Peroxisome proliferator-activated receptor-(gamma) receptor ligand partially prevents the development of endometrial explants in baboons: a prospective, randomized, placebo-controlled study

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.

The role of peroxisome proliferator-activated receptors in endometriosis

Endometriosis constitutes the most common cause of chronic pelvic pain in female patients and is associated with infertility. Although there is no known cause for the disease, it is a heritable condition that is determined by numerous genetic, epigenetic, and environmental aspects. Peroxisome proliferator-activated receptors (PPARs) represent nuclear receptor proteins that control gene expression. By using the MEDLINE and LIVIVO databases we conducted a literature review in order to look into the role of PPARs in the endometriosis pathophysiology and succeeded in revealing 36 pertinent publications between 2001 and 2022. In regards to PPAR expression in endometriosis, PPARγ seems to represent the most studied PPAR isoform in endometriosis and to influence various pathways involved in the disease onset and progression. It's interesting to note that diverse treatment agents targeting the PPAR system have been identified as innovative, effective therapeutic alternatives in the context of endometriosis treatment. In conclusion, PPARs appear to contribute an important role in both endometriosis pathophysiology and therapy.

Evaluation of the potential role of diethylstilbestrol on the induction of endometriosis in a rat model - An alternative approach

Endometriosis is known to be a gynaecological condition characterised by persistent inflammation and abnormal development of endometrial stroma and glands. Researchers require a rodent model to analyse the disease environment. Animal models are the best option for investigating the etiology and effective treatment of debilitating illnesses in women since rodents, like humans, menstruate. In order to develop the model system, diethylstilbestrol (DES) was examined for its ability to induce endometriosis in rats by investigating its effect on the estrus cycle, hormones, and key markers. The results demonstrated that animals given DES had an erratic estrus cycle and aberrant hormone levels. Histomorphology revealed the development of an endometriosis environment with degenerative epithelium and enlarged glandular cells after DES induction. The higher levels of estrogen, progesterone, and MCP-1 were shown in the endometriosis induced animals. Endometriosis-induced groups had decreased levels of HOXA10 and HOXA11 and increased levels of VEGF and COX-2. Finally, the DES demonstrated endometriosis induction efficacy, implying that it might be a viable replacement for endometriosis induction.

PPARγ Agonists: Emergent Therapy in Endometriosis

Endometriosis is one of the major gynecological diseases of reproductive-age women. This disease is characterized by the presence of glands and stroma outside the uterine cavity. Several studies have shown the major role of inflammation, angiogenesis, adhesion and invasion, and apoptosis in endometriotic lesions. Nevertheless, the mechanisms underlying endometriotic mechanisms still remain unclear and therapies are not currently efficient. The introduction of new agents can be effective by improving the condition of patients. PPARγ ligands can directly modulate these pathways in endometriosis. However, data in humans remain low. Thus, the purpose of this review is to summarize the potential actions of PPARγ agonists in endometriosis by acting on inflammation, angiogenesis, invasion, adhesion, and apoptosis.

Establishment of endometriotic models: the past and future

Endometriosis is a prevalent chronic disease that affects approximately 6% to 10% of reproductive-aged women. Although numerous researchers have endeavored to explore the etiology of endometriosis over a century, its etiology still remains an enigma. The exploration of pathophysiologic mechanism and novel therapy for endometriosis depends on ideal endometriotic models. In the previous decade, various endometriotic models have been established; therefore, we made a conclusion for available information on these models. This review summarized the common experimental models used in endometriotic studies, including their origins, characteristics, applications, and limitations. Endometriotic models played an important role in studying etiologies and novel treatments of endometriosis during the last decades. Among them, animal models and endometriotic cell lines were viewed as most common studying tools to explore the intrinsic entities of endometriosis. In addition, endometrial organoid also emerged and was regarded as an ideal studying tool for endometriosis research. Different research models collectively complement each other to advance the endometriosis research. The successful establishment of endometrial organoids means that organoids are expected to become an ideal model for studying endometriosis in the future.

Revisiting estrogen-dependent signaling pathways in endometriosis: Potential targets for non-hormonal therapeutics

Endometriosis is an estrogen-dependent gynecologic disease. Endometriotic cells survive in oxidative stress and hypoxic environments. The aim of this review is to reconsider new therapeutic strategies for endometriosis by focusing on estrogen signaling, ROS production and scavenging, and mitochondrial metabolism. Each keyword alone or in combination was used to search from PubMed and Embase by applying the filters of the title and the publication years between January 2000 and May 2020. Abnormal epigenetic marks of estrogen receptors (ERs) in endometriosis cause overexpression of ERβ, progesterone resistance, inflammation, anti-apoptosis, and mitochondrial metabolic modification. In addition to hormonal action, estrogen is involved in various functions such as mitochondrial biosynthesis and energy metabolism. Estrogen works with its downstream target genes to modulate mitochondrial gene expression, regulate ROS production, and affect mitochondrial biology, including ATP production, antioxidant defenses, mitochondrial biosynthesis, quality control, and energy-transducing capacity. Endometriosis can shift mitochondrial metabolism from oxidative phosphorylation to aerobic glycolysis. This metabolic conversion suppresses ROS production and thus activates the survival signal of endometriotic cells. Therefore, molecules associated with aerobic glycolysis and mitochondrial metabolism are considered therapeutic targets for endometriosis. In conclusion, estrogen downstream target genes involved in mitochondrial metabolic biosynthesis may be potential targets for non-hormonal treatment of endometriosis.

Rosiglitazone affects the progression of surgically‑induced endometriosis in a rat model

Endometriosis is closely associated with inflammatory reactions and angiogenesis. Whether PPARγ is a target for the treatment of endometriosis remains unknown. The present study was designed to investigate the impact of a PPARγ agonist (rosiglitazone, RSG) on endometriosis in a rat model and to identify the underlying mechanism. The endometriosis model was established in rats. The pathological state of the endometrium was examined using hematoxylin‑eosin staining. The microstructures of interest were visualized using electron microscopy. Western blot analysis and reverse transcription‑quantitative polymerase chain reaction were used to detect PPARγ and MAT2A expression. VEGF and caspase‑3 expression were investigated using immunohistochemistry. Pathological analysis revealed transparent and red nodules in the model group, and that vasoganglions were present all over the nodules. Endometrial epithelial hyperplasia was observed in the model group, and the shape was columnar. Increased interstitial cell numbers, with compact structure and abundant blood supply, were detected in the model group. Compared with the model group, incomplete epithelial structures with sparse interstitial cells and loose structure were observed in the pathological images from RSG treatment groups. Numerous inflammatory cells and poor blood supply were observed in the endometrial tissues, and the gland was filled mostly with vacuolar cells. Electron microscopy revealed that the tissue structure was integrated. Many vacuoles were formed within the endometrial tissue and the classical morphological changes of apoptotic cells were observed in RSG‑treated groups. Caspase‑3 and PPARγ expression increased and expression of VEGF and MAT2A decreased in RSG‑treated groups. Taken together, these results revealed that RSG impacts the development and progression of endometriosis likely by inhibiting angiogenesis and inducing apoptosis.

What Have We Learned from Animal Models of Endometriosis and How Can We Use the Knowledge Gained to Improve Treatment of Patients?

Endometriosis is a complex disorder with a high socio-economic impact. Development of effective novel drug therapies which can be given to women to relieve chronic pain symptoms without side effects such as hormone suppression is urgently required, but progress has been slow. Several different rodent models of 'endometriosis' have been developed, the majority of which mimic aspects of peritoneal disease (e.g. 'lesions' in peritoneal cavity either surgically or spontaneously attached to wall, mesentery, fat). Results obtained using these models have informed our understanding of aetiology including evidence for differential expression of regulatory factors in lesions and impacts on pain perception and fertility. Refinement of these models to ensure reproducibility, extension of models to replicate ovarian and deep disease, complementary in vitro approaches and robust experimental design are all needed to ensure preclinical drug testing results in positive findings in clinical trials and translation for patient benefit.

Endometriosis

Endometriosis is a common inflammatory disease characterized by the presence of tissue outside the uterus that resembles endometrium, mainly on pelvic organs and tissues. It affects ~5-10% of women in their reproductive years - translating to 176 million women worldwide - and is associated with pelvic pain and infertility. Diagnosis is reliably established only through surgical visualization with histological verification, although ovarian endometrioma and deep nodular forms of disease can be detected through ultrasonography and MRI. Retrograde menstruation is regarded as an important origin of the endometrial deposits, but other factors are involved, including a favourable endocrine and metabolic environment, epithelial-mesenchymal transition and altered immunity and inflammatory responses in genetically susceptible women. Current treatments are dictated by the primary indication (infertility or pelvic pain) and are limited to surgery and hormonal treatments and analgesics with many adverse effects that rarely provide long-term relief. Endometriosis substantially affects the quality of life of women and their families and imposes costs on society similar to those of other chronic conditions such as type 2 diabetes mellitus, Crohn's disease and rheumatoid arthritis. Future research must focus on understanding the pathogenesis, identifying disease subtypes, developing non-invasive diagnostic methods and targeting non-hormonal treatments that are acceptable to women who wish to conceive.

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.

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.

The endometriotic tissue lining the internal surface of endometrioma: hormonal, genetic, epigenetic status, and gene expression profile

Ovarian endometriomas are found in a consistent proportion of patients with endometriosis and are associated with a more severe form of the disease. The endometriotic tissue lining the inside of the endometrioma has been extensively studied over the years mostly for the need to compare the molecular and cellular characteristics of eutopic and ectopic endometria. Several aspects of hormonal regulation, response to local inflammation, carcinogenesis, and modifications of the local environment have been investigated in order to characterize also the processes associated with peritoneal endometriosis. In this review, we have summarized the current knowledge of pathophysiology of endometrioma, with a particular focus on the cellular components lining the internal surface of the cyst in order to provide a comprehensive overview of the hormonal, genetic, epigenetic, and gene expression profiles of this essential part of the cyst.

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.

Serum Polyunsaturated Fatty Acids and Endometriosis

Polyunsaturated fatty acids (PUFAs) are fatty acids containing 2 or more double bonds, and they are classified by the location of the last double bond. Omega 3 (n-3) and omega 6 (n-6) PUFAs are obtained through food sources including fatty fish and seed/vegetable oils, respectively, and they are important to a number of physiologic processes including inflammation. Previous work demonstrates suppressive effects of n-3 PUFAs on endometriotic lesions in animal models and decreased risk of endometriosis among women with high n-3 PUFA intake. Thus, we sought to determine the relationship between circulating levels of PUFAs and endometriosis in women. To do this, we performed a cross-sectional study of serum PUFAs and clinical data from 205 women undergoing in vitro fertilization (IVF). Serum PUFAs were measured using liquid chromatography coupled to tandem mass spectroscopy and included n-3 PUFAs such as α-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid and n-6 PUFAs such as linoleic acid and arachidonic acid. Multivariable logistic regression was used to determine relationships between specific and total serum PUFAs and patient history of endometriosis. Women with high serum EPA levels were 82% less likely to have endometriosis compared to women with low EPA levels (odds ratio = 0.18, 95% confidence interval 0.04-0.78).

Regression of experimental endometriotic implants in a rat model with the angiotensin II receptor blocker losartan

AIM

Endometriosis is a common disease in women of reproductive age, and many different treatments have been developed, although none has provided a cure. In this study, the efficacy of losartan, an angiotensin II type 1 receptor blocker and an antiangiogenic and anti-inflammatory agent, on regression of experimental endometriotic implants in a rat model was investigated.

METHODS

Peritoneal endometriosis was surgically induced in 16 mature female Sprague-Dawley rats. The peritoneal endometriotic implant was confirmed after 28 days, and the animals were divided randomly into two groups. The control group (n = 8) was given 4 mL/day tap water by oral gavage, and the losartan group (n = 8) was given 20 mg/kg per day losartan p.o. We compared endometriotic implant size, extent and severity of adhesion, as well as plasma and peritoneal lavage fluid cytokine levels including vascular endothelial growth factor (VEGF) and tumor necrosis factor (TNF)-α, plasma inflammatory factor pentraxin-3 (PTX-3) and C-reactive protein (CRP) between the treatment groups.

RESULTS

Mean surface endometriotic area, histological score of implants, adhesion formation, plasma VEGF, TNF, PTX-3 and CRP levels were significantly lower in the losartan group compared with control (P < 0.05). Furthermore, the peritoneal VEGF level was lower in the losartan group than in the control group (P < 0.001), but peritoneal TNF-α was similar in both groups (P > 0.05).

CONCLUSION

Losartan suppressed the implant surface area of experimental endometriosis in rats and reduced the levels of plasma VEGF, TNF-α, PTX-3 and CRP.

Genome-wide enrichment analysis between endometriosis and obesity-related traits reveals novel susceptibility loci

Endometriosis is a chronic inflammatory condition in women that results in pelvic pain and subfertility, and has been associated with decreased body mass index (BMI). Genetic variants contributing to the heritable component have started to emerge from genome-wide association studies (GWAS), although the majority remain unknown. Unexpectedly, we observed an intergenic locus on 7p15.2 that was genome-wide significantly associated with both endometriosis and fat distribution (waist-to-hip ratio adjusted for BMI; WHRadjBMI) in an independent meta-GWAS of European ancestry individuals. This led us to investigate the potential overlap in genetic variants underlying the aetiology of endometriosis, WHRadjBMI and BMI using GWAS data. Our analyses demonstrated significant enrichment of common variants between fat distribution and endometriosis (P = 3.7 × 10⁻³), which was stronger when we restricted the investigation to more severe (Stage B) cases (P = 4.5 × 10⁻⁴). However, no genetic enrichment was observed between endometriosis and BMI (P = 0.79). In addition to 7p15.2, we identify four more variants with statistically significant evidence of involvement in both endometriosis and WHRadjBMI (in/near KIFAP3, CAB39L, WNT4, GRB14); two of these, KIFAP3 and CAB39L, are novel associations for both traits. KIFAP3, WNT4 and 7p15.2 are associated with the WNT signalling pathway; formal pathway analysis confirmed a statistically significant (P = 6.41 × 10⁻⁴) overrepresentation of shared associations in developmental processes/WNT signalling between the two traits. Our results demonstrate an example of potential biological pleiotropy that was hitherto unknown, and represent an opportunity for functional follow-up of loci and further cross-phenotype comparisons to assess how fat distribution and endometriosis pathogenesis research fields can inform each other.

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.

The dynamics of nuclear receptors and nuclear receptor coregulators in the pathogenesis of endometriosis

BACKGROUND

Endometriosis is defined as the colonization and growth of endometrial tissue at anatomic sites outside the uterine cavity. Up to 15% of reproductive-aged women in the USA suffer from painful symptoms of endometriosis, such as infertility, pelvic pain, menstrual cycle abnormalities and increased risk of certain cancers. However, many of the current clinical treatments for endometriosis are not sufficiently effective and yield unacceptable side effects. There is clearly an urgent need to identify new molecular mechanisms that critically underpin the initiation and progression of endometriosis in order to develop more specific and effective therapeutics which lack the side effects of current therapies. The aim of this review is to discuss how nuclear receptors (NRs) and their coregulators promote the progression of endometriosis. Understanding the pathogenic molecular mechanisms for the genesis and maintenance of endometriosis as modulated by NRs and coregulators can reveal new therapeutic targets for alternative endometriosis treatments.

METHODS

This review was prepared using published gene expression microarray data sets obtained from patients with endometriosis and published literature on NRs and their coregulators that deal with endometriosis progression. Using the above observations, our current understanding of how NRs and NR coregulators are involved in the progression of endometriosis is summarized.

RESULTS

Aberrant levels of NRs and NR coregulators in ectopic endometriosis lesions are associated with the progression of endometriosis. As an example, endometriotic cell-specific alterations in gene expression are correlated with a differential methylation status of the genome compared with the normal endometrium. These differential epigenetic regulations can generate favorable cell-specific NR and coregulator milieus for endometriosis progression. Genetic alterations, such as single nucleotide polymorphisms and insertion/deletion polymorphisms of NR and coregulator genes, are frequently detected in ectopic lesions compared with the normal endometrium. These genetic variations impart new molecular properties to NRs and coregulators to increase their capacity to stimulate progression of endometriosis. Finally, post-translational modifications of NR coregulators, such as proteolytic processing, generate endometriosis-specific isoforms. Compared with the unmodified coregulators, these coregulator isoforms have unique functions that enhance the pathogenesis of endometriosis.

CONCLUSIONS

Epigenetic/genetic variations and posttranslational modifications of NRs and coregulators alter their original function so that they become potent 'drivers' of endometriosis progression.

Combined blockade of angiotensin II type 1 receptor and activation of peroxisome proliferator-activated receptor-γ by telmisartan effectively inhibits vascularization and growth of murine endometriosis-like lesions

STUDY QUESTION

Is telmisartan effective in the treatment of endometriosis?

SUMMARY ANSWER

Combined blockade of angiotensin II type 1 receptor (AT1R) and activation of peroxisome proliferator-activated receptor (PPAR)-γ by telmisartan inhibits vascularization and growth of murine endometriosis-like lesions.

WHAT IS KNOWN ALREADY

AT1R and PPAR-γ are involved in the regulation of inflammation, proliferation and angiogenesis. These processes are also crucial for the pathogenesis of endometriosis and both receptors are expressed in endometrial tissue. Telmisartan is a partial agonist of PPAR-γ, which additionally blocks AT1R.

STUDY DESIGN, SIZE, DURATION

This was a randomized study in the mouse dorsal skinfold chamber and peritoneal model of endometriosis. Endometriosis-like lesions were induced in dorsal skinfold chambers of 21 female C57BL/6 mice, and in the peritoneal cavity of 15 additional animals, which were daily treated with an i.p. injection of pioglitazone (10 mg/kg, n = 12), telmisartan (10 mg/kg, n = 12) or vehicle (5% dimethyl sulfoxide (DMSO), n = 12) throughout an observation period of 14 and 28 days, respectively.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The anti-angiogenic actions of pioglitazone, a full PPAR-γ agonist, and telmisartan were firstly assessed in vitro by an aortic ring assay. Endometriosis-like lesions were induced in the dorsal skinfold chamber or peritoneal cavity and the effects of telmisartan and pioglitazone on their vascularization, immune cell content and growth were studied by intravital fluorescence microscopy, high-resolution ultrasound imaging as well as histological, immunohistochemical and immunofluorescent analyses. Additional quantitative real-time polymerase chain reaction (qRT-PCR) arrays served for gene expression profiling of the lesions. To limit the role of chance, the experiments were conducted under standardized laboratory conditions with appropriate vehicle-treated controls. Statistical significance was accepted for a value of P < 0.05.

MAIN RESULTS AND THE ROLE OF CHANCE

Telmisartan inhibited vascular sprout formation of aortic rings more effectively than pioglitazone. Accordingly, endometriosis-like lesions in dorsal skinfold chambers of telmisartan-treated animals exhibited a markedly lower functional microvessel density and blood perfusion. High-resolution ultrasound analyses of peritoneal endometriosis-like lesions revealed that the compound inhibited the stromal tissue growth, resulting in a significantly reduced final lesion volume. In contrast, the development of cysts did not differ between the groups. Moreover, telmisartan induced an up-regulation of PPAR-γ and a down-regulation of AT1R proteins in endometriosis-like lesions, which was associated with a decreased density of CD31-positive microvessels, a reduced immune cell content and a lower number of Ki67-positive proliferating cells. qRT-PCR arrays further demonstrated an inhibitory action of telmisartan on the expression of several angiogenic and inflammatory genes.

LIMITATIONS, REASONS FOR CAUTION

Endometriosis-like lesions were induced by syngeneic tissue transplantation into recipient mice without the use of pathological endometriotic tissue of human nature. Therefore, the results obtained in this study may not fully relate to human patients with endometriosis.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrates that telmisartan inhibits vascularization, immune cell content and growth of endometriosis-like lesions. Accordingly, the combined blockade of AT1R and activation of PPAR-γ represents a promising new concept in the development of novel compounds for the treatment of endometriosis.

STUDY FUNDING/COMPETING INTEREST(S)

There was no specific funding of this study. The authors have no conflicts of interest to declare.

PPARγ activation inhibits growth and survival of human endometriotic cells by suppressing estrogen biosynthesis and PGE2 signaling

Endometriosis is a chronic inflammatory disease of reproductive age women leading to chronic pelvic pain and infertility. Current antiestrogen therapies are temporizing measures, and endometriosis often recurs. Potential nonestrogenic or nonsteroidal targets are needed for treating endometriosis. Peroxisome proliferator-activated receptor (PPAR)γ, a nuclear receptor, is activated by thiazolidinediones (TZDs). In experimental endometriosis, TZDs inhibit growth of endometriosis. Clinical data suggest potential use of TZDs for treating pain and fertility concurrently in endometriosis patients. Study objectives were to 1) determine the effects of PPARγ action on growth and survival of human endometriotic epithelial and stromal cells and 2) identify the underlying molecular links between PPARγ activation and cell cycle regulation, apoptosis, estrogen biosynthesis, and prostaglandin E2 biosynthesis and signaling in human endometriotic epithelial and stromal cells. Results indicate that activation of PPARγ by TZD ciglitazone 1) inhibits growth of endometriotic epithelial cells 12Z up to 35% and growth of endometriotic stromal cells 22B up to 70% through altered cell cycle regulation and intrinsic apoptosis, 2) decreases expression of PGE2 receptors (EP)2 and EP4 mRNAs in 12Z and 22B cells, and 3) inhibits expression and function of P450 aromatase mRNA and protein and estrone production in 12Z and 22B cells through EP2 and EP4 in a stromal-epithelial cell-specific manner. Collectively, these results indicate that PGE2 receptors EP2 and EP4 mediate actions of PPARγ by incorporating multiple cell signaling pathways. Activation of PPARγ combined with inhibition of EP2 and EP4 may emerge as novel nonsteroidal therapeutic targets for endometriosis-associated pain and infertility, if clinically proven safe and efficacious.

The influence of endocrine disruptors in a selected population of infertile women

Several studies report that endocrine disrupting chemicals (EDC) able to interfere with endocrine homeostasis may affect women's reproductive health. We analyzed EDC serum levels and nuclear receptors (NRs) expression in order to have an indication of the internal dose of biologically active compounds and a measurement of indicators of their effects, as a result of the repeated uptake from environmental source. The percentage of patients with detectable bisphenol A (BPA) concentrations was significantly higher in the infertile patients compared with fertile subjects. No significant difference was found between the groups with regard to perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), mono-ethylhexyl phthalate (MEHP) and di-(2-ethylhexyl) phthalate (DEHP) concentrations. Among infertile women, the mean expression of estrogen receptor alpha (ERα) and beta (Erβ), androgen receptor (AR) and pregnane X receptor (PXR) was significantly higher than fertile patients. The mean expression of aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor gamma (PPARγ) did not show significant differences between two groups. Patients with endometriosis had higher levels of PPARγ than all women with other causes of infertility. This study led further support to EDC exposure as a risk factor for women's fertility.

Medical management of endometriosis: emerging evidence linking inflammation to disease pathophysiology

Progesterone action normally mediates the balance between anti-inflammatory and proinflammatory processes throughout the female reproductive tract. However, in women with endometriosis, endometrial progesterone resistance, characterized by alterations in progesterone responsive gene and protein expression, is now considered a central element in disease pathophysiology. Recent studies additionally suggest that the peritoneal microenvironment of endometriosis patients exhibits altered physiological characteristics that may further promote inflammation-driven disease development and progression. Within this review, we summarize our current understanding of the pathogenesis of endometriosis with an emphasis on the role that inflammation plays in generating not only the progesterone-resistant eutopic endometrium but also a peritoneal microenvironment that may contribute significantly to disease establishment. Viewing endometriosis from the emerging perspective that a progesterone resistant endometrium and an immunologically compromised peritoneal microenvironment are biologically linked risk factors for disease development provides a novel mechanistic framework to identify new therapeutic targets for appropriate medical management.

Inflammation, NK cells and implantation: friend and foe (the good, the bad and the ugly?): replacing placental viviparity in an evolutionary perspective

This review summarises an invited talk presented at the 2012 ESRI/ASRI meeting in Hamburg, concerning current views of inflammation in pregnancy, which is timely given that the effects of a local injury in the uterus acts to favour implantation. Recalling that inflammation can be good (it is useful and necessary for implantation), bad (in implantation failure, RSA) and ugly (at the extreme, endometriosis is associated with pain and infertility) leads to consideration of its status in pregnancy. Its role in implantation and the fact that pregnancy maintains some aspects of inflammation throughout, leads to revision of not only concepts of immunosuppression and the Th1/Th2 paradigm, but also the feto-maternal relationship as seen since Medawar's hypotheses were advanced. This is examined from an evolutionary perspective, which should lead to further review of our perception of uterine NK cells, and the emergence of Treg cells to control some aspects of adaptive immunity, which appeared long after placentation.

New trends for the medical treatment of endometriosis

INTRODUCTION

Endometriosis is a benign sex hormone-dependent gynecological disease, characterized by the presence and growth of endometrial tissue outside the uterus; it affects 10% of women of reproductive age and is associated with infertility and pain. Treatment of endometriosis involves conservative or radical surgery, or medical therapies. The goals for endometriosis treatment may be the relief of pain and/or a successful pregnancy achievement in infertile patients. Treatment must be individualized with a multidisciplinary approach. The classical treatments carry adverse side effects and in some cases a negative impact on quality of life. New agents promise a distinct perspective in endometriosis treatment.

AREAS COVERED

The aim of this paper is to systematically review the literature evidence of new medical treatments for endometriosis, defined as pharmacological treatments not yet commonly available and currently under investigation.

EXPERT OPINION

These new medical therapies would be used associated with surgical treatment and, in the future, will render possible the association of hormone therapy with non-hormonal treatment for endometriosis.

Immune interactions in endometriosis

Endometriosis is a common, complex gynecologic disorder characterized by the presence of endometrial glands and stroma at extrauterine (ectopic) sites. In women who develop this disease, alterations in specific biological processes involving both the endocrine and immune systems have been observed, which may explain the survival and growth of displaced endometrial tissue in affected women. In the past decade, a considerable amount of research has implicated a role for alterations in progesterone action at both eutopic and ectopic sites of endometrial growth which may contribute to the excessive inflammation associated with progression of endometriosis; however, it remains unclear whether these anomalies induce the condition or are simply a consequence of the disease process. In this article, we summarize current knowledge of alterations within the immune system of endometriosis patients and discuss how endometrial cells from women with this disease not only have the capacity to escape immunosurveillance, but also use inflammatory mechanisms to promote their growth within the peritoneal cavity. Finally, we discuss evidence that exposure to an environmental endocrine disruptor, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin, can mediate the development of an endometrial phenotype that exhibits both reduced progesterone responsiveness and hypersensitivity to proinflammatory stimuli mimicking the endometriosis phenotype. Future studies in women with endometriosis should consider whether a heightened inflammatory response within the peritoneal microenvironment contributes to the development and persistence of this disease.

Peroxisome proliferating activating receptor gamma-independent attenuation of interleukin 6 and interleukin 8 secretion from primary endometrial stromal cells by thiazolidinediones

OBJECTIVE

To assess the effect of thiazolidinediones on the regulation of inflammatory cytokines related to endometriosis in endometrial tissue and determine whether these effects occur via activation of the peroxisome proliferating activating receptor gamma (PPAR)-γ.

DESIGN

In vitro study using eutopic endometrial tissue.

SETTING

University hospital.

PATIENT(S)

Premenopausal women undergoing laparoscopy for infertility or abdominal pain.

INTERVENTION(S)

Isolation of endometrial stromal cells and the culture of these cells in the presence of thiazolidinediones, ciglitazone and pioglitazone, both with and without a pretreatment of the specific, irreversible PPAR-γ antagonist GW9662.

MAIN OUTCOME MEASURE(S)

Quantitation of interleukin (IL)-6 and IL-8 released into the cell culture medium by ELISA. Real-time polymerase chain reaction to quantitate PPAR-γ gene expression in the primary cell preparations and the expression of IL-6 and IL-8 after thiazolidinedione treatment.

RESULT(S)

Treatment of stromal cells with thiazolidinediones attenuated IL-6 and IL-8 release in a dose-dependent manner. This effect was not inhibited by GW9662 pretreatment. Ciglitazone induced IL-6 messenger RNA expression, an effect that was suppressed by GW9662 pretreatment.

CONCLUSION(S)

Thiazolidinediones decrease the proinflammatory cytokines IL-6 and IL-8 in endometrial stromal cells via a PPAR-γ-independent mechanism. A better understanding of the anti-inflammatory action of this class of drugs may improve their safety and efficacy for endometriosis treatment.

The inhibitory effect of celecoxib and rosiglitazone on experimental endometriosis

OBJECTIVE

To evaluate the effects of celecoxib and rosiglitazone on the implantation and growth of endometriotic-like lesions in a murine model of endometriosis.

DESIGN

Prospective experimental study.

SETTING

Animal research and laboratory facility.

ANIMAL(S)

Two-month-old female BALB/c mice.

INTERVENTION(S)

Surgically induced endometriosis in female BALB/C mice; 28 days of treatment with celecoxib, rosiglitazone, or their combination; counting, measuring, excising, and fixing lesions.

MAIN OUTCOME MEASURE(S)

Immunohistochemical examination for proliferating cell nuclear antigen (PCNA), CD31, and CD34 to assess cell proliferation and vascularization, with the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) technique for apoptosis evaluation.

RESULT(S)

Celecoxib and the combined treatment (celecoxib and rosiglitazone) statistically significantly reduced the mean number of lesions established per mouse, and all treatments diminished the implant volume. In addition, cell proliferation within the implants was statistically significantly reduced, and apoptosis was statistically significantly enhanced by all treatments. Also, we found that all treatments diminished the vascularized area in the lesion.

CONCLUSION(S)

These results are promising and reveal that celecoxib and rosiglitazone, combined or separately, have a beneficial effect on overall endometriotic growth.