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

Differential immunohistochemical expression of matrix metalloproteinase-2 and tissue inhibitor of metalloproteinase-2 in cow uteri with adenomyosis during follicular phase

The present investigation was intended to show a different immunohistochemical profile of matrix metalloproteinase-2 and Tissue inhibitor metalloproteinase-2 in bovine uteri with adenomyosis during follicular phase. Uterine samples of 32 cows in reproductive age were taken from the medial third of one of the uterine horns and grouped according to the adenomyosis degree (superficial and deep). Tissue sections (4 μm) were incubated overnight at 4°C with monoclonal antibody for matrix metalloproteinase-2 and Tissue inhibitor metalloproteinase-2. Staining intensities were evaluated in the luminal epithelium, ectopic and dystopic endometrial tissue (stroma, capillaries and glands), endometrial-myometrial border, myometrium, myometrial vessels (middle tunic and endothelium). The matrix metalloproteinase-2 expression was higher for deep adenomyosis samples, showing a differential mean reactivity in superficial endometrium, myometrial vessels, myometrium adjacent to adenomyotic focus and endometrial-myometrial border (P < 0.05). Moreover, matrix metalloproteinase-2 expression was higher in deep adenomyosis samples than that of Tissue inhibitor metalloproteinase-2 in almost all uterine structures analyzed (except for the endometrial and myometrial vessels and endometrial-myometrial border). The opposite was observed in the follicular phase, for both normal specimens and with superficial adenomyosis, where Tissue inhibitor metalloproteinase-2 expression was higher than that of matrix metalloproteinase-2. In conclusion, a differential pattern of matrix metalloproteinase-2 and Tissue inhibitor metalloproteinase-2 was observed in cow uteri with adenomyosis.

Does advanced-stage endometriosis affect the gene expression of estrogen and progesterone receptors in granulosa cells?

OBJECTIVE

To evaluate how endometriosis affects the expression of estrogen and progesterone receptors mRNA in granulosa cells.

DESIGN

Prospective study.

SETTING

IVF-ET program at Osaka Medical College.

PATIENT(S)

Eighteen patients with revised American Fertility Society stage IV endometriosis and 23 patients with tubal infertility without endometriosis.

INTERVENTION(S)

Granulosa cells obtained from patients with endometriosis were examined for estrogen (ER-β, ER-α) and progesterone (PR-A, PR-B) receptor mRNA expression ratio against GAPDH.

MAIN OUTCOME MEASURE(S)

Hormonal environment and clinical outcome were investigated. Expression of ER and PR mRNA were evaluated by StepOne real-time polymerase chain reaction (PCR) analysis.

RESULT(S)

Total hMG/FSH levels were statistically higher in patients with endometriosis; however, high-quality embryo rates and pregnancy rates were lower in patients with endometriosis than in patients with tubal infertility. Expression of PR-A and ER-α in patients with endometriosis was statistically higher than in patients with tubal infertility. The expression of PRs and ERs in patients with tubal infertility showed a positive correlation; however, it was not identified in the endometriosis group.

CONCLUSION(S)

The higher PR-A and ER-α gene expression in granulosa cells in patients with endometriosis, compared with patients with tubal infertility, might be a leading cause of ovarian dysfunction due to 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.

Chronic pelvic pain and endometriosis: translational evidence of the relationship and implications

BACKGROUND

Many clinicians and patients believe that endometriosis-associated pain is due to the lesions. Yet causality remains an enigma, because pain symptoms attributed to endometriosis occur in women without endometriosis and because pain symptoms and severity correlate poorly with lesion characteristics. Most research and reviews focus on the lesions, not the pain. This review starts with the recognition that the experience of pain is determined by the central nervous system (CNS) and focuses on the pain symptoms.

METHODS

Comprehensive searches of Pubmed, Medline and Embase were conducted for current basic and clinical research on chronic pelvic pain and endometriosis. The information was mutually interpreted by a basic scientist and a clinical researcher, both in the field of endometriosis. The goal was to develop new ways to conceptualize how endometriosis contributes to pain symptoms in the context of current treatments and the reproductive tract.

RESULTS

Endometriotic lesions can develop their own nerve supply, thereby creating a direct and two-way interaction between lesions and the CNS. This engagement provides a mechanism by which the dynamic and hormonally responsive nervous system is brought directly into play to produce a variety of individual differences in pain that can, in some women, become independent of the disease itself.

CONCLUSIONS

Major advances in improving understanding and alleviating pain in endometriosis will likely occur if the focus changes from lesions to pain. In turn, how endometriosis affects the CNS would be best examined in the context of mechanisms underlying other chronic pain conditions.

Developmental dioxin exposure of either parent is associated with an increased risk of preterm birth in adult mice

We have previously described diminished uterine progesterone response and increased uterine sensitivity to inflammation in adult female mice with a history of developmental exposure to TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin). Since parturition in mammals is an inflammatory process mediated in part by a decline in progesterone action, toxicant-mediated disruption of progesterone receptor (PR) expression at the maternal-fetal interface would likely impact the timing of birth. Therefore, in the current study, we examined pregnancy outcomes in adult female mice with a similar in utero exposure to TCDD. We also examined the impact of in utero TCDD exposure of male mice on pregnancy outcomes in unexposed females since the placenta, a largely paternally derived organ, plays a major role in the timing of normal parturition via inflammatory signaling. Our studies indicate that developmental exposure of either parent to TCDD is associated with preterm birth in a subsequent adult pregnancy due to altered PR expression and placental inflammation.

Development and prevention of postsurgical adhesions in a chimeric mouse model of experimental endometriosis

OBJECTIVE

To examine the impact of a recent surgery on development of endometriosis-related adhesions in a chimeric model and to determine the therapeutic efficacy of pioglitazone (PIO).

DESIGN

Human endometrial biopsies were maintained in E(2) with or without PIO for 24 h before intraperitoneal injection into immunocompromised mice also treated with or without PIO at multiple time points after peritoneal surgery. The presence and extent of adhesions were examined in animals relative to the initial establishment of experimental endometriosis.

SETTING

Medical school research center.

PATIENT(S)

Endometrial biopsies for experimental studies were provided by normally cycling women without a medical history indicative of endometriosis or adhesions.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Examination of the development of endometriosis-related adhesions in an experimental model.

RESULT(S)

Without therapeutic intervention, injection of E(2)-treated human endometrial tissue into mice near the time of peritoneal surgery resulted in multiple adhesions and extensive endometriotic-like disease. In contrast, PIO treatment reduced adhesive disease and experimental endometriosis related to surgical injury.

CONCLUSION(S)

The presence of human endometrial tissue fragments in the peritoneal cavity of mice with a recent surgical injury promoted development of both adhesive disease and experimental endometriosis. Targeting inflammation and angiogenesis with PIO therapy limited the development of postsurgical adhesions associated with ectopic endometrial growth.

Epidemiology of endometriosis: an assessment of risk factors

Endometriosis is the third leading cause of gynecologic hospitalization in the United States. This disease impacts both a woman's physical and mental well being. This impact is often compounded by the frequent delay from the onset of symptoms to a confirmed diagnosis, which may average 6 years or more. The precise incidence and prevalence of endometriosis remains elusive for a multitude of reasons, and their measurement remains difficult to accurately assess. None the less, there are many unique and interesting components to the disease which arise when population-based analyses are performed. The goal of this paper is to investigate and summarize the existing epidemiologic parameters, primarily risk factors, associated with endometriosis.

Prokineticin 1, homeobox A10, and progesterone receptor messenger ribonucleic acid expression in primary cultures of endometrial stromal cells isolated from endometrium of healthy women and from eutopic endometrium of women with endometriosis

OBJECTIVE

To examine prokineticin 1 (PROK1), homeobox (HOX) A10, and P receptor (PR) messenger ribonucleic acid (mRNA) expression in primary cultures of endometrial stromal cells (ESC) obtained from eutopic endometrial samples of patients with endometriosis and to clarify whether in vitro steroid hormone dependence of PROK1 gene expression is altered in endometriosis.

DESIGN

Prospective laboratory study.

SETTING

Tertiary university hospital.

PATIENT(S)

Twelve normal women (controls) and 12 patients affected by moderate to severe endometriosis in the midsecretory phase of the menstrual cycle.

INTERVENTION(S)

Endometrial specimens were obtained from control women and from women affected by endometriosis; ESC were isolated from endometrial biopsies, and primary cultures were established.

MAIN OUTCOME MEASURE(S)

Real-time polymerase chain reaction analysis of PROK1, HOXA10, and PR mRNA expression in ESC after 1-4 days of steroid hormone treatment and after decidual differentiation.

RESULT(S)

Contrary to ESC from control women, in ESC obtained from women affected by endometriosis PROK1 and PR mRNA expression was not induced by 1-4 days of treatment with steroid hormones. Nevertheless, when ESC from both groups of women were differentiated to decidual phenotype, PROK1 mRNA was up-regulated and PR and HOXA10 mRNA were down-regulated to the same extent.

CONCLUSION(S)

Our results provide additional evidence for P resistance in endometriosis.

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.

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.

Female reproductive disorders: the roles of endocrine-disrupting compounds and developmental timing

OBJECTIVE

To evaluate the possible role of endocrine-disrupting compounds (EDCs) on female reproductive disorders emphasizing developmental plasticity and the complexity of endocrine-dependent ontogeny of reproductive organs. Declining conception rates and the high incidence of female reproductive disruptions warrant evaluation of the impact of EDCs on female reproductive health.

DESIGN

Publications related to the contribution of EDCs to disorders of the ovary (aneuploidy, polycystic ovary syndrome, and altered cyclicity), uterus (endometriosis, uterine fibroids, fetal growth restriction, and pregnancy loss), breast (breast cancer, reduced duration of lactation), and pubertal timing were identified, reviewed, and summarized at a workshop.

CONCLUSION(S)

The data reviewed illustrate that EDCs contribute to numerous human female reproductive disorders and emphasize the sensitivity of early life-stage exposures. Many research gaps are identified that limit full understanding of the contribution of EDCs to female reproductive problems. Moreover, there is an urgent need to reduce the incidence of these reproductive disorders, which can be addressed by correlative studies on early life exposure and adult reproductive dysfunction together with tools to assess the specific exposures and methods to block their effects. This review of the EDC literature as it relates to female health provides an important platform on which women's health can be improved.

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.

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.

Gene expression profiles and functional characterization of human immortalized endometriotic epithelial and stromal cells

OBJECTIVE

To determine whether immortalized endometriotic cells can be used as potential models to unravel pathophysiology/pathogenesis of endometriosis in humans.

DESIGN

In vitro study. Human immortalized endometriotic epithelial and stromal cells.

SETTING

College of Veterinary Medicine and Biomedical Sciences, Texas A&M University.

PATIENT(S)

Not applicable.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Gene expression pattern and prostaglandin E(2) production and activity of matrix metalloproteinase 2 and matrix metalloproteinase 9.

RESULT(S)

Several genes associated with estrogen and progesterone biosynthesis and signaling, cell cycle regulation, extracellular matrix degradation, angiogenesis, cell growth and survival, cytokine production, and prostaglandin E(2) biosynthesis, transport, and signaling were expressed in human immortalized endometriotic cells. These endometriotic epithelial and stromal cells exhibited migrating and invading potential, produced a high quantity of prostaglandin E(2), and showed higher matrix metalloproteinase 2 and matrix metalloproteinase 9 activity compared to normal endometrial, epithelial, and stromal cells.

CONCLUSION(S)

Human immortalized endometriotic epithelial and stromal cells could be used as ideal models to study the molecular and cellular aspects of endometriosis in humans.

The altered distribution of the steroid hormone receptors and the chaperone immunophilin FKBP52 in a baboon model of endometriosis is associated with progesterone resistance during the window of uterine receptivity

This study examines the distribution of estrogen receptors (ESR), progesterone receptors (Pgr), and the chaperone immunophilin FKBP52 in the eutopic endometrium in a baboon model of endometriosis during the window of receptivity to determine if their aberrant distribution contributes to reduced fecundity. Endometriosis was induced by inoculation of menstrual endometrium into the peritoneal cavity. Eutopic endometrium was collected at 3, 6, 9, 12, and 15 months postinoculation. Western blot (WB) and immunohistochemical analyses were performed. Isolated endometrial stromal cells were cultured in the presence or absence of steroid hormones. In animals with endometriosis, ESR-1 (ER-alpha) decreased in endometrial stromal cells, while ESR-2 (ER-beta) was reduced in both glandular epithelial (GE) and stromal cells. Immunoreactive total Pgr was markedly diminished in the GE, which was confirmed by WB analysis. Furthermore, treatment of isolated stromal cells from baboons with endometriosis with hormones did not increase levels of PRA or PRB as in control baboons. FKBP52 was also reduced in the eutopic endometrium of baboons with endometriosis. Endometriosis results in an aberrant distribution of ESR-1, ESR-2, Pgr, and FKBP52 in the eutopic endometrium. The authors propose that a dysregulation in the paracrine signaling between the endometrial stromal and GE cells reduces the responsiveness of Pgr, creating an endometrial environment that is unsuitable for implantation.

Prolonged stimulation with tumor necrosis factor-alpha induced partial methylation at PR-B promoter in immortalized epithelial-like endometriotic cells

The promoter of P receptor isoform B (PR-B) has recently been shown to be hypermethylated in endometriotic tissues, but one question remains as what causes the aberrant methylation. We show that sustained stimulation of an epithelial-like endometriotic cell line with tumor necrosis factor alpha stimulation for 30 days induced partial methylation in the promoter region of PR-B with concomitant reduction of PR-B expression.

Gene expression analysis of endometrium reveals progesterone resistance and candidate susceptibility genes in women with endometriosis

The identification of molecular differences in the endometrium of women with endometriosis is an important step toward understanding the pathogenesis of this condition and toward developing novel strategies for the treatment of associated infertility and pain. In this study, we conducted global gene expression analysis of endometrium from women with and without moderate/severe stage endometriosis and compared the gene expression signatures across various phases of the menstrual cycle. The transcriptome analysis revealed molecular dysregulation of the proliferative-to-secretory transition in endometrium of women with endometriosis. Paralleled gene expression analysis of endometrial specimens obtained during the early secretory phase demonstrated a signature of enhanced cellular survival and persistent expression of genes involved in DNA synthesis and cellular mitosis in the setting of endometriosis. Comparative gene expression analysis of progesterone-regulated genes in secretory phase endometrium confirmed the observation of attenuated progesterone response. Additionally, interesting candidate susceptibility genes were identified that may be associated with this disorder, including FOXO1A, MIG6, and CYP26A1. Collectively these findings provide a framework for further investigations on causality and mechanisms underlying attenuated progesterone response in endometrium of women with endometriosis.

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.

Stromal cells of endometriosis fail to produce paracrine factors that induce epithelial 17beta-hydroxysteroid dehydrogenase type 2 gene and its transcriptional regulator Sp1: a mechanism for defective estradiol metabolism

OBJECTIVE

In endometrium, stromal progesterone receptors mediate production of paracrine factors, which enhance binding of the transcription factor specific protein-1 to the promoter of the gene encoding the 17beta-hydroxysteroid dehydrogenase type 2 enzyme responsible for converting biologically active estradiol to estrone in epithelium. The objective of this study is to define the cellular defect responsible for the disruption of this stromal-epithelial interaction in endometriosis.

STUDY DESIGN

We determined the effects of conditioned media generated from primary human eutopic endometrial stromal cells vs endometriotic stromal cells on Ishikawa malignant endometrial epithelial cells.

RESULTS

Conditioned media from progestin-pretreated eutopic endometrial stromal cells but not endometriotic stromal cells significantly stimulated specific protein-1 protein levels, 17beta-hydroxysteroid dehydrogenase type 2 messenger RNA levels and promoter activity, and binding activity of specific protein-1 to the 17beta-hydroxysteroid dehydrogenase type 2 promoter region in Ishikawa cells.

CONCLUSION

A stromal cell defect in endometriosis blocks formation of progesterone-dependent production of factors leading to 17beta-hydroxysteroid dehydrogenase type 2 deficiency and defective conversion of estradiol to estrone in epithelium.

The role of progestins in treating the pain of endometriosis

Progestins, synthetic progestational agents, have been used in the management of symptomatic endometriosis both as primary therapy and as an adjunct to surgical resection. A variety of oral agents have been employed in this regard with investigators demonstrating differing degrees of benefit. Unfortunately, due to the lack of large-scale, appropriately controlled, randomized trials, or dose-ranging studies, no single agent can be demonstrated to be truly efficacious. The lack of a standardized instrument to evaluate painful symptoms makes comparative analysis more difficult. Injectable administration of long-acting depot medroxyprogesterone acetate preparations intramuscularly or subcutaneously has been investigated in three randomized trials. The lower dose subcutaneous injection holds promise with an apparent reduction in side effects. Issues of reversible bone mineral density loss, breakthrough bleeding, and return of menses have not been completely resolved. Selective progesterone receptor modulators represent an intriguing alternative. These orally administered agents have been shown in preliminary investigations to be not only efficacious in reducing symptoms but also associated with minimal side effects. Further investigation of these agents is clearly required.

Nuclear factor-kappab (NF-kappaB): an unsuspected major culprit in the pathogenesis of endometriosis that is still at large?

Endometriosis, defined as the ectopic presence of endometrial glandular and stromal cells outside the uterine cavity, is a common benign gynecological disorder with an enigmatic pathogenesis. Many genes and gene products have been reported to be altered in endometriosis, yet some of them may not be major culprits but merely unwitting accomplices or even innocent bystanders. Therefore, the identification and apprehension of major culprits in the pathogenesis of endometriosis are crucial to the understanding of the pathogenesis and would help to develop better therapeutics for endometriosis. Although so far NF-kappaB only has left few traces of incriminating fingerprints, several lines of investigation suggest that NF-kappaB, a pivotal pro-inflammatory transcription factor, could promote and maintain endometriosis. Various inflammatory agents, growth factors, and oxidative stress activate NF-kappaB. NF-kappaB proteins themselves and proteins regulated by them have been linked to cellular transformation, proliferation, apoptosis, angiogenesis, and invasion. Interestingly, all existing and nearly all investigational medications for endometriosis appear to act through suppression of NF-kappaB activation. In endometriotic cells, NF-kappaB appears to be constitutively activated, and suppression of NF-kappaB activity by NF-kappaB inhibitors or proteasome inhibitors suppresses proliferation in vitro. Viewing NF-kappaB as a major culprit, an autoregulatory loop model can be postulated, which is consistent with existing data and, more importantly, can explain several puzzling phenomena that are otherwise difficult to interpret based on prevailing theories. This view has immediate and important implications for novel ways to treat endometriosis. Further research is warranted to precisely delineate the roles of NF-kappaB in the pathogenesis of endometriosis and to indict and convict its aiders and abettors.

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.

The role of endometrium in endometriosis

Endometriosis is defined as the presence of endometrial glands and stroma outside the uterus. Several theories have been proposed to explain the pathogenesis of this disease. According to Sampson's retrograde menstruation theory, endometrial cells are refluxed through the fallopian tubes during the menstruation and implant onto peritoneum or pelvic organs. Since retrograde menstruation is a very common phenomenon among women of reproductive age, there must be other factors that may contribute to the pathophysiology and/or pathogenesis of endometriosis. Genetic predisposition, environmental factors, and alterations in immune and endocrine functions are believed to play significant roles in the establishment and maintenance of endometriosis. Although the eutopic endometriums of women with and without endometriosis are histologically similar, studies revealed that there are many fundamental differences between these two tissues. Invasive properties, decreased apoptosis, alterations in expression of specific gene and proteins, and increased steroid and cytokine production have been identified in eutopic endometrium of women with endometriosis. Furthermore, significant biochemical differences exist even between ectopic and autologous eutopic endometrium. These differences can be explained by the direct effects of an inflammatory peritoneal environment.

Expression of WT1 is down-regulated in eutopic endometrium obtained during the midsecretory phase from patients with endometriosis

OBJECTIVE

To investigate whether WT1 protein expression is altered in eutopic endometrium of endometriosis patients.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENT(S)

Patients with endometriosis and fertile women with macroscopically normal pelvic cavities.

INTERVENTION(S)

During surgery, endometrial tissues were obtained from 59 patients with deep infiltrating endometriosis, ovarian endometriosis, or only superficial peritoneal endometriosis. Control endometrial tissue samples were obtained from 40 fertile women who underwent laparoscopic tubal ligation or reversal of tubal sterilization.

MAIN OUTCOME MEASURE(S)

The percentage of nuclear surface positively immunostained for WT1 (PI) and WT1-positive microvessel density.

RESULT(S)

The PI was significantly lower in endometrial stromal cells from patients with deep infiltrating endometriosis than in stroma from control subjects during the midsecretory phase, whereas there was no significant difference between the two populations during the proliferative, early secretory, and late secretory phases. The PI was also significantly lower during the midsecretory phase in endometrial stromal cells from patients with ovarian endometriosis and superficial peritoneal endometriosis compared with control subjects.

CONCLUSION(S)

During the midsecretory phase, PI in endometrial stromal cells is down-regulated in patients with deep infiltrating endometriosis, ovarian endometriosis, and superficial peritoneal endometriosis compared with endometrium from healthy control subjects.

Analysis of aromatase and 17beta-hydroxysteroid dehydrogenase type 2 messenger ribonucleic acid expression in deep endometriosis and eutopic endometrium using laser capture microdissection

OBJECTIVE

To investigate mRNA expression of aromatase and 17beta-hydroxysteroid dehydrogenase type 2 (17betaHSD2) in epithelial and stromal cells from eutopic and ectopic endometrium of patients with deep endometriosis.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENT(S)

Patients with deep endometriosis and fertile women with macroscopically normal pelvic cavities.

INTERVENTION(S)

During surgery, 30 endometrial and 16 endometriotic samples were obtained from 30 patients with deep endometriosis. Control endometrial samples were obtained from 24 fertile women with macroscopically normal pelvic cavities who underwent laparoscopic tubal ligation or reversal of tubal sterilization. Epithelial cells and stromal cells from endometrial or endometriotic tissues were microdissected using laser capture microdissection.

MAIN OUTCOME MEASURE(S)

Expression levels of aromatase and 17betaHSD2 mRNA in microdissected epithelial and stromal cells were determined using quantitative real-time reverse transcriptase polymerase chain reaction.

RESULT(S)

Aromatase mRNA expression was significantly higher in epithelial cells than in stromal cells in both eutopic and ectopic endometrium obtained from endometriosis patients. In the ectopic endometrium of 8 patients (8/16, 50%), 17betaHSD2 expression was not detected in either epithelial or stromal cells. In eutopic endometrium from endometriosis patients, 17betaHSD2 expression in epithelial cells was significantly increased during the early, middle, and late secretory phases compared with the late proliferative phase, whereas no significant cyclical difference was detected in control endometrium.

CONCLUSION(S)

Local estrogen concentration may be much higher in epithelial cells than in stromal cells in deep endometriotic tissue.

Progesterone resistance in endometriosis: link to failure to metabolize estradiol

Endometriosis is the most common cause of pelvic pain and affects an estimated 5 million women in the US. The biologically active estrogen estradiol (E2) is the best-defined mitogen for the growth and inflammation processes in the ectopic endometriotic tissue that commonly resides on the pelvic organs. Progesterone and progestins may relieve pain by limiting growth and inflammation in endometriosis but a portion of patients with endometriosis and pelvic pain do not respond to treatment with progestins. Moreover, progesterone-induced molecular changes in the eutopic (intrauterine) endometrial tissue of women with endometriosis are either blunted or undetectable. These in vivo 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 receptors (PRs) and the lack of the PR isoform named progesterone receptor B (PR-B). In normal endometrium, progesterone acts on stromal cells to induce secretion of paracrine factor(s). These unknown factor(s) act on neighboring epithelial cells to induce the expression of the enzyme 17beta-hydroxysteroid dehydrogenase type 2 (17beta-HSD-2), which metabolizes the biologically active estrogen E2 to estrone (E1). In endometriotic tissue, progesterone does not induce epithelial 17beta-HSD-2 expression due to a defect in stromal cells. The inability of endometriotic stromal cells to produce progesterone-induced paracrine factors that stimulate 17beta-HSD-2 may be due to the lack of PR-B and very low levels of progesterone receptor A (PR-A) observed in vivo in endometriotic tissue. The end result is deficient metabolism of E2 in endometriosis giving rise to high local concentrations of this local mitogen. The cellular and molecular mechanisms underlying progesterone resistance and failure to metabolize E2 in endometriosis are reviewed.

Trimegestone differentially modulates the expression of matrix metalloproteinases in the endometrial stromal cell

Matrix metalloproteinases (MMP) are considered to be of critical importance in the initiation of menstruation where MMP protein levels are reciprocally modulated by the actions of the gonadal steroid hormones, estradiol (E(2)) and progesterone (P4), with P4 being considered the principal suppressor of endometrial MMP expression. Trimegestone (T) is a novel progestagen that tightly controls menstruation timing and duration through mechanisms that might involve MMP suppression. Endometrial stromal cells treated with 10(-6) M E(2), P4 or T in the presence and absence of 10(-6)M RU486 showed that both T and P4 suppressed the expression of MMP-1 and MMP-3 transcripts and secreted protein, whereas MMP-9 was not produced in culture. The suppressive effect of T or P4 on MMP-1 and MMP-3 transcript levels was enhanced in the presence of E(2) and attenuated in the presence of RU486, although MMP-1 proteins were unaffected by the presence of RU486, which alone acted as a partial progesterone agonist in these cultures. Immunohistochemistry with MMP-1, MMP-3 and MMP-9-specific antibodies performed on endometrial biopsies obtained from non-treated, LH-dated, normally cycling women and endometrial biopsies obtained from postmenopausal women treated with T-based HRT showed that immunoreactive MMP-1 and MMP-3 was higher in the menstrual phase, whilst MMP-9 expression was higher in the late luteal phase (P = 0.03) and T significantly inhibited the presence of MMP-9(+) cells. These data suggest that T acts in a similar manner to P4, but causes subtle differences in expression patterns of MMPs that may explain the different clinical effect that this progestagen has on endometrial behaviour compared to P4.

Reduced expression of progesterone receptor-B in the endometrium of women with endometriosis and in cocultures of endometrial cells exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin

OBJECTIVE

To analyze endometrial progesterone receptor (PR) expression in women with endometriosis compared with disease-free women and to assess the impact of in vitro 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure on PR isotype expression.

DESIGN

Controlled laboratory study.

SETTING

University medical center.

PATIENT(S)

Healthy volunteers and women with surgically diagnosed endometriosis.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Analysis of in vivo PR-A and PR-B expression in endometrium from women with and without endometriosis. The impact of in vitro TCDD exposure on PR-B/PR-A ratio and cell-specific matrix metalloproteinase (MMP) expression was also determined.

RESULT(S)

The PR-B/PR-A ratio was lower in endometrial tissues from women with endometriosis compared with normal tissues. A similar ratio was induced in normal stromal cells cocultured with epithelial cells and exposed to TCDD. Disruption of stromal PR expression following TCDD exposure was associated with a failure of P-mediated down-regulation of both stromal-specific pro-MMP-3 and epithelial-specific pro-MMP-7.

CONCLUSION(S)

Our data suggest that reduced progesterone (P) sensitivity in the endometrium of women with endometriosis may be related to an altered pattern of PR expression. The ability of TCDD to selectively down-regulate stromal PR-B expression and increase MMP expression in both stromal and epithelial cells suggests that exposure to this toxin may negatively impact P-mediated cell-cell communication in the human endometrium.

Endometrial biology and the etiology of endometriosis

Two recent studies reported in this issue of Fertility and Sterility have explored important issues regarding the understanding and diagnosing of endometriosis. These studies emphasize the complexity of endometriosis and underscore the different roles of clinicians and translational scientists in exploring this disease.

ANÁLISE HISTOLÓGICA DA ENDOMETRIOSE EM RATAS DURANTE AS FASES DO CICLO ESTRAL

RESUMO A presente pesquisa teve como objetivo analisar morfologicamente os sítios de implantes endometriais sobre a região externa da musculatura da parede abdominal anterior de ratas, durante o ciclo estral. Para tanto foram utilizadas 16 ratas albinas (Rattus norvegicus albinus), da linhagem Wistar com 90 dias de idade, obtidas do biotério do Departamento de Morfologia e Fisiologia Animal da UFRPE, as quais foram submetidas à indução da endometriose. A análise histológica dos implantes foi realizada por meio da microscopia de luz, utilizando-se técnicas de colorações pela Hematoxilina-Eosina (H-E) e pelo Tricrômico de Mallory. O material coletado foi fixado em líquido de Boüin e processado para inclusão em “paraplast”. Os resultados mostraram que as fases de proestro, estro e diestro foram mais favoráveis para o desenvolvimento dos implantes endometriais em ratas, quando comparadas ao metaestro.