Progesterone receptor isoform A but not B is expressed in endometriosis

Altered gene expression profile in vaginal polypoid endometriosis resembles peritoneal endometriosis and is consistent with increased local estrogen production

BACKGROUND

In a university hospital setting, a 25-year-old woman presented with large vaginal and cervical polyps. Past medical history was significant for stage IV endometriosis. Polypectomy was performed and the polyps were histologically consistent with endometriosis. Gene expression was compared with control vaginal tissue to assess if the altered gene expression profile was similar to peritoneal endometriosis.

METHODS AND RESULTS

Using quantitative reverse transcription, real-time PCR, estrogen receptor-β expression was found to be upregulated 10-fold while estrogen receptor-α expression was downregulated 5-fold in the vaginal polyp relative to control vaginal tissue. The estrogen-synthesizing enzyme aromatase was upregulated 8-fold and 3β-hydroxysteroid dehydrogenase was upregulated 400-fold in the polyp. Immunohistochemical staining revealed altered cell type localization for progesterone receptor in the polyp and increased cell proliferation in polyp stromal cells relative to control.

CONCLUSIONS

Increased proliferation in the vaginal polypoid endometriotic tissue may be due to increased local estrogen production. The altered gene expression profile was very similar to the altered gene expression profile seen in peritoneal endometriosis.

The role of the Hoxa10/HOXA10 gene in the etiology of endometriosis and its related infertility: a review

PURPOSE

endometriosis and its associated infertility have been the object of continuous research for over a century. To understand the molecular mechanisms underlying the disease, it has become necessary to determine the aspects of its etiology that are not explained by the retrograde menstruation theory. This could in turn elucidate how various clinical and surgical treatments might affect the evolution and remission of the disease.

METHODS

this review is focused on the most recent clinical and laboratory findings regarding the association of HOXA10 with endometriosis and infertility.

RESULT

the homebox (Hox/HOX) proteins are highly conserved transcription factors that determine segmental body identities in multiple species, including humans. Hoxa10/HOXA10 is directly involved in the embryogenesis of the uterus and embryo implantation via regulation of downstream genes. Cyclical endometrial expression of Hoxa10/HOXA10, with a peak of expression occurring during the window of implantation, is observed in the adult in response to estrogen and progesterone. Women with endometriosis do not demonstrate the expected mid-luteal rise of HOXA10 expression, which might partially explain the infertility observed in many of these patients. Recent studies also demonstrated HOXA10 expression in endometriotic foci outside the Müllerian tract.

CONCLUSIONS

multiple lines of evidence suggest that the actions of the homeobox A10 (Hoxa10/HOXA10) gene could account for some aspects of endometriosis.

Altered retinoid uptake and action contributes to cell survival in endometriosis

CONTEXT

Retinoic acid (RA) controls multiple biological processes via exerting opposing effects on cell survival. Retinol uptake into cells is controlled by stimulated by RA 6 (STRA6). RA is then produced from retinol in the cytosol. Partitioning of RA between the nuclear receptors RA receptor α and peroxisome-proliferator-activated receptor β/δ is regulated by cytosol-to-nuclear shuttling proteins cellular RA binding protein 2 (CRABP2) and fatty acid binding protein 5 (FABP5), which induce apoptosis or enhance survival, respectively. The roles of these mechanisms in endometrium or endometriosis remain unknown.

OBJECTIVE

The aim was to determine the regulation of retinoid uptake and RA action in primary stromal cells from endometrium (n = 10) or endometriosis (n = 10).

RESULTS

Progesterone receptor was necessary for high STRA6 and CRABP2 expression in endometrial stromal cells. STRA6, which was responsible for labeled retinoid uptake, was strikingly lower in endometriotic cells compared to endometrial cells. CRABP2 knockdown in endometrial cells increased survival, and FABP5 knockdown in endometriotic cells decreased survival without altering the expression of downstream nuclear retinoic acid receptor α and peroxisome-proliferator-activated receptor β/δ.

CONCLUSIONS

In endometrial stromal cells, progesterone receptor up-regulates expression of STRA6 and CRABP2, which control retinol uptake and growth-suppressor actions of RA. In endometriotic stromal cells, decreased expression of these genes leads to decreased retinol uptake and dominant FABP5-mediated prosurvival activity.

The endometrial response to chorionic gonadotropin is blunted in a baboon model of endometriosis

Endometriosis-associated infertility has a multifactorial etiology. We tested the hypothesis that the endometrial response to the early embryonic signal, human chorionic gonadotropin (hCG), alters over time in a nonhuman primate model of endometriosis. Animals with experimental or spontaneous endometriosis were treated with hCG (30 IU/d), from d 6 after ovulation for 5 d, via an oviductal cannula. Microarray analysis of endometrial transcripts from baboons treated with hCG at 3 and 6 months of disease (n=6) identified 22 and 165 genes, respectively, whose levels differed more than 2-fold compared with disease-free (DF) animals treated with hCG (P<0.01). Quantitative RT-PCR confirmed abnormal responses of known hCG-regulated genes. APOA1, SFRP4, and PAPPA, which are normally down-regulated by hCG were up-regulated by hCG in animals with endometriosis. In contrast, the ability of hCG to induce SERPINA3 was lost. Immunohistochemistry demonstrated dysregulation of C3 and superoxide dismutase 2 proteins. We demonstrate that this abnormal response to hCG persists for up to 15 months after disease induction and that the nature of the abnormal response changes as the disease progresses. Immunohistochemistry showed that this aberrant gene expression was not a consequence of altered LH/choriogonadotropin receptor distribution in the endometrium of animals with endometriosis. We have shown that endometriosis induces complex changes in the response of eutopic endometrium to hCG, which may prevent the acquisition of the full endometrial molecular repertoire necessary for decidualization and tolerance of the fetal allograft. This may in part explain endometriosis-associated implantation failure.

Basal and steroid hormone-regulated expression of CXCR4 in human endometrium and endometriosis

Endometriosis is associated with activation of local and systemic inflammatory mechanisms, including increased levels of chemokines and other proinflammatory cytokines. We have previously reported increased gene expression of chemokine receptor 4 (CXCR4), the receptor for CXCL12, in lesions of the rat model of endometriosis. The CXCR4-CXCL12 axis has been shown to have both immune (HIV infection, lymphocyte chemotaxis) and nonimmune functions, including roles in tissue repair, angiogenesis, invasion, and migration. There is evidence indicating that these mechanisms are also at play in endometriosis; therefore, we hypothesized that activation of the CXCR4-CXCL12 axis could be responsible, at least in part, for the survival and establishment of endometrial cells ectopically. Immunohistochemistry (IHC) showed that CXCR4 protein levels were significantly higher in endometriotic lesions compared to the endometrium of controls. Next, we determined basal gene and protein expression of CXCR4 and CXCL12 and regulation by estradiol (E2) and/or progesterone (P4) in endometrial cell lines using quantitative polymerase chain reaction (qPCR), and Western blots. Basal CXCR4 gene expression levels were higher in epithelial versus stromal cells; conversely, CXCL12 was expressed at higher levels in stromal vs epithelial cells. CXCR4 gene expression was significantly downregulated by ovarian steroid hormones in endometrial epithelial. These data suggest that steroid modulation of CXCR4 is defective in endometriosis, although the specific mechanism involved remains to be elucidated. These findings have implications for future therapeutic strategies specifically targeting the inflammatory component in endometriosis.

Unique transcriptome, pathways, and networks in the human endometrial fibroblast response to progesterone in endometriosis

Eutopic endometrium in endometriosis has molecular evidence of resistance to progesterone (P(4)) and activation of the PKA pathway in the stromal compartment. To investigate global and temporal responses of eutopic endometrium to P(4), we compared early (6-h), intermediate (48-h), and late (14-Day) transcriptomes, signaling pathways, and networks of human endometrial stromal fibroblasts (hESF) from women with endometriosis (hESF(endo)) with hESF from women without endometriosis (hESF(nonendo)). Endometrial biopsy samples were obtained from subjects with and without mild peritoneal endometriosis (n = 4 per group), and hESF were isolated and treated with P(4) (1 μM) plus estradiol (E(2)) (10 nM), E(2) alone (10 nM), or vehicle for up to 14 days. Total RNA was subjected to microarray analysis using a Gene 1.0 ST (Affymetrix) platform and analyzed by using bioinformatic algorithms, and data were validated by quantitative real-time PCR and ELISA. Results revealed unique kinetic expression of specific genes and unique pathways, distinct biological and molecular processes, and signaling pathways and networks during the early, intermediate, and late responses to P(4) in both hESF(nonendo) and hESF(endo), although a blunted response to P(4) was observed in the latter. The normal response of hESF to P(4) involves a tightly regulated kinetic cascade involving key components in the P(4) receptor and MAPK signaling pathways that results in inhibition of E(2)-mediated proliferation and eventual differentiation to the decidual phenotype, but this was not established in the hESF(endo) early response to P(4). The abnormal response of this cell type to P(4) may contribute to compromised embryonic implantation and infertility in women with endometriosis.

Subfertility linked to combined luteal insufficiency and uterine progesterone resistance

Early pregnancy loss is common and can be caused by a range of factors. The Brown Norway (BN) rat exhibits reproductive dysfunction characterized by small litter size and pregnancy failure and represents a model for investigating early pregnancy loss. In this study, we investigated the establishment of pregnancy in the BN rat and gained insight into mechanisms causing its subfertility. Early stages of BN uteroplacental organization are unique. The BN primordial placenta is restricted in its development and correlates with limited BN uterine decidual development. BN uterine decidua was shown to be both structurally and functionally distinct and correlated with decreased circulating progesterone (P4) levels. Ovarian anomalies were also apparent in BN rats and included decreased ovulation rates and decreased transcript levels for some steroidogenic enzymes. Attempts to rescue the BN uterine decidual phenotype with steroid hormone therapy were ineffective. BN uteri were shown to exhibit reduced responsiveness to P4 but not to 17beta-estradiol. P4 resistance was associated with decreased transcript levels for the P4 receptor (Pgr), a P4 receptor chaperone (Fkbp4), and P4 receptor coactivators (Ncoa1 and Ncoa2). In summary, the BN rat exhibits luteal insufficiency and uterine P4 resistance, which profoundly affects its ability to reproduce.

Functional differentiation of uterine stromal cells involves cross-regulation between bone morphogenetic protein 2 and Kruppel-like factor (KLF) family members KLF9 and KLF13

The inability of the uterine epithelium to enter a state of receptivity for the embryo to implant is a significant underlying cause of early pregnancy loss. We previously showed that mice null for the progesterone receptor (PGR)-interacting protein Krüppel-like factor (KLF) 9 are subfertile and exhibit reduced uterine progesterone sensitivity. KLF9 expression is high in predecidual stroma, undetectable in decidua, and enhanced in uteri of mice with conditional ablation of bone morphogenetic protein 2 (BMP2). Given the individual importance of KLF9 and BMP2 for implantation success, we hypothesized that the establishment of uterine receptivity involves KLF9 and BMP2 functional cross-regulation. To address this, we used early pregnant wild-type and Klf9 null mice and KLF9 small interfering RNA-transfected human endometrial stromal cells (HESCs) induced to differentiate under standard conditions. Loss of KLF9 in mice and HESCs enhanced BMP2 expression, whereas recombinant BMP2 treatment of HESCs attenuated KLF9 mRNA levels. IGFBP1 and KLF9-related KLF13 expression were positively associated with BMP2 and inversely associated with KLF9. Prolonged, but not short-term, knockdown of KLF9 in HESCs reduced IGFBP1 expression. Mouse uterine Igfbp1 expression was similarly reduced with Klf9 ablation. PGR-A and PGR-B expression were positively associated with KLF9 in predecidual HESCs but not decidualizing HESCs. KLF13 knockdown attenuated BMP2 and PGR-B and abrogated BMP2-mediated inhibition of KLF9 expression. Results support cross-regulation among BMP2, KLF9, and KLF13 to maintain progesterone sensitivity in stromal cells undergoing differentiation and suggest that loss of this regulatory network compromises establishment of uterine receptivity and implantation success.

Experimental endometriosis in immunocompromised mice after adoptive transfer of human leukocytes

OBJECTIVE

To develop a chimeric human/mouse model of experimental endometriosis for the examination of the role of human immune cells in this disease.

DESIGN

Laboratory-based study.

SETTING

University-affiliated medical center.

PATIENT(S)

Healthy women undergoing volunteer endometrial biopsies and blood donation.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

In vivo analysis of the impact of the adoptive transfer of human immune cells into immunocompromised mice receiving autologous human endometrium.

RESULT(S)

Similar to our previous data using nude mice, human endometrial tissue fragments injected intraperitoneally into rag2gamma(c) mice readily established experimental disease. However, in this study, we found a statistically significant reduction in the severity of peritoneal disease in rag2gamma(c) mice which also received adoptive transfer of human immune cells compared with mice that did not receive immune cells. Our studies indicate that human immune cells readily track into the ectopic lesions established in mice.

CONCLUSION(S)

The ability of immune cells from disease-free women to limit intraperitoneal disease in mice suggests that a robust immune system is protective against the development of endometriosis.

Uterine disorders and pregnancy complications: insights from mouse models

Much of our knowledge of human uterine physiology and pathology has been extrapolated from the study of diverse animal models, as there is no ideal system for studying human uterine biology in vitro. Although it remains debatable whether mouse models are the most suitable system for investigating human uterine function(s), gene-manipulated mice are considered by many the most useful tool for mechanistic analysis, and numerous studies have identified many similarities in female reproduction between the two species. This Review brings together information from studies using animal models, in particular mouse models, that shed light on normal and pathologic aspects of uterine biology and pregnancy complications.

17Beta-hydroxysteroid dehydrogenase-2 deficiency and progesterone resistance in endometriosis

Estradiol (E2) stimulates the growth and inflammation in the ectopic endometriotic tissue that commonly resides on the pelvic organs. Several clinical and laboratory-based observations are indicative of resistance to progesterone action in endometriosis. The molecular basis of progesterone resistance in endometriosis may be related to an overall reduction in the levels of progesterone receptor (PR). In normal endometrium, progesterone acts via PR on stromal cells to induce secretion of paracrine factor(s) that in turn stimulate neighboring epithelial cells to express the enzyme 17beta-hydroxysteroid dehydrogenase type 2 (HSD17B2). HSD17B2 is an extremely efficient enzyme and rapidly metabolizes the biologically potent estrogen E2 to weakly estrogenic estrone. In endometriotic tissue, progesterone is incapable of inducing epithelial HSD17B2 expression due to a defect in stromal cells. The inability of endometriotic stromal cells to produce progesterone-induced paracrine factors that stimulate HSD17B2 may be due to the very low levels of PR observed in vivo in endometriotic tissue. The end result is deficient metabolism of E2 in endometriosis giving rise to high local concentrations of this mitogen. The molecular details of this physiological paracrine interaction between the stroma and epithelium in normal endometrium and its lack thereof in endometriosis are discussed.

Endometrial decidualization: of mice and men

In murine and human pregnancies, embryos implant by attaching to the luminal epithelium and invading into the stroma of the endometrium. Under the influence of the steroid hormones estrogen and progesterone, the stromal cells surrounding the implanting embryo undergo a remarkable transformation event. This process, known as decidualization, is an essential prerequisite for implantation. It comprises morphogenetic, biochemical, and vascular changes driven by the estrogen and progesterone receptors. The development of mutant mouse models lacking these receptors has firmly established the necessity of steroid signaling for decidualization. Genomic profiling of mouse and human endometrium has uncovered a complex yet highly conserved network of steroid-regulated genes that supports decidualization. To advance our understanding of the mechanisms regulating implantation and better address the clinical challenges of infertility and endometrial diseases such as endometriosis, it is important to integrate the information gained from the mouse and human models.

Estrogen receptor-beta, estrogen receptor-alpha, and progesterone resistance in endometriosis

Loss of progesterone signaling in the endometrium may be a causal factor in the development of endometriosis, and progesterone resistance is commonly observed in women with this disease. In endometriotic stromal cells, the levels of progesterone receptor (PR), particularly the PR-B isoform, are significantly decreased, leading to a loss of paracrine signaling. PR deficiency likely underlies the development of progesterone resistance in women with endometriosis who no longer respond to progestin therapy. Here we review the complex epigenetic and transcriptional mechanisms leading to PR deficiency. The initial event may involve deficient methylation of the estrogen receptor (ER)beta promoter resulting in pathologic overexpression of ERbeta in endometriotic stromal cells. We speculate that alterations in the relative levels of ERbeta and ERalpha in endometrial tissue dictate E2-regulated PR expression, such that a decreased ERalpha-tauomicron-ERbeta ratio may result in suppression of PR. In this review, we propose a molecular model that may be responsible for changes in ERbeta and ERalpha leading to PR loss and progesterone resistance in endometriosis.

Connexin expression pattern in the endometrium of baboons is influenced by hormonal changes and the presence of endometriotic lesions

Experimentally induced endometriosis in baboons serves as an elegant model to discriminate between endometrial genes which are primarily associated with normal endometrial function and those that are changed by the presence of endometriotic lesions. Since connexin genes are characteristic of the hormonally regulated differentiation of the endometrium, we have examined connexin expression in baboon endometrium to delineate if they are altered in response to the presence of endometriotic lesions. Connexin expression in the endometrium of cycling baboons is similar to that of the human endometrium with Connexin(Cx)43 being primarily seen in the stromal compartment and Cx26 and Cx32 being present predominantly in the epithelium. Although Cx32 is up-regulated during the secretory phase, Cx26 and Cx43 are down-regulated. In the baboon model of induced endometriosis a change in connexin pattern was evident in the presence of endometriotic lesions. In the secretory phase, Cx26 and Cx32 are no longer present in the epithelium but Cx26 is now observed primarily in the stromal cells. Infusion of chorionic gonadotrophin in a manner that mimics blastocyst transit in utero failed to rescue the aberrant stromal expression of Cx26 that is associated with the presence of endometriotic lesions suggesting an impairment of the implantation process. The altered connexin pattern coupled with a loss of the channel protein in the epithelium and a gain of Cx26 in the stromal compartment suggests that the presence of lesions changes the uterine environment and thereby the differentiation programme. This aberrant expression of connexins may be an additional factor that contributes to endometriosis-associated infertility.

The progesterone receptor coactivator Hic-5 is involved in the pathophysiology of endometriosis

Endometriosis is an estrogen-dependent disorder primarily associated with pelvic pain and infertility in up to 10% of women of reproductive age. Recent studies suggest that resistance to progesterone action may contribute to the development and pathophysiology of this disorder. In this study we examined the in vivo and in vitro expression and function of one progesterone receptor (PR) coactivator, Hic-5, in human endometrium and endometrial stromal fibroblasts (hESFs) from 29 women with and 30 (control) women without endometriosis. Hic-5 was highly expressed in stromal, but not epithelial, cells in women without endometriosis, in a cycle-dependent manner. In contrast, Hic-5 expression was not regulated during the menstrual cycle in hESFs from women with endometriosis and was significantly reduced in hESFs from women with vs. without disease. Hic-5 mRNA expression throughout the cycle in endometrium from control women, but not those with endometriosis, correlated with expression of PR. Hic-5 mRNA in hESFs was significantly up-regulated in control but not endometriosis hESFs after treatment in vitro with 8-bromoadenosine-cAMP for 96 h but only modestly after 14 d of progesterone treatment. Hic-5 silencing did not influence cAMP-regulated gene expression but affected genes regulated solely by progesterone (e.g. DKK1 and calcitonin). Together the data suggest that the proposed progesterone resistance in endometrium from women with endometriosis derives, in part, from impaired expression of the PR coactivator, Hic-5, in endometrial tissue and cultured endometrial stromal fibroblasts.

The non-human primate model of endometriosis: research and implications for fecundity

The development of an animal model of endometriosis is crucial for the investigation of disease pathogenesis and therapeutic intervention. These models will enhance our ability to evaluate the causes for the subfertility associated with disease and provide a first-line validation of treatment modulators. Currently rodents and non-human primate models have been developed, but each model has their limitations. The aim of this manuscript is to summarize the current findings and theories on the development of endometriosis and disease progression and the effectiveness of therapeutic targets using the experimental induced model of endometriosis in the baboon (Papio anubis).

Reduced expression of biomarkers associated with the implantation window in women with endometriosis

OBJECTIVE

To evaluate the expression of biomarkers of implantation, glycodelin A (GdA), osteopontin (OPN), lysophosphatidic acid receptor 3 (LPA3), and HOXA10, in eutopic endometrium of women with and without endometriosis.

DESIGN

Prospective observational study.

SETTING

Clinical research center.

PATIENT(S)

Twenty-four women with endometriosis and 23 healthy volunteers of similar age.

INTERVENTION(S)

Secretory phase endometrial biopsy.

MAIN OUTCOME MEASURE(S)

Expression of immunohistochemical staining intensity and localization of GdA, OPN, LPA3, and HOXA10 in eutopic endometrium.

RESULT(S)

Endometrial GdA expression was significantly reduced in patients after cycle day 22. The endometrium from women with endometriosis also showed decreased expression of OPN in the late secretory phase and LPA3 and HOXA10 expression in the midsecretory and late secretory phases.

CONCLUSION(S)

The decreased expression of these four biomarkers of implantation may indicate impaired endometrial receptivity in patients with endometriosis, providing one explanation for the subfertility observed even in women with few pelvic implants. Because many of these markers are P dependent, these findings suggest the possibility of reduced endometrial P action in this population.

Peritoneal ectopic lesions from women with endometriosis show abnormalities in progesterone-dependent glycan expression

Examination of 12 paired peritoneal ectopic and eutopic endometria for histochemical binding of Dolichos biflorus agglutinin, normally found in the mid-late secretory part of the cycle, showed a failure of lectin binding in 9 of 11 secretory-phase lesions although the eutopic specimens generally stained normally. This failure of glycan expression in the secretory phase may result from various anomalies, including an inability to respond to progesterone, possibly due to a lack of, or to nonfunctional, progesterone receptors, suggesting that an ectopic environment may produce changes in tissue cell biology and hormonal responsiveness compared with that of eutopic endometrium.

Eutopic endometrium from women with endometriosis shows altered ultrastructure and glycosylation compared to that from healthy controls--a pilot observational study

Endometrial curettings from a cohort of 24 women with endometriosis were compared with matched biopsies from 14 healthy, fertile women and examined for ultrastructural changes and the secretion of glycans bound by the lectin from Dolichos biflorus. Ultrastructural analysis of glandular endometrial tissue from women with stages I to III endometriosis showed heterogeneous responses to the disease, biopsies often showing a mixture of features, combining delays in the maturation sequence with characteristics of later phenotypes particularly in the mid-late secretory phase of the menstrual cycle. Expression of glycans bound by Dolichos biflorus agglutinin was very variable in these cases but generally matched the observed ultrastructure. Biopsies from women with stage IV endometriosis showed immature gland morphology later in the cycle and also failed to express Dolichos biflorus agglutinin-binding glycans, suggesting an association between histological and biochemical function in advanced disease states. These findings may explain in part endometriosis-associated subfertility as blastocyst attachment is intimately associated with appropriate glycosylation and gland morphology.

Estrogen receptor (ER) beta regulates ERalpha expression in stromal cells derived from ovarian endometriosis

CONTEXT

Estradiol and its nuclear receptors, estrogen receptor (ER) alpha and ERbeta, play critical roles in endometrium and endometriosis. Levels of ERbeta, due to pathological hypomethylation of its promoter, are significantly higher in endometriotic vs. endometrial tissue and stromal cells, whereas ERalpha levels are lower in endometriosis. Estradiol regulates ERalpha gene expression via its alternatively used promoters A, B, and C.

OBJECTIVE

The aim of the study was to determine whether high levels of ERbeta in endometriotic stromal cells from ovarian endometriomas regulate ERalpha gene expression.

RESULTS

ERbeta knockdown significantly increased ERalpha mRNA and protein levels in endometriotic stromal cells. Conversely, ERbeta overexpression in endometrial stromal cells decreased ERalpha mRNA and protein levels. ERbeta knockdown significantly decreased proliferation of endometriotic stromal cells. Chromatin immunoprecipitation assays demonstrated that estradiol enhanced ERbeta binding to nonclassical activator protein 1 and specificity protein 1 motifs in the ERalpha gene promoters A and C and a classic estrogen response element in promoter B in endometriotic stromal cells.

CONCLUSIONS

High levels of ERbeta suppress ERalpha expression and response to estradiol in endometrial and endometriotic stromal cells via binding to classic and nonclassic DNA motifs in alternatively used ERalpha promoters. ERbeta also regulates cell cycle progression and might contribute to proliferation of endometriotic stromal cells. We speculate that a significantly increased ratio of ERbeta:ERalpha in endometriotic tissues may also suppress progesterone receptor expression and contribute to progesterone resistance. Thus, ERbeta may serve as a significant therapeutic target for endometriosis.

Endometriosis is associated with progesterone resistance in the baboon (Papio anubis) oviduct: evidence based on the localization of oviductal glycoprotein 1 (OVGP1)

Endometriosis has been associated with a reduced response to progesterone in both the eutopic and ectopic endometrium. In this study we evaluated OVGP1 and steroid receptor expression in oviducts of baboons with endometriosis during the midsecretory phase and determined whether progesterone resistance associated with endometriosis also occurs in the oviduct. Oviducts obtained during the window of uterine receptivity (Day 10 postovulation [PO]) from animals with induced and spontaneous disease were compared to control animals during the proliferative stage and in the implantation window as well as animals treated with the progesterone receptor (PGR) antagonist ZK 137.299 (ZK). OVGP1 was significantly higher in animals with endometriosis compared with Day 10 PO controls and was similar to that seen in the late proliferative phase and in ZK-treated animals. Baboons with spontaneous endometriosis also showed a similar persistence of OVGP1, which was correlated with the maintenance of estrogen receptor 1 (ESR1) in the epithelial cells of animals with endometriosis. However, epithelial cell height and the percentage of ciliation were not affected by endometriosis. These data imply that the normal antagonism of progesterone on ESR and OVGP1, which results in their downregulation during the window of implantation, is absent in animals with endometriosis. This was confirmed further when the action of PGR was antagonized in animals without disease, which also resulted in the persistence of ESR1 and OVGP1. These studies suggest that an aberrant oviductal environment may be an additive factor that contributes to endometriosis-associated infertility.

Ultrastructure of ectopic peritoneal lesions from women with endometriosis, including observations on the contribution of coelomic mesothelium

Following a study in a baboon model of endometriosis, we here describe the morphology of ectopic peritoneal lesions in the human to examine the effects of an ectopic site on glandular structure and function. Ectopic biopsies from 17 women with endometriosis were fixed and processed for electron microscopy. Certain biopsies were also probed for intermediate filaments using immunohistochemistry. Ultrastructurally, lesions showed many different glandular morphologies with indications of delayed maturation compared to normal endometrium. Mesothelium covered some lesions and there was evidence of mesothelial invasion into the stroma. Ectopic endometriotic lesions from women with endometriosis showed ultrastructural differences from eutopic endometrium, with indications that mesothelial invasion may contribute to gland development in some lesions.

Deficiency of immunophilin FKBP52 promotes endometriosis

Endometriosis is a common gynecological disease that affects approximately 10% of women of childbearing age. It is characterized by endometrial growth outside the uterus and often results in inflamed lesions, pain, and reduced fertility. Although heightened estrogenic activity and/or reduced progesterone responsiveness are considered to be involved in the etiology of endometriosis, neither the extent of their participation nor the underlying mechanisms are clearly understood. Heterogeneous uterine cell types differentially respond to estrogen and progesterone (P(4)). P(4), primarily acting via its nuclear receptor (PR), activates gene transcription and impacts many reproductive processes. Deletion of Fkbp52, an immunophilin cochaperone for PR, results in uterine-specific P(4) resistance in mice, creating an opportunity to study the unique aspects of P(4) signaling in endometriosis. Here we explored the roles of FKBP52 in this disease using Fkbp52(-/-) mice. We found that the loss of FKBP52 encourages the growth of endometriotic lesions with increased inflammation, cell proliferation, and angiogenesis. We also found remarkable down-regulation of FKBP52 in cases of human endometriosis. Our results provide the first evidence corroborated by genetic studies in mice for a potential role of an immunophilin cochaperone in the etiology of human endometriosis. This investigation is highly relevant for clinical application, particularly because P(4) resistance is favorably indicated in endometriosis and other gynecological diseases.

Dioxin may promote inflammation-related development of endometriosis

Laboratory and population-based studies suggest that exposure to environmental toxicants may be one of several triggers for the development of endometriosis. We discuss evidence that modulation of the endometrial endocrine-immune interface could mechanistically link toxicant exposure to the development of this disease.

Inflammatory status influences aromatase and steroid receptor expression in endometriosis

Aberrant up-regulation of aromatase in eutopic endometrium and implants from women with endometriosis has been reported. Aromatase induction may be mediated by increased cyclooxygenase-2 (COX-2). Recently, we demonstrated that progesterone receptor (PR)-A and PR-B serve an antiinflammatory role in the uterus by antagonizing nuclear factor kappaB activation and COX-2 expression. PR-C, which antagonizes PR-B, is up-regulated by inflammation. Although estrogen receptor alpha (ERalpha) is implicated in endometriosis, an antiinflammatory role of ERbeta has been suggested. We examined stage-specific expression of aromatase, COX-2, ER, and PR isoform expression in eutopic endometrium, implants, peritoneum, and endometrioma samples from endometriosis patients. Endometrial and peritoneal biopsies were obtained from unaffected women and those with fibroids. Aromatase expression in eutopic endometrium from endometriosis patients was significantly increased compared with controls. Aromatase expression in endometriosis implants was markedly increased compared with eutopic endometrium. Aromatase mRNA levels were increased significantly in red implants relative to black implants and endometrioma cyst capsule. Moreover, COX-2 expression was increased in implants and in eutopic endometrium of women with endometriosis as compared with control endometrium. As observed for aromatase mRNA, the highest levels of COX-2 mRNA were found in red implants. The ratio of ERbeta/ERalpha mRNA was significantly elevated in endometriomas compared with endometriosis implants and eutopic endometrium. Expression of PR-C mRNA relative to PR-A and PR-B mRNA was significantly increased in endometriomas compared with eutopic and control endometrium. PR-A protein was barely detectable in endometriomas. Thus, whereas PR-C may enhance disease progression, up-regulation of ERbeta may play an antiinflammatory and opposing role.

Neuroendocrine-immune disequilibrium and endometriosis: an interdisciplinary approach

Endometriosis, a chronic disease characterized by endometrial tissue located outside the uterine cavity, affects one fourth of young women and is associated with chronic pelvic pain and infertility. However, an in-depth understanding of the pathophysiology and effective treatment strategies of endometriosis is still largely elusive. Inadequate immune and neuroendocrine responses are significantly involved in the pathophysiology of endometriosis, and key findings are summarized in the present review. We discuss here the role of different immune mechanisms particularly adhesion molecules, proteinglycan interactions, and pro-angiogenic mediators in the development and progression of the disease. Finally, we introduce the concept of endometrial dissemination as result of a neuroendocrine-immune disequilibrium in response to high levels of perceived stress caused by cardinal clinical symptoms of endometriosis.

Developmental exposure of mice to TCDD elicits a similar uterine phenotype in adult animals as observed in women with endometriosis

Whether environmental toxicants impact an individual woman's risk for developing endometriosis remains uncertain. Although the growth of endometrial glands and stroma at extra-uterine sites is associated with retrograde menstruation, our studies suggest that reduced responsiveness to progesterone may increase the invasive capacity of endometrial tissue in women with endometriosis. Interestingly, our recent studies using isolated human endometrial cells in short-term culture suggest that experimental exposure to the environmental contaminant 2,3,7,8-tetracholorodibenzo-p-dioxin (TCDD) can alter the expression of progesterone receptor isotypes. Compared to adult exposure, toxicant exposure during development can exert a significantly greater biological impact, potentially affecting the incidence of endometriosis in adults. To address this possibility, we exposed mice to TCDD at critical developmental time points and subsequently examined uterine progesterone receptor expression and steroid responsive transforming growth factor-beta2 expression in adult animals. We find that the uterine phenotype of toxicant-exposed mice is markedly similarly to the endometrial phenotype of women with endometriosis.

Deregulation of the HOXA10 homeobox gene in endometrial carcinoma: role in epithelial-mesenchymal transition

Homeobox genes encode transcription factors that control cell differentiation and play essential roles in developmental patterning. Increasing evidence indicates that many homeobox genes are aberrantly expressed in cancers, and that their deregulation significantly contributes to tumor progression. The homeobox gene HOXA10 controls uterine organogenesis during embryonic development and functional endometrial differentiation in the adult. We investigated whether HOXA10 expression is deregulated in endometrial carcinomas, and how counteracting this aberrant expression modifies tumor behavior. We found that down-regulation of HOXA10 expression in endometrial carcinomas strongly correlates with increased tumor grade and is associated with methylation of the HOXA10 promoter. Enforced expression of HOXA10 in endometrial carcinoma cells inhibited invasive behavior in vitro and tumor dissemination in nude mice. The inhibitory effect of HOXA10 on invasive behavior was attributable at least in part to the ability of HOXA10 to induce expression of the epithelial cell adhesion molecule E-cadherin by down-regulating expression of Snail, a repressor of E-cadherin gene transcription. These findings reveal a novel role for HOXA10 deregulation in the progression of endometrial carcinoma by promoting epithelial-mesenchymal transition.