Reduced progesterone action during endometrial maturation: a potential risk factor for the development of endometriosis

Mare stromal endometrial cells differentially modulate inflammation depending on oestrus cycle status: an in vitro study

The modulation of inflammation is pivotal for uterine homeostasis. Here we evaluated the effect of the oestrus cycle on the expression of pro-inflammatory and anti-inflammatory markers in a cellular model of induced fibrosis. Mare endometrial stromal cells isolated from follicular or mid-luteal phase were primed with 10 ng/mL of TGFβ alone or in combination with either IL1β, IL6, or TNFα (10 ng/mL each) or all together for 24 h. Control cells were not primed. Messenger and miRNA expression were analyzed using real-time quantitative PCR (RT-qPCR). Cells in the follicular phase primed with pro-inflammatory cytokines showed higher expression of collagen-related genes (CTGF, COL1A1, COL3A1, and TIMP1) and mesenchymal marker (SLUG, VIM, CDH2, and CDH11) genes; p < 0.05. Cells primed during the mid-luteal overexpressed genes associated with extracellular matrix, processing, and prostaglandin E synthase (MMP2, MMP9, PGR, TIMP2, and PTGES; p < 0.05). There was a notable upregulation of pro-fibrotic miRNAs (miR17, miR21, and miR433) in the follicular phase when the cells were exposed to TGFβ + IL1β, TGFβ + IL6 or TGFβ + IL1β + IL6 + TNFα. Conversely, in cells from the mid-luteal phase, the treatments either did not or diminished the expression of the same miRNAs. On the contrary, the anti-fibrotic miRNAs (miR26a, miR29b, miR29c, miR145, miR378, and mir488) were not upregulated with treatments in the follicular phase. Rather, they were overexpressed in cells from the mid-luteal phase, with the highest regulation observed in TGFβ + IL1β + IL6 + TNFα treatment groups. These miRNAs were also analyzed in the extracellular vesicles secreted by the cells. A similar trend as seen with cellular miRNAs was noted, where anti-fibrotic miRNAs were downregulated in the follicular phase, while notably elevated pro-fibrotic miRNAs were observed in extracellular vesicles originating from the follicular phase. Pro-inflammatory cytokines may amplify the TGFβ signal in the follicular phase resulting in significant upregulation of extracellular matrix-related genes, an imbalance in the metalloproteinases, downregulation of estrogen receptors, and upregulation of pro-fibrotic factors. Conversely, in the luteal phase, there is a protective role mediated primarily through an increase in anti-fibrotic miRNAs, a decrease in SMAD2 phosphorylation, and reduced expression of fibrosis-related genes.

Aberrant epigenetic regulation of estrogen and progesterone signaling at the level of endometrial/endometriotic tissue in the pathomechanism of endometriosis

Endometriosis is a term referring to a condition whereby the endometrial tissue is found outside the uterine cavity. This progressive and debilitating condition affects up to 15% of women of reproductive age. Due to the fact that endometriosis cells may express estrogen receptors (ERα, Erβ, GPER) and progesterone (P4) receptors (PR-A, PR-B), their growth, cyclic proliferation, and breakdown are similar to the processes occurring in the endometrium. The underlying etiology and pathogenesis of endometriosis are still not fully explained. The retrograde transport of viable menstrual endometrial cells with the retained ability to attach within the pelvic cavity, proliferate, differentiate and invade into the surrounding tissue explains the most widely accepted implantation theory. Endometrial stromal cells (EnSCs) with clonogenic potential constitute the most abundant population of cells within endometrium that resemble the properties of mesenchymal stem cells (MSCs). Accordingly, formation of the endometriotic foci in endometriosis may be due to a kind of EnSCs dysfunction. Increasing evidence indicates the underestimated role of epigenetic mechanisms in the pathogenesis of endometriosis. Hormone-mediated epigenetic modifications of the genome in EnSCs or even MSCs were attributed an important role in the etiopathogenesis of endometriosis. The roles of excess estrogen exposure and P4 resistance were also found to be crucial in the development of epigenetic homeostasis failure. Therefore, the aim of this review was to consolidate the current knowledge regarding the epigenetic background of EnSCs and MSCs and the changed properties due to estrogen/P4 imbalances in the context of the etiopathogenesis of endometriosis.

Influence of the ectopic location on the antigen expression and functional characteristics of endometrioma stromal cells

RESEARCH QUESTION

Are the alterations observed in the endometriotic cells, such as progesterone resistance, already present in the eutopic endometrium or acquired in the ectopic location?

DESIGN

The response to decidualization with progesterone and cyclic AMP for up to 28 days was compared in different endometrial stromal cell (EnSC) lines established from samples of endometriomas (eEnSC), eutopic endometrium from women with endometriosis (eBEnSC), endometrial tissue from healthy women (BEnSC) and menstrual blood from healthy donors (mEnSC).

RESULTS

Usual features of decidualized cells, such as changes in cell morphology and expression of prolactin, were similarly observed in the three types of eutopic EnSC studied, but not in the ectopic cells upon decidualization. Among the phenotypic markers analysed, CD105 was down-regulated under decidualization in all cell types (mEnSC, P = 0.005; BEnSC, P = 0.029; eBEnSC, P = 0.022) except eEnSC. mEnSC and BEnSC underwent apoptosis during decidualization, whereas eBEnSC and eEnSC were resistant to the induction of cell death. Lastly, migration studies revealed that mEnSC secreted undetermined factors during decidualization that inhibited cell motility, whereas eEnSC showed a significantly lower ability to produce those migration-regulating factors (P < 0.0001, P  < 0.001 and P = 0.0013 for the migration of mEnSC at 24, 48 and 72 h, respectively; P  < 0.0001 for the migration of eEnSC at all times studied).

CONCLUSIONS

This study provides novel insights into the differences between endometriotic and eutopic endometrial cells and reinforces the idea that the microenvironment in the ectopic location plays additional roles in the acquisition of the alterations that characterize the cells of the endometriotic foci.

Circulating CD200 is increased in the secretory phase of women with endometriosis as is endometrial mRNA, and endometrial stromal cell CD200R1 is increased in spite of reduced mRNA

PROBLEM

Estrogen-dependent extrauterine implantation and growth of menstrual endometrial tissue affects roughly 10% of reproductive age women and depends on suppression of local innate immune defenses to prevent ectopic tissue rejection. Immunohistochemistry has shown the immune check-point inhibitor CD200 which can suppress rejection is expressed in eutopic endometrium and in ectopic deposits. Soluble CD200 accumulated in venules draining eutopic and ectopic endometrium of endometriosis cases in the secretory phase but not proliferative phase of the menstrual cycle, and should be increased in the circulation.

METHOD OF STUDY

Sera from endometriosis and non-endometriosis controls were tested by ELISA for CD200. Endometrial CD200, CD200R1 and CD200R2 mRNA in eutopic was quantified by RT-PCR and localized by in situ hybridization. CD200R1 protein was quantified by immunohistochemistry.

RESULTS

Secretory phase serum CD200 was elevated in women with endometriosis compared to controls. Serum CD200 correlated with matched endometrial CD200 mRNA levels. Expression of mRNA for CD200R1 which signals immune suppression was decreased whereas mRNA for the CD200R2 activating receptor was increased. In situ staining of CD200R1 and CD200R2 mRNA showed both receptors were expressed and the fraction of CD200R that is CD200R1 was reduced in secretory and menstrual phase endometriosis endometrium consistent with the RT-PCR result. By contrast, CD200R1 protein and CD200R1 fraction of total CD200R protein were increased in endometriosis.

CONCLUSIONS

Failure to suppress circulating CD200 levels in the secretory phase had an 87% specificity and 90% sensitivity for endometriosis. CD200 and increased CD200R1 expression may facilitate development of ectopic deposits by suppressing rejection mechanisms.

Endometriosis-associated infertility: From pathophysiology to tailored treatment

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

Role of AMPK/mTOR, mitochondria, and ROS in the pathogenesis of endometriosis

Endometriosis is the presence of endometrial tissue outside the uterine cavity usually in the ovaries, fallopian tube, and pelvic cavity. It's a chronic enigmatic gynecological condition associated with dysmenorrhea, dyspareunia, pelvic pain, and infertility. Endometriosis lesions exist in a unique microenvironment characterized by increased concentrations of hormones, inflammation, and oxidative stress. This environment promotes cell survival through the binding of membrane receptors and subsequent cascading activation of intracellular kinases that stimulate a cellular response. In endometriosis, well-established signaling pathways, mTOR and AMPK, are altered via steroid hormones and other factors to promote cell growth, migration, and proliferation. This is accompanied by dysfunction in the mitochondria that increase energy production to sustain proliferation demands consequently leading to reactive oxygen species overproduction. This review aims to summarize the role of altered mTOR/AMPK signaling pathway, mitochondrial dysfunction, and reactive oxygen species overproduction along with providing therapeutic and diagnostic approaches. Highlighting these factors would provide a better understanding to reach a coherent theory for the pathogenesis of endometriosis.

Whole-exome sequencing and functional validation reveals a rare missense variant in MMP7 confers ovarian endometriosis risk

Prior studies have shown that genetic factors play important roles in ovarian endometriosis. Herein, we first analyzed the WES data from 158 patients with ovarian endometriosis and 385 local control women without endometriosis. Among which, a rare missense variant in the MMP7 (p.I79T, rs150338402) gene exhibited significant frequency difference. This rare variant was screened in an additional 1176 patients and 600 control women via direct DNA sequencing. Meanwhile, a total of 38 available clinical characteristics were collected. Our results showed 45 out of 1334 (3.37%) patients, while 15 out of 985 control women (1.52%) (P = 0.0076) harbored this rare variant, respectively. This rare variant was associated with clinical features such as follicle stimulating hormone (FSH, Padj = 0.0342), luteinizing hormone (LH, Padj = 0.0038), progesterone (PROG, Padj = 1.4e-7), testosterone (TESTO, Padj = 0.0923), total bilirubin (TBIL, Padj = 0.0699), carcinoembryonic antigen (CEA, Padj = 0.0665), and squamous cell carcinoma antigen (SCC, Padj = 0.0817), respectively. Functional assays showed this rare variant could promote cell migration, invasion, epithelial-mesenchymal transition (EMT), and increase the proteolytic protein activity of MMP7, implicating that the increased capacities of cell invasion, migration, and EMT might be mediated by enhanced proteolytic activity of MMP7 mutant. These results showed the MMP7 rare missense variant (p.I79T) played important roles in the pathogenesis of ovarian endometriosis. In conclusion, we identified for the first time, a significantly enriched MMP7 rare variant in ovarian endometriosis; this rare variant was closely associated with certain clinical features in ovarian endometriosis, thus, it could be a promising early diagnostic biomarker for this disease.

Gut Microbiota Exceeds Cervical Microbiota for Early Diagnosis of Endometriosis

The diagnosis of endometriosis is typically delayed by years for the unexclusive symptom and the traumatic diagnostic method. Several studies have demonstrated that gut microbiota and cervical mucus potentially can be used as auxiliary diagnostic biomarkers. However, none of the previous studies has compared the robustness of endometriosis classifiers based on microbiota of different body sites or demonstrated the correlation among microbiota of gut, cervical mucus, and peritoneal fluid of endometriosis, searching for alternative diagnostic approaches. Herein, we enrolled 41 women (control, n = 20; endometriosis, n = 21) and collected 122 well-matched samples, derived from feces, cervical mucus, and peritoneal fluid, to explore the nature of microbiome of endometriosis patients. Our results indicated that microbial composition is remarkably distinguished between three body sites, with 19 overlapped taxa. Moreover, endometriosis patients harbor distinct microbial communities versus control group especially in feces and peritoneal fluid, with increased abundance of pathogens in peritoneal fluid and depletion of protective microbes in feces. Particularly, genera of Ruminococcus and Pseudomonas were identified as potential biomarkers in gut and peritoneal fluid, respectively. Furthermore, novel endometriosis classifiers were constructed based on taxa selected by a robust machine learning method. These results demonstrated that gut microbiota exceeds cervical microbiota in diagnosing endometriosis. Collectively, this study reveals important insights into the microbial profiling in different body sites of endometriosis, which warrant future exploration into the role of microbiota in endometriosis and highlighted values on gut microbiota in early diagnosis of endometriosis.

Unique Sensitivity of Uterine Tissue and the Immune System for Endometriotic Lesion Formation

Endometriosis is a debilitating disease that affects about 10% of reproductive-aged adolescents and women. The etiology of the disease is unknown; however, a prevailing hypothesis is that endometriosis develops from retrograde menstruation, where endometrial tissue and fluids flow back through the oviducts into the peritoneal cavity. There is no cure for endometriosis, and symptoms are treated palliatively. Despite the advances in knowledge, the complexity of endometriosis etiology is still unknown. Recent work by our group suggests that the initiation of endometriosis is immune-dependent. Using a mouse model of endometriosis, we hypothesized the initiation of endometriosis is immune regulated and uterine endometrium specific. In the absence of a functional immune system non-obese diabetic/severe combined immunodeficiency (NOD/SCID mice), endometriotic lesions did not form. Uterine endometrial tissue forms endometriotic lesions, whereas tissues with differing basal expression levels of estrogen receptor alpha (ESR1) and estrogen receptor beta (ESR2), similar cellular composition to uterus (i.e. bladder, mammary gland, and lung), and treated with estradiol did not form lesions. As MMP7 is known to play a major role in the organization/reorganization of the endometrium during the menstrual cycle, blocking metalloproteinase (MMP) activity significantly decreased the invasive properties of these cells. Together, these findings suggest that endometriosis is immune and uterine specific and that MMP7 likely plays a role in the ability of uterine tissue and the innate immune system to establish and maintain endometriotic lesions.

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin potential impacts on peripheral blood mononuclear cells of endometriosis women

Endometriosis happens following the implantation of endometrial-derived tissues outside the uterine cavity. It has been suggested that 2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin (TCDD) is involved in endometriosis development. Furthermore, aryl hydrocarbon receptor (AHR), as a TCDD receptor, has been demonstrated to regulate immune responses. Nonetheless, data regarding the mechanisms, through which TCDD influences the immune system in endometriosis, are still inconclusive. Therefore, frequency of regulatory T cells (Tregs) and the expression of FOXP3, AHR and indoleamine 2, 3-dioxygenase 1 (IDO1) from endometriosis and non-endometriosis individuals were investigated in the absence and presence of TCDD; also, the concentration of IL-6 and kynurenine in the supernatant of cultures was assessed. The impact of TCDD-treated PBMCs on the migration capacity of menstrual blood-derived stromal stem cells (MenSCs) and monocyte chemoattractant protein-1 (MCP-1) and IL-6 production was determined. Here, we found that AHR and IDO1 expression levels were lower in endometriosis PBMCs; however, TCDD treatment increased AHR, FOXP3, IDO1, IL-6, and Treg levels in the endometriosis group (P ≤ 0.05-0.0001). TCDD-treated PBMCs increased the migration capacity of MenSCs and up-regulated MCP-1 and IL-6 levels in the PBMCs/MenSCs co-culture (P ≤ 0.01-0.0001). In conclusion, these results shed light on the probable mechanisms, through which AHR activation by chemical toxicants can impact inflammatory immune mediators involved in the development of endometriosis; also, these data support the idea that TCDD could promote endometriosis progression.

Estrogen- and Progesterone (P4)-Mediated Epigenetic Modifications of Endometrial Stromal Cells (EnSCs) and/or Mesenchymal Stem/Stromal Cells (MSCs) in the Etiopathogenesis of Endometriosis

Endometriosis is a common chronic inflammatory condition in which endometrial tissue appears outside the uterine cavity. Because ectopic endometriosis cells express both estrogen and progesterone (P4) receptors, they grow and undergo cyclic proliferation and breakdown similar to the endometrium. This debilitating gynecological disease affects up to 15% of reproductive aged women. Despite many years of research, the etiopathogenesis of endometrial lesions remains unclear. Retrograde transport of the viable menstrual endometrial cells with retained ability for attachment within the pelvic cavity, proliferation, differentiation and subsequent invasion into the surrounding tissue constitutes the rationale for widely accepted implantation theory. Accordingly, the most abundant cells in the endometrium are endometrial stromal cells (EnSCs). These cells constitute a particular population with clonogenic activity that resembles properties of mesenchymal stem/stromal cells (MSCs). Thus, a significant role of stem cell-based dysfunction in formation of the initial endometrial lesions is suspected. There is increasing evidence that the role of epigenetic mechanisms and processes in endometriosis have been underestimated. The importance of excess estrogen exposure and P4 resistance in epigenetic homeostasis failure in the endometrial/endometriotic tissue are crucial. Epigenetic alterations regarding transcription factors of estrogen and P4 signaling pathways in MSCs are robust in endometriotic tissue. Thus, perspectives for the future may include MSCs and EnSCs as the targets of epigenetic therapies in the prevention and treatment of endometriosis. Here, we reviewed the current known changes in the epigenetic background of EnSCs and MSCs due to estrogen/P4 imbalances in the context of etiopathogenesis of endometriosis. Graphical Abstract.

Current Knowledge on Endometriosis Etiology: A Systematic Review of Literature

Objective

To review the mechanisms of endometriosis development, including those related to epigenetic mutations, cellular dysregulation, inflammatory processes, and oxidative stress.

Methods

A systematic literature review regarding current aspects of endometriosis etiology, genesis and development was performed using the PubMed, Google Scholar, and eLibrary databases. Keywords included endometriosis, etiology, development, genesis, associations and mechanisms. A multilingual search was performed.

Results

Several mechanisms underline the pathophysiological pathways for endometriosis development. Epigenetic mutations, external and internal influences, and chronic conditions have a significant impact on endometriosis development, survival and regulation. Several historically valid theories on endometriosis development were discussed, as well as updated findings.

Conclusion

Despite recent advances, fundamental problems in understanding endometriosis remain unresolved. The identification of unknown circulating epithelial progenitors or stem cells that are responsible for epithelial growth in both the endometrium and endometriotic foci seems to be the next step in solving these questions.

Dienogest regulates apoptosis, proliferation, and invasiveness of endometriotic cyst stromal cells via endoplasmic reticulum stress induction

Dienogest, a specific progesterone receptor agonist, is used in the treatment of endometriosis. However, it is still unclear as to the mechanisms of therapeutic effects on endometriosis. Our recent study showed that endometriosis may be the result of aberrant endoplasmic reticulum (ER) stress induction due to progesterone resistance. This finding suggests that the regulation of ER stress induction may play a key role in treatment of endometriosis. Therefore, the anti-endometriotic effects of dienogest may be mediated by regulation of ER stress. To test this hypothesis, we elucidate whether dienogest affects endometriotic stromal cell apoptosis, proliferation and invasiveness by modulating ER stress-induced CCAAT/enhancer-binding protein homologous protein (CHOP) expression. Specifically, PRKR-like ER kinase (PERK)/eukaryotic initiation factor 2α (eIF2α)/activating transcription factor 4 (ATF4), inositol-requiring kinase 1 (IRE1)/TNF receptor-associated factor 2 (TRAF2)/apoptosis signal-regulating kinase 1 (ASK1)/c-Jun N-terminal kinase (JNK) signaling, and downstream CHOP were evaluated to determine the involved ER stress-mediated regulation mechanism of CHOP expression. Our results show that progesterone treatment did not have any significant effects on ER stress, apoptosis, proliferation, and invasion in estrogen-treated endometriotic cyst stromal cells (ECSCs). However, dienogest treatment upregulated the induction of ER stress. It also led to increased apoptosis, and decreased proliferation and invasiveness. These dienogest-induced changes in apoptosis, proliferation and invasiveness were reversed by the ER stress inhibitor salubrinal. Furthermore, dienogest-induced ER stress increased CHOP expression through activation of both PERK/elf2α/ATF4 and IRE1/TRAF2/ASK1/JNK signaling. This upregulation was blocked by transfection with PERK and IRE1 siRNA, which decreased apoptosis and increased the proliferation and invasiveness of dienogest-treated ECSCs. Taken together, our findings indicate that dienogest enhances ER stress induction in endometriotic stromal cells, which affects apoptosis, proliferation and invasiveness via CHOP upregulation.

Steroid hormones regulate genome-wide epigenetic programming and gene transcription in human endometrial cells with marked aberrancies in endometriosis

Programmed cellular responses to cycling ovarian-derived steroid hormones are central to normal endometrial function. Abnormalities therein, as in the estrogen-dependent, progesterone-"resistant" disorder, endometriosis, predispose to infertility and poor pregnancy outcomes. The endometrial stromal fibroblast (eSF) is a master regulator of pregnancy success. However, the complex hormone-epigenome-transcriptome interplay in eSF by each individual steroid hormone, estradiol (E2) and/or progesterone (P4), under physiologic and pathophysiologic conditions, is poorly understood and was investigated herein. Genome-wide analysis in normal, early and late stage eutopic eSF revealed: i) In contrast to P4, E2 extensively affected the eSF DNA methylome and transcriptome. Importantly, E2 resulted in a more open versus closed chromatin, confirmed by histone modification analysis. Combined E2 with P4 affected a totally different landscape than E2 or P4 alone. ii) P4 responses were aberrant in early and late stage endometriosis, and mapping differentially methylated CpG sites with progesterone receptor targets from the literature revealed different but not decreased P4-targets, leading to question the P4-"resistant" phenotype in endometriosis. Interestingly, an aberrant E2-response was noted in eSF from endometriosis women; iii) Steroid hormones affected specific genomic contexts and locations, significantly enriching enhancers and intergenic regions and minimally involving proximal promoters and CpG islands, regardless of hormone type and eSF disease state. iv) In eSF from women with endometriosis, aberrant hormone-induced methylation signatures were mainly due to existing DNA methylation marks prior to hormone treatments and involved known endometriosis genes and pathways. v) Distinct DNA methylation and transcriptomic signatures revealed early and late stage endometriosis comprise unique disease subtypes. Taken together, the data herein, for the first time, provide significant insight into the hormone-epigenome-transcriptome interplay of each steroid hormone in normal eSF, and aberrant E2 response, distinct disease subtypes, and pre-existing epigenetic aberrancies in the setting of endometriosis, provide mechanistic insights into how endometriosis affects endometrial function/dysfunction.

The role of the endocannabinoid system in aetiopathogenesis of endometriosis: A potential therapeutic target

Endometriosis affects a large proportion of women during their reproductive years and is associated with pain and infertility, also affecting psychological wellbeing and quality of life. The pathogenesis of the disease remains unclear, although it is believed to be multifactorial. The endocannabinoid system (ECS) consists of a number of ligands, receptors and enzymes, and has gained interests in endometriosis research. This review aims to summarise all available evidence reporting the roles of the ECS in endometriosis. A literature search of the PubMed, EMBASE, and Web of Science electronic medical databases was performed. Original and review articles published in peer-reviewed journals were included. No publication date or publication status restrictions were imposed. Significant differences in the concentrations and expressions of the components of the ECS were reported in the eutopic and ectopic endometrium, and the systemic circulation of women with endometriosis compared to controls. Endometriosis appears to be associated with downregulation of CB1 receptors and upregulation of TRPV1 receptors. The role of CB1 and progesterone in anti-inflammatory action and the role of TRPV1 in inflammation and pain are of particular interests. Furthermore, the ECS has been reported to be involved in processes relevant to endometriosis, including cell migration, cell proliferation, apoptosis, inflammation, and interacts with sex steroid hormones. The ECS may play a role in disease establishment, progression, and pain in endometriosis. However, reports are based on studies of limited size and there are inconsistencies among the definition of their control groups. There are also conflicting reports regarding precise involvement of the ECS in endometriosis. Future research with larger numbers, strict inclusion and exclusion criteria and detailed clinical information is imperative.

The Pathogenesis of Endometriosis: Molecular and Cell Biology Insights

The etiopathogenesis of endometriosis is a multifactorial process resulting in a heterogeneous disease. Considering that endometriosis etiology and pathogenesis are still far from being fully elucidated, the current review aims to offer a comprehensive summary of the available evidence. We performed a narrative review synthesizing the findings of the English literature retrieved from computerized databases from inception to June 2019, using the Medical Subject Headings (MeSH) unique ID term “Endometriosis” (ID:D004715) with “Etiology” (ID:Q000209), “Immunology” (ID:Q000276), “Genetics” (ID:D005823) and “Epigenesis, Genetic” (ID:D044127). Endometriosis may origin from Müllerian or non-Müllerian stem cells including those from the endometrial basal layer, Müllerian remnants, bone marrow, or the peritoneum. The innate ability of endometrial stem cells to regenerate cyclically seems to play a key role, as well as the dysregulated hormonal pathways. The presence of such cells in the peritoneal cavity and what leads to the development of endometriosis is a complex process with a large number of interconnected factors, potentially both inherited and acquired. Genetic predisposition is complex and related to the combined action of several genes with limited influence. The epigenetic mechanisms control many of the processes involved in the immunologic, immunohistochemical, histological, and biological aberrations that characterize the eutopic and ectopic endometrium in affected patients. However, what triggers such alterations is not clear and may be both genetically and epigenetically inherited, or it may be acquired by the particular combination of several elements such as the persistent peritoneal menstrual reflux as well as exogenous factors. The heterogeneity of endometriosis and the different contexts in which it develops suggest that a single etiopathogenetic model is not sufficient to explain its complex pathobiology.

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.

Progesterone Receptor B (PGR-B) Is Partially Methylated in Eutopic Endometrium From Infertile Women With Endometriosis

Endometriosis is frequently related to infertility and little is known about the mechanisms underlying this association. Some studies point to an endometrial factor involved in this condition, which could compromise embryo implantation. Progesterone plays crucial role in endometrial receptivity by acting through progesterone receptor (PGR) isoforms PR-A and PR-B whose expression is epigenetically regulated by DNA methylation, in a specific promoter region for each isoform. Epigenetic changes in PGR-A and PGR-B may be related to progesterone resistance of endometriosis-related infertility. In order to better understand the mechanisms involved in endometrial receptivity, this case-control study aimed to compare the methylation pattern of PGR-A and PGR-B in eutopic endometrium from infertile women with and without endometriosis during the secretory phase. Endometrial biopsies from 19 patients (10 infertile women with endometriosis and 9 infertile controls) with regular cycles were performed during the secretory phase and were dated according to Noyes' criteria. The percentage of DNA methylation at PGR-A and PGR-B was carried out by high-resolution melting assay. The PGR-A gene showed 0% of DNA methylation (unmethylated) in both control and endometriosis groups. However, PGR-B gene showed a partially methylated pattern in majority of the patients (n = 7), with methylation percentage corresponding to 50%, while in the control group the percentage of methylation was 20% (hypomethylated; P = .04). The increased percentage of methylation at PGR-B may be related to reduced gene expression, which could compromise the endometrial receptivity in patients with endometriosis.

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

BACKGROUND

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

OBJECTIVE

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

RESULTS

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

CONCLUSION

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

Analysis of CARD10 and CARD11 somatic mutations in patients with ovarian endometriosis

Endometriosis is a complex and heterogeneous pre-malignant inflammatory disease harboring multiple gene mutations. Previous studies have suggested that caspase recruitment domain family member (CARD)10 and CARD11 mutations may exist in endometriosis. In the present study, a collection of endometriotic lesions and paired peripheral blood from 101 patients with ovarian endometriosis were obtained, and the entire coding sequences of the CARD10 and CARD11 genes were sequenced. Evolutionary conservation analysis and online prediction programs were applied to analyze the disease-causing potential of the identified mutations. A total of 4 novel somatic mutations were identified in 4 out of the 101 (4.0%) samples: 2 in-frame deletions in CARD10 (c.785_790delAGGAGA, p.K272_E273delKE; c.785_802delAGGAGAAGGAGAAGGAGA, p.K272_V277delKEPDNV) and 2 heterozygous missense mutations in CARD11 (c.49G>T, p.D17Y; c.160G>C, p.E54Q). The sample with CARD10 p.K272_E273delKE deletion was obtained from a 47-year-old patient who was also diagnosed with uterine leiomyoma, while the CARD10 p.K272_V277delKEPDNV-mutated sample was from a 43-year-old patient exhibiting a decreased blood eosinophil granulocyte ratio (0.3%) and an elevated serum creatine kinase level (314 U/l). The patient with the CARD11 p.D17Y mutation was 38 years old and exhibited an increased level of cancer antigen 125 (45.4 U/ml), while the patient with the CARD11 p.E54Q mutation was 46 years old and exhibited no other gynecological conditions. Evolutionary conservation analysis and online prediction programs suggested that these mutations may be disease-causing. In summary, 4 novel somatic mutations in the CARD10 and CARD11 genes were identified from amongst 101 cases of ovarian endometriosis for the first time, these mutations may serve active roles in the development of ovarian endometriosis.

Progestins for the Treatment of Endometriosis: An Update

Endometriosis is a gynecological condition that affects approximately 10% of women of reproductive age, including 25–40% of infertile women. Dysmenorrhea, dyspareunia and chronic pelvic pain are the most common symptoms. Currently available medical therapies for endometriosis do not cure the disease, but are directed at symptom relief, typically utilizing the hormone responsiveness of endometriotic tissue to induce lesion atrophy. Unfortunately, pain relapse after treatment suspension is a common event. Treatment with pharmacological therapies for endometriosis should be conceived in terms of years, thus agents that must be withdrawn after a few months due to poor tolerability or severe metabolic side effects do not greatly benefit women with symptomatic endometriosis. The characteristics of progestins render this class an ideal pharmacological choice for administration over extended periods. The present paper will review the rationale for using progestins and their mechanism of action in endometriosis. Thereafter, the results obtained by various progestins in the treatment of endometriosis will be evaluated (danazol, gestrinone, norethisterone acetate, desogestrel, cyproterone acetate, megestrol acetate, medroxyprogesterone acetate, and levonorgestrel). A progestin called dienogest, recently introduced for the treatment of endometriosis, will be given special focus, describing its mechanism of action and clinical results.

The Wnt/β-catenin signaling in endometriosis, the expression of total and active forms of β-catenin, total and inactive forms of glycogen synthase kinase-3β, WNT7a and DICKKOPF-1

OBJECTIVES

The cyclical changes in proliferation and differentiation of endometrial cells are regulated by estrogen and progesterone via modulating Wnt/β-catenin signaling. Imbalance in the expression of estrogen and progesterone receptors causes progesterone resistance in endometriosis patients. The aim of this study was to investigate the expression of some main components of Wnt/β-catenin signaling including WNT7a, DKK-1, β-catenin, and GSK-3β in eutopic endometrium and peritoneal endometriotic lesions of endometriosis patients compared to healthy endometrium in the mid-secretory phase of menstrual cycle.

STUDY DESIGN

This prospective study was performed, during a 12 months period from December 2015 to November 2016, on healthy women as the control group (n=14) and endometriosis patients (n=34). We used real-time polymerase chain reaction and Western blot techniques.

RESULTS

Protein and mRNA expression of DKK-1 were significantly down-regulated in both endometriotic lesions and eutopic endometrium of endometriosis group. We also demonstrated that the expression of non-phosphorylated β-catenin (active form) and phosphorylated GSK-3β (inactive form) were up-regulated in endometriosis patients. The mRNA levels of β-catenin, GSK-3β, and WNT7a, as well as the protein levels of total β-catenin, total GSK-3β, and WNT7a in endometriosis group, were not significantly different with those in control group. The patterns of mRNA and protein expression of all interested factors in the lesions were similar to those in the eutopic endometrium of same patients.

CONCLUSIONS

It seems that the aberrant activation of Wnt/β-catenin signaling in the secretory phase of the menstrual cycle in endometriosis has two essential elements: excessive inactivation of GSK-3β and suppression of the expression of Wnt signaling inhibitor DKK-1. Interventions in this signaling pathway may allow for the exploration of potential new targets for the control of development and progression of endometriosis.

Expression of PGR, HBEGF, ITGAV, ITGB3 and SPP1 genes in eutopic endometrium of infertile women with endometriosis during the implantation window: a pilot study

OBJECTIVE

Alterations in endometrial receptivity may be involved in the etiopathogenesis of endometriosis-related infertility. The literature has suggested that patients with endometriosis present progestin resistance, which could affect embryo implantation. We question the presence of alterations in the expression of the progesterone receptor gene (PGR) and the genes related to endometrium-embryo interaction regulated by progesterone. This pilot study compared the expression of PGR, HBEGF, ITGAV, ITGB3, and SPP1 genes in eutopic endometrium during the implantation window (IW) in infertile women with endometriosis with that observed in the endometrium of fertile and infertile controls.

METHODS

In this prospective case-control study, endometrial biopsies were performed during the IW in patients aged between 18 and 45 years old, with regular cycles and without endocrine/systemic dysfunctions, divided into endometriosis (END), infertile control (IC) and fertile control (FC) groups. Total RNA extraction, cDNA synthesis, and gene expression analysis by Real-Time PCR were performed. We assessed the size of the difference that our series was powered to detect.

RESULTS

From the 687 patients who underwent diagnostic videolaparoscopy or tubal ligation at the University Hospital, 130 were eligible. Of these, 32 had endometrial samples collected, with 17 confirmed in the IW. Fifteen samples (5 END, 5 IC and 5 FC) were analyzed. There was no significant difference in the expression of any studied gene. Our sample size allowed us to identify or discard large differences (two standard deviations) among the groups.

CONCLUSION

Endometriosis doesn't cause large changes in the endometrial expression of PGR, HBEGF, ITGAV, ITGB3 and SPP1 during the IW.

Endometrial receptivity in the eutopic endometrium of women with endometriosis: it is affected, and let me show you why

The endometrium maintains complex controls on proliferation and apoptosis as part of repetitive menstrual cycles that prepare the endometrium for the window of implantation and pregnancy. The reliance on inflammatory mechanisms for both implantation and menstruation creates the opportunity in the setting of endometriosis for establishment of chronic inflammation that is disruptive to endometrial receptivity, causing both infertility and abnormal bleeding. Clinically, there can be little doubt that the endometrium of women with endometriosis is less receptive to embryo implantation, and strong evidence exists to suggest that endometrial changes are associated with decreased cycle fecundity as a result of this disease. Here we provide unifying concepts regarding those changes and how they are coordinated to promote progesterone resistance and estrogen dominance through aberrant cell signaling pathways and reduced expression of key homeostatic proteins in eutopic endometrium of women with endometriosis.

Inside the granulosa transcriptome

The somatic component of follicular structure is a mixture of different cell types, represented by Granulosa cells (GCs) that are the paracrine regulators of the oocyte growth. GCs finely support this process by a continuous bidirectional talk with oocyte, which ensure oocyte quality and competence. Specific pathways are involved in the cross-talk and in both GCs and oocyte development. This review summarizes data from GCs gene expression analysis concerning both their physiological role and their interaction with oocyte. We also explore the CGs transcriptome modifications induced by controlled ovarian stimulation (COS) or pathological conditions and their impact in reproduction. The transcriptome analysis of GCs could be a powerful tool to improve our knowledge about the pathways involved in oocyte development. This approach, associated with new technologies as RNA-seq could allow the identifications of new noninvasive biological markers of oocyte quality to increase the efficiency of clinical IVF. Moreover, GCs expression analysis could be useful to shed light on new therapeutic targets by providing new options for the treatment of infertility.

Decreased Progesterone Receptor B/A Ratio in Endometrial Cells by Tumor Necrosis Factor-Alpha and Peritoneal Fluid from Patients with Endometriosis

PURPOSE

Progesterone resistance is thought to be a major factor that contributes to progression of endometriosis. However, it is not clear what causes progesterone resistance in endometriosis. This study aimed to assess whether cytokines or peritoneal fluid can affect progesterone receptor (PR) expression in endometrial cells and to verify whether PR expression is reduced in endometriosis.

MATERIALS AND METHODS

The PR-B/A ratio was measured via real-time polymerase chain reaction after in vitro culture, in which endometrial cells were treated with either tumor necrosis factor-alpha (TNF-α), interleukin-1 beta, or peritoneal fluid obtained from women with advanced-stage endometriosis. Immunohistochemistry was performed to compare PR-B expression between eutopic and ectopic endometrial tissues from women with and without advanced-stage endometriosis.

RESULTS

The PR-B/A ratio was significantly decreased by treatment with either TNF-α (p=0.011) or peritoneal fluid from women with advanced-stage endometriosis (p=0.027). Immunoreactivity of PR-B expression was significantly lower during the secretory phase than during the proliferative phase in endometrial tissues from control subjects (p<0.001). PR-B expression was significantly reduced in the eutopic endometrium (p=0.031) and ovarian endometrioma (p=0.036) from women with advanced-stage endometriosis compared with eutopic endometrium tissues from control subjects.

CONCLUSION

Progesterone resistance in endometriosis may be caused by proinflammatory conditions in the pelvic peritoneal microenvironment.

The Levonorgestrel Intrauterine System: Long-Term Contraception and Therapeutic Effects

The levonorgestrel intrauterine system (Mirena®) has been developed as a long-acting method of contraception. This medicated device, inserted into the uterus, delivers a small daily dose of a progestin, levonorgestrel, into the uterine cavity. It is one of the most effective methods of contraception and is approved in more than 100 countries for 5 years of use.

Pathogenesis of Endometriosis: Roles of Retinoids and Inflammatory Pathways

Endometriosis is a nonmalignant, but potentially metastatic, gynecological condition manifested by the extrauterine growth of inflammatory endometrial implants. Ten percent of reproductive-age women are affected and commonly suffer pelvic pain and/or infertility. The theories of endometriosis histogenesis remain controversial, but retrograde menstruation and metaplasia each infer mechanisms that explain the immune cell responses observed around the ectopic lesions. Recent findings from our laboratories and others suggest that retinoic acid metabolism and action are fundamentally flawed in endometriotic tissues and even generically in women with endometriosis. The focus of our ongoing research is to develop medical therapies as adjuvants or alternatives to the surgical excision of these lesions. On the basis of concepts put forward in this review, we predict that the pharmacological actions and anticipated low side-effect profiles of retinoid supplementation might provide a new treatment option for the long-term management of this chronic and debilitating gynecological disease.

Abundance and Localization of Progesterone Receptor Isoforms in Endometrium in Women With and Without Endometriosis and in Peritoneal and Ovarian Endometriotic Implants

BACKGROUND

Several studies suggest that resistance to progesterone may contribute to the pathophysiology of endometriosis. Progesterone mediates its biological activity via the 2 progesterone receptor (PR) isoforms (PR-A and PR-B). Effects of progesterone are determined by the PR-A:PR-B ratio such that a PR-B-dominant state promotes progesterone signaling, whereas a PR-A-dominant state decreases progesterone responsiveness. Our objective was to compare the abundance and cellular localization of the PR isoforms in endometrium and endometriotic lesions from women with and without peritoneal and ovarian endometriosis.

METHODS

This in vitro study was conducted in a tertiary care facility. Reproductive-age women with surgically diagnosed endometriosis (n = 18) and asymptomatic control individuals (n = 20) were prospectively recruited at the late proliferative and the early secretory phases. At laparoscopy, samples of eutopic endometrium, peritoneal and ovarian endometriosis, and disease-free peritoneum were obtained for subsequent immunohistochemical and immunoblot analysis of PR-B and total PR localization and PR-A and PR-B abundance, respectively.

RESULTS

The PR-A and PR-B were detected in eutopic endometrium and in peritoneal and ovarian endometriosis but not in disease-free peritoneum from patients with and without endometriosis. In peritoneal endometriosis, PR-A was the predominant isoform detected, whereas both receptors were detected in ovarian endometriosis and eutopic endometrium. In eutopic endometrium, levels of PR-A were significantly elevated in women with endometriosis compared with women without disease, regardless of menstrual phase. The PR-A levels were significantly elevated in ovarian endometriosis compared with peritoneal endometriosis.

CONCLUSIONS

Endometriotic lesions and eutopic endometrium from women with endometriosis are uniform in a PR-A-dominant state. The data suggest that menstrual efflux of a PR-A-dominant endometrial tissue into the peritoneal cavity may play a role in the pathophysiology of endometriosis.

Role of nuclear progesterone receptor isoforms in uterine pathophysiology

BACKGROUND

Progesterone is a key hormonal regulator of the female reproductive system. It plays a major role to prepare the uterus for implantation and in the establishment and maintenance of pregnancy. Actions of progesterone on the uterine tissues (endometrium, myometrium and cervix) are mediated by the combined effects of two progesterone receptor (PR) isoforms, designated PR-A and PR-B. Both receptors function primarily as ligand-activated transcription factors. Progesterone action on the uterine tissues is qualitatively and quantitatively determined by the relative levels and transcriptional activities of PR-A and PR-B. The transcriptional activity of the PR isoforms is affected by specific transcriptional coregulators and by PR post-translational modifications that affect gene promoter targeting. In this context, appropriate temporal and cell-specific expression and function of PR-A and PR-B are critical for normal uterine function.

METHODS

Relevant studies describing the role of PRs in uterine physiology and pathology (endometriosis, uterine leiomyoma, endometrial cancer, cervical cancer and recurrent pregnancy loss) were comprehensively searched using PubMed, Cochrane Library, Web of Science, and Google Scholar and critically reviewed.

RESULTS

Progesterone, acting through PR-A and PR-B, regulates the development and function of the endometrium and induces changes in cells essential for implantation and the establishment and maintenance of pregnancy. During pregnancy, progesterone via the PRs promotes myometrial relaxation and cervical closure. Withdrawal of PR-mediated progesterone signaling triggers menstruation and parturition. PR-mediated progesterone signaling is anti-mitogenic in endometrial epithelial cells, and as such, mitigates the tropic effects of estrogen on eutopic normal endometrium, and on ectopic implants in endometriosis. Similarly, ligand-activated PRs function as tumor suppressors in endometrial cancer cells through inhibition of key cellular signaling pathways required for growth. In contrast, progesterone via PR activation appears to increase leiomyoma growth. The exact role of PRs in cervical cancer is unclear. PRs regulate implantation and therefore aberrant PR function may be implicated in recurrent pregnancy loss (RPL). PRs likely regulate key immunogenic factors involved in RPL. However, the exact role of PRs in the pathophysiology of RPL and the use of progesterone for therapeutic benefit remains uncertain.

CONCLUSIONS

PRs are key mediators of progesterone action in uterine tissues and are essential for normal uterine function. Aberrant PR function (due to abnormal expression and/or function) is a major cause of uterine pathophysiology. Further investigation of the underlying mechanisms of PR isoform action in the uterus is required, as this knowledge will afford the opportunity to create progestin/PR-based therapeutics to treat various uterine pathologies.

Decreased expression of mucin-1 in endometriosis endometrium correlated with progesterone receptor B involved in infertility

PURPOSE

Mucin-1(MUC1), a type of glucoprotein, has various expression statuses on the endometrium at different menstrual phases. Normal expression of MCU1 is closely related to successful blastocyst implantation. MUC1 was synthesized and secreted by the glandular epithelium of the endometrium, which acts as a barrier to foreign bodies. The endometrium was able to recognize and accept the blastocyst implantation. Endometriosis has lower rates of successful implantation with in vitro fertilization and embryo transfer, which may involve the altered expression of MUC1 on eutopic endometrium. In vitro studies demonstrated that progesterone and its receptors affected MUC1 expression under different physiopathology conditions. Our study was designed to explore whether progesterone receptors alteration contributed to MUC1 varied expression on endometriosis endometrium.

METHODS

A total of 54 patients with different infertility reason were selected retrospectively from the First Affiliated Hospital of Soochow University and Kowloon Hospital, Suzhou, China. Endometrium samples were collected under operative procedures. The samples were assigned to two groups: endometriosis (n = 28) and oviduct block (control group, n = 26), on which we examined the expression of progesterone receptor B (PR-B) and MUC1, respectively, using immunohistochemistry and Western blotting.

RESULTS

Compared with the control group, the expression of MUC1 was significantly decreased in the mid-secretory phase of the menstrual cycle in endometriosis. There was relatively lower expression of MUC1 in different phases of the cycle in comparison with the control group. The varied expression of MUC1 was significantly related to PR-B variation in endometriosis endometrium (r = 0.763, P < 0.01).

CONCLUSION

Decreased expression of MUC1 may attribute to PR-B variation in the mid-secretory phase of endometriosis endometrium. It might be one of the factors resulted in infertility in endometriosis patients.

Influence of AKT on progesterone action in endometrial diseases

Progesterone plays an essential role in the maintenance of the endometrium; it prepares the endometrium for pregnancy, promotes decidualization, and inhibits estrogen-dependent proliferation. Progesterone function is often dysregulated in endometrial disease states. In addition, the PI3K/AKT signaling pathway is often overactive in endometrial pathologies and promotes the survival and proliferation of the diseased cells. Understanding how AKT influences progesterone action is critical in improving hormone-based therapies in endometrial pathologies. Here, we summarize recent studies investigating the crosstalk between the AKT pathway and progesterone receptor function in endometriosis and endometrial cancer.

Krüppel-like factor 9 deficiency in uterine endometrial cells promotes ectopic lesion establishment associated with activated notch and hedgehog signaling in a mouse model of endometriosis

Endometriosis, a steroid hormone-dependent disease characterized by aberrant activation of estrogen receptor signaling and progesterone resistance, remains intractable because of the complexity of the pathways underlying its manifestation. We previously showed that eutopic endometria of women with endometriosis exhibit lower expression of Krüppel-like factor 9 (KLF9), a progesterone receptor coregulator in the uterus, relative to that of women without disease. Here we examined whether loss of endometrial KLF9 expression causes ectopic lesion establishment using syngeneic wild-type (WT) mice as recipients of endometrial fragments from WT and Klf9 null donors. We found significantly higher incidence of ectopic lesions with Klf9 null than WT endometria 8 weeks after tissue injection into the intraperitoneal cavity. The increased incidence of lesion establishment with Klf9 null endometria was associated with a higher expression ratio of estrogen receptor 2 isoform relative to that of estrogen receptor 1 and attenuated progesterone receptor levels in endometriotic stromal cells. PCR array analyses of Notch and Hedgehog signaling components in ectopic lesions demonstrated up-regulated expression of select genes (Jag 2, Shh, Gli1, and Stil 1) in Klf9 null lesions relative to that in WT lesions. Immunohistochemical analyses showed increased levels of Notch intracellular domain and Sonic Hedgehog proteins in Klf9 null lesions relative to that in WT lesions, confirming pathway activation. WT recipients with Klf9 null lesions displayed lower systemic levels of TNFα and IL-6 and higher soluble TNF receptor 1 than corresponding recipients with WT lesions. Our results suggest that endometrial KLF9 deficiency promotes endometriotic lesion establishment by the coincident deregulation of Notch-, Hedgehog-, and steroid receptor-regulated pathways.

Progesterone action in endometrial cancer, endometriosis, uterine fibroids, and breast cancer

Progesterone receptor (PR) mediates the actions of the ovarian steroid progesterone, which together with estradiol regulates gonadotropin secretion, prepares the endometrium for implantation, maintains pregnancy, and differentiates breast tissue. Separation of estrogen and progesterone actions in hormone-responsive tissues remains a challenge. Pathologies of the uterus and breast, including endometrial cancer, endometriosis, uterine fibroids, and breast cancer, are highly associated with estrogen, considered to be the mitogenic factor. Emerging evidence supports distinct roles of progesterone and its influence on the pathogenesis of these diseases. Progesterone antagonizes estrogen-driven growth in the endometrium, and insufficient progesterone action strikingly increases the risk of endometrial cancer. In endometriosis, eutopic and ectopic tissues do not respond sufficiently to progesterone and are considered to be progesterone-resistant, which contributes to proliferation and survival. In uterine fibroids, progesterone promotes growth by increasing proliferation, cellular hypertrophy, and deposition of extracellular matrix. In normal mammary tissue and breast cancer, progesterone is pro-proliferative and carcinogenic. A key difference between these tissues that could explain the diverse effects of progesterone is the paracrine interactions of PR-expressing stroma and epithelium. Normal endometrium is a mucosa containing large quantities of distinct stromal cells with abundant PR, which influences epithelial cell proliferation and differentiation and protects against carcinogenic transformation. In contrast, the primary target cells of progesterone in the breast and fibroids are the mammary epithelial cells and the leiomyoma cells, which lack specifically organized stromal components with significant PR expression. This review provides a unifying perspective for the diverse effects of progesterone across human tissues and diseases.

Dienogest increases the progesterone receptor isoform B/A ratio in patients with ovarian endometriosis

BACKGROUND

The resistance of endometriotic tissue to progesterone can be explained by alterations in the distribution of progesterone receptor (PR) and estrogen receptor (ER) isoforms. The aims of this study were to examine the expressions of PR-A, PR-B, ERα and ERβ in endometrioma and assess whether these expressions are affected by dienogest or leuprolide acetate (LA) treatment.

METHODS

We enrolled 60 females, including 43 patients with endometriosis (14 who received no medical treatment, 13 who received dienogest and 16 who received LA before undergoing laparoscopic surgery) and 17 patients with leiomyoma. The expression levels of PR and ER isoforms in eutopic and ectopic endometrium were assayed with quantitative real-time PCR, and confirmed with immunohistochemistry.

RESULTS

A decreased PR-B/PR-A ratio and an increased ERβ/ERα ratio were demonstrated in ectopic endometrium derived from females with endometriosis compared with the ratios observed in eutopic endometrium obtained from females without endometriosis. Although LA treatment did not affect the PR-B/PR-A and ERβ/ERα ratios, dienogest treatment increased the PR-B/PR-A ratio and decreased the ERβ/ERα ratio in patients with endometriomas.

CONCLUSIONS

Dienogest may improve progesterone resistance in endometriotic tissue by increasing the relative expressions of PR-B and PR-A, and decreasing the relative expressions of ERβ and ERα.

TYK2 rs34536443 polymorphism is associated with a decreased susceptibility to endometriosis-related infertility

INTRODUCTION

Tyrosine kinase 2 gene (TYK2) is part of the janus kinase (JAK) that binds to the type I interferon-α receptor (IFNAR) on the cell surface of IFN-producing cells, and have crucial importance in the etiology of autoimmune and inflammatory diseases. Many polymorphisms of the TYK2 gene have been identified, and recently, a number of case-control studies were conducted to investigate the association of these polymorphisms with autoimmune and inflammatory diseases, with conflicting results. Based on these observations, we hypothesized that the TYK2 polymorphisms (rs34536443, rs2304256, rs280523, rs12720270 and rs12720356) might be involved in the pathogenesis of endometriosis and/or infertility.

METHODS

Genetic association study comprising 275 infertile women with endometriosis, 92 women with idiopathic infertility and 307 fertile women as controls. TYK2 polymorphisms were identified by TaqMan PCR. Genotype distribution, allele frequency and haplotype analysis of the TYK2 polymorphisms were performed. A p-value <0.05 was considered significant.

RESULTS

Single-marker analysis revealed that TYK2 rs34536443 was significantly associated with protection against endometriosis-related infertility, especially in moderate/severe disease (p = 0.002; OR = 0.24, 95% IC = 0.09-0.62). No difference was found considering the infertile group without endometriosis. No associations were found considering rs2304256, rs280523, rs12720270 and rs12720356 either for endometriosis-related infertility group or idiopathic infertility group. Haplotype analysis of five TYK2 polymorphisms identified a haplotype "CTATG" associated with protection against endometriosis-related infertility, especially in moderate/severe disease (p = 0.027).

CONCLUSION

This is the first study to report an association between TYK2 polymorphisms and endometriosis and/or infertility. These findings require replication in other populations but suggest the TYK2 rs34536443 polymorphisms and "CTATG" haplotype can be associated with a decreased susceptibility to endometriosis-related infertility in Brazilian women.

Progesterone-dependent regulation of endometrial cannabinoid receptor type 1 (CB1-R) expression is disrupted in women with endometriosis and in isolated stromal cells exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

OBJECTIVE

To examine the differentiation-related expression of cannabinoid receptor type 1 (CB1-R) messenger RNA (mRNA) and protein in endometrial tissue obtained from women with and without endometriosis and to determine the impact of acute 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure on CB1-R gene expression in isolated endometrial stromal cells.

DESIGN

Laboratory-based study.

SETTING

University-affiliated medical center.

PATIENT(S)

Women with and without endometriosis undergoing volunteer endometrial biopsies after informed consent.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Analysis of in vivo CB1-R mRNA and protein expression in human endometrial tissues and mRNA expression in isolated stromal cells after exposure to TCDD or a progesterone receptor antagonist (onapristone).

RESULT(S)

Expression of CB1-R mRNA and protein was highest during the progesterone-dominated secretory phase in control samples, but expression was minimal in the endometrial tissues acquired from women with endometriosis, regardless of the cycle phase. Although progesterone was found to induce CB1-R mRNA expression in endometrial stromal cells from control donors, steroid-induced expression of this gene was inhibited by cotreatment with either TCDD or onapristone.

CONCLUSION(S)

Our studies reveal a role for the anti-inflammatory actions of progesterone in regulating endometrial cannabinoid signaling, which is disrupted in women with endometriosis. We demonstrate for the first time that acute TCDD exposure disrupts cannabinoid signaling in the human endometrium.

The Role of Endocrine Disruptors in the Epigenetics of Reproductive Disease and Dysfunction: Potential Relevance to Humans

In a murine model, we have linked early life toxicant exposure to reduced uterine sensitivity to progesterone, a phenotype we had previously associated with inflammation in endometriosis patients. Subsequent studies revealed that developmental toxicant exposure not only reduces fertility in male and female mice but also negatively impacts pregnancy leading to spontaneous preterm birth (PTB). An epigenetic alteration of the progesterone receptor gene correlated with reduced fertility and adverse pregnancy outcomes and persisted in multiple generations of mice in the absence of an additional toxicant exposure. Gene-environment interactions in women may explain why some patients "at risk" for PTB deliver at term while others without known risks deliver early. Our model provides a unique system to unravel the interactive influences of inflammation and reduced progesterone responsiveness on PTB and suggests that therapy needs to begin prior to pregnancy (and involve both partners) rather than once the inflammatory cascade has been initiated.

Treatment of endometriosis in different ethnic populations: a meta-analysis of two clinical trials

Approaches to the treatment of endometriosis vary worldwide, but studies comparing endometriosis medications in different ethnic groups are rare. A systematic literature search identified two studies directly comparing dienogest (DNG) versus gonadotropin-releasing hormone (GnRH) analogues in European and Japanese populations. Meta-analysis of visual analogue scale scores revealed no heterogeneity in response between the trials, indicating equivalent efficacy of DNG and GnRH analogues for endometriosis-related pain across populations. DNG was significantly superior to GnRH analogues for bone mineral density change in both trials, but significant heterogeneity between the studies may indicate ethnic differences in physiology.

Krüppel-like factor 9 and progesterone receptor coregulation of decidualizing endometrial stromal cells: implications for the pathogenesis of endometriosis

CONTEXT

Endometriosis is characterized by progesterone resistance and associated with infertility. Krüppel-like factor 9 (KLF9) is a progesterone receptor (PGR)-interacting protein, and mice null for Klf9 are subfertile. Whether loss of KLF9 expression contributes to progesterone resistance of eutopic endometrium of women with endometriosis is unknown.

OBJECTIVE

The aims were to investigate 1) KLF9 expression in eutopic endometrium of women with and without endometriosis, 2) effects of attenuated KLF9 expression on WNT-signaling component expression and on WNT inhibitor Dickkopf-1 promoter activity in human endometrial stromal cells (HESC), and 3) PGR and KLF9 coregulation of the stromal transcriptome network.

METHODS

Transcript levels of KLF9, PGR, and WNT signaling components were measured in eutopic endometrium of women with and without endometriosis. Transcript and protein levels of WNT signaling components in HESC transfected with KLF9 and/or PGR small interfering RNA were analyzed by quantitative RT-PCR and Western blot. KLF9 and PGR coregulation of Dickkopf-1 promoter activity was evaluated using human Dickkopf-1-luciferase promoter/reporter constructs and by chromatin immunoprecipitation. KLF9 and PGR signaling networks were analyzed by gene expression array profiling.

RESULTS

Eutopic endometrium from women with endometriosis had reduced expression of KLF9 mRNA together with those of PGR-B, WNT4, WNT2, and DKK1. KLF9 and PGR were recruited to the DKK1 promoter and modified each other's transactivity. In HESC, KLF9 and PGR coregulated components of the WNT, cytokine, and IGF gene networks that are implicated in endometriosis and infertility.

CONCLUSION

Loss of KLF9 coregulation of endometrial stromal PGR-responsive gene networks may underlie progesterone resistance in endometriosis.

Role of estrogen receptor-β in endometriosis

Endometriosis is an estrogen-dependent disease. The biologically active estrogen, estradiol, aggravates the pathological processes (e.g., inflammation and growth) and the symptoms (e.g., pain) associated with endometriosis. Abundant quantities of estradiol are available for endometriotic tissue via several mechanisms including local aromatase expression. The question remains, then, what mediates estradiol action. Because estrogen receptor (ER)β levels in endometriosis are >100 times higher than those in endometrial tissue, this review focuses on this nuclear receptor. Deficient methylation of the ERβ promoter results in pathological overexpression of ERβ in endometriotic stromal cells. High levels of ERβ suppress ERα expression. A severely high ERβ-to-ERα ratio in endometriotic stromal cells is associated with suppressed progesterone receptor and increased cyclo-oxygenase-2 levels contributing to progesterone resistance and inflammation. ERβ-selective estradiol antagonists may serve as novel therapeutics of endometriosis in the future.

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.

Is abnormal eutopic endometrium the cause of endometriosis? The role of eutopic endometrium in pathogenesis of endometriosis

Endometriosis (EM) is one of the most common diseases which severely affect the health and reproductive function of women of childbearing age. There are fundamental abnormal changes within the eutopic endometrium of women with endometriosis compared to normal endometrium of women without endometriosis. Eutopic endometrium shows enhanced ability of proliferation, implantation and angiogenesis, and greater probability of escaping the unfavorable conditions of the ectopic environment. Therefore, the character of eutopic endometrium determines the fate of the backward-flowing endometrial tissue – to live or to die. The abnormal endometrial tissue in EM patients flows backward to the pelvic cavity, completing a 3-step procedure of pathogenesis (attachment-aggression-angiogenesis), and ultimately develops into EM. Abnormal eutopic endometrium may also play important roles in endometriosis-associated infertility. This recognition regarding the pathogenesis of endometriosis ultimately will help to discover new methods for diagnosis and treatment. Endometrial markers for micro-invasive diagnosis and direct treatment of eutopic endometrium as the origin of the disease should be further investigated.

Bisphenol-A exposure alters endometrial progesterone receptor expression in the nonhuman primate

OBJECTIVE

To evaluate the effect of bisphenol-A (BPA), a xenoestrogen endocrine disruptor, on endometrial P receptor (PR) expression in nonhuman primates and human cells.

DESIGN

Controlled trial in primates.

SETTING

University.

ANIMAL(S)

African green monkeys.

INTERVENTION(S)

After oophorectomy, BPA (50 μg/kg/d), E(2), both, or vehicle control were administered. Estradiol and BPA were used in Ishikawa cells.

MAIN OUTCOME MEASURE(S)

Progesterone receptor expression using immunohistochemistry and quantitative polymerase chain reaction.

RESULT(S)

Progesterone receptor expression was increased in E(2)-treated primates compared with controls. Exposure to the combination of E(2) and BPA resulted in decreased PR expression compared with E(2) exposure alone. In Ishikawa cells treated with E(2), PR expression increased 5.1-fold; however, when Ishikawa cells were simultaneously treated with E(2) and BPA, PR expression was decreased to 0.6-fold that of cells treated with E(2) alone.

CONCLUSION(S)

Bisphenol-A alone functions as a weak estrogen. However, when administered with E(2), BPA diminishes E(2)-induced PR expression. The estrogen-like effect of BPA reported in exposed humans may be mediated by PR blockade and a resultant decrease in the estrogen inhibition normally imparted by P. Diminished PR expression may underlie previous reports linking BPA exposure to endometrial dysfunction in humans.