Notch2 controls prolactin and insulin-like growth factor binding protein-1 expression in decidualizing human stromal cells of early pregnancy

Notch signaling in reproduction

The Notch signaling pathway is conserved among mammalian species and controls proliferation, differentiation, and cell death in many organs throughout the body including the reproductive tract. Notch signaling plays critical roles in the development and function of both the male and female reproductive systems. Specifically, within the female reproductive tract, Notch signaling is hormone regulated and mediates key reproductive events important for ovarian and uterine function. In this review, we highlight the tissues that express Notch receptors, ligands, and downstream effectors and distinguish how these molecules regulate reproductive function in male and female mice, non-human primates, and humans. Finally, we describe some of the aberrations in Notch signaling in female reproductive pathologies and identify opportunities for future investigation.

Uterine Notch2 facilitates pregnancy recognition and corpus luteum maintenance via upregulating decidual Prl8a2

The maternal recognition of pregnancy is a necessary prerequisite for gestation maintenance through prolonging the corpus luteum lifespan and ensuring progesterone production. In addition to pituitary prolactin and placental lactogens, decidual derived prolactin family members have been presumed to possess luteotropic effect. However, there was a lack of convincing evidence to support this hypothesis. Here, we unveiled an essential role of uterine Notch2 in pregnancy recognition and corpus luteum maintenance. Uterine-specific deletion of Notch2 did not affect female fertility. Nevertheless, the expression of decidual Prl8a2, a member of the prolactin family, was downregulated due to Notch2 ablation. Subsequently, we interrupted pituitary prolactin function to determine the luteotropic role of the decidua by employing the lipopolysaccharide-induced prolactin resistance model, or blocking the prolactin signaling by prolactin receptor-Fc fusion protein, or repressing pituitary prolactin release by dopamine receptor agonist bromocriptine, and found that Notch2-deficient females were more sensitive to these stresses and ended up in pregnancy loss resulting from abnormal corpus luteum function and insufficient serum progesterone level. Overexpression of Prl8a2 in Notch2 knockout mice rescued lipopolysaccharide-induced abortion, highlighting its luteotropic function. Further investigation adopting Rbpj knockout and DNMAML overexpression mouse models along with chromatin immunoprecipitation assay and luciferase analysis confirmed that Prl8a2 was regulated by the canonical Notch signaling. Collectively, our findings demonstrated that decidual prolactin members, under the control of uterine Notch signaling, assisted pituitary prolactin to sustain corpus luteum function and serum progesterone level during post-implantation phase, which was conducive to pregnancy recognition and maintenance.

Progesterone secreted from the corpus luteum in the ovary is indispensable to pregnancy maintenance in both rodents and humans. Therefore, prolonged corpus luteum lifespan and sustainable progesterone production is a prerequisite for a successful pregnancy. In rodents, in addition to pituitary prolactin and placental lactogens, decidual derived factors have been presumed to possess luteotropic effects during the post-implantation stage. In this study, utilizing a mouse model with uterine specific deletion of Notch2, which displayed decreased level of decidual prolactin member Prl8a2, combined with multiple approaches to interrupt the pituitary prolactin signal, we demonstrated that decidual derived Prl8a2 assisted pituitary prolactin to sustain corpus luteum function and serum progesterone level during post-implantation phase, which was conducive to pregnancy recognition and maintenance. In addition, the expression of decidual Prl8a2 was under the direct control of the canonical Notch pathway. Together, we herein provide convincing evidence that decidual produced Prl8a2, modulated by uterine canonical Notch signaling, exhibits luteotropic functions and contributes to pregnancy maintenance.

Notch and Endometrial Cancer

The human endometrium is a unique, highly dynamic tissue that undergoes cyclic changes of cell proliferation, differentiation, and death. Endometrial cancer is the most common malignancy among women in developed countries. Importantly, the incidence of endometrial cancer is rising in high-income countries. Currently histological classification is used for subtyping of endometrial cancer, while ongoing research is evaluating markers for more accurate molecular classification. Evolutionary conserved Notch signaling pathway regulates diverse cellular processes such as proliferation, differentiation, and cell invasion. Accumulating evidence links aberrant Notch signaling with diseases such as hyperplasia and endometrial cancer. This chapter summarizes the current state of Notch signaling investigations in the endometrium, endometriosis, and endometrial cancer.

Notch1 is crucial for decidualization and maintaining the first pregnancy in the mouse†

The endometrium undergoes a pregnancy-delivery-repair cycle multiple times during the reproductive lifespan in females. Decidualization is one of the critical events for the success of this essential process. We have previously reported that Notch1 is essential for artificial decidualization in mice. However, in a natural pregnancy, the deletion of Notch1 (PgrCre/+Notch1f/f, or Notch1d/d) only affects female fertility in the first 30 days of a 6-month fertility test, but not the later stages. In the present study, we undertook a closer evaluation at the first pregnancy of these mice to attempt to understand this puzzling phenomenon. We observed a large number of pregnancy losses in Notch1d/d mice in their first pregnancy, which led to the subfertility observed in the first 30 days of the fertility test. We then demonstrated that the initial pregnancy loss is a consequence of impaired decidualization. Furthermore, we identified a group of genes that contribute to Notch1 regulated decidualization in a natural pregnancy. Gene ontogeny analysis showed that these differentially expressed genes in the natural pregnancy are involved in cell-cell and cell-matrix interactions, different from genes that have been previously identified from the artificial decidualization model, which contribute to cell proliferation and apoptosis. In summary, we determined that Notch1 is essential for normal decidualization in the mouse uterus only in the first pregnancy but not in subsequent ones.

Bisphenol compounds regulate decidualized stromal cells in modulating trophoblastic spheroid outgrowth and invasion in vitro†

Bisphenol A (BPA) is commonly found in epoxy resins used in the manufacture of plastic coatings in food packaging and beverage cans. There is a growing concern about BPA as a weak estrogenic compound that can affect human endocrine function. Chemicals structurally similar to BPA, such as bisphenol F (BPF) and bisphenol S (BPS), have been developed as substitutes in the manufacturing industry. Whether these bisphenol substitutes have adverse effects on human endocrine and reproductive systems remains largely unknown. This study investigated the effects of BPA, BPF, and BPS on regulating the function of decidualized human primary endometrial stromal cells on trophoblast outgrowth and invasion by indirect and direct co-culture models. All three bisphenols did not affect the stromal cell decidualization process. However, BPA- and BPF-treated decidualized stromal cells stimulated trophoblastic spheroid invasion in the indirect coculture model. The BPA-treated decidualized stromal cells had upregulated expressions of several invasion-related molecules including leukemia inhibitory factor (LIF), whereas both BPA- and BPF-treated decidualized stromal cells had downregulated expressions of anti-invasion molecules including plasminogen activator inhibitor type 1 (PAI-1) and tumor necrosis factor (TNFα) . Taken together, BPA and BPF altered the expression of invasive and anti-invasive molecules in decidualized stromal cells modulating its function on trophoblast outgrowth and invasion, which could affect the implantation process and subsequent pregnancy outcome.

Identification of loci associated with conception rate in primiparous Holstein cows

Background

Subfertility is a major issue facing the dairy industry as the average US Holstein cow conception rate (CCR) is approximately 35%. The genetics underlying the physiological processes responsible for CCR, the proportion of cows able to conceive and maintain a pregnancy at each breeding, are not well characterized. The objectives of this study were to identify loci, positional candidate genes, and transcription factor binding sites (TFBS) associated with CCR and determine if there was a genetic correlation between CCR and milk production in primiparous Holstein cows. Cows were bred via artificial insemination (AI) at either observed estrus or timed AI and pregnancy status was determined at day 35 post-insemination. Additive, dominant, and recessive efficient mixed model association expedited (EMMAX) models were used in two genome-wide association analyses (GWAA). One GWAA focused on CCR at first service (CCR1) comparing cows that conceived and maintained pregnancy to day 35 after the first AI (n = 494) to those that were open after the first AI (n = 538). The second GWAA investigated loci associated with the number of times bred (TBRD) required for conception in cows that either conceived after the first AI (n = 494) or repeated services (n = 472).

Results

The CCR1 GWAA identified 123, 198, and 76 loci associated (P < 5 × 10^− 08) in additive, dominant, and recessive models, respectively. The TBRD GWAA identified 66, 95, and 33 loci associated (P < 5 × 10^− 08) in additive, dominant, and recessive models, respectively. Four of the top five loci were shared in CCR1 and TBRD for each GWAA model. Many of the associated loci harbored positional candidate genes and TFBS with putative functional relevance to fertility. Thirty-six of the loci were validated in previous GWAA studies across multiple breeds. None of the CCR1 or TBRD associated loci were associated with milk production, nor was their significance with phenotypic and genetic correlations to 305-day milk production.

Conclusions

The identification and validation of loci, positional candidate genes, and TFBS associated with CCR1 and TBRD can be utilized to improve, and further characterize the processes involved in cattle fertility.

The Notch Family Transcription Factor, RBPJκ, Modulates Glucose Transporter and Ovarian Steroid Hormone Receptor Expression During Decidualization

During decidualization, endometrial stromal cells differentiate into a secretory phenotype to modulate the uterine microenvironment and promote embryo implantation. This highly metabolic process relies on ovarian steroid receptors and glucose transporters. Canonical Notch signaling is mediated by the transcription factor Recombination Signal Binding Protein for Immunoglobulin Kappa J Region (RBPJ). Loss of RBPJ in the mouse uterus (Pgr^cre/+Rbpj^flox/flox; Rbpj c-KO) results in subfertility in part due to an abnormal uterine-embryonic axis during implantation and, as described herein, decidualization failure. Induced in vivo decidualization in Rbpj c-KO mice was impaired with the downregulation of decidual markers and decreased progesterone receptor (Pgr) signaling. Consistent with in vivo mouse data, RBPJ knockdown during in vitro Human uterine fibroblast (HuF) cell decidualization results in the reduced expression of decidual marker genes along with PGR. Expression of the glucose transporter, SLC2A1, was decreased in the RBPJ-silenced HuF cells, which corresponded to decreased Slc2a1 in the secondary decidual zone of Rbpj c-KO mouse uteri. Exogenous administration of pyruvate, which bypasses the need for glucose, rescues PRL expression in RBPJ-deficient HuF cells. In summary, Notch signaling through RBPJ controls both ovarian steroid receptor PGR and glucose transporter SLC2A1 expression during decidualization, and this dysregulation likely contributes to embryo implantation failure.

Pregnancy-associated diamine oxidase originates from extravillous trophoblasts and is decreased in early-onset preeclampsia

Human extravillous trophoblast (EVT) invasion of the pregnant uterus constitutes a pivotal event for the establishment of the maternal-fetal interface. Compromised EVT function manifesting in inadequate arterial remodeling is associated with the severe pregnancy disorder early-onset preeclampsia (eoPE). Recent studies suggest that EVTs invade the entire uterine vasculature including arteries, veins and lymphatics in the first trimester of pregnancy. We therefore hypothesized that EVT-derived factors accumulate in the circulation of pregnant women early in gestation and may serve to predict eoPE. In contrast to published literature, we demonstrate that placenta-associated diamine oxidase (DAO) is not expressed by maternal decidual cells but solely by EVTs, especially when in close proximity to decidual vessels. Cultures of primary EVTs express and secret large amounts of bioactive DAO. ELISA measurements indicate a pregnancy-specific rise in maternal DAO plasma levels around gestational week (GW) 7 coinciding with vascular invasion of EVTs. Strikingly, DAO levels from eoPE cases were significantly lower (40%) compared to controls in the first trimester of pregnancy but revealed no difference at mid gestation. Furthermore, DAO-containing pregnancy plasma rapidly inactivates pathophysiologically relevant histamine levels. This study represents the first proof of concept suggesting EVT-specific signatures as diagnostic targets for the prediction of eoPE.

Diverse endometrial mRNA signatures during the window of implantation in patients with repeated implantation failure

High endometrial receptivity in the window of implantation (WOI) is essential for successful implantation. However, a diagnostic tool with high specificity for impaired endometrial receptivity remains to be developed. We collected endometrium specimens during the WOI from patients with RIF and women who conceived after one IVF/ICSI attempt. We conducted mRNA microarray on the samples followed by relevant comparative and functional analysis. Microarray analysis revealed 357 dysregulated mRNAs between the two groups. The majority of these mRNAs were found to encode membrane proteins by Gene Ontology (GO) analysis. The major functional biological pathways associated with the down-regulated mRNAs were cytokine-cytokine receptor interaction, the p53 signalling pathway and the complement and coagulation cascades. Up-regulated mRNAs were found mainly to participate in pathways such as PPAR signalling, hematopoietic cell lineage, phosphatidylinositol signalling system, ECM-receptor interaction and notch signalling. AQP3, DPP4 and TIMP3 whose expression patterns were down-regulated in RIF patients both by microarray and real-time PCR had a high correspondence with previous studies demonstrating that these genes may contribute to the defects in endometrial receptivity in RIF patients. Overall, these RIF-associated mRNAs may help devise new diagnostic tools for endometrial receptivity.

Notch signalling in placental development and gestational diseases

Activation of Notch signalling upon cell-cell contact of neighbouring cells controls a plethora of cellular processes such as stem cell maintenance, cell lineage determination, cell proliferation, and survival. Accumulating evidence suggests that the pathway also critically regulates these events during placental development and differentiation. Herein, we summarize our present knowledge about Notch signalling in murine and human placentation and discuss its potential role in the pathophysiology of gestational disorders. Studies in mice suggest that Notch controls trophectoderm formation, decidualization, placental branching morphogenesis and endovascular trophoblast invasion. In humans, the particular signalling cascade promotes formation of the extravillous trophoblast lineage and regulates trophoblast proliferation, survival and differentiation. Expression patterns as well as functional analyses indicate distinct roles of Notch receptors in different trophoblast subtypes. Altered effects of Notch signalling have been detected in choriocarcinoma cells, consistent with its role in cancer development and progression. Moreover, deregulation of Notch signalling components were observed in pregnancy disorders such as preeclampsia and fetal growth restriction. In summary, Notch plays fundamental roles in different developmental processes of the placenta. Abnormal signalling through this pathway could contribute to the pathogenesis of gestational diseases with aberrant placentation and trophoblast function.

Placental methylome analysis from a prospective autism study

Background

Autism spectrum disorders (ASD) are increasingly prevalent neurodevelopmental disorders that are behaviorally diagnosed in early childhood. Most ASD cases likely arise from a complex mixture of genetic and environmental factors, an interface where the epigenetic marks of DNA methylation may be useful as risk biomarkers. The placenta is a potentially useful surrogate tissue characterized by a methylation pattern of partially methylated domains (PMDs) and highly methylated domains (HMDs) reflective of methylation patterns observed in the early embryo.

Methods

In this study, we investigated human term placentas from the MARBLES (Markers of Autism Risk in Babies: Learning Early Signs) prospective study by whole genome bisulfite sequencing. We also examined the utility of PMD/HMDs in detecting methylation differences consistent with ASD diagnosis at age three.

Results

We found that while human placental methylomes have highly reproducible PMD and HMD locations, there is a greater variation between individuals in methylation levels over PMDs than HMDs due to both sampling and individual variability. In a comparison of methylation differences in placental samples from 24 ASD and 23 typically developing (TD) children, a HMD containing a putative fetal brain enhancer near DLL1 was found to reach genome-wide significance and was validated for significantly higher methylation in ASD by pyrosequencing.

Conclusions

These results suggest that the placenta could be an informative surrogate tissue for predictive ASD biomarkers in high-risk families.

Electronic supplementary material

The online version of this article (doi:10.1186/s13229-016-0114-8) contains supplementary material, which is available to authorized users.

Wingless ligand 5a is a critical regulator of placental growth and survival

The maternal uterine environment is likely critical for human placental morphogenesis and development of its different trophoblast subtypes. However, factors controlling growth and differentiation of these cells during early gestation remain poorly elucidated. Herein, we provide evidence that the ligand Wnt5a could be a critical regulator of trophoblast proliferation and survival. Immunofluorescence of tissues and western blot analyses of primary cultures revealed abundant Wnt5a expression and secretion from first trimester decidual and villous stromal cells. The ligand was also detectable in decidual glands, macrophages and NK cells. Wnt5a increased proliferation of villous cytotrophoblasts and cell column trophoblasts, outgrowth on collagen I as well as cyclin A and D1 expression in floating explant cultures, but suppressed camptothecin-induced apoptosis. Similarly, Wnt5a stimulated BrdU incorporation and decreased caspase-cleaved cytokeratin 18 neo-epitope expression in primary cytotrophoblasts. Moreover, Wnt5a promoted activation of the MAPK pathway in the different trophoblast models. Chemical inhibition of p42/44 MAPK abolished cyclin D1 expression and Wnt5a-stimulated proliferation. Compared to controls, MAPK phosphorylation and proliferation of cytotrophoblasts declined upon supplementation of supernatants from Wnt5a gene-silenced decidual or villous stromal cells. In summary, non-canonical Wnt5a signalling could play a role in early human trophoblast development by promoting cell proliferation and survival.

Aberrant activation of canonical Notch1 signaling in the mouse uterus decreases progesterone receptor by hypermethylation and leads to infertility

In mammalian reproduction, implantation is one of the most critical events. Failure of implantation and the subsequent decidualization contribute to more than 75% of pregnancy losses in women. Our laboratory has previously reported that inhibition of Notch signaling results in impaired decidualization in both women and a transgenic mouse model. In this study, we generated a Notch gain-of-function transgenic mouse by conditionally overexpressing the Notch1 intracellular domain (N1ICD) in the reproductive tract driven by a progesterone receptor (Pgr) -Cre. We show that the overexpression of N1ICD in the uterus results in complete infertility as a consequence of multiple developmental and physiological defects, including the absence of uterine glands and dysregulation of progesterone and estrogen signaling by a Recombination Signal Binding Protein Jκ-dependent signaling mechanism. We further show that the inhibition of progesterone signaling is caused by hypermethylation of its receptor Pgr by Notch1 overexpression through the transcription factor PU.1 and DNA methyltransferase 3b (Dnmt3b). We have generated a mouse model to study the consequence of increased Notch signaling in female reproduction and provide the first evidence, to our knowledge, that Notch signaling can regulate epigenetic modification of the Pgr.

Expression pattern and function of Notch2 in different subtypes of first trimester cytotrophoblast

Introduction

Notch signalling has been shown to control cytotrophoblast (CTB) proliferation, differentiation and motility suggesting that the conserved signalling pathway could be critical for human placental development. Since individual Notch receptors have not been elucidated, we herein investigated expression pattern and function of Notch2 in different first trimester trophoblast subpopulations.

Methods

Localisation of Notch2 was analysed in first trimester placental and decidual tissues using immunofluorescence. Notch2 transcript and protein levels were studied by qRT-PCR and Western blotting in proliferative EGF receptor (EGFR)⁺ and differentiated HLA-G⁺ CTBs, respectively, isolated from early placentae by MACS. CTB migration through fibronectin-coated transwells as well as proliferation (EdU labelling) in floating villous explant cultures and primary CTBs were investigated in the presence of Notch2 siRNAs or specific antibodies blocking Notch2 cleavage.

Results

In tissue sections Notch2 expression was higher in HLA-G⁺ distal cell column trophoblasts (dCCTs) compared to proximal CCTs. Accordingly, expression of Notch2 mRNA and protein were elevated in isolated HLA-G⁺ CTBs compared to EGFR⁺ CTBs. Notch2 was also detectable in interstitial CTBs as well as in intramural CTBs associated with maternal decidual vessels. Antibody-mediated inhibition of Notch2 signalling did not affect proliferation, but increased migration of SGHPL-5 cells and primary CTBs. Similarly, Notch2 siRNA treatment promoted trophoblast motility.

Discussion

Notch2 is present in differentiated cells of the extravillous trophoblast lineage, such as dCCTs, interstitial and intramural CTBs, suggesting diverse roles of the particular receptor. Notch2 signalling, activated by cell–cell contact of neighbouring dCCTs, could attenuate trophoblast migration.

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Notch2 is induced during EVT differentiation.

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Notch2 in interstitial trophoblasts could regulate cross-talk with decidual cells.

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Notch2 expressed by intramural trophoblasts may play a role in vessel remodelling.

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Notch2 impairs trophoblast migration in vitro.