Zonula occludens-1 and E-cadherin are coordinately expressed in the mouse uterus with the initiation of implantation and decidualization

Uterine prostaglandin DP receptor-induced upon implantation contributes to decidualization together with EP4 receptor

To investigate the yet-unknown roles of prostaglandins (PGs) in the uterus, we analyzed the expression of various PG receptors in the uterus. We found that three types of Gs-coupled PG receptors, DP, EP2, and EP4, were expressed in luminal epithelial cells from the peri-implantation period to late pregnancy. DP expression was also induced in stromal cells within the mesometrial region, whereas EP4 was expressed in stromal cells within the anti-mesometrial region during the peri-implantation period. The timing of DP induction after embryo attachment correlated well with that of cyclooxygenase-2 (COX-2); however, COX-2-expressing stromal cells were located in the vicinity of the embryo, whereas DP-expressing stromal cells surrounded these cells on the mesometrial side. Specific [3H]PGD2-binding activity was detected in the decidua of uteri, with PGD2 synthesis comparable to that of PGE2 detected in the uteri during the peri-implantation period. Administration of the COX-2-specific inhibitor celecoxib caused adverse effects on decidualization, as demonstrated by the attenuated weight of the implantation sites, which was recovered by the simultaneous administration of a DP agonist. Such a rescuing effect of the DP agonist was mimicked by an EP4 agonist, but not an EP2 agonist. While the importance of DP signaling was shown pharmacologically, DP/EP2 double deficiency did not affect implantation and decidualization, suggesting the contribution of EP4 to these processes. Indeed, administration of an EP4 antagonist substantially affected decidualization in DP/EP2-deficient mice. These results suggest that COX-2-derived PGD2 and PGE2 contribute to decidualization via a coordinated pathway of DP and EP4 receptors.

Spatial and molecular anatomy of the endometrium during embryo implantation: a current overview of key regulators of blastocyst invasion

Embryo implantation is composed of three steps: blastocyst apposition, adhesion/attachment and invasion. Blastocyst invasion has been studied less extensively than the other two events. Historically, studies conducted using electron microscopy have shown the removal of epithelial cells in the vicinity of the attached blastocysts in rodents, although the underlying mechanisms have remained unclear. Here, we describe recent studies using mice with uterine-specific gene deletion that demonstrated important roles for nuclear proteins such as progesterone receptor, hypoxia inducible factor and retinoblastoma in the regulation of embryo invasion. In these mouse models, the detachment of the endometrial luminal epithelium, decidualization in the stroma, and the activation of trophoblasts have been found to be important in ensuring embryo invasion. This review summarizes the molecular signaling associated with these cellular events, mainly evidenced by mouse models.

TJP1 suppresses trophoblast cell invasion by expressing E2F8 in the human placenta

Adequate extravillous trophoblast (EVT) invasion into the maternal decidua is important for human placental development. We identified that E2F transcription factor 8 (E2F8) suppresses EVT invasion, and that tight junction protein-1 (TJP1) is a potential downstream target gene of E2F8. We investigated the role of TJP1 in the human placenta and regulation of TJP1 expression by E2F8. TJP1 expression decreased in E2F8 knockdown HTR-8/SVneo cells. TJP1 and E2F8 were co-expressed in villi in the first-trimester placenta and in EVTs and villi in the third-trimester placenta. TJP1 was significantly increased in the pre-eclamptic compared with control placenta. TJP1 knockdown increased the invasion of HTR-8/SVneo cells, while TJP1 overexpression inhibited cell invasion. Halo-E2F8 overexpression significantly increased TJP1 expression and TJP1 transcription compared with control placenta. Our findings suggest that E2F8 promotes TJP1 transcription, and that TJP1 expression by E2F8 inhibits EVT invasion. TJP1 and E2F8 may be related to pre-eclampsia pathogenesis.

Spatiotemporally distinct roles of cyclooxygenase-1 and cyclooxygenase-2 at fetomaternal interface in mice

Embryo implantation is crucial for ensuring a successful pregnancy outcome and subsequent child health. The intrauterine environment during the peri-implantation period shows drastic changes in gene expression and cellular metabolism in response to hormonal stimuli and reciprocal communication with embryos. Here, we performed spatial transcriptomic analysis to elucidate the mechanisms underlying embryo implantation. Transcriptome data revealed that lipid metabolism pathways, especially arachidonic acid-related (AA-related) ones, were enriched in the embryo-receptive luminal epithelia. Cyclooxygenases (COXs), rate-limiting enzymes involved in prostaglandin production by AA, were spatiotemporally regulated in the vicinity of embryos during implantation, but the role of each COX isozyme in the uterus for successful pregnancy was unclear. We established uterine-specific COX2-knockout (uKO) and COX1/uterine COX2-double-KO (COX1/COX2-DKO) mice. COX2 uKO caused deferred implantation with failed trophoblast invasion, resulting in subfertility with reduced pregnancy rates and litter sizes. COX1/COX2 DKO induced complete infertility, owing to abrogated embryo attachment. These results demonstrate that both isozymes have distinct roles during embryo implantation. Spatial transcriptome and lipidome analyses revealed unique profiles of prostaglandin synthesis by each COX isozyme and spatiotemporal expression patterns of downstream receptors throughout the endometrium. Our findings reveal previously unappreciated roles of COXs at the fetomaternal interface to establish early pregnancy.

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.

Affinity-tagged SMAD1 and SMAD5 mouse lines reveal transcriptional reprogramming mechanisms during early pregnancy

Endometrial decidualization, a prerequisite for successful pregnancies, relies on transcriptional reprogramming driven by progesterone receptor (PR) and bone morphogenetic protein (BMP)-SMAD1/SMAD5 signaling pathways. Despite their critical roles in early pregnancy, how these pathways intersect in reprogramming the endometrium into a receptive state remains unclear. To define how SMAD1 and/or SMAD5 integrate BMP signaling in the uterus during early pregnancy, we generated two novel transgenic mouse lines with affinity tags inserted into the endogenous SMAD1 and SMAD5 loci (Smad1HA/HA and Smad5PA/PA). By profiling the genome-wide distribution of SMAD1, SMAD5, and PR in the mouse uterus, we demonstrated the unique and shared roles of SMAD1 and SMAD5 during the window of implantation. We also showed the presence of a conserved SMAD1, SMAD5, and PR genomic binding signature in the uterus during early pregnancy. To functionally characterize the translational aspects of our findings, we demonstrated that SMAD1/5 knockdown in human endometrial stromal cells suppressed expressions of canonical decidual markers (IGFBP1, PRL, FOXO1) and PR-responsive genes (RORB, KLF15). Here, our studies provide novel tools to study BMP signaling pathways and highlight the fundamental roles of SMAD1/5 in mediating both BMP signaling pathways and the transcriptional response to progesterone (P4) during early pregnancy.

Affinity-tagged SMAD1 and SMAD5 mouse lines reveal transcriptional reprogramming mechanisms during early pregnancy

Endometrial decidualization, a prerequisite for successful pregnancies, relies on transcriptional reprogramming driven by progesterone receptor (PR) and bone morphogenetic protein (BMP)-SMAD1/SMAD5 signaling pathways. Despite their critical roles in early pregnancy, how these pathways intersect in reprogramming the endometrium into a receptive state remains unclear. To define how SMAD1 and/or SMAD5 integrate BMP signaling in the uterus during early pregnancy, we generated two novel transgenic mouse lines with affinity tags inserted into the endogenous SMAD1 and SMAD5 loci (Smad1HA/HA and Smad5PA/PA). By profiling the genome-wide distribution of SMAD1, SMAD5, and PR in the mouse uterus, we demonstrated the unique and shared roles of SMAD1 and SMAD5 during the window of implantation. We also showed the presence of a conserved SMAD1, SMAD5, and PR genomic binding signature in the uterus during early pregnancy. To functionally characterize the translational aspects of our findings, we demonstrated that SMAD1/5 knockdown in human endometrial stromal cells suppressed expressions of canonical decidual markers (IGFBP1, PRL, FOXO1) and PR-responsive genes (RORB, KLF15). Here, our studies provide novel tools to study BMP signaling pathways and highlight the fundamental roles of SMAD1/5 in mediating both BMP signaling pathways and the transcriptional response to progesterone (P4) during early pregnancy.

Roles of lipid mediators in early pregnancy events

Background

Early pregnancy events, including embryo implantation, are critical for maintaining a healthy pregnancy and facilitating childbirth. Despite numerous signaling pathways implicated in establishing early pregnancy, a comprehensive understanding of implantation remains elusive.

Methods

This paper provides a comprehensive review of the current research on lipids in the context of early pregnancy, with a particular focus on feto-maternal communications.

Main Findings

Embryo implantation entails direct interaction between uterine tissues and embryos. Introducing embryos triggers significant changes in uterine epithelial morphology and stromal differentiation, facilitating embryo implantation through communication with uterine tissue. Studies employing genetic models and chemical compounds targeting enzymes and receptors have elucidated the crucial roles of lipid mediators-prostaglandins, lysophosphatidic acid, sphingosine-1-phosphate, and cannabinoids-in early pregnancy events.

Conclusion

Given the high conservation of lipid synthases and receptors across species, lipid mediators likely play pivotal roles in rodents and humans. Further investigations into lipids hold promise for developing novel diagnostic and therapeutic approaches for infertility in humans.

Deciphering a critical role of uterine epithelial SHP2 in parturition initiation at single cell resolution

The timely onset of female parturition is a critical determinant for pregnancy success. The highly heterogenous maternal decidua has been increasingly recognized as a vital factor in setting the timing of labor. Despite the cell type specific roles in parturition, the role of the uterine epithelium in the decidua remains poorly understood. This study uncovers the critical role of epithelial SHP2 in parturition initiation via COX1 and COX2 derived PGF2α leveraging epithelial specific Shp2 knockout mice, whose disruption contributes to delayed parturition initiation, dystocia and fetal deaths. Additionally, we also show that there are distinct types of epithelium in the decidua approaching parturition at single cell resolution accompanied with profound epithelium reformation via proliferation. Meanwhile, the epithelium maintains the microenvironment by communicating with stromal cells and macrophages. The epithelial microenvironment is maintained by a close interaction among epithelial, stromal and macrophage cells of uterine stromal cells. In brief, this study provides a previously unappreciated role of the epithelium in parturition preparation and sheds lights on the prevention of preterm birth.

Spatiotemporal insight into early pregnancy governed by immune-featured stromal cells

Endometrial decidualization connecting embryo implantation and placentation is transient but essential for successful pregnancy, which, however, is not systematically investigated. Here, we use a scStereo-seq technology to spatially visualize and define the dynamic functional decidual hubs assembled by distinct immune, endothelial, trophoblast, and decidual stromal cells (DSCs) in early pregnant mice. We unravel the DSC transdifferentiation trajectory and surprisingly discover a dual-featured type of immune-featured DSCs (iDSCs). We find that immature DSCs attract immune cells and induce decidual angiogenesis at the mesenchymal-epithelial transition hub during decidualization initiation. iDSCs enable immune cell recruitment and suppression, govern vascularization, and promote cytolysis at immune cell assembling and vascular hubs, respectively, to establish decidual homeostasis at a later stage. Interestingly, dysfunctional and spatially disordered iDSCs cause abnormal accumulation of immune cells in the vascular hub, which disrupts decidual hub specification and eventually leads to pregnancy complications in DBA/2-mated CBA/J mice.

Expression of nuclear factor-erythroid 2-related factor 2 (Nrf2) in mouse uterus during the peri-implantation period

Nuclear factor-erythroid 2-related factor- 2 (Nrf2) is a nuclear transcription factor that facilitates transcription of genes for detoxification enzymes and antioxidant proteins. We investigated the distribution and expression of Nrf2 during the peri-implantation period. We detected Nrf2 in uteri of mice during estrus (control) and on days 1, 4, 5, 6 and 8 of pregnancy using immunohistochemistry, quantitative real-time polymerase chain reaction and western blotting. Nrf2 immunostaining was significantly greater on days 1, 5 and 6 of pregnancy compared to controls, and on days 4 and 8 of pregnancy; western blotting results were consistent with immunohistochemical observations. Nrf2 mRNA levels on days 5 and 8 were significantly higher than for control uteri. Increased expression of Nrf2 on days 1, 5 and 6 of pregnancy may be important for uterine receptivity, implantation and decidualization by protecting the developing embryo and uterus from the adverse effects of oxidative stress.

Uterus: A Unique Stem Cell Reservoir Able to Support Cardiac Repair via Crosstalk among Uterus, Heart, and Bone Marrow

Clinical evidence suggests that the prevalence of cardiac disease is lower in premenopausal women compared to postmenopausal women and men. Although multiple factors contribute to this difference, uterine stem cells may be a major factor, as a high abundance of these cells are present in the uterus. Uterine-derived stem cells have been reported in several studies as being able to contribute to cardiac neovascularization after injury. However, our studies uniquely show the presence of an “utero-cardiac axis”, in which uterine stem cells are able to home to cardiac tissue to promote tissue repair. Additionally, we raise the possibility of a triangular relationship among the bone marrow, uterus, and heart. In this review, we discuss the exchange of stem cells across different organs, focusing on the relationship that exists between the heart, uterus, and bone marrow. We present increasing evidence for the existence of an utero-cardiac axis, in which the uterus serves as a reservoir for cardiac reparative stem cells, similar to the bone marrow. These cells, in turn, are able to migrate to the heart in response to injury to promote healing.

The investigation of hippo signaling pathway in mouse uterus during peri-implantation period

PURPOSE

Events in the uterus during the peri-implantation period include embryo development, acquisition of uterine receptivity, implantation and decidualization. Hippo signaling pathway regulates cell proliferation, apoptosis and differentiation. We aimed to determine localization and expressions of pYAP (Phospho Yes-associated protein), YAP (Yes-associated protein), TEAD1 (TEA domain family member 1) and CTGF (Connective tissue growth factor), members of the Hippo signaling pathway, in the mouse uterus during the peri-implantation period.

METHODS

Pregnant mice were randomly separated into 5 groups: 1st, 4th, 5th, 6th, and 8th days of pregnancy groups. Non-pregnant female mice in estrous phase were included in the estrous group. Uteri and implantation sites were collected. Also, inter-implantation sites were collected from the 5th day of pregnancy group. pYAP, YAP, TEAD-1 and CTGF were detected by immunohistochemistry and Western blotting.

RESULTS

We observed that the expressions of YAP, TEAD-1 and CTGF were increased in the luminal and glandular epithelium on the 1st and 4th days of pregnancy when epithelial proliferation occurred. pYAP expression was high, and YAP and CTGF expressions were low in the luminal epithelium of the implantation sites on the 5th day of pregnancy, when epithelial differentiation occurred. pYAP expression was low, YAP and CTGF expressions were high at implantation sites on the 6th and 8th days of pregnancy, where decidua was formed.

CONCLUSION

Our findings suggest that the Hippo signaling pathway might be involved in implantation and decidualization. Our findings will guide further studies and may help to elucidate underlying causes of implantation failure and pregnancy loss.

Single-cell analysis of mouse uterus at the invasion phase of embryo implantation

Background

Embryo implantation into the uterus is a crucial step for human reproduction. A hypothesis has been proposed that the molecular circuit invented by trophoblasts for invasive embryo implantation during evolution might be misused by cancer cells to promote malignancy. Unfortunately, our current understanding of the molecular mechanism underlying embryo implantation is far from complete.

Results

Here we used the mouse as an animal model and generated a single-cell transcriptomic atlas of the embryo implantation site of mouse uterus at the invasion phase of embryo implantation on gestational day 6. We revealed 23 distinct cell clusters, including 5 stromal cell clusters, 2 epithelial cell clusters, 1 smooth muscle cell cluster, 2 pericyte clusters, 4 endothelial cell clusters, and 9 immune cell clusters. Through data analysis, we identified differentially expression changes in all uterine cell types upon embryo implantation. By integrated with single-cell RNA-seq data from E5.5 embryos, we predicted cell–cell crosstalk between trophoblasts and uterine cell types.

Conclusions

Our study provides a valuable resource for understanding of the molecular mechanism of embryo implantation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00749-y.

A gene network of uterine luminal epithelium organizes mouse blastocyst implantation

Purpose

The receptive endometrium is critical for blastocyst implantation. In mice, after blastocysts enter the uterine cavities on day 4 of pregnancy (day 1 = vaginal plug), blastocyst attachment is completed within 24 h, accompanied by dynamic interactions between the uterine luminal epithelium and the blastocysts. Any failures in this process compromise subsequent pregnancy outcomes. Here, we performed comprehensive analyses of gene expression at the luminal epithelium in the peri-implantation period.

Methods

RNA-seq combined with laser microdissection (LMD) was used to reveal unique gene expression kinetics in the epithelium.

Results

We found that the prereceptive epithelium on day 3 specifically expresses cell cycle-related genes. In addition, days 3 and 4 epithelia express glutathione pathway-related genes, which are protective against oxidative stresses. In contrast, day 5 epithelium expresses genes involved in glycolysis and the regulation of cell proliferation. The genes highly expressed on days 3 and 4 compared to day 5 are related to progesterone receptor signaling, and the genes highly expressed on day 5 compared to days 3 and 4 are associated with the ones regulated by H3K27me3.

Conclusions

These results suggest that specific gene expression patterns govern uterine functions during early pregnancy, contributing to implantation success.

Modulation of E-Cadherin and N-Cadherin by ovarian steroids and embryonic stimuli

Endometrium is a dynamic tissue that undergoes extensive remodelling to attain a receptive state which is further modulated in presence of an embryo for successful initiation of pregnancy. Cadherins are the proteins of the junctional complex of which E-cadherin (E-Cad) is crucial for maintaining epithelial cell state and integrity of the epithelial barrier; gain of N-cadherin (N-Cad) in epithelial cells leads to epithelial to mesenchymal transition (EMT). In the present study, we investigated the expression of E-Cad and N-Cad in the mouse endometrial luminal epithelium and its modulation by estrogen, progesterone, and embryonic stimuli. We observed that E-Cad is diffusely expressed in the luminal epithelium of mouse endometrium during the estrus stage and upon estrogen treatment. It is apico-laterally and basolaterally sorted at the diestrus stage and in response to the combined treatment of estrogen and progesterone. In 3D spheroids of human endometrial epithelial cells, combined treatment with estrogen and progesterone led to lateral sorting of E-Cad without any effects on its mRNA levels. at the time of embryo implantation, there is loss of E-Cad along with the gain of N-Cad and SNAIL expression suggestive of EMT in the luminal epithelium. This EMT is possibly driven by embryonic stimuli as treatment with estrogen and progesterone did not lead to the gain of N-Cad expression in the mouse endometrium in vivo or in human endometrial epithelial cells in vitro. In conclusion, the present study demonstrates that steroid hormones directly affect E-Cad sorting in the endometrial epithelium which undergo EMT in response to embryonic stimuli.

Loss of basigin expression in uterine cells leads to subfertility in female mice†

Basigin (BSG) is a transmembrane glycoprotein involved in cell proliferation, angiogenesis, and tissue remodeling. BSG has been shown to be essential for male and female reproduction although little is known about its role in normal uterine function. To study the potential function of BSG in the female reproductive tract, we generated mice with conditional knockout of Bsg in uterine cells using progesterone receptor-Cre and hypothesized that BSG is required for normal pregnancy in mice. Fertility study data showed that the conditional knockout mice had significantly reduced fertility compared to controls. Ovarian function of the conditional knockout mice appeared normal with no difference in the number of superovulated oocytes collected or in serum progesterone levels between the conditional knockout and the control mice. Uterine tissues collected at various times of gestation showed increased abnormalities in implantation, decidualization, placentation, and parturition in the conditional knockout mice. Uterine cross sections on Day 5 of pregnancy showed implantation failure and abnormal uterine epithelial differentiation in a large proportion of the conditional knockout mice. There was a compromised decidual response to artificial decidualization stimuli and decreased mRNA and protein levels for decidualization genes in the uteri of the conditional knockout mice. We also observed altered protein expression of monocarboxylate transporter 1 (MCT1), as well as impaired angiogenesis in the conditional knockout uteri compared to the controls. These results support that BSG is required for successful pregnancy through its functions in implantation and decidualization.

Maternal Neutrophil Depletion Fails to Avert Systemic Lipopolysaccharide-Induced Early Pregnancy Defects in Mice

Maternal infection-induced early pregnancy complications arise from perturbation of the immune environment at the uterine early blastocyst implantation site (EBIS), yet the underlying mechanisms remain unclear. Here, we demonstrated in a mouse model that the progression of normal pregnancy from days 4 to 6 induced steady migration of leukocytes away from the uterine decidual stromal zone (DSZ) that surrounds the implanted blastocyst. Uterine macrophages were found to be CD206⁺ M2-polarized. While monocytes were nearly absent in the DSZ, DSZ cells were found to express monocyte marker protein Ly6C. Systemic endotoxic lipopolysaccharide (LPS) exposure on day 5 of pregnancy led to: (1) rapid (at 2 h) induction of neutrophil chemoattractants that promoted huge neutrophil infiltrations at the EBISs by 24 h; (2) rapid (at 2 h) elevation of mRNA levels of MyD88, but not Trif, modulated cytokines at the EBISs; and (3) dose-dependent EBIS defects by day 7 of pregnancy. Yet, elimination of maternal neutrophils using anti-Ly6G antibody prior to LPS exposure failed to avert LPS-induced EBIS defects allowing us to suggest that activation of Tlr4-MyD88 dependent inflammatory pathway is involved in LPS-induced defects at EBISs. Thus, blocking the activation of the Tlr4-MyD88 signaling pathway may be an interesting approach to prevent infection-induced pathology at EBISs.

Induction of the epithelial-mesenchymal transition in the endometrium by chronic endometritis in infertile patients

Background

The purpose of the present study was to evaluate the relationship between chronic endometritis and the epithelial-mesenchymal transition in the endometrium of infertile patients in the implantation phase.

Methods

Endometrial biopsy specimens from 66 infertility patients were analyzed. The presence of chronic endometritis was investigated by immunostaining for CD138. Immunohistochemical staining for E-cadherin, N-cadherin, Slug, and Snail was performed, and the expression profiles were statistically analyzed according to the presence of chronic endometritis. When the loss of E-cadherin expression and/or the positive expression of N-cadherin was detected, the specimen was considered epithelial-mesenchymal transition-positive. Epithelial-mesenchymal transition-positive cases were also statistically analyzed according to the presence of chronic endometritis. The characteristics of the patients in the epithelial-mesenchymal transition-positive and epithelial-mesenchymal transition-negative groups were compared. The association between variables, including age, body mass index, gravidity, parity, and each causative factor of infertility and epithelial-mesenchymal transition positivity was analyzed.

Results

The rates of the loss of E-cadherin expression, the gain of N-cadherin and epithelial-mesenchymal transition positivity were significantly higher in chronic endometritis patients. The expression of Slug, cytoplasmic Snail, and nuclear Snail was also detected at significantly higher rates in chronic endometritis patients. Chronic endometritis were related to the epithelial-mesenchymal transition.

Conclusion

The epithelial-mesenchymal transition was frequently detected in the endometrium in infertile patients with chronic endometritis. Since the epithelial-mesenchymal transition is associated with chronic endometritis, the epithelial-mesenchymal transition appears to be involved in the alteration of mechanisms of implantation.

Regulation of ARHGAP19 in the endometrial epithelium: a possible role in the establishment of uterine receptivity

BACKGROUND

The establishment of uterine receptivity is essential for embryo implantation initiation and involves a significant morphological transformation in the endometrial epithelial cells (EECs). The remodeling of junctional complexes and membrane-associated cytoskeleton is crucial for epithelial transformation. However, little is known about how this process is regulated in EECs during the receptive phase. ARHGAP19 is a Rho GTPase-activating protein that participates in various cytoskeletal-related events, including epithelial morphogenesis. Here, we investigated the role of ARHGAP19 in endometrial epithelial transformation during the establishment of uterine receptivity. The upstream regulator of ARHGAP19 was also investigated.

METHODS

ARHGAP19 expression was examined in mouse uteri during early pregnancy and in human EEC lines. The role of ARHGAP19 was investigated by manipulating its expression in EECs. The effect of ARHGAP19 on junctional proteins in EECs was examined by western blotting and immunofluorescence. The effect of ARHGAP19 on microvilli was examined by scanning electron microscopy. The upstream microRNA (miRNA) was predicted using online databases and validated by the dual-luciferase assay. The in vivo and in vitro effect of miRNA on endogenous ARHGAP19 was examined by uterine injection of miRNA agomirs and transfection of miRNA mimics or inhibitors.

RESULTS

ARHGAP19 was upregulated in the receptive mouse uteri and human EECs. Overexpression of ARHGAP19 in non-receptive EECs downregulated the expression of junctional proteins and resulted in their redistribution. Meanwhile, upregulating ARHGAP19 reorganized the cytoskeletal structure of EECs, leading to a decline of microvilli and changes in cell configuration. These changes weakened epithelial cell polarity and promoted the transition of non-receptive EECs to a receptive phenotype. Besides, miR-192-5p, a miRNA that plays a key role in maintaining epithelial properties, was validated as an upstream regulator of ARHGAP19.

CONCLUSION

These results suggested that ARHGAP19 may contribute to the transition of EECs from a non-receptive to a receptive state by regulating the remodeling of junctional proteins and membrane-associated cytoskeleton.

miR-192-5p suppresses uterine receptivity formation through impeding epithelial transformation during embryo implantation

The establishment of uterine receptivity is a prerequisite for embryo implantation and begins with the transformation of the luminal epithelium. MicroRNAs (miRNAs) have been widely reported to be involved in the regulation of embryo implantation, but their roles in establishing uterine receptivity remain unclear. In this study, through small RNA sequencing analysis, we showed that a low level of miR-192-5p is essential for initiating implantation in mice, and transient upregulation of miR-192-5p led to implantation failure. In situ hybridization results revealed that miR-192-5p was primarily expressed in the endometrial epithelium, and dysregulation of miR-192-5p interfered with the performance of the luminal epithelium, resulting in inadequate receptivity. By manipulating miR-192-5p expression in mouse uterus and an endometrial epithelial cell line, we showed that miR-192-5p maintains cell polarity through stabilizing adherens junction protein E-cadherin, thereby preventing epithelial-mesenchymal transition. Furthermore, miR-192-5p preserved the pattern of microvilli as well as Muc1 expression on the apical membrane of epithelial cells, thereby avoiding embryo adhesion. Moreover, miR-192-5p was found to be regulated by ovarian steroids. Collectively, this study demonstrated that the physiological role of miR-192-5p in mouse uterus is to maintain the nonreceptive state of epithelial cells and prevent their transformation to the receptive state. Thus, a sustained high level of miR-192-5p is detrimental to embryo implantation. These findings help elucidate the mechanisms involved in miRNA-based regulation of uterine physiology in early pregnancy, and may even contribute to the diagnosis and treatment of infertility.

The role of mesenchymal-epithelial transition in endometrial function

BACKGROUND

The human uterine endometrium undergoes significant remodeling and regeneration on a rapid and repeated basis, after parturition, menstruation, and in some cases, injury. The ability of the adult endometrium to undergo cyclic regeneration and differentiation/decidualization is essential for successful human reproduction. Multiple key physiologic functions of the endometrium require the cells of this tissue to transition between mesenchymal and epithelial phenotypes, processes known as mesenchymal-epithelial transition (MET) and epithelial-mesenchymal transition (EMT). Although MET/EMT processes have been widely characterized in embryonic development and in the context of malignancy, mounting evidence demonstrates the importance of MET/EMT in allowing the endometrium the phenotypic and functional flexibility necessary for successful decidualization, regeneration/re-epithelialization and embryo implantation.

OBJECTIVE AND RATIONALE

The objective of this review is to provide a comprehensive summary of the observations concerning MET and EMT and their regulation in physiologic uterine functions, specifically in the context of endometrial regeneration, decidualization and embryo implantation.

SEARCH METHODS

Using variations of the search terms 'mesenchymal-epithelial transition', 'mesenchymal-epithelial transformation', 'epithelial-mesenchymal transition', 'epithelial-mesenchymal transformation', 'uterus', 'endometrial regeneration', 'endometrial decidualization', 'embryo implantation', a search of the published literature between 1970 and 2018 was conducted using the PubMed database. In addition, we searched the reference lists of all publications included in this review for additional relevant original studies.

OUTCOMES

Multiple studies demonstrate that endometrial stromal cells contribute to the regeneration of both the stromal and epithelial cell compartments of the uterus, implicating a role for MET in mechanisms responsible for endometrial regeneration and re-epithelialization. During decidualization, endometrial stromal cells undergo morphologic and functional changes consistent with MET in order to accommodate embryo implantation. Under the influence of estradiol, progesterone and multiple other factors, endometrial stromal fibroblasts acquire epithelioid characteristics, such as expanded cytoplasm and rough endoplasmic reticulum required for greater secretory capacity, rounded nuclei, increased expression of junctional proteins which allow for increased cell-cell communication, and a reorganized actin cytoskeleton. During embryo implantation, in response to both maternal and embryonic-derived signals, the maternal luminal epithelium as well as the decidualized stromal cells acquire the mesenchymal characteristics of increased migration/motility, thus undergoing EMT in order to accommodate the invading trophoblast.

WIDER IMPLICATIONS

Overall, the findings support important roles for MET/EMT in multiple endometrial functions required for successful reproduction. The endometrium may be considered a unique wound healing model, given its ability to repeatedly undergo repair without scarring or loss of function. Future studies to elucidate how MET/EMT mechanisms may contribute to scar-free endometrial repair will have considerable potential to advance studies of wound healing mechanisms in other tissues.

Primary decidual zone formation requires Scribble for pregnancy success in mice

Scribble (Scrib) is a scaffold protein with multifunctional roles in PCP, tight junction and Hippo signaling. This study shows that Scrib is expressed in stromal cells around the implantation chamber following implantation. Stromal cells transform into epithelial-like cells to form the avascular primary decidual zone (PDZ) around the implantation chamber (crypt). The PDZ creates a permeability barrier around the crypt restricting immune cells and harmful agents from maternal circulation to protect embryonic health. The mechanism underlying PDZ formation is not yet known. We found that uterine deletion of Scrib by a Pgr-Cre driver leads to defective PDZ formation and implantation chamber (crypt) formation, compromising pregnancy success. Interestingly, epithelial-specific Scrib deletion by a lactoferrin-Cre (Ltf-Cre) driver does not adversely affect PDZ formation and pregnancy success. These findings provide evidence for a previously unknown function of stromal Scrib in PDZ formation, potentially involving ZO-1 and Hippo signaling.

The scaffold protein Scribble (Scrib) has roles in PCP and tight junction formation. Here the authors show that during embryo implantation in mouse, Scrib is needed to form the avascular primary decidual zone by transforming stromal cells into an epithelial cell-like barrier around the crypt, protecting the embryo from harmful infiltrations.

Syncytiotrophoblast of Placentae from Women with Zika Virus Infection Has Altered Tight Junction Protein Expression and Increased Paracellular Permeability

The cytotrophoblast of human placenta transitions into an outer multinucleated syncytiotrophoblast (STB) layer that covers chorionic villi which are in contact with maternal blood in the intervillous space. During pregnancy, the Zika virus (ZIKV) poses a serious prenatal threat. STB cells are resistant to ZIKV infections, yet placental cells within the mesenchyme of chorionic villi are targets of ZIKV infection. We seek to determine whether ZIKV can open the paracellular pathway of STB cells. This route is regulated by tight junctions (TJs) which are present in the uppermost portion of the lateral membranes of STB cells. We analyzed the paracellular permeability and expression of E-cadherin, occludin, JAMs -B and -C, claudins -1, -3, -4, -5 and -7, and ZO-1, and ZO-2 in the STB of placentae from ZIKV-infected and non-infected women. In ZIKV-infected placentae, the pattern of expression of TJ proteins was preserved, but the amount of claudin-4 diminished. Placentae from ZIKV-infected women were permeable to ruthenium red, and had chorionic villi with a higher mean diameter and Hofbauer hyperplasia. Finally, ZIKV added to the basolateral surface of a trophoblast cell line reduced the transepithelial electrical resistance. These results suggest that ZIKV can open the paracellular pathway of STB cells.

Low endometrial beta-catenin and cadherins expression patterns are predictive for primary infertility and recurrent pregnancy loss

Inadequate uterine receptivity is responsible for two-third of implanting failures. Aim of the study was to investigate the role of epithelial adherence and tight-junction molecules expressed by human endometrium in predicting womens' fertility outcome. A total of 76 consecutive women, including 24 fertile (G1), 40 primary infertile (G2), and 12 recurrent pregnancy loss (RPL, G3) women, who underwent diagnostic hysteroscopy plus endometrial biopsy between 2005 and 2016 at the Gynecology Division of Sant'Andrea Hospital, Sapienza University of Rome, in Italy, were retrospectively identified and included into the study. Endometrial biopsies were assessed for the immunohistochemical expression of beta-catenin (β-catenin), E-cadherin and K-cadherin biomarkers. Expression profiles were compared between the three groups of patients and were correlated with patients' fertility outcome. In infertile patients there was a significant lower endometrial expression of β-catenin (p = .001), E-cadherin (p = .001) and K-cadherin (p = .002), compared to the fertile ones. Furthermore, β-catenin and E-cadherin intensity gradients of expression at glandular level were found totally reversed in infertile patients. Significant lower expression levels of K-catenin (p = .016) and E-cadherin (p < .0001) at glandular level were found in RPL patients. Results showed that the low endometrial expression of β-catenin, E-cadherin and K-cadherin were associated to fertility-related problems, such as primary intertility and RPL.

Parental perinatal exposure to bisphenol A reduces the threshold to disrupt blastocyst implantation via decreasing talin, occudin and E-cadherin levels

The aim was to evaluate the effect of perinatal BPA exposure of one or both parents on the implantation index and expression of talin, occludin and E-cadherin in the uterine epithelial cells (UEC) of the offspring. Pregnant Wistar dams (F0) received BPA or vehicle from gestational day (GD) 6 to lactation day 21. F1 animals were mated forming four groups: Control dam-Control sire (C♀-C♂), BPA dam -Control sire (B♀-C♂), Control dam -BPA sire (C♀-B♂), BPA dam -BPA sire (B♀-B♂). F1 dams were sacrificed at GD 6. Significantly decreased number of implantation sites was observed in the B♀-B♂ group as compared to the C♀-C♂ group, which correlated with decreased talin apical/basal expression ratio, occludin apical expression, and E-cadherin apical/lateral expression ratio in the UEC. Furthermore, decreased E-cadherin expression in the blastocyst was observed. Our data suggest that reduced protein expressions in F1 BPA offspring could result from decreased progesterone serum levels.

Molecular mechanisms of embryonic implantation in mammals: Lessons from the gene manipulation of mice

BACKGROUND

Human infertility has become a serious and social issue all over the world, especially in developed countries. Numerous types of assisted reproductive technology have been developed and are widely used to treat infertility. However, pregnancy outcomes require further improvement. It is essential to understand the cross-talk between the uterus (mother) and the embryo (fetus) in pregnancy, which is a very complicated event.

METHODS

The mammalian uterus requires many physiological and morphological changes for pregnancy-associated events, including implantation, decidualization, placentation, and parturition, to occur. Here is discussed recent advances in the knowledge of the molecular mechanisms underlying these reproductive events - in particular, embryonic implantation and decidualization - based on original and review articles.

MAIN FINDINGS RESULTS

In mice, embryonic implantation and decidualization are regulated by two steroid hormones: estrogen and progesterone. Along with these hormones, cytokines, cell-cycle regulators, growth factors, and transcription factors have essential roles in implantation and decidualization in mice.

CONCLUSION

Recent studies using the gene manipulation of mice have given considerable insight into the molecular mechanisms underlying embryonic implantation and decidualization. However, as most of the findings are based on mice, comparative research using different mammalian species will be useful for a better understanding of the species-dependent differences that are associated with reproductive events, including embryonic implantation.

Direct Cell⁻Cell Interactions in the Endometrium and in Endometrial Pathophysiology

Cell contacts exhibit a considerable influence on tissue physiology and homeostasis by controlling paracellular and intercellular transport processes, as well as by affecting signaling pathways. Since they maintain cell polarity, they play an important role in cell plasticity. The knowledge about the junctional protein families and their interactions has increased considerably during recent years. In contrast to most other tissues, the endometrium undergoes extensive physiological changes and reveals an extraordinary plasticity due to its crucial role in the establishment and maintenance of pregnancy. These complex changes are accompanied by changes in direct cell–cell contacts to meet the various requirements in the respective developmental stage. Impairment of this sophisticated differentiation process may lead to failure of implantation and embryo development and may be involved in the pathogenesis of endometrial diseases. In this article, we focus on the knowledge about the distribution and regulation of the different junctional proteins in the endometrium during cycling and pregnancy, as well as in pathologic conditions such as endometriosis and cancer. Decoding these sophisticated interactions should improve our understanding of endometrial physiology as well as of the mechanisms involved in pathological conditions.

Adrenomedullin improves fertility and promotes pinopodes and cell junctions in the peri-implantation endometrium

Implantation is a complex event demanding contributions from both embryo and endometrium. Despite advances in assisted reproduction, endometrial receptivity defects persist as a barrier to successful implantation in women with infertility. We previously demonstrated that maternal haploinsufficiency for the endocrine peptide adrenomedullin (AM) in mice confers a subfertility phenotype characterized by defective uterine receptivity and sparse epithelial pinopode coverage. The strong link between AM and implantation suggested the compelling hypothesis that administration of AM prior to implantation may improve fertility, protect against pregnancy complications, and ultimately lead to better maternal and fetal outcomes. Here, we demonstrate that intrauterine delivery of AM prior to blastocyst transfer improves the embryo implantation rate and spacing within the uterus. We then use genetic decrease-of-function and pharmacologic gain-of-function mouse models to identify potential mechanisms by which AM confers enhanced implantation success. In epithelium, we find that AM accelerates the kinetics of pinopode formation and water transport and that, in stroma, AM promotes connexin 43 expression, gap junction communication, and barrier integrity of the primary decidual zone. Ultimately, our findings advance our understanding of the contributions of AM to uterine receptivity and suggest potential broad use for AM as therapy to encourage healthy embryo implantation, for example, in combination with in vitro fertilization.

Uterine glands coordinate on-time embryo implantation and impact endometrial decidualization for pregnancy success

Uterine glands are essential for pregnancy establishment. By employing forkhead box A2 (FOXA2)-deficient mouse models coupled with leukemia inhibitory factor (LIF) repletion, we reveal definitive roles of uterine glands in embryo implantation and stromal cell decidualization. Here we report that LIF from the uterine glands initiates embryo-uterine communication, leading to embryo attachment and stromal cell decidualization. Detailed histological and molecular analyses discovered that implantation crypt formation does not involve uterine glands, but removal of the luminal epithelium is delayed and subsequent decidualization fails in LIF-replaced glandless but not gland-containing FOXA2-deficient mice. Adverse ripple effects of those dysregulated events in the glandless uterus result in embryo resorption and pregnancy failure. These studies provide evidence that uterine glands synchronize embryo-endometrial interactions, coordinate on-time embryo implantation, and impact stromal cell decidualization, thereby ensuring embryo viability, placental growth, and pregnancy success.

The transcription factor FOXA2 is specifically expressed in uterine glands. Here, using two conditional FOXA2 knockout mouse models, the authors show that glandular epithelia of the endometrium are required for timely embryo implantation and subsequent endometrial decidualization during successful pregnancy establishment.

Expression of PIK3IP1 in the murine uterus during early pregnancy

The ovarian steroid hormones, estrogen (E2) and progesterone (P4), are essential regulators of uterine functions necessary for development, embryo implantation, and normal pregnancy. ARID1A plays an important role in steroid hormone signaling in endometrial function and pregnancy. In previous studies, using high density DNA microarray analysis, we identified phosphatidylinositol-3-kinase interacting protein 1 (Pik3ip1) as one of the genes up-regulated by ARID1A. In the present study, we performed real-time qPCR and immunohistochemistry analysis to investigate the regulation of PIK3IP1 by ARID1A and determine expression patterns of PIK3IP1 in the uterus during early pregnancy. The expression of PIK3IP1 was strong at the uterine epithelial and stromal cells of the control mice. However, expression of PIK3IP1 was remarkably reduced in the Pgr^cre/+Arid1a^f/f mice and progesterone receptor knock-out (PRKO) mice. During early pregnancy, PIK3IP1 expression was strong at day 2.5 of gestation (GD 2.5) and then slightly decreased at GD 3.5 at the epithelium and stroma. After implantation, PIK3IP1 expression was detected at the secondary decidualization zone. To determine the ovarian steroid hormone regulation of PIK3IP1, we examined the expression of PIK3IP1 in ovariectomized control, Pgr^cre/+Arid1a^f/f, and PRKO mice treated with P4 or E2. P4 treatment increased the PIK3IP1 expression at the luminal and glandular epithelium of control mice. However, the PIK3IP1 induction was decreased in both the Pgr^cre/+Arid1a^f/f and PRKO mice, compared to controls. Our results identified PIK3IP1 as a novel target of ARID1A and PGR in the murine uterus.

Prostaglandin-Endoperoxide Synthase 1 Mediates the Timing of Parturition in Mice Despite Unhindered Uterine Contractility

Cyclooxygenase (COX)-derived prostaglandins stimulate uterine contractions and prepare the cervix for parturition. Prior reports suggest Cox-1 knockout (KO) mice exhibit delayed parturition due to impaired luteolysis, yet the mechanism for late-onset delivery remains unclear. Here, we examined key factors for normal onset of parturition to determine whether any could account for the delayed parturition phenotype. Pregnant Cox-1KO mice did not display altered timing of embryo implantation or postimplantation growth. Although messenger RNAs of contraction-associated proteins (CAPs) were differentially expressed between Cox-1KO and wild-type (WT) myometrium, there were no differences in CAP agonist-induced intracellular calcium release, spontaneous or oxytocin (OT)-induced ex vivo uterine contractility, or in vivo uterine contractile pressure. Delayed parturition in Cox-1KO mice persisted despite exogenous OT treatment. Progesterone (P4) withdrawal, by ovariectomy or administration of the P4-antagonist RU486, diminished the delayed parturition phenotype of Cox-1KO mice. Because antepartum P4 levels do not decline in Cox-1KO females, P4-treated WT mice were examined for the effect of this hormone on in vivo uterine contractility and ex vivo cervical dilation. P4-treated WT mice had delayed parturition but normal uterine contractility. Cervical distensibility was decreased in Cox-1KO mice on the day of expected delivery and reduced in WT mice with long-term P4 treatment. Collectively, these findings show that delayed parturition in Cox-1KO mice is the result of impaired luteolysis and cervical dilation, despite the presence of strong uterine contractions.

Embryo-epithelium interactions during implantation at a glance

At implantation, with the acquisition of a receptive phenotype in the uterine epithelium, an initial tenuous attachment of embryonic trophectoderm initiates reorganisation of epithelial polarity to enable stable embryo attachment and the differentiation of invasive trophoblasts. In this Cell Science at a Glance article, we describe cellular and molecular events during the epithelial phase of implantation in rodent, drawing on morphological studies both in vivo and in vitro, and genetic models. Evidence is emerging for a repertoire of transcription factors downstream of the master steroidal regulators estrogen and progesterone that coordinate alterations in epithelial polarity, delivery of signals to the stroma and epithelial cell death or displacement. We discuss what is known of the cell interactions that occur during implantation, before considering specific adhesion molecules. We compare the rodent data with our much more limited knowledge of the human system, where direct mechanistic evidence is hard to obtain. In the accompanying poster, we represent the embryo-epithelium interactions in humans and laboratory rodents, highlighting similarities and differences, as well as depict some of the key cell biological events that enable interstitial implantation to occur.

Epithelial-to-Mesenchymal Transition in the Female Reproductive Tract: From Normal Functioning to Disease Pathology

Epithelial-to-mesenchymal transition (EMT) is a physiological process that is vital throughout the human lifespan. In addition to contributing to the development of various tissues within the growing embryo, EMT is also responsible for wound healing and tissue regeneration later in adulthood. In this review, we highlight the importance of EMT in the development and normal functioning of the female reproductive organs (the ovaries and the uterus) and describe how dysregulation of EMT can lead to pathological conditions, such as endometriosis, adenomyosis, and carcinogenesis. We also summarize the current literature relating to EMT in the context of ovarian and endometrial carcinomas, with a particular focus on how molecular mechanisms and the tumor microenvironment can govern cancer cell plasticity, therapy resistance, and metastasis.

Perinatal administration of bisphenol A alters the expression of tight junction proteins in the uterus and reduces the implantation rate

We studied the effect of bisphenol-A (BPA) administration to rats, during the perinatal period, on the fertility of F1 generation and on the expression of tight junction (TJ) proteins in the uterus during early pregnancy. Pregnant Wistar dams (F0) received: BPA-L (0.05mg/kg/day), BPA-H (20mg/kg/day) or vehicle, from gestational day (GD) 6 to lactation day 21. F1 female pups were mated at 3 months of age and sacrificed at GD 1, 3, 6, and 7. Serum hormonal levels, ovulation rate, number of implantation sites and expression of TJ proteins in the uterus of F1 females were evaluated. BPA treatment induced no change in ovulation rate, but induced alterations in progesterone (P₄) and estradiol (E₂) serum levels, and in implantation rate. With regards to TJ proteins, BPA-H increased claudin-1 during all GDs; eliminated the peaks of claudins -3 and -4 at GD 3 and 6, respectively; and decreased claudin-7 at GD 6, ZO-1 from GD 1-6, and claudin-3 at GD 7 in stromal cells. BPA-L instead, eliminated claudin-3 peak at GD 3, increased claudin-4 and decreased claudin-7 from GD 1-6, decreased claudin-1 at GD 3 and 7 and claudin-4 at GD 7 in stromal cells. BPA-L also decreased ZO-1 at GDs 1 and 3 and increased ZO-1 at GD 6. Thus, BPA treatment during perinatal period perturbed, when the animals reached adulthood and became pregnant, the particular expression of TJ proteins in the uterine epithelium and reduced in consequence the number of implantation sites.

Embryo implantation triggers dynamic spatiotemporal expression of the basement membrane toolkit during uterine reprogramming

Basement membranes (BMs) are specialized extracellular scaffolds that influence behaviors of cells in epithelial, endothelial, muscle, nervous, and fat tissues. Throughout development and in response to injury or disease, BMs are fine-tuned with specific protein compositions, ultrastructure, and localization. These features are modulated through implements of the BM toolkit that is comprised of collagen IV, laminin, perlecan, and nidogen. Two additional proteins, peroxidasin and Goodpasture antigen-binding protein (GPBP), have recently emerged as potential members of the toolkit. In the present study, we sought to determine whether peroxidasin and GPBP undergo dynamic regulation in the assembly of uterine tissue BMs in early pregnancy as a tractable model for dynamic adult BMs. We explored these proteins in the context of collagen IV and laminin that are known to extensively change for decidualization. Electron microscopic analyses revealed: 1) a smooth continuous layer of BM in between the epithelial and stromal layers of the preimplantation endometrium; and 2) interrupted, uneven, and progressively thickened BM within the pericellular space of the postimplantation decidua. Quantification of mRNA levels by qPCR showed changes in expression levels that were complemented by immunofluorescence localization of peroxidasin, GPBP, collagen IV, and laminin. Novel BM-associated and subcellular spatiotemporal localization patterns of the four components suggest both collective pericellular functions and distinct functions in the uterus during reprogramming for embryo implantation.

Concurrent administration of diethylhexyl phthalate reduces the threshold dose at which bisphenol A disrupts blastocyst implantation and cadherins in mice

Many people are repeatedly exposed to both bisphenol A (BPA) and diethylhexyl phthalate (DEHP), but there has been little research concerning their effects in combination. Both can disrupt blastocyst implantation in inseminated females, albeit at high doses. We exposed mice on gestation days (GD) 1-4 to combinations of BPA and DEHP in doses below the threshold necessary to disrupt implantation on their own. On GD 6, there were fewer normally-developed implantation sites and more underdeveloped implantation sites in females given the combined subthreshold doses. Uterine epithelial cadherin (e-cadherin), a protein that assists in blastocyst adhesion to the uterine epithelium, was significantly reduced by these combined doses, but not by the individual doses. A similar trend was seen in integrin αvβ3, another uterine adhesion molecule. Cadherin-11 was disrupted by BPA but not DEHP. These data are consistent with competition of BPA and DEHP for conjugating enzymes.

Planar cell polarity signaling in the uterus directs appropriate positioning of the crypt for embryo implantation

Blastocyst implantation is a complex process requiring coordination of a dynamic sequence of embryo-uterine interactions. Blood vessels enter the uterus from the mesometrium, demarcating the uterus into mesometrial (M) and antimesometrial (AM) domains. Implantation occurs along the uterine longitudinal axis within specialized implantation chambers (crypts) that originate within the evaginations directed from the primary lumen toward the AM domain. The morphological orientation of crypts in rodent uteri was recognized more than a century ago, but the mechanism remained unknown. Here we provide evidence that planar cell polarity (PCP) signaling orchestrates directed epithelial evaginations to form crypts for implantation in mice. Uterine deletion of Vang-like protein 2, but not Vang-like protein 1, conferred aberrant PCP signaling, misdirected epithelial evaginations, defective crypt formation, and blastocyst attachment, leading to severely compromised pregnancy outcomes. The study reveals a previously unrecognized role for PCP in executing spatial cues for crypt formation and implantation. Because PCP is an evolutionarily conserved phenomenon, our study is likely to inspire implantation studies of this signaling pathway in humans and other species.

HOXA-10 and E-cadherin expression in the endometrium of women with recurrent implantation failure and recurrent miscarriage

OBJECTIVE

To compare the expression of HOXA-10 and E-cadherin in the endometrium of women with recurrent implantation failure (RIF), women with recurrent miscarriage (RM), and women with proven fertility (normal control; NC).

DESIGN

Observational cohort study.

SETTING

University assisted reproductive unit.

PATIENT(S)

Fifty women were recruited: 18 NC, 12 unexplained RIF, and 20 RM.

INTERVENTIONS(S)

None.

MAIN OUTCOME MEASURE(S)

Endometrial biopsy was precisely timed 7 days after LH surge. The expression of HOXA-10 and E-cadherin were examined by means of immunohistochemistry. H-Scores of staining intensity in the glandular epithelium and stroma were measured.

RESULT(S)

HOXA-10 signal was mainly localized in the nuclei of stroma cells and the cytoplasm of glandular epithelium cells. E-Cadherin signal was found only in the cytoplasm of glandular epithelium cells. The HOXA-10 H-scores in the RIF group and the RM group were significantly lower than in the control group in both the glandular epithelium and stroma. The E-cadherin H-scores in the RM group were also significantly lower than in the control group. Interestingly, there was a positive correlation between HOXA-10 and E-cadherin H-scores in all of the women examined.

CONCLUSION(S)

There is a positive correlation between levels of HOXA-10 and E-cadherin expression in the endometrium, both of which are significantly reduced in women with RIF and RM compared with fertile control women. The findings suggest a potential role of HOXA-10 and E-cadherin in the implantation processes and altered expression in women with reproductive failure.

MFGE8 regulates TGF-β-induced epithelial mesenchymal transition in endometrial epithelial cells in vitro

This study investigated the role of milk fat globule-epidermal growth factor-factor 8 (MFGE8) in TGF-β-induced epithelial-mesenchymal transition (EMT) of endometrial epithelial cells. These were in vitro studies using human endometrial epithelial cells and mouse blastocysts. We investigated the ability of TGF-β to induce EMT in endometrial epithelial cells (HEC-1A) by assessment of cytological phenotype (by light and atomic force microscopy), changes in expression of the markers of cell adhesion/differentiation E- and N-cadherin, and of the transcription factor Snail (by immunofluorescence and immunoblotting), and competence to support embryo attachment in a mouse blastocyst outgrowth assay. We also studied the effects of E-cadherin expression in cells transfected by retroviral shRNA vectors specifically silencing MFGE8. Results demonstrated that TGF-β induced EMT as demonstrated by phenotypic cell changes, by a switch of cadherin expression as well as by upregulation of the expression of the mesenchymal markers Snail and Vimentin. Upon MFGE8 knockdown, these processes were interfered with, suggesting that MFGE8 and TGF-β together may participate in regulation of EMT. This study demonstrated for the first time that endometrial MFGE8 modulates TGF-β-induced EMT in human endometrium cells.

Polycomb repressive complex 1 controls uterine decidualization

Uterine stromal cell decidualization is an essential part of the reproductive process. Decidual tissue development requires a highly regulated control of the extracellular tissue remodeling; however the mechanism of this regulation remains unknown. Through systematic expression studies, we detected that Cbx4/2, Rybp, and Ring1B [components of polycomb repressive complex 1 (PRC1)] are predominantly utilized in antimesometrial decidualization with polyploidy. Immunofluorescence analyses revealed that PRC1 members are co-localized with its functional histone modifier H2AK119ub1 (mono ubiquitination of histone-H2A at lysine-119) in polyploid cell. A potent small-molecule inhibitor of Ring1A/B E3-ubiquitin ligase or siRNA-mediated suppression of Cbx4 caused inhibition of H2AK119ub1, in conjunction with perturbation of decidualization and polyploidy development, suggesting a role for Cbx4/Ring1B-containing PRC1 in these processes. Analyses of genetic signatures by RNA-seq studies showed that the inhibition of PRC1 function affects 238 genes (154 up and 84 down) during decidualization. Functional enrichment analyses identified that about 38% genes primarily involved in extracellular processes are specifically targeted by PRC1. Furthermore, ~15% of upregulated genes exhibited a significant overlap with the upregulated Bmp2 null-induced genes in mice. Overall, Cbx4/Ring1B-containing PRC1 controls decidualization via regulation of extracellular gene remodeling functions and sheds new insights into underlying molecular mechanism(s) through transcriptional repression regulation.

Uterine Prx2 restrains decidual differentiation through inhibiting lipolysis in mice

Uterine decidualization, characterized as extensive stromal cell proliferation, differentiation and polyploidization, is a crucial event for successful pregnancy and is tightly regulated by many different molecules and pathways. Prx2, an evolutionarily conserved homeobox transcription factor expressed in both embryos and adults, plays an important role during mesenchymal cell differentiation. However, it remains unclear what the exact function of Prx2 is in the uterine stromal cells, one type of mesenchymal cells. In the present study, employing in vivo and in vitro stromal cell decidualization models, combining adenovirus-mediated overexpression of Prx2, we found that the expression of Prx2 is initiated in the uterine stromal cells once the blastocyst attached to the epithelium and is always detected around the differentiated decidual zone in the anti-mesometrium of the uterus during post-implantation uterine development. Also, overexpression of Prx2 disturbed stromal-decidual differentiation, which is reflected by the decreased expression of decidual/trophoblast prolactin-related protein (Dtprp), the marker for uterine decidualization in mice. Further, we demonstrate that Prx2 overexpression disturbs lipolysis, leading to lipid droplets accumulation in uterine stromal cells, partially mediated by downregulated expression of adipocyte triglyceride lipase. Collectively, these data indicate that uterine Prx2 restrains uterine decidual differentiation through regulating lipid metabolism.

Maternal N-Carbamylglutamate Supplementation during Early Pregnancy Enhances Embryonic Survival and Development through Modulation of the Endometrial Proteome in Gilts

BACKGROUND

Early pregnancy loss is a major concern in humans and animals. N-carbamylglutamate (NCG) has been found to enhance embryonic survival during early pregnancy in rats. However, little is known about the key factors in the endometrium involved in the improvement of embryonic implantation and development induced by maternal NCG supplementation.

OBJECTIVES

Our objectives were to investigate whether NCG supplementation during early gestation enhanced embryonic survival and development in gilts and to uncover the related factors using the approach of endometrium proteome analysis with isobaric tags for relative and absolute quantification (iTRAQ).

METHODS

Uteruses and embryos/fetuses were obtained on days 14 and 28 of gestation from gilts fed a basal diet that was or was not supplemented with 0.05% NCG. The iTRAQ-based quantitative proteomics approach was performed to explore the endometrium proteome altered by NCG supplementation.

RESULTS

Maternal NCG supplementation significantly increased the number of total fetuses and live fetuses on day 28 of gestation by 1.32 and 1.29, respectively (P < 0.05), with a significant decrease in embryonic mortality (P < 0.05). iTRAQ results indicated that a total of 59 proteins showed at least 2-fold differences (P < 0.05), including 52 proteins that were present at higher abundance and 7 proteins present at lower abundance in NCG-supplemented gilts. The differentially expressed proteins primarily are involved in cell adhesion, energy metabolism, lipid metabolism, protein metabolism, antioxidative stress, and immune response. On day 14 of gestation, several proteins closely related to embryonic implantation and development, such as integrin-αv, integrin-β3, talin, and endothelial nitric oxide synthase, were upregulated (3.7-, 4.1-, 2.4-, and 5.4-fold increases, respectively) by NCG supplementation.

CONCLUSION

To our knowledge, our results provide the first evidence that altered abundance of the endometrial proteome induced by NCG supplementation is highly associated with the improvement of embryonic survival and development in gilts.

Control of regional decidualization in implantation: Role of FoxM1 downstream of Hoxa10 and cyclin D3

Appropriate regulation of regional uterine stromal cell decidualization in implantation, at the mesometrial triangle and secondary decidual zone (SDZ) locations, is critical for successful pregnancy, although the regulatory mechanisms remain poorly understood. In this regard, the available animal models that would specifically allow mechanistic analysis of site-specific decidualization are strikingly limited. Our study found that heightened expression of FoxM1, a Forkhead box transcription factor, is regulated during decidualization, and its conditional deletion in mice reveals failure of implantation with regional decidualization defects such as a much smaller mesometrial decidua with enlarged SDZ. Analysis of cell cycle progression during decidualization both in vivo and in vitro demonstrates that the loss of FoxM1 elicits diploid cell deficiency with enhanced arrests prior to mitosis and concomitant upregulation of polyploidy. We further showed that Hoxa10 and cyclin D3, two decidual markers, control transcriptional regulation and intra-nuclear protein translocation of FoxM1 in polyploid cells, respectively. Overall, we suggest that proper regional decidualization and polyploidy development requires FoxM1 signaling downstream of Hoxa10 and cyclin D3.

Claudin-3, claudin-7, and claudin-10 show different distribution patterns during decidualization and trophoblast invasion in mouse and human

Implantation of the mammalian embryo requires profound endometrial changes for successful pregnancy, including epithelial-mesenchymal transition of the luminal epithelium and stromal-epithelial transition of the stromal cells resulting in decidualization. Claudins (Cldn) determine the variability in tight junction paracellular permeability and may play a role during these epithelial and decidual changes. We here localized Cldn3, Cldn7 and Cldn10 proteins in the different compartments of murine endometrium up to day 8.5 of pregnancy (dpc) as well as in human endometrium and first trimester decidua. In murine estrous endometrium, luminal and glandular epithelium exhibited Cldn3 and Cldn7, whereas Cldn10 was only detectable in glandular epithelium. At 4.5 dpc, Cldn3 protein shifted to an apical localization, whereas Cldn7 vanished in the epithelium of the implantation chamber. At this stage, there was no stromal signal for Cldn3 and Cldn7, but a strong induction of Cldn10 in the primary decidual zone. Cldn3 proteins emerged at 5.5 dpc spreading considerably from 6.5 dpc onward in the endothelial cells of the decidual blood sinusoids and in the decidual cells of the compact antimesometrial region. In addition to Cldn3, Cldn10 was identified in human endometrial epithelia. Both proteins were not detected in human first trimester decidual cells. Cldn3 was shown in murine trophoblast giant cells as well as in human extravillous trophoblast cells and thus may have an impact on trophoblast invasion in both species. We here showed a specific claudin signature during early decidualization pointing to a role in decidual angiogenesis and regulation of trophoblast invasion.

Stress lowers the threshold dose at which bisphenol A disrupts blastocyst implantation, in conjunction with decreased uterine closure and e-cadherin

Exposure to stress can disrupt blastocyst implantation in inseminated female mice, and evidence implicates elevation of the female's estrogen:progesterone ratio. Exposure to the xenoestrogen, bisphenol A (BPA) can also disrupt implantation. Undisturbed control female CF-1 mice were compared to other females that were exposed to predators (rats) across a wire-mesh grid during gestation days (GD) 1-4, a procedure that elevates corticosterone but does not on its own disrupt implantation in this genetic strain. They were concurrently exposed to varied doses of BPA that on their own were below the threshold dose sufficient to disrupt implantation. On GD 6, we measured the number of intrauterine implantation sites and extracted their uteri, which subsequently were stained and analyzed for uterine luminal area and epithelial cadherin (e-cadherin), a molecule that causes uterine closure and adhesion of blastocysts to the uterine epithelium. The combination of rat-exposure stress and BPA significantly disrupted implantation and increased uterine luminal area, whereas either manipulation on its own did not. E-cadherin was significantly reduced by exposure to BPA, positively correlated with the number of implantation sites, and inversely correlated with luminal area. BPA exposure was also associated with nonmonotonic perturbation of urinary corticosterone concentrations and increased urinary estradiol concentrations on GD 6. These data are consistent with a potential summation of stress-induced estrogen and xenoestrogen activity.

Alkaline phosphatase protects lipopolysaccharide-induced early pregnancy defects in mice

Excessive cytokine inflammatory response due to chronic or superphysiological level of microbial infection during pregnancy leads to pregnancy complications such as early pregnancy defects/loss and preterm birth. Bacterial toxin lipopolysaccharide (LPS), long recognized as a potent proinflammatory mediator, has been identified as a risk factor for pregnancy complications. Alkaline phosphatase (AP) isozymes have been shown to detoxify LPS by dephosphorylation. In this study, we examined the role of alkaline phosphatase (AP) in mitigating LPS-induced early pregnancy complications in mice. We found that 1) the uterus prior to implantation and implantation sites following embryo implantation produce LPS recognition and dephosphorylation molecules TLR4 and tissue non-specific AP (TNAP) isozyme, respectively; 2) uterine TNAP isozyme dephosphorylates LPS at its sites of production; 3) while LPS administration following embryo implantation elicits proinflammatory cytokine mRNA levels at the embryo implantation sites (EISs) and causes early pregnancy loss, dephosphorylated LPS neither triggers proinflammatory cytokine mRNA levels at the EISs nor induces pregnancy complications; 4) AP isozyme supplementation to accelerate LPS detoxification attenuates LPS-induced pregnancy complications following embryo implantation. These findings suggest that a LPS dephosphorylation strategy using AP isozyme may have a unique therapeutic potential to mitigate LPS- or Gram-negative bacteria-induced pregnancy complications in at-risk women.