NLRP7 contributes to in vitro decidualization of endometrial stromal cells

HLA-C expression in extravillous trophoblasts is determined by an ELF3-NLRP2/NLRP7 regulatory axis

The distinct human leukocyte antigen (HLA) class I expression pattern of human extravillous trophoblasts (EVT) endows them with unique tolerogenic properties that enable successful pregnancy. Nevertheless, how this process is elaborately regulated remains elusive. Previously, E74 like ETS transcription factor 3 (ELF3) was identified to govern high-level HLA-C expression in EVT. In the present study, ELF3 is found to bind to the enhancer region of two adjacent NOD-like receptor (NLR) genes, NLR family pyrin domain-containing 2 and 7 (NLRP2, NLRP7). Notably, our analysis of ELF3-deficient JEG-3 cells, a human choriocarcinoma cell line widely used to study EVT biology, suggests that ELF3 transactivates NLRP7 while suppressing the expression of NLRP2. Moreover, we find that NLRP2 and NLRP7 have opposing effects on HLA-C expression, thus implicating them in immune evasion at the maternal-fetal interface. We confirmed that NLRP2 suppresses HLA-C levels and described a unique role for NLRP7 in promoting HLA-C expression in JEG-3. These results suggest that these two NLR genes, which arose via gene duplication in primates, are fine-tuned by ELF3 yet have acquired divergent functions to enable proper expression levels of HLA-C in EVT, presumably through modulating the degradation kinetics of IkBα. Targeting the ELF3-NLRP2/NLRP7-HLA-C axis may hold therapeutic potential for managing pregnancy-related disorders, such as recurrent hydatidiform moles and fetal growth restriction, and thus improve placental development and pregnancy outcomes.

Endometrial decidualization status modulates endometrial microvascular complexity and trophoblast outgrowth in gelatin methacryloyl hydrogels

The endometrium undergoes rapid cycles of vascular growth, remodeling, and breakdown during the menstrual cycle and pregnancy. Decidualization is an endometrial differentiation process driven by steroidal sex hormones that is critical for blastocyst-uterine interfacing and blastocyst implantation. Certain pregnancy disorders may be linked to decidualization processes. However, much remains unknown regarding the role of decidualization and reciprocal trophoblast-endometrial interactions on endometrial angiogenesis and trophoblast invasion. Here, we report an engineered endometrial microvascular network embedded in gelatin hydrogels that displays morphological and functional patterns of decidualization. Vessel complexity and biomolecule secretion are sensitive to decidualization and affect trophoblast motility, but that signaling between endometrial and trophoblast cells was not bi-directional. Although endometrial microvascular network decidualization status influences trophoblast cells, trophoblast cells did not induce structural changes in the endometrial microvascular networks. These findings add to a growing literature that the endometrium has biological agency at the uterine-trophoblast interface during implantation. Finally, we form a stratified endometrial tri-culture model, combining engineered microvascular networks with epithelial cells. These endometrial microvascular networks provide a well-characterized platform to investigate dynamic changes in angiogenesis in response to pathological and physiological endometrial states.

Cell Chirality of Micropatterned Endometrial Microvascular Endothelial Cells

Chirality is an intrinsic cellular property that describes cell polarization biases along the left-right axis, apicobasal axis, or front-rear axes. Cell chirality plays a significant role in the arrangement of organs in the body as well as in the orientation of organelles, cytoskeletons, and cells. Vascular networks within the endometrium, the mucosal inner lining of the uterus, commonly display spiral architectures that rapidly form across the menstrual cycle. Herein, the role of endometrial-relevant extracellular matrix stiffness, composition, and soluble signals on endometrial endothelial cell chirality is systematically examined using a high-throughput microarray. Endometrial endothelial cells display marked patterns of chirality as individual cells and as cohorts in response to substrate stiffness and environmental cues. Vascular networks formed from endometrial endothelial cells also display shifts in chirality as a function of exogenous hormones. Changes in cellular-scale chirality correlate with changes in vascular network parameters, suggesting a critical role for cellular chirality in directing endometrial vessel network organization.

NLRP3 inflammasome pathway, the hidden balance in pregnancy: A comprehensive review

The balance of the inflammatory response is indispensable during pregnancy. Inflammasomes are the cytosolic supramolecular protein complexes activated by pattern recognition receptors. These receptors recognize the pathogen and damage/danger-associated molecular patterns. NLRP3 inflammasome complex consists mainly of NLRP3 (leucine-rich repeat-containing and pyrin domain-containing protein 3), a cytosolic sensor molecule, ASC (apoptosis-associated speck-like protein containing a CARD) protein and a cysteine protease pro-caspase-1 as an effector molecule. This complex has a role in producing inflammatory cytokines, interleukin 1 beta and interleukin 18, and inflammasome-dependent programmed cell death pathway pyroptosis. In this review, we focused on and summarised the NLRP3 inflammasome and its roles in normal and pathological pregnancies. The NLRP3 inflammasome pathway influences endometrial receptivity and embryo invasion by inducing epithelial-mesenchymal transition. Abnormal inflammasome activation in the endometrium may adversely affect endometrial receptivity. In addition, NLRP3 inflammasome pathway overactivation may mediate the abnormal inflammatory response at the maternal-fetal interface and be associated with pregnancy complications, such as recurrent implantation failure, pregnancy loss, pre-term birth and pre-eclampsia. Therefore, targeting the NLRP3 inflammasome pathway could develop a new therapeutic approach to prevent the aforementioned pregnancy pathologies.

Energy metabolism and maternal-fetal tolerance working in decidualization

One pivotal aspect of early pregnancy is decidualization. The decidualization process includes two components: the differentiation of endometrial stromal cells to decidual stromal cells (DSCs), as well as the recruitment and education of decidual immune cells (DICs). At the maternal-fetal interface, stromal cells undergo morphological and phenotypic changes and interact with trophoblasts and DICs to provide an appropriate decidual bed and tolerogenic immune environment to maintain the survival of the semi-allogeneic fetus without causing immunological rejection. Despite classic endocrine mechanism by 17 β-estradiol and progesterone, metabolic regulations do take part in this process according to recent studies. And based on our previous research in maternal-fetal crosstalk, in this review, we elaborate mechanisms of decidualization, with a special focus on DSC profiles from aspects of metabolism and maternal-fetal tolerance to provide some new insights into endometrial decidualization in early pregnancy.

Changes in expression levels of Nod-like receptors in the spleen of ewes

Nucleotide-binding oligomerization domain receptors (NOD-like receptors, NLRs) have critical effects on interfaces of the immune and reproductive systems, and the spleen plays a key role in both innate and adaptive immune functions. It is hypothesized that NLR family participates in maternal splenic immune regulation during early pregnancy in sheep. In this study, maternal spleens were collected on day 16 of the estrous cycle, and days 13, 16 and 25 of gestation (n = 6 for each group) in ewes. Expression of NLR family, including NOD1, NOD2, class II transactivator (CIITA), NLR family apoptosis inhibitory protein (NAIP), nucleotide-binding oligomerization domain, Leucine rich repeat and Pyrin domain containing 1 (NLRP1), NLRP3 and NLRP7, was analyzed using quantitative real-time PCR, Western blot and immunohistochemistry analysis. The results revealed that expression levels of NOD1, NOD2, CIITA and NLRP3 were downregulated at days 13 and 16 of pregnancy, but expression of NLRP3 was increased at day 25 of pregnancy. In addition, expression values of NAIP and NLRP7 mRNA and proteins were improved at days 16 and 25 of pregnancy, and NLRP1 was peaked at days 13 and 16 of pregnancy in the maternal spleen. Furthermore, NOD2 and NLRP7 proteins were limited to the capsule, trabeculae and splenic cords. In summary, early pregnancy changes expression of NLR family in the maternal spleen, which may be related with the maternal splenic immunomodulation during early pregnancy in sheep.

Modulation of Nod-like Receptor Expression in the Thymus during Early Pregnancy in Ewes

Nucleotide-binding oligomerization domain receptors (NOD-like receptors, NLRs) are involved in modulating the innate immune responses of the trophoblast and the placenta in normal pregnancy. The thymus participates in regulation of innate and adaptive immune responses. However, it is unclear whether expression of NLR is modulated in the maternal thymus during early pregnancy. In this study, thymuses were sampled at day 16 of the estrous cycle, and at days 13, 16 and 25 of gestation (n = 6 for each group) from ewes after slaughter. Different stages were chosen because the maternal thymus was under the different effects of interferon-tau and/or progesterone or not. RT-qPCR, Western blot and immunohistochemistry analysis were used to analyze the expression of the NLR family, including NOD1; NOD2; major histocompatibility complex class II transactivator (CIITA); NLR family apoptosis inhibitory protein (NAIP); nucleotide-binding oligomerization domain and Leucine-rich repeat and Pyrin domain containing protein 1 (NLRP1), NLRP3 and NLRP7. The results showed that expression level of NOD1 was changed with the pregnancy stages, and expression levels of NOD2, CIITA, NAIP, NLRP1, NLRP3 and NLRP7 mRNA and proteins were peaked at day 13 of pregnancy. The levels of NOD2 and CIITA were increased during early pregnancy. The stainings for NOD2 and NLRP7 proteins were located in epithelial reticular cells, capillaries and thymic corpuscles. In summary, pregnancy stages changed expression of NLR family in the maternal thymus, which may be related to the modulation of maternal thymic immune responses, and beneficial for normal pregnancy in sheep.

Early Pregnancy Modulates Expression of the Nod-like Receptor Family in Lymph Nodes of Ewes

NOD receptors (NLRs) mediate adaptive immune responses and immune tolerance. Nevertheless, it is not clear if gestation modulates the NLR signaling pathway in lymph nodes of ewes. In this study, lymph nodes of ewes were collected at day 16 of the estrous cycle, and at days 13, 16 and 25 of gestation (n = 6 for each group). RT-qPCR, Western blot and immunohistochemistry analysis were used to analyze the expression of the NLR family, including NOD1, NOD2, CIITA, NAIP, NLRP1, NLRP3 and NLRP7. The data showed that early gestation enhanced expression of NOD1, CIITA, NLRP1, NLRP3 and NLRP7 mRNA, as well as proteins at day 16 of gestation, and the expression levels of NOD2, CIITA, NLRP1 and NLRP7 were higher at days 13 and 25 of gestation than day 16 of the estrous cycle. However, NOD1 expression was lower on days 13 and 25 of gestation compared to day 16 of the estrous cycle, and early gestation suppressed NAIP expression. In summary, early pregnancy modulated expression of the NLR family in ovine lymph nodes, which participates in immune regulation, and this modulation may be necessary for pregnancy establishment in ewes.

Decidualization of Stromal Cells Promotes Involvement of Mast Cells in Successful Human Pregnancy by Increasing Stem Cell Factor Expression

Decidualization of endometrial stromal cells and the presence of immunocompetent cells, including human mast cells, play important roles in the establishment of pregnancy. In the present study, the effects of decidualization of endometrial stromal cells on the function of decidual mast cells were elucidated. The in vitro assay revealed that decidualization of an endometrial stromal cell line, T HESCs, increased stem cell factor (SCF) mRNA expression. Decidualization of T HESCs enhanced the production of leukemia inhibitory factor (LIF), and the migration of LAD2 cells when co-cultured with T HESCs and LAD2 cells. In addition, decidualization of T HESCs enhanced cell migration in a human trophoblast cell line, HTR-8/SVneo, increased CD9 expression, a marker for extravillous trophoblast (EVT) differentiation, and decreased the secretion of β human chorionic gonadotropin (hCG), a marker for syncytiotrophoblast (ST) differentiation, when co-cultured with T HESCs, LAD2 cells, and HTR-8/SVneo cells, in a LIF-dependent manner. Histological samples from uterine pregnancies, including decidual stromal cells, showed increased SCF mRNA expression, mast cell numbers and LIF mRNA expression thereof compared with tubal pregnancy. SCF produced by decidual stromal cells enhanced the migration and LIF production of mast cells, and promoted the migration and differentiation of trophoblasts to increase the likelihood of successful human pregnancy.

Role of NLRP7 in Normal and Malignant Trophoblast Cells

Gestational choriocarcinoma (CC) is an aggressive cancer that develops upon the occurrence of abnormal pregnancies such as Hydatidiform moles (HMs) or upon non-molar pregnancies. CC cells often metastasize in multiple organs and can cause maternal death. Recent studies have established an association between recurrent HMs and mutations in the Nlrp7 gene. NLRP7 is a member of a new family of proteins that contributes to innate immune processes. Depending on its level of expression, NLRP7 can function in an inflammasome-dependent or independent pathway. To date, the role of NLRP7 in normal and in malignant human placentation remains to be elucidated. We have recently demonstrated that NLRP7 is overexpressed in CC trophoblast cells and may contribute to their acquisition of immune tolerance via the regulation of key immune tolerance-associated factors, namely HLA family, βCG and PD-L1. We have also demonstrated that NLRP7 increases trophoblast proliferation and decreases their differentiation, both in normal and tumor conditions. Actual findings suggest that NLRP7 expression may ensure a strong tolerance of the trophoblast by the maternal immune system during normal pregnancy and may directly affect the behavior and aggressiveness of malignant trophoblast cells. The proposed review summarizes recent advances in the understanding of the significance of NLRP7 overexpression in CC and discusses its multifaceted roles, including its function in an inflammasome-dependent or independent pathways.

Transcriptomic analysis of human endometrial stromal cells during early embryo invasion

PURPOSE

During early embryo invasion (48 h after embryo attachment), what functional changes accompany dynamic gene expression alterations in human endometrial stromal cells?

METHOD

In the present study, primary human endometrial stromal cells (phESCs) were cultured. After in vitro decidualization, primary human endometrial stromal cells (phESCs) were cultured with blastocysts for 48 h. During this process, blastocysts attached and invaded the phESCs (embryo-invaded primary human endometrial stromal cells, ehESCs). We performed comprehensive transcriptomic profiling of phESCs (two replicates) and ehESCs (five replicates) and analyzed the differentially expressed gene (DEGs) sets for gene ontology (GO) terms and Kyoto encyclopaedia of genes and genomes (KEGG) pathway enrichment. To analyse potential connectivity patterns between the transcripts in these DEG sets, a protein-protein interaction (PPI) network was constructed using the STRING database.

RESULTS

A total of 592 DEGs were identified between phESCs and ehESCs after embryo invasion. Primary human endometrial stromal cells underwent significant transcriptomic changes that occur in a stepwise fashion. Oxidative phosphorylation, mitochondrial organization, and P53 signalling pathways were significantly altered in phESCs after embryo invasion. EP300 may play a key role in regulating transcription via chromatin remodelling to facilitate the adaptive gene expression changes that occur during embryo invasion.

CONCLUSIONS

Our data identify dynamic transcriptome changes that occur in endometrial stromal cells within 48 h after embryo invasion. The pathways that we found to be enriched in phESCs after embryo invasion (oxidative phosphorylation, mitochondrial organization, and P53 signalling) may represent novel mechanisms underlying embryo implantation, and may illuminate the reasons that some women experience reproductive failure.Key messagesHuman endometrial stromal cells have undergone changes in gene expression regulation and signalling pathways during the embryo invasion.Mitochondrial-oxidative phosphorylation changes in human stromal cells manifested as down-regulation of gene expression in the electron transport chain.TP53 signalling pathway and transcriptional regulator EP300 assist stromal cells to get adaptive changes during embryo invasion phase.

Deciphering the Role of PGRMC1 During Human Decidualization Using an In Vitro Approach

CONTEXT

Non-classical membrane progesterone receptor (mPRs) and progesterone receptor membrane component 1 (PGRMC1) expression have been detected in endometrium, but their role in decidualization had not yet been investigated. We previously demonstrated PGRMC1 downregulation in receptive endometrium and that its overexpression inhibits decidualization. Furthermore, during decidualization, PGRMC1 mainly interacts with proteins involved in biosynthesis, intracellular transport, and mitochondrial activity.

OBJECTIVE

To determine PGRMC1 and mPRs signaling role during decidualization.

METHODS

Isolated primary endometrial stromal cells (EnSC) were decidualized in vitro in the presence of classic stimuli (E2 + P4), PGRMC1 inhibitor (AG205), or membrane-impermeable P4 (P4-BSA). Endometrial biopsies were obtained from 19 fertile oocyte donors attending the IVI-Valencia in vitro fertilization (IVF) clinic. EnSC decidualization was evaluated by prolactin ELISA and F-actin immunostaining. Progesterone receptor localization was evaluated by immunofluorescence. EnSC transcriptomic profiles were analyzed by microarray technology.

RESULTS

PGRMC1 inhibition during EnSC decidualization (AG205dEnSC) does not interfere with EnSC cytoskeletal rearrangements and prolactin secretion. However, global transcriptional profiling revealed more differentially expressed genes in AG205dEnSC than in dEnSC, compared with nondecidualized EnSC (ndEnSC). In silico analysis showed that PGRMC1 inhibition upregulated more genes related to metabolism, molecular transport, and hormonal biosynthesis compared with control dEnSC. EnSC decidualized in the presence of P4-BSA showed a similar behavior as ndEnSC in terms of morphological features, absence of prolactin secretion, and transcriptomic pattern.

CONCLUSION

Our findings associate PGRMC1 to hormonal biosynthesis, metabolism, and vesicular transport-important cellular functions for dEnSC supporting pregnancy. Activation of membrane P4 receptor signaling alone was unable to induce downstream effects needed for proper decidualization.

Reproductive Outcomes from Maternal Loss of Nlrp2 Are Not Improved by IVF or Embryo Transfer Consistent with Oocyte-Specific Defect

Nlrp2 encodes a protein of the oocyte subcortical maternal complex (SCMC), required for embryo development. We previously showed that loss of maternal Nlrp2 in mice causes subfertility, smaller litters with birth defects, and growth abnormalities in offspring, indicating that Nlrp2 is a maternal effect gene and that all embryos from Nlrp2-deficient females that were cultured in vitro arrested before the blastocysts stage. Here, we used time-lapse microscopy to examine the development of cultured embryos from superovulated Nlrp2-deficient and wild-type mice after in vivo and in vitro fertilization. Embryos from Nlrp2-deficient females had similar abnormal cleavage and fragmentation and arrested by blastocyst stage, irrespective of fertilization mode. This indicates that in vitro fertilization does not further perturb or improve the development of cultured embryos. We also transferred embryos from superovulated Nlrp2-deficient and wild-type females to wild-type recipients to investigate if the abnormal reproductive outcomes of Nlrp2-deficient females are primarily driven by oocyte dysfunction or if a suboptimal intra-uterine milieu is a necessary factor. Pregnancies with transferred embryos from Nlrp2-deficient females produced smaller litters, stillbirths, and offspring with birth defects and growth abnormalities. This indicates that the reproductive phenotype is oocyte-specific and is not rescued by development in a wild-type uterus. We further found abnormal DNA methylation at two maternally imprinted loci in the kidney of surviving young adult offspring, confirming persistent DNA methylation disturbances in surviving offspring. These findings have implications for fertility treatments for women with mutations in NLRP2 and other genes encoding SCMC proteins.

NLRP7: From inflammasome regulation to human disease

Nucleotide-binding oligomerization domain (NOD) and leucine-rich repeat (LRR)-containing receptors or NOD-like receptors (NLRs) are cytosolic pattern recognition receptors, which sense conserved microbial patterns and host-derived danger signals to elicit innate immune responses. The activation of several prototypic NLRs, including NLR and pyrin domain (PYD) containing (NLRP) 1, NLRP3 and NLR and caspase recruitment domain (CARD) containing (NLRC) 4, results in the assembly of inflammasomes, which are large, cytoplasmic multiprotein signalling platforms responsible for the maturation and release of the pro-inflammatory cytokines IL-1β and IL-18, and for the induction of a specialized form of inflammatory cell death called pyroptosis. However, the function of other members of the NLR family, including NLRP7, are less well understood. NLRP7 has been linked to innate immune signalling, but its precise role is still controversial as it has been shown to positively and negatively affect inflammasome responses. Inflammasomes are essential for homeostasis and host defence, but inappropriate inflammasome responses due to hereditary mutations and somatic mosaicism in inflammasome components and defective regulation have been linked to a broad spectrum of human diseases. A compelling connection between NLRP7 mutations and reproductive diseases, and in particular molar pregnancy, has been established. However, the molecular mechanisms by which NLRP7 mutations contribute to reproductive diseases are largely unknown. In this review, we focus on NLRP7 and discuss the current evidence of its role in inflammasome regulation and its implication in human reproductive diseases.

hsa_circ_001946 elevates HOXA10 expression and promotes the development of endometrial receptivity via sponging miR-135b

Background

Impaired endometrial receptivity is a major reason for embryo implantation failure. There’s a paucity of information regarding the role of circRNAs on endometrial receptivity. Here, we investigated the function of hsa_circ_001946 on endometrial receptivity and its mechanisms.

Methods

A total of 50 women composing 25 with recurrent implantation failure and 25 who conceived after their implantation were recruited in this study. Expression of hsa_circ_001946, miR-135b, and HOXA10 was evaluated by quantitative RT-PCR (qRT-PCR) in biopsied endometrial tissue samples. The levels of HOXA10, and cell cycle markers (CCNB1, CDK1, and CCND1) were determined by IHC and western blotting assays. Binding relationship among miR-135b, hsa_circ_001946 and HOXA10 were confirmed by dual luciferase reporter assays and western blotting. MTT assays and cell cycle assays by FACS were employed to evaluate the proliferation and cell cycle of cells. T-HESCs were cultured with 1 µM medroxyprogesterone acetate (MPA) and 0.5 mM 8-bromoadenosine 3’:5’-cyclic monophosphate (8-Br-cAMP) to induce decidualization. The mechanisms and functions of hsa_circ_001946 on decidualization were further assessed by qRT-PCR evaluating the expression of hsa_circ_001946, miR-135b, HOXA10 and decidual markers (PRL and IGFBP1) in T-HESCs.

Results

Endometrial tissues from patients with recurrent implantation failure had lower hsa_circ_001946 expression, higher miR-135b expression, and lower HOXA10 expression. Hsa_circ_001946 promoted HOXA10 expression by sponging miR-135b in T-HESCs. Overexpression of hsa_circ_001946 restored cell proliferation and cell cycle that were disrupted by miR-135b overexpression in T-HESCs. Decidualized T-HESCs had higher hsa_circ_001946 expression, lower miR-135b expression, and higher HOXA10 expression. Overexpression of hsa_circ_001946 reversed the expression of decidual markers (PRL and IGFBP1) that were suppressed by miR-135b overexpression in T-HESCs.

Conclusions

In conclusion, our findings suggest that hsa_circ_001946 promotes cell proliferation and cell cycle process and increases expression of decidualization markers to enhance endometrial receptivity progression via sponging miR-135b and elevating HOXA10.

Evaluating the influence of progesterone concentration and time of exposure on in vitro endometrial decidualisation

This study aimed to evaluate the influence of progesterone (concentration and time of exposure) on endometrial decidualisation using an in vitro model cell line: Human Endometrial Stromal Cells (HESCs). HESCs exposed to progesterone (1 and 10 μM) had higher percentages of decidualised cells and higher expression of the decidual marker (Insulin Like Growth Factor Binding Protein 1 (IGFBP1)) compared with those exposed to (0.1 μM). Among those HESCs cultured with 1 μM progesterone for 11 days, the highest rate of morphological differentiation (40-50%) occurred between days 7-9 and IGFBP1 peaked on day 7. The cell-cycle pathway was significantly down-regulated in HESCs exposed to at least 1 μM progesterone regardless of the incubation period. We conclude that exposure to high progesterone concentration for 7-9 days is essential to maximise the process of decidualisation.

The pivotal roles of the NOD-like receptors with a PYD domain, NLRPs, in oocytes and early embryo development†

Nucleotide-binding oligomerization domain (NOD)-like receptors with a pyrin domain (PYD), NLRPs, are pattern recognition receptors, well recognized for their important roles in innate immunity and apoptosis. However, several NLRPs have received attention for their new, specialized roles as maternally contributed genes important in reproduction and embryo development. Several NLRPs have been shown to be specifically expressed in oocytes and preimplantation embryos. Interestingly, and in line with divergent functions, NLRP genes reveal a complex evolutionary divergence. The most pronounced difference is the human-specific NLRP7 gene, not identified in rodents. However, mouse models have been extensively used to study maternally contributed NLRPs. The NLRP2 and NLRP5 proteins are components of the subcortical maternal complex (SCMC), which was recently identified as essential for mouse preimplantation development. The SCMC integrates multiple proteins, including KHDC3L, NLRP5, TLE6, OOEP, NLRP2, and PADI6. The NLRP5 (also known as MATER) has been extensively studied. In humans, inactivating variants in specific NLRP genes in the mother are associated with distinct phenotypes in the offspring, such as biparental hydatidiform moles (BiHMs) and preterm birth. Maternal-effect recessive mutations in KHDC3L and NLRP5 (and NLRP7) are associated with reduced reproductive outcomes, BiHM, and broad multilocus imprinting perturbations. The precise mechanisms of NLRPs are unknown, but research strongly indicates their pivotal roles in the establishment of genomic imprints and post-zygotic methylation maintenance, among other processes. Challenges for the future include translations of findings from the mouse model into human contexts and implementation in therapies and clinical fertility management.

Mitochondrial and Metabolic Dynamics of Endometrial Stromal Cells During the Endometrial Cycle

The endometrial cycle in response to hormonal stimulation is essential for implantation. The female has endometrium that repeats this cycle through about half of a lifetime. The cycle includes three phases, proliferative, secretory, and menstrual, and each phase has distinct characteristics. The endometrial stromal cells (EnSCs) in each phase also have specialized characteristics, including cell cycle, morphologies, and cellular metabolic state. So we hypothesized that the cells in each phase have unique mitochondrial morphologies because they are generally linked to cellular metabolic state. To investigate the metabolic characteristics in each phase, we investigated the mitochondrial morphologies by transmission electron microscopy, oxygen consumption rate (OCR), and intracellular adenosine triphosphate (ATP) production. The decidualized EnSCs have shorter mitochondria than those in the proliferative phase. Besides, they also displayed distinct intracellular structural characteristics compared with the proliferative phase, such as ribosome-rich endoplasmic reticulum and increased formation of vesicles. OCR and luminescent ATP detection assay revealed that the basal respiration and ATP production in the decidualized EnSCs were lower than those in the proliferative phase. Thus, we concluded that morphological and intracellular structural changes were induced during the decidualization. Moreover, the decreased mitochondrial length was shown to correlate with decreased dependency on oxidative phosphorylation and ATP concentration in EnSCs.

ALK3-SMAD1/5 Signaling Mediates the BMP2-Induced Decrease in PGE2 Production in Human Endometrial Stromal Cells and Decidual Stromal Cells

BMP2 is a critical factor that is involved in the processes of embryo implantation and uterine decidualization. The expression of cyclooxygenase (COX) and subsequent prostaglandin E2 (PGE2) production are critical for successful pregnancy. However, it is not clear whether BMP2 can regulate the production of PG during endometrial decidualization. The aim of this study was to investigate the effects of BMP2 on COX-1 expression and PGE2 production as well as the underlying molecular mechanisms in the human endometrium. Immortalized human endometrial stromal cells (HESCs) and human decidual stromal cells (HDSCs) were used as the study model to investigate the effects of BMP2-induced cellular activities. Our results showed that BMP2 treatment significantly decreased PGE2 production by downregulating COX-1 expression in both human endometrial stromal and decidual stromal cells. Additionally, BMP2 induced an increase in the levels of phosphorylated SMAD1/5/8, and this effect was completely abolished by the addition of the inhibitors DMH-1 and dorsomorphin, but not by SB431542. Knocking down ALK3 completely reversed the BMP2-induced downregulation of COX-1. Moreover, concomitantly knocking down SMAD1 and SMAD5 completely reversed the BMP2-induced downregulation of COX-1. Our results indicated that BMP2 decreased PGE2 production by downregulating COX-1 expression, most likely through the ALK3/SMAD1-SMAD5 signaling pathway in human endometrial stromal and human decidual stromal cells. These findings deepen our understanding of the functional role of BMP2 in the regulation of endometrial decidualization in humans.

Human Amnion Epithelial Cells (AECs) Respond to the FSL-1 Lipopeptide by Engaging the NLRP7 Inflammasome

Context and Objectives: Inflammation is the leading mechanism involved in both physiological and pathological rupture of fetal membranes. Our aim was to obtain a better characterization of the inflammasome-dependent inflammation processes in these tissues, with a particular focus on the nucleotide-binding oligomerization domain (NOD)–like receptor, pyrin domain containing protein 7 (NLRP7) inflammasome.

Methods: The presence of NLRP7 inflammasome actors [NLRP7, apoptosis-associated speck–like protein containing a CARD domain (ASC), and caspase-1] was confirmed by reverse transcriptase–polymerase chain reaction (RT-PCR) in human amnion and choriodecidua at the three trimesters and at term. The protein concentrations were then determined by enzyme-linked immunosorbent assay in term tissues, with or without labor. The presence of Mycoplasma salivarium and Mycoplasma fermentans in human fetal membranes was investigated using a PCR approach. Human amnion epithelial cells (AECs) were treated for 4 or 20 h with fibroblast-stimulating lipopeptide-1 (FSL-1), a M. salivarium–derived ligand. Transcripts and proteins quantity was then measured by RT–quantitative PCR and Western blotting, respectively. NLRP7 and ASC colocalization was confirmed by immunofluorescence. Western blots allowed analysis of pro–caspase-1 and gasdermin D cleavage.

Results: NLRP7, ASC, and caspase-1 transcripts were expressed in both sheets of human fetal membranes during all pregnancy stages, but only ASC protein expression was increased with labor. In addition, M. salivarium and M. fermentans were detected for the first time in human fetal membranes. NLRP7 and caspase-1 transcripts, as well as NLRP7, ASC, and pro–caspase-1 protein levels, were increased in FSL-1–treated AECs. The NLRP7 inflammasome assembled around the nucleus, and pro–caspase-1 and gasdermin D were cleaved into their mature forms after FSL-1 stimulation.

Conclusion: Two new mycoplasmas, M. salivarium and M. fermentans, were identified in human fetal membranes, and a lipopeptide derived from M. salivarium was found to induce NLRP7 inflammasome formation in AECs.

NLRP7 Is Involved in the Differentiation of the Decidual Macrophages

Macrophage polarization, regulated appropriately, may play important roles in successful pregnancy. In the face of the vital roles of decidua macrophages in pregnancy, it is insufficient to recognize the trigger of macrophage differentiation and polarization. We aimed to explore the link between the NLRP7 gene and macrophage polarization in human deciduas. Here, we enrolled the endometrial tissues from eight pregnant women in the first trimester. We found that NLRP7 was abundant in endometrial tissues and that NLRP7 was expressed in decidual macrophages of the first-trimester pregnancy. NLRP7 was predominately expressed in the decidual M2 macrophages, as compared with the M1 macrophages. Furthermore, our results suggest that NLRP7 is associated with decidual macrophage differentiation. NLRP7 over-expression suppresses the expression of M1 markers and enhances the expression of the M2 markers. Considering that NLRP7 relates to decidualization and macrophage differentiation, we propose that NLRP7 is a primate-specific multitasking gene to maintain endometrial hemostasis and reproductive success. This finding may pave the way for therapies of pathological pregnancies.

A gelatin hydrogel to study endometrial angiogenesis and trophoblast invasion

The endometrium is the lining of the uterus and site of blastocyst implantation. Each menstrual cycle, the endometrium cycles through rapid phases of growth, remodelling and breakdown. Significant vascular remodelling is also driven by trophoblast cells that form the outer layer of the blastocyst. Trophoblast invasion and remodelling enhance blood flow to the embryo ahead of placentation. Understanding the mechanisms of endometrial vascular remodelling and trophoblast invasion would provide key insights into endometrial physiology and cellular interactions critical for establishment of pregnancy. The objective of this study was to develop a tissue engineering platform to investigate the processes of endometrial angiogenesis and trophoblast invasion in a three-dimensional environment. We report adaptation of a methacrylamide-functionalized gelatin hydrogel that presents matrix stiffness in the range of the native tissue, supports the formation of endometrial endothelial cell networks with human umbilical vein endothelial cells and human endometrial stromal cells as an artificial endometrial perivascular niche and the culture of an endometrial epithelial cell layer, enables culture of a hormone-responsive stromal compartment and provides the capacity to monitor the kinetics of trophoblast invasion. With these studies, we provide a series of techniques that will instruct researchers in the development of endometrial models of increasing complexity.

Human menstrual blood-derived stromal/stem cells modulate functional features of natural killer cells

Although natural killer (NK) cells play a crucial role in the maintenance of a successful pregnancy, their cytotoxic activity should be tightly controlled. We hypothesized that endometrial mesenchymal stromal/stem cells (eMSCs) could potentially attenuate the functional features of NK cells. Herein, we assessed immunomodulatory effects of menstrual blood-derived stromal/stem cells (MenSCs), as a surrogate for eMSCs, on NK cells function. Our results showed that MenSCs induced proliferation of NK cells. However, IFN-γ/IL-1β pretreated MenSCs significantly inhibited NK cell proliferation. Of 41 growth factors tested, MenSCs produced lower levels of insulin-like growth factor binding proteins (IGFBPs) 1-4, VEGF-A, β-NGF, and M-CSF compared to bone marrow-derived mesenchymal stem cells (BMSCs). MenSCs displayed high activity of IDO upon IFN-γ treatment. The antiproliferative potential of IFN-γ/IL-1β-pretreated MenSCs was mediated through IL-6 and TGF-β. MenSCs impaired the cytotoxic activity of NK cells on K562 cells, consistent with the lower expression of perforin, granzymes A, and B. We also observed that in vitro decidualization of MenSCs in the presence of IFN-γ reduced the inhibitory effect of MenSCs on NK cell cytotoxicity against K562 target cells. Additionally, MenSCs were found to be prone to NK cell-mediated lysis in an MHC-independent manner. Our findings imply that dysregulation of NK cells in such pregnancy-related disorders as miscarriage may stem from dysfunctioning of eMSCs.