Molecular and preclinical basis to inhibit PGE2 receptors EP2 and EP4 as a novel nonsteroidal therapy for endometriosis

Progressively Diminished Prostaglandin E2 Signaling in Concordance with Increasing Fibrosis in Ectopic Endometrium

The prostaglandin E2 (PGE2) signaling has traditionally been viewed to play a pivotal role in endometriosis, linking inflammation and hyperestrogenism. We have previously reported that asectopic endometrium becomes more fibrotic, the expression of both COX-2 and PGE2 receptors (EP2 and EP4) are reduced. This study further investigatedwhether the expression levels of genes involved in the biosynthesis and metabolism of PGE2in ectopic endometrium diminish in concordance with increasing lesional fibrosis. We performed immunohistochemistry analyses of COX-2, mPGES-1, mPGES-2, cPGES, 15-PGDH, EP2 and EP4 and Masson trichrome staining for ovarian endometrioma (OE), adenomyosis (AD), and deep endometriosis (DE) tissue samples and control endometrial tissue samples (CT). Gene and protein expression analyses were performed by real-time RT-PCR and Western blotting, respectively. We found that as the extent of lesional fibrosis increased, immunoexpression of COX-2, mPGES-1/2, cPGES, EP2 and EP4 in OE lesions was increased but no change in these genes/proteins in DE lesions as compared with CT. Immunoexpression of COX-2 was found to be reduced while that of 15-PGDH was found to be elevated in DE lesions. In AD lesions, only EP2 and COX-2 were overexpressed. Thus, our data indicate that when the extent of lesional fibrosis is high, the PGE2 signaling pathway is depressed, manifesting as reduced COX-2 expression and elevated expression of 15-PGDH. They underscore the fact that not all ectopic endometria are the same and equal, and highlight the importance of the extracellular matrix in shaping the lesional behavior and response to drug treatment.

Cyclooxygenase 2 overexpression suppresses Smad3 and augments ERK1/2 signaling activated by TGFβ1 in endometrial stromal cells: A novel insight into endometriosis pathogenesis

RESEARCH QUESTION

To investigate the underlying mechanisms driving the opposing effects of transforming growth factor-beta 1 (TGFβ1) on the proliferation of control (CESCs) and ectopic (EESCs) endometrial stromal cells.

DESIGN

Cell proliferation assays (CCK-8 and colony formation) were employed to assess the effects of TGFβ1 on CESC and EESC proliferation. An immortalized human endometrial stromal cell line (HESC) was used to elucidate the mechanisms behind cytostatic effect of TGFβ1 and the potential role of cyclooxygenase (COX)-2 in mediating the modulation of TGFβ1 signaling.

RESULTS

This study demonstrated that TGFβ1 inhibited the proliferation of CESCs and HESCs while significantly promoting the proliferation of EESCs. In both CESCs and HESCs, TGFβ1-induced growth arrest was primarily mediated by cell cycle arrest rather than apoptosis. Mechanistically, TGFβ1 activated both Smad3 and ERK1/2 signaling pathways, with Smad3 acting to inhibit proliferation and ERK1/2 to promote it. Notably, overexpression of COX-2 in HESCs abolished the cytostatic effect of TGFβ1 by enhancing ERK1/2 signaling and decreasing Smad3 protein levels and its nuclear translocation. Similar effects were observed following prostaglandin E2 (PGE2) treatment. In contrast, inhibition of COX-2 activity in EESCs resulted in increased Smad3 expression, reduced ERK1/2 activation, and a restoration of the cytostatic effect of TGFβ1.

CONCLUSION

COX-2 modulates the effects of TGFβ1 on endometrial stromal cells by altering the balance between the Smad3 and ERK1/2 signaling pathways, thereby converting TGFβ1 from a growth inhibitor to a proliferation stimulator.

Molecular Basis of Impaired Decidualization in the Eutopic Endometrium of Endometriosis Patients

Endometriosis is a chronic gynecological disorder characterized by the presence of endometrial tissue outside the uterine cavity. A common feature of this pathology is the impaired decidualization of endometrial stromal cells, a critical process that prepares the uterus for embryo implantation. This decidualization defect has been mechanistically linked to progesterone resistance in endometriotic lesions. However, the presence and underlying mechanisms of decidualization defects in the eutopic endometrium of women with endometriosis remain controversial. The aim of the present study is to integrate and discuss molecular evidence from both in vivo and in vitro studies examining decidualization alterations in the eutopic endometrium of patients with endometriosis. Multiple studies have demonstrated impaired decidualization in the eutopic endometrium of women with endometriosis. These alterations have been reported on multiple genes, signaling pathways, and epigenetic processes. However, additional functional studies are warranted to elucidate whether these decidualization defects directly contribute to endometriosis-associated infertility. A better understanding of the decidualization process and its dysregulation in endometriosis will not only advance the development of targeted fertility treatments but also facilitate the design of more effective therapeutic strategies for managing this chronic condition.

Modelling Endometriosis Using In Vitro and In Vivo Systems

Endometriosis is a chronic inflammatory condition characterised by the presence of endometrium-like tissue outside the uterus. Despite its high prevalence and recent advances in molecular science, many aspects of endometriosis and its pathophysiology are still poorly understood. Previously, in vitro and in vivo modelling have been instrumental in establishing our current understanding of endometriosis. As the field of molecular science and the advance towards personalised medicine is ever increasing, more sophisticated models are continually being developed. These hold great potential to provide more intricate knowledge of the underlying pathophysiology and facilitate investigations into potential future approaches to diagnosis and treatment. This review provides an overview of different in vitro and in vivo models of endometriosis that are pertinent to establishing our current understanding. Moreover, we discuss new cross-cutting approaches to endometriosis modelling, such as the use of microfluidic cultures and 3D printing, which have the potential to shape the future of endometriosis research.

Synergistic inhibitory effects of tetramethylpyrazine and evodiamine on endometriosis development

Endometriosis (EMS) belongs to a gynecological disorder with inflammation and the existence of endometrial-like tissues beyond the uterus, often leading to infertility and pelvic pain. Estrogen receptor β (ERβ) is significantly expressed in endometriosis (EMS) and recognized as a promising therapeutic target for EMS treatment by inhibiting ERβ activity. In this study, we investigated the potential mechanisms for tetramethylpyrazine (TMP)-mediated ERβ suppression, and the synergistic inhibitory effect of TMP and evodiamine (EVO) on ERβ expression and EMS development. We found that TMP suppresses ERβ expression by reducing the association of Oct3/4 with the ERβ promoter and decreasing Oct3/4 protein levels without affecting Oct3/4 transcript levels. A minimum dosage of 10 µM TMP is required to inhibit ERβ expression. Neither TMP (5 µM) nor EVO (2 µM) alone had any effect, but their combination synergistically inhibited ERβ expression and modulated related cellular processes, including redox balance, mitochondrial function, inflammation, and proliferation. Additionally, the combination of TMP (10 mg/kg body weight) and EVO (5 mg/kg) synergistically inhibited ERβ expression and EMS development in the mouse model. In conclusion, TMP suppresses ERβ expression by reducing the association of Oct3/4 with the ERβ promoter. Neither TMP nor EVO alone effectively suppresses ERβ in both laboratory and live organism models. However, their combination synergistically inhibits ERβ expression and EMS development, suggesting a potential therapeutic strategy for EMS using TMP and EVO.

The relationship between blood lipids and endometriosis: a cross-sectional study from NHANES (1999-2006) and a bidirectional Mendelian randomization study

OBJECTIVE

Observational studies suggest a link between blood lipid levels and endometriosis risk, but clinical evidence is limited and causality has not been established. This study aims to clarify this relationship using NHANES data (1999-2006) and bidirectional Mendelian Randomization (MR) analysis.

METHODS

We analyzed NHANES data to explore the relationship between blood lipids and endometriosis risk using multivariable logistic regression, nonlinear testing, and trend analysis. For causal inference, MR was performed using GWAS data from the UK Biobank (lipid levels) and the Finnish Endometriosis Database (endometriosis).

RESULTS

In NHANES (n=2,201), elevated triglycerides (TG) were significantly associated with increased endometriosis risk (OR, 2.10; 95% CI, 1.00-3.49; p < 0.05). MR analysis confirmed this association (OR, 1.19; 95% CI, 1.07-1.32; p < 0.006) and suggested HDL may protect against endometriosis (OR, 0.79; 95% CI, 0.63-0.99; p < 0.05). Additionally, bidirectional MR indicated that endometriosis may also contribute to TG dysregulation (OR, 1.02; 95% CI, 1.01-1.03; p < 0.006).

CONCLUSION

Our findings suggest that elevated TG levels may increase endometriosis risk, while HDL may provide a protective effect. These results offer new insights and may inform future management strategies for endometriosis. However, large-scale longitudinal studies are needed to further validate these associations.

Dual inhibition of AKT and ERK1/2 pathways restores the expression of progesterone Receptor-B in endometriotic lesions through epigenetic mechanisms

Endometriosis is an estrogen-dependent and progesterone-resistant gynecological inflammatory disease of reproductive-age women. Progesterone resistance, loss of progesterone receptor -B (PR-B) in the stromal cells of the endometrium, is one of the hallmarks of endometriosis and a major contributing factor for infertility in endometriosis patients. Loss of PR-B in the stromal cells of the endometriotic lesions poses resistance to the success of progesterone-based therapy. The working hypothesis is that PR-B is hypermethylated and epigenetically silenced, and inhibition of AKT and ERK1/2 pathways will decrease the hypermethylation, reverse the epigenetic silencing, and restore the expression of PR-B via DNA methylation and histone modification mechanisms in the endometriotic lesions. The objectives are to (i) determine the effects of dual inhibition of AKT and ERK1/2 pathways on the expression of PR-B and DNA methylation and histone modification protein machinery in the endometriotic lesions and (ii) identify the underlying epigenetic mechanisms of PR-B restoration in the endometriotic lesions. The results indicate that dual inhibition of AKT and ERK1/2 pathways decreases the hypermethylation, reverses the epigenetic silencing, and restores the expression of PR-B via DNA methylation and H3K9 and H3K27 methylation mechanisms in the endometriotic lesions or endometriotic stromal cells of human origin. These results support the novel concept that restored expression of PR-B in the endometriotic lesions and endometrium may improve the clinical outcome of progesterone therapy in endometriosis patients.

Endometriosis: recent advances that could accelerate diagnosis and improve care

Endometriosis is a common disorder associated with pain, gastrointestinal and urinary symptoms, infertility, and fatigue. It is defined by the presence of endometrial-like lesions found predominantly in the pelvis. Mechanisms that contribute to disease aetiology include changes in hormonal, inflammatory, and pain pathways. In this article, we focus on recent developments in imaging technologies, on our improved understanding of mechanisms contributing to infertility, on drug therapies that are in clinical trials, and on insights from studies on the gut that offer potential to support self-management strategies. We postulate that improvements in the quality of life of patients will be accelerated by reframing endometriosis as a multi-system disorder and learning from treatments targeting symptoms shared between endometriosis, neuroinflammatory, and gastrointestinal disorders.

Evodiamine suppresses endometriosis development induced by early EBV exposure through inhibition of ERβ

Introduction: Endometriosis (EMS) is characterized as a prevalent gynecological inflammatory disorder marked by the existence of endometrial tissues situated beyond the uterus. This condition leads to persistent pelvic pain and may contribute to infertility. In this investigation, we explored the potential mechanism underlying the development of endometriosis (EMS) triggered by transient exposure to either latent membrane protein 1 (LMP1) or Epstein-Barr virus (EBV) in a mouse model. Additionally, we examined the potential inhibitory effect of evodiamine (EDM) on EMS. Methods: Immortalized human endometrial stromal cells (HESC) or epithelial cells (HEEC) were transiently exposed to either EBV or LMP1. The presence of evodiamine (EDM) was assessed for its impact on estrogen receptor β (ERβ) expression, as well as on cell metabolism parameters such as redox balance, mitochondrial function, inflammation, and proliferation. Additionally, a mixture of LMP1-treated HESC and HEEC was administered intraperitoneally to generate an EMS mouse model. Different dosages of EDM were employed for treatment to evaluate its potential suppressive effect on EMS development. Results: Transient exposure to either EBV or LMP1 triggers persistent ERβ expression through epigenetic modifications, subsequently modulating related cell metabolism for EMS development. Furthermore, 4.0 µM of EDM can efficiently reverse this effect in in vitro cell culture studies. Additionally, 20 mg/kg body weight of EDM treatment can partly suppress EMS development in the in vivo EMS mouse model. Conclusion: Transient EBV/LMP1 exposure triggers permanent ERβ expression, favoring later EMS development, EDM inhibits EMS development through ERβ suppression. This presents a novel mechanism for the development of endometriosis (EMS) in adulthood stemming from early Epstein-Barr virus (EBV) exposure during childhood. Moreover, evodiamine (EDM) stands out as a prospective candidate for treating EMS.

HIF-1α regulates DcR3 to promote the development of endometriosis

OBJECTIVE

The aim of this study was to investigate the expression and clinical significance of HIF-1α and DcR3 in endometriosis by analysing clinical case data. Tissue samples were collected for tissue chip analysis and staining, and human endometrial stromal cells were isolated and cultured for cell experiments. Additionally, experiments were conducted on collected peritoneal fluid to explore the association and role of HIF-1α and DcR3 in endometriosis.

STUDY DESIGN

Patients who visited the Department of Obstetrics and Gynaecology at Central Hospital in Fengxian District, Shanghai, from January 2018 to December 2021 were recruited for this controlled study. Clinical data and tissue chip staining results were collected for multiple regression analysis on the clinical significance of HIF-1α and DcR3. Endometrial tissue, ovarian cysts, and pelvic fluid were collected, and human endometrial stromal cells were cultured. The impact of HIF-1α on DcR3 in different oxygen environments and its role in endometriosis were investigated through PCR, Western blotting, enzyme-linked immunosorbent assay, as well as adhesion and migration assays.

RESULTS

In patients with endometriosis, the expression of DcR3 and HIF-1α was found to be upregulated and correlated in ectopic endometrium. The expression of DcR3 served as an indicator of the severity of endometriosis. Hypoxia induced the expression of DcR3, which was regulated by HIF-1α and promoted migration and adhesion.

CONCLUSION

DcR3 can be used as a clinical indicator to assess the severity of endometriosis. The hypoxic environment in endometriosis enhances disease progression by regulating DcR3 through HIF-1α.

Revisiting prostaglandin E2: A promising therapeutic target for osteoarthritis

Osteoarthritis (OA) is a complex disease characterized by cartilage degeneration and persistent pain. Prostaglandin E2 (PGE2) plays a significant role in OA inflammation and pain. Recent studies have revealed the significant role of PGE2-mediated skeletal interoception in the progression of OA, providing new insights into the pathogenesis and treatment of OA. This aspect also deserves special attention in this review. Additionally, PGE2 is directly involved in pathologic processes including aberrant subchondral bone remodeling, cartilage degeneration, and synovial inflammation. Therefore, celecoxib, a commonly used drug to alleviate inflammatory pain through inhibiting PGE2, serves not only as an analgesic for OA but also as a potential disease-modifying drug. This review provides a comprehensive overview of the discovery history, synthesis and release pathways, and common physiological roles of PGE2. We discuss the roles of PGE2 and celecoxib in OA and pain from skeletal interoception and multiple perspectives. The purpose of this review is to highlight PGE2-mediated skeletal interoception and refresh our understanding of celecoxib in the pathogenesis and treatment of OA.

Progesterone resistance in endometriosis: A pathophysiological perspective and potential treatment alternatives

Background

Endometriosis is a common gynecological disease affecting women of reproductive age. Patients with endometriosis frequently experience severe chronic pain and have higher chances to experience infertility. Progesterone resistance is a major problem that develops during the medical treatment of endometriosis, which often leads to treatment failure of hormonal therapies. Previous studies indicated that the dysregulation of progesterone receptors (PR) is the primary factor leading to progesterone resistance in endometriosis.

Methods

This review article systematically reviewed and summarized findings extracted from previously published papers available on PubMed, encompassing both experimental studies and clinical trials.

Main findings

Various determinants influencing PR expression in endometriosis have been identified, including the environmental toxins, microRNAs, cell signaling pathways, genetic mutations, and the pro-inflammatory cytokines. The selective estrogen/progesterone receptor modulators have emerged as novel therapeutic approaches for treating endometriosis, offering potential improvements in overcoming progesterone resistance.

Conclusion

Concerns and limitations persist despite the newly developed drugs. Therefore, studies on unraveling new therapeutic targets based on the molecular mechanisms of progesterone resistance is warranted for the development potential alternatives to overcome hormonal treatment failure in endometriosis.

The Unmet Needs for Studying Chronic Pelvic/Visceral Pain Using Animal Models

The different definitions of chronic pelvic/visceral pain used by international societies have changed over the years. These differences have a great impact on the way researchers study chronic pelvic/visceral pain. Recently, the role of systemic changes, including the role of the central nervous system, in the perpetuation and chronification of pelvic/visceral pain has gained weight. Consequently, researchers are using animal models that resemble those systemic changes rather than using models that are organ- or tissue-specific. In this review, we discuss the advantages and disadvantages of using bladder-centric and systemic models, enumerating some of the central nervous system changes and pain-related behaviors occurring in each model. We also present some drawbacks when using animal models and pain-related behavior tests and raise questions about possible, yet to be demonstrated, investigator-related bias. We also suggest new approaches to study chronic pelvic/visceral pain by refining existing animal models or using new ones.

Emerging hallmarks of endometriosis metabolism: A promising target for the treatment of endometriosis

Endometriosis, characterized by ectopic endometrium growth in the extrauterine environment, is one of the most notable diseases of the female reproductive system. Worldwide, endometriosis affects nearly 10 % of women in their reproductive years and causes a significant decline in quality of life. Despite extensive investigations of endometriosis over the past years, the mechanisms of endometriosis pathogenesis remain unclear. In recent years, metabolic factors have increasingly been considered factors in endometriosis. There is compelling evidence regarding the progress of endometriosis in the context of severe metabolic dysfunction. Hence, the curative strategies and ongoing attempts to conquer endometriosis might start with metabolic pathways. This review focuses on metabolic mechanisms and summarizes current research progress. These findings provide valuable information for the non-intrusive diagnosis of the disease and may contribute to the understanding of the pathogenesis of endometriosis.

Effects of selective inhibition of prostaglandin E2 receptors EP2 and EP4 on the miRNA profile in endometriosis

Endometriosis is an estrogen-dependent, progesterone-resistant, chronic inflammatory gynecological disease of reproductive-age women. Two major clinical symptoms of endometriosis are chronic pelvic pain and infertility, which profoundly affect the quality of life in women. Current hormonal therapies to induce a hypoestrogenic state are unsuccessful because of undesirable side effects, reproductive health concerns, and failure to prevent disease recurrence. Prostaglandin E₂ (PGE₂) plays an important role in the survival and growth of endometriotic lesions. MicroRNAs (miRNAs) are small, noncoding RNAs that control gene expressions through multiple mechanisms and have important roles in the pathogenesis of endometriosis. The objective of the present study is to determine the effects of pharmacological inhibition of PGE₂ receptors, EP2 and EP4, on miRNA profile in endometriosis. The novel results collectively indicate that inhibition of PGE₂-EP2/EP4 signaling regulated several miRNA clusters associated with cell adhesion, migration, invasion, survival and growth in cell-specific and the chromosome-specific manner and reverses the epigenetic silencing of proapoptotic miRNAs 15a and 34c in the human endometriotic epithelial and stromal cells and experimental endometriotic lesions. Thus, selective inhibition of EP2/EP4 receptors could emerge as a potential nonsteroidal therapy for endometriosis.

Endometriosis-associated infertility: From pathophysiology to tailored treatment

Despite the clinically recognized association between endometriosis and infertility, the mechanisms implicated in endometriosis-associated infertility are not fully understood. Endometriosis is a multifactorial and systemic disease that has pleiotropic direct and indirect effects on reproduction. A complex interaction between endometriosis subtype, pain, inflammation, altered pelvic anatomy, adhesions, disrupted ovarian reserve/function, and compromised endometrial receptivity as well as systemic effects of the disease define endometriosis-associated infertility. The population of infertile women with endometriosis is heterogeneous, and diverse patients' phenotypes can be observed in the clinical setting, thus making difficult to establish a precise diagnosis and a single mechanism of endometriosis related infertility. Moreover, clinical management of infertility associated with endometriosis can be challenging due to this heterogeneity. Innovative non-invasive diagnostic tools are on the horizon that may allow us to target the specific dysfunctional alteration in the reproduction process. Currently the treatment should be individualized according to the clinical situation and to the suspected level of impairment. Here we review the etiology of endometriosis related infertility as well as current treatment options, including the roles of surgery and assisted reproductive technologies.

[Mystery of endometriosis - catamenial pneumothorax]

The review is devoted to clinical picture, main theories of pathogenesis, traditional and innovative methods of diagnosis and surgical treatment of catamenial pneumothorax. Currently, clinicians prefer magnetic resonance imaging and thoracoscopy for diagnosis of this disease. Various researchers are actively searching for laboratory diagnostic methods that can confirm endometrioid nature of pneumothorax. Treatment and prevention of catamenial pneumothorax are a controversial issue depending both clinical picture and preferences of the attending physician. Currently, the majority of authors believe that hormonal therapy combined with diaphragm resection ensures optimal anti-relapse effect in patients with thoracic endometriosis.

Lysophospholipid Mediators in Health and Disease

Lysophospholipids, exemplified by lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P), are produced by the metabolism and perturbation of biological membranes. Both molecules are established extracellular lipid mediators that signal via specific G protein-coupled receptors in vertebrates. This widespread signaling axis regulates the development, physiological functions, and pathological processes of all organ systems. Indeed, recent research into LPA and S1P has revealed their important roles in cellular stress signaling, inflammation, resolution, and host defense responses. In this review, we focus on how LPA regulates fibrosis, neuropathic pain, abnormal angiogenesis, endometriosis, and disorders of neuroectodermal development such as hydrocephalus and alopecia. In addition, we discuss how S1P controls collective behavior, apoptotic cell clearance, and immunosurveillance of cancers. Advances in lysophospholipid research have led to new therapeutics in autoimmune diseases, with many more in earlier stages of development for a wide variety of diseases, such as fibrotic disorders, vascular diseases, and cancer.

Effects of dual inhibition of AKT and ERK1/2 pathways on endometrial pro-inflammatory, hormonal, and epigenetic microenvironment in endometriosis

Endometriosis is an estrogen-dependent and progesterone-resistant gynecological inflammatory disease of reproductive-age women. The prevalence of endometriosis is ~5-10% in reproductive-age women, increasing to 20-30% in women with subfertility. The current anti-estrogen therapies can be prescribed only for a short time because of the undesirable side effects on menstruation, pregnancy, bone health, and failure to prevent a recurrence. The causes of endometriosis-associated infertility are multifactorial and poorly understood. The objective of the present study was to determine the inhibitory effects of AKT and/or ERK1/2 pathways on the microenvironment of the endometrium in a xenograft mouse model of endometriosis of human origin. Results indicate that dual inhibition of AKT and ERK1/2 pathways, but not inhibition of either AKT or ERK1/2 pathway, suppresses the growth of the endometriotic lesions in vivo. Dual inhibition of AKT and ERK1/2 pathways suppresses the production of proinflammatory cytokines, decreases E₂ biosynthesis and signaling, and restores progesterone receptor-B signaling components in the epithelial and stromal cells of the endometrium in a cell-specific manner. These results together suggest that dual inhibition of AKT and ERK1/2 pathways suppresses the estrogen-dominant state and concomitantly increases the progesterone-responsive state of the endometrium. Therefore, dual inhibition of AKT and ERK1/2 pathways could emerge as long-term nonsteroidal therapy for endometriosis.

Prostaglandin E receptor 2 mediates the inducible effects of prostaglandin E2 on expression of growth factors and enzymes in cattle endometrial epithelial cells and explants

Prostaglandin E₂ (PGE₂ ) is able to induce the expression of several growth factors and enzymes in cattle endometria. However, the specific type of PGE₂ receptors which mediates this effect is not fully clear. In this study, the role of prostaglandin E receptor 2 (PTGER2) in PGE₂ -mediated induction of growth factors and enzymes expression in cattle endometrial explants and epithelial cells were investigated. PTGER2 was blocked by a PTGER2 antagonist, AH6809, before PGE₂ treatment, then the mRNA and protein expression levels of several growth factors and enzymes were compared with that in PGE₂ alone treatment group by real-time RT-PCR and Western blotting analysis in endometrial epithelial cells and explants. Results indicated that PGE₂ significantly increased the mRNA and protein levels of these growth factors and enzymes, while the rates of increment in the expression of these growth factors and enzymes were inhibited by AH6809. In addition, a PTGER2 agonist, butaprost, significantly increased the expression levels of these growth factors and enzymes, and the effect could be blocked by AH6809. In conclusion, PTGER2 was found to be one dominant receptor mediating the inducible effects of PGE₂ on the expression of these growth factors and enzymes in cattle endometrial explants and epithelial cells.

Changing prostaglandin E2 (PGE2) signaling during lesional progression and exacerbation of endometriosis by inhibition of PGE2 receptor EP2 and EP4

Purpose

We investigated the change, if any, in prostaglandin E2 (PGE₂) signaling in endometriotic lesions of different developmental stages in mouse. In addition, we evaluated the effect of treatment of mice with induced deep endometriosis (DE) with inhibitors of PGE₂ receptor subtypes EP2 and EP4 and metformin.

Methods

Three mouse experimentations were conducted. In Experiment 1, female Balb/C mice were induced with endometriosis or DE and were serially sacrificed after induction. Experiments 2 and 3 evaluated the effect of treatment with EP2 and EP4 inhibitors and metformin, respectively, in mice with induced DE. Immunohistochemistry analysis of COX-2, EP2, and EP4, along with the extent of lesional fibrosis, was evaluated.

Results

The immunostaining of COX-2, EP2, and EP4 turned from activation to a stall as lesions progressed. Treatment with EP2/EP4 inhibitors in DE mice exacerbated endometriosis-associated hyperalgesia and promoted fibrogenesis in lesions even though it suppressed the PGE₂ signaling dose-dependently. In contrast, treatment with metformin resulted in increased PGE₂ signaling, concomitant with improved hyperalgesia, and retarded lesional fibrogenesis.

Conclusions

The PGE₂ signaling diminishes as endometriotic lesions progress. Treatment with EP2/EP4 inhibitors in DE mice exacerbates endometriosis, but metformin appears to be promising seemingly through the induction of the PGE₂ signaling.

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.

Differential Expression of Prostaglandin Receptors in Canine Uterus with Pyometra

The objective of the study was to ascertain the role of prostaglandins Viz., PGE₂ and PGF_2α, and their respective receptors in the pathophysiology of canine pyometra. Normal (n=6) and pyometra (n=8) affected uterus were collected from bitches undergoing ovariohysterectomy. Pyometra was graded according to histopathological alterations. The levels of PGE₂ and PGF_2α were estimated in the endometrium. The differential expression in the mRNA of PGF_2α receptor (FP) and PGE₂ receptors (EP1, EP2, EP3, and EP4) were studied in the endometrium and myometrium of the pyometra-affected uterus. Normal uterus served as calibrator. Elevation of both PGE₂ and PGF_2α levels in the endometrium of pyometra-affected bitches was observed. The FP receptor gene in the endometrium and myometrium of pyometra-affected bitches was down-regulated (P<0.05). Out of all EP receptors, only EP2 receptor has shown up-regulation in both endometrium and myometrium of pyometra affected uterus. EP3 receptor got down-regulated in both endometrium and myometrium in pyometra. Thus, down-regulation of FP, EP3 receptors in the myometrium reinforces the lack of contractility in pyometra-affected bitches favoring bacterial proliferation and subsequent pus accumulation. Moreover, upregulation of EP2 receptors in the pyometra bitches suggests the scope of selective pharmacological inhibition of EP2 receptors as an adjunct therapy in the treatment of pyometra.

Low-dose aspirin can downregulate progesterone resistance and increase the expression of LIF in endometriosis during the implantation window

AIM

Study the effect of low-dose aspirin on the endometrial receptivity in endometriosis rat models.

MATERIALS AND METHODS

This study is to explore the expressions of progesterone receptor and LIF among three groups of endometriosis rat models: control group (n = 12), EMs group (n = 15), and aspirin group (n = 17). The expressions of progesterone receptor (PR), PRA, PRB, and leukemia inhibitory factor receptor (LIFR) in eutopic endometrium were determined using immunohistochemistry technology, western blot, and qRT-PCR. The levels of LIF in eutopic endometrium and serum were detected by western blot, qRT-PCR, and ELISA.

RESULTS

The expressions of PR, PRA, and PRB protein were significantly increased in the eutopic endometrium after low-dose aspirin treatment, and the level of PRB mRNA was also increased while the ratio of PRA/PRB mRNA was decreased in the eutopic endometrium. The levels of LIF in eutopic endometrium and serum were increased compared with the untreated endometriosis rats. However, the expression of LIFR was not statistically different among the three groups.

CONCLUSIONS

The results suggest that the low-dose aspirin treatment could downregulate progesterone resistance and increase the expression of LIF of endometriosis rats during the implantation window, which could improve endometrial receptivity and enhance the pregnant rate of endometriosis. It may provide a potential treatment method for endometriosis-related infertility.

Kappa opioid receptor modulation of endometriosis pain in mice

The kappa opioid receptor is a constituent of the endogenous opioid analgesia system widely expressed in somatosensory nervous pathways and also in endometrial tissues. This work investigates the possible involvement of kappa opioid receptor on the nociceptive, behavioral and histopathological manifestations of endometriosis in a murine model. Female mice receiving endometrial implants develop a persistent mechanical hypersensitivity in the pelvic area that is stronger during the estrus phase of the estrous cycle. The kappa opioid receptor agonist U50,488H produces a dose-dependent relief of this mechanical hypersensitivity, regardless of the cycle phase. Repeated exposure to a low dose of U50,488H (1 mg/kg/day s.c. for one month) provides sustained relief of mechanical hypersensitivity, without tolerance development or sedative side effects. Interestingly, this treatment also inhibits a decreased rearing behavior associated with spontaneous pain or discomfort in endometriosis mice. This KOR-mediated pain relief does not prevent the anxiety-like behavior or the cognitive impairment exhibited by endometriosis mice, and the growth of endometriotic cysts is also unaltered. These data provide evidence of strong pain-relieving properties of kappa opioid receptor stimulation in female mice with endometriosis pain. The persistence of affective and cognitive manifestations suggests that these comorbidities are independent of pelvic pain and simultaneous treatment of these comorbidities may be necessary for successful management of endometriosis.

Use of selective PGE2 receptor antagonists on human endometriotic stromal cells and peritoneal macrophages

Non-hormonal therapeutic strategies for endometriosis are needed. The aim of this study was to characterize the effects of prostaglandin (PG)E2 receptor inhibitors to explore their potential as novel therapeutic strategies for endometriosis. The expression of PGE2 receptors (EP2 and EP4) in donated tissues from human ovarian endometriosis, adenomyosis and peritoneal endometriosis was examined using immunohistochemistry. Human endometriotic stromal cells (ESC) isolated from ovarian endometriotic tissue and peritoneal macrophages were treated with EP2 and EP4 antagonists. cAMP accumulation and the effect of EP antagonists were measured using cAMP assays. DNA synthesis in ESC was detected using bromodeoxyuridine incorporation analysis. Interleukin (IL)-6 and IL-8 protein levels in ESC supernatants were measured using ELISAs. mRNA expression level for aromatase by ESC, and selected cytokines by peritoneal macrophages was measured using RT-PCR. EP2 and EP4 receptors were expressed in cells derived from control and diseased tissue, ovarian endometriotic, adenomyotic and peritoneal lesions. A selective EP2 antagonist reduced DNA synthesis, cAMP accumulation and IL-1β-induced proinflammatory cytokine secretion and aromatase expression. A selective EP4 antagonist negated IL-1β-induced IL-6 secretion and aromatase expression. In peritoneal macrophages, EP expression was elevated in endometriosis samples but the EP4 antagonist reduced cAMP levels and expression of vascular endothelial growth factor, chemokine ligand 2 and chemokine ligand 3 mRNA. EP2 and EP4 are functioning in endometriosis lesions and peritoneal macrophages, and their selective antagonists can reduce EP-mediated actions, therefore, the EP antagonists are potential therapeutic agents for controlling endometriosis.

Inflammatory Mediators and Pain in Endometriosis: A Systematic Review

BACKGROUND

pain is one of the main symptoms of endometriosis and it has a deleterious effect on a patients' personal and social life. To date, the clinical management of pain includes prolonged medication use and, in some cases, surgery, both of which are disruptive events for patients. Hence, there is an urgency for the development of a sufficient non-invasive medical treatment. Inflammation is one of the causative factors of pain in endometriosis. It is well established that inflammatory mediators promote angiogenesis and interact with the sensory neurons inducing the pain signal; the threshold of pain varies and it depends on the state and location of the disease. The inhibition of inflammatory mediators' synthesis might offer a novel and effective treatment of the pain that is caused by inflammation in endometriosis.

OBJECTIVES

patients with endometriosis experience chronic pelvic pain, which is moderate to severe in terms of intensity. The objective of this systematic review is to highlight the inflammatory mediators that contribute to the induction of pain in endometriosis and present their biological mechanism of action. In addition, the authors aim to identify new targets for the development of novel treatments for chronic pelvic pain in patients with endometriosis.

DATA SOURCES

three databases (PubMed, Scopus, and Europe PMC) were searched in order to retrieve articles with the keywords 'inflammation, pain, and endometriosis' between the review period of 1 January 2016 to 31 December 2020. This review has been registered with PROSPERO (registry number: CRD42020171018). Eligibility Criteria: only original articles that presented the regulation of inflammatory mediators and related biological molecules in endometriosis and their contribution in the stimulation of pain signal were included.

DATA EXTRACTION

two authors independently extracted data from articles, using predefined criteria.

RESULTS

the database search yielded 1871 articles, which were narrowed down to 56 relevant articles of interest according to the eligibility criteria.

CONCLUSIONS

inflammatory factors that promote angiogenesis and neuroangiogenesis are promising targets for the treatment of inflammatory pain in endometriosis. Specifically, CXC chemokine family, chemokine fractalkine, and PGE2 have an active role in the induction of pain. Additionally, IL-1β appears to be the primary interleukin (IL), which stimulates the majority of the inflammatory factors that contribute to neuroangiogenesis along with IL-6. Finally, the role of Ninj1 and BDNF proteins needs further investigation.

Three-Dimensional Biofabrication Models of Endometriosis and the Endometriotic Microenvironment

Endometriosis occurs when endometrial-like tissue grows outside the uterine cavity, leading to pelvic pain, infertility, and increased risk of ovarian cancer. The present study describes the optimization and characterization of cellular spheroids as building blocks for Kenzan scaffold-free method biofabrication and proof-of-concept models of endometriosis and the endometriotic microenvironment. The spheroid building blocks must be of a specific diameter (~500 μm), compact, round, and smooth to withstand Kenzan biofabrication. Under optimized spheroid conditions for biofabrication, the endometriotic epithelial-like cell line, 12Z, expressed high levels of estrogen-related genes and secreted high amounts of endometriotic inflammatory factors that were independent of TNFα stimulation. Heterotypic spheroids, composed of 12Z and T-HESC, an immortalized endometrial stromal cell line, self-assembled into a biologically relevant pattern, consisting of epithelial cells on the outside of the spheroids and stromal cells in the core. 12Z spheroids were biofabricated into large three-dimensional constructs alone, with HEYA8 spheroids, or as heterotypic spheroids with T-HESC. These three-dimensional biofabricated constructs containing multiple monotypic or heterotypic spheroids represent the first scaffold-free biofabricated in vitro models of endometriosis and the endometriotic microenvironment. These efficient and innovative models will allow us to study the complex interactions of multiple cell types within a biologically relevant microenvironment.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Multiple Roles of Prostaglandin E2 Receptors in Female Reproduction

Among prostaglandins, Prostaglandin E2 (PGE2) (PGE2) is considered especially important for decidualization, ovulation, implantation and pregnancy. Four major PGE2 receptor subtypes, EP1, EP2, EP3, EP4, as well as peroxisome proliferator-activated receptors (PPARs), mediate various PGE2 effects via their coupling to distinct signaling pathways. This review summarizes up-to-date literatures on the role of prostaglandin E2 receptors in female reproduction, which could provide a broad perspective to guide further research in this field. PGE2 plays an indispensable role in decidualization, ovulation, implantation and pregnancy. However, the precise mechanism of Prostaglandin E2 (EP) receptors in the female reproductive system is still limited. More investigations should be performed on the mechanism of EP receptors in the pathological states, and the possibility of EP agonists or antagonists clinically used in improving reproductive disorders.

Autonomic nervous system and inflammation interaction in endometriosis-associated pain

Endometriosis is a chronic inflammatory disease. Pain is the most common symptom in endometriosis. Endometriosis-associated pain is caused by inflammation, and is related to aberrant innervation. Although the specific mechanism between endometriosis-associated pain and the interaction of aberrant innervation and inflammation remains unclear, many studies have confirmed certain correlations between them. In addition, we found that some chronic inflammatory autoimmune diseases (AIDs) such as inflammatory bowel disease (IBD) and rheumatoid arthritis (RA) share similar characteristics: the changes in dysregulation of inflammatory factors as well as the function and innervation of the autonomic nervous system (ANS). The mechanisms underlying the interaction between the ANS and inflammation have provided new advances among these disorders. Therefore, the purpose of this review is to compare the changes in inflammation and ANS in endometriosis, IBD, and RA; and to explore the role and possible mechanism of sympathetic and parasympathetic nerves in endometriosis-associated inflammation by referring to IBD and RA studies to provide some reference for further endometriosis research and treatment.

Disease-modifying effects of natural Δ9-tetrahydrocannabinol in endometriosis-associated pain

Endometriosis is a chronic painful disease highly prevalent in women that is defined by growth of endometrial tissue outside the uterine cavity and lacks adequate treatment. Medical use of cannabis derivatives is a current hot topic and it is unknown whether phytocannabinoids may modify endometriosis symptoms and development. Here we evaluate the effects of repeated exposure to Δ9-tetrahydrocannabinol (THC) in a mouse model of surgically-induced endometriosis. In this model, female mice develop mechanical hypersensitivity in the caudal abdomen, mild anxiety-like behavior and substantial memory deficits associated with the presence of extrauterine endometrial cysts. Interestingly, daily treatments with THC (2 mg/kg) alleviate mechanical hypersensitivity and pain unpleasantness, modify uterine innervation and restore cognitive function without altering the anxiogenic phenotype. Strikingly, THC also inhibits the development of endometrial cysts. These data highlight the interest of scheduled clinical trials designed to investigate possible benefits of THC for women with endometriosis.

Endometriosis is a common disease in women caused by tissue that lines the uterus growing outside the uterine cavity on to other organs in the pelvis. This can cause a variety of symptoms including chronic pelvic pain, infertility, and pain during menstruation or sexual intercourse. These symptoms may contribute to anxiety, depression, loss of working ability and a reduced quality of life.

Currently available treatments for endometriosis, including hormonal therapy and surgery, have a limited effect and can produce unwanted side effects. For example, women who undergo surgery to remove the growths may experience post-surgical pain or a recurrence. As a result, women with endometriosis often rely on self-management strategies like dietary changes or exercise. Although cannabis consumption has a large number of potential side effects and can lead to substance abuse, it has been shown to provide pain relief in some conditions. But it is unknown whether it could be useful for treating endometriosis.

Now, Escudero-Lara et al. have created a mouse model that mimics some of the conditions of human endometriosis: pelvic pain, anxiety and memory impairments. The mice were treated with moderate doses of Δ9-tetrahydrocannabinol (THC), which is the main pain-relieving component of cannabis. The THC reduced pelvic pain and cognitive impairments in the mice with the endometriosis-like condition, but it had no effect on their anxious behavior. Escudero-Lara et al. also noticed that endometrial growths were also smaller in the treated mice indicating that THC may also inhibit endometriosis development.

These experiments suggest that THC may be a useful treatment for patients with endometriosis. Clinical trials are already ongoing to test whether these findings translate to patients with the condition. Although THC and cannabis are readily available in some areas, Escudero-Lara et al. discourage using unregulated cannabis products due to the potential risks.

Disease-modifying effects of natural Δ9-tetrahydrocannabinol in endometriosis-associated pain

Endometriosis is a chronic painful disease highly prevalent in women that is defined by growth of endometrial tissue outside the uterine cavity and lacks adequate treatment. Medical use of cannabis derivatives is a current hot topic and it is unknown whether phytocannabinoids may modify endometriosis symptoms and development. Here we evaluate the effects of repeated exposure to Δ9-tetrahydrocannabinol (THC) in a mouse model of surgically-induced endometriosis. In this model, female mice develop mechanical hypersensitivity in the caudal abdomen, mild anxiety-like behavior and substantial memory deficits associated with the presence of extrauterine endometrial cysts. Interestingly, daily treatments with THC (2 mg/kg) alleviate mechanical hypersensitivity and pain unpleasantness, modify uterine innervation and restore cognitive function without altering the anxiogenic phenotype. Strikingly, THC also inhibits the development of endometrial cysts. These data highlight the interest of scheduled clinical trials designed to investigate possible benefits of THC for women with endometriosis.

Endometriosis-related chronic pelvic pain: A mini review on pathophysiology and impact on mental health

Endometriosis-related chronic pelvic pain is a major component of the disease that affects quality of life in women of reproductive age suffering from endometriosis. The present review summarizes current evidence upon pathophysiology and its impact on mental health. It seems that endometriosis-related chronic pelvic pain is the result of chronic stress on the central nervous system as a consequence of chronic pelvic inflammation. Mental health issues may rise as a result of central nervous system derangement and further aggravate pain perception and therefore quality of life. Further properly designed studies are needed in order to elucidate the connection between mental disorders and endometriosis-related chronic pelvic pain.

Endometriosis-Associated Pain - Do Preclinical Rodent Models Provide a Good Platform for Translation?

Pelvic pain is a common symptom of endometriosis. Our understanding of its etiology remains incomplete and medical management is limited by poor translation from preclinical models to clinical trials. In this review, we briefly consider the evidence, or lack thereof, that different subtypes of lesion, extra-uterine bleeding, and neuropathic pathways add to the complex and heterogeneous pain experience of women with the condition. We summarize the studies in rodent models of endometriosis that have used behavioral endpoints (evoked and non-evoked) to explore mechanisms of endometriosis-associated pain. Lesion innervation, activation of nerves by pronociceptive molecules released by immune cells, and a role for estrogen in modulating hyperalgesia are key endometriosis-associated pain mechanisms replicated in preclinical rodent models. The presence of ectopic (full thickness uterus or endometrial) tissue may be associated with changes in the spinal cord and brain, which appear to model changes reported in patients. While preclinical models using rats and mice have yielded insights that appear relevant to mechanisms responsible for the development of endometriosis-associated pain, they are limited in scope. Specifically, most studies are based on models that only resulted in the formation of superficial lesions and use induced (evoked) behavioral 'pain' tests. We suggest that translation for patient benefit will be improved by new approaches including models of ovarian and deep infiltrating disease and measurement of spontaneous pain behaviors. Future studies must also capitalize on new advances in the wider field of pain medicine to identify more effective treatments for endometriosis-associated pain.

Aldo-keto reductase 1C3-Assessment as a new target for the treatment of endometriosis

Endometriosis is a common gynecological disorder, which is treated surgically and/ or pharmacologically with an unmet clinical need for new therapeutics. A completed phase I trial and a recent phase II trial that investigated the steroidal aldo-keto reductase 1C3 (AKR1C3) inhibitor BAY1128688 in endometriosis patients prompted this critical assessment on the role of AKR1C3 in endometriosis. This review includes an introduction to endometriosis with emphasis on the roles of prostaglandins and progesterone in its pathophysiology. This is followed by an overview of the major enzymatic activities and physiological functions of AKR1C3 and of the data published to date on the expression of AKR1C3 in endometriosis at the mRNA and protein levels. The review concludes with the rationale for using AKR1C3 inhibitors, a discussion of the effects of AKR1C3 inhibition on the pathophysiology of endometriosis and a brief overview of other drugs under clinical investigation for this indication.

γ-Secretase inhibition affects viability, apoptosis, and the stem cell phenotype of endometriotic cells

INTRODUCTION

Stem cells mediate cyclic regeneration of the endometrium. The upregulated expression of receptors and modulators of the notch signaling pathway in endometriosis suggests an involvement in the pathogenetic process. Here, we investigated the effects of notch pathway inhibition by a γ-secretase inhibitor (GSI) on stemness-associated properties of the epithelial endometriotic cell line 12Z and of primary endometriotic stroma cells.

MATERIAL AND METHODS

12Z cells and primary endometriotic stroma cells of 7 patients were treated with or without GSI, and analyzed for changes in gene expression by TaqMan low-density arrays, quantitative PCR, and flow cytometry. The functional impact of GSI treatment was studied by MTT assay, cell cycle analysis, colony formation assay, annexin V apoptosis assay, and aldehyde dehydrogenase activity assays.

RESULTS

In 12Z cells, GSI treatment reduced aldehyde dehydrogenase activity and colony formation, and induced a shift to the G2/M phase of the cell cycle. Cell viability was decreased and apoptosis was increased in both cell models. GSI further induced transcriptional downregulation of the stemness-associated factors leukemia inhibitory factor receptor (LIFR), sex-determining region Y (SRY)- box 2, interferon-induced transmembrane protein 1, and hes-related family bHLH transcription factor with YRPW motif 1, in 12Z cells and in primary cell cultures. Downregulation of LIFR expression by GSI was confirmed at the protein level by flow cytometry.

CONCLUSIONS

Our in vitro data suggest that application of GSI may be a worthwhile approach in the treatment of endometriosis that warrants further investigation.

Endometriosis

Pelvic endometriosis is a complex syndrome characterized by an estrogen-dependent chronic inflammatory process that affects primarily pelvic tissues, including the ovaries. It is caused when shed endometrial tissue travels retrograde into the lower abdominal cavity. Endometriosis is the most common cause of chronic pelvic pain in women and is associated with infertility. The underlying pathologic mechanisms in the intracavitary endometrium and extrauterine endometriotic tissue involve defectively programmed endometrial mesenchymal progenitor/stem cells. Although endometriotic stromal cells, which compose the bulk of endometriotic lesions, do not carry somatic mutations, they demonstrate specific epigenetic abnormalities that alter expression of key transcription factors. For example, GATA-binding factor-6 overexpression transforms an endometrial stromal cell to an endometriotic phenotype, and steroidogenic factor-1 overexpression causes excessive production of estrogen, which drives inflammation via pathologically high levels of estrogen receptor-β. Progesterone receptor deficiency causes progesterone resistance. Populations of endometrial and endometriotic epithelial cells also harbor multiple cancer driver mutations, such as KRAS, which may be associated with the establishment of pelvic endometriosis or ovarian cancer. It is not known how interactions between epigenomically defective stromal cells and the mutated genes in epithelial cells contribute to the pathogenesis of endometriosis. Endometriosis-associated pelvic pain is managed by suppression of ovulatory menses and estrogen production, cyclooxygenase inhibitors, and surgical removal of pelvic lesions, and in vitro fertilization is frequently used to overcome infertility. Although novel targeted treatments are becoming available, as endometriosis pathophysiology is better understood, preventive approaches such as long-term ovulation suppression may play a critical role in the future.

Discovery and optimization of pyridyl-cycloalkyl-carboxylic acids as inhibitors of microsomal prostaglandin E synthase-1 for the treatment of endometriosis

Here we report on novel and potent pyridyl-cycloalkyl-carboxylic acid inhibitors of microsomal prostaglandin E synthase-1 (PTGES). PTGES produces, as part of the prostaglandin pathway, prostaglandin E2 which is a well-known driver for pain and inflammation. This fact together with the observed upregulation of PTGES during inflammation suggests that blockade of the enzyme might provide a beneficial treatment option for inflammation related conditions such as endometriosis. Compound 5a, a close analogue of the screening hit, potently inhibited PTGES in vitro, displayed excellent PK properties in vitro and in vivo and demonstrated efficacy in a CFA-induced pain model in mice and in a rat dyspareunia endometriosis model and was therefore selected for further studies.

Regulatory roles of PGE2 in LPS-induced tissue damage in bovine endometrial explants

Bovine endometritis is the most common uterine disease following parturition. The role of prostaglandin E₂ (PGE₂) in regulating normal physiological function in the bovine endometrium has been clearly established. Although PGE₂ accumulation is observed in multiple inflammatory diseases, such as endometritis, its association with pathogen-induced inflammatory damage in the endometrium is unclear. To clarify the role of PGE₂ in lipopolysaccharide (LPS)-induced endometritis in cultured bovine endometrial explants, the levels of PGE₂ secretion, prostaglandin synthetases, pro-inflammatory factors, and damage-associated molecular patterns (DAMPs) were evaluated in the present study. Significant PGE₂ accumulation in response to LPS stimulation, up-regulation of prostaglandin-endoperoxide synthase-2 (PTGS-2), microsomal prostaglandin E synthase-1 (mPGES-1), pro-inflammatory factors including interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and induced nitric oxide synthase (iNOS)/nitric oxide (NO) and DAMPs including hyaluronan binding protein 1 (HABP1) and high mobility group box-1 (HMGB1), were observed compared to the control group. LPS induced distinct damage in the bovine endometrium, characterized by morphological changes and increases in HABP1 and HMGB1 expression. PTGS-2 inhibitors CAY10404 and NS398 effectively decreased the secretion of PGE₂ and the expression of prostaglandin synthetases, pro-inflammatory factors and DAMPs, and alleviated LPS-induced tissue damage. These results indicate that PGE₂ accumulates via PTGS-2 and mPGES-1 and induces tissue damage by upregulating pro-inflammatory factors and DAMPs in LPS-treated bovine endometrial explants. These findings provide a basis for the effect of PGE₂ on LPS-treated bovine endometrium, and suggest a potential target for curing endometritis.

Dual inhibition of ERK1/2 and AKT pathways is required to suppress the growth and survival of endometriotic cells and lesions

Endometriosis is an estrogen-dependent and progesterone-resistant gynecological inflammatory disease of reproductive-age women. Current hormonal therapies targeting estrogen can be prescribed only for a short time. It indicates a need for non-hormonal therapy. ERK1/2 and AKT pathways control several intracellular signaling molecules that control growth and survival of cells. Objectives of the present study are to determine the dual inhibitory effects of ERK1/2 and AKT pathways: (i) on proliferation, survival, and apoptosis of human endometrioitc epithelial cells and stromal cells in vitro; (ii) on growth and survival of endometrioitc lesions in vivo in xenograft mouse model of endometriosis of human origin; and (iii) establish the associated ERK1/2 and AKT downstream intracellular signaling modules in the pathogenesis of endometriosis. Our results indicated that combined inhibition of ERK1/2 and AKT pathways highly decreased the growth and survival of human endometriotic epithelial cells and stromal cells in vitro and suppressed the growth of endometriotic lesions in vivo compared to inhibition of either ERK1/2 or AKT pathway individually. This cause-effect is associated with dysregulated intracellular signaling modules associated with cell cycle, cell survival, and cell apoptosis pathways. Collectively, our results indicate that dual inhibition of ERK1/2 and AKT pathways could emerge as potential non-hormonal therapy for the treatment of endometriosis.

Fractalkine/CX3CR1 Contributes to Endometriosis-Induced Neuropathic Pain and Mechanical Hypersensitivity in Rats

Pain is the most severe and common symptom of endometriosis. Its underlying pathogenetic mechanism is poorly understood. Nerve sensitization is a particular research challenge, due to the limitations of general endometriosis models and sampling nerve tissue from patients. The chemokine fractalkine (FKN) has been demonstrated to play a key role in various forms of neuropathic pain, while its role in endometriotic pain is unknown. Our study was designed to explore the function of FKN in the development and maintenance of peripheral hyperalgesia and central sensitization in endometriosis using a novel endometriosis animal model developed in our laboratory. After modeling, behavioral tests were carried out and the optimal time for molecular changes was obtained. We extracted ectopic tissues and L4-6 spinal cords to detect peripheral and central roles for FKN, respectively. To assess morphologic characteristics of endometriosis-like lesions-as well as expression and location of FKN/CX3CR1-we performed H&E staining, immunostaining, and western blotting analyses. Furthermore, inhibition of FKN expression in the spinal cord was achieved by intrathecal administration of an FKN-neutralizing antibody to demonstrate its function. Our results showed that implanted autologous uterine tissue around the sciatic nerve induced endometriosis-like lesions and produced mechanical hyperalgesia and allodynia. FKN was highly expressed on macrophages, whereas its receptor CX3CR1 was overexpressed in the myelin sheath of sciatic nerve fibers. Overexpressed FKN was also observed in neurons. CX3CR1/pp38-MAPK was upregulated in activated microglia in the spinal dorsal horn. Intrathecal administration of FKN-neutralizing antibody not only reversed the established mechanical hyperalgesia and allodynia, but also inhibited the expression of CX3CR1/pp38-MAPK in activated microglia, which was essential for the persistence of central sensitization. We concluded that the FKN/CX3CR1 signaling pathway might be one of the mechanisms of peripheral hyperalgesia in endometriosis, which requires further studies. Spinal FKN is important for the development and maintenance of central sensitization in endometriosis, and it may further serve as a novel therapeutic target to relieve persistent pain associated with endometriosis.

Chronic Niche Inflammation in Endometriosis-Associated Infertility: Current Understanding and Future Therapeutic Strategies

Endometriosis is an estrogen-dependent inflammatory disease that affects up to 10% of women of reproductive age and accounts for up to 50% of female infertility cases. It has been highly associated with poorer outcomes of assisted reproductive technology (ART), including decreased oocyte retrieval, lower implantation, and pregnancy rates. A better understanding of the pathogenesis of endometriosis-associated infertility is crucial for improving infertility treatment outcomes. Current theories regarding how endometriosis reduces fertility include anatomical distortion, ovulatory dysfunction, and niche inflammation-associated peritoneal or implantation defects. This review will survey the latest evidence on the role of inflammatory niche in the peritoneal cavity, ovaries, and uterus of endometriosis patients. Nonhormone treatment strategies that target these inflammation processes are also included. Furthermore, mesenchymal stem cell-based therapies are highlighted for potential endometriosis treatment because of their immunomodulatory effects and tropism toward inflamed lesion foci. Potential applications of stem cell therapy in treatment of endometriosis-associated infertility in particular for safety and efficacy are discussed.

The Endometriotic Tumor Microenvironment in Ovarian Cancer

Women with endometriosis are at increased risk of developing ovarian cancer, specifically ovarian endometrioid, low-grade serous, and clear-cell adenocarcinoma. An important clinical caveat to the association of endometriosis with ovarian cancer is the improved prognosis for women with endometriosis at time of ovarian cancer staging. Whether endometriosis-associated ovarian cancers develop from the molecular transformation of endometriosis or develop because of the endometriotic tumor microenvironment remain unknown. Additionally, how the presence of endometriosis improves prognosis is also undefined, but likely relies on the endometriotic microenvironment. The unique tumor microenvironment of endometriosis is composed of epithelial, stromal, and immune cells, which adapt to survive in hypoxic conditions with high levels of iron, estrogen, and inflammatory cytokines and chemokines. Understanding the unique molecular features of the endometriotic tumor microenvironment may lead to impactful precision therapies and/or modalities for prevention. A challenge to this important study is the rarity of well-characterized clinical samples and the limited model systems. In this review, we will describe the unique molecular features of endometriosis-associated ovarian cancers, the endometriotic tumor microenvironment, and available model systems for endometriosis-associated ovarian cancers. Continued research on these unique ovarian cancers may lead to improved prevention and treatment options.

Rodent Models of Experimental Endometriosis: Identifying Mechanisms of Disease and Therapeutic Targets

BACKGROUND

Although it has been more than a century since endometriosis was initially described in the literature, understanding the etiology and natural history of the disease has been challenging. However, the broad utility of murine and rat models of experimental endometriosis has enabled the elucidation of a number of potentially targetable processes which may otherwise promote this disease.

OBJECTIVE

To review a variety of studies utilizing rodent models of endometriosis to illustrate their utility in examining mechanisms associated with development and progression of this disease.

RESULTS

Use of rodent models of endometriosis has provided a much broader understanding of the risk factors for the initial development of endometriosis, the cellular pathology of the disease and the identification of potential therapeutic targets.

CONCLUSION

Although there are limitations with any animal model, the variety of experimental endometriosis models that have been developed has enabled investigation into numerous aspects of this disease. Thanks to these models, our under-standing of the early processes of disease development, the role of steroid responsiveness, inflammatory processes and the peritoneal environment has been advanced. More recent models have begun to shed light on how epigenetic alterations con-tribute to the molecular basis of this disease as well as the multiple comorbidities which plague many patients. Continued de-velopments of animal models which aid in unraveling the mechanisms of endometriosis development provide the best oppor-tunity to identify therapeutic strategies to prevent or regress this enigmatic disease.

Animal models of endometriosis: Replicating the aetiology and symptoms of the human disorder

Endometriosis is a chronic incurable disorder that affects 1 in 10 women of reproductive age: associated symptoms include chronic pain and infertility. The aetiology of endometriosis remains poorly understood but patients, clinicians and researchers are all in agreement that new non-surgical therapies are urgently needed to reduce the severity of symptoms. Preclinical testing of drugs requires the development and validation of models that recapitulate the key features of the disorder. In this review we describe the best-validated animal models (primate, rodent, xenograft) and their contributions to our understanding of the factors underpinning the development of symptoms. We consider the evidence that these models have provided the platform for identification of new therapeutic interventions and reflect on future directions for research and drug validation.

Vasoactive intestinal peptide is upregulated in women with endometriosis and chronic pelvic pain

PROBLEM

Chronic pelvic pain (CPP) causes compromised the quality of life in women with endometriosis and is often attributed to local inflammation and ingrowth of nerve fibers. In this pilot study, we aimed to investigate whether the inflammation-related vasoactive intestinal peptide (VIP) and interleukin (IL)-6 were increased in affected patients.

METHOD OF STUDY

Endometrial and endometriotic tissue biopsy specimens, and serum and peritoneal fluid (PF) samples, were obtained from 85 endometriosis patients and 53 controls. VIP and IL-6 analysis and measurement of microvessel density in tissue were performed using immunohistochemistry, Western blotting, RT-qPCR, and ELISA.

RESULTS

Compared with controls, VIP transcript and protein levels were increased in endometrium from endometriosis patients and further elevated in patients with CPP. In addition, microvessel density, a measurement of angiogenic activity, was increased in the endometrium and in endometriosis lesions in the same subset of patients. Serum and PF levels of VIP and IL-6 were higher in women with endometriosis and CPP compared with endometriosis patients who reported no chronic pain.

CONCLUSION

Vasoactive intestinal peptide is upregulated in endometriosis patients reporting chronic pain. Increased microvessel density in tissue and peritoneal fluid concentrations of IL-6 indicate an elevated inflammation in the pelvic microenvironment of these patients.

Macrophage Migration Inhibitory Factor Receptor, CD74, is Overexpressed in Human and Baboon ( Papio Anubis) Endometriotic Lesions and Modulates Endometriotic Epithelial Cell Survival and Interleukin 8 Expression

CD74 is the primary receptor for macrophage migration inhibitory factor (MIF). Although expression of MIF has been described in endometriotic lesions, the cellular localization and function of the MIF receptor, CD74, are poorly understood. To further explore the role of CD74 in the pathophysiology of endometriosis, we utilized specimens from women with diagnostically confirmed endometriosis, women with no signs or symptoms of endometriosis (controls), and 8 baboons with experimentally induced endometriosis. Compared to eutopic endometrium from women with endometriosis, CD74 transcript expression was significantly increased in endometriotic lesion tissue. Similarly, cellular expression of CD74 was significantly greater in ectopic lesion tissue compared to paired eutopic endometrium, which both expressed greater CD74 expression compared to eutopic endometrium from control patients. Localization of CD74 was predominant to epithelial cells of ectopic and matched eutopic endometrium and was not influenced by the stage of the menstrual cycle. Eutopic endometrium from control patients did not express detectable levels of CD74 protein by immunohistochemistry. This pattern of expression and CD74 protein localization could be recapitulated in endometriotic lesion tissue from baboons with experimentally induced disease. Transfection of the endometriotic epithelial cell lines, 12Z with CD74 short hairpin RNA (shRNA), resulted in a significant decrease in CD74 protein expression, which was associated with a significant reduction in cellular proliferation as well as the expression of the prosurvival cytokine interleukin 8. Together, these data support the hypothesis that CD74 is elevated in endometriotic lesion tissue and may contribute to the pathogenesis of endometriosis by promoting cell survival.