescence staining.

RESULTS

Our results showed that the proportion of 17 decidual immune cell clusters and the expression levels of 21 genes were changed after T. gondii infection. Differential gene analysis demonstrated that T. gondii infection induced the differential expression of 279, 312, and 380 genes in decidual NK cells (dNK), decidual macrophages (dMφ), and decidual T cells (dT), respectively. Our results revealed for the first time that several previously unknown molecules in decidual immune cells changed following infection. This result revealed that the function of maternal-fetal immune tolerance declined, whereas the killing ability of decidual immune cells enhanced, eventually contributing to the occurrence of adverse pregnancy outcomes.

CONCLUSIONS

This study provides valuable resource for uncovering several novel molecules that play an important role in the occurrence of abnormal pregnancy outcomes induced by T. gondii infection.

Maternal-fetal immunity and recurrent spontaneous abortion

Recurrent Spontaneous Abortion (RSA) is a common pregnancy complication, that has multifactorial causes, and currently, 40%-50% of cases remain unexplained, referred to as Unexplained RSA (URSA). Due to the elusive etiology and mechanisms, clinical management is exceedingly challenging. In recent years, with the progress in reproductive immunology, a growing body of evidence suggests a relationship between URSA and maternal-fetal immunology, offering hope for the development of tailored treatment strategies. This article provides an immunological perspective on the pathogenesis, diagnosis, and treatment of RSA. On one hand, it comprehensively reviews the immunological mechanisms underlying RSA, including abnormalities in maternal-fetal interface immune tolerance, maternal-fetal interface immune cell function, gut microbiota-mediated immune dysregulation, and vaginal microbiota-mediated immune anomalies. On the other hand, it presents the diagnosis and existing treatment modalities for RSA. This article offers a clear knowledge framework for understanding RSA from an immunological standpoint. In conclusion, while the "layers of the veil" regarding immunological factors in RSA are gradually being unveiled, our current research may only scratch the surface. In terms of immunological etiology, effective diagnostic tools for RSA are currently lacking, and the efficacy and safety of immunotherapies, primarily based on lymphocyte immunotherapy and intravenous immunoglobulin, remain contentious.

Increased levels of villus-derived exosomal miR-29a-3p in normal pregnancy than uRPL patients suppresses decidual NK cell production of interferon-γ and exerts a therapeutic effect in abortion-prone mice

OBJECTIVE

Recurrent pregnancy loss (RPL) patients have higher absolute numbers of decidual natural killer (dNK) cells with elevated intracellular IFN-γ levels leading to a pro-inflammatory cytokine milieu, which contributes to RPL pathogenesis. The main objective of this study was twofold: first to explore the regulatory effects and mechanisms of villus-derived exosomes (vEXOs) from induced abortion patients or RPL patients at the level of intracellular IFN-γ in dNK cells; second to determine the validity of application of vEXOs in the treatment of unexplained RPL (uRPL) through in vitro experiments and mouse models.

METHODS

Exosomes were isolated from villus explants by ultracentrifugation, co-cultured with dNK cells, and purified by enzymatic digestion and magnetically activated cell sorting. Flow cytometry, enzyme-linked immunosorbent assays, and RT-qPCR were used to determine IFN-γ levels. Comparative miRNA analysis of vEXOs from induced abortion (IA) and uRPL patients was used to screen potential candidates involved in dNK regulation, which was further confirmed by luciferase reporter assays. IA-vEXOs were electroporated with therapeutic miRNAs and encapsulated in a China Food and Drug Administration (CFDA)-approved hyaluronate gel (HA-Gel), which has been used as a clinical biomaterial in cell therapy for > 30 years. In vivo tracking was performed using 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyaine iodide (DiR) labelling. Tail-vein and uterine horn injections were used to evaluate therapeutic effects of the engineered exosomes in an abortion-prone mouse model (CBA/J × DBA/2 J). Placental growth was evaluated based on placental weight. IFN-γ mRNA levels in mouse placentas were measured by RT-qPCR.

RESULTS

IFN-γ levels were significantly higher in dNK cells of uRPL patients than in IA patients. Both uRPL-vEXOs and IA-vEXOs could be efficiently internalized by dNK cells, whereas uRPL-vEXOs could not reduce the expression of IFN-γ by dNK cells as much as IA-vEXOs. Mechanistically, miR-29a-3p was delivered by vEXOs to inhibit IFN-γ production by binding to the 3' UTR of IFN-γ mRNA in dNK cells. For in vivo treatment, application of the HA-Gel effectively prolonged the residence time of vEXOs in the uterine cavity via sustained release. Engineered vEXOs loaded with miR-29a-3p reduced the embryo resorption rate in RPL mice with no signs of systemic toxicity.

CONCLUSION

Our study provides the first evidence that villi can regulate dNK cell production of IFN-γ via exosome-mediated transfer of miR-29a-3p, which deepens our understanding of maternal-fetal immune tolerance for pregnancy maintenance. Based on this, we developed a new strategy to mix engineered vEXOs with HA-Gel, which exhibited good therapeutic effects in mice with uRPL and could be used for potential clinical applications in uRPL treatment.

Single-cell transcriptome analyses reveal disturbed decidual homoeostasis in obstetric antiphospholipid syndrome

OBJECTIVES

Obstetric antiphospholipid syndrome (OAPS) is an autoimmune disease characterised by the presence of antiphospholipid antibodies in circulation and pathological pregnancy. However, the pathogenesis of OAPS remains unknown. We aimed to reveal cellular compositions and molecular features of decidual cells involved in the development of OAPS using single-cell RNA sequencing (scRNA-seq).

METHODS

We performed unbiased scRNA-seq analysis on the first-trimester decidua from five OAPS patients and five healthy controls (HCs), followed by validations with flow cytometry, immunohistochemical staining and immunofluorescence in a larger cohort. Serum chemokines and cytokines were measured by using ELISA.

RESULTS

A higher ratio of macrophages but a lower ratio of decidual natural killer (dNK) cells was found in decidua from OAPS compared with HCs. Vascular endothelial cells shrinked in OAPS decidua while having upregulated chemokine expression and conspicuous responses to IFN-γ and TNF-α. Macrophages in OAPS had stronger phagocytosis function, complement activation signals and relied more on glycolysis. dNK cells were more activated in OAPS and had enhanced cytotoxicity and IFN-γ production. Downregulation of granules in OAPS dNK cells could be associated with suppressed glycolysis. Moreover, stromal cells had a prosenescent state with weakened immune surveillance for senescent cells in OAPS. In addition, the cellular interactions between decidual immune cells and those of immune cells with non-immune cells under disease state were altered, especially through chemokines, IFN-γ and TNF-α.

CONCLUSION

This study provided a comprehensive decidual cell landscape and identified aberrant decidual microenvironment in OAPS, providing some potential therapeutic targets for this disease.

The ubiquitin codes in cellular stress responses

Ubiquitination/ubiquitylation, one of the most fundamental post-translational modifications, regulates almost every critical cellular process in eukaryotes. Emerging evidence has shown that essential components of numerous biological processes undergo ubiquitination in mammalian cells upon exposure to diverse stresses, from exogenous factors to cellular reactions, causing a dazzling variety of functional consequences. Various forms of ubiquitin signals generated by ubiquitylation events in specific milieus, known as ubiquitin codes, constitute an intrinsic part of myriad cellular stress responses. These ubiquitination events, leading to proteolytic turnover of the substrates or just switch in functionality, initiate, regulate, or supervise multiple cellular stress-associated responses, supporting adaptation, homeostasis recovery, and survival of the stressed cells. In this review, we attempted to summarize the crucial roles of ubiquitination in response to different environmental and intracellular stresses, while discussing how stresses modulate the ubiquitin system. This review also updates the most recent advances in understanding ubiquitination machinery as well as different stress responses and discusses some important questions that may warrant future investigation.

scGIST: gene panel design for spatial transcriptomics with prioritized gene sets

A critical challenge of single-cell spatial transcriptomics (sc-ST) technologies is their panel size. Being based on fluorescence in situ hybridization, they are typically limited to panels of about a thousand genes. This constrains researchers to build panels from only the marker genes of different cell types and forgo other genes of interest, e.g., genes encoding ligand-receptor complexes or those in specific pathways. We propose scGIST, a constrained feature selection tool that designs sc-ST panels prioritizing user-specified genes without compromising cell type detection accuracy. We demonstrate scGIST's efficacy in diverse use cases, highlighting it as a valuable addition to sc-ST's algorithmic toolbox.

Aberrant NK cell profile in gestational diabetes mellitus with fetal growth restriction

Gestational diabetes mellitus (GDM) is a gestational disorder characterized by hyperglycemia, that can lead to dysfunction of diverse cells in the body, especially the immune cells. It has been reported that immune cells, specifically natural killer (NK) cells, play a crucial role in normal pregnancy. However, it remains unknown how hyperglycemia affects NK cell dysfunction thus participates in the development of GDM. In this experiment, GDM mice were induced by an intraperitoneal injection of streptozotocin (STZ) after pregnancy and it has been found that the intrauterine growth restriction occurred in mice with STZ-induced GDM, accompanied by the changed proportion and function of NK cells. The percentage of cytotoxic CD27-CD11b+ NK cells was significantly increased, while the proportion of nourished CD27-CD11b- NK cells was significantly reduced in the decidua of GDM mice. Likewise, the same trend appeared in the peripheral blood NK cell subsets of GDM patients. What's more, after intrauterine reinfusion of NK cells to GDM mice, the fetal growth restriction was alleviated and the proportion of NK cells was restored. Our findings provide a theoretical and experimental basis for further exploring the pathogenesis of GDM.

Macrophage plasticity and function in cancer and pregnancy

As the soil of life, the composition and shaping process of the immune microenvironment of the uterus is worth exploring. Macrophages, indispensable constituents of the innate immune system, are essential mediators of inflammation and tissue remodeling as well. Recent insights into the heterogeneity of macrophage subpopulations have renewed interest in their functional diversity in both physiological and pathological settings. Macrophages display remarkable plasticity and switch from one phenotype to another. Intrinsic plasticity enables tissue macrophages to perform a variety of functions in response to changing tissue contexts, such as cancer and pregnancy. The remarkable diversity and plasticity make macrophages particularly intriguing cells given their dichotomous role in either attacking or protecting tumors and semi-allogeneic fetuses, which of both are characterized functionally by immunomodulation and neovascularization. Here, we reviewed and compared novel perspectives on macrophage biology of these two settings, including origin, phenotype, differentiation, and essential roles in corresponding microenvironments, as informed by recent studies on the heterogeneity of macrophage identity and function, as well as their mechanisms that might offer opportunities for new therapeutic strategies on malignancy and pregnancy complications.

Endometrial protein expression and phosphorylation landscape decipher aberrant insulin and mTOR signalling in patients with recurrent pregnancy loss

RESEARCH QUESTION

What are the proteomic and phosphoproteomic differences between the endometrium of women with recurrent pregnancy loss (RPL) and the endometrium of healthy control women during the proliferative and secretory phases of the menstrual cycle?

DESIGN

In total, 54 endometrial samples were collected during the proliferative and secretory phases from women with RPL (n = 28) and healthy controls (n = 26). Comprehensive proteomic and phosphoproteomic analyses were conducted using label-free liquid chromatography-tandem mass spectrometry (n = 44), and verified through Western blotting (n = 10). Three comparison groups were established: total RPL endometrium versus total control endometrium; RPL proliferative endometrium versus control proliferative endometrium; and RPL secretory endometrium versus control secretory endometrium.

RESULTS

Differentially expressed proteins and differentially phosphorylated proteins were identified in the three comparison groups. Combining pathway enrichment, network analysis and soft clustering analysis, the insulin/cyclic nucleotide signalling pathway and AMPK/mTOR signalling pathway were identified as the major contributors to the aberration of RPL endometrium. Western blotting verified altered expression of four proteins: cAMP-dependent protein kinase type I-β regulatory subunit, adenylate cyclase type 3, 5'-AMP-activated protein kinase catalytic subunit α-2 and phosphatidate phosphatase LPIN2.

CONCLUSIONS

This exploratory study provides insights into the differentiated protein expression and phosphorylation profiles of the endometrium of women with RPL in both the proliferative and sectretory phases of the menstrual cycle. The results highlight potential proteins associated with the pathogenesis of RPL that may serve as potential indicators for RPL. The findings contribute to the identification of potential targets for RPL treatment as well as its pathogenesis.

Roles of immune microenvironment in the female reproductive maintenance and regulation: novel insights into the crosstalk of immune cells

Female fertility decline is an accumulative consequence caused by complex factors, among them, the disruption of the immune profile in female reproduction stands out as a crucial contributor. Presently, the effects of immune microenvironment (IME) on the female reproductive process have attracted increasing attentions for their dynamic but precisive roles. Immunocytes including macrophages, dendritic cells, T cells, B cells and neutrophils, with diverse subpopulations as well as high plasticity functioned dynamically in the process of female reproduction through indirect intercellular communication via specific cytokine release transduced by molecular signal networks or direct cell-cell contact to maintain the stability of the reproductive process have been unveiled. The immune profile of female reproduction in each stage has also been meticulously unveiled. Especially, the application of single-cell sequencing (scRNA-seq) technology in this process reveals the distribution map of immune cells, which gives a novel insight for the homeostasis of IME and provides a research direction for better exploring the role of immune cells in female reproduction. Here, we provide an all-encompassing overview of the latest advancements in immune modulation within the context of the female reproductive process. Our approach involves structuring our summary in accordance with the physiological sequence encompassing gonadogenesis, folliculogenesis within the ovaries, ovulation through the fallopian tubes, and the subsequent stages of embryo implantation and development within the uterus. Our overarching objective is to construct a comprehensive portrayal of the immune microenvironment (IME), thereby accentuating the pivotal role played by immune cells in governing the intricate female reproductive journey. Additionally, we emphasize the pressing need for heightened attention directed towards strategies that focus on immune interventions within the female reproductive process, with the ultimate aim of enhancing female fertility.

Metal-coding assisted serological multi-omics profiling deciphers the role of selenium in COVID-19 immunity

Uncovering how host metal(loid)s mediate the immune response against invading pathogens is critical for better understanding the pathogenesis mechanism of infectious disease. Clinical data show that imbalance of host metal(loid)s is closely associated with the severity and mortality of COVID-19. However, it remains elusive how metal(loid)s, which are essential elements for all forms of life and closely associated with multiple diseases if dysregulated, are involved in COVID-19 pathophysiology and immunopathology. Herein, we built up a metal-coding assisted multiplexed serological metallome and immunoproteome profiling system to characterize the links of metallome with COVID-19 pathogenesis and immunity. We found distinct metallome features in COVID-19 patients compared with non-infected control subjects, which may serve as a biomarker for disease diagnosis. Moreover, we generated the first correlation network between the host metallome and immunity mediators, and unbiasedly uncovered a strong association of selenium with interleukin-10 (IL-10). Supplementation of selenium to immune cells resulted in enhanced IL-10 expression in B cells and reduced induction of proinflammatory cytokines in B and CD4+ T cells. The selenium-enhanced IL-10 production in B cells was confirmed to be attributable to the activation of ERK and Akt pathways. We further validated our cellular data in SARS-CoV-2-infected K18-hACE2 mice, and found that selenium supplementation alleviated SARS-CoV-2-induced lung damage characterized by decreased alveolar inflammatory infiltrates through restoration of virus-repressed selenoproteins to alleviate oxidative stress. Our approach can be readily extended to other diseases to understand how the host defends against invading pathogens through regulation of metallome.

Proteomic profiling analysis of human endometrium in women with unexplained recurrent spontaneous abortion

Unexplained recurrent spontaneous abortion (URSA) seriously affects female reproductive health, causing a great burden to patients both physically and mentally. Endometrial decidualization plays an important role in pregnancy, and impaired decidualization is an essential cause of URSA, but the cause of the damage is still poorly understood. This study aimed to reveal the pathogenesis of URSA by analyzing the differential protein expression profiles in the decidual tissue of patients with recurrent abortion compared to those with normal pregnancy. Morphological analysis revealed abnormal decidualization of endometrial tissue in patients with URSA. Quantitative proteomics analysis showed that a total of 146 differentially expressed proteins were identified between the two groups, among which 95 proteins were downregulated and 51 proteins were upregulated. Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways revealed that the protein expression profile and signaling pathways of endometrium in patients with URSA changed significantly, and cytoskeleton remodeling and morphological transformation disorders were associated with abortion induced by incomplete decidualization. Meanwhile, transcription factors analysis showed that the 3 most affected families were zf-C2H2, MYB and HMG. Therefore, our study may provide a basis for searching for potential markers of decidualization injury. SIGNIFICANCE: At present, there are still about 50% of RSA patients with unknown causes, which brings great difficulties and blindness to clinical diagnosis and treatment.The limited proteomic studies on URSA further contribute to the lack of understanding in this field. However, in this study, the focus was on proteomic profiling analysis of the human endometrium in URSA patients compared to normal women. The findings revealed that cytoskeletal remodeling disorder is a significant contributor to the failure of decidualization in URSA patients. This insight highlights the potential role of cytoskeleton-related proteins in the pathogenesis of URSA, providing valuable information for further research and potential therapeutic interventions.

SARS-CoV-2 niches in human placenta revealed by spatial transcriptomics

BACKGROUND

Functional placental niches are presumed to spatially separate maternal-fetal antigens and restrict the vertical transmission of pathogens. We hypothesized a high-resolution map of placental transcription could provide direct evidence for niche microenvironments with unique functions and transcription profiles.

METHODS

We utilized Visium Spatial Transcriptomics paired with H&E staining to generate 17,927 spatial transcriptomes. By integrating these spatial transcriptomes with 273,944 placental single-cell and single-nuclei transcriptomes, we generated an atlas composed of at least 22 subpopulations in the maternal decidua, fetal chorionic villi, and chorioamniotic membranes.

FINDINGS

Comparisons of placentae from uninfected healthy controls (n = 4) with COVID-19 asymptomatic (n = 4) and symptomatic (n = 5) infected participants demonstrated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detection in syncytiotrophoblasts occurred in both the presence and the absence of maternal clinical disease. With spatial transcriptomics, we found that the limit of detection for SARS-CoV-2 was 1/7,000 cells, and placental niches without detectable viral transcripts were unperturbed. In contrast, niches with high SARS-CoV-2 transcript levels were associated with significant upregulation in pro-inflammatory cytokines and interferon-stimulated genes, altered metallopeptidase signaling (TIMP1), with coordinated shifts in macrophage polarization, histiocytic intervillositis, and perivillous fibrin deposition. Fetal sex differences in gene expression responses to SARS-CoV-2 were limited, with confirmed mapping limited to the maternal decidua in males.

CONCLUSIONS

High-resolution placental transcriptomics with spatial resolution revealed dynamic responses to SARS-CoV-2 in coordinate microenvironments in the absence and presence of clinically evident disease.

FUNDING

This work was supported by the NIH (R01HD091731 and T32-HD098069), NSF (2208903), the Burroughs Welcome Fund and the March of Dimes Preterm Birth Research Initiatives, and a Career Development Award from the American Society of Gene and Cell Therapy.

The function of decidua natural killer cells in physiology and pathology of pregnancy

The role of decidual natural killer (dNK) cells in maintaining immune tolerance at the maternal-fetal interface during pregnancy is a significant topic in reproductive health. Immune tolerance is essential for a successful pregnancy and involves a complex immune response involving various immune cells and molecules. DNK cells comprise the largest population of lymphocyte subsets found in the decidua and play important roles in maintaining immune tolerance. These cells exert multiple functions to maintain homeostasis of the decidual microenvironment, including modulation of trophoblast invasion, promotion of fetal development, regulation of endometrial decidualization and spiral artery remodeling. DNK cells can also be divided into different subsets based on their functions as NKtolerant , NKcytotoxic , and NKregulatory cells. However, the relationship between dNK cells function and pregnancy outcomes is complex and poorly understood. In this review, we will focus on the physiological role of dNK cells during pregnancy and highlight the potential role in pathological pregnancies and therapeutic approaches.

Characterization and development of a plastid genome base editor, ptpTALECD

The modification of photosynthesis-related genes in plastid genomes may improve crop yields. Recently, we reported that a plastid-targeting base editor named ptpTALECD, in which a cytidine deaminase DddA functions as the catalytic domain, can homoplasmically substitute a targeted C to T in plastid genomes of Arabidopsis thaliana. However, some target Cs were not substituted. In addition, although ptpTALECD could substitute Cs on the 3' side of T and A, it was unclear whether it could also substitute Cs on the 3' side of G and C. In this study, we identified the preferential positions of the substituted Cs in ptpTALECD-targeting sequences in the Arabidopsis plastid genome. We also found that ptpTALECD could substitute Cs on the 3' side of all four bases in plastid genomes of Arabidopsis. More recently, a base editor containing an improved version of DddA (DddA11) was reported to substitute Cs more efficiently, and to substitute Cs on the 3' side of more varieties of bases in human mitochondrial genomes than a base editor containing DddA. Here, we also show that ptpTALECD_v2, in which a modified version of DddA11 functions as the catalytic domain, more frequently substituted Cs than ptpTALECD in the Arabidopsis plastid genome. We also found that ptpTALECD_v2 tended to substitute Cs at more positions than ptpTALECD. Our results reveal that ptpTALECD can cause a greater variety of codon changes and amino acid substitutions than previously thought, and that ptpTALECD and ptpTALECD_v2 are useful tools for the targeted base editing of plastid genomes.

Crosstalk between Placental Trophoblast and Decidual Immune Cells in Recurrent Miscarriage

Recurrent miscarriage (RM) is a pregnancy complication associated with dysregulation of the maternal-fetal interface. We aimed to identify dysfunctional interactions between trophoblast cells and decidual immune cells in RM. We downloaded single-cell RNA sequencing (scRNA-seq) datasets (GSE214607) from the Gene Expression Omnibus (GEO) datasets for further analysis using the R software. The data comprised of paired placental and decidual tissues, including those from patients diagnosed with RM and matched healthy controls. A total of 22976 cells were identified in 11 cell types, including trophoblasts, immune cells, and other cells. We divided trophoblast cells into three types and analyzed their interactions with decidual immune cells. Additionally, we re-clustered NK&T cells and macrophages, identified differentially expressed genes (DEGs), enriched their functions, and compared the cell interactions with trophoblast cells in each cell type. Our single-cell atlas of the maternal-fetal interface revealed alterations in the cellular organization of the decidua and placenta, cell type-specific transcriptome, and cell communication between immune and non-immune cells in RM, which are critical for illuminating the pathophysiology of RM.

Autoimmune thyroid disease disrupts immune homeostasis in the endometrium of unexplained infertility women-a single-cell RNA transcriptome study during the implantation window

Objective

Autoimmune thyroid disease (AITD) is known to be associated with unexplained infertility in women. Although the presence of antithyroid antibodies have been speculated to be a marker of an immune imbalance that might lead to implantation failure, its underlying mechanism influencing the endometrial receptivity remains to be elucidated. In this study, we used single-cell RNA sequencing (scRNA-seq) to dissect immune microenvironment in endometrium of AITD patients during window of implantation (WOI).

Methods

We collected CD45⁺ immune cell populations of endometrium samples of unexplained infertile women with AITD (n=3), as well as samples of AITD^- controls (n=3). The cells were then processed with 10X Genomics Chromium for further analysis.

Results

We characterized 28 distinct immune cell subtypes totally, and uncovered differences in the composition and gene expression patterns between AITD patients and controls. The proportions of T CD4⁺, cNK, ILC3, T CD8⁺ GZMK⁺, T CD8⁺ Cytotoxic and ILC3 CD3E ^- cells were increased, and CD366⁺ uNK1 was decreased in AITD⁺ patients. And the abnormal expression of GNLY and chemokines was observed in AITD patients. In addition, uNK and T CD8⁺ Cytotoxic cells showed lower cytotoxicity but activation of immune response. Genes enriched in cell adhesion of ILC3 and Tregs were downregulated, while the number of ILC3 and Tregs were increased.

Conclusion

Immune imbalance exists in endometrium during WOI, which may impact embryo implantation.

The role of CD8+ T cells in endometriosis: a systematic review

Background

Endometriosis is a chronic disease affecting 6-10% of women of reproductive age. It is an important cause of infertility and chronic pelvic pain with poorly understood aetiology. CD8+ T (CD8 T) cells were shown to be linked to infertility and chronic pain and play a significant role in lesion clearance in other pathologies, yet their function in endometriosis is unknown. We systematically evaluated the literature on the CD8 T in peripheral blood and endometriosis-associated tissues to determine the current understanding of their pathophysiological and clinical relevance in the disease and associated conditions (e.g. infertility and pelvic pain).

Methods

Four databases were searched (MEDLINE, EMBASE, Web of Science, CINAHL), from database inception until September 2022, for papers written in the English language with database-specific relevant terms/free-text terms from two categories: CD8 T cells and endometriosis. We included peer-reviewed papers investigating CD8 T cells in peripheral blood and endometriosis-associated tissues of patients with surgically confirmed endometriosis between menarche and menopause, and animal models with oestrous cycles. Studies enrolling participants with other gynaecological pathologies (except uterine fibroids and tubal factor infertility used as controls), cancer, immune diseases, or taking immune or hormonal therapy were excluded.

Results

28 published case-control studies and gene set analyses investigating CD8 T cells in endometriosis were included. Data consistently indicate that CD8 T cells are enriched in endometriotic lesions in comparison to eutopic endometrium, with no differences in peripheral blood CD8 T populations between patients and healthy controls. Evidence on CD8 T cells in peritoneal fluid and eutopic endometrium is conflicting. CD8 T cell cytotoxicity was increased in the menstrual effluent of patients, and genomic analyses have shown a clear trend of enriched CD8 T effector memory cells in the eutopic endometrium of patients.

Conclusion

Literature on CD8 T cells in endometriosis-associated tissues is inconsistent. Increased CD8 T levels are found in endometriotic lesions, however, their activation potential is understudied in all relevant tissues. Future research should focus on identifying clinically relevant phenotypes to support the development of non-invasive diagnostic and treatment strategies.

Systematic Review Registration

PROSPERO identifier CRD42021233304.

Human embryo implantation

Embryo implantation in humans is interstitial, meaning the entire conceptus embeds in the endometrium before the placental trophoblast invades beyond the uterine mucosa into the underlying inner myometrium. Once implanted, embryo survival pivots on the transformation of the endometrium into an anti-inflammatory placental bed, termed decidua, under homeostatic control of uterine natural killer cells. Here, we examine the evolutionary context of embryo implantation and elaborate on uterine remodelling before and after conception in humans. We also discuss the interactions between the embryo and the decidualising endometrium that regulate interstitial implantation and determine embryo fitness. Together, this Review highlights the precarious but adaptable nature of the implantation process.

Morphology-guided transcriptomic analysis of human pancreatic cancer organoids reveals microenvironmental signals that enhance invasion

Pancreatic ductal adenocarcinoma (PDAC) frequently presents with metastasis, but the molecular programs in human PDAC cells that drive invasion are not well understood. Using an experimental pipeline enabling PDAC organoid isolation and collection based on invasive phenotype, we assessed the transcriptomic programs associated with invasion in our organoid model. We identified differentially expressed genes in invasive organoids compared with matched noninvasive organoids from the same patients, and we confirmed that the encoded proteins were enhanced in organoid invasive protrusions. We identified 3 distinct transcriptomic groups in invasive organoids, 2 of which correlated directly with the morphological invasion patterns and were characterized by distinct upregulated pathways. Leveraging publicly available single-cell RNA-sequencing data, we mapped our transcriptomic groups onto human PDAC tissue samples, highlighting differences in the tumor microenvironment between transcriptomic groups and suggesting that non-neoplastic cells in the tumor microenvironment can modulate tumor cell invasion. To further address this possibility, we performed computational ligand-receptor analysis and validated the impact of multiple ligands (TGF-β1, IL-6, CXCL12, MMP9) on invasion and gene expression in an independent cohort of fresh human PDAC organoids. Our results identify molecular programs driving morphologically defined invasion patterns and highlight the tumor microenvironment as a potential modulator of these programs.

Identifying a dynamic transcriptomic landscape of the cynomolgus macaque placenta during pregnancy at single-cell resolution

Supporting healthy pregnancy outcomes requires a comprehensive understanding of the cellular hierarchy and underlying molecular mechanisms in the primate placenta during gestation. Here, we present a single-cell transcriptome-wide view of the cynomolgus macaque placenta throughout gestation. Bioinformatics analyses and multiple validation experiments suggested that placental trophoblast cells exhibited stage-specific differences across gestation. Interactions between trophoblast cells and decidual cells also showed gestational stage-dependent differences. The trajectories of the villous core cells indicated that placental mesenchymal cells were derived from extraembryonic mesoderm (ExE.Meso) 1, whereas placental Hofbauer cells, erythrocytes, and endothelial cells were derived from ExE.Meso2. Comparative analyses of human and macaque placentas uncovered conserved features of placentation across species, and the discrepancies of extravillous trophoblast cells (EVTs) between human and macaque correlated to their differences in invasion patterns and maternal-fetal interactions. Our study provides a groundwork for elucidating the cellular basis of primate placentation.

Current Status and Prospects of the Single-Cell Sequencing Technologies for Revealing the Pathogenesis of Pregnancy-Associated Disorders

Single-cell RNA sequencing (scRNA-seq) is a method that focuses on the analysis of gene expression profile in individual cells. This method has been successfully applied to answer the challenging questions of the pathogenesis of multifactorial diseases and open up new possibilities in the prognosis and prevention of reproductive diseases. In this article, we have reviewed the application of scRNA-seq to the analysis of the various cell types and their gene expression changes in normal pregnancy and pregnancy complications. The main principle, advantages, and limitations of single-cell technologies and data analysis methods are described. We discuss the possibilities of using the scRNA-seq method for solving the fundamental and applied tasks related to various pregnancy-associated disorders. Finally, we provide an overview of the scRNA-seq findings for the common pregnancy-associated conditions, such as hyperglycemia in pregnancy, recurrent pregnancy loss, preterm labor, polycystic ovary syndrome, and pre-eclampsia.

The Mac Is Back: The Role of Macrophages in Human Healthy and Complicated Pregnancies

Pregnancy is a fascinating immunological paradox: the semi-allogeneic fetus generally grows without any complications. In the placenta, fetal trophoblast cells come into contact with maternal immune cells. Inaccurate or inadequate adaptations of the maternal immune system could lead to problems with the functioning of the placenta. Macrophages are important for tissue homeostasis, cleanup, and the repair of damaged tissues. This is crucial for a rapidly developing organ such as the placenta. The consensus on macrophages at the maternal-fetal interface in pregnancy is that a major proportion have an anti-inflammatory, M2-like phenotype, that expresses scavenger receptors and is involved in tissue remodeling and the dampening of the immune reactions. Recent multidimensional analyses have contributed to a more detailed outlook on macrophages. The new view is that this lineage represents a highly diverse phenotype and is more prevalent than previously thought. Spatial-temporal in situ analyses during gestation have identified unique interactions of macrophages both with trophoblasts and with T cells at different trimesters of pregnancy. Here, we elaborate on the role of macrophages during early human pregnancy and at later gestation. Their possible effect is reviewed in the context of HLA incompatibility between mother and fetus, first in naturally conceived pregnancies, but foremost in pregnancies after oocyte donation. The potential functional consequences of macrophages for pregnancy-related immune reactions and the outcome in patients with recurrent pregnancy loss are also discussed.

Single-cell profiling of the microenvironment in decidual tissue from women with missed abortions

OBJECTIVE

To define the decidual microenvironment in euploid and aneuploid missed abortions and elective termination of pregnancies.

DESIGN

Prospective, multicenter, observational study.

SETTING

Tertiary hospital and descriptive analysis of transcriptomic data.

PATIENT(S)

A total of 34 patients experienced abortions, including 6 women who underwent elective terminations of pregnancy of unplanned pregnancies and 28 cases with missed abortions. All patients underwent their operations from Sep, 2021 to Sep, 2022.

INTERVENTION(S)

All women underwent villous copy number variation sequencing. Meanwhile, single-cell RNA sequencing were performed in the decidual tissues of 16 women, and reverse transcription quantitative polymerase chain reaction were performed in the decidual tissues of 18 women.

MAIN OUTCOME MEASURE(S)

Single-cell RNA sequencing was used to explore the changes in the microenvironment of decidual tissues in abortions.

RESULT(S)

Single-cell RNA sequencing indicated that the microenvironment of the decidual tissue of the missed-abortion group was altered, and that the stromal cells (SCs), natural killer cells, macrophages, and epithelial cells all reflected functional imbalances compared with the elective terminations of pregnancy group. We also noted a correlation between the proportion of senescent SCs and chromosomal abnormalities in missed-abortion embryos. The proportion of senescent decidual SCs in the decidual tissue of missed-abortion patients with common chromosomal abnormalities of the fetus was higher, and this was not conducive to fetal growth and was closely related to missed abortion. In addition, we ascertained that the strength of the HLA-KIR interaction between NK1 and NK2 subsets and non-senescent stromal cell subsets in the missed abortion decidual tissues was weakened, potentially playing a role in the occurrence of missed abortion.

CONCLUSION(S)

The decidualization of SCs in the missed-abortion decidual tissues was impaired, the clearance of senescent SCs by NK cells was weakened, the killing toxicity of non-senescent SCs was enhanced, macrophages were insufficiently resident at the maternal-fetal interface, and epithelial cell differentiation was unbalanced-all creating a maternal microenvironment that was not conducive to fetal growth. We posit that interfering with the expression of dysregulated genes in the missed-abortion decidual tissues and reversing the maternal microenvironment might constitute an effective means toward improving the clinical outcome of missed abortions. Intriguingly, we observed a correlation between stromal cell senescence and embryonic chromosomal abnormalities. Thus, we hypothesize that the DIO2 marker of senescent SCs can be used as a risk indicator for the occurrence of missed miscarriages with chromosomal abnormalities of the embryos, and that it can be applied to guide the clinical diagnosis and treatment of recurrent abortion.

CLINICAL TRIAL REGISTRATION NUMBER

NCT04425317.

HSP70 regulates lipid metabolism of decidual macrophages to maintain normal pregnancy

Dysfunction of decidual macrophages (dMs) are closely associated with recurrent pregnancy loss (RPL) which brings great suffering to patients. Metabolism is essential for regulating macrophage function. Identifying molecules that regulate metabolism and function of dMs is important to revealing the pathogenesis of RPL. Single-cell sequencing data of decidual immune cells from control and RPL patients were downloaded from the GSA database and converted into feature-barcode matrices by Cell Ranger. After quality control, removal of double cell and clustering of all cells, 3579 macrophages were extracted for normalisation, scaling and re-clustering. Function and metabolism analyses were performed by R packages AddMoudleScore, scMetabolism and AUCell. Metabolism clustering based on metabolism-related genes to clarify the metabolic characteristics of macrophages clusters. These results indicated that macrophage characterised by lipid metabolism were reduced in RPL and differential expression genes analysis found that HSP70 was significantly decreased in the RPL group. Furthermore, immunofluorescence staining demonstrated that HSP70 was significantly downregulated in dMs of RPL patients compared to controls. In conclusion, HSP70 may maintain normal pregnancy by regulating lipid metabolism of dMs. This study provides new insights into the molecular mechanisms regulating the function of dMs and provides a theoretical basis for the development of new therapies for RPL.

Bioinformatics Analysis Identifies Key Genes in Recurrent Implantation Failure Based on Immune Infiltration

Recurrent implantation failure (RIF) is a thorny problem often encountered in the field of assisted reproduction. Existing evidences suggest that immune dysregulation may be involved in the pathogenesis of RIF. The purpose of this study is to explore immune-related genes contributing to RIF through data mining. The endometrial expression profiles of 24 RIF and 24 controls were obtained from the GEO database. The immune infiltration in bulk tissue was estimated by single sample gene set enrichment analysis (ssGSEA) method based on marker gene sets for immune cells generated from endometrial single-cell RNA sequencing data. The results showed that the infiltration levels of B cells and regulatory T cells (Tregs) were significantly reduced in the RIF group. Four hub genes (GJA1, PRKAG2, CPT1A, and ICA1) were identified by integrated analysis of weighted gene co-expression network analysis (WGCNA), random forest and LASSO regression. Moreover, these hub genes were significantly correlated with certain immune-related factors, especially CXCL12, CEACAM1, and XCR1. Single-gene GSEA indicated that the pathways associated with hub genes included the regulation of cell cycle, the process of epithelial-mesenchymal transition and transplant rejection, etc. A predictive model for RIF was constructed based on hub genes and performed well in the training dataset and the other two external datasets. Thus, this study identified immune-related key genes in RIF and provided new biomarkers for early diagnosis.

Uterine NK cells underexpress KIR2DL1/S1 and LILRB1 in reproductive failure

A significant proportion of recurrent miscarriage, recurrent implantation failure and infertility are unexplained, and these conditions have been proposed to have an etiology of immunological dysfunction at the maternal-fetal interface. Uterine Natural Killer cells (uNK) comprise three subsets and are the most numerous immune cells found in the uterine mucosa at the time of implantation. They are thought to play an important role in successful pregnancy by regulation of extravillous trophoblast (EVT) invasion and spiral artery remodelling. Here, we examine the frequency, phenotype and function of uNK1-3 from the uterine mucosa of 16 women with unexplained reproductive failure compared to 11 controls with no reproductive problems, during the window of implantation. We report that KIR2DL1/S1 and LILRB1 expression is lower in the reproductive failure group for both uNK (total uNK, uNK 2 and 3) and pNK. We also show that degranulation activity is significantly reduced in total uNK, and that TNF-α production is lower in all uNK subsets in the reproductive failure group. Taken together, our findings suggest that reproductive failure is associated with global reduction in expression of uNK receptors important for interaction with HLA-C and HLA-G on EVT during early pregnancy, leading to reduced uNK activation. This is the first study to examine uNK subsets during the window of implantation in women with reproductive failure and will serve as a platform to focus on particular aspects of phenotype and function of uNK subsets in future studies. Further understanding of uNK dysregulation is important to establish potential diagnostic and therapeutic targets in the population of women with unexplained reproductive failure.

Single cell RNA sequencing research in maternal fetal interface

The maternal-fetal interface is an essential environment for embryonic growth and development, and a successful pregnancy depends on the dynamic balance of the microenvironment at the maternal-fetal interface. Single-cell sequencing, which unlike bulk sequencing that provides averaged data, is a robust method for interpreting the cellular and molecular landscape at single-cell resolution. With the support of single-cell sequencing, the issue of maternal-fetal interface heterogeneity during pregnancy has been more deeply elaborated and understood, which is important for a deeper understanding of physiological and pathological pregnancy. In this paper, we analyze the recent studies of single-cell transcriptomics in the maternal-fetal interface, and provide new directions for understanding and treating various pathological pregnancies.

Single-cell profiling reveals mechanisms of uncontrolled inflammation and glycolysis in decidual stromal cell subtypes in recurrent miscarriage

STUDY QUESTION

Do distinct subpopulations of decidual stromal cells (DSCs) exist and if so, are given subpopulations enriched in recurrent miscarriage (RM)?

SUMMARY ANSWER

Three subpopulations of DSCs were identified from which inflammatory DSCs (iDSCs) and glycolytic DSCs (glyDSCs) are significantly enriched in RM, with implicated roles in driving decidual inflammation and immune dysregulation.

WHAT IS KNOWN ALREADY

DSCs play crucial roles in establishing and maintaining a successful pregnancy; dysfunction of DSCs has been considered as one of the key reasons for the development of RM.

STUDY DESIGN, SIZE, DURATION

We collected 15 early decidual samples from five healthy donors (HDs) and ten RM patients to perform single-cell RNA sequencing (scRNA-seq). A total of 43 RM patients and 37 HDs were enrolled in the validation cohort.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Non-immune cells and immune cells of decidual tissues were sorted by flow cytometry to perform scRNA-seq. We used tissue microarrays (TMA) to validate three distinct subpopulations of DSCs. The expression of inflammatory and glycolytic proteins by DSCs was validated by immunohistochemistry (IHC) and multiplex immunohistochemistry (mIHC). Different subsets of decidual NK (dNK) cells and macrophages were also validated by multicolor flow cytometry and mIHC. Cell ligand-receptor and spatial analyses between DSCs and immune cells were analyzed by mIHC.

MAIN RESULTS AND THE ROLE OF CHANCE

We classify the DSCs into three subtypes based on scRNA-seq data: myofibroblastic (myDSCs), inflammatory (iDSCs) and glycolytic (glyDSCs), with the latter two being significantly enriched in RM patients. The distribution patterns of DSC subtypes in the RM and HD groups were validated by mIHC. Single-cell analyses indicate that the differentiation of iDSCs and glyDSCs may be coupled with the degrees of hypoxia. Consequently, we propose a pathological model in which a vicious circle is formed and fueled by hypoxic stress, uncontrolled inflammation and aberrant glycolysis. Furthermore, our results show that the inflammatory SPP1+ macrophages and CD18+ dNK cells are preferentially increased in the decidua of RM patients. Cell ligand-receptor and mIHC spatial analyses uncovered close interactions between pathogenic DSCs and inflammatory SPP1+ macrophages and CD18+ NK cells in RM patients.

LARGE SCALE DATA

The raw single-cell sequence data reported in this paper were deposited at the National Omics Data Encyclopedia (www.biosino.org), under the accession number OEP002901.

LIMITATIONS, REASONS FOR CAUTION

The number of decidual samples for scRNA-seq was limited and in-depth functional studies on DSCs are warranted in future studies.

WIDER IMPLICATIONS OF THE FINDINGS

Identification of three DSC subpopulations opens new avenues for further investigation of their roles in RM patients.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Strategic Priority Research Program (No. XDB29030302), Frontier Science Key Research Project (QYZDB-SSW-SMC036), Chinese Academy of Sciences; National Key Research and Development Program of China (2021YFE0200600), National Natural Science Foundation of China (No. 31770960), Shanghai Municipal Science and Technology Major Project (No. 2019SHZDZX02, HS2021SHZX001), and Shanghai Committee of Science and Technology (17411967800). All authors report no conflict of interest.

The Progress of Research on Genetic Factors of Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is both mental and physical health problem affecting about 1-5% of women of childbearing age. The etiology of RPL is complex, involving chromosomal abnormalities, autoimmune diseases, metabolic disorders, and endometrial dysfunction. The causes of abortion are still unknown in more than 50% of these cases. With the development of science and technology, an increasing number of scholars focus on this field and find that genetic factors may play an essential role in unexplained RPL, such as embolism-related genes, immune factor-related genes, and chromosomal numeric, and structural variation. This review summarizes the genetic factors associated with RPL, including genetic mutations and genetic polymorphisms, chromosomal variants, and chromosomal polymorphisms. Many related genetic factors have been found to be demographically and geographically relevant, some of which can be used for risk prediction or screening for the etiology of RPL. However, it is difficult to predict and prevent RPL due to uncertain pathogenesis and highly variable clinical presentation. Therefore, the genetic factors of RPL still need plentiful research to obtain a more accurate understanding of its pathogenesis and to provide more detection means for the screening and prevention of RPL.

A hybrid discrete-continuum model of immune responses to SARS-CoV-2 infection in the lung alveolar region, with a focus on interferon induced innate response

We develop a lattice-based, hybrid discrete-continuum modeling framework for SARS-CoV-2 exposure and infection in the human lung alveolar region, or parenchyma, the massive surface area for gas exchange. COVID-19 pneumonia is alveolar infection by the SARS-CoV-2 virus significant enough to compromise gas exchange. The modeling framework orchestrates the onset and progression of alveolar infection, spatially and temporally, beginning with a pre-immunity baseline, upon which we superimpose multiple mechanisms of immune protection conveyed by interferons and antibodies. The modeling framework is tunable to individual profiles, focusing here on degrees of innate immunity, and to the evolving infection-replication properties of SARS-CoV-2 variant strains. The model employs partial differential equations for virion, interferon, and antibody concentrations governed by diffusion in the thin fluid coating of alveolar cells, species and lattice interactions corresponding to sources and sinks for each species, and multiple immune protections signaled by interferons. The spatial domain is a two-dimensional, rectangular lattice of alveolar type I (non-infectable) and type II (infectable) cells with a stochastic, species-concentration-governed, switching dynamics of type II lattice sites from healthy to infected. Once infected, type II cells evolve through three phases: an eclipse phase during which RNA copies (virions) are assembled; a shedding phase during which virions and interferons are released; and then cell death. Model simulations yield the dynamic spread of, and immune protection against, alveolar infection and viral load from initial sites of exposure. We focus in this paper on model illustrations of the diversity of outcomes possible from alveolar infection, first absent of immune protection, and then with varying degrees of four known mechanisms of interferon-induced innate immune protection. We defer model illustrations of antibody protection to future studies. Results presented reinforce previous recognition that interferons produced solely by infected cells are insufficient to maintain a high efficacy level of immune protection, compelling additional mechanisms to clear alveolar infection, such as interferon production by immune cells and adaptive immunity (e.g., T cells). This manuscript was submitted as part of a theme issue on "Modelling COVID-19 and Preparedness for Future Pandemics".

Dysfunction of CCR1+ decidual macrophages is a potential risk factor in the occurrence of unexplained recurrent pregnancy loss

Recurrent pregnancy loss (RPL) puzzles 1-3% of women of childbearing age worldwide. Immunological factors account for more than 60% of cases of unexplained RPL (URPL); however, the underlying mechanism remains unclear. Here, using single-cell sequencing data and functional experiments with clinical samples, we identified a distinct population of CCR1⁺ decidual macrophages (dMφ) that were preferentially enriched in the decidua from normal early pregnancies but were substantially decreased in patients with URPL. Specific gene signatures endowed CCR1⁺ dMφ with immunosuppressive and migration-regulatory properties, which were attenuated in URPL. Additionally, CCR1⁺ dMφ promoted epithelial-to-mesenchymal transition (EMT) to promote trophoblast migration and invasion by activating the ERK1/2 signaling pathway. Decidual stromal cell (DSC)-derived CCL8 was the key regulator of CCR1⁺ dMφ as CCL8 recruited peripheral CCR1⁺ monocytes, induced a CCR1⁺ dMφ-like phenotype, and reinforced the CCR1⁺ dMφ-exerted modulation of trophoblasts. In patients with URPL, CCL8 expression in DSCs was decreased and trophoblast EMT was defective. Our findings revealed that CCR1⁺ dMφ play an important role in immune tolerance and trophoblast functions at the maternal-fetal interface. Additionally, decreased quantity and dysregulated function of CCR1⁺ dMφ result in URPL. In conclusion, we provide insights into the crosstalk between CCR1⁺ dMφ, trophoblasts, and DSCs at the maternal-fetal interface and macrophage-targeted interventions of URPL.

Single cell transcriptomic analysis of human amnion identifies cell-specific signatures associated with membrane rupture and parturition

Background

The human amnion is an intrauterine tissue which is involved in the initiation of parturition. In-depth understanding of gene expression signatures of individual cell types in the amnion with respect to membrane rupture at parturition may help identify crucial initiators of parturition for the development of specific strategies to prevent preterm birth, a leading cause of perinatal mortality.

Results

Six major cell types were revealed in human amnion including epithelial cells, fibroblasts and immunocytes as well as three other cell types expressing dual cell markers including epithelial/fibroblast, immune/epithelial and immune/fibroblast markers. The existence of cell types expressing these dual cell markers indicates the presence of epithelial-mesenchymal (EMT), epithelial-immune (EIT) and mesenchymal-immune (MIT) transitions in amnion at parturition. We found that the rupture zone of amnion exhibited some specific increases in subcluster proportions of immune and EMT cells related to extracellular matrix remodeling and inflammation in labor. The non-rupture zone exhibited some common changes in subcluster compositions of epithelial and fibroblast cells with the rupture zone in labor, particularly those related to oxidative stress and apoptosis in epithelial cells and zinc ion transport in fibroblasts. Moreover, we identified that C–C motif chemokine ligand 20 (CCL20) was among the top up-regulated genes in amnion epithelial cells, fibroblasts and immunocytes in the rupture zone at parturition. Studies in pregnant mice showed that administration of CCL20 induced immunocytes infiltration to tissues at the maternal–fetal interface and led to preterm birth.

Conclusions

Apart from the conventional epithelial, fibroblast and immunocytes, human amnion cells may undergo EMT, EIT and FIT in preparation for parturition. Intense inflammation and ECM remodeling are present in the rupture zone, while enhanced apoptosis and oxidative stress in epithelial cells and zinc ion transport in fibroblasts are present in amnion regardless of the rupture zones at parturition. CCL20 derived from the major cell types of the amnion participates in labor onset.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00797-4.