Dysregulation of In Vitro Decidualization of Human Endometrial Stromal Cells by Insulin via Transcriptional Inhibition of Forkhead Box Protein O1

Uterine cyclin A2-deficient mice as a model of female early pregnancy loss

Proper action of the female sex steroids 17β-estradiol (E2) and progesterone (P4) on the endometrium is essential for fertility. Beyond its role in regulating the cell cycle, cyclin A2 (CCNA2) also mediates E2 and P4 signaling in vitro, but a potential role in modulating steroid action for proper endometrial tissue development and function is unknown. To fill this gap in our knowledge, we examined human endometrial tissue from fertile and infertile cisgender women for CCNA2 expression and correlated this with pregnancy outcome. Functional assessment of CCNA2 was validated in vivo using a conditional Ccna2 uterine-deficient mouse model, while in vitro function was assessed using human cell culture models. We found that CCNA2 expression was significantly reduced in endometrial tissue, specifically the stromal cells, from women undergoing in vitro fertilization who failed to achieve pregnancy. Conditional deletion of Ccna2 from mouse uterine tissue resulted in an inability to achieve pregnancy, which appeared to be due to alterations in the process of decidualization, which was confirmed using in vitro models. From these studies, we conclude that CCNA2 expression during the proliferative/regenerative stage of the menstrual cycle allows for proper steroid responsiveness, decidualization, and pregnancy. When CCNA2 expression levels are insufficient, there is impaired endometrial responsiveness, aberrant decidualization, and loss of pregnancy.

Hyperinsulinemia impairs decidualization via AKT-NR4A1 signaling: new insight into polycystic ovary syndrome (PCOS)-related infertility

BACKGROUND

Investigating the underlying molecular mechanisms responsible for endometrial dysfunction in women with PCOS is essential, particularly focusing on the role of hyperinsulinemia.

METHODS

We explored the role of insulin in the decidualization process using a synthetic decidualization assay. To dissect the effects of PI3K/AKT-NR4A signaling, we employed small interfering RNAs (siRNAs) targeting the NR4A genes and inhibitors of the PI3K/AKT pathway. We also investigated the disruption of AKT-NR4A1 signaling in the endometrium of PCOS female rats induced with dehydroepiandrosterone (DHEA). Quantitative real-time PCR (qRT-PCR) and Western blot (WB) analyses were utilized to evaluate gene expression regulation.

RESULTS

Insulin was found to suppress the expression of decidualization markers in human endometrial stromal cells (hESC) in a dose-dependent manner, concurrently triggering an inappropriate activation of the PI3K/AKT pathway. Members of the NR4A family, as downstream effectors in the PI3K/AKT pathway, were implicated in the insulin-induced disruptions during the decidualization process. Moreover, the endometrium of PCOS models showed significantly elevated levels of phosphorylated (Ser473) AKT, with a corresponding reduction in Nr4a1 protein.

CONCLUSIONS

Our research demonstrates that insulin negatively regulates decidualization in hESC via the PI3K/AKT-NR4A pathway. In vivo analysis revealed a significant dysregulation of the AKT-NR4A1 pathway in the endometrium of PCOS rats. These findings offer novel insights into the pathogenesis of infertility and endometrial disorders associated with hyperinsulinemia in PCOS.

Polycystic ovary syndrome and adverse pregnancy outcomes: potential role of decidual function

Polycystic ovary syndrome (PCOS) is a common endocrine disorder affecting fertility and mental health among women of reproductive age. In addition to anovulation and hyperandrogenism, patients also experience metabolic issues, such as insulin resistance, obesity, and dyslipidemia, as well as chronic low-grade inflammation throughout the body. Recent studies have shown that even with assisted reproductive technology to treat anovulatory issues, patients with PCOS still have higher rates of adverse pregnancy outcomes and abortion compared to normal pregnancies. These findings suggest that PCOS may impair the endometrium and disrupt the onset and maintenance of healthy pregnancies. Decidualization is a crucial step in the process of healthy pregnancy, during which endometrial stromal cells (ESCs) differentiate into secretory decidual stromal cells (DSCs) regulated by hormones and local metabolism. This article comprehensively reviews the pathological processes of PCOS and the mechanisms involved in its impaired decidualization. In addition, we explore how PCOS increases the incidence of adverse pregnancy outcomes (APO). By gaining a better understanding of the adverse effects of PCOS on pregnancy and its specific mechanisms, we hope to provide a theoretical basis for reducing APO and improving the live birth rate among women with PCOS.

Impaired decidualization and relative increase of PROK1 expression in the decidua of patients with unexplained recurrent pregnancy loss showing insulin resistance

A recent meta-analysis revealed that patients with unexplained recurrent pregnancy loss (RPL) show higher insulin resistance compared to healthy controls. However, the etiology of RPL remains unknown. Prokineticin (PROK1), a pleiotropic uterine endometrial protein, is important for implantation and decidualization and is regulated by hypoxia and insulin. In this study, we investigated the decidualization status and the role of PROK1 in the decidua of patients with unexplained RPL showing insulin resistance. Thirty-two patients with unexplained RPL were included in this study. Following the diagnosis of a miscarriage, the decidua and villi of the patient were surgically collected. Fasting blood glucose and insulin levels were measured, and HOMA-β was calculated. Using IHC and ELISA, the expression of IGFBP-1, PRL and PROK1 in the decidua and IGF-2 in the villi were analyzed in patients with euploid miscarriage with a high HOMA-β index (n = 8) and compared to controls (euploid miscarriage with normal HOMA-β: n = 12, aneuploid miscarriage with normal HOMA-β: n = 12). The co-localization of PROK1 and IGFBP-1 was observed in the decidua by IHC. In the decidua of RPL patients with high HOMA-β, the expression levels of IGFBP-1 and PRL were significantly lower, whereas the PROK1/IGFBP-1 ratio was significantly higher compared to that of the controls. IGF-2 expression in villi was significantly lower in RPL patients with high HOMA-β. Impaired decidualization and excessive PROK1 production may have pathological implications in patients with unexplained RPL with insulin resistance, especially under the state of hyper insulin production.

DHT and Insulin Upregulate Secretion of the Soluble Decoy Receptor of IL-33 From Decidualized Endometrial Stromal Cells

Interleukin 33 (IL-33) signaling regulates most of the key processes of pregnancy, including decidualization, trophoblast proliferation and invasion, vascular remodeling, and placental growth. Accordingly, dysregulation of IL-33, its membrane-bound receptor (ST2L, transducer of IL-33 signaling), and its soluble decoy receptor (sST2, inhibitor of IL-33 signaling) has been linked to a wide range of adverse pregnancy outcomes that are common in women with obesity and polycystic ovary syndrome, that is, conditions associated with hyperandrogenism, insulin resistance, and compensatory hyperinsulinemia. To reveal if androgens and insulin might modulate uteroplacental IL-33 signaling, we investigated the effect of dihydrotestosterone (DHT) and/or insulin on the expression of ST2L and sST2 (along with the activity of their promoter regions), IL-33 and sIL1RAP (heterodimerization partner of sST2), during in vitro decidualization of endometrial stromal cells from 9 healthy women. DHT and insulin markedly upregulated sST2 secretion, in addition to the upregulation of its messenger RNA (mRNA) expression, while the proximal ST2 promoter, from which the sST2 transcript originates, was upregulated by insulin, and in a synergistic manner by DHT and insulin combination treatment. On the other hand, sIL1RAP was slightly downregulated by insulin and IL-33 mRNA expression was not affected by any of the hormones, while ST2L mRNA expression and transcription from its promoter region (distal ST2 promoter) could not be detected or showed a negligibly low level. We hypothesize that high levels of androgens and insulin might lead to subfertility and pregnancy complications, at least partially, through the sST2-dependent downregulation of uteroplacental IL-33 signaling.

ATOH8 Expression Is Regulated by BMP2 and Plays a Key Role in Human Endometrial Stromal Cell Decidualization

During the secretory phase of the menstrual cycle, elongated fibroblast-like mesenchymal cells in the uterine endometrium begin to transdifferentiate into polygonal epithelioid-like (decidual) cells. This decidualization process continues more broadly during early pregnancy, and the resulting decidual tissue supports successful embryo implantation and placental development. This study was carried out to determine if atonal basic helix-loop-helix transcription factor 8 (ATOH8) plays a role in human endometrial stromal fibroblast (ESF) decidualization. ATOH8 messenger RNA and protein expression levels significantly increased in human ESF cells undergoing in vitro decidualization, with the protein primarily localized to the nucleus. When ATOH8 expression was silenced, the ability of the cells to undergo decidualization was significantly diminished. Overexpression of ATOH8 enhanced the expression of many decidualization markers. Silencing the expression of ATOH8 reduced the expression of FZD4, FOXO1, and several known FOXO1-downstream targets during human ESF cell decidualization. Therefore, ATOH8 may be a major upstream regulator of the WNT/FZD-FOXO1 pathway, previously shown to be critical for human endometrial decidualization. Finally, we explored possible regulators of ATOH8 expression during human ESF decidualization. BMP2 significantly enhanced ATOH8 expression when cells were stimulated to undergo decidualization, while an ALK2/3 inhibitor reduced ATOH8 expression. Finally, although the steroids progesterone plus estradiol did not affect ATOH8 expression, the addition of cyclic adenosine monophosphate (cAMP) analogue alone represented the major effect of ATOH8 expression when cells were stimulated to undergo decidualization. Our results suggest that ATOH8 plays a crucial role in human ESF decidualization and that BMP2 plus cAMP are major regulators of ATOH8 expression.

Enhanced ZBTB16 Levels by Progestin-Only Contraceptives Induces Decidualization and Inflammation

Progestin-only long-acting reversible-contraceptive (pLARC)-exposed endometria displays decidualized human endometrial stromal cells (HESCs) and hyperdilated thin-walled fragile microvessels. The combination of fragile microvessels and enhanced tissue factor levels in decidualized HESCs generates excess thrombin, which contributes to abnormal uterine bleeding (AUB) by inducing inflammation, aberrant angiogenesis, and proteolysis. The- zinc finger and BTB domain containing 16 (ZBTB16) has been reported as an essential regulator of decidualization. Microarray studies have demonstrated that ZBTB16 levels are induced by medroxyprogesterone acetate (MPA) and etonogestrel (ETO) in cultured HESCs. We hypothesized that pLARC-induced ZBTB16 expression contributes to HESC decidualization, whereas prolonged enhancement of ZBTB16 levels triggers an inflammatory milieu by inducing pro-inflammatory gene expression and tissue-factor-mediated thrombin generation in decidualized HESCs. Thus, ZBTB16 immunostaining was performed in paired endometria from pre- and post-depo-MPA (DMPA)-administrated women and oophorectomized guinea pigs exposed to the vehicle, estradiol (E2), MPA, or E2 + MPA. The effect of progestins including MPA, ETO, and levonorgestrel (LNG) and estradiol + MPA + cyclic-AMP (E2 + MPA + cAMP) on ZBTB16 levels were measured in HESC cultures by qPCR and immunoblotting. The regulation of ZBTB16 levels by MPA was evaluated in glucocorticoid-receptor-silenced HESC cultures. ZBTB16 was overexpressed in cultured HESCs for 72 h followed by a ± 1 IU/mL thrombin treatment for 6 h. DMPA administration in women and MPA treatment in guinea pigs enhanced ZBTB16 immunostaining in endometrial stromal and glandular epithelial cells. The in vitro findings indicated that: (1) ZBTB16 levels were significantly elevated by all progestin treatments; (2) MPA exerted the greatest effect on ZBTB16 levels; (3) MPA-induced ZBTB16 expression was inhibited in glucocorticoid-receptor-silenced HESCs. Moreover, ZBTB16 overexpression in HESCs significantly enhanced prolactin (PRL), insulin-like growth factor binding protein 1 (IGFBP1), and tissue factor (F3) levels. Thrombin-induced interleukin 8 (IL-8) and prostaglandin-endoperoxide synthase 2 (PTGS2) mRNA levels in control-vector-transfected HESCs were further increased by ZBTB16 overexpression. In conclusion, these results supported that ZBTB16 is enhanced during decidualization, and long-term induction of ZBTB16 expression by pLARCs contributes to thrombin generation through enhancing tissue factor expression and inflammation by enhancing IL-8 and PTGS2 levels in decidualized HESCs.

High Glucose Promotes Inflammation and Weakens Placental Defenses against E. coli and S. agalactiae Infection: Protective Role of Insulin and Metformin

Placentas from gestational diabetes mellitus (GDM) patients undergo significant metabolic and immunologic adaptations due to hyperglycemia, which results in an exacerbated synthesis of proinflammatory cytokines and an increased risk for infections. Insulin or metformin are clinically indicated for the treatment of GDM; however, there is limited information about the immunomodulatory activity of these drugs in the human placenta, especially in the context of maternal infections. Our objective was to study the role of insulin and metformin in the placental inflammatory response and innate defense against common etiopathological agents of pregnancy bacterial infections, such as E. coli and S. agalactiae, in a hyperglycemic environment. Term placental explants were cultivated with glucose (10 and 50 mM), insulin (50–500 nM) or metformin (125–500 µM) for 48 h, and then they were challenged with live bacteria (1 × 105 CFU/mL). We evaluated the inflammatory cytokine secretion, beta defensins production, bacterial count and bacterial tissue invasiveness after 4–8 h of infection. Our results showed that a GDM-associated hyperglycemic environment induced an inflammatory response and a decreased beta defensins synthesis unable to restrain bacterial infection. Notably, both insulin and metformin exerted anti-inflammatory effects under hyperglycemic infectious and non-infectious scenarios. Moreover, both drugs fortified placental barrier defenses, resulting in reduced E. coli counts, as well as decreased S. agalactiae and E. coli invasiveness of placental villous trees. Remarkably, the double challenge of high glucose and infection provoked a pathogen-specific attenuated placental inflammatory response in the hyperglycemic condition, mainly denoted by reduced TNF-α and IL-6 secretion after S. agalactiae infection and by IL-1β after E. coli infection. Altogether, these results suggest that metabolically uncontrolled GDM mothers develop diverse immune placental alterations, which may help to explain their increased vulnerability to bacterial pathogens.

Basigin is necessary for normal decidualization of human uterine stromal cells

STUDY QUESTION

Does basigin (BSG) regulate human endometrial stromal cell (HESC) decidualization in vitro?

SUMMARY ANSWER

BSG regulates HESCs proliferation and decidualization.

WHAT IS KNOWN ALREADY

Studies have shown that in the human endometrium, BSG expression is menstrual-cycle dependent and its expression was significantly lower in uterine endometrium during the luteal phase of women experiencing multiple implantation failures after IVF than in women with normal fertility.

STUDY DESIGN, SIZE, DURATION

We utilized a telomerase-immortalized HESCs in an in vitro cell culture model system to investigate whether BSG regulates decidualization of stromal cells. Further, we used microarray analysis to identify changes in the gene expression profile of HESCs treated with BSG small interfering RNA (siRNA). All experiments were repeated at least three times.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effect of BSG knockdown (using siRNA) on HESC proliferation was determined by counting cell number and by tritiated thymidine incorporation assays. The effect of BSG on decidualization of HESCs was determined by RT-qPCR for the decidualization markers insulin-like growth factor-binding protein 1 (IGFBP1) and prolactin (PRL). Immunoblotting was used to determine the effect of BSG siRNA on the expression of MMP-2,3. Microarray analysis was used to identify BSG-regulated genes in HESCs at Day 6 of decidualization. Functional and pathway enrichment analyses were then carried out on the differentially expressed genes (DEGs). The STRING online database was used to analyze protein-protein interaction (PPI) between DEG-encoded proteins, and CytoScape software was used to visualize the interaction. MCODE and CytoHubba were used to construct functional modules and screen hub genes separately. Several BSG-regulated genes identified in the microarray analysis were confirmed by qPCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Knockdown of BSG expression in cultured stromal cells by siRNA significantly (P < 0.05) inhibited HESC proliferation, disrupted cell decidualization and down-regulated MMP-2 and MMP-3 expression. Microarray analysis identified 721 genes that were down-regulated, and 484 genes up-regulated with P < 0.05 in BSG siRNA treated HESCs. GO term enrichment analysis showed that the DEGs were significantly enriched in cell communication, signaling transduction and regulation, response to stimulus, cell adhesion, anatomical structure morphogenesis, extracellular matrix organization, as well as other functional pathways. KEGG pathway analysis identified upregulated gene enriched in pathways such as the MAPK signaling pathway, colorectal cancer, melanoma and axon guidance. In contrast, downregulated genes were mainly enriched in pathways including ECM-receptor interaction, PI3K-Akt signaling pathway, pathways in cancer, antigen processing, type I diabetes mellitus and focal adhesion. The top 10 hub nodes were identified using 12 methods analyses. The hub genes that showed up in two methods were screened out. Among these genes, upregulated genes included EGFR, HSP90AA1, CCND1, PXN, PRKACB, MGAT4A, EVA1A, LGALS1, STC2, HSPA4; downregulated genes included WNT4/5, FOXO1, CDK1, PIK3R1, IGF1, JAK2, LAMB1, ITGAV, HGF, MXRA8, TMEM132A, UBE2C, QSOX1, ERBB2, GNB4, HSP90B1, LAMB2, LAMC1 and ITGA1. Hub genes and module genes involved in the top three modules of PPI analysis were analyzed through the string database. Analysis showed that hub and module genes were related mainly to the WNT signaling pathway, PI3K-AKT signaling pathway and pathways in cancer.

LARGE SCALE DATA

The microarray data set generated in this study has been published online at databank.illinois.edu.

LIMITATIONS, REASONS FOR CAUTION

Most of the findings were obtained using an in vitro cell culture system that may not necessarily reflect in vivo functions.

WIDER IMPLICATIONS OF THE FINDINGS

Our results demonstrate that BSG plays a vital role in decidualization and that downregulation of BSG in the uterine endometrium may be associated with infertility in women. The identified hub genes and pathways increase our understanding of the genetic etiology and molecular mechanisms underlying the regulation of decidualization by BSG.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the NIH U54 HD40093 (R.A.N.). The authors have no competing interests to declare.

Single-cell analysis of menstrual endometrial tissues defines phenotypes associated with endometriosis

BACKGROUND

Endometriosis is a common, complex disorder which is underrecognized and subject to prolonged delays in diagnosis. It is accompanied by significant changes in the eutopic endometrial lining.

METHODS

We have undertaken the first single-cell RNA-sequencing (scRNA-Seq) comparison of endometrial tissues in freshly collected menstrual effluent (ME) from 33 subjects, including confirmed endometriosis patients (cases) and controls as well as symptomatic subjects (who have chronic symptoms suggestive of endometriosis but have not been diagnosed).

RESULTS

We identify a unique subcluster of proliferating uterine natural killer (uNK) cells in ME-tissues from controls that is almost absent from endometriosis cases, along with a striking reduction of total uNK cells in the ME of cases (p < 10-16). In addition, an IGFBP1+ decidualized subset of endometrial stromal cells are abundant in the shed endometrium of controls when compared to cases (p < 10-16) confirming findings of compromised decidualization of cultured stromal cells from cases. By contrast, endometrial stromal cells from cases are enriched in cells expressing pro-inflammatory and senescent phenotypes. An enrichment of B cells in the cases (p = 5.8 × 10-6) raises the possibility that some may have chronic endometritis, a disorder which predisposes to endometriosis.

CONCLUSIONS

We propose that characterization of endometrial tissues in ME will provide an effective screening tool for identifying endometriosis in patients with chronic symptoms suggestive of this disorder. This constitutes a major advance, since delayed diagnosis for many years is a major clinical problem in the evaluation of these patients. Comprehensive analysis of ME is expected to lead to new diagnostic and therapeutic approaches to endometriosis and other associated reproductive disorders such as female infertility.

The Regulators of Human Endometrial Stromal Cell Decidualization

Several factors are important for implantation and subsequent placentation in the endometrium, including immunity, angiogenesis, extracellular matrix, glucose metabolism, reactive oxidative stress, and hormones. The involvement or abnormality of these factors can impair canonical decidualization. Unusual decidualization can lead to perinatal complications, such as disruption of trophoblast invasion. Drastic changes in the morphology and function of human endometrial stromal cells (hESCs) are important for decidualization of the human endometrium; hESCs are used to induce optimal morphological and functional decidualization in vitro because they contain estrogen and progesterone receptors. In this review, we will focus on the studies that have been conducted on hESC decidualization, including the results from our laboratory.

The Translational Role of miRNA in Polycystic Ovary Syndrome: From Bench to Bedside—A Systematic Literature Review

MicroRNAs (miRNAs) are small, non-coding RNAs that are essential for the regulation of post-transcriptional gene expression during tissue development and differentiation. They are involved in the regulation of manifold metabolic and hormonal processes and, within the female reproductive tract, in oocyte maturation and folliculogenesis. Altered miRNA levels have been observed in oncological and inflammatory diseases, diabetes or polycystic ovary syndrome (PCOS). Therefore, miRNAs are proving to be promising potential biomarkers. In women with PCOS, circulating miRNAs can be obtained from whole blood, serum, plasma, urine, and follicular fluid. Our systematic review summarizes data from 2010–2021 on miRNA expression in granulosa and theca cells; the relationship between miRNAs, hormonal changes, glucose and lipid metabolism in women with PCOS; and the potential role of altered miRNAs in fertility (oocyte quality) in PCOS. Furthermore, we discuss miRNAs as a potential therapeutic target in PCOS and as a diagnostic marker for PCOS.

Calpain7 negatively regulates human endometrial stromal cell decidualization in EMs by promoting FoxO1 nuclear exclusion via hydrolyzing AKT1

Endometrial receptivity damage caused by impaired decidualization may be one of the mechanisms of infertility in endometriosis (EMs). Our previous study demonstrated that Calpain-7 (CAPN7) is abnormally overexpressed in EMs. Whether CAPN7 affects the regulation of decidualization and by what mechanism CAPN7 regulates decidualization remains to be determined. In this study, we found CAPN7 expression decreased during human endometrial stromal cell (HESC) decidualization in vitro. CAPN7 negatively regulated decidualization in vitro and in vivo. We also identified one conserved potential PEST sequence in the AKT1 protein and found that CAPN7 was able to hydrolyse AKT1 and enhance AKT1's phosphorylation. Correspondingly, CAPN7 notably promoted the phosphorylation of Forkhead Box O1 (FoxO1), the downstream of AKT1 protein, at Ser319, leading to increased FoxO1 exclusion from nuclei and attenuated FoxO1 transcriptional activity in decidualized HESC. In addition, we detected endometrium CAPN7, p-AKT1 and p-FoxO1 expressions were increased in EMs. These data demonstrate that CAPN7 negatively regulates HESC decidualization in EMs probably by promoting FoxO1's phosphorylation and FoxO1 nuclear exclusion via hydrolyzing AKT1. The dysregulation of CAPN7 may be a novel cause of EMs.

C-Peptide Promotes Cell Migration by Controlling Matrix Metallopeptidase-9 Activity Through Direct Regulation of β-Catenin in Human Endometrial Stromal Cells

The motility of endometrial stromal cells (ESCs) contributes to the restoration of the endometrial functional layer and subsequently supports the trophoblast invasion during early pregnancy. Following ESCs differentiation through decidualization in response to progesterone during the menstrual cycle and embryo implantation, decidualized ESCs (D-ESCs) have greater motility and invasive activity. The human proinsulin-connecting peptide (C-peptide) is produced in equimolar amounts during the proteolysis of insulin in pancreatic β-cells. However, the function of C-peptide in the cellular motility of the human endometrium remains unexamined. In the present study, C-peptide was identified as a determinant of undecidualized human endometrial stromal cells (UnD-ESCs) migration. C-peptide promoted the migration and invasion of UnD-ESCs and trophoblast-derived Jeg3 cells, but not that of ESCs post decidualization, a functional and biochemical differentiation of UnD-ESCs. Both Akt and protein phosphatase 1 regulated β-catenin phosphorylation in UnD-ESCs, not D-ESCs, thereby promoting β-catenin nuclear translocation in C-peptide-treated UnD-ESCs. C-peptide was also observed to increase matrix metallopeptidase-9 (MMP9) activity by increasing MMP9 expression and decreasing the expression of metallopeptidase inhibitor 1 (TIMP1) and TIMP3. Their expression was modulated by the direct binding of β-catenin in the regulatory region of the promoter of MMP9, TIMP1, and TIMP3. Inhibition of either β-catenin or MMP9 dampened C-peptide-enhanced migration in UnD-ESCs. Together, these findings suggest that C-peptide levels are critical for the regulation of UnD-ESC migration, providing evidence for the association between C-peptide levels and the failure rate of trophoblast invasion by inducing abnormal migration in UnD-ESCs in hyperinsulinemia or PCOS patients.

Higher preconceptional maternal body mass index is associated with faster early preimplantation embryonic development: the Rotterdam periconception cohort

BACKGROUND

Overweight and obesity affect millions of people globally, which has also serious implications for reproduction. For example, treatment outcomes after in vitro fertilisation (IVF) are worse in women with a high body mass index (BMI). However, the impact of maternal BMI on embryo quality is inconclusive. Our main aim is to study associations between preconceptional maternal BMI and morphokinetic parameters of preimplantation embryos and predicted implantation potential. In addition, associations with clinical IVF outcomes are investigated.

METHODS

From a tertiary hospital, 268 women undergoing IVF or IVF with intracytoplasmic sperm injection (ICSI) were included; 143 normal weight, 79 overweight and 46 obese women. The embryos of these women were cultured in the EmbryoScope, a time-lapse incubator. The morphokinetic parameters of preimplantation embryos and predicted implantation potential, assessed by the KIDScore algorithm were longitudinally evaluated as primary and secondary outcomes, respectively. The tertiary outcomes included clinical outcomes, i.e., fertilization, implantation and live birth rate.

RESULTS

After adjustment for patient- and treatment-related factors, we demonstrated in 938 embryos that maternal BMI is negatively associated with the moment of pronuclear appearance (β_tPNa -0.070 h (95%CI -0.139, -0.001), p = 0.048), pronuclear fading (β_tPNf -0.091 h (95%CI -0.180, -0.003), p = 0.043 and the first cell cleavage (β_t2 -0.111 h (95%CI -0.205, -0.016), p = 0.022). Maternal BMI was not significantly associated with the KIDScore and tertiary clinical treatment outcomes. In embryos from couples with female or combined factor subfertility, the impact of maternal BMI was even larger (β_tPNf -0.170 h (95%CI -0.293, -0.047), p = 0.007; β_t2 -0.199 h (95%CI -0.330, -0.067), p = 0.003). Additionally, a detrimental impact of BMI per point increase was observed on the KIDScore (β -0.073 (se 0.028), p = 0.010).

CONCLUSIONS

Higher maternal BMI is associated with faster early preimplantation development. In couples with female or combined factor subfertility, a higher BMI is associated with a lower implantation potential as predicted by the KIDScore. Likely due to power issues, we did not observe an impact on clinical treatment outcomes. However, an effect of faster preimplantation development on post-implantation development is conceivable, especially since the impact of maternal BMI on pregnancy outcomes has been widely demonstrated.

Mechanistic Target of Rapamycin Complex 1 Signaling Links Hypoxia to Increased IGFBP-1 Phosphorylation in Primary Human Decidualized Endometrial Stromal Cells

Insulin-like growth factor-1 (IGF-1) bioavailability in pregnancy is governed by IGF binding protein (IGFBP-1) and its phosphorylation, which enhances the affinity of IGFBP-1 for the growth factor. The decidua is the predominant source of maternal IGFBP-1; however, the mechanisms regulating decidual IGFBP-1 secretion/phosphorylation are poorly understood. Using decidualized primary human endometrial stromal cells (HESCs) from first-trimester placenta, we tested the hypothesis that mTORC1 signaling mechanistically links hypoxia to decidual IGFBP-1 secretion/phosphorylation. Hypoxia inhibited mechanistic target of rapamycin (mTORC1) (p-P70-S6K/Thr389, -47%, p = 0.038; p-4E-BP1/Thr70, -55%, p = 0.012) and increased IGFBP-1 (total, +35%, p = 0.005; phosphorylated, Ser101/+82%, p = 0.018; Ser119/+88%, p = 0.039; Ser 169/+157%, p = 0.019). Targeted parallel reaction monitoring-mass spectrometry (PRM-MS) additionally demonstrated markedly increased dual IGFBP-1 phosphorylation (pSer98+Ser101; pSer169+Ser174) in hypoxia. IGFBP-1 hyperphosphorylation inhibited IGF-1 receptor autophosphorylation/ Tyr1135 (-29%, p = 0.002). Furthermore, silencing of tuberous sclerosis complex 2 (TSC2) activated mTORC1 (p-P70-S6K/Thr389, +68%, p = 0.038; p-4E-BP1/Thr70, +30%, p = 0.002) and reduced total/site-specific IGFBP-1 phosphorylation. Importantly, TSC2 siRNA prevented inhibition of mTORC1 and the increase in secretion/site-specific IGFBP-1 phosphorylation in hypoxia. PRM-MS indicated concomitant changes in protein kinase autophosphorylation (CK2/Tyr182; PKC/Thr497; PKC/Ser657). Overall, mTORC1 signaling mechanistically links hypoxia to IGFBP-1 secretion/phosphorylation in primary HESC, implicating decidual mTORC1 inhibition as a novel mechanism linking uteroplacental hypoxia to fetal growth restriction.

Interaction between insulin and androgen signalling in decidualization, cell migration and trophoblast invasion in vitro

Finely tuned decidualization of endometrial stromal fibroblasts into decidual cells is crucial for successful implantation and a healthy pregnancy. Both insulin and androgens are known to modulate decidualization, however, their complex effect on this process has not been fully elucidated. As hyperinsulinemia and hyperandrogenism are associated in clinical conditions, we aimed to investigate the interaction between insulin and androgens on decidualization. Primary human endometrial stromal cells were decidualized in vitro in the presence of insulin and/or androgens (dihydrotestosterone (DHT), testosterone). Gene or protein expressions of decidualization markers were measured, and cells size characteristics were determined. Migration of decidualizing endometrial stromal cells and invasion of HTR‐8/SVneo trophoblast spheroids were assessed. We found that insulin and androgens in combination enhanced the upregulation of several decidualization markers including prolactin, tissue factor, tissue inhibitor of matrix metalloproteinase 3 and connexin‐43, and also interacted in modulating cell size characteristics resulting in enlarged decidualizing cells. However, insulin and DHT together restricted the migration of decidualizing cells and invasion of trophoblast spheroids. Our findings suggest that insulin and androgens interact to potentiate the process of decidualization. On the other hand, inhibited cell migration and trophoblast invasion might negatively impact the function of decidualizing endometrial stromal cells.

An Update on the Progress of Endometrial Receptivity in Women with Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a significant public health issue with diverse presentations, including reproductive, metabolic, and psychological disorders. Although problems with ovulation, metabolism, and hormonal imbalance can be pharmacologically improved, even the excellent quality of transferred embryos does not necessarily increase the pregnancy rate. Poor endometrial receptivity in women with PCOS perturbs endometrial decidualization and blastocyst implantation, increasing adverse pregnancy outcomes, such as miscarriage and poor embryonic development. The etiological and pathophysiological mechanisms involved in defective endometrial receptivity in women with PCOS have not been fully elucidated to date. Various contributing factors have been reported as primary causes of defective endometrial receptivity in women with PCOS, including metabolic alterations, inflammatory events, and some abnormally expressed endometrial molecular markers. However, few studies to date have investigated in depth the complex mechanisms underlying the compromised endometrial receptivity in women with PCOS. This article reviews recent reports mainly on metabolic alterations and some new endometrial molecular markers in order to collate the existing data and improve our understanding in this field. The aim was to discuss current novel insights on defective endometrial receptivity in women with PCOS in order to provide a theoretical basis for reducing adverse pregnancy outcomes and improving the live birth rate in PCOS.

Decidual NK cell-derived conditioned medium from miscarriages affects endometrial stromal cell decidualisation: endocannabinoid anandamide and tumour necrosis factor-α crosstalk

STUDY QUESTION

What are the effects of endocannabinoid anandamide (AEA) in uterine natural killer (unK) cells from miscarriage decidua, regarding their cytokine profile and endometrial stromal cell (ESC) crosstalk?

SUMMARY ANSWER

uNK-conditioned media from miscarriage samples present high TNF-α levels which inhibit ESC decidualisation.

WHAT IS KNOWN ALREADY

AEA plasma levels are higher in women who have suffered a miscarriage. Moreover, AEA inhibits ESC proliferation and differentiation, although the levels and impact on the uNK cell cytokine profile at the feto-maternal interface remain elusive.

STUDY DESIGN, SIZE, DURATION

This laboratory-based study used human primary uNK cells which were isolated from first-trimester decidua (gestational age, 5-12 weeks) derived from 8 women with elective pregnancy termination and 18 women who suffered a miscarriage.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The first-trimester placental tissues were assayed for AEA levels by UPLC-MS/MS and respective enzymatic profile by western blot. The uNK cells were isolated and maintained in culture. The expression of angiogenic markers in uNK cells was examined by quantitative PCR (qPCR). The uNK-conditioned medium was analysed for IFN-γ, TNF-α and IL-10 production by enzyme-linked immunosorbent assay, and the impact on ESC differentiation was assessed by measuring decidual markers Prl, Igfbp-1 and Fox01 mRNA expression using qPCR.

MAIN RESULTS AND THE ROLE OF CHANCE

AEA levels were higher in miscarriage decidua compared with decidua from elective terminations. The uNK cell-conditioned medium from the miscarriage samples exhibited high TNF-α levels and interfered with the decidualisation of ESCs. Exacerbated inflammation and elevated TNF-α levels at the feto-maternal interface may trigger AEA signalling pathways that, in turn, may impact decidualisation and the angiogenic ability of uNK cells.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Primary uNK cell responses are based on a simple in vitro model. Thus, in complex microenvironments, such as the feto-maternal interface, the mechanisms may not be exactly the same. Also, the inflammatory events of miscarriage that, in this study, have happened prior to processing of the samples may cause different responses to that observed. In addition, the magnitude of the inflammatory response, required to trigger the AEA pathways that impact decidualisation and the uNK angiogenic ability in vivo, is still unclear.

WIDER IMPLICATIONS OF THE FINDINGS

The endocannabinoid AEA is a modulator of reproductive competence. AEA not only may contribute to neuroendocrine homeostasis but also can take part in uterine changes occurring during early pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

The work was supported by UID/MULTI/04378/2019 with funding from Fundação para a Ciência e a Tecnologia (FCT)/MCTES through national funds and PORTUGAL 2020 Partnership Agreement, NORTE-01-0145-FEDER-000024. S.C. Cunha acknowledges FCT for the IF/01616/2015 contract. There are no conflicts of interest.

Continuous human uterine NK cell differentiation in response to endometrial regeneration and pregnancy

Immune cell differentiation is critical for adequate tissue-specific immune responses to occur. Here, we studied differentiation of human uterine natural killer cells (uNK cells). These cells reside in a tissue undergoing constant regeneration and represent the major leukocyte population at the maternal-fetal interface. However, their physiological response during the menstrual cycle and in pregnancy remains elusive. By surface proteome and transcriptome analysis as well as using humanized mice, we identify a differentiation pathway of uNK cells in vitro and in vivo with sequential acquisition of killer cell immunoglobulin-like receptors and CD39. uNK cell differentiation occurred continuously in response to the endometrial regeneration and was driven by interleukin-15. Differentiated uNK cells displayed reduced proliferative capacity and immunomodulatory function including enhanced angiogenic capacity. By studying human uterus transplantation and monozygotic twins, we found that the uNK cell niche could be replenished from circulation and that it was under genetic control. Together, our study uncovers a continuous differentiation pathway of human NK cells in the uterus that is coupled to profound functional changes in response to local tissue regeneration and pregnancy.

The ameliorating effects of tokishakuyakusan in a rat model of implantation failure involves endometrial gland leukemia inhibitory factor and decidualization

ETHNOPHARMACOLOGICAL RELEVANCE

Tokishakuyakusan (TSS) is a Kampo medicine that is prescribed for the treatment of infertility in Japan. However, its precise mechanism of action remains unclear.

AIM OF THE STUDY

Leukemia inhibitory factor (LIF) in the endometrium plays an indispensable role in embryo implantation and is linked to infertility or implantation failure. Previously, we demonstrated that TSS ameliorated implantation failure induced by mifepristone (RU-486), an antagonist of progesterone, in rats. Herein, we aimed to clarify whether the ameliorating effect of TSS on implantation failure in the rat model involves endometrial LIF. Additionally, we determined whether decidualization, the dysfunction of which is linked to infertility or implantation failure similar to LIF, progesterone, and other implantation-related factors, are involved in the effect of TSS.

MATERIALS AND METHODS

The implantation failure rat model was developed via the subcutaneous administration of RU-486 (7 mg/kg) on day 3 post-coitus. Sesame oil was administered as the vehicle control. Rats were fed a diet containing 1% or 3% TSS or a control diet from day 13 pre-coitus. Subsequently, the implantation sites were assessed, and plasma progesterone levels were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) on day 8 post-coitus. The LIF mRNA of the endometrial gland, which was segmented via laser-microdissection from the endometrial tissue, was measured, and endometrial LIF immunostaining was carried out on day 5. The gene expression of different factors related to implantation, including decidualization and progesterone-responsiveness on days 5 and 6, were measured. The human endometrial Ishikawa cell line derived from human adenocarcinoma was treated with TSS (30-300 μg/mL) for 24 h, and the LIF concentrations in the cell culture supernatants were measured.

RESULTS

RU-486 decreased the number of implantation sites in the uterus of rats; however, the decrease was significantly alleviated by TSS (3%-diet), which tended to increase plasma progesterone. In rats with RU-486-induced implantation failure, endometrial gland LIF mRNA and endometrial LIF protein were markedly decreased while the gene expression of both decidualization-related factors such as interleukin-11, insulin-like growth factor binding protein-1, and cyclooxygenase-2, and progesterone responsive-related factors such as FK506 binding protein 5, were significantly decreased. These changes in the uterus of rats with implantation failure were significantly alleviated by TSS (3%-diet). Additionally, TSS significantly enhanced LIF protein production and LIF mRNA in Ishikawa cells.

CONCLUSIONS

The mechanism whereby TSS ameliorates RU-486-induced implantation failure in rats may involve the alleviation of decreased LIF production derived from the endometrial gland, and a dysfunction of decidualization, including lower progesterone responsiveness in the model. These findings may partly contribute to the interpretation of the beneficial effects of TSS on infertility.

Endometrial function in women with polycystic ovary syndrome: a comprehensive review

BACKGROUND

Polycystic ovary syndrome (PCOS) is the most common cause of anovulatory infertility. An endometrial component has been suggested to contribute to subfertility and poor reproductive outcomes in affected women.

OBJECTIVE AND RATIONALE

The aim of this review was to determine whether there is sufficient evidence to support that endometrial function is altered in women with PCOS, whether clinical features of PCOS affect the endometrium, and whether there are evidence-based interventions to improve endometrial dysfunction in PCOS women.

SEARCH METHODS

An extensive literature search was performed from 1970 up to July 2020 using PubMed and Web of Science without language restriction. The search included all titles and abstracts assessing a relationship between PCOS and endometrial function, the role played by clinical and biochemical/hormonal factors related to PCOS and endometrial function, and the potential interventions aimed to improve endometrial function in women with PCOS. All published papers were included if considered relevant. Studies having a specific topic/hypothesis regarding endometrial cancer/hyperplasia in women with PCOS were excluded from the analysis.

OUTCOMES

Experimental and clinical data suggest that the endometrium differs in women with PCOS when compared to healthy controls. Clinical characteristics related to the syndrome, alone and/or in combination, may contribute to dysregulation of endometrial expression of sex hormone receptors and co-receptors, increase endometrial insulin-resistance with impaired glucose transport and utilization, and result in chronic low-grade inflammation, immune dysfunction, altered uterine vascularity, abnormal endometrial gene expression and cellular abnormalities in women with PCOS. Among several interventions to improve endometrial function in women with PCOS, to date, only lifestyle modification, metformin and bariatric surgery have the highest scientific evidence for clinical benefit.

WIDER IMPLICATIONS

Endometrial dysfunction and abnormal trophoblast invasion and placentation in PCOS women can predispose to miscarriage and pregnancy complications. Thus, patients and their health care providers should advise about these risks. Although currently no intervention can be universally recommended to reverse endometrial dysfunction in PCOS women, lifestyle modifications and metformin may improve underlying endometrial dysfunction and pregnancy outcomes in obese and/or insulin resistant patients. Bariatric surgery has shown its efficacy in severely obese PCOS patients, but a careful evaluation of the benefit/risk ratio is warranted. Large scale randomized controlled clinical trials should address these possibilities.

C-Peptide Inhibits Decidualization in Human Endometrial Stromal Cells via GSK3β-PP1

Decidualization refers to the functional differentiation of endometrial stromal cells and plays a significant role in embryo implantation and pregnancy. C-peptide is excreted in equimolar concentrations as that of insulin during the metabolism of proinsulin in pancreatic beta-cells. High levels of C-peptide are correlated with hyperinsulinemia and polycystic ovarian syndrome, which show a defect in decidualization. However, the role of C-peptide in decidualization has not yet been studied. Here, we identified C-peptide as an endogenous antideciduogenic factor. This inhibitory function was confirmed by the reduced expression of decidual markers, including prolactin, insulin-like growth factor-binding protein-1, and Forkhead box protein O1 as well as by the fibroblastic morphological change in the presence of C-peptide. C-peptide also enhanced cellular senescence and decreased the proportion of apoptotic cells during decidualization. In addition, C-peptide potentiated the inhibitory effects of both insulin and palmitic acid in an AKT- and autophagy-independent manner, respectively. Furthermore, C-peptide augmented protein phosphatase 1 (PP1) activity, leading to a reduction in the inhibitory phosphorylation of glycogen synthase kinase (GSK)3β, which resulted in enhanced cellular senescence and decreased apoptosis during decidualization. Taken together, our findings suggest that C-peptide is an antideciduogenic factor acting via the regulation between PP1 and GSK3β in patients with hyperinsulinemia.

Insulin regulation of solute carrier family 2 member 1 (glucose transporter 1) expression and glucose uptake in decidualizing human endometrial stromal cells: an in vitro study

BACKGROUND

Solute carrier family 2 member 1 (SLC2A1; previously known as glucose transporter 1), is the most abundant glucose transporter in human endometrium and is up-regulated during decidualization, whereas high insulin may have a negative impact on this process. The present study aimed to investigate the effect of insulin on the expression of SLC2A1 and glucose uptake in decidualizing human endometrial stromal cells.

METHODS

We induced in vitro decidualization of endometrial stromal cells obtained from regularly menstruating healthy non-obese women. The cells were treated with increasing concentrations of insulin, and the involvement of the transcription factor forkhead box O1 (FOXO1) was evaluated using a FOXO1 inhibitor. SLC2A1 mRNA levels were measured by Real-Time PCR and protein levels were evaluated by immunocytochemistry. Glucose uptake was estimated by an assay quantifying the cellular uptake of radioactive glucose. One-way ANOVA, Dunnett's multiple comparisons test and paired t-test were used to determine the statistical significance of the results.

RESULTS

We found that insulin dose-dependently decreased SLC2A1 mRNA levels and decreased protein levels of SLC2A1 in decidualizing human endometrial stromal cells. Transcriptional inactivation of FOXO1 seems to explain at least partly the down-regulation of SLC2A1 by insulin. Glucose uptake increased upon decidualization, whereas insulin treatment resulted in a slight inhibition of the glucose uptake, although not significant for all insulin concentrations.

CONCLUSIONS

These results indicate an impairment of decidualization by high concentrations of insulin. Future studies will determine the clinical significance of our results for endometrial function and decidualization in women with insulin resistance and hyperinsulinemia.

Copper and lead exposures disturb reproductive features of primary endometrial stromal and epithelial cells

This study investigates if Cu and Pb act as endocrine disruptors affecting endometrial cells. Primary EnSCs and EnECs were exposed to Cu (0, 50, 100 and 200 μM) or Pb (0, 30, 100 and 500 μM) and assessed for viability, decidualization, apoptosis and proliferation on EnSCs, and wound healing and adhesion capabilities on EnECs. Cu exposure decreased significantly cell viability in a dose-dependent manner. Cu and Pb negatively affected in vitro decidualization, showing a significant decrease in PRL secretion. HOXA10 and ERα mRNA levels significantly decreased in decidualized cells (dEnSCs) exposed to Cu. Cu and Pb decreased adhesion and regeneration capability in EnEC. This study reveals that Cu and Pb could negatively affect endometrial functionality, compromising the decidualization process and disrupting endometrial regeneration and embryo adhesion. Therefore, special care should be taken considering heavy metals exposure if pregnancy is being pursued.

Dihydrotestosterone potentiates insulin to up-regulate prokineticin-1 in decidualizing human endometrial stromal cells

Prokineticin 1 (PROK1) is a key regulator of embryo implantation and placentation, and its dysregulation is associated with pregnancy complications, such as pre‐eclampsia and foetal growth restriction. We have previously shown that insulin strongly enhances the expression of PROK1 in human decidualizing stromal cells. Here, we demonstrate that dihydrotestosterone (DHT), but not testosterone, potentiates insulin to up‐regulate PROK1 in these cells. However, the androgens alone do not influence the expression of PROK1. Our findings suggest that insulin and androgens both are involved in the regulation of PROK1 that could have implications for normal and pathological pregnancies.

Endometrial stromal cells exhibit a distinct phenotypic and immunomodulatory profile

BACKGROUND

In Asherman's syndrome (AS), intrauterine scarring and fibrotic adhesions lead to menstrual disorders, pregnancy loss, or infertility. A few clinical trials have piloted cell therapy to overcome AS. Understanding the role of the stromal compartment in endometrial regeneration remains poorly understood. We hypothesize that endometrial stromal cells (eSCs) represent a relevant cell population to establish novel cell-based therapeutics for endometrial disorders. The aim of this study was to characterize eSCs and evaluate their immune-cell interactions.

METHODS

eSCs were isolated from healthy donors, during the proliferative stage of the menstrual cycle. Cells were characterized for expression of mesenchymal stromal cell (MSC) markers and assessed for their tumorigenic potential. eSCs were co-cultured with interferon γ and tumor necrosis factor α, and cell surface expression of their respective receptors and human leukocyte antigen (HLA) I and II determined by flow cytometry. Secreted levels of key immunomodulatory factors were established. eSCs were cultured with activated peripheral blood mononuclear cells, and T cell differentiation and proliferation determined.

RESULTS

eSCs demonstrated an MSC surface phenotype and exhibited multipotency. Expanded eSCs retained chromosomal stability and demonstrated no tumorigenicity. Upon stimulation, eSCs licensed to an anti-inflammatory phenotype with upregulated secretion of immunomodulatory factors. Stimulated eSCs did not express HLA class II. eSCs suppressed the proliferation and activation of CD4+ T cells, with the eSC secretome further downregulating central memory T cells and upregulating effector memory (EM) cells.

CONCLUSIONS

Differential responsiveness to inflammation by eSCs, compared to other MSC sources, demonstrates the need to understand the specific functional effects of individual stromal cell sources. A lack of HLA class II and triggering of EM T cell differentiation strongly links to innate in vivo roles of eSCs in tissue repair and immune tolerance during pregnancy. We conclude that eSCs may be an ideal cell therapy candidate for endometrial disorders.

Insulin Signaling Via Progesterone-Regulated Insulin Receptor Substrate 2 is Critical for Human Uterine Decidualization

Decidualization, the process by which fibroblastic human endometrial stromal cells (HESC) differentiate into secretory decidual cells, is a critical event during the establishment of pregnancy. It is dependent on the steroid hormone progesterone acting through the nuclear progesterone receptor (PR). Previously, we identified insulin receptor substrate 2 (IRS2) as a factor that is directly regulated by PR during decidualization. IRS2 is an adaptor protein that functionally links receptor tyrosine kinases, such as insulin receptor (IR) and insulin-like growth factor 1 receptor (IGF1R), and their downstream effectors. IRS2 expression was induced in HESC during in vitro decidualization and siRNA-mediated downregulation of IRS2 transcripts resulted in attenuation of this process. Further use of siRNAs targeted to IR or IGF1R transcripts showed that downregulation of IR, but not IGF1R, led to impaired decidualization. Loss of IRS2 transcripts in HESC suppressed phosphorylation of both ERK1/2 and AKT, downstream effectors of insulin signaling, which mediate gene expression associated with decidualization and regulate glucose uptake. Indeed, downregulation of IRS2 resulted in reduced expression and membrane localization of the glucose transporters GLUT1 and GLUT4, resulting in lowered glucose uptake during stromal decidualization. Collectively, these data suggest that the PR-regulated expression of IRS2 is necessary for proper insulin signaling for controlling gene expression and glucose utilization, which critically support the decidualization process to facilitate pregnancy. This study provides new insight into the mechanisms by which steroid hormone signaling intersects with insulin signaling in the uterus during decidualization, which has important implications for pregnancy complications associated with insulin resistance and infertility.

Transcriptional Regulation of INSR, the Insulin Receptor Gene

The insulin receptor gene encodes an evolutionarily conserved signaling protein with a wide spectrum of functions in metazoan development. The insulin signaling pathway plays key roles in processes such as metabolic regulation, growth control, and neuronal function. Misregulation of the pathway features in diabetes, cancer, and neurodegenerative diseases, making it an important target for clinical interventions. While much attention has been focused on differential pathway activation through ligand availability, sensitization of overall signaling may also be mediated by differential expression of the insulin receptor itself. Although first characterized as a “housekeeping” gene with stable expression, comparative studies have shown that expression levels of the human INSR mRNA differ by tissue and in response to environmental signals. Our recent analysis of the transcriptional controls affecting expression of the Drosophila insulin receptor gene indicates that a remarkable amount of DNA is dedicated to encoding sophisticated feedback and feed forward signals. The human INSR gene is likely to contain a similar level of transcriptional complexity; here, we summarize over three decades of molecular biology and genetic research that points to a still incompletely understood regulatory control system. Further elucidation of transcriptional controls of INSR will provide the basis for understanding human genetic variation that underlies population-level physiological differences and disease.

Endometrial expression of receptivity markers subject to ovulation induction agents

PURPOSE

Implantation rates differ according to ovulation induction agents in ART. This study investigates the different local endometrial effects of LH- versus hCG-induced ovulation.

METHODS

Endometrial stromal cells from healthy patients were cultured with hCG or LH in different concentrations, supplemented with 250 ng/mL hCG and progesterone after 2 and 5 days. In addition after decidualization induction, cells were treated with hCG (50 or 250 ng/mL) or LH (10 or 50 ng/mL) for 3 days. Receptivity markers expression was evaluated by real-time quantitative PCR on day 3 and 6.

RESULTS

On day 3, non-decidualized cells treated with LH showed an increased expression of IGFBP1, IL-8 and CXCL12 compared to hCG. The expression pattern changed on day 6, where cells treated with hCG showed higher expression of implantation markers compared to LH-treated cells. Furthermore, on day 3, decidualized cells treated with hCG250 showed an increased IL8 and CXCL12 expression compared to LH10.

CONCLUSIONS

LH seems to modulate the local endometrial expression of receptivity markers earlier compared to hCG; however, the effect is not sustained over time in cells without prior decidualization. Though, in decidualized cells, pattern changed and an earlier positive effect of hCG was shown on IL-8 and CXCL12.

Decidualization of the human endometrium

BACKGROUND

Decidualization of the human endometrium, which involves a dramatic morphological and functional differentiation of human endometrial stromal cells (ESCs), is essential for the establishment of a successful pregnancy. Decidualization results from a complex interplay of transcription factors, morphogens, cytokines, cell cycle regulators, and signaling pathways.

METHODS

Based on a literature review, the regulation of, and the molecular mechanisms involved in, the decidualization of the endometrium are described.

MAIN FINDINGS

Progesterone, together with proteins that are regulated by progesterone and/or cyclic adenosine monophosphate, including homeobox A10, forkhead box O1, signal transducers and activators of transcription, and heart and neural crest derivatives expressed transcript 2, forms a critical network for ESC decidualization and is a prerequisite to successful implantation. Decidualized ESCs contribute to the microenvironment at the feto-maternal interface and its direct or indirect influence on extracellular matrix remodeling, regulation of the local immune response, anti-oxidative stress, and angiogenesis (vascular maturation). Impairment of this process is associated with a variety of pregnancy disorders, including infertility, recurrent miscarriages, and uteroplacental disorders.

CONCLUSION

A deeper understanding of the process of decidualization is expected to provide new insights into the fields of reproductive biology and reproductive medicine.

Prokineticin 1 is up-regulated by insulin in decidualizing human endometrial stromal cells

Prokineticin 1 (PROK1), a hypoxia‐regulated angiogenic factor, has emerged as a crucial regulator of embryo implantation and placentation. Dysregulation of PROK1 has been linked to recurrent pregnancy loss, pre‐eclampsia, foetal growth restriction and preterm birth. These pregnancy complications are common in women with obesity and polycystic ovary syndrome, i.e. conditions associated with insulin resistance and compensatory hyperinsulinaemia. We investigated the effect of insulin on PROK1 expression during in vitro decidualization. Endometrial stromal cells were isolated from six healthy, regularly menstruating women and decidualized in vitro. Insulin induced a significant dose‐dependent up‐regulation of PROK1 on both mRNA and protein level in decidualizing endometrial stromal cells. This up‐regulation was mediated by hypoxia‐inducible factor 1‐alpha (HIF1α) via the phosphatidylinositol 3‐kinase (PI3K) pathway. Furthermore, we demonstrated that PROK1 did not affect the viability, but significantly inhibited the migration of endometrial stromal cells and the migratory and invasive capacity of trophoblast cell lines. This in vitro study provides new insights into the regulation of PROK1 by insulin in human decidualizing endometrial stromal cells, the action of PROK1 on migration of endometrial stromal cells, as well as migration and invasion of trophoblasts. We speculate that hyperinsulinaemia may be involved in the mechanisms by which PROK1 is linked to placenta‐related pregnancy complications.