Basic research in endometriosis

Endometriosis risk alleles at 1p36.12 act through inverse regulation of CDC42 and LINC00339

Genome-wide association studies (GWAS) have identified markers within the WNT4 region on chromosome 1p36.12 showing consistent and strong association with increasing endometriosis risk. Fine mapping using sequence and imputed genotype data has revealed strong candidates for the causal SNPs within these critical regions; however, the molecular pathogenesis of these SNPs is currently unknown. We used gene expression data collected from whole blood from 862 individuals and endometrial tissue from 136 individuals from independent populations of European descent to examine the mechanism underlying endometriosis susceptibility. Association mapping results from 7,090 individuals (2,594 cases and 4,496 controls) supported rs3820282 as the SNP with the strongest association for endometriosis risk (P = 1.84 × 10−5, OR = 1.244 (1.126-1.375)). SNP rs3820282 is a significant eQTL in whole blood decreasing expression of LINC00339 (also known as HSPC157) and increasing expression of CDC42 (P = 2.0 ×10−54 and 4.5x10−4 respectively). The largest effects were for two LINC00339 probes (P = 2.0 ×10−54; 1.0 × 10−34). The eQTL for LINC00339 was also observed in endometrial tissue (P = 2.4 ×10−8) with the same direction of effect for both whole blood and endometrial tissue. There was no evidence for eQTL effects for WNT4. Chromatin conformation capture provides evidence for risk SNPs interacting with the promoters of both LINC00339 and CDC4 and luciferase reporter assays suggest the risk SNP rs12038474 is located in a transcriptional silencer for CDC42 and the risk allele increases expression of CDC42. However, no effect of rs3820282 was observed in the LINC00339 expression in Ishikawa cells. Taken together, our results suggest that SNPs increasing endometriosis risk in this region act through CDC42, but further functional studies are required to rule out inverse regulation of both LINC00339 and CDC42.

Length of Menstrual Cycle and Risk of Endometriosis: A Meta-Analysis of 11 Case-Control Studies

Endometriosis is a complex disease that affects a large number of women worldwide and may cause pain and infertility. To systematically review published studies evaluating the relationship between menstrual cycle length and risk of endometriosis. We searched the Cochrane Library, PubMed, Web of Science, and EMBASE in databases in July 2014 using the keywords "case-control studies," "epidemiologic determinants," "risk factors," "menstrual cycle," "menstrual length," "menstrual character," and "endometriosis." We included case-control studies published in English that investigated cases of surgically confirmed endometriosis and examined the relationship between endometriosis risk and menstrual cycle. Eleven articles that met the inclusion criteria included data of 3392 women with endometriosis and 5006 controls. Fixed-effects and random-effects models were used for the evaluation. For the association of risk of endometriosis and menstrual cycle length shorter than or equal to 27 days (SEQ27) or length longer than or equal to 29 days (LEQ29), the odds ratio was 1.22 (95% confidence interval [CI]: 1.05-1.43) and 0.68 (95% CI: 0.48-0.96), respectively. In conclusion, this meta-analysis suggests that menstrual cycle length SEQ27 increase the risk of endometriosis and cycle length LEQ29 decrease the risk.

Endometriosis: a new cellular and molecular genetic approach for understanding the pathogenesis and evolutivity

Endometriosis is a benign disease with high prevalence in women of reproductive age estimated between 10 and 15% and is associated with considerable morbidity. Its etiology and pathogenesis are controversial but it is believed to involve multiple genetic, environmental, immunological, angiogenic, and endocrine processes. Altered expressions of growth factors, cytokines, adhesion molecules, matrix metalloproteinases, and enzymes for estrogen synthesis and metabolism have been frequently observed in this condition. The possibility of genetic basis of endometriosis is demonstrated in studies of familial disease, in which the incidence of endometriosis is higher for first-degree relatives of probands as compared to controls. This review describes mainly the cellular, cytochemical, cytogenetic, and molecular genetic features of endometriotic lesions and cultured endometriotic cells. In attempts to identify candidate gene (s) involved in the pathogenesis of endometriosis, a tissue-based approaches including conventional cytogenetics (RHG-banding), loss of heterozygosity (LOH), and comparative genomic hybridization (CGH) were employed. In addition to the karyotypic anomalies, consistent chromosome instability was confirmed by CGH and fluorescence in situ hybridization (FISH). The nature and significance of the molecular genetic aberrations in relation to the locations and function of oncogenes and tumor suppressor genes will be discussed. At last, a possible pathogenic role of embryonic duct remnants was observed in seven female fetal reproductive tract in endometriosis and may induce a discussion about the beginning of ovarian tumors and malignant proliferations.

Growth mechanisms of endometriotic cells in implanted places: a review

Endometriosis is a common gynecological disease defined by extrauterine growth of endometrial glands and stroma. A variety of theories have been proposed to account for the pathogenesis of this disease, including retrograde transplantation theory, metaplasia of coelomic epithelium, hematogenic and lymphogenic spread, and remnants of the Mŭllerian duct. However, the etiopathology of endometriosis is still obscure. In this article, we aim to summarize recent researches concerning the growth mechanisms of endometriotic cells in implanted sites systematically, including the adhesion, invasion, angiogenesis, proliferation, apoptosis of endometriotic cells, variations of the immune molecules and endometriotic cells themselves, which may provide clues for future researches in the pathogenesis of endometriosis.

Treatment of endometriosis with local acetylsalicylic acid injection: experimental study in rabbits

The objective of the present study was to estimate the effects of introduction of acetylsalicylic acid solution into peritoneal implants in autologous endometrium as a method for treating endometriosis. Forty adult female rabbits were subdivided into 4 groups of 10 rabbits each, and endometriosis was induced via autotransplantation of endometrial fragments into the peritoneal cavity. At 30 days after induction of endometriosis, all animals were randomly assigned to 1 of 2 protocols. In protocol 1, animals were evaluated at 24 hours after treatment; group 1 (control) received physiologic solution, and group 2 received acetylsalicylic acid. In protocol 2, animals were evaluated at 10 days after treatment, group 3 (control) and group 4 received acetylsalicylic acid. After measuring the lesion, the endometriotic focus was removed and prepared for mounting on slides for histologic analysis. Imaging software was used for analysis of the total remaining area of endometrial tissue. The affected area in acetylsalicylic acid-treated animals was smaller than that in control animals at 24 hours and 10 days after treatment; a significant difference was found between control and treated groups (p < .001). Statistical analysis comparing protocols 1 and 2 demonstrated no differences between controls groups or acetylsalicylic acid groups (p = .30), and no differences between times (p = .75). Acetylsalicylic acid solution led to less growth (or higher involution) of endometrial implants. Acetylsalicylic acid injected directly into endometriotic foci was effective in their destruction. This presents new perspectives for treatment of endometriosis and for clinical applications based on further clinical studies.

Endometriosis: current therapies and new pharmacological developments

Endometriosis is a chronic inflammatory condition that is responsive to management with steroids. The establishment of a steady hormonal environment and inhibition of ovulation can temporarily suppress ectopic implants and reduce inflammation as well as associated pain symptoms. In terms of pharmacological management, the currently available agents are not curative, and treatment often needs to be continued for years or until pregnancy is desired. Similar efficacy has been observed from the various therapies that have been investigated for endometriosis. Accordingly, combined oral contraceptives and progestins, based on their favourable safety profile, tolerability and cost, should be considered as first-line options, as an alternative to surgery and for post-operative adjuvant use. In situations where progestins and oral contraceptives prove ineffective, are poorly tolerated or are contraindicated, gonadotrophin-releasing hormone analogues, danazol or gestrinone may be used. Future therapeutic options for managing endometriosis must compare favourably against existing agents before they can be considered for inclusion into current practice. Finally, as reproductive prognosis is not ameliorated by medical treatment, it is not indicated for women seeking conception.

Multiple endometrial antigens are targeted in autoimmune endometriosis

Endometriosis is defined as the growth of endometrial glands and stroma in ectopic locations. Its aetiology is multifactorial, but autoimmunity has been shown to play a role in its onset and development. The present study aimed to investigate the presence of both IgG and IgM anti-endometrial antibodies in sera of endometriosis patients in comparison with age-matched controls, and to also investigate the cognate endometrial proteins involved. Sera from these groups were screened by western blot and immunohistochemistry. Thirteen out of the 40 sera tested were positive for IgG isotype, and 10/27 IgG negative patients were positive for IgM isotype. These findings indicate that endometrial antibodies of IgG and IgM classes could be detected in almost 60% of endometriosis patients. Of the various identified endometrial antigens, 30 and 45 kDa antigens were immunodominant in both IgG and IgM positive endometriosis patients. With immunohistochemistry, positive sera showed reactivity in luminal epithelium, glandular epithelium and stroma. These anti-endometrial antibodies might be partially responsible for failure of implantation leading to infertility. Identification of specific targets would be a help in understanding the pathophysiology of endometriosis, and would also help in setting up a non-invasive test for the diagnosis of endometriosis.

Endometriosis: epidemiology and aetiological factors

Estimates of the frequency of endometriosis vary widely. Based on the few reliable data, the prevalence of the condition can reasonably be assumed to be around 10%. Although no consistent information is available on the incidence of the disease, temporal trends suggest an increase among women of reproductive age. This could be explained-at least in part-by changing reproductive habits. Numerous epidemiological studies have indicated that nulliparous women and women reporting short and heavy menstrual cycles are at increased risk of developing endometriosis; data on other risk factors are less consistent. These epidemiological findings strongly support the menstrual reflux hypothesis. Additional evidence in favour of this theory includes the demonstration of viable endometrial cells in the menstrual effluent and peritoneal fluid, experimental implantation and growth of endometrium within the peritoneal cavity, observation of some degree of retrograde menstruation in most women undergoing laparoscopy during menses, and an association between obstructed menstrual outflow and endometriosis.

Medical management of endometriosis

Current approved medical therapies for endometriosis rely on drugs that suppress ovarian steroids and induce a hypoestrogenic state, which determines the atrophy of the ectopic endometrium. Gonadotropin-releasing hormone analogs such as danazol, progestogens and estrogen-progestin combinations have all proven effective in relieving pain and reducing the extent of endometriotic implants. However, symptoms often recur after discontinuation of therapy and hypoestrogenism-related side effects limit the long-term use of most medications. Recently, knowledge of the pathogenesis of endometriosis, particularly at the molecular level, has grown substantially, providing a rational basis for the development of new drugs with precise targets that may be safely administered over the long term.

Validation of rat endometriosis model by using raloxifene as a positive control for the evaluation of novel SERM compounds

Approximately 10% of women of reproductive age suffer from endometriosis, a potentially painful disease process and important cause of female infertility. Raloxifene, a commercially available SERM (selective estrogen receptor modulator) compound, used for the treatment of postmenopausal osteoporosis, has preclinically demonstrated its estrogen antagonist effect on uterine tissue in rats. There is potential that SERM compounds may become a viable treatment option for human endometriosis, although more investigation is needed. In this study, raloxifene was administered at various doses to determine the efficacy and an appropriate dose level for use as a positive control in a rat model of endometriosis. Prior to dose administration, all rats underwent a bilateral ovariectomy, autologous transplantation of uterine tissue onto the peritoneal surface of the abdominal wall, and implantation of a subcutaneous estrogen pellet (E2). Two separate postsurgical experiments were performed. In experiment 1, following a 4-wk recovery, the rats bearing implants were assigned to three groups: (1) removal of the E2 pellet and dosing vehicle only (n = 7); (2) E2 and vehicle (n = 6); and (3) E2 and raloxifene at 10.0 mg/kg (n = 6). In experiment 2, also following a 4-week recovery, the rats bearing implants were assigned to five groups (n = 8/group): (1) E2 and vehicle only; (2) E2 and raloxifene, 0.3 mg/kg/d; (3) E2 and raloxifene, 1.0 mg/kg/d; (4) E2 and raloxifene, 3.0 mg/kg/d; (5) E2 and raloxifene, 10.0 mg/kg/d. All rats were dosed orally BID for 14 d. At the end of the study, the implanted endometrium was remeasured and compared to the pretreatment measurement. The results from both studies demonstrated that Raloxifene at only one dose (10.0 mg/kg) displayed significant implant regression (p < .05). Subsequently, our rat endometriosis experimental model consistently uses the exogenous E2 pellet and raloxifene at 10 mg/kg, BID, as a positive control to help screen and compare novel SERM compounds.

Hormonal suppressive therapy for endometriosis may not improve patient health

OBJECTIVE

To critically examine the possible association between hormonal treatment of endometriosis and ovarian cancer.

RESULT(S)

The malignant potential of endometriosis has been suggested by several clinical studies. Although controversial, ovarian carcinoma of the endometrioid and clear cell subtypes has been associated with endometriosis, particularly among subjects with a longstanding disease. Furthermore, a significantly higher frequency of endometriosis has been found in patients undergoing surgery for endometrioid, clear cell, and mixed subtypes of ovarian carcinoma, as compared with the other subtypes. Changes in the genomic material in endometriotic implants were observed by many investigators in chromosomes 1, 5, 6, 7, 16, and 22 by several methods (fluorescent in situ hybridization, comparative genomic hybridization, and others). Because hormonal ablative treatments may suppress the normal, eukaryotic cells more than the aneuploid cells bearing chromosomal aberrations, it may increase the rate of dyskaryotic cells in the endometriotic implants, possibly augmenting the risk of malignant transformation. A recent published association between Danazol and ovarian cancer suggests that such a theoretical risk may occur.

CONCLUSION(S)

The hormonal ablative treatment of endometriosis may increase the risk of malignant transformation in the endometriotic implants by causing a negative selection and increasing the rate of dyskaryosis and loss of heterozygosity.

Endometriotic haptoglobin binds to peritoneal macrophages and alters their function in women with endometriosis

OBJECTIVE

To evaluate the effects of endometriotic haptoglobin on peritoneal macrophage function.

DESIGN

Prospective laboratory study.

SETTING

School of medicine.

PATIENT(S)

Twenty-three women with and without endometriosis.

INTERVENTION(S)

Peritoneal macrophages cultured without or with haptoglobin.

MAIN OUTCOME MEASURE(S)

Peritoneal macrophage haptoglobin immunoreactivity, adhesion, and interleukin-6 (IL-6) production.

RESULT(S)

In vivo, significantly more peritoneal macrophages from women with endometriosis bound haptoglobin and exhibited reduced adhesion compared to women without endometriosis. In vitro, haptoglobin treatment significantly decreased peritoneal macrophage adherence only in women without endometriosis; this effect was not seen in women with endometriosis, probably owing to in vivo haptoglobin saturation. Conversely, haptoglobin treatment robustly increased IL-6 production only by macrophages from women with endometriosis, suggesting differential immune response in these women.

CONCLUSION(S)

Endometriotic lesions synthesize and secrete a unique form of haptoglobin (endometriosis protein-I) that is up-regulated by IL-6. This study shows that haptoglobin adheres to peritoneal macrophages; decreases adhesion, which may influence phagocytic function; and up-regulates IL-6 production. Hence, a feed-forward loop is proposed whereby endometriotic lesion haptoglobin decreases macrophage phagocytic function while increasing IL-6 production, which in turn increases endometriotic haptoglobin and promotes establishment of endometriosis.

Endometriosis: novel etiopathogenetic concepts and clinical perspectives

OBJECTIVE

To discuss current ideas about therapy for endometriosis derived from new observations generated by using molecular biology techniques and in vivo animal models of disease.

METHOD(S)

The MEDLINE database was reviewed for English-language articles on new drugs that affect the endocrine or immunologic system, the possibility that endometriosis has multiple forms, and the association of endometriosis with cancer. Specific attention was given to in vivo studies in animals or humans.

CONCLUSION(S)

Among the novel potential candidate drugs, aromatase inhibitors and raloxifene should be considered for treatment of postmenopausal women with endometriosis. Notable observations have emerged from studies of immunomodulators and antiinflammatory agents in animal models of disease. These findings must be confirmed in women. The histogenesis of ovarian endometriomas is still unclear, thus limiting new experimental approaches to this form of disease. Given the low but established risk for malignant transformation of endometriosis, efforts should be directed toward identification of susceptibility loci for the disease and its potential transformation into cancer.

Signal transduction pathways involved in macrophage migration induced by peritoneal fluid chemotactic factors in stages I and II endometriosis

OBJECTIVE

To explore the role of G-protein coupled signaling pathways in activation of macrophage migration in endometriosis stages I and II.

DESIGN

Case controlled study.

SETTING

University hospital.

PATIENT(S)

Fifteen patients undergoing laparoscopy for elective sterilization (n = 5) or for diagnosis of endometriosis stages I and II associated with infertility (n = 10).

INTERVENTION(S)

Peritoneal fluid samples were collected during laparoscopy.

MAIN OUTCOME MEASURE(S)

Macrophage migration induced by peritoneal fluid from patients with endometriosis stages I and II (PF SI-II) and potential G-protein coupled receptors and second messengers involved in macrophage activation.

RESULT(S)

Potential G-protein coupled receptors and second messengers involved in macrophage activation were evaluated after incubation of U-937 cells differentiated into macrophages with inhibitors of phospholipase A and C, adenylate cyclase, and protein kinase A and C. Macrophage chemotactic activity induced by PF SI-II was inhibited in the presence of a phospholipase C and A2 inhibitor (IC50= 30 microM) and after treatment with myristoylated protein kinase C peptide inhibitor (50 nM). An increase in inositol phosphate (IP3) was also observed in macrophages exposed to PF SI-II. Activation of multiple G-proteins in macrophages was examined after exposure of cells to PF SI-II in the presence and absence of Bordettela pertussis and cholera toxins. No effect on macrophage migration was observed.

CONCLUSION(S)

Macrophage chemotaxis induced by PF SI-II appears to involve activation of pertussis toxin-insensitive G-protein coupled receptors in macrophages. Our data suggest that these events lead to subsequent activation of phospholipases followed by generation of IP3 and potential mobilization of intracellular Ca2+. Subsequent phosphorylation of target proteins by protein kinase C may regulate the chemotactic responses. The adenylate cyclase pathway does not appear to play a role in this process.

Paracrine regulation of matrix metalloproteinase expression in endometriosis

Following retrograde menstruation, shed endometrial tissue fragments attach to and invade the peritoneal surface to form established endometriotic lesions. With disease progression, the biochemically active lesions undergo remodeling and become fibrotic. Matrix metalloproteinase enzymes (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) play a significant role in normal endometrial remodeling during menses. Anomalous expression of MMPs and TIMPs has been identified in endometriotic lesions as compared to their highly regulated expression in eutopic endometrium. The paracrine mechanisms regulating misexpression of MMPs and TIMPs by endometriotic lesions are, however, not well defined. Misexpression of the MMPs and TIMPs may be due to innate anomalies in the eutopic endometrium from women with endometriosis, in the resident immune cells and peritoneal cells that juxtapose the ectopic endometrium, and/or numerous substances present in peritoneal fluid of women with endometriosis. The majority of MMPs are under strict transcriptional regulation. Steroid hormones and cytokines appear to act on the MMP promoter, either independently or in consort, to provide both positive and negative regulation of these genes. Misregulated expression of MMPs and TIMPs is associated with a more aggressive phenotype and a cascade of events facilitating peritoneal extracellular matrix degradation and establishment or remodeling of endometriotic lesions. The mechanisms by which MMP and TIMP expression are misregulated warrant further investigation as such information may provide insight into novel therapeutic modalities for endometriosis.

Differential regulation of matrix metalloproteinase-3 gene expression in endometriotic lesions compared with endometrium

In vivo levels of mRNA and the specificity of the extrauterine environment on matrix metalloproteinase (MMP)-3, MMP-2, and tissue inhibitor of matrix metalloproteinase (TIMP)-1 were evaluated in eutopic and ectopic endometrial tissue during the establishment of endometriosis in a rat model. Uteri and endometriotic implants were collected and frozen at 36 h, 2 wk, and 4 wk postsurgery to study in vivo mRNA levels. Intact uteri, uterine tissues implanted in the peritoneum or under the skin, and peritoneal adipose implants were collected at 2 wk, halved, and either frozen or cultured. Gene-specific reverse transcriptase-polymerase chain reaction was performed to detect and quantify MMP-2, MMP-3, and TIMP-1 mRNA levels. The peritoneal endometriotic implants progressed from avascularized implants, to vascularized red lesions, to well-established encapsulated cysts. In vivo, MMP-3 mRNA was detectable at all times in ectopic tissues but not in eutopic uterine tissues, whereas MMP-2 and TIMP-1 were ubiquitously expressed at all times in both tissues. In vitro, only MMP-3 mRNA levels were elevated in endometrial tissues collected from the intact uterine and from under the skin, at levels similar to in vivo endometriotic implant MMP-3. In conclusion, ectopic endometrial MMP-3 may participate in the process of invasion and tissue remodeling that is hypothesized to occur in the pathogenesis of endometriosis.

Endometrial anomalies in women with endometriosis

Endometriotic lesions are defined by extrauterine growth of endometrial glands and stroma. Retrograde menstruation with subsequent attachment, invasion, and neovascularization are believed to give rise to the endometriotic lesions. As most women exhibit some degree of retrograde menstruation, some other unidentified factor(s) must render certain women susceptible to attachment and growth of ectopic endometrial tissue. A variety of theories have been proposed to account for this susceptibility, including genetic predisposition, aberrant immunological response, and an altered peritoneal environment. Ectopic endometriotic lesions are histologically similar to their putative eutopic precursors, yet significant biochemical differences exist between these two tissues. Less information is available regarding differences between eutopic endometrium from women with or without endometriosis. This report describes anomalies in structure, proliferation, immune components, adhesion molecules, proteolytic enzymes and inhibitors, steroid and cytokine production and responsiveness, and gene expression and protein production that have been identified in eutopic endometrium from women with endometriosis.

Is endometriosis an endometrial disease?

Endometriosis is characterised by the presence of abnormally located tissue resembling the endometrium with glands and stroma. Several hypotheses have attempted to explain the development of such tissue. The most often cited theory, that of implantation, proposes that the physiological phenomenon of endometrial reflux in the fallopian tubes during menstruation may, in certain conditions, overcome local defense mechanisms, implant, and proliferate. The implantation theory does not explain why endometriosis will develop only in approximately 10-15% of women, while the reflux of endometrial tissue via the fallopian tubes during menstruation is a quasi-universal phenomenon. The endometrium of women affected by endometriosis could be abnormal compared with endometrium of healthy women. The abnormal endometrium could be able to protect itself from harmful effects of immune cells by expressing specific antigens, by harbouring a different immune cell population and by synthetizing and secreting immunosuppressive factors. Several others characteristic features of endometrium have been described in women with endometriosis: (1) production of its own estrogens in too heavy amount; (2) aptitude for setting up on peritoneum; (3) tendencies to proliferate and to invade tissue; (4) aggressiveness for the peritoneum; (5) auto-protection from physiological apoptosis; (6) abnormal expression of heat shock proteins; and (7) excessive angiogenesis.

Endometrial ability to implant in ectopic sites can be prevented by interleukin-12 in a murine model of endometriosis

Immune dysfunctions in endometriosis are widely documented but the effectiveness of immunotherapies for the management of the disease is still debated. Progress in this field has also been limited by the lack of an appropriate animal model of the disease. In this study, we created a model of endometriosis in immunocompetent mice to verify the ability of endometrium to implant in ectopic sites and to investigate the potential application of the cytokine interleukin (IL)-12 in preventing this ectopic implantation. Endometriotic lesions were induced in both C57BL/6 and BALB/c mice by inoculating syngenic endometrial fragments through a small laparotomic incision into the peritoneal space. All the animals challenged with syngenic endometrium showed evidence of peritoneal endometriosis at 3 weeks. Histologically, endometriotic lesions consisted of cystic endometrial glands surrounded by a stroma. Intraperitoneal injection of IL-12 was able to reduce total weight and total surface area of endometriotic lesions respectively of 77 and 61% in C57BL/6 and of 42 and 28% in BALB/c mice. These results demonstrate that IL-12 is able to induce a significant prevention of ectopic endometrial implantation in an in-vivo model of endometriosis. These findings support the possibility of using the immune system to generate novel therapies for the management of the disease.