Implication of the RAGE-EN-RAGE axis in endometriosis

Potential mechanism of Luoshi Neiyi prescription in endometriosis based on serum pharmacochemistry and network pharmacology

Introduction

Endometriosis (EMs) is characterized by ectopic growth of active endometrial tissue outside the uterus. The Luoshi Neiyi prescription (LSNYP) has been extensively used for treating EMs in China. However, data on the active chemical components of LSNYP are insufficient, and its pharmacological mechanism in EMs treatment remains unclear. This study aimed to explore the potential mechanism of LSNYP for EMs through network pharmacology based on the components absorbed into the blood.

Methods

Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry was used to analyze blood components, and a series of network pharmacology strategies were utilized to predict targets of these components and EMs. Protein-protein interaction (PPI) network analysis, component-target-disease network construction, gene ontology (GO) functional enrichment analysis, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed. Additionally, molecular docking, molecular dynamics simulations, and in vitro and in vivo experiments were conducted to validate the HIF1A/EZH2/ANTXR2 pathway associated with hypoxic pathology in EMs.

Results

Thirty-four absorbed components suitable for network pharmacology analysis were identified, and core targets, such as interleukin 6, EGFR, HIF1A, and EZH2, were founded. Enrichment results indicated that treatment of EMs with LSNYP may involve the regulation of hypoxia and inflammatory-related signaling pathways and response to oxidative stress and transcription factor activity. Experimental results demonstrated that LSNYP could decrease the expression of HIF1A, ANTXR2, YAP1, CD44, and β-catenin, and increased EZH2 expression in ectopic endometrial stromal cells and endometriotic tissues. Molecular docking and molecular dynamics simulations manifested that there was stable combinatorial activity between core components and key targets of the HIF1A/EZH2/ANTXR2 pathway.

Conclusion

LSNYP may exert pharmacological effects on EMs via the HIF1A/EZH2/ANTXR2 pathway; hence, it is a natural herb-related therapy for EMs.

Multicenter evaluation of blood-based biomarkers for the detection of endometriosis and adenomyosis: A prospective non-interventional study

OBJECTIVE

To evaluate blood-based biomarkers to detect endometriosis and/or adenomyosis across nine European centers (June 2014-April 2018).

METHODS

This prospective, non-interventional study assessed the diagnostic accuracy of 54 blood-based biomarker immunoassays in samples from 919 women (aged 18-45 years) with suspicion of endometriosis and/or adenomyosis versus symptomatic controls. Endometriosis was stratified by revised American Society for Reproductive Medicine stage. Symptomatic controls were "pathologic symptomatic controls" or "pathology-free symptomatic controls". The main outcome measure was receiver operating characteristic-area under the curve (ROC-AUC) and Wilcoxon P values corrected for multiple testing (q values).

RESULTS

CA-125 performed best in "all endometriosis cases" versus "all symptomatic controls" (AUC 0.645, 95% confidence interval [CI] 0.600-0.690, q < 0.001) and increased (P < 0.001) with disease stage. In "all endometriosis cases" versus "pathology-free symptomatic controls", S100-A12 performed best (AUC 0.692, 95% CI 0.614-0.769, q = 0.001) followed by CA-125 (AUC 0.649, 95% CI 0.569-0.729, q = 0.021). In "adenomyosis only cases" versus "symptomatic controls" or "pathology-free symptomatic controls", respectively, the top-performing biomarkers were sFRP-4 (AUC 0.615, 95% CI 0.551-0.678, q = 0.045) and S100-A12 (AUC 0.701, 95% CI 0.611-0.792, q = 0.004).

CONCLUSION

This study concluded that no biomarkers tested could diagnose or rule out endometriosis/adenomyosis with high certainty.

Follicular fluid advanced glycation end products in assisted reproduction: A systematic review

Follicular fluid (FF) advanced glycation end products (AGEs) have been associated with low oocyte quality and number, low fertilization rate, impaired embryonic development and low pregnancy rate. These findings are especially relevant in women undergoing in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), ie, assisted reproductive technology (ART). A systematic literature search was conducted to examine various AGEs including pentosidine, carboxymethyl-lysine (CML), methylglyoxal 5-hydro-5-methylimidazolones (MG-H1), toxic AGE (TAGE), and soluble receptor for AGE (sRAGE) with ART outcomes. Studies showed that total AGEs and sRAGE in FF were associated with the ovarian response, follicle number, retrieved oocyte number, mature (MII) oocyte number, fertilization rate, embryo number, embryo quality, and successful pregnancy. Although FF AGEs could be considered predictive biomarkers, population heterogeneity and differences in ovulation induction protocols make the findings less clear. This review highlights important role of AGEs in ART and necessity of evaluating AGEs in serum vs with FF to better predict ART outcomes.

Does the Use of the "Proseek® Multiplex Inflammation I Panel" Demonstrate a Difference in Local and Systemic Immune Responses in Endometriosis Patients with or without Deep-Infiltrating Lesions?

Endometriotic lesions are able to infiltrate surrounding tissue. This is made possible partly by an altered local and systemic immune response that helps achieve neoangiogenesis, cell proliferation and immune escape. Deep-infiltrating endometriosis (DIE) differs from other subtypes through the invasion of its lesions over 5 mm into affected tissue. Despite the invasive nature of these lesions and the wider range of symptoms they can trigger, DIE is described as a stable disease. This elicits the need for a better understanding of the underlying pathogenesis. We used the "Proseek^® Multiplex Inflammation I Panel" in order to simultaneously detect 92 inflammatory proteins in plasma and peritoneal fluid (PF) of controls and patients with endometriosis, as well as in particular patients with DIE, in order to gain a better insight into the systemically and locally involved immune response. Extracellular newly identified receptor for advanced gycation end-products binding protein (EN-RAGE), C-C motif Chemokine ligand 23 (CCL23), Eukaryotic translation initiation factor 4-binding protein 1 (4E-BP1) and human glial cell-line derived neurotrophic factor (hGDNF) were significantly increased in plasma of endometriosis patients compared to controls, whereas Hepatocyte Growth factor (HGF) and TNF-related apoptosis inducing ligand (TRAIL) were decreased. In PF of endometriosis patients, we found Interleukin 18 (IL-18) to be decreased, yet Interleukin 8 (IL-8) and Interleukin 6 (IL-6) to be increased. TNF-related activation-induced cytokine (TRANCE) and C-C motif Chemokine ligand 11 (CCL11) were significantly decreased in plasma, whereas C-C motif Chemokine ligand 23 (CCL23), Stem Cell Factor (SCF) and C-X-C motif chemokine 5 (CXCL5) were significantly increased in PF of patients with DIE compared to endometriosis patients without DIE. Although DIE lesions are characterized by increased angiogenetic and pro-inflammatory properties, our current study seems to support the theory that the systemic immune system does not play a major role in the pathogenesis of these lesions.

Higher fibrotic content of endometriotic lesions is associated with diminished prostaglandin E2 signaling

Purpose

While the prevailing view holds that the prostaglandin E2 (PGE₂) signaling plays a vital role in endometriosis, PGE₂ also is known to be anti-fibrotic. We investigated the immunostaining of COX-2, EP2, and EP4, along with fibrotic content in ovarian endometrioma (OE) and deep endometriosis (DE) lesions, and in OE lesions from adolescent and adult patients. In addition, we evaluated the effect of substrate stiffness on the expression of COX-2, EP2, and EP4 in endometrial stromal cells.

Methods

Immunohistochemistry analysis of COX-2, EP2, and EP4, along with the quantification of lesional fibrosis, was conducted for OE and DE lesion samples and also OE lesion samples from adolescent and adult patients. The effect of substrate rigidity on fibroblast-to-myofibroblast transdifferentiation (FMT) and the expression of COX-2, EP2, and EP4, with or without TGF-β1 stimulation, were investigated.

Results

The immunostaining of COX-2, EP2, and EP4 was substantially reduced in endometriotic lesions as lesions became more fibrotic. Both TGF-β1 stimulation and stiff substrates induced FMT and reduced the expression of COX-2, EP2, and EP4.

Conclusions

Since fibrosis is a common feature of endometriosis, our results thus cast doubts on the use of therapeutics that suppresses the PGE₂ signaling pathway, either by inhibiting COX-2 or EP2/EP4.

Immunomodulatory Factors in Primary Endometrial Cell Cultures Isolated from Cancer and Noncancerous Human Tissue-Focus on RAGE and IDO1

Background: Immune modulatory factors like indoleamine 2,3-dioxygenase 1 (IDO1) generating kynurenine (Kyn) and receptor for advanced glycation end-products (RAGE) contribute to endometrial and cancer microenvironment. Using adequate experimental models is needed to learn about the significance of these molecular factors in endometrial biology. In this paper we study IDO1 activity and RAGE expression in the in vitro cultured primary human endometrial cells derived from cancerous and noncancerous tissue. Methods: The generated primary cell cultures from cancer and noncancerous endometrial tissues were characterized using immunofluorescence and Western Blot for expression of endometrial and cancer markers. IDO1 activity was studied by Kyn quantification with High Performance Liquid Chromatography with Diode Array Detector. Results: The primary cultures of endometrial cells were obtained with 80% success rate and no major genetic aberrations. The cells retained in vitro expression of markers (mucin MUC1 and HER2) or immunomodulatory factors (RAGE and IDO1). Increased Kyn secretion was associated with cancer endometrial cell culture in contrast to the control one. Conclusions: Primary endometrial cells express immune modulatory factors RAGE and IDO1 in vitro associated with cancer phenotype of endometrium.

Association of Follicular Fluid Advanced Glycation End-Products with Oocyte Response and Clinical Pregnancy in Assisted Reproduction Cycles

Context:

Advanced glycation end-products (AGEs) are toxic metabolic end-products of lipids, nucleic acids, and proteins. Their accumulation in the ovaries can alter the follicular microenvironment and affect stimulation response.

Aims:

We aimed to study the association of AGEs in follicular fluid (FF AGE) with oocyte response and clinical pregnancy in ART-Assisted Reproductive Technology cycles.

Settings and Design:

This prospective study involved 84 individuals undergoing ART.

Methods and Material:

FF was collected during oocyte retrieval, and the level of AGEs was measured by enzyme-linked immunosorbent assay. Oocyte response was grouped as below target (<7 MII oocytes) or above target response (≥7 MII).

Statistical Analysis Used:

The association of FF AGE with the oocyte response and clinical pregnancy rate was analyzed by Mann–Whitney U-test. The strength of association of FF AGE with the outcome variables was analyzed with receiver operating characteristic (ROC) curve.

Results:

The median FF AGE was 17.6 (8.5) μg/ml. It was significantly higher in the below target than the normal ovarian response group (18.5 [17.8] vs. 16.3 [7.8] μg/ml, P = 0.046). Similarly, it was significantly higher in those who did not conceive (19.9 [7.3] vs. 13.5 [5.9] μg/ml, P < 0.001). The cutoff of FF AGE obtained by ROC curve analysis was 16.5 μg/ml above which there were significantly lower oocyte response and clinical pregnancy.

Conclusions:

Elevated FF AGE can be a significant negative predictor of clinical pregnancy and ovarian response to stimulation in ART cycles. The FF AGE level above the cutoff value of 16.5 μg/ml was associated with significantly lower oocyte response and clinical pregnancy.

The role of advanced glycation end products in human infertility

Advanced glycation end products (AGEs) are heterogeneous products of the non-enzymatic interaction between proteins and reducing sugars. Numerous studies have shown that AGEs are associated with senescence, diabetes, vascular disease, aging and kidney disease. Infertility has been affected approximately 10 to15% of couples of reproductive ages. AGEs accumulation has been shown to play a crucial role in pathogenesis of infertility-related diseases. The present review provides the generation process, mechanism and pathological significance of AGEs and the novel treatment targeting AGEs for infertility.

Plasma High Mobility Group Box 1 (HMGB1), Osteopontin (OPN), and Hyaluronic Acid (HA) as Admissible Biomarkers for Endometriosis

Identification of biomarkers for endometriosis is an unmet medical need that demands to be fulfilled. In this study, we first used a mouse model of endometriosis and evaluated the potential utility of select biomarkers based on serial observations. Since fibrosis is the end result of lesional development, we chose high mobility group box 1 (HMGB1), osteopontin (OPN), and hyaluronic acid (HA), all three of them have been well documented to be involved in endometriosis and fibrosis, as potential biomarkers. In addition, we performed immunohistochemistry analysis of HMGB1, OPN, and the receptors for HMGB1, such as toll-like receptor 4 (TLR4), nuclear factor κB (NF-κB), proliferating cell nuclear antigen (PCNA), interleukin-33 (IL-33), and receptor for advanced glycation endproducts (RAGE)–a pattern recognition receptor, with HMGB1 being its important ligand. We then evaluated the same set of putative markers in 30 women with ovarian endometriomas and 20 without endometriosis, and reevaluated the 3 plasma markers 3 months after the surgical removal of all visible endometriotic lesions. In mouse, the lesional staining levels of OPN, RAGE, and IL-33 were all significantly higher than that of normal endometrium, and increased progressively as lesions progressed. In contrast to HMGB1, TLR4, p-p65 and PCNA staining levels were decreased progressively. In humans, lesional staining levels of OPN correlated positively, while that of HMGB1 correlated negatively with the extent of fibrosis. All three plasma markers correlated positively with the extent of lesional fibrosis. Through this integrated approach, we identified plasma HMGB1, OPN and HA as promising admissible biomarkers for endometriosis.

Prognostic values of S100 family members in ovarian cancer patients

Objective

Exhibiting high consistence in sequence and structure, S100 family members are interchangeable in function and they show a wide spectrum of biological processes, including proliferation, apoptosis, migration, inflammation and differentiation and the like. While the prognostic value of each individual S100 in ovarian cancer is still elusive. In current study, we investigated the prognostic value of S100 family members in the ovarian cancer.

Methods

We used the Kaplan Meier plotter (KM plotter) database, in which updated gene expression data and survival information are from 1657 ovarian cancer patients, to assess the relevance of individual S100 family mRNA expression to overall survival in various ovarian cancer subtypes and different clinicopathological features.

Results

It was found that high expression of S100A2 (HR = 1.18, 95%CI: 1.04–1.34, P = 0.012), S100A7A (HR = 1.3, 95%CI: 1.04–1.63, P = 0.02),S100A10 (HR = 1.2, 95%CI: 1.05–1.38, P = 0.0087),and S100A16 (HR = 1.23, 95%CI: 1–1.51, P = 0.052) were significantly correlated with worse OS in all ovarian cancer patients, while the expression of S100A1 (HR = 0.87, 95%CI: 0.77–0.99, P = 0.039), S100A3 (HR = 0.83, 95%CI: 0.71–0.96, P = 0.0011), S100A5 (HR = 0.84, 95%CI: 0.73–0.97, P = 0.017), S100A6 (HR = 0.84, 95%CI: 0.72–0.98, P = 0.024), S100A13 (HR = 0.85, 95%CI:0.75–0.97, P = 0.014) and S100G (HR = 0.86, 95%CI: 0.74–0.99, P = 0.041) were associated with better prognosis. Furthermore, we assessed the prognostic value of S100 expression in different subtypes and the clinicopathological features, including pathological grades, clinical stages and TP53 mutation status, of ovarian cancer patients.

Conclusion

Comprehensive understanding of the S100 family members may have guiding significance for the diagnosis and outcome of ovarian cancer patients.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5170-3) contains supplementary material, which is available to authorized users.

Advanced glycation end product concentrations in follicular fluid of women undergoing IVF/ICSI with a GnRH agonist protocol

The accumulation of advanced glycation end products (AGE) is associated with ovarian dysfunction. This study examines whether the accumulation of AGE in follicular fluid affects ovarian responsiveness and embryo quality during IVF/intracytoplasmic sperm injection (IVF/ICSI) with a gonadotrophin-releasing hormone (GnRH) agonist protocol. The levels of AGE in follicular fluid were measured in 127 women undergoing IVF/ICSI in GnRH agonist cycles. Plasma hormones were also measured. Embryos were graded using standard approaches. There were inverse associations between follicular fluid AGE concentration and number of oocytes retrieved, number of fertilized oocytes, number of high-quality embryos, fertilization rate and high-quality embryo rate, adjusted for potential confounders. AGE concentration in follicular fluid was significantly higher in women with an ovarian response below the target (<7 oocytes) compared with those reaching the target (7-15 oocytes) or above the target (>15 oocytes). The cut-off value of 15.3 µg/ml for follicular fluid AGE showed 84.6% sensitivity and 55.5% specificity in evaluating the response to ovarian stimulation as below the target. The results suggest that ovarian responsiveness and embryo quality are related to intraovarian exposure to AGE.

Intrafollicular soluble RAGE benefits embryo development and predicts clinical pregnancy in infertile patients of advanced maternal age undergoing in vitro fertilization

Soluble receptor for advanced glycation end products (sRAGE) can decoy the toxic AGEs and is considered to be a protective factor. This study aimed to evaluate the correlation between intrafollicular sRAGE levels and clinical outcomes in infertile women of young or advanced maternal age (AMA) undergoing in vitro fertilization (IVF). A total of 62 young women and 62 AMA women who would undergo IVF were included in this prospective study. The intrafollicular sRAGE concentration was measured to determine its association with the number of retrieved oocytes, fertilized oocytes, high-quality embryos or achievement of clinical pregnancy in young and AMA women, respectively. Besides, correlations between sRAGE and age or follicle-stimulating hormone (FSH) were examined. We found that the intrafollicular sRAGE levels were higher in young patients than those in AMA patients, suggesting that the sRAGE levels were inversely correlated with age. In young patients, sRAGE showed no correlation with the number of retrieved oocytes, fertilized oocytes, high-quality embryos or achievement of clinical pregnancy. But it was found that AMA patients with more retrieved oocytes, fertilized oocytes and high-quality embryos demonstrated higher sRAGE levels, which were a prognostic factor for getting clinical pregnancy independent of age or FSH level. In conclusion, the sRAGE levels decrease with age. Elevated intrafollicular sRAGE levels indicate good follicular growth, fertilization and embryonic development, and successful clinical pregnancy in AMA women, while in young women, the role of sRAGE may not be so predominant.

Follicular fluid soluble receptor for advanced glycation endproducts (sRAGE): a potential protective role in polycystic ovary syndrome

PURPOSE

To explore the relationships between the soluble receptor for advanced glycation endproducts (sRAGE) and the outcome parameters following in vitro fertilization-embryo transfer (IVF-ET) in patients with polycystic ovary syndrome (PCOS) and investigate the protective effect of sRAGE in PCOS development regarding inflammation.

METHODS

We conducted a prospective analysis of a subsample of 74 participants from the Reproductive Medical Center of the First Affiliated Hospital of Zhengzhou University. We quantified sRAGE, vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF-α), interleukelin-6 (IL-6), and C-reactive protein (CPR) protein levels in the follicular fluid from 39 PCOS and 35 non-PCOS reproductive-age women. sRAGE and VEGF, TNF-α, IL-6, and CRP in follicular fluid aspirated without blood were measured by ELISA.

RESULTS

sRAGE concentrations in the follicular fluid were significantly lower in the PCOS group compared to those in the control group, while VEGF, TNF-α, IL-6, and CRP concentrations were significantly higher in the PCOS group than in the control group (P < 0.05). sRAGE was significantly, inversely correlated with the total dose of gonadotropin (Gn) in the PCOS group undergoing IVF treatment (r = -0.451, P = 0.004). After adjusting for age and Gn dose (in international units used per cycle), sRAGE protein levels in the follicular fluid were significantly, inversely related to VEGF (r = -0.378, P = 0.018), TNF-α (r = -0.450, P = 0.004), IL-6 (r = -0.455, P = 0.004), and CRP (r = -0.375, P = 0.019).

CONCLUSION

sRAGE in the follicular fluid might exert a protective effect against the inflammatory action of PCOS development.

Elevation of soluble form of receptor for advanced glycation end products (sRAGE) in recurrent pregnancy losses (RPL): possible participation of RAGE in RPL

OBJECTIVE

To determine whether the soluble receptor for advanced glycation end products (sRAGE) and immune inflammatory markers are associated with recurrent pregnancy losses (RPL).

DESIGN

Prospective case-control study.

SETTING

University clinic.

PATIENT(S)

A total of 93 women (age 35.8±4.6 years) were enrolled including 63 women with three or more recurrent pregnancy losses (RPL), and age-matched fertile controls with a history of at least one live birth and no history of pregnancy losses (n=30).

INTERVENTION(S)

Peripheral blood collection.

MAIN OUTCOME MEASURE(S)

Assessment of anthropometric, metabolic, and inflammatory immune variables.

RESULT(S)

Levels of sRAGE were statistically significantly higher in RPL patients than in control patients (1,528.9±704.5 vs. 1,149.9±447.4 pg/mL). In the multivariate analysis, the levels of insulin, plasminogen activator inhibitor-1, the resistance index of the uterine radial artery, and the ratio of tumor necrosis factor-α/interleukin-10 producing T helper cells were statistically significantly associated with the serum sRAGE level.

CONCLUSION(S)

Elevated levels of serum sRAGE are associated with RPL. The soluble receptor for advanced glycation end products might contribute to RPL by reducing uterine blood flow and subsequently causing ischemia in the fetus via inflammatory and thrombotic reactions.

Hormonal therapy deregulates prostaglandin-endoperoxidase synthase 2 (PTGS2) expression in endometriotic tissues

CONTEXT

Endometriosis is a common gynecologic condition characterized by an important inflammatory process mediated by the prostaglandin pathway. Oral contraceptives are the treatment of choice for symptomatic endometriotic women. However the effects of oral contraceptives use and prostaglandin pathway in endometriotic women are actually still unknown.

OBJECTIVE

To investigate the expression of prostaglandin pathway key genes in endometriotic tissue, affected or not by hormonal therapy, as compared with healthy endometrial tissue.

DESIGN

This was a comparative laboratory study.

SETTING

This study was conducted in a tertiary-care university hospital.

PATIENTS

Seventy-six women, with (n = 46) and without (n = 30) histologically proven endometriosis.

MAIN OUTCOME MEASURES

Prostaglandin-endoperoxidase synthase (PTGS)1, PTGS2, prostaglandin E receptor (PTGER)1, PTGER2, PTGER3, and PTGER4 mRNA levels in endometrium of disease-free women and in eutopic and ectopic endometrium of endometriosis-affected women. PTGS2 expression was further investigated by immunohistochemistry, using specific monoclonal antibodies. PTGS2 expression was analyzed at mRNA and protein levels and correlated with taking hormonal treatment.

RESULTS

PTGS2 expression was significantly increased in eutopic and ectopic endometrium as compared with healthy tissue (induction of 9.6- and 6.3-fold, respectively; P = .001). PTGS2 immunoreactivity increased gradually from normal endometrium to eutopic and ectopic endometrium (h-score of 96.7 ± 55.0, 128.3 ± 66.1, and 226.7 ± 62.6, respectively, P < .001). PTGER2, PTGER3, and PTGER4 expression increased significantly and gradually from normal to eutopic and ectopic endometrium, whereas PTGER1 remained unchanged. Patients under hormonal treatment had a higher PTGS2 expression at transcriptional and protein levels as compared with those without treatment (P = .002 and P = .025, respectively).

CONCLUSIONS

Prostaglandin pathway is strongly deregulated in eutopic and ectopic endometrium of women suffering from endometriosis for the benefit of an increased PTGS2 expression. We show for the first time that hormonal treatment appears to enhance even more PTGS2 expression. These results contribute to explain why medical treatment could fail to control endometriosis progression.

Advanced glycation end products and their relevance in female reproduction

STUDY QUESTION

Do advanced glycation end products (AGEs) and their receptors play a role in female reproduction?

SUMMARY ANSWER

AGEs might contribute to the etiology of polycystic ovary syndrome (PCOS) and infertility.

WHAT IS KNOWN ALREADY

The endogenous AGEs are produced in the body by chemical reactions. Exogenous sources of AGEs are diet and smoking. AGEs have been proposed to be among the main intermediaries involved in several diseases, such as metabolic syndrome, type 2 diabetes mellitus, cardiovascular disease, ovarian aging, inflammation, neurodegenerative disorders and PCOS.

STUDY DESIGN, SIZE, DURATION

A systematic review was performed for all available basic science and clinical peer-reviewed articles published in PubMed from 1987 to date. Abstracts of annual meetings of the Endocrine Society and American Society for Reproductive Medicine were also reviewed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 275 publications and scientific abstracts were identified from the initial search. Sixty-two papers and four published scientific abstracts were selected for full review. The main outcomes were the regulatory effects of AGEs on: (i) granulosa cells, adipocyte physiology, obesity and insulin resistance in women with PCOS and in polycystic ovary animal models and (ii) infertility and measures of ovarian reserve.

MAIN RESULTS AND THE ROLE OF CHANCE

There is an intricate relationship between the AGE-RAGE (receptor for AGEs) system and some aspects of PCOS, such as granulosa cell dysfunction, adipocyte pathophysiology, obesity and insulin resistance. Additionally, irregular ovarian AGE signaling might in part explain the abnormal ovarian histology observed in women with PCOS. The ovarian dysfunction due to AGEs in women without PCOS suggests a role for the AGE-RAGE system in the ovarian follicular environment, and might relate to assisted reproduction technology outcome and measures of ovarian reserve.

LIMITATIONS, REASONS FOR CAUTION

The body of literature currently available limits these findings. The results obtained from granulosa cell lines and animal models may not fully extrapolate to humans.

WIDER IMPLICATIONS OF THE FINDINGS

This review underscores a critical need to unveil the exact mechanistic actions of AGEs in reproductive physiology and more specifically the hypothalamic-pituitary-ovarian axis. AGE inhibitors might present an emerging therapeutic approach with significant applications in the context of PCOS and infertility.

STUDY FUNDING/COMPETING INTEREST(S)

American Society for Reproductive Medicine New Investigator Award and University of Vermont College of Medicine Internal Funds. No competing interests.

Intrafollicular soluble receptor for advanced glycation end products (sRAGE) and embryo quality in assisted reproduction

The developmental potential of human embryos has important implications in assisted reproduction and depends, among other factors, on oocyte competency. The receptor for advanced glycation end products (RAGE) is a member of the superfamily of immunoglobulin cell-surface molecules that are constitutively expressed during embryonic development. RAGE is down-regulated in homeostasis in adult life. This study measured the concentration of soluble RAGE (sRAGE) in follicular fluid obtained from the leading follicle after ovarian stimulation of 54 women undergoing intracytoplasmic sperm injection. Corresponding embryos and sRAGE concentrations in follicular fluid were evaluated and correlations were investigated by multi-adjusted regression analysis. High intrafollicular sRAGE concentrations predicted poor-quality embryos (n=45, OR=0.986; P=0.026), adjusted for patient age, body mass index and oocyte quality, showing an inverse association between intrafollicular sRAGE concentrations and embryo development. The developmental potential of human embryos has important implications in assisted reproduction, and it depends, among other factors, on oocyte competency. The receptor for advanced glycation end products (RAGE) is a molecule constitutively expressed during embryonic development, but it is down-regulated in adult life. RAGE is frequently associated with pro-inflammatory responses, and it is implicated as an underlying condition in immune disorders, cardiovascular diseases, diabetes, Alzheimer's disease and cancer. In addition to activating the pro-inflammatory responses, RAGE down-regulates cellular defence mechanisms. The present study measured the concentrations of soluble RAGE (sRAGE) in follicular fluid samples obtained from leading follicles of women undergoing intracytoplasmic sperm injection (ICSI). This prospective cohort study included 54 patients undergoing ICSI, and follicular fluid samples were obtained from the leading follicle after ovarian stimulation. The corresponding embryos were evaluated and correlations with intrafollicular sRAGE concentrations were investigated using multi-adjusted regression analysis. We observed that high intrafollicular concentrations of sRAGE predicted poor embryo quality. Our findings suggest an association between high concentrations of intrafollicular sRAGE and poor embryo development following ovarian stimulation for ICSI.