Regulation of the PI3K/Akt pathway during decidualization of endometrial stromal cells

The roles of AKT isoforms in decidualization and embryo implantation using a Progesterone Receptor-Cre mouse model†

Implantation is a complex process requiring a prepared, receptive endometrium, reliant on synchronized decidualization of stromal cells. During this process, cell proliferation and apoptosis are tightly regulated by signaling factors, including the survival and proliferation of the PI3K/AKT pathway. The three AKT isoforms each play distinct physiological roles, but their specific functions in endometrial cell survival and apoptosis remain unclear. We hypothesize that for successful implantation, each AKT isoform has distinct roles in the endometrium during decidualization, which varies throughout the process. To explore this, we developed a unique PGR-Cre tissue-specific mouse model with single and combined knockouts (KO) of each AKT isoform. Using artificial decidualization during pseudopregnancy and normal gestation, we investigated the specific activity of each AKT isoform and their downstream targets to assess the role of AKT pathway. Our results showed that the AKT1-2 KO genotype failed to decidualize during pseudopregnancy and exhibited a reduced number of implantation sites. Interestingly, AKT3 was hyperphosphorylated in the AKT1-2 KO mice and emerged as the primary isoform active throughout decidualization, specifically signaling through GSK3B. This study suggests distinct yet partially redundant roles for AKT1 and AKT2 during decidualization and embryo implantation. We propose that the AKT pathway plays significant role in fertility, and a deeper understanding of its involvement in decidualization could lead to improved strategies for addressing fertility issues. These findings highlight the importance of AKT activity in the cellular and molecular regulation of mouse fertility.

Adenomyosis-associated infertility: an update of the immunological perspective

Adenomyosis is characterized by the invasion of endometrial glands and stroma into the myometrium. Its clinical manifestations often include dysmenorrhoea, excessive menstrual bleeding and infertility. Reduced pregnancy and live birth rates and an increased miscarriage rate are observed in women with adenomyosis. This review summarizes relevant advances and presents the underlying mechanisms of adenomyosis-associated infertility from an immunological perspective. Individuals with adenomyosis exhibit imbalances in immune cell subpopulations and the endocrine hormone-immunomodulatory axis. These immunological alterations may be key contributors to, or at least accomplices in, impaired endometrial receptivity. In addition, adenomyosis often occurs in association with endometriosis, uterine leiomyoma or endometrial polyps, which are pathogenetically relevant; their similarities and differences are discussed from an immunological perspective. The clinical diagnostic criteria of adenomyosis are not perfect, and the pathogenesis remains to be fully explored. Therefore screening for effective targets for early diagnosis and treatment at the cellular and molecular levels from the immunological point of view holds great potential, which will be of great importance in preventing this disease and improving women's reproductive health.

Decidual Disrupting Effects of Low-Dose Benzophenone-Type UV Filters in Human Endometrial Stromal Cells via ER/PR/FOXO1 Signaling

Exposure to endocrine disrupting chemicals (EDCs), particularly benzophenone (BP)-type UV filters, has been epidemiologically linked to endometrium-related reproductive risks in women. However, their effects on hormone-driven endometrial events and key receptor signaling at the human cellular level remain unexplored. Herein, using human primary endometrial stromal cells (HESCs), we investigated the disrupting effects of five BP congeners and deciphered the underlying mechanism on decidualization, a functional change of the endometrium preparing for pregnancy. BP-8, its two metabolites, BP-3, and BP-1 at 10 nM significantly disrupted progesterone-dependent decidualization in HESCs, marked by 1.5-1.8-fold and 2.2-2.6-fold upregulation of IGFBP-1 and LEFTY, respectively. Decidual transcriptional activators, WNT-FOXO1, were significantly induced by BPs, which are implicated in G2 phase cell arrest (from 3.26% to 8.93%) and apoptosis (from 12.29% to 25.61%). Mechanistically, the inhibition of estrogen receptor α (ERα) effectively alleviated these decidual disrupting effects. BPs increased the transcription of ERα and progesterone receptor (PR) signaling and enhanced nuclear translocation and interaction between ERα and PR during decidualization. The ERα-mediated enhancement of PR signaling activity by BPs was further validated in progesterone response element-luciferase transfected cells. Collectively, our findings elucidate the molecular pathway through which BPs disrupt endometrial decidualization via ERα/PR/FOXO1, providing critical mechanistic insights for the reproductive risk assessment of BPs and structurally related EDCs.

Investigating Aging-Related Endometrial Dysfunction Using Endometrial Organoids

Ageing of the endometrium is a critical factor that affects reproductive health, yet its intricate mechanisms remain poorly explored. In this study, we performed transcriptome profiling and experimental verification of endometrium and endometrial organoids from young and advanced age females, to elucidate the underlying mechanisms and to explore novel treatment strategies for endometrial ageing. First, we found that age-associated decline in endometrial functions including fibrosis and diminished receptivity, already exists in reproductive age. Subsequently, based on RNA-seq analysis, we identified several changes in molecular processes affected by age, including fibrosis, imbalanced inflammatory status including Th1 bias in secretory phase, cellular senescence and abnormal signalling transduction in key pathways, with all processes been further validated by molecular experiments. Finally, we uncovered for the first time that PI3K-AKT-FOXO1 signalling pathway is overactivated in ageing endometrium and is closely correlated with fibrosis and impaired receptivity characteristics of ageing endometrium. Blocking or activation of PI3K by LY294002 or 740Y-P could attenuate the effect of ageing or accelerate dysfunction of endometrial organoids. This discovery is expected to bring new breakthroughs for understanding the pathophysiological processes associated with endometrial ageing, as well as treatment strategies to improve reproductive outcomes in women of advanced reproductive age.

Dead or Alive: Exploratory Analysis of Selected Apoptosis- and Autophagy-Related Proteins in Human Endometrial Stromal Cells of Fertile Females and Their Potential Role During Embryo Implantation

To date, very little is known about how apoptosis and autophagy affect human endometrial stromal cells (ESCs), particularly how these processes might determine the depth of implantation in humans. Before investigating how apoptosis and autophagy might modulate the implantation process in an infertile population, it is necessary to clarify how these processes are regulated in healthy individuals. This study examined the protein expression related to apoptosis and autophagy in primary ESCs from fertile women, particularly in the context of decidualization and embryo contact, using Western blot analysis. This study evaluated the protein expression of apoptosis receptors and autophagy markers during the window of implantation. Previous research has shown that a syndecan 1 (Sdc1) knockdown (kd) in endometrial stromal cell lines increased the sensitivity to apoptosis induced by embryonic stimuli. We aimed to determine if this effect is also present in primary cells and if Sdc1 regulates autophagy. The expression of autophagy- and apoptosis-associated proteins in primary ESCs from fertile individuals was investigated in this preliminary study, along with their impact on the process of human embryo implantation. During decidualization and exposure to embryo contact, we observed an upregulation of apoptosis- and autophagy-related proteins in ESCs. Decidualized ESCs exhibited higher levels of apoptosis receptors, indicating increased sensitivity to embryo-induced apoptosis. Additionally, the increase in basal autophagy proteins suggests a significant role in the implantation process. Sdc1 is potentially involved in regulating apoptosis and autophagy, demonstrating its possible role in modulating implantation-related cell activities. These findings suggest a complex interplay between apoptosis and autophagy in regulating human embryo implantation. The changes in the expression of apoptotic and autophagic proteins in ESCs after decidualization and upon contact with the embryo provide new insights into the cellular mechanisms that underlie successful implantation. These results have potential implications for understanding the pathophysiology of implantation disorders and improving assisted reproductive technologies. The first results of this pilot study need to be verified with a larger sample size in the future.

PAI-1 promotes human endometrial stromal decidualization via inhibiting VEGFR2/PI3K/AKT signaling pathway mediated F-actin reorganization

Decidualization of endometrial stromal cells is a prerequisite for successful embryo implantation and early pregnancy. Decidualization dysregulation results in implantation failure. In our previous study, we reported that PAI-1 is abnormally downregulated in the endometrial tissue samples of patients with recurrent implantation failure. This study will explore the dynamic expression changes of PAI-1 in the endometrium during the menstrual cycle and its molecular mechanism affecting endometrial decidualization. Our findings indicated that the abundance of PAI-1 increased in the mid-secretory phase and attached a peak in the decidual phase in the endometrium of women with regular menstrual cycles. In human endometrial stromal cells (HESCs), PAI-1 knockdown attenuated endometrial decidualization by upregulating VEGFR2/PI3K/AKT signaling pathway and impaired the F-actin reorganization. Furthermore, axitinib (a VEGFR2 inhibitor) was used to inhibit the VEGFR2 protein activity and the results suggested that it eliminated the effects of PAI-1 on PI3K/AKT signaling pathways and F-actin remodeling. In addition, the interaction between PAI-1 and KNG1 was confirmed by coimmunoprecipitation assay in HESCs. Altogether, PAI-1-KNG1 may enhance the decidualization of endometrium by inhibiting VEGFR2/PI3K/AKT signaling pathway-mediated F-actin reorganization in healthy females.

The landscape of N1-methyladenosine (m1A) modification in mRNA of the decidua in severe preeclampsia

Recent discoveries in mRNA modification have highlighted N1-methyladenosine (m1A), but its role in preeclampsia (PE) pathogenesis remains unclear. In this study, we utilized methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) to identify m1A peaks and the expression profile of mRNA in the decidua of humans with early-onset PE (EPE), late-onset PE (LPE), and normal pregnancy (NP). We assessed the m1A modification patterns in preeclamptic decidua using 10 m1A modulators. Our bioinformatic analysis focused on differentially methylated mRNAs (DMGs) and differentially expressed mRNAs (DEGs) in pairwise comparisons of EPE vs. NP, LPE vs. NP, and EPE vs. LPE, as well as m1A-related DEGs. The comparisons of EPE vs. NP, LPE vs. NP, and EPE vs. LPE identified 3110, 2801, and 2818 DMGs, respectively. We discerned three different m1A modification patterns from this data. Further analysis revealed that key PE-related DMGs and m1A-related DEGs predominantly influence signaling pathways critical for decidualization, including cAMP, MAPK, PI3K-Akt, Notch, and TGF-β pathways. Additionally, these modifications impact pathways related to vascular smooth muscle contraction, estrogen signaling, and relaxin signaling, contributing to vascular dysfunction. Our findings demonstrate that preeclamptic decidua exhibits unique mRNA m1A modification patterns and gene expression profiles that significantly alter signaling pathways essential for both decidualization and vascular dysfunction. These differences in m1A modification patterns provide valuable insights into the molecular mechanisms influencing the decidualization process and vascular function in the pathogenesis of PE. These m1A modification regulators could potentially serve as potent biomarkers or therapeutic targets for PE, warranting further investigation.

Quercetin enhances decidualization through AKT-ERK-p53 signaling and supports a role for senescence in endometriosis

BACKGROUND

Patients with endometriosis suffer with chronic pelvic pain and infertility, and from the lack of pharmacologic therapies that consistently halt disease progression. Differences in the endometrium of patients with endometriosis vs. unaffected controls are well-documented. Specifically, shed endometrial tissues (delivered to the pelvic cavity via retrograde menstruation) reveal that a subset of stromal cells exhibiting pro-inflammatory, pro-fibrotic, and pro-senescence-like phenotypes is enhanced in endometriosis patients compared to controls. Additionally, cultured biopsy-derived endometrial stromal cells from endometriosis patients exhibit impaired decidualization, a defined differentiation process required for human embryo implantation and pregnancy. Quercetin, a senolytic agent, shows therapeutic potential for pulmonary fibrosis, a disorder attributed to senescent pulmonary fibroblasts. In rodent models of endometriosis, quercetin shows promise, and quercetin improves decidualization in vitro. However, the exact mechanisms are not completely understood. Therefore, we investigated the effects of quercetin on menstrual effluent-derived endometrial stromal cells from endometriosis patients and unaffected controls to define the signaling pathways underlying quercetin's effects on endometrial stromal cells.

METHODS

Menstrual effluent-derived endometrial stromal cells were collected and cultured from unaffected controls and endometriosis patients and then, low passage cells were treated with quercetin (25 µM) under basal or standard decidualization conditions. Decidualization responses were analyzed by measuring the production of IGFBP1 and PRL. Also, the effects of quercetin on intracellular cAMP levels and cellular oxidative stress responses were measured. Phosphokinase arrays, western blotting, and flow cytometry methods were performed to define the effects of quercetin on various signaling pathways and the potential mechanistic roles of quercetin.

RESULTS

Quercetin significantly promotes decidualization of control- and endometriosis-endometrial stromal cells. Quercetin substantially reduces the phosphorylation of multiple signaling molecules in the AKT and ERK1/2 pathways, while enhancing the phosphorylation of p53 and total p53 levels. Furthermore, p53 inhibition blocks decidualization while p53 activation promotes decidualization. Finally, we provide evidence that quercetin increases apoptosis of endometrial stromal cells with a senescent-like phenotype.

CONCLUSIONS

These data provide insight into the mechanisms of action of quercetin on endometrial stromal cells and warrant future clinical trials to test quercetin and other senolytics for treating endometriosis.

Targeting a mTOR/autophagy axis: a double-edged sword of rapamycin in spontaneous miscarriage

Immune dysfunction is a primary culprit behind spontaneous miscarriage (SM). To address this, immunosuppressive agents have emerged as a novel class of tocolytic drugs, modulating the maternal immune system's tolerance towards the embryo. Rapamycin (PubChem CID:5284616), a dual-purpose compound, functions as an immunosuppressive agent and triggers autophagy by targeting the mTOR pathway. Its efficacy in treating SM has garnered significant research interest in recent times. Autophagy, the cellular process of self-degradation and recycling, plays a pivotal role in numerous health conditions. Research indicates that autophagy is integral to endometrial decidualization, trophoblast invasion, and the proper functioning of decidual immune cells during a healthy pregnancy. Yet, in cases of SM, there is a dysregulation of the mTOR/autophagy axis in decidual stromal cells or immune cells at the maternal-fetal interface. Both in vitro and in vivo studies have highlighted the potential benefits of low-dose rapamycin in managing SM. However, given mTOR's critical role in energy metabolism, inhibiting it could potentially harm the pregnancy. Moreover, while low-dose rapamycin has been deemed safe for treating recurrent implant failure, its potential teratogenic effects remain uncertain due to insufficient data. In summary, rapamycin represents a double-edged sword in the treatment of SM, balancing its impact on autophagy and immune regulation. Further investigation is warranted to fully understand its implications.

Fetal growth restriction and placental defects in obese mice are associated with impaired decidualisation: the role of increased leptin signalling modulators SOCS3 and PTPN2

Decidualisation of the endometrium is a key event in early pregnancy, which enables embryo implantation. Importantly, the molecular processes impairing decidualisation in obese mothers are yet to be characterised. We hypothesise that impaired decidualisation in obese mice is mediated by the upregulation of leptin modulators, the suppressor of cytokine signalling 3 (SOCS3) and the protein tyrosine phosphatase non-receptor type 2 (PTPN2), together with the disruption of progesterone (P4)-signal transducer and activator of transcription (STAT3) signalling. After feeding mice with chow diet (CD) or high-fat diet (HFD) for 16 weeks, we confirmed the downregulation of P4 and oestradiol (E2) steroid receptors in decidua from embryonic day (E) 6.5 and decreased proliferation of stromal cells from HFD. In vitro decidualised mouse endometrial stromal cells (MESCs) and E6.5 deciduas from the HFD showed decreased expression of decidualisation markers, followed by the upregulation of SOCS3 and PTPN2 and decreased phosphorylation of STAT3. In vivo and in vitro leptin treatment of mice and MESCs mimicked the results observed in the obese model. The downregulation of Socs3 and Ptpn2 after siRNA transfection of MESCs from HFD mice restored the expression level of decidualisation markers. Finally, DIO mice placentas from E18.5 showed decreased labyrinth development and vascularisation and fetal growth restricted embryos. The present study revealed major defects in decidualisation in obese mice, characterised by altered uterine response to E2 and P4 steroid signalling. Importantly, altered hormonal response was associated with increased expression of leptin signalling modulators SOCS3 and PTPN2. Elevated levels of SOCS3 and PTPN2 were shown to molecularly affect decidualisation in obese mice, potentially disrupting the STAT3-PR regulatory molecular hub.

PI3K/AKT signaling alters glucose metabolism in uterine microenvironment of women with idiopathic recurrent spontaneous miscarriage

BACKGROUND

This study aims to identify metabolomic signatures in uterine fluid of women with idiopathic recurrent spontaneous miscarriage (IRSM) during window of implantation (WOI). Also, glucose transporters GLUT3 and GLUT4 and proteins of PI3K-Akt signaling pathway in endometrial tissue are assessed.

METHODS

Paired uterine fluid and endometrial biopsies were collected during WOI from women with IRSM (n = 24) and healthy women with azoospermic male partners as controls (n = 15). NMR metabolomics was used to identify the dysregulated metabolites in uterine fluid of IRSM women. Additionally, proteins and glucose transporters were investigated in the endometrial tissue using immunohistochemistry (IHC) and western blotting.

RESULTS

Uterine fluid metabolomics indicated eleven metabolites to be significantly downregulated in IRSM. While expression levels of PI3K (p85), PI3K (p110), p-Akt (Thr308), p-Akt (Ser473), GLUT3 and GLUT4 were significantly downregulated in endometrial tissue of these women, p-IKK α/β (Ser176/180) and p-NFkBp65 (Ser536) were significantly increased.

CONCLUSION

Our findings suggest that dysregulation of PI3K/Akt pathway in the uterine microenvironment could be a likely cause of endometrial dysfunction, thereby affecting implantation. Further studies on the downstream effects of the Akt signaling pathway in-vitro for improved understanding of the Akt-mediated cellular responses in IRSM is, therefore, warranted.

Oxidative Stress and the Nrf2/PPARγ Axis in the Endometrium: Insights into Female Fertility

Successful pregnancy depends on precise molecular regulation of uterine physiology, especially during the menstrual cycle. Deregulated oxidative stress (OS), often influenced by inflammatory changes but also by environmental factors, represents a constant threat to this delicate balance. Oxidative stress induces a reciprocally regulated nuclear factor erythroid 2-related factor 2/peroxisome proliferator-activated receptor-gamma (Nrf2/PPARγ) pathway. However, increased PPARγ activity appears to be a double-edged sword in endometrial physiology. Activated PPARγ attenuates inflammation and attenuates OS to restore redox homeostasis. However, it also interferes with physiological processes during the menstrual cycle, such as hormonal signaling and angiogenesis. This review provides an elucidation of the molecular mechanisms that support the interplay between PPARγ and OS. Additionally, it offers fresh perspectives on the Nrf2/PPARγ pathway concerning endometrial receptivity and its potential implications for infertility.

Long-chain acyl-CoA synthetase-4 regulates endometrial decidualization through a fatty acid β-oxidation pathway rather than lipid droplet accumulation

OBJECTIVE

Lipid metabolism plays an important role in early pregnancy, but its effects on decidualization are poorly understood. Fatty acids (FAs) must be esterified by fatty acyl-CoA synthetases to form biologically active acyl-CoA in order to enter the anabolic and/or catabolic pathway. Long-chain acyl-CoA synthetase 4 (ACSL4) is associated with female reproduction. However, whether it is involved in decidualization is unknown.

METHODS

The expression of ACSL4 in human and mouse endometrium was detected by immunohistochemistry. ACSL4 levels were regulated by the overexpression of ACSL4 plasmid or ACSL4 siRNA, and the effects of ACSL4 on decidualization markers and morphology of endometrial stromal cells (ESCs) were clarified. A pregnant mouse model was established to determine the effect of ACSL4 on the implantation efficiency of mouse embryos. Modulation of ACSL4 detects lipid anabolism and catabolism.

RESULTS

Through examining the expression level of ACSL4 in human endometrial tissues during proliferative and secretory phases, we found that ACSL4 was highly expressed during the secretory phase. Knockdown of ACSL4 suppressed decidualization and inhibited the mesenchymal-to-epithelial transition induced by MPA and db-cAMP in ESCs. Further, the knockdown of ACSL4 reduced the efficiency of embryo implantation in pregnant mice. Downregulation of ACSL4 inhibited FA β-oxidation and lipid droplet accumulation during decidualization. Interestingly, pharmacological and genetic inhibition of lipid droplet synthesis did not affect FA β-oxidation and decidualization, while the pharmacological and genetic inhibition of FA β-oxidation increased lipid droplet accumulation and inhibited decidualization. In addition, inhibition of β-oxidation was found to attenuate the promotion of decidualization by the upregulation of ACSL4. The decidualization damage caused by ACSL4 knockdown could be reversed by activating β-oxidation.

CONCLUSIONS

Our findings suggest that ACSL4 promotes endometrial decidualization by activating the β-oxidation pathway. This study provides interesting insights into our understanding of the mechanisms regulating lipid metabolism during decidualization.

Effect of beta-cypermethrin on the reproductive capacity of female mice in advanced age

The aim of the present study was to investigate whether exposure to pesticides beta-cypermethrin (β-CYP) harms the reproductive capacity of advanced-age female mice. The results evidenced that peri-implantation β-CYP exposure significantly reduced the number of fetuses per advanced-age female in the first litter, and the number and weight of implantation sites. The levels of decidualization markers were significantly reduced in β-CYP-administered advanced-age mice. Lower expression of Pcna, Cdk6, Foxo1, Ki67, and p62 protein and mRNA was found in the decidua of β-CYP-treated advanced-age mice. The levels of Bax, cleaved caspase-3, Lc3a/b, Atg, mTOR, and p-mTOR protein, and the ratio of p-mTOR/mTOR protein expression were clearly downregulated by peri-implantation β-CYP exposure. These results indicated that peri-implantation β-CYP exposure may elevate the decline in reproductive capacity of early pregnant mice in advanced age.

Focusing on the role of protein kinase mTOR in endometrial physiology and pathology: insights for therapeutic interventions

The mammalian target of rapamycin (mTOR) is a serine/threonine protein kinase crucial for cellular differentiation, proliferation, and autophagy. It shows a complex role in the endometrium, influencing both normal and pathogenic conditions. mTOR promotes the growth and maturation of endometrial cells, enhancing endometrial receptivity and decidualization. However, it also contributes to the development of endometriosis (EMs) and endometrial cancer (EC), thus emerging as a therapeutic target for these conditions. In this review, we summarize recent research progress on the mTOR signalling pathway in the endometrium. This provides insights into female endometrial structure and function and guides the prevention and treatment of related diseases.

The Role of Catestatin in Preeclampsia

Preeclampsia (PE) is a unique pregnancy disorder affecting women across the world. It is characterized by the new onset of hypertension with coexisting end-organ damage. Although the disease has been known for centuries, its exact pathophysiology and, most importantly, its prevention remain elusive. The basis of its associated molecular changes has been attributed to the placenta and the hormones regulating its function. One such hormone is chromogranin A (CgA). In the placenta, CgA is cleaved to form a variety of biologically active peptides, including catestatin (CST), known inter alia for its vasodilatory effects. Recent studies indicate that the CST protein level is diminished both in patients with hypertension and those with PE. Therefore, the aim of the present paper is to review the most recent and most relevant in vitro, in vivo, and clinical studies to provide an overview of the proposed impact of CST on the molecular processes of PE and to consider the possibilities for future experiments in this area.

Non-coding RNAs in Recurrent implantation failure

Recurrent implantation failure (RIF), defined as the inability to achieve conception following multiple consecutive in-vitro fertilization (IVF) attempts, represents a complex and multifaceted challenge in reproductive medicine. The emerging role of non-coding RNAs in RIF etiopathogenesis has only gained prominence over the last decade, illustrating a new dimension to our understanding of the intricate network underlying RIF. Successful embryo implantation demands a harmonious synchronization between an adequately decidualized endometrium, a competent blastocyst, and effective maternal-embryonic interactions. Emerging evidence has clarified the involvement of a sophisticated network of non-coding RNAs, including microRNAs, circular RNAs, and long non-coding RNAs, in orchestrating these pivotal processes. Disconcerted expression of these molecules can disrupt the delicate equilibrium required for implantation, amplifying the risk of RIF. This comprehensive review presents an in-depth investigation of the complex role played by non-coding RNAs in the pathogenesis of RIF. Furthermore, it underscores the vast potential of non-coding RNAs as diagnostic biomarkers and therapeutic targets, with the ultimate goal of enhancing implantation success rates in IVF cycles. As ongoing research continues to unravel the intercalated web of molecular interactions, exploiting the power of non-coding RNAs may offer promising avenues for mitigating the challenges posed by RIF and improving the outcomes of assisted reproduction.

Gene pathway analysis of the endometrium at the start of the window of implantation in women with unexplained infertility and unexplained recurrent pregnancy loss: is unexplained recurrent pregnancy loss a subset of unexplained infertility?

This study aims to understand differences/similarities in the genetic profile of the endometrium at the start of window of implantation (WOI) in women with unexplained infertility (UI) and unexplained recurrent pregnancy loss (uRPL). Differentially expressed genes (DEGs) from the endometrium were evaluated using gene expression array and pathway enrichment analysis was performed to analyse gene expression pathways involved in both conditions. We found 2,171 genes arranged in 117 pathways and 730 genes arranged in 33 pathways differentially expressed in endometrium of patients in UI and uRPL, respectively. Complement-coagulation cascades, morphine addiction pathway, and PI3K-Akt signalling pathway were predominantly differentially expressed in UI. Cancer pathways, NF-κB signalling pathway, and actin cytoskeleton regulation pathway showed significant changes in uRPL. Forty-eight percent of DEGs and 84% of differentially expressed pathways in uRPL were found in the endometrium of UI patients. Unexpected close association in gene expression pathways between UI and uRPL is observed supporting the hypothesis 'uRPL is a clinical subset of UI'. Yet 100% DEGs overlap wasn't found suggesting the endometrium has still some different gene expression patterns at start of WOI in UI and uRPL. Lastly, diagnostic tools may be developed for uRPL because more specific genes-pathways are involved compared with UI, which shows broader genetic expression profile.

Uterine-specific Ezh2 deletion enhances stromal cell senescence and impairs placentation, resulting in pregnancy loss

Maternal uterine remodeling facilitates embryo implantation, stromal cell decidualization and placentation, and perturbation of these processes may cause pregnancy loss. Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase that epigenetically represses gene transcription; loss of uterine EZH2 affects endometrial physiology and induces infertility. We utilized a uterine Ezh2 conditional knockout (cKO) mouse to determine EZH2's role in pregnancy progression. Despite normal fertilization and implantation, embryo resorption occurred mid-gestation in Ezh2cKO mice, accompanied by compromised decidualization and placentation. Western blot analysis revealed Ezh2-deficient stromal cells have reduced amounts of the histone methylation mark H3K27me3, causing upregulation of senescence markers p21 and p16 and indicating that enhanced stromal cell senescence likely impairs decidualization. Placentas from Ezh2cKO dams on gestation day (GD) 12 show architectural defects, including mislocalization of spongiotrophoblasts and reduced vascularization. In summary, uterine Ezh2 loss impairs decidualization, increases decidual senescence, and alters trophoblast differentiation, leading to pregnancy loss.

Downregulated INHBB in endometrial tissue of recurrent implantation failure patients impeded decidualization through the ADCY1/cAMP signalling pathway

PURPOSE

This study aims to identify the mechanism of Inhibin Subunit Beta B (INHBB), a member of the transforming growth factor-β (TGF-β) family involved in the regulation of human endometrial stromal cells (HESCs) decidualization in recurrent implantation failure (RIF).

METHODS

RNA-seq was conducted to identify the differentially expressed genes in the endometria from control and RIF patients. RT-qPCR, WB, and immunohistochemistry were performed to analyse the expression levels of INHBB in endometrium and decidualised HESCs. RT-qPCR and immunofluorescence were used to detect changes in the decidual marker genes and cytoskeleton after knockdown INHBB. Then, RNA-seq was used to dig out the mechanism of INHBB regulating decidualization. The cAMP analogue (forskolin) and si-INHBB were used to investigate the involvement of INHBB in the cAMP signalling pathway. The correlation of INHBB and ADCY expression was analysed by Pearson's correlation analysis.

RESULTS

Our results showed significantly reduced expression of INHBB in endometrial stromal cells of women with RIF. In addition, INHBB was increased in the endometrium of the secretory phase and significantly induced in in-vitro decidualization of HESCs. Notably, with RNA-seq and siRNA-mediated knockdown approaches, we demonstrated that the INHBB-ADCY1-mediated cAMP signalling pathway regulates the reduction of decidualization. We found a positive association between the expression of INHBB and ADCY1 in endometria with RIF (R2 = 0.3785, P = 0.0005).

CONCLUSIONS

The decline of INHBB in HESCs suppressed ADCY1-induced cAMP production and cAMP-mediated signalling, which attenuated decidualization in RIF patients, indicating that INHBB is an essential component in the decidualization process.

Reduction in CgA-Derived CST Protein Level in HTR-8/SVneo and BeWo Trophoblastic Cell Lines Caused by the Preeclamptic Environment

One of the most dangerous complications of pregnancy is preeclampsia (PE), a disease associated with a high risk of maternal and fetal mortality and morbidity. Although its etiology remains unknown, the placenta is believed to be at the center of ongoing changes. One of the hormones produced by the placenta is chromogranin A (CgA). Thus far, its role in pregnancy and pregnancy-related disorders is enigmatic, yet it is known that both CgA and its derived peptide catestatin (CST) are involved in the majority of the processes that are disturbed in PE, such as blood pressure regulation or apoptosis. Therefore, in this study, the influence of the preeclamptic environment on the production of CgA using two cell lines, HTR-8/SVneo and BeWo, was investigated. Furthermore, the capacity of trophoblastic cells to secrete CST to the environment was tested, as well as the correlation between CST and apoptosis. This study provided the first evidence that CgA and CST proteins are produced by trophoblastic cell lines and that the PE environment has an impact on CST protein production. Furthermore, a strong negative correlation between CST protein level and apoptosis induction was found. Hence, both CgA and its derived peptide CST may play roles in the complex process of PE pathogenesis.

Toxicity mechanism of peri-implantation pesticide beta-cypermethrin exposure on endometrial remodeling in early pregnant mice

Beta-cypermethrin (β-CYP) is a universally used pyrethroid pesticide with adverse effects on human health. β-CYP may impair endometrial remodeling in mice; however, the mechanism remains largely unknown. Endometrial remodeling plays a vital role in embryonic development and the maintenance of pregnancy. Therefore, we explored the mechanism by which peri-implantation β-CYP administration reduces uterine remodeling in pregnant mice. The C57BL/6J pregnant mice were administered a dose of 20mg/kg.bw. d β-CYP via oral gavage once daily from day 1 of gestation (GD1) to GD7. Molecular markers of endometrial remodeling, stromal cell proliferation, cell cycle regulation, and the PI3K/Akt/mTOR signaling pathway were evaluated in the decidual tissue of the uterus on GD7. An in vivo pseudopregnancy mouse model, a pregnant mouse model treated with an mTOR activator and an mTOR inhibitor and an in vitro decidualization model of mouse endometrial stromal cells were used to confirm β-CYP-induced defective endometrial remodeling and the key molecules expression of PI3K/Akt/mTOR signaling pathway. The results showed that β-CYP decreased the expression of the endometrial remodeling markers MMP9 and LIF in the uterine decidua. Peri-implantation β-CYP treatment markedly downregulated the expression of endometrial proliferation markers PCNA and Ki67 and decreased decidua thickness. Correspondingly, peri-implantation β-CYP exposure upregulated the expression of FOXO1, P57 and p-4E-BP1 in the decidua. Further experiments showed β-CYP significantly inhibited key molecules in the PI3K/Akt/mTOR pathway: PI3K, p-Akt/Akt, p-mTOR, and p-P70S6K in the uterine decidua. Additional experiments showed that aberrant endometrial remodeling induced by β-CYP was aggravated by rapamycin (an mTOR inhibitor) and partially reversed by MHY1485 (an mTOR agonist). In summary, our results indicated that a reduction in the PI3K/Akt/mTOR pathway may enhance defective endometrial remodeling by downregulating the proliferation and differentiation of endometrial stromal cells in early pregnant mice exposed to β-CYP. Our study elucidates the mechanism of defective endometrial remodeling induced by peri-implantation β-CYP exposure.

Chromogranin A: An Endocrine Factor of Pregnancy

Pregnancy is a state of physiological and hormonal changes. One of the endocrine factors involved in these processes is chromogranin A, an acidic protein produced, among others, by the placenta. Although it has been previously linked to pregnancy, no existing articles have ever managed to clarify the role of this protein regarding this subject. Therefore, the aim of the present study is to gather knowledge of chromogranin A's function with reference to gestation and parturition, clarify elusive information, and, most importantly, to formulate hypotheses for the future studies to verify.

Transcriptome-wide high-throughput m6 A sequencing of differential m6 A methylation patterns in the decidual tissues from RSA patients

Recurrent spontaneous abortion (RSA) is characterized by two or more consecutive pregnancy losses in the first trimester of pregnancy, experienced by 5% of women during their reproductive age. As a complex pathological process, the etiology of RSA remains poorly understood. Recent studies have established that gene expression changes dramatically in human endometrial stromal cells (ESCs) during decidualization. N6-methyladenosine (m⁶ A) modification is the most prevalent epigenetic modification of mRNA in eukaryotic cells and it is closely related to the occurrence and development of many pathophysiological phenomena. In this study, we first confirmed that high levels of m⁶ A mRNA methylation in decidual tissues are associated with RSA. Then, we used m⁶ A-modified RNA immunoprecipitation sequence (m⁶ A-seq) and RNA sequence (RNA-seq) to identify the differentially expressed m⁶ A methylation in decidual tissues from RSA patients and identified the key genes involved in abnormal decidualization by bioinformatics analysis. Using m⁶ A-seq, we identified a total of 2169 genes with differentially expressed m⁶ A methylation, of which 735 m⁶ A hypermethylated genes and 1434 m⁶ A hypomethylated genes were identified. Further joint analysis of m⁶ A-seq and RNA-seq revealed that 133 genes were m⁶ A modified with mRNA expression. GO and KEGG analyses indicated that these unique genes were mainly enriched in environmental information processing pathways, including the cytokine-cytokine receptor interaction and PI3K-Akt signaling pathway. In summary, this study uncovered the transcriptome-wide m⁶ A modification pattern in decidual tissue of RSA, which provides a theoretical basis for further research into m⁶ A modification and new therapeutic strategies for RSA.

Recombinant human chorionic gonadotropin and gonadotropin-releasing hormone agonist differently affect the profile of extracellular vesicle microRNAs in human follicular fluid

PURPOSE

To compare the expression profile of extracellular vesicle microRNAs (EV-miRNAs) derived from follicular fluid after a trigger with recombinant human chorionic gonadotropin (r-hCG) or with a gonadotropin-releasing hormone GnRH agonist (GnRH-a) for final oocyte maturation.

METHODS

A retrospective analysis of a prospective cohort. Women undergoing in vitro fertilization at a tertiary university-affiliated hospital were recruited between 2014 and 2016. EV-miRNAs were extracted from the follicular fluid of a single follicle, and their expression was assessed using TaqMan Open Array®. Genes regulated by EV-miRNAs were analyzed using miRWalk2.0 Targetscan database, DAVID Bioinformatics Resources, Kyoto-Encyclopedia of Genes and Genomes (KEGG), and Gene Ontology (GO).

RESULTS

Eighty-two women were included in the r-hCG trigger group and 9 in the GnRH-a group. Of 754 EV-miRNAs screened, 135 were detected in at least 50% of the samples and expressed in both groups and were further analyzed. After adjusting for multiple testing, 41 EV-miRNAs whose expression levels significantly differed between the two trigger groups were identified. Bioinformatics analysis of the genes regulated by these EV-miRNAs showed distinct pathways between the two triggers, including TGF-beta signaling, cell cycle, and Wnt signaling pathways. Most of these pathways regulate cascades associated with apoptosis, embryo development, implantation, decidualization, and placental development.

CONCLUSIONS

Trigger with GnRH-a or r-hCG leads to distinct EV-miRNAs expression profiles and to downstream biological effects in ovarian follicles. These findings may provide an insight for the increased apoptosis and the lower implantation rates following GnRH-a trigger vs. r-hCG in cases lacking intensive luteal phase support.

Transcriptomic profiling analysis of human endometrial stromal cells treated with autologous platelet-rich plasma

Purpose

To clarify the mechanisms of intrauterine platelet-rich plasma (PRP) infusion that support embryo implantation in in vitro fertilization treatment.

Methods

Blood and endometrial samples were collected from four infertile women. Human endometrial stromal cells (HESCs) were cultured and passaged equally into four cell culture dishes in each patient. Two were treated with PRP twice, and the other two were treated with vehicle. Subsequently, two cultures with and without PRP were decidualized with 8-bromoadenosine 3',5'-cyclic AMP and progesterone for 5 days.

Results

The gene expression in undifferentiated or decidualized HESCs with and without PRP was compared. In the microarray analysis, 381 and 63 differentially expressed genes were detected in undifferentiated and decidualized HESCs, respectively. In the undifferentiated HESCs, PRP was found to promote the gene expression associated with cell growth, tissue regeneration, proinflammatory response, and antibiotic effects. In decidualized HESCs, PRP was found to attenuate the gene expression involved in cell proliferation and inflammation by inhibiting the expression of phosphoinositide 3-kinase signaling.

Conclusions

Platelet-rich plasma regulates the reprogramming of cell proliferation and inflammation depending on menstrual cycle phases in an appropriate manner, suggesting that PRP has the potential to increase endometrial thickness in the proliferative phase and improve immune tolerance in the secretory phase.

Primary Cilia Restrain PI3K-AKT Signaling to Orchestrate Human Decidualization

Endometrial decidualization plays a pivotal role during early pregnancy. Compromised decidualization has been tightly associated with recurrent implantation failure (RIF). Primary cilium is an antenna-like sensory organelle and acts as a signaling nexus to mediate Hh, Wnt, TGFβ, BMP, FGF, and Notch signaling. However, whether primary cilium is involved in human decidualization is still unknown. In this study, we found that primary cilia are present in human endometrial stromal cells. The ciliogenesis and cilia length are increased by progesterone during in vitro and in vivo decidualization. Primary cilia are abnormal in the endometrium of RIF patients. Based on data from both assembly and disassembly of primary cilia, it has been determined that primary cilium is essential to human decidualization. Trichoplein (TCHP)-Aurora A signaling mediates cilia disassembly during human in vitro decidualization. Mechanistically, primary cilium modulates human decidualization through PTEN-PI3K-AKT-FOXO1 signaling. Our study highlights primary cilium as a novel decidualization-related signaling pathway.

Autophagy markers are dysregulated in the endometrial tissues of patients with unexplained repeated implantation failure

Endometrium decidualization is a complex biological process, which includes the interplay of transcription factors, cytokines, cell cycle regulators, and other signaling pathways. However, the underlying molecular mechanisms of this process are not fully elucidated to date. In this study, we aimed to investigate the possible association between autophagy and recurrent implantation failure (RIF). A total of 81 genes were downregulated and 231 genes were upregulated in the RIF group compared with the control group, and the differences were statistically significant (p < 0.05). Further, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway were analyzed, and we found that some autophagy markers, for example, LC3-II, LAMP2, and HIF-1α were significantly increased, whereas P62 was drastically downregulated in the RIF group. Similar results were observed in proteins level; and the autophagy puncta were also markedly enhanced in the endometrial tissues of RIF patients. Autophagy is closely associated with the RIF occurs and may be involved in the pathogenesis of RIF.

Comparative metabolomic profiling of women undergoing in vitro fertilization procedures reveals potential infertility-related biomarkers in follicular fluid

Infertility is a worldwide concern, affecting one in six couples throughout their reproductive period. Therefore, enhancing the clinical tools available to identify the causes of infertility may save time, money, and emotional distress for the involved parties. This study aims to annotate potential biomarkers in follicular fluid that are negatively affecting pregnancy outcomes in women suffering infertility-related diseases such as endometriosis, tuboperitoneal factor, uterine factor, and unexplained infertility, using a metabolomics approach through high-resolution mass spectrometry. Follicular fluid samples collected from women who have the abovementioned diseases and managed to become pregnant after in vitro fertilization procedures [control group (CT)] were metabolically compared with those from women who suffer from the same diseases and could not get pregnant after the same treatment [infertile group (IF)]. Mass spectrometry analysis indicated 10 statistically relevant differential metabolites in the IF group, including phosphatidic acids, phosphatidylethanolamines, phosphatidylcholines, phosphatidylinositol, glucosylceramides, and 1-hydroxyvitamin D3 3-D-glucopyranoside. These metabolites are associated with cell signaling, cell proliferation, inflammation, oncogenesis, and apoptosis, and linked to infertility problems. Our results indicate that understanding the IF's metabolic profile may result in a faster and more assertive female infertility diagnosis, lowering the costs, and increasing the probability of a positive pregnancy outcome.

Human umbilical cord platelet-rich plasma to treat endometrial pathologies: methodology, composition and pre-clinical models

STUDY QUESTION

Can human umbilical cord platelet-rich plasma (hUC-PRP) efficiently treat endometrial damage and restore fertility in a preclinical murine model?

SUMMARY ANSWER

Local application of hUC-PRP promotes tissue regeneration and fertility restoration in a murine model of Asherman syndrome and endometrial atrophy (AS/EA).

WHAT IS KNOWN ALREADY

AS/EA are well-described endometrial pathologies that cause infertility; however, there are currently no gold-standard treatments available. Recent reports have described the successful use of human platelet-rich plasma in reproductive medicine, and its regenerative potential is further enhanced using hUC-PRP, due to the ample growth factors and reduced pro-inflammatory cytokines in the latter.

STUDY DESIGN SIZE DURATION

hUC-PRP (n = 3) was processed, characterized and delivered locally to endometrial damage in a murine model (n = 50). The hUC-PRP was either used alone or loaded into a decellularized porcine endometrium-derived extracellular matrix (EndoECM) hydrogel; endometrial regeneration, fertility outcomes and immunocompatibility were evaluated 2 weeks following treatment administration.

PARTICIPANTS/MATERIALS SETTING METHODS

Umbilical cord blood was obtained from women in childbirth. Endometrial damage (mimicking AS/EA) was induced using ethanol in 8-week-old C57BL/6 mice, and treated with the most concentrated hUC-PRP sample 4 days later. Characterization of hUC-PRP and immunotolerance was carried out with multiplex technology, while uterine samples were analyzed by immunohistochemistry and quantitative PCR. The number of embryos and their morphology was determined visually.

MAIN RESULTS AND THE ROLE OF CHANCE

Platelet density was enhanced 3-fold in hUC-PRP compared to that in hUC blood (P < 0.05). hUC-PRP was enriched with growth factors related to tissue regeneration (i.e. hepatocyte growth factor, platelet-derived growth factor-BB and epidermal growth factor), which were released constantly (in vitro) when hUC-PRP was loaded into EndoECM. Both treatments (hUC-PRP alone and hUC-PRP with EndoECM) were immunotolerated and caused significantly regeneration of the damaged endometrium, evidenced by increased endometrial area, neoangiogenesis, cell proliferation and gland density and lower collagen deposition with respect to non-treated uterine horns (P < 0.05). Additionally, we detected augmented gene expression of Akt1, VEGF and Ang, which are involved in regenerative and proliferation pathways. Finally, hUC-PRP treatment restored pregnancy rates in the mouse model.

LARGE SCALE DATA

N/A.

LIMITATIONS REASONS FOR CAUTION

This proof-of-concept pilot study was based on a murine model of endometrial damage and the use of EndoECM requires further validation prior to clinical implementation for women affected by AS/EA.

WIDER IMPLICATIONS OF THE FINDINGS

The local administration of hUC-PRP has high impact and is immunotolerated in a murine model of AS/EA, as has been reported in other tissues, making it a promising candidate for heterologous treatment of these endometrial pathologies.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by the Ministerio de Ciencia, Innovación y Universidades; Conselleria de Innovación, Universidades, Ciencia y Sociedad Digital, Generalitat Valenciana; and Instituto de Salud Carlos III. The authors do not have any conflicts of interest to declare.

Endocrine disrupting chemicals interfere with decidualization of human primary endometrial stromal cells in vitro

Multiple studies have shown associations between exposure to endocrine disrupting chemicals (EDCs) and reduced fertility in women. However, little is known about the target organs of chemical disruption of female fertility. Here, we focus on the hormone-sensitive uterine lining, the endometrium, as a potential target. Decidualization is the morphological and functional change that endometrial stromal cells undergo to support endometrial receptivity, which is crucial for successful implantation, placentation, and pregnancy. We investigated the effect of nine selected EDCs on primary human endometrial stromal cell decidualization in vitro. The cells were exposed to a decidualization-inducing mixture in the presence or absence of 1 μM of nine different EDCs for nine days. Extent of decidualization was assessed by measuring the activity of cAMP dependent protein kinase, Rho-associated coiled-coil containing protein kinase, and protein kinase B in lysates using photoluminescent probes, and secretion of prolactin into the media by using ELISA. Decidualization-inducing mixture upregulated activity of protein kinases and prolactin secretion in cells derived from all women. Of the tested chemicals, dichlorodiphenyldichloroethylene (p,p'-DDE), hexachlorobenzene (HCB) and perfluorooctanesulfonic acid (PFOS) significantly reduced decidualization as judged by the kinase markers and prolactin secretion. In addition, bisphenol A (BPA) reduced prolactin secretion but did not significantly affect activity of the kinases. None of the EDCs was cytotoxic, based on the assessment of total protein content or activity of the viability marker casein kinase 2 in lysates. These results indicate that EDCs commonly present in the blood circulation of reproductive-aged women can reduce decidualization of human endometrial stromal cells in vitro. Future studies should focus on detailed hazard assessment to define possible risks of EDC exposure to endometrial dysfunction and implantation failure in women.

A novel lncRNA lncSAMD11-1: 1 interacts with PIP4K2A to promote endometrial decidualization by stabilizing FoxO1 nuclear localization

Decidualization is essential for a successful pregnancy and determines embryo implantation and pregnancy maintenance. Abnormal decidualization is one of the main causes of recurrent implantation failure (RIF). Studies have shown that large amounts of long noncoding RNAs (lncRNAs) are abnormally expressed in endometrial samples from patients with RIF. However, the functional contributions of lncRNAs to decidualization in RIF have not been explored. In this study, we found that lncSAMD11-1:1 was significantly declined in the endometria of patients with RIF. The knockdown of lncSAMD11-1:1 in human endometrial stromal cells (hESCs) restrained decidualization and embryo implantation in vitro, while the overexpression of lncSAMD11-1:1 facilitated hESC decidualization and embryo implantation in vitro and ameliorated decidualization in RIF patients. Mechanistically, lncSAMD11-1:1 and phosphatidylinositol-5-phosphate 4-kinase type 2 alpha (PIP4K2A) translocated out of nucleus and bound to each other during decidualization, thereby inhibiting the phosphorylation of AKT and promoting FoxO1 nuclear localization. These data suggest that lncSAMD11-1:1 might be a critical novel lncRNA functionally required for human decidualization, and the dysregulation of lncSAMD11-1:1 in the endometrium may be a new predisposing factor of RIF.

Short Communication: Maternal obesity alters ovine endometrial gene expression during peri-implantation development

Exposure to maternal obesity in utero is associated with marked developmental effects in offspring that may not be evident until adulthood. Mechanisms regulating the programming effects of maternal obesity on fetal development have been reported, but little is known about how maternal obesity affects the earliest periods of embryonic development. This work explored how obesity influences endometrial gene expression during the peri-implantation period using a sheep model. Ewes were assigned randomly to diets that produced an obese state or maintained a lean state. After 4 mo, obese and lean ewes were bred and then euthanized at day 14 post-breeding. The uterus was excised, conceptuses were flushed, and endometrial tissue was collected. Isolated RNA from endometrial tissues (n = 6 ewes/treatment) were sequenced using an Illumina-based platform. Reads were mapped to the Ovis aries genome (Oar_4.0). Differential gene expression was determined, and results were filtered (false discovery rate ≤ 0.05 and ≥2-fold change, ≥0.2 reads/kilobase/million reads). Differentially expressed genes (DEGs) were identified (n = 699), with 171 downregulated and 498 upregulated in obese vs. lean endometrium, respectively. The most pronounced gene ontology categories identified were cellular process, metabolic process, and biological regulation. Enrichments were detected within the DEGs for genes involved with immune system processes, negative regulation of apoptosis, cell growth, and cell adhesion. A literature search revealed that 125 DEGs were associated with either the trophoblast lineage or the placenta. Genes within this grouping were involved with wingless/integrated signaling, angiogenesis, and integrin signaling. In summary, these data indicate that the peri-implantation endometrium is responsive to maternal obesity. Transcript profile analyses suggest that the endometrial immune response, adhesion, and angiogenesis may be especially susceptible to obesity. Thus, alterations in uterine transcript profiles during early embryogenesis may be a mechanism responsible for developmental programming following maternal obesity exposure in utero.

The Circ-CYP24A1-miR-224-PRLR Axis Impairs Cell Proliferation and Apoptosis in Recurrent Miscarriage

Aim

Recurrent miscarriage (RM) is associated with numerous clinical factors. However, some RM occurred without specific factors. It has been revealed that some molecules such as hormones, miRNAs, and transcription factors are involved in RM by regulating proliferation, apoptosis, etc. However, the mechanism of RM has yet to be identified clearly. Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs that often act as sponges for miRNAs or binds to proteins involved in biological processes. However, the functional role of circRNAs in the uterine decidua of patients with early RM is still unclear. In this study, we aimed to investigate the mechanisms of circ-CYP24A1 in RM.

Methods

The Dual-Luciferase Activity Assay was designed to analyze the bonding between circ-CYP24A1 and miR-224, and miR-224 and prolactin receptor (PRLR) mRNA 3′UTR. In situ hybridization (ISH) and immunohistochemistry (IHC) were used to observe the expression of circ-CYP24A1 and PRLR in the decidua. Rescue experiments were performed to investigate the regulating effects of circ-CYP24A1, miR-224, and PRLR. Western blotting was conducted to test the expression level of PRLR. The proliferation and apoptosis-related markers in Ishikawa cells were analyzed using CCK8, immunofluorescence staining, and the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) assay.

Results

In this study, based on the microarray analysis data, we identified a high level of circ-CYP24A1 and PRLR in the decidua of patients with early RM. Based on the bioinformatics prediction, the binding relationship between circ-CYP24A1 and miR-224, as well as miR-224 and PRLR, were verified. Functional experiments demonstrated that circ-CYP24A1 regulated proliferation and apoptosis by binding to and inhibiting miR-224, resulting in increased PRLR expression. Taken together, this study provides new insights into the mechanism of RM.

Conclusion

In this study, we found that circ-CYP24A1 plays a role in RM by impairing the balance of cell proliferation and apoptosis by sponging miR-224, thereby regulating PRLR.

The Anti-Endometriotic Effect of Cyperi Rhizoma Extract, Inhibiting Cell Adhesion and the Expression of Pain-Related Factors through Akt and NF-kB Pathways

Rhizomes of Cyperus rotundus have been widely used as a traditional medicine in Asia for the treatment of gynecological diseases. However, there is no scientific evidence demonstrating the effect of C. rotundus rhizomes on endometriosis, which is characterized by the adhesion of endometrial tissues outside the uterus, resulting in chronic and severe pelvic pain. The aim of this study was to investigate the effects of Cyperi rhizoma extract (CRE) on cell adhesion and the expression of pain-related factors (neurotrophins) in endometriotic cells, and to elucidate the underlying molecular mechanisms. CRE inhibited the adhesion of human endometriotic 12Z cells to peritoneal mesothelial Met5A cells using by adhesion assays. The mRNA expression of adhesion molecules [P-cadherin and matrix metalloproteinase (MMP)-2] was downregulated by CRE treatment. In addition, CRE significantly inhibited the mRNA expression of neurotrophins (BDNF, NGF, NT-3 and NT-4/5) in 12Z cells. Moreover, Akt overexpression markedly neutralized the inhibition of cell adhesion by CRE and expression of neurotrophins in 12Z cells. Furthermore, it was found that CRE suppressed NF-kB activation through the Akt pathway. These data suggest that CRE exerts anti-endometriotic activities by the inhibition of cell adhesion and neurotrophin expression, through the negative regulation of the Akt and NF-kB pathways in endometriotic cells.

Shp2 in uterine stromal cells critically regulates on time embryo implantation and stromal decidualization by multiple pathways during early pregnancy

Approximately 75% of failed pregnancies are considered to be due to embryo implantation failure or defects. Nevertheless, the explicit signaling mechanisms governing this process have not yet been elucidated. Here, we found that conditional deletion of the Shp2 gene in mouse uterine stromal cells deferred embryo implantation and inhibited the decidualization of stromal cells, which led to embryonic developmental delay and to the death of numerous embryos mid-gestation, ultimately reducing female fertility. The absence of Shp2 in stromal cells increased the proliferation of endometrial epithelial cells, thereby disturbing endometrial epithelial remodeling. However, Shp2 deletion impaired the proliferation and polyploidization of stromal cells, which are distinct characteristics of decidualization. In human endometrial stromal cells (hESCs), Shp2 expression gradually increased during the decidualization process. Knockout of Shp2 blocked the decidual differentiation of hESCs, while Shp2 overexpression had the opposite effect. Shp2 knockout inhibited the proliferation of hESCs during decidualization. Whole gene expression profiling analysis of hESCs during the decidualization process showed that Shp2 deficiency disrupted many signaling transduction pathways and gene expression. Analyses of hESCs and mouse uterine tissues confirmed that the signaling pathways extracellular regulated protein kinases (ERK), protein kinase B (AKT), signal transducer and activator of transcription 3 (STAT3) and their downstream transcription factors CCAAT/enhancer binding protein β (C/EBPβ) and Forkhead box transcription factor O1 (FOXO-1) were involved in the Shp2 regulation of decidualization. In summary, these results demonstrate that Shp2 plays a crucial role in stromal decidualization by mediating and coordinating multiple signaling pathways in uterine stromal cells. Our discovery possibly provides a novel key regulator of embryo implantation and novel therapeutic target for pregnancy failure.

Embryo implantation includes the establishment of uterine receptivity, blastocyst attachment, and endometrial decidualization. Disorders of this process usually induce pregnancy failure, resulting in women infertility. But the signaling mechanisms governing this process remain unclear. Here, using gene knockout mouse model and human endometrial stromal cells (hESCs), we identified a novel key regulator of embryo implantation, Shp2, which plays a crucial role in stromal decidualization by mediating and coordinating multiple signaling pathways in uterine stromal cells. Shp2 deficiency in mouse uterine stromal cells inhibited the uterine stromal decidualization, disturbing embryo implantation and embryonic development, ultimately reducing female fertility. The absence of Shp2 in hESCs also blocked the decidual differentiation. Our findings not only promote the understanding of peri-implantation biology, but may also provide a critical target for more effectively diagnose and/or treat women with recurrent implantation failure or early pregnancy loss.

OUP accepted manuscript

STUDY QUESTION

Is the composition of microRNAs (miRNAs) in uterine fluid (UF) of women with recurrent implantation failure (RIF) different from that of healthy fertile women?

SUMMARY ANSWER

The composition of miRNAs in UF of women with RIF is different from that of healthy fertile women and the dysregulated miRNAs are associated with impaired endometrial receptivity and embryo implantation.

WHAT IS KNOWN ALREADY

It has previously been demonstrated that the miRNAs secreted from endometrial cells into the UF contribute to the achievement of endometrial receptivity. Endometrial miRNAs are dysregulated in women with RIF.

STUDY DESIGN, SIZE, DURATION

In this descriptive laboratory case–control study, miRNA abundancy was compared between UF collected during implantation phase from healthy fertile women (n = 17) and women with RIF (n = 34), which was defined as three failed IVF cycles with high-quality embryos.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Recruitment of study subjects and sampling of UF were performed at two university clinics in Stockholm, Sweden and Tartu, Estonia. The study participants monitored their menstrual cycles using an LH test kit. The UF samples were collected on Day LH + 7–9 by flushing with saline. Samples were processed for small RNA sequencing and mapped for miRNAs. The differential abundance of miRNAs in UF was compared between the two groups using differential expression analysis (DESeq2). Further downstream analyses, including miRNA target gene prediction (miRTarBase), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis (g:Profiler) and external validation using relevant published data, were performed on the dysregulated miRNAs. Two miRNAs were technically validated with quantitative real-time PCR (RT-PCR).

MAIN RESULTS AND THE ROLE OF CHANCE

After processing of the sequencing data, there were 15 samples in the healthy fertile group and 33 samples in the RIF group. We found 61 differentially abundant UF miRNAs (34 upregulated and 27 downregulated) in RIF compared to healthy women with a false discovery rate of <0.05 and a fold change (FC) of ≤−2 or ≥2. When analyzed with published literature, we found that several of the differentially abundant miRNAs are expressed in endometrial epithelial cells and have been reported in endometrial extracellular vesicles and in association with endometrial receptivity and RIF. Their predicted target genes were further expressed both in the trophectodermal cells of blastocyst-stage embryos and endometrial mid-secretory epithelial cells, as assessed by publicly available single-cell transcriptome-sequencing studies. Pathway analysis further revealed that 25 pathways, having key roles in endometrial receptivity and implantation, were significantly enriched. Hsa-miR-486-5p (FC −20.32; P-value = 0.004) and hsa-miR-92b-3p (FC −9.72; P-value = 0.004) were successfully technically validated with RT-PCR.

LARGE SCALE DATA

The data are available in Gene Expression Omnibus (GEO) at https://www.ncbi.nlm.nih.gov/geo/ with GEO accession number: GSE173289.

LIMITATIONS, REASONS FOR CAUTION

This is a descriptive study with a limited number of study participants. Moreover, the identified differentially abundant miRNAs should be validated in a larger study cohort, and the predicted miRNA target genes and enriched pathways in RIF need to be confirmed and further explored in vitro.

WIDER IMPLICATIONS OF THE FINDINGS

RIF is a major challenge in the current IVF setting with no diagnostic markers nor effective treatment options at hand. For the first time, total miRNAs have been extensively mapped in receptive phase UF of both healthy women with proven fertility and women diagnosed with RIF. Our observations shed further light on the molecular mechanisms behind RIF, with possible implications in future biomarker and clinical treatment studies.

STUDY FUNDING/COMPETING INTEREST(S)

This work was financially supported by the Swedish Research Council (2017-00932), a joint grant from Region Stockholm and Karolinska Institutet (ALF Medicine 2020, FoUI-954072), Estonian Research Council (PRG1076), Horizon 2020 innovation (ERIN, EU952516) and European Commission and Enterprise Estonia (EU48695). The authors have no competing interests to declare for the current study.

Investigation and Validation of Molecular Characteristics of Endometrium in Recurrent Miscarriage and Unexplained Infertility from a Transcriptomic Perspective

Recurrent miscarriage (RM) and unexplained infertility (UI) are gordian knots in reproductive medicine, which are troubling many patients, doctors, and researchers. Although these two diseases of early pregnancy have a significant impact on human reproductive health, little is known about the specific mechanisms, which caused treatment difficulties. This study focused on the molecular signatures underlying the pathological phenotypes of two diseases, with the hope of using statistical methods to identify the significant core genes. An unbiased Weighted Correlation Network Analysis (WGCNA) algorithm was used for endometrial transcriptome data analysis and the disease-related gene modules were screened out. Through enrichment analysis of the candidate genes, we found similarities between both diseases and shared enrichment of immune-related pathways. Therefore, we used immune algorithms to assess the infiltration of immune cells and found abnormal increases of CD8+T cells and neutrophils. In order to explore the molecular profile behind the immunophenotypic changes, we used the SVM algorithm and LASSO regression to identify the core genes with diagnostic capacity in both diseases and discussed their significance of immune disorders in the endometrium. In the end, the satisfactory diagnostic ability of these core genes was verified in the broader group. Our results demonstrated the presence of immune disorders in non-pregnancy tissues of RM and UI, and identified the core molecules of this phenotype, and discuss mechanisms. This provides exploratory evidence for the in-depth understanding of the mechanism of RM and UI and may provide potential targets for their future treatment.

Cyclic activity of signal transduction pathways in fimbrial epithelium of the human fallopian tube

INTRODUCTION

The local environment of the fallopian tube represents the optimal conditions for reproductive processes. To maintain tissue homeostasis, signal transduction pathways are thought to play a pivotal role. Enhancing our understanding of functional signal transduction pathway activity is important to be able to clarify the role of aberrant signal transduction pathway activity leading to female subfertility and other tubal diseases. Therefore, in this study we investigate the influence of the hormonal cycle on the activity of key signal transduction pathways in the fimbrial epithelium of morphologically normal fallopian tubes.

MATERIAL AND METHODS

We included healthy pre- (n = 17) and postmenopausal (n = 8) patients who had surgical interventions for benign gynecologic conditions. Histologic sections of the fallopian tubes were reviewed by two pathologists and, for the premenopausal patients, hormone serum levels and sections of the endometrium were examined to determine the hormonal phase (early follicular [n = 4], late follicular [n = 3], early luteal [n = 5], late luteal [n = 5]). After laser capture microdissection, total mRNA was extracted from the fimbrial epithelium and real-time quantitative reverse transcription-PCR was performed to determine functional signal transduction pathway activity of the androgen receptor (AR), estrogen receptor (ER), phosphoinositide-3-kinase (PI3K), Hedgehog (HH), transforming growth factor-beta (TGF-β) and canonical wingless-type MMTV integration site (Wnt) pathways.

RESULTS

The early luteal phase demonstrated high AR and ER pathway activity in comparison with the late luteal phase (p = 0.016 and p = 0.032, respectively) and low PI3K activity compared with the late follicular phase (p = 0.036), whereas the late luteal phase showed low activity of HH and Wnt compared with the early follicular phase (both p = 0.016). Signal transduction pathway activity in fimbrial epithelium from postmenopausal patients was most similar to the early follicular and/or late luteal phase with regard to the AR, ER and PI3K pathways. Wnt pathway activity in postmenopausal patients was comparable to the late follicular and early luteal phase. We observed no differences in HH and TGF-β pathway activity between pre- and postmenopausal samples. The cyclic changes in signal transduction pathway activity suggest a stage-specific function which may affect the morphology and physiology of the human fallopian tube.

CONCLUSIONS

We demonstrated cyclic changes in activity of the AR, ER, PI3K, HH and Wnt pathways throughout the hormonal cycle.

Progestins as Anticancer Drugs and Chemosensitizers, New Targets and Applications

Progesterone and its synthetic analogues, progestins, participate in the regulation of cell differentiation, proliferation and cell cycle progression. Progestins are usually applied for contraception, maintenance of pregnancy, and hormone replacement therapy. Recently, their effectiveness in the treatment of hormone-sensitive tumors was revealed. According to current data, the anticancer activity of progestins is mainly mediated by their cytotoxic and chemosensitizing influence on different cancer cells. In connection with the detection of previously unknown targets of the progestin action, which include the membrane-associated progesterone receptor (PR), non-specific transporters related to the multidrug resistance (MDR) and mitochondrial permeability transition pore (MPTP), and checkpoints of different signaling pathways, new aspects of their application have emerged. It is likely that the favorable influence of progestins is predominantly associated with the modulation of expression and activity of MDR-related proteins, the inhibition of survival signaling pathways, especially TGF-β and Wnt/β-catenin pathways, which activate the proliferation and promote MDR in cancer cells, and the facilitation of mitochondrial-dependent apoptosis. Biological effects of progestins are mediated by the inhibition of these signaling pathways, as well as the direct interaction with the nucleotide-binding domain of ABC-transporters and mitochondrial adenylate translocase as an MPTP component. In these ways, progestins can restore the proliferative balance, the ability for apoptosis, and chemosensitivity to drugs, which is especially important for hormone-dependent tumors associated with estrogen stress, epithelial-to-mesenchymal transition, and drug resistance.

Analysis of heart and neural crest derivatives-expressed protein 2 (HAND2)-progesterone interactions in peri-implantation endometrium†

Implantation is restricted to a narrow window when the local endometrial microenvironment is supportive of the invading embryo. The ovarian steroid hormones estrogen (E) and progesterone (P) are principal regulators of uterine receptivity. Suppression of E-dependent proliferation of luminal epithelium (LE) by P is mandatory for embryo implantation. Here, we report that the balance of E receptor α (ERα) and P receptors (PR) activity controls HAND2 expression, a key transcription factor that determines the fate of the implanting embryo and thereby pregnancy outcome. As a model, we used wild-type mice as well as mice in which either both PR isoforms or the A-isoform was genetically ablated (PRKO and PRAKO, respectively). Detailed spatiotemporal analyses of PR, HAND2, and ERα expression at implantation site demonstrated co-expression of HAND2 and PR but not ERα. Furthermore, in hormonally treated ovariectomized WT, PRAKO and PRKO mice, E suppresses endometrial HAND2 expression. Adding P together with E partially rescues HAND2 expression in WT, but not PRAKO and PRKO animals. Therefore, infertility in PRAKO mice is at least in part associated with the loss of PR-A-regulated HAND2 expression.

Progesterone triggers Rho kinase-cofilin axis during in vitro and in vivo endometrial decidualization

STUDY QUESTION

Can a combination of the focussed protein kinase assays and a wide-scale proteomic screen pinpoint novel, clinically relevant players in decidualization in vitro and in vivo?

SUMMARY ANSWER

Rho-dependent protein kinase (ROCK) activity is elevated in response to the combined treatment with progesterone and 8-Br-cAMP during in vitro decidualization, mirrored by increase of ROCK2 mRNA and protein levels and the phosphorylation levels of its downstream target Cofilin-1 (CFL1) in secretory versus proliferative endometrium.

WHAT IS KNOWN ALREADY

Decidualization is associated with extensive changes in gene expression profile, proliferation, metabolism and morphology of endometrium, yet only a few underlying molecular pathways have been systematically explored. In vitro decidualization of endometrial stromal cells (ESCs) can be reportedly induced using multiple protocols with variable physiological relevance. In our previous studies, cyclic AMP (cAMP)/cAMP-dependent protein kinase (PKA)/prolactin axis that is classically upregulated during decidualization showed dampened activation in ESCs isolated from polycystic ovary syndrome (PCOS) patients as compared to controls.

STUDY DESIGN, SIZE, DURATION

In vitro decidualization studies were carried out in passage 2 ESCs isolated from controls (N = 15) and PCOS patients (N = 9). In parallel, lysates of non-cultured ESCs isolated from proliferative (N = 4) or secretory (N = 4) endometrial tissue were explored. The observed trends were confirmed using cryo-cut samples of proliferative (N = 3) or secretory endometrium (N = 3), and in proliferative or secretory full tissue samples from controls (N = 8 and N = 9, respectively) or PCOS patients (N = 10 for both phases).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The activities of four target kinases were explored using kinase-responsive probes and selective inhibitors in lysates of in vitro decidualized ESCs and non-cultured ESCs isolated from tissue at different phases of the menstrual cycle. In the latter lysates, wide-scale proteomic and phosphoproteomic studies were further carried out. ROCK2 mRNA expression was explored in full tissue samples from controls or PCOS patients. The immunofluorescent staining of phosphorylated CFL1 was performed in full endometrial tissue samples, and in the in vitro decidualized fixed ESCs from controls or PCOS patients. Finally, the cellular migration properties were explored in live in vitro decidualized ESCs.

MAIN RESULTS AND THE ROLE OF CHANCE

During in vitro decidualization, the activities of PKA, protein kinase B (Akt/PKB), and ROCK are increased while the activity of casein kinase 2 (CK2) is decreased; these initial trends are observable after 4-day treatment (P < 0.05) and are further augmented following the 9-day treatment (P < 0.001) with mixtures containing progesterone and 8-Br-cAMP or forskolin. The presence of progesterone is necessary for activation of ROCK, yet it is dispensable in the case of PKA and Akt/PKB; in comparison to controls, PCOS patient-derived ESCs feature dampened response to progesterone. In non-cultured ESCs isolated from secretory vs proliferative phase tissue, only activity of ROCK is increased (P < 0.01). ROCK2 protein levels are slightly elevated in secretory versus proliferative ESCs (relative mean standard deviation < 50%), and ROCK2 mRNA is elevated in mid-secretory versus proliferative full tissue samples (P < 0.05) obtained from controls but not PCOS patients. Activation of ROCK2 downstream signalling results in increase of phospho-S3 CFL1 in secretory endometrium (P < 0.001) as well as in vitro decidualized ESCs (P < 0.01) from controls but not PCOS patients. ROCK2-triggered alterations in the cytoskeleton are reflected by the significantly decreased motility of in vitro decidualized ESCs (P < 0.05).

LARGE SCALE DATA

Proteomic and phosphoproteomic data are available via ProteomeXchange with identifier PXD026243.

LIMITATIONS, REASONS FOR CAUTION

The number of biological samples was limited. The duration of protocol for isolation of non-cultured ESCs from tissue can potentially affect phosphorylation pathways in cells, yet the possible artefacts were minimized by the identical treatment of proliferative and secretory samples.

WIDER IMPLICATIONS OF THE FINDINGS

The study demonstrated the benefits of combining the focussed kinase activity assay with wide-scale phosphoproteomics and showed the need for detailed elaboration of the in vitro decidualization protocols. ROCK was identified as the novel target of interest in decidualization, which requires closer attention in further studies-including the context of decidualization-related subfertility and infertility.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Estonian Ministry of Education and Research, and the Estonian Research Council (PRG1076, PRG454, PSG230 and PSG608), Enterprise Estonia (EU48695), Horizon 2020 innovation grant (ERIN, Grant no. EU952516) of the European Commission, the COMBIVET ERA Chair, H2020-WIDESPREAD-2018-04 (Grant agreement no. 857418), the Academy of Finland (Project grants 315921 and 321763), the Finnish Medical Foundation and The Sigrid Juselius Foundation. The authors confirm that they have no conflict of interest with respect to the content of this article.

Preimplantation factor modulates trophoblastic invasion throughout the decidualization of human endometrial stromal cells

BACKGROUND

Successful human embryo implantation requires the differentiation of endometrial stromal cells (ESCs) into decidual cells during a process called decidualization. ESCs express specific markers of decidualization, including prolactin, insulin-like growth factor-binding protein-1 (IGFBP-1), and connexin-43. Decidual cells also control of trophoblast invasion by secreting various factors, such as matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases. Preimplantation factor (PIF) is a recently identified, embryo-derived peptide with activities at the fetal-maternal interface. It creates a favorable pro-inflammatory environment in human endometrium and directly controls placental development by increasing the human trophoblastic cells' ability to invade the endometrium. We hypothesized that PIF's effects on the endometrium counteract its pro-invasive effects.

METHODS

We tested sPIF effect on the expression of three decidualization markers by RT-qPCR and/or immunochemiluminescence assay. We examined sPIF effect on human ESC migration by performing an in vitro wound healing assay. We analyzed sPIF effect on endometrial control of human trophoblast invasion by performing a zymography and an invasion assay.

RESULTS

Firstly, we found that a synthetic analog of PIF (sPIF) significantly upregulates the mRNA expression of IGFBP-1 and connexin-43, and prolactin secretion in ESCs - suggesting a pro-differentiation effect. Secondly, we showed that the HTR-8/SVneo trophoblastic cell line's invasive ability was low in the presence of conditioned media from ESCs cultured with sPIF. Thirdly, this PIF's anti-invasive action was associated with a specifically decrease in MMP-9 activity.

CONCLUSION

Taken as a whole, our results suggest that PIF accentuates the decidualization process and the production of endometrial factors that limit trophoblast invasion. By controlling both trophoblast and endometrial cells, PIF therefore appears to be a pivotal player in the human embryo implantation process.

Pharmacologic inhibition of Akt in combination with chemotherapeutic agents effectively induces apoptosis in ovarian and endometrial cancer cell lines

The PI3K/Akt signaling pathway, the most frequently altered signaling system in human cancer, is a crucial inducer of dysregulated proliferation and neoplastic processes; however, few therapeutic strategies using PI3K/Akt inhibitors singly have been shown to be effective. The purpose of this paper was to underline the potential benefit of pharmacological modulation of the PI3K/Akt pathway when combined with specific chemotherapeutic regimens. We have studied the ability of NVP‐BEZ235 (PI3K/mTOR inhibitor) and AZD5363 (Akt inhibitor) in the sensitization of cancer cells to cisplatin and doxorubicin. Our results show that NVP‐BEZ235 sensitizes cells preferentially to cisplatin while AZD5363 sensitizes cells to doxorubicin. At equal concentrations (5 μm), both inhibitors reduce ribosomal protein S6 phosphorylation, but AZD5363 is more effective in reducing GSK3β phosphorylation as well as S6 phosphorylation. Additionally, AZD5363 is capable of inducing FOXO1 and p53 nuclear localization and reduces BAD phosphorylation, which is generally increased by cisplatin and doxorubicin. Finally, the combination of AZD5363 and doxorubicin induces apoptosis in cells and robustly reduces cell ability to clonally replicate, which underlines a potential cooperative effect of the studied compounds.

Exploring the role of Luman/CREB3 in regulating decidualization of mice endometrial stromal cells by comparative transcriptomics

Background

Luman is a member of CREB3 (cAMP responsive element-binding) subfamily of the basic leucine-zipper (bZIP) transcription factors. It may play an important regulatory role during the decidualization process since Luman was highly expressed in the decidual cells. However, the exact molecular mechanisms of how Luman regulating decidualization is unknown.

Results

Using an in vitro model, we prove that Luman knockdown significantly affects the decidualization process of mice endometrial stromal cells (ESCs) as the expression of two decidual markers PRL8a2 and PRL3c1 were repressed. We employed massively parallel RNA sequencing (RNA-Seq) to understand the changes in the transcriptional landscape associated with knockdown of Luman in ESCs during in vitro decidualization. We found significant dysregulation of genes related to protein processing in the endoplasmic reticulum (ER). Several genes involved in decidualization including bone morphogenetic proteins (e.g. BMP1, BMP4, BMP8A, BMP2, and BMP8B), growth factor-related genes (e.g. VEGFB, FGF10, and FGFR2), and transcription factors (IF4E, IF4A2, WNT4, WNT9A, ETS1, NOTCH1, IRX1, IDB1, IDB2, and IDB3), show altered expression. We also found that the knockdown of Luman is associated with increased expression of cell cycle-related genes including cycA1, cycB1, cycB2, CDK1, CDK2, and PLPK1, which resulted in an increased proportion of ESCs in the G1 phase. Differentially expressed genes (DEGs) were highly enriched on ECM-receptor interaction signaling, endoplasmic reticulum protein processing, focal adhesion, and PI3K-Akt signaling pathways.

Conclusions

Luman knockdown results in widespread gene dysregulation during decidualization of ESCs. Genes involved in protein processing in ER, bone morphogenetic protein, growth factor, and cell cycle progression were identified as particularly important for explaining the decidual deficiency observed in this in vitro model. Therefore, this study provides clues as to the underlying mechanisms that may expand our understanding of gene regulation during decidualization.

Elevated insulin levels compromise endometrial decidualization in mice with decrease in uterine apoptosis in early-stage pregnancy

Women with hyperinsulinism and insulin resistance have reduced fertility, but the underlying mechanism is still poorly understood. Aberrant endometrial decidualization in early pregnancy was linked to pregnancy complications. In this study, we aimed to test whether elevated insulin levels compromise decidualization in early-stage pregnancy. C57BL/6J mice in high insulin-exposed group were given a subcutaneous injection of recombinant insulin at a concentration of 0.05 IU daily. During decidualization in early pregnancy, serum levels of insulin, E2, P4, LH, FSH and blood glucose were significantly altered in mice treated with high insulin levels. The number of embryo implantation sites and endometrial decidual markers BMP2, ER, PR was significantly decreased by high insulin levels in vivo. Artificial decidual induction in primary mouse endometrial stromal cells and immortal human endometrial stromal cells line were all compromised after treated with 100 nmol/L insulin levels. All these results on flow cytometry, transmission electron microscopy and western blotting of Bax, Bcl2, cleaved Caspase3, cleaved PARP proteins level showed that decidual cells apoptosis was significantly decreased. Mitochondrial transmembrane potential also significantly increased by the influence of high insulin levels. PI3K and p-Akt were much higher after insulin exposure and the compromised decidualization by high insulin treatment was rescued by PI3K/Akt inhibitor LY294002 both in vitro and in vivo. In conclusion, we demonstrated that elevated insulin levels could compromise mice decidualization in early-stage pregnancy and PI3K/p-Akt-regulated apoptosis was essential for this role. It provides a clue for future investigation on compromised reproduction in women with hyperinsulinemia.

Microgravity inhibits decidualization via decreasing Akt activity and FOXO3a expression in human endometrial stromal cells

Decidualization is characterized by the differentiation of endometrial stromal cells (eSCs), which is critical for embryo implantation and maintenance of pregnancy. In the present study, we investigated the possible effect of simulated microgravity (SM) on the process of proliferation and in vitro decidualization using primary human eSCs. Exposure to SM for 36 h decreased the proliferation and migration of eSCs significantly, without inducing cell death and changes in cell cycle progression. The phosphorylation of Akt decreased under SM conditions in human eSCs, accompanied by a simultaneous decrease in the level of matrix metalloproteinase (MMP)-2 and FOXO3a. Treatment with Akti, an Akt inhibitor, decreased MMP-2 expression, but not FOXO3a expression. The decreased level of FOXO3a under SM conditions impeded autophagic flux by reducing the levels of autophagy-related genes. In addition, pre-exposure of eSCs to SM significantly inhibited 8-Br-cAMP induced decidualization, whereas restoration of the growth status under SM conditions by removing 8-Br-cAMP remained unchanged. Treatment of human eSCs with SC-79, an Akt activator, restored the reduced migration of eSCs and decidualization under SM conditions. In conclusion, exposure to SM inhibited decidualization in eSCs by decreasing proliferation and migration through Akt/MMP and FOXO3a/autophagic flux.

Alterations in intracellular Ca2+ levels in human endometrial stromal cells after decidualization

Calcium (Ca2+) is an important element for many physiological functions of the uterus, including embryo implantation. Here, we investigated the possible involvement of altered intracellular Ca2+ levels in decidualization in human endometrial stromal cells (hEMSCs). hEMSCs showed high levels of mesenchymal stem cell marker expression (CD73, CD90, and CD105) and did not express markers of hematopoietic progenitor cells (CD31, CD34, CD45, and HLA-DR). Decidualization is a process of ovarian steroid-induced endometrial stromal cell proliferation and differentiation. Several types of ion channels, which are regulated by the ovarian hormones progesterone and estradiol, as well as growth factors, are important for endometrial receptivity and embryo implantation. The combined application of progesterone (1 μM medroxyprogesterone acetate) and cyclic AMP (0.5 mM) for 6 days not only elevated inositol 1,4,5-triphosphate receptor (IP3R)-mediated Ca2+ release and IP3R expression, it also promoted ORAI and STIM expression as well as cyclopiazonic acid-induced Ca2+ release. Finally, intracellular Ca2+ levels and ion channel gene expression influenced hEMSC proliferation. These results suggest that cytosolic Ca2+ dynamics, mediated by specific ion channels, serve as an important step in the decidualization of hEMSCs.

Glucose regulates the histone acetylation of gene promoters in decidualizing stromal cells

Decidualization stimuli activate the insulin signaling pathway and increase the glucose uptake in human endometrial stromal cells (ESCs). The inductions of prolactin (PRL) and IGF-binding protein-1 (IGFBP1), specific markers of decidualization, were inhibited by incubating ESCs under low glucose concentrations. These results suggested that decidualization stimuli activate the insulin signaling pathway, which contributes to decidualization through the increase of glucose uptake. Here, we investigated the mechanisms by which glucose regulates decidualization. ESCs were incubated with cAMP to induce decidualization. We examined whether low glucose affects the expression levels of transcription factors that induce decidualization. Forkhead box O1 (FOXO1) expression was significantly suppressed under low glucose conditions. Knockdown of FOXO1 by siRNA inhibited the expression levels of PRL and IGFBP1 during decidualization. Taken together, our results showed that low glucose inhibits decidualization by decreasing FOXO1 expression. We also examined the levels of histone H3K27 acetylation (H3K27ac), which is related to active transcription, of the promoter regions of FOXO1, PRL and IGFBP1 by ChIP assay. The H3K27ac levels of these promoter regions were increased by decidualization under normal glucose conditions, but not under low glucose conditions. Thus, our results show that glucose is indispensable for decidualization by activating the histone modification status of the promoters of PRL, IGFBP1 and FOXO1.

Differential regulation of mTORC1 and mTORC2 is critical for 8-Br-cAMP-induced decidualization

Human endometrium decidualization, a differentiation process involving biochemical and morphological changes, is a prerequisite for embryo implantation and successful pregnancy. Here, we show that the mammalian target of rapamycin (mTOR) is a crucial regulator of 8-bromoadenosine 3',5'-cyclic monophosphate (8-Br-cAMP)-induced decidualization in human endometrial stromal cells. The level of mSin1 in mTOR complex 2 (mTORC2) and DEPTOR in mTOR complex 1 (mTORC1) decreases during 8-Br-cAMP-induced decidualization, resulting in decreased mTORC2 activity and increased mTORC1 activity. Notably, DEPTOR displacement increases the association between raptor and insulin receptor substrate-1 (IRS-1), facilitating IRS-1 phosphorylation at serine 636/639. Finally, both S473 and T308 phosphorylation of Akt are reduced during decidualization, followed by a decrease in forkhead box O1 (FOXO1) phosphorylation and an increase in the mRNA levels of the decidualization markers prolactin (PRL) and insulin-like growth factor-binding protein-1 (IGFBP-1). Taken together, our findings reveal a critical role for mTOR in decidualization, involving the differential regulation of mTORC1 and mTORC2.