Treatment with anti-TNF monoclonal antibody (c5N) reduces the extent of induced endometriosis in the baboon

The Known, the Unknown and the Future of the Pathophysiology of Endometriosis

Endometriosis is one of the most common causes of chronic pelvic pain and infertility, affecting 10% of women of reproductive age. A delay of up to 9 years is estimated between the onset of symptoms and the diagnosis of endometriosis. Endometriosis is currently defined as the presence of endometrial epithelial and stromal cells at ectopic sites; however, advances in research on endometriosis have some authors believing that endometriosis should be re-defined as "a fibrotic condition in which endometrial stroma and epithelium can be identified". There are several theories on the etiology of the disease, but the origin of endometriosis remains unclear. This review addresses the role of microRNAs (miRNAs), which are naturally occurring post-transcriptional regulatory molecules, in endometriotic lesion development, the inflammatory environment within the peritoneal cavity, including the role that cytokines play during the development of the disease, and how animal models have helped in our understanding of the pathology of this enigmatic disease.

Association of endometriosis with Sjögren's syndrome: Genetic insights (Review)

Patients with a history of endometriosis have an increased risk of developing various autoimmune diseases such as rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, multiple sclerosis and celiac disease. There is a potential association between endometriosis and an increased susceptibility for Sjögren's syndrome (SS). SS is a common chronic, inflammatory, systemic, autoimmune, multifactorial disease of complex pathology, with genetic, epigenetic and environmental factors contributing to the development of this condition. It occurs in 0.5‑1% of the population, is characterized by the presence of ocular dryness, lymphocytic infiltrations and contributes to neurological, gastrointestinal, vascular and dermatological manifestations. Endometriosis is an inflammatory, estrogen‑dependent, multifactorial, heterogeneous gynecological disease, affecting ≤10% of reproductive‑age women. It is characterized by the occurrence of endometrial tissue outside the uterine cavity, mainly in the pelvic cavity, and is associated with pelvic pain, dysmenorrhea, deep dyspareunia and either subfertility or infertility. It is still unclear whether SS appears as a secondary response to endometriosis, or it is developed due to any potential shared mechanisms of these conditions. The aim of the present review was to explore further the biological basis only of the co‑occurrence of these disorders but not their association at clinical basis, focusing on the analysis of the partially shared genetic background between endometriosis and SS, and the clarification of the possible similarities in the underlying pathogenetic mechanisms and the relevant molecular pathways.

Menstrual cycle abnormalities in women with inflammatory bowel disease and effects of biological therapy on gynecological pathology

Inflammatory bowel disease (IBD) is a chronic condition that affects young individuals in their reproductive years. It may have long-term implications on their reproductive, sexual, and mental health. IBD has been related to menstrual abnormalities. Furthermore, the administration of biological therapy can also result in gynecological issues in addition to the disease itself. The purpose of this review was to present potential menstrual cycle problems in patients with IBD, as well as the impact of adalimumab and other anti-tumor necrosis factor medications on gynecological pathology.

The latest advances in the pharmacological management of endometriosis

INTRODUCTION

Endometriosis is a benign disease, characterized by a wide range of symptoms and different degrees of severity, which is why therapy should be individually adapted to the patient's needs. Over the years, a lot of research has gone into finding new therapeutic approaches for this enigmatic disease.

AREAS COVERED

This review presents the latest advances in pharmacological management of endometriosis and is solely focused on studies published from 2010 to 2021.

EXPERT OPINION

Clinicians and researchers are constantly searching for new therapeutic strategies for endometriosis patients. As there are well-established treatments, however, any new medication should fulfill at least one of the three criteria: increased efficacy, comparable efficacy but a better safety profile, or treatments that have a lack of accompanying contraceptive effects that are seen in most endometriosis treatments. While some new substances show promising results, further studies are needed to demonstrate the fulfillment of one of the above-mentioned criteria.

Sex Steroid Receptors in Polycystic Ovary Syndrome and Endometriosis: Insights from Laboratory Studies to Clinical Trials

Polycystic ovary syndrome (PCOS) and endometriosis are reproductive disorders that may cause infertility. The pathology of both diseases has been suggested to be associated with sex steroid hormone receptors, including oestrogen receptors (ER), progesterone receptors (PRs) and androgen receptors (ARs). Therefore, with this review, we aim to provide an update on the available knowledge of these receptors and how their interactions contribute to the pathogenesis of PCOS and endometriosis. One of the main PCOS-related medical conditions is abnormal folliculogenesis, which is associated with the downregulation of ER and AR expression in the ovaries. In addition, metabolic disorders in PCOS are caused by dysregulation of sex steroid hormone receptor expression. Furthermore, endometriosis is related to the upregulation of ER and the downregulation of PR expression. These receptors may serve as therapeutic targets for the treatment of PCOS-related disorders and endometriosis, considering their pathophysiological roles. Receptor agonists may be applied to increase the expression of a specific receptor and treat endometriosis or metabolic disorders. In contrast, receptor antagonist functions to reduce receptor expression and can be used to treat endometriosis and induce ovulation. Understanding PCOS and the pathological roles of endometriosis sex steroid receptors is crucial for developing potential therapeutic strategies to treat infertility in both conditions. Therefore, research should be continued to fill the knowledge gap regarding the subject.

Bacillus Calmette-Guerin (BCG) vaccination to treat endometriosis

Bacille Calmette-Guérin (BCG), a vaccine intended to protect against tuberculosis disease, can elicit protection against heterologous infections, and even specific types of cancer. In this mini-review, we will address the possible use of BCG as a therapeutic for endometriosis, a syndrome of chronic pelvic pain due to ectopic growth of endometrial-type tissue outside of the uterine lining. These implanted tissues cycle synchronously with menses in pre-menopausal women, generating cellular debris inciting chronic inflammation and tissue scarring leading to pelvic pain and infertility. Further, these lesions may evolve into ovarian clear cell carcinoma. We hypothesize that implantation, survival and transformation of these implants is enabled by a form of immune suppression within the peritoneum, which may be overcome by BCG vaccination.

Interleukin-37b inhibits the growth of murine endometriosis-like lesions by regulating proliferation, invasion, angiogenesis and inflammation

Endometriosis is a gynecological disease with abnormal expression of interleukin (IL)-37 which can suppress inflammation and the immune system. Here we investigated the role of the IL-37b splice variant in endometriosis in vivo and in vitro. In a murine model of endometriosis, in vivo administration of IL-37b significantly inhibited the development of lesions judged by the number (P = 0.0213), size (P = 0.0130) and weight (P = 0.0152) of lesions. IL-37b had no effect on the early stage of lesion formation, however administration in the growth stage of lesions decreased the number (P = 0.0158), size (P = 0.0158) and weight (P = 0.0258) of lesions compared with PBS control, an effect that was not reversed by macrophage depletion. Expressions of inflammatory factors, matrix metalloproteinases and vascular endothelial growth factor-A mRNA/protein were significantly inhibited in ectopic lesions following IL-37b administration, and in uterine segments treated in vitro. In vitro treatment of uterine segments with IL-37b inhibited phosphorylation of Akt and Erk1/2 in uterine segments. Isolated mouse endometrial stromal treated with IL-37b and transfected with pIL-37b plasmid got suppressed cell proliferation, invasion, angiogenesis and the expression of inflammatory factors. In addition, transfection with pIL-37b significantly decreased the phosphorylation of Akt and Erk1/2. IL-37b also inhibited proliferation and the expression of inflammatory and angiogenesis factors in epithelial cell line RL95-2. These findings suggest that IL-37b may inhibit the growth of lesions by regulating proliferation, invasion, angiogenesis and inflammation through Akt and Erk1/2 signaling pathway.

Role of medical treatment of endometriosis

Endometriosis is a chronic benign disease that affects women of reproductive age. Medical therapy is often the first line of management for women with endometriosis in order to ameliorate symptoms or to prevent post-surgical disease recurrence. Currently, there are several medical options for the management of patients with endometriosis and long-term treatments should balance clinical efficacy (controlling pain symptoms and preventing recurrence of disease after surgery) with an acceptable safety-profile. Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of chronic inflammatory conditions, being efficacious in relieving primary dysmenorrhea. Combined oral contraceptives and progestins, available for multiple routes of administration, are commonly administered as first-line hormonal therapies. Several studies demonstrated that they succeed in improving pain symptoms in the majority of patients; moreover, they are well tolerated and not expensive. Gonadotropin-releasing hormone-agonists are prescribed when first line therapies are ineffective, not tolerated or contraindicated. Even if these drugs are efficacious in treating women not responding to COCs or progestins, they are not orally available and have a less favorable tolerability profile (needing an appropriate add-back therapy). Because few data are available on long-term efficacy and safety of aromatase inhibitors they should be reserved only for women with symptoms who are refractory to other treatments only in a research environment. Almost all of the currently available treatment options for endometriosis suppress ovarian function and are not curative. For this reason, research into new drugs is unsurprisingly demanding. Amongst the drugs currently under investigation, gonadotropin-releasing hormone antagonists have shown most promise, currently in late-stage clinical development. There is a number of potential future therapies currently tested only in vitro, in animal models of endometriosis or in early clinical studies with a small sample size. Further studies are necessary to conclude whether these treatments would be of value for the treatment of endometriosis.

Endometriosis with infertility: A comprehensive review on the role of immune deregulation and immunomodulation therapy

BACKGROUND

Endometriosis is a multifactorial pathology dependent on intrinsic and extrinsic factors, but the immune deregulation seems to play a pivotal role. In endometriosis-associated infertility, this could raise the benefit of immunomodulatory strategies to improve the results of ART. In this review, we will describe (1) sera and peritoneal fluid cytokines and immune markers; (2) autoantibodies; and (3) immunomodulatory treatments in endometriosis with infertility.

METHODS

The literature research was conducted in MEDLINE, Embase, and Cochrane Library with the following keywords: "endometriosis", "unexplained miscarriage", "implantation failure", "recurrent implantation failure » and « IVF-ICSI », « biomarkers of autoimmunity", "TNF-α", "TNF-α antagonists", "infliximab", "adalimumab", "etanercept", "immunomodulatory treatment", "steroids", "intralipids", "intravenous immunoglobulins", "G-CSF", "pentoxyfylline".

RESULTS

Several studies analyzed the levels of pro-inflammatory cytokines in sera and peritoneal fluid of endometriosis-associated infertility, in particular TNF-α. Various autoantibodies have been found in peritoneal fluid and sera of infertile endometriosis women even in the absence of clinically defined autoimmune disease, as antinuclear, anti-SSA, and antiphospholipid autoantibodies. In few uncontrolled studies, steroids and TNF-α antagonists could increase the pregnancy rates in endometriosis-associated infertility, but well-designed trials are lacking.

CONCLUSION

Endometriosis is characterized by increased levels of cytokines and autoantibodies. This suggests the role of inflammation and immune cell deregulation in infertility associated with endometriosis. The strategies of immunomodulation to regulate these immune deregulations are poorly studied, and well-designed studies are necessary.

Anti-IL-6 receptor monoclonal antibody as a new treatment of endometriosis

Many pro-inflammatory cytokines especially tumor necrotic factor alpha (TNFα), interleukin (IL)-1β, and IL-6 have crucial role in the pathogenesis of endometriosis. In this study, we investigated the immune-modulatory role of humanized anti-IL-6 receptor monoclonal antibodies in the treatment of endometriosis. This is a prospective, randomized, controlled, blinded study in which Sprague Dawley rats were used as animal model of endometriosis. Animals were randomly divided into two groups, a test group which received tocilizumab (Actemra; Roche, Switzerland) and a control group which received saline. Afterwards, a comparison was done between the eutopic and ectopic endometrium that was excised from both groups, histopathologically and immune-histochemically. Histopathologic assessment and immune-histochemical staining were performed using antibodies against IL-6. Tocilizumab significantly suppressed the volume of endometriotic lesions compared with non-treated rats (P = 0.006) and atrophied the ectopic endometrial-like epithelium (in 42.8% of treated rats vs 0% in the control group). Tocilizumab also decreased the anti-IL-6 receptor immune-histochemical staining intensity in ectopic endometrium (from non to +++ in the test group vs ++ or more in the control group), with no apparent difference in the eutopic one reflecting the down-regulation of IL-6-producing cells in ectopic endometriotic lesions. In rats with induced endometriosis, anti-IL-6 receptor monoclonal antibodies could offer a new horizon of usage of this immune-modulatory biologic drug, used in other autoimmune diseases, in treatment of endometriosis.

Menstrual Effluent Provides a Novel Diagnostic Window on the Pathogenesis of Endometriosis

Endometriosis is a chronic inflammatory disorder characterized by the presence of endometrial-like tissue growing outside of the uterus. Although the cause is unknown, retrograde menstruation leads to deposition of endometrial cells into the peritoneal cavity. Lack of disease recognition and long diagnostic delays (6–10 years) lead to substantial personal, social and financial burdens, as well as delayed treatment. A non-invasive diagnostic for endometriosis is a major unmet clinical need. Here, we assessed whether differences in menstrual effluent-derived stromal fibroblast cells (ME-SFCs) from women with and without endometriosis provide the basis for a non-invasive diagnostic for endometriosis. In addition, we investigated whether treatment of control ME-SFCs with inflammatory cytokines (TNF and IL-1β) could induce an endometriosis-like phenotype. ME-SFCs from laparoscopically diagnosed endometriosis patients exhibit reduced decidualization capacity, measured by IGFBP1 production after exposure to cAMP. A receiver operating characteristic (ROC) curve developed using decidualization data from controls and endometriosis subjects yielded an area under the curve of 0.92. In addition, a significant reduction in ALDH1A1 gene expression and increased podoplanin surface expression were also observed in endometriosis ME-SFCs when compared to control ME-SFCs. These endometriosis-like phenotypes can be reproduced in control ME-SFCs by exposure to inflammatory cytokines (TNF and IL-1β) and are associated with increased cell migration. These results are consistent with the hypothesis that chronic intrauterine inflammation influences the development of endometriosis lesions following retrograde menstruation. In conclusion, the analysis of ME-SFCs can provide an accurate, rapid, and non-invasive diagnostic for endometriosis and insight into disease pathogenesis.

Estrogen Receptors and Endometriosis

Endometriosis is a frequent and chronic inflammatory disease with impacts on reproduction, health and quality of life. This disorder is highly estrogen-dependent and the purpose of hormonal treatments is to decrease the endogenous ovarian production of estrogens. High estrogen production is a consistently observed endocrine feature of endometriosis. mRNA and protein levels of estrogen receptors (ER) are different between a normal healthy endometrium and ectopic/eutopic endometrial lesions: endometriotic stromal cells express extraordinarily higher ERβ and significantly lower ERα levels compared with endometrial stromal cells. Aberrant epigenetic regulation such as DNA methylation in endometriotic cells is associated with the pathogenesis and development of endometriosis. Although there is a large body of data regarding ERs in endometriosis, our understanding of the roles of ERα and ERβ in the pathogenesis of endometriosis remains incomplete. The goal of this review is to provide an overview of the links between endometriosis, ERs and the recent advances of treatment strategies based on ERs modulation. We will also attempt to summarize the current understanding of the molecular and cellular mechanisms of action of ERs and how this could pave the way to new therapeutic strategies.

Endometriosis Classification and The Role of Tumor Necrosis Factor-Alpha Polymorphisms as A Therapeutic Target

In the recent original research published on International Journal of Fertility and Sterility the association between tumor necrosis factor-alpha (TNF-α) genetic polymorphisms and endometriosis in 150 Iranian patients suffered this disease. The authors notably found a lower frequency of TNF-α -863C/A allele A among the affected patients in comparison with healthy women, although this difference was not significant by adjusting multiple testing. We deem that the authors should specify, if these patients had peritoneal nodules, ovarian endometrioma/deep infiltrating endometriosis (DIE) nodules or combination of them, since it has been hypothesized that these phenotypes may represent three distinct pathogenetic entities of endometriosis.

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.

Anti-inflammatory cytokines in endometriosis

Although the pathogenesis of endometriosis is not fully understood, it is often considered to be an inflammatory disease. An increasing number of studies suggest that differential expression of anti-inflammatory cytokines (e.g., interleukin-4 and -10, and transforming growth factor-β1) occurs in women with endometriosis, including in serum, peritoneal fluid and ectopic lesions. These anti-inflammatory cytokines also have indispensable roles in the progression of endometriosis, including by promoting survival, growth, invasion, differentiation, angiogenesis, and immune escape of the endometriotic lesions. In this review, we provide an overview of the expression, origin, function and regulation of anti-inflammatory cytokines in endometriosis, with brief discussion and perspectives on their future clinical implications in the diagnosis and therapy of the disease.

TGR5 agonist INT-777 mitigates inflammatory response in human endometriotic stromal cells: A therapeutic implication for endometriosis

Endometriosis is a condition characterized by the presence of endometrial tissues outside the uterus. Endometriotic stromal cells (ESCs) are known to undergo regeneration and are linked to the causation of endometriosis. Activation of stromal cells by local inflammatory cytokines is proposed to be one of the mechanisms of endometriosis development. Takeda-G-protein-receptor-5 (TGR5) is a G protein-coupled bile acid receptor that plays multiple roles in various cells and tissues. In this study, we show that activation of TGR5 by its specific agonist, INT-777, protects ESCs from inflammation and oxidative stress induced by tumor necrosis factor-α (TNF-α). TGR5 is fairly expressed in cultured ESCs, and TNF-α treatment suppresses TGR5 expression. Activation of TGR5 by its synthetic agonist, INT-777, dramatically reduces the production of pro-inflammatory cytokines and adhesion molecules by TNF-α, including interleukin-6 (IL-6), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Moreover, INT-777 suppresses TNF-α-induced NADPH oxidase 4 (NOX4) expression and ameliorates cellular oxidative stress. Mechanistically, our findings demonstrate that INT-777 suppresses TNF-α-induced c-Jun N-terminal kinase (JNK) activation via suppression of p-JNK. INT-777 inhibits TNF-α-induced activation of the activator protein-1 (AP-1) pathway owing to its suppression of c-Jun and c-fos as well as transfected AP-1 promoter. INT-777 also inhibits nuclear factor-κB (NF-κB) activation as revealed by its suppression of TNF-α-induced nuclear p65 accumulation and NF-κB promoter. Collectively, our data indicate that activation of TGR5 by its agonist has protective effects against inflammation and reactive oxygen species (ROS) in cytokine-induced activation of ESCs. Therefore, INT-777 may have an implication in the clinical treatment of endometriosis.

6-Shogaol reduces progression of experimental endometriosis in vivo and in vitro via regulation of VGEF and inhibition of COX-2 and PGE2-mediated inflammatory responses

Endometriosis (EM) is one of the most common gynaecological disorder affecting women in their reproductive age. Mechanisms involved in the pathogenesis of EM remains poorly understood, however inflammatory responses have been reported to be significantly involved. The efficacy of 6-shogaol on proliferation of endometriotic lesions and inflammatory pathways in experimentally-induced EM model was explored in this study. EM was stimulated in Sprague-Dawley rats by implantation of autologous endometrium onto the peritoneum abdominal wall. Separate groups were treated with 6-shogaol (50, 100 or 150 mg/kg b.wt/day) via oral gavage for one month period. Gestrinone (GTN) group received GTN (0.5 mg/kg/day) as positive control. Five weeks after implantation, the spherical volume of ecto-uterine tissues was determined. Treatment with 6-shogaol significantly reduced the implant size. Histological analysis reported atrophy and regression of the lesions. 6-shogaol administration effectively down-regulated NF-κB signaling, VEGF and VEGFR-2 (Flk-1) expression in the endometriotic lesions. Excess production of IL-1β and IL-6 (pro-inflammatory cytokines), PGE2 and nitric oxide (NO) were reduced. Overall, the results of the study reveal the efficacy of 6-shogaol against endometriosis via effectively suppressing proliferation of the lesions and modulating angiogenesis and COX-2/NF-κB-mediated inflammatory cascades.

Nobiletin alleviates endometriosis via down-regulating NF-κB activity in endometriosis mouse model

Nobiletin exhibits protective potential on inflammation and inhibits the activation of transcription factors nuclear factor-κB (NF-κB). However, its effects on the progression of endometriosis remain unsettled. The present study aimed to explore the in vivo alleviation of nobiletin on endometriosis and its mechanism of action. The mouse model of endometriosis was established and administered with nobiletin. The ectopic lesion size was measured and the hotplate test was performed to assess the amelioration of nobiletin on endometriosis. The expression of proliferation and angiogenesis relevant genes including proliferating cell nuclear antigen (PCNA), vascular endothelial growth factor (VEGF), and E-cadherin was measured by immunostaining and the mRNA expression of proinflammatory mediators including interleukin (IL)-6, IL-1β, tumor necrosis factor (TNF)-α, matrix metalloproteinases (MMP)-1, and MMP-3 was measured by RT-PCR. The change of NF-κB activity in endometriotic cells was evaluated by Western blotting and confirmed by luciferase assay. Administration of nobiletin significantly reduced lesions size and pain in endometriosis mice. Nobiletin significantly altered the expression of PCNA, VEGF, and E-cadherin in ectopic endometrium, as well as the levels of IL-6, IL-1β, TNF-α, MMP-1, and MMP-3. Nobiletin also showed remarkably impairment on the activation of NF-κB in promoting endometriotic cells, likely targeting on the activity of IκB kinases (IKKs). The present study provides the first evidence that nobiletin exerts protection on endometriosis via inhibition the activation of NF-κB, specifically on the activity of IκB kinases.

Investigational drugs for the treatment of endometriosis, an update on recent developments

INTRODUCTION

Endometriosis is a hormone-dependent benign chronic disease that requires a chronic medical therapy. Although currently available drugs are efficacious in treating endometriosis-related pain, some women experience partial or no improvement. Moreover, the recurrence of symptoms is expected after discontinuation of the therapies. Currently, new drugs are under intense clinical investigation for the treatment of endometriosis.

AREAS COVERED

This review aims to offer the reader a complete and updated overview on new investigational drugs and early molecular targets for the treatment of endometriosis. The authors describe the pre-clinical and clinical development of these agents.

EXPERT OPINION

Among the drugs under investigation, late clinical trials on gonadotropin-releasing hormone antagonists (GnRH-ant) showed the most promising results for the treatment of endometriosis. Aromatase inhibitors (AIs) are efficacious in treating endometriosis related pain symptoms but they cause significant adverse effects that limit their long-term use. New targets have been identified to produce drugs for the treatment of endometriosis, but the majority of these new compounds have only been investigated in laboratory studies or early clinical trials. Thus, further clinical research is required in order to elucidate their efficacy and safety in human.

Nonhuman Primates: A Vital Model for Basic and Applied Research on Female Reproduction, Prenatal Development, and Women's Health

The comparative biology of reproduction and development in mammalian species is remarkable. Hence, because of similarities in environmental and neuroendocrine control of the reproductive axis, the cyclic function of the ovary and reproductive tract, establishment and control of the maternal-fetal-placental unit during pregnancy, and reproductive aging from puberty through menopause, nonhuman primates (NHPs) are valuable models for research related to women's reproductive health and its disorders. This chapter provides examples of research over the past 10+ years using Old World monkeys (notably macaque species), baboons, and to a lesser extent New World monkeys (especially marmosets) that contributed to our understanding of the etiology and therapies or prevention of: (1) ovarian disorders, e.g., polycystic ovary syndrome, mitochondrial DNA-based diseases from the oocyte; (2) uterine disorders, for example, endometriosis and uterine transplantation; and (3) pregnancy disorders, for example, preterm labor and delivery, environmental factors. Also, emerging opportunities such as viral (e.g., Zika) induced fetal defects and germline genomic editing to generate valuable primate models of human diseases (e.g., Huntington and muscular dystrophy) are addressed. Although the high costs, specialized resources, and ethical debate challenge the use of primates in biomedical research, their inclusion in fertility and infertility research is vital for continued improvements in women's reproductive health.

Effect of Etanercept on the Success of Assisted Reproductive Technology in Patients with Endometrioma

AIMS

To determine the effects of a tumor necrosis factor inhibitor (etanercept) on pregnancy outcomes in patients with endometrioma who were treated with assisted reproductive technology.

METHODS

Sixty-eight infertile patients who had endometrioma were included in our retrospective case-control study. We administered etanercept (Enbrel, 50 mg in 1 mL intramuscularly) to 19 patients on the second day of their previous menstrual cycle. All patients were treated with assisted reproductive technology. Pregnancy and live birth rates (LBR) were documented.

RESULTS

When all other parameters (age, body mass index, infertility) are supposed to be constant, the clinical pregnancy rate was significantly higher in patients who used etanercept in an antagonist protocol than in patients who did not use etanercept (χ2 = 5.547; p = 0.019) but LBR did not reach a statistical significance (χ2 = 3.179; p = 0.075). The use of etanercept had an OR of 4.17 (95% CI 1.23-14.14) compared with not using etanercept for clinical pregnancy rate. The use of etanercept increased the rate of pregnancy (χ2 = 6.55; p = 0.01). The pregnancy rate with the use of etanercept had an OR of 4.23 (95% CI 1.35-13.25) compared with patients who did not use etanercept. In the same way, the use of etanercept increased LBR twofold, but it is not significant in the border line (χ2 = 3.771; p = 0.052).

CONCLUSIONS

Etanercept may be a new non-hormonal therapy that may be an adjunct to treatment of infertile women with endometrioma. However, the safety of etanercept on embryos and fetuses has not been fully clarified.

Recent advances in the understanding of endometriosis: the role of inflammatory mediators in disease pathogenesis and treatment

In this review, we focus on recent advancements in our understanding of the roles of inflammatory mediators in endometriosis pathophysiology and the potential for improved therapies based upon targeting these pathways. We review the association between endometriosis and inflammation and the initial promise of anti-tumor necrosis factor therapies based upon experimental evidence, and how and why these studies have not translated to the clinic. We then discuss emerging data on the role of inter-relationship among macrophage migration inhibitory factor, prostaglandin E ₂, and estrogen receptor-beta, and the potential utility of targeting these factors in endometriosis treatment. In doing so, we highlight the strengths and discuss the current research on identification of novel, anti-inflammatory-based therapy and the necessity to expand experimental endpoints to include clinically relevant measures when assessing the efficacy of potential new therapies for endometriosis.

Challenges in the development of novel therapeutic strategies for treatment of endometriosis

INTRODUCTION

Endometriosis is an estrogen-dependent disease that results in pelvic pain and infertility. Its treatment is often frustrating due to limited medical treatment options, complex surgical treatment and high recurrence rates. Despite the advances in our understanding of the pathogenesis over the last decades and the consequent novel therapeutic strategies, no new drugs have been introduced in daily clinical practice.

AREAS COVERED

In the first part we present an overview of the pathogenesis of endometriosis. In the second part we discuss how new insights have led to the development of novel nonhormonal strategies for the treatment of endometriosis, focusing on anti-inflammatory and anti-angiogenic agents. In the third part we describe the problems encountered in the translation from experimental drugs to routine medicine for the treatment of endometriosis.

EXPERT OPINION

Despite the multitude of agents that have been tested in preclinical trials, only few drugs have passed to the stage of clinical testing and none have been introduced into clinical practice. It is our opinion that the major challenges in the translation from novel agents for endometriosis is due to the use of inadequate rodent models and a lack of standardization in the design and reporting of preclinical endometriosis models.

c-Jun NH2-terminal kinase inhibitor bentamapimod reduces induced endometriosis in baboons: an assessor-blind placebo-controlled randomized study

OBJECTIVE

To test the hypothesis that the c-Jun NH2-terminal kinase (JNK) inhibitor (JNKI) bentamapimod (AS602801/PGL5001) can reduce induced endometriosis in baboons.

DESIGN

Prospective randomized placebo-controlled study.

SETTING

Nonhuman primate research center.

ANIMAL(S)

Twenty baboons each underwent four laparoscopies. Initial screening laparoscopy (L1) was followed after one rest cycle by an endometriosis-induction laparoscopy (L2). Fifty days after L2, the baboons were randomized just before staging laparoscopy (L3). Treatment lasted for 60 days, followed by a post-treatment staging laparoscopy (L4).

INTERVENTION(S)

Randomization before a 60-day treatment in four groups: daily placebo (n = 5), daily oral administration of 20 mg/kg JNKI (n = 5), concomitant daily oral administration of 20 mg/kg JNKI and 10 mg medroxyprogesterone acetate (MPA; n = 5), or subcutaneous administration of 3 mg cetrorelix every 3 days (n = 5).

MAIN OUTCOME MEASURE(S)

Type, surface area and volume of endometriotic lesions, and revised American Society for Reproductive Medicine score and stage were recorded during L3 and L4. Menstrual cycle length and serum hormonal concentration were recorded before and after treatment.

RESULT(S)

Compared with placebo, treatment with JNKI, JNKI + PMA, or cetrorelix resulted in lower total surface area and volume of endometriotic lesions. Remodeling of red active lesions into white lesions was observed more frequently in baboons treated with JNKI + MPA than in baboons treated with JNKI only. Menstrual cycle length and serum hormonal concentration were similar between placebo and JNKI groups.

CONCLUSION(S)

JNKI alone was as effective as JNKI + MPA or cetrorelix in reducing induced endometriosis in baboons, but without severe side effects or effect on cycle length or serum reproductive hormones.

Bentamapimod (JNK Inhibitor AS602801) Induces Regression of Endometriotic Lesions in Animal Models

Endometriosis is an estrogen (ER)-dependent gynecological disease caused by the growth of endometrial tissue at extrauterine sites. Current endocrine therapies address the estrogenic aspect of disease and offer some relief from pain but are associated with significant side effects. Immune dysfunction is also widely believed to be an underlying contributor to the pathogenesis of this disease. This study evaluated an inhibitor of c-Jun N-terminal kinase, bentamapimod (AS602801), which interrupts immune pathways, in 2 rodent endometriosis models. Treatment of nude mice bearing xenografts biopsied from women with endometriosis (BWE) with 30 mg/kg AS602801 caused 29% regression of lesion. Medroxyprogesterone acetate (MPA) or progesterone (PR) alone did not cause regression of BWE lesions, but combining 10 mg/kg AS602801 with MPA caused 38% lesion regression. In human endometrial organ cultures (from healthy women), treatment with AS602801 or MPA reduced matrix metalloproteinase-3 (MMP-3) release into culture medium. In organ cultures established with BWE, PR or MPA failed to inhibit MMP-3 secretion, whereas AS602801 alone or MPA + AS602801 suppressed MMP-3 production. In an autologous rat endometriosis model, AS602801 caused 48% regression of lesions compared to GnRH antagonist Antide (84%). AS602801 reduced inflammatory cytokines in endometriotic lesions, while levels of cytokines in ipsilateral horns were unaffected. Furthermore, AS602801 enhanced natural killer cell activity, without apparent negative effects on uterus. These results indicate that bentamapimod induced regression of endometriotic lesions in endometriosis rodent animal models without suppressing ER action. c-Jun N-terminal kinase inhibition mediated a comprehensive reduction in cytokine secretion and moreover was able to overcome PR resistance.

Novel agents for the medical treatment of endometriosis

PURPOSE OF REVIEW

Current medical treatments for endometriosis-associated pain, including oral contraceptives, progestins and GnRH agonists, are partially effective and have significant side-effects. The purpose of this review is to present new hormonal and nonhormonal treatment for endometriosis.

RECENT FINDINGS

At present, the ideal drug that can prevent, inhibit or stop development of endometriosis, reduce associated pain or infertility and allow conception does not exist. New drugs in development for endometriosis modulate GnRH, estrogen and/or progesterone receptors, or target endometriosis-associated inflammation, angiogenesis, adhesion and/or tissue invasion. Most have been tested in rodents, and have been evaluated in more relevant animal models like nonhuman primates (baboons), but only a few, that is GnRH antagonists, have been tested in human randomized controlled trials. Important safety and efficacy issues remain a concern, as steroid receptors, inflammation, adhesion, angiogenesis and tissue invasion are key factors in physiological events like ovulation, menstruation and embryo implantation.

SUMMARY

New drugs for the medical treatment of endometriosis targeting both hormonal (GnRH, estrogen and progesterone receptors) and nonhormonal pathways (inflammation, angiogenesis, adhesions, tissue invasion) are promising, but their efficacy and safety need to be established in randomized human trials before they can be used in clinical practice.

Medical treatments for endometriosis-associated pelvic pain

The main sequelae of endometriosis are represented by infertility and chronic pelvic pain. Chronic pelvic pain causes disability and distress with a very high economic impact. In the last decades, an impressive amount of pharmacological agents have been tested for the treatment of endometriosis-associated pelvic pain. However, only a few of these have been introduced into clinical practice. Following the results of the controlled studies available, to date, the first-line treatment for endometriosis associated pain is still represented by oral contraceptives used continuously. Progestins represent an acceptable alternative. In women with rectovaginal lesions or colorectal endometriosis, norethisterone acetate at low dosage should be preferred. GnRH analogues may be used as second-line treatment, but significant side effects should be taken into account. Nonsteroidal anti-inflammatory drugs are widely used, but there is inconclusive evidence for their efficacy in relieving endometriosis-associated pelvic pain. Other agents such as GnRH antagonist, aromatase inhibitors, immunomodulators, selective progesterone receptor modulators, and histone deacetylase inhibitors seem to be very promising, but there is not enough evidence to support their introduction into routine clinical practice. Some other agents, such as peroxisome proliferator activated receptors-γ ligands, antiangiogenic agents, and melatonin have been proven to be efficacious in animal studies, but they have not yet been tested in clinical studies.

Increased nuclear expression of nuclear factor kappa-B p65 subunit in the eutopic endometrium and ovarian endometrioma of women with advanced stage endometriosis

PROBLEM

We evaluated whether the expression of NF-кB p65 subunit is increased in the eutopic endometrium and/or in the ovarian endometrioma of women with advanced stage endometriosis, and ascertained in vitro effects of proinflammatory cytokines on the expression and DNA binding of NF-кB p65 subunit in endometrial cells.

METHOD OF STUDY

Immunohistochemistry was performed to compare the nuclear NF-кB p65 subunit immunoreactivity between women with and without advanced stage endometriosis. The nuclear NF-кB p65 subunit expression and DNA binding were also analyzed in endometrial cells treated with tumor necrosis factor-alpha (TNF-α) or interleukin-1beta (IL-1β) utilizing Western blot analysis, enzyme-linked immunosorbent assay, and electrophoretic mobility shift assay.

RESULTS

The immunoreactivity of the nuclear NF-кB p65 subunit was significantly increased in the eutopic endometrium as well as in the ovarian endometrioma of women with endometriosis compared with the controls. In vitro treatment of endometrial cells with TNF-α and IL-1β led to a significant increase in nuclear NF-кB p65 subunit expression and DNA binding.

CONCLUSIONS

The nuclear expression of NF-κB p65 is increased in the eutopic endometrium and ovarian endometrioma of women with advanced stage endometriosis, which strongly suggests that NF-кB signaling plays a crucial role in the pathogenesis and/or pathophysiology of endometriosis.

Interplay between Misplaced Müllerian-Derived Stem Cells and Peritoneal Immune Dysregulation in the Pathogenesis of Endometriosis

In the genetic regulation of Müllerian structures development, a key role is played by Hoxa and Wnt clusters, because they lead the transcription of different genes according to the different phases of the organogenesis, addressing correctly cell-to-cell interactions, allowing, finally, the physiologic morphogenesis. Accumulating evidence is suggesting that dysregulation of Wnt and/or Hox genes may affect cell migration during organogenesis and differentiation of Müllerian structures of the female reproductive tract, with possible dislocation and dissemination of primordial endometrial stem cells in ectopic regions, which have high plasticity to differentiation. We hypothesize that during postpubertal age, under the influence of different stimuli, these misplaced and quiescent ectopic endometrial cells could acquire new phenotype, biological functions, and immunogenicity. So, these kinds of cells may differentiate, specializing in epithelium, glands, and stroma to form a functional ectopic endometrial tissue. This may provoke a breakdown in the peritoneal cavity homeostasis, with the consequent processes of immune alteration, documented by peripheral mononuclear cells recruitment and secretion of inflammatory cytokines in early phases and of angiogenic and fibrogenic cytokines in the late stages of the disease.

Baboon model for the study of endometriosis

Endometriosis is a benign, estrogen-dependent disease and is now recognized as an enigmatic disease owing to its various clinical manifestations and locations. The lack of a reliable and specific method for the early detection of endometriosis often results in delayed diagnosis. So far, research has born inadequate findings regarding understanding the basic etiology or pathophysiology of endometriosis. Animal models that accurately represent the cellular and molecular changes associated with the initiation and progression of human endometriosis have significant potential to facilitate the development of better methods for the early detection and treatment of endometriosis. A number of animal model systems have been developed for the study of this disease. These models replicate many of the known salient features of human endometriosis. This review provides an insight into the use of the baboon model for studies focused on understanding human endometriosis.

A new isoform of steroid receptor coactivator-1 is crucial for pathogenic progression of endometriosis

Endometriosis is considered to be an estrogen-dependent inflammatory disease, but its etiology is unclear. Thus far, a mechanistic role for steroid receptor coactivators (SRCs) in the progression of endometriosis has not been elucidated. An SRC-1-null mouse model reveals that the mouse SRC-1 gene has an essential role in endometriosis progression. Notably, a previously unidentified 70-kDa SRC-1 proteolytic isoform is highly elevated both in the endometriotic tissue of mice with surgically induced endometriosis and in endometriotic stromal cells biopsied from patients with endometriosis compared to normal endometrium. Tnf⁻/⁻ and Mmp9⁻/⁻ mice with surgically induced endometriosis showed that activation of tumor necrosis factor a (TNF-α)-induced matrix metallopeptidase 9 (MMP9) activity mediates formation of the 70-kDa SRC-1 C-terminal isoform in endometriotic mouse tissue. In contrast to full-length SRC-1, the endometriotic 70-kDa SRC-1 C-terminal fragment prevents TNF-α-mediated apoptosis in human endometrial epithelial cells and causes the epithelial-mesenchymal transition and the invasion of human endometrial cells that are hallmarks of progressive endometriosis. Collectively, the newly identified TNF-α-MMP9-SRC-1 isoform functional axis promotes pathogenic progression of endometriosis.

Primate model research for endometriosis

Endometriosis is defined as the existence of endometrial tissue outside the uterine cavity, and it includes a chronic, inflammatory reaction associated with female infertility and pelvic pain. Endometriosis occurs in 7 to 10% of women. Although it has been studied for more than 50 years, the pathogenesis and development of endometriosis are still poorly understood. There is no curative therapy for endometriosis, which often recurs after surgical or medical treatment. There is a consensus that the adverse current of menstrual blood plays a crucial role in the development of endometriosis. This places a major limitation on research using rodent models of endometriosis, although these are still widely employed, because rodents do not menstruate and endometriosis does not occur spontaneously in these animals. In fact, menstruation and spontaneous endometriosis only occur in women and some non-human primates, making models that employ non-human primates the best animal models for research into the pathogenesis, pathophysiology, spontaneous onset, and treatment of endometriosis. This review assesses the effectiveness and potential of the non-human primate models of endometriosis. It also describes the current findings and theories on the pathogenesis of endometriosis that have been obtained by research using non-human primates.

New treatment strategies and emerging drugs in endometriosis

Introduction: Endometriosis, histologically defined as the presence of endometrium-like tissue - glands and stroma - that develops outside of the uterine cavity, is still an enigmatic disease responsible for pelvic pain and infertility. The current treatments of endometriosis are surgery and hormonal therapies that act by suppressing ovulation and/or directly on steroid receptors located in endometriotic lesions. Areas covered: New hormonal and non-hormonal therapies are being developed for the treatment of endometriosis-related pain. The authors review the state of advancement and the results of novel treatments studied in registered trials ( www.ClinicalTrials.gov ). Cellular signaling pathways activated in endometriotic cells, which constitute potential targets for future treatments, are also described. Expert opinion: Therapeutic research efforts should focus on identifying and testing substances capable of acting locally on the lesions themselves, without interfering with ovulation, in order to be efficacious on both pain symptoms and infertility.

Tumor necrosis factor-α activates estrogen signaling pathways in endometrial epithelial cells via estrogen receptor α

The pro-inflammatory cytokine TNF-α and the female hormone estrogen have been implicated in the pathophysiology of two common gynecological diseases, endometriosis and endometrial adenocarcinoma. Here we describe a novel capacity of TNF-α to activate ER signaling in endometrial epithelial cells. TNF-α induced luciferase expression in the absence and presence of estradiol and also augmented expression of the estrogen-regulated genes c-fos, GREB1, and progesterone receptor. Furthermore, TNF-α mediated ER transcriptional activity is dependent on the Extracellular Regulated Kinase (ERK) 1/2 pathway. Co-treatment with a pure ER antagonist resulted in an inhibition of this TNF-α-induced ERE luciferase activity and gene expression, demonstrating that this cytokine signals through ERs. Additional investigations confirmed that TNF-α acts specifically via ERα. Taken together, these data provide a rationale for the potential use of inhibitors of TNF-α and estrogen production/activity in combination for the treatment of endometrial pathologies.

Recruitment of CCR6-expressing Th17 cells by CCL 20 secreted from IL-1 beta-, TNF-alpha-, and IL-17A-stimulated endometriotic stromal cells

In a novel paradigm of T cell differentiation, type 17 T helper (Th17) cells may play a significant role in endometriosis, a chronic inflammatory disease. However, the mechanism regulating the accumulation of Th17 cells in endometriotic tissues remains unknown. We hypothesized that Th17 cells migrate to endometriotic tissues through an interaction of the chemokine CC chemokine ligand (CCL)20 and its receptor CCR6. Using endometriotic tissues from women with endometriosis, we demonstrated, by flow cytometry, that Th17 cells in endometriotic tissues express CC chemokine receptor (CCR)6. Immunohistochemistry also revealed that CCL20 was expressed in the epithelial cells and stromal cells beneath the epithelium of endometriotic tissues. CCR6+ cells were small and round and scattered in the stroma in which abundant CCL20+ cells were detected. CCL20 caused selective migration of Th17 cells in the peripheral blood in a migration assay. IL-1β, TNF-α, and IL-17A increased the secretion of CCL20 in cultured endometriotic stromal cells. Inhibitors of p38- and p42/44-MAPKs, and stress-activated protein kinase/c-Jun kinase suppressed the secretion of CCL20 increased by IL-1β, TNF-α, and IL-17A. This suggests that the CCL20/CCR6 system is involved in the migration of Th17 cells to endometriotic tissues and that proinflammatory cytokines contribute to the development of endometriosis via up-regulation of CCL20 secretion from endometriotic stromal cells.

Evaluation of polymorphisms in predicted target sites for micro RNAs differentially expressed in endometriosis

Previous microarray analyses identified 22 microRNAs (miRNAs) differentially expressed in paired ectopic and eutopic endometrium of women with and without endometriosis. To investigate further the role of these miRNAs in women with endometriosis, we conducted an association study aiming to explore the relationship between endometriosis risk and single-nucleotide polymorphisms (SNPs) in miRNA target sites for these differentially expressed miRNAs. A panel of 102 SNPs in the predicted miRNA binding sites were evaluated for an endometriosis association study and an ingenuity pathway analysis was performed. Fourteen rare variants were identified in this study. We found SNP rs14647 in the Wolf-Hirschhorn syndrome candidate gene1 (WHSC1) 3'UTR (untranslated region) was associated with endometriosis-related infertility presenting an odds ratio of 12.2 (95% confidence interval = 2.4-60.7, P = 9.03 × 10(-5)). SNP haplotype AGG in the solute carrier family 22, member 23 (SLC22A23) 3'UTR was associated with endometriosis-related infertility and more severe disease. With the individual genotyping data, ingenuity pathways analysis identified the tumour necrosis factor and cyclin-dependant kinase inhibitor as major factors in the molecular pathways. Significant associations between WHSC1 alleles and endometriosis-related infertility and SLC22A23 haplotypes and the disease severe stage were identified. These findings may help focus future research on subphenotypes of this disease. Replication studies in independent large sample sets to confirm and characterize the involvement of the gene variation in the pathogenesis of endometriosis are needed.

Endometriosis research: animal models for the study of a complex disease

Endometriosis is a common gynaecological disease that is characterized and defined as the presence of endometrial tissue outside the uterus, causing painful periods and subfertility in approximately 10% of women. After more than 50 years of research, little is known about the mechanisms underlying the development and establishment of this condition. Animal models allow us to study the temporal sequence of events involved in disease establishment and progression. Also, because this disease occurs spontaneously only in humans and non-human primates and there are practical problems associated with studying the disease, animal models have been developed for the evaluation of endometriosis. This review describes the animal models for endometriosis that have been used to date, highlighting their importance for the investigation of disease mechanisms that would otherwise be more difficult to elucidate, and proposing new alternatives aimed at overcoming some of these limitations.