Endometriosis and Genetic Polymorphisms

Association of endometriosis with Sjögren's syndrome: Genetic insights (Review)

Patients with a history of endometriosis have an increased risk of developing various autoimmune diseases such as rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, multiple sclerosis and celiac disease. There is a potential association between endometriosis and an increased susceptibility for Sjögren's syndrome (SS). SS is a common chronic, inflammatory, systemic, autoimmune, multifactorial disease of complex pathology, with genetic, epigenetic and environmental factors contributing to the development of this condition. It occurs in 0.5‑1% of the population, is characterized by the presence of ocular dryness, lymphocytic infiltrations and contributes to neurological, gastrointestinal, vascular and dermatological manifestations. Endometriosis is an inflammatory, estrogen‑dependent, multifactorial, heterogeneous gynecological disease, affecting ≤10% of reproductive‑age women. It is characterized by the occurrence of endometrial tissue outside the uterine cavity, mainly in the pelvic cavity, and is associated with pelvic pain, dysmenorrhea, deep dyspareunia and either subfertility or infertility. It is still unclear whether SS appears as a secondary response to endometriosis, or it is developed due to any potential shared mechanisms of these conditions. The aim of the present review was to explore further the biological basis only of the co‑occurrence of these disorders but not their association at clinical basis, focusing on the analysis of the partially shared genetic background between endometriosis and SS, and the clarification of the possible similarities in the underlying pathogenetic mechanisms and the relevant molecular pathways.

Single nucleotide polymorphisms of Interleukin - 4, Interleukin-18, FCRL3 and sPLA2IIa genes and their association in pathogenesis of endometriosis

BACKGROUND

Endometriosis is a complex gynaecological disorder that contributes to infertility, dysmenorrhea, dyspareunia, and other chronic issues. It is a multifactorial disease involving genetic, hormonal, immunological and environmental components. Endometriosis's pathogenesis remains unclear.

AIM OF THE STUDY

was to analyse the polymorphisms in Interleukin 4, Interleukin 18, FCRL3 and sPLA2IIa genes to identify any significant association with the risk of endometriosis.

MATERIAL AND METHODS

This study evaluated the polymorphism of -590 C/T in interleukin- 4(IL-4) gene, C607A in Interleukin - 18(IL-18) gene, -169T > C in FCRL3 gene and 763 C > G in sPLA2IIa gene in women with endometriosis. The case-control study included 150 women with endometriosis and 150 apparently healthy women as control subjects. DNA was extracted from peripheral blood leukocytes and endometriotic tissue of cases and blood samples for controls and further analysed by PCR amplification and then sequencing was carried out to find the allele and genotypes of the subjects and then to analyse the relationship between the gene polymorphisms and endometriosis. To evaluate the association of the different genotypes, 95% confidence intervals (CI) were calculated.

RESULTS

Interleukin - 18 and FCRL3 gene polymorphisms of endometriotic tissue and blood samples of endometriosis (cases) showed significantly associated (OR = 4.88 [95% CI = 2.31-10.30], P > 0.0001) and (OR = 4.00 [95% CI = 2.2-7.33], P > 0.0001) when compared with normal blood samples. However, there was no significant difference in Interleukin - 4 and sPLA2IIa gene polymorphisms between control women and patients with endometriosis.

CONCLUSIONS

The present study suggests that the IL-18 and FCRL3 gene polymorphisms are associated with a higher risk for endometriosis, which delivers valuable knowledge of endometriosis's pathogenesis. However, a larger sample size of patients from various ethnic backgrounds is necessary to evaluate whether these alleles have a direct effect on disease susceptibility.

Artificial Intelligence Based Study Association between p53 Gene Polymorphism and Endometriosis: A Systematic Review and Meta-analysis

BACKGROUND

The P53 gene is critical to the onset and progression of cancers. Currently, relevant study findings indicate that the p53 gene may have a strong association with the risk of endometriosis, but these findings have not been united. To gather more statistically meaningful clinical data, we used meta-analysis to examine the relationship between the rs1042522 single nucleotide polymorphism of the tumor suppressor gene p53 and the incidence of endometriosis.

METHODS

Through a comprehensive literature survey of PubMed, MEDLINE, EMBASE, Springer, and Web of Science literature databases, we obtained a clinical control case study on the relationship between p53 gene polymorphism and the prevalence of female endometriosis and finally traced the relevant references included. The quality of the literature included in this study was evaluated, and Revman5.3 was used to complete the meta-analysis.

RESULTS

This research includes eight publications. The total number of cases in the study group was 1551, whereas the total number of cases in the control group was 1440. The findings of the sensitivity analyses of each omitted piece of the literature revealed no significant difference. The results of the meta-analysis showed that there were significant differences in the GG gene frequency (OR = 0.56, 95%CI (0.38, 0.92), P = 0.003), allele G (OR = 2.46, 95%CI (1.41,4.29), P = 0.002), and allele C (OR = 0.62, 95%CI (0.46, 0.84), P = 0.002) between the study group and the control group (P < 0.01), but there was no significant difference in the GC gene frequency (OR = 1.17, 95%CI (1.01,1.36), P = 0.03), and the CC gene frequency (OR = 1.25, 95%CI (0.85,1.82), P = 0.26) (P > 0.01).

CONCLUSION

Our study results show that there is a significant correlation between the single nucleotide of the p53 gene and the incidence rate of female endometriosis, in which the decrease of the GG gene frequency and the increase of allele C are likely to increase the risk of such diseases.

Effect of early inflammatory reaction on ovarian reserve after laparoscopic cystectomy for ovarian endometriomas

This study aimed to investigate the effect of early inflammatory reaction on ovarian reserve of patients with ovarian endometriomas after laparoscopic cystectomy. Our retrospective case series included 112 patients with ovarian endometriomas that underwent the laparoendoscopic single-site cystectomy. Interleukin-6 (IL-6), hs-CRP, tumour necrosis factor-α (TNF-α), interleukin-17A (IL-17A) and AMH level were detected during perioperative and postoperative period. In our study, ovarian endometriomas with low AMH group were found having higher level of IL-6 than the normal AMH group in the preoperative status. On the 3rd day after operation, the change of AMH level was inversely proportional to the IL-6 level. During the follow-up within one year, it was found that the bilateral nature of the cyst and the postoperative IL-6 increased level were the risk factors for AMH not returning to baseline level. Our results suggested that inflammatory reaction is indeed involved in the damage of ovarian reserve during laparoscopic cystectomy. Hence, the negative impact of inflammatory injury should be fully considered before operation, especially young women with bilateral ovarian endometriomas.Impact StatementWhat is already known on this subject? Ovarian reserve in women always was reduced after the laparoscopic cystectomy. It is reported that it may be related to the use of energy instruments, haemostatic methods or the size of cysts in minimally invasive surgery.What do the results of this study add? Inflammatory reaction is indeed involved in the damage of ovarian reserve during LESS cystectomy. Interleukin-6 (IL-6) may act as the most main inflammatory factor aggravating damage of the ovarian reserve. Moreover, increased IL-6 level after surgery and bilateral cyst burden are the two risk factors for AMH not returning to baseline level within one year after surgery.What are the implications of these findings for clinical practice and/or further research? In clinic, the negative impact of inflammatory injury on ovarian reserve should be fully considered before operation, especially young women with bilateral ovarian endometriomas. Moreover, this is also the clinical basis for further study on the mechanism of inflammatory ovarian injury or the method of blocking the inflammatory response to reduce the damage of ovarian reserve after surgery.

Molecular dysregulations underlying the pathogenesis of endometriosis

Endometriosis is a crippling disease characterized by the presence of endometrium-like tissue or scar outside the uterine cavity, commonly confined to the peritoneal and serosal surfaces of the pelvic organs. 10-15% of women in reproductive age are estimated to be affected by endometriosis. Most of these patients present with infertility and suffer from pelvic pain. The benign disease rarely progresses to malignancy. Regardless of its high prevalence, the pathogenesis of the disease is not fully understood. Treatment options for endometriosis are limited and are often based on a symptomatic approach. The unavailability of proper diagnostic approaches, fewer therapeutic options, and sparse understanding of molecular alterations are responsible for the continued disease burden. Exploring the molecular elements causing the pathogenesis of endometriosis may lead to a number of breakthroughs in the treatment of the illness, such as the discovery of new biomarkers for diagnosis and therapeutic targets that can be a guide to better prognosis and reduced recurrence. The goal of this review is to provide the reader a critical understanding of the disease by summarizing the genetic, immunological, hormonal, and epigenetic deregulations that support the molecular basis for development of endometriotic cyst, with a special focus on the study models needed to analyze these changes in the endometriotic microenvironment.

Genetic variants in the nucleotide excision repair genes are associated with the risk of developing endometriosis

Endometriosis is a major health issue among women of reproductive age. However, its etiology has not yet been completely understood. We investigated 10 single nucleotide polymorphisms from six novel nucleotide excision repair genes and the susceptibility to endometriosis. A total of 153 patients with endometriosis were recruited during 2000-2010 from central Taiwan. Pathological confirmation was necessary for all patients, and exclusion criteria included the presence of leiomyoma, adenomyosis, or cancer of the uterine, cervix, or ovary and a prescription of hormone therapy. Furthermore, a total of 636 age-matched individuals without endometriosis were recruited during the same time period from central Taiwan. The polymerase chain reaction coupled with restriction fragment length polymorphism methodology was applied for genotyping. The multivariate logistic regression analysis showed that subjects carrying the ERCC1 rs11615 TT (OR = 2.04, 95% CI = 1.36-3.41), ERCC2 rs1799793 AA (OR = 1.86, 95% CI = 1.14-3.11), and ERCC6 rs2228528 AA genotypes (OR = 1.79, 95% CI = 1.13-2.83) exhibited significantly increased risks of developing endometriosis compared with their counterparts carrying the wild-type genotypes. This study suggests that certain single nucleotide polymorphisms of nucleotide excision repair genes excision repair cross-complementation group 1 (ERCC1, ERCC2, and ERCC6) predispose women to the development of endometriosis.

Endometriosis Associated Infertility: A Critical Review and Analysis on Etiopathogenesis and Therapeutic Approaches

Endometriosis represents a frequently diagnosed gynecological affliction in the reproductive timespan of women, defined by symptoms ranging from pelvic pain to infertility. A complex interplay between the genetic profile, hormonal activity, menstrual cyclicity, inflammation status, and immunological factors define the phenotypic presentation of endometriosis. To date, imaging techniques represent the gold standard in diagnosing endometriosis, of which transvaginal ultrasonography and magnetic resonance imaging bring the most value to the diagnostic step. Current medical treatment options for endometriosis-associated infertility focus on either stimulating the follicular development and ovulation or on inhibiting the growth and development of endometriotic lesions. Techniques of assisted reproduction consisting of superovulation with in vitro fertilization or intrauterine insemination represent effective treatment alternatives that improve fertility in patients suffering from endometriosis. Emerging therapies such as the usage of antioxidant molecules and stem cells still need future research to prove the therapeutic efficacy in this pathology.

Polymorphisms and endometriosis: a systematic review and meta-analyses

BACKGROUND

Endometriosis is an estrogen-dependent gynecological disorder that affects at least 10% of women of reproductive age. It may lead to infertility and non-specific symptoms such as chronic pelvic pain. Endometriosis screening and diagnosis are difficult and time-consuming. Late diagnosis (with a delay ranging from 3.3 to 10.7 years) is a major problem and may contribute to disease progression and a worse response to treatment once initiated. Efficient screening tests might reduce this diagnostic delay. As endometriosis is presumed to be a complex disease with several genetic and non-genetic pathogenic factors, many researchers have sought to identify polymorphisms that predispose to this condition.

OBJECTIVE AND RATIONALE

We performed a systematic review and meta-analysis of the most regularly reported polymorphisms in order to identify those that might predispose to endometriosis and might thus be of value in screening.

SEARCH METHODS

The MEDLINE database was searched for English-language publications on DNA polymorphisms in endometriosis, with no date restriction. The PubTator text mining tool was used to extract gene names from the selected publications' abstracts. We only selected polymorphisms reported by at least three studies, having applied strict inclusion and exclusion criteria to their control populations. No stratification based on ethnicity was performed. All steps were carried out according to PRISMA guidelines.

OUTCOMES

The initial selection of 395 publications cited 242 different genes. Sixty-two genes (corresponding to 265 different polymorphisms) were cited at least in three publications. After the application of our other selection criteria (an original case-control study of endometriosis, a reported association between endometriosis and at least one polymorphism, data on women of reproductive age and a diagnosis of endometriosis in the cases established by surgery and/or MRI and confirmed by histology), 28 polymorphisms were eligible for meta-analysis. Only five of the 28 polymorphisms were found to be significantly associated with endometriosis: interferon gamma (IFNG) (CA) repeat, glutathione S-transferase mu 1 (GSTM1) null genotype, glutathione S-transferase pi 1 (GSTP1) rs1695 and wingless-type MMTV integration site family member 4 (WNT4) rs16826658 and rs2235529. Six others showed a significant trend towards an association: progesterone receptor (PGR) PROGINS, interCellular adhesion molecule 1 (ICAM1) rs1799969, aryl-hydrocarbon receptor repressor (AHRR) rs2292596, cytochrome family 17 subfamily A polypeptide 1 (CYP17A1) rs743572, CYP2C19 rs4244285 and peroxisome proliferator-activated receptor gamma (PPARG) rs1801282), and 12 showed a significant trend towards the lack of an association: tumor necrosis factor (TNF) rs1799964, interleukin 6 (IL6) rs1800796, transforming growth factor beta 1 (TGFB1) rs1800469, estrogen receptor 1 (ESR1) rs2234693, PGR rs10895068, FSH receptor (FSHR) rs6166, ICAM1 rs5498, CYP1A1 rs4646903, CYP19A1 rs10046, tumor protein 53 (TP53) rs1042522, X-ray repair complementing defective repair in Chinese hamster cells 1 (XRCC1) rs25487 and serpin peptidase inhibitor clade E member 1 (SERPINE1) rs1799889; however, for the 18 polymorphisms identified in the latter two groups, further studies of the potential association with the endometriosis risk are needed. The remaining five of the 28 polymorphisms were not associated with endometriosis: glutathione S-transferase theta 1 (GSTT1) null genotype, vascular endothelial growth factor alpha (VEGFA) rs699947, rs833061, rs2010963 and rs3025039.

WIDER IMPLICATIONS

By carefully taking account of how the control populations were defined, we identified polymorphisms that might be candidates for use in endometriosis screening and polymorphisms not associated with endometriosis. This might constitute the first step towards identifying polymorphism combinations that predispose to endometriosis (IFNG (CA) repeat, GSTM1 null genotype, GSTP1 rs1695, WNT4 rs16826658 and WNT4 rs2235529) in a large cohort of patients with well-defined inclusion criteria. In turn, these results might improve the diagnosis of endometriosis in primary care. Lastly, our present findings may enable a better understanding of endometriosis and improve the management of patients with this disease.

Meta-analysis of association between il-6-174 g/c polymorphism and female infertility related disorders

Female infertility continues to increase in prevalence annually and factors causing it need to be researched. As IL-6-174 G/C polymorphism is known to alter the plasma levels of IL-6, abnormal levels of IL-6 found in infertile females could be due to genetic reasons. With the understanding of the importance of IL-6 in reproductive physiology, several individual studies done so far to find the association of this polymorphism with female infertility related disorders were systematically combined for meta-analysis. Articles were searched using electronic data base sources and were included based on specific criteria. Finally, eight articles which includes polycystic ovarian syndrome (PCOS; n = 4), endometriosis (n = 3) and tubal damage (n = 1) were selected for the analysis. Results showed statistically significant heterogeneity across studies under the allele model (p < 0.0001, I² = 78 %) and dominant model (p < 0.00001, I² = 82%) but not under recessive model (p = 0.31, I² = 16%). This difference could be possibly due to variation in ethnicity, lifestyle, age or BMI related factors. The pooled odds ratio under the three genetic models were 0.87(CI = 0.75-1.02), 0.77 (CI = 0.63-0.94) and 1.05 (CI = 0.76-1.46) respectively. Sub group analysis showed statistical significant (P < 0.01) for PCOS under allele and dominant model, but not for endometriosis and tubal damage. By this meta-analysis, we can say that IL-6-174 G/C polymorphism can be considered as a potential genetic marker for PCOS but not for endometriosis and tubal damage disorders. However, more studies with adequate sample sizes are required to be done in endometriosis, tubal disease and other female infertility disorders to arrive at a definite conclusion.

Endometriosis research in the -omics era

Endometriosis is a pathological condition extensively studied, but its pathogenesis is not completely understood, since its pathophysiology stems from a broad spectrum of environmental influences and genetic factors. Moreover, the nature of this condition is heterogeneous and includes different anatomical entities. Scientists actively pursue discovery of novel biomarkers in the hope of better identifying susceptible individuals in early stages of the disease. High-throughput technologies have substantially revolutionized medical research and, as a first step, the advent of genotyping arrays led to large-scale genome-wide association studies (GWAS) and enabled the assessment of global transcript levels, thus giving rise to integrative genetics. In this framework, comprehensive studies have been conducted at multiple biological levels by using the "omics" platforms, thus allowing to re-examine endometriosis at a greater degree of molecular resolution. -Omics technologies can detect and analyze hundreds of markers in the same experiment and their increasing use in the field of gynecology comes from an urgent need to find new diagnostic and therapeutic tools that improve the diagnosis of endometriosis and the efficacy of assisted reproductive techniques. Proteomics and metabolomics have been introduced recently into the every day methodology of researchers collaborating with gynecologists and, importantly, multi-omics approach is advantageous to gain insight of the total information that underlies endometriosis, compared to studies of any single -omics type. In this review, we expect to present multiple studies based on the high-throughput-omics technologies and to shed light in all considerable advantages that they may confer to a proper management of endometriosis.

The Pathogenesis of Endometriosis: Molecular and Cell Biology Insights

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

Inflammatory cytokine profile of co‑cultivated primary cells from the endometrium of women with and without endometriosis

Endometriosis is a chronic gynecological disorder defined as the presence of endometrial tissue within extra-uterine sites. The primary symptoms are infertility and chronic pain. The inflammatory environment and aberrant immune responses in women with endometriosis may be directly associated with the initiation and progression of endometriotic lesions. In the present study, the secretion of inflammatory cytokines was evaluated in cultures of primary endometrial cells (ECs) isolated from the endometrium of women with and without endometriosis. The presence of endometriotic cells leads to alterations in the secretory profile of healthy ECs. The expression of the inflammatory cytokines interleukin (IL)‑6 and IL‑8 was significantly increased in endometriotic and co‑cultured cells compared with healthy ECs. IL‑6 expression was strongly correlated with IL‑8 expression in endometriotic cells. IL‑1β expression was increased on day 10 of co‑culture to 48.30 pg/ml and may be associated with the long‑term co‑culture, rather than IL‑6 and IL‑8 expression. IL‑6 expression was strongly correlated with cell number, whereas IL‑8 expression was moderately correlated with cell number. Additionally, it was observed that co‑cultured cells exhibited a different population of cells, with expression of the mesenchymal stem cell marker cell surface glycoprotein MUC18, indicating a putative role of endometrial mesenchymal stem cells in the secretion of cytokines and disease development. These results indicate a predominant role of primary endometriotic cells in the secretion of cytokines, which contributes to the disrupted peritoneal and endometrial environment observed in the women with endometriosis.

The Impact of FSHR Gene Polymorphisms Ala307Thr and Asn680Ser in the Endometriosis Development

Endometriosis is an estrogen-dependent inflammatory disease that affects a large number of women in reproductive age. Follicle-stimulating hormone (FSH) plays a role in steroidogenesis and acts through a transmembrane glycoprotein, FSH receptor (FSHR). Polymorphisms in FSHR gene were previously associated with variability in FSH serum level and reproductive outcomes, but its relation with endometriosis has not been clarified and demonstrated conflicting results, ranging from strong links to no association to endometriosis. Inspired by these findings, we aimed to investigate the influence of FSHR Ala307Thr and Asn680Ser polymorphisms in the risk of endometriosis development and/or progression and the status of fertility in 352 women with endometriosis and 510 fertile controls. Single-marker analysis revealed no significant difference for both Ala307Thr and Asn680Ser polymorphisms between overall endometriosis and control group. However, when the endometriosis group was subdivided according to fertility status and disease stage, a positive association was found between 680Ser/Ser or GG genotype of the Asn680Ser polymorphism and fertile women with endometriosis (p = 0.004). Combined alleles of FSHR polymorphisms revealed that "GG/307Ala680Ser" was more frequently found in fertile women with endometriosis (haplotype frequency of 45.4% in fertile women with endometriosis and 38.3% in controls, p = 0.041). The combined alleles of FSHR polymorphisms disclosed that "GG/307Ala680Ser" was more frequently found in fertile women with endometriosis (haplotype frequency of 45.4% in fertile women with endometriosis and 38.3% in controls, p = 0.049), while "GA/307Ala680Asn" haplotype was less frequently found in endometriosis group (haplotype frequency of 6.5% in cases and 11.9% in controls, p = < 0.001), regardless of fertility status and stage of the disease. The findings suggest that 680Ser-Ser/GG genotype and "GG/307Ala680Ser" haplotype increase the risk of endometriosis in fertile women, while "GA/307Ala680Asn" haplotype decreases the risk of endometriosis development and progression.

Recent Advances in Molecular Genetics of Endometriosis

Endometriosis (MIM 131200) is a prevalent and complex gynecological disease polygenically inherited with multifactorial pathogenesis. It is increasingly recognized as a major women's health issue. Endometriosis is characterized by the presence of endometrial-like tissue in sites outside the uterus, mainly the pelvic peritoneum, ovaries and rectovaginal septum causing severe dysmenorrhoea, dyspareunia, chronic pelvic pain and subfertility. Recent advances in molecular technologies have provided many evidences about the underlying biological events that are likely to be involved in the development of endometriosis. Different chromosomal regions, genes and other molecules, such as microRNAs, have been identified as potentially involved in endometriosis pathogenesis. Moreover, genome-wide analyses of endometriosis have showed novel molecular signatures or individual genes that had not been previously associated with the disease. The goal of these studies is to provide information that might, in turn, lead to new therapies. In this review, some previous studies were updated supporting the polygenic/multifactorial inheritance and the association with malignant neoplasias. We have also emphasized the importance of identifying the causative genes and determining novel diagnostic and predictive biomarkers.

The role of IL‑16 gene polymorphisms in endometriosis

Endometriosis is one of the most common gynecological diseases affecting up to 10% of the female population of childbearing age and a major cause of pain and infertility. It is influenced by multiple genetic, epigenetic and environmental factors. Interleukin-16 (IL-16) is a proinflammatory cytokine playing a pivotal role in many inflammatory and autoimmune diseases as well as in the pathogenesis of endometriosis. The aim of the present study was to evaluate the association of two IL-16 gene single nucleotide polymorphisms (SNPs), rs4072111 and rs11556218, with the risk of endometriosis in women from Greece as well as to gain insight about the structural consequences of these two exonic SNPs regarding development of the disease. A total of 159 women with endometriosis (stages I–IV) hospitalized for endometriosis, diagnosed by laparoscopic intervention and histologically confirmed, and 146 normal controls were recruited and genotyped. Subjects were genotyped using a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) strategy. A significant association was detected regarding the GG and GT genotype as well as 'G' allele of rs11556218 in patients with endometriosis. The rs4072111 SNP of the IL-16 gene was not found to be associated with an increased susceptibility to endometriosis either for all patients (stages I–IV) or for stage III and IV of the disease only. Our results demonstrated that rs11556218 is associated with endometriosis in Greek women, probably by resulting in the aberrant expression of IL-16, as suggested by the bioinformatics analysis conducted on the SNP-derived protein sequences, which indicated a possible association between mutation and functional modification of Pro-IL-16.

The Association of Flap Endonuclease 1 Genotypes with the Susceptibility of Endometriosis

BACKGROUND/AIM

Flap endonuclease 1 (FEN1), a protein with multiple functions in genome stability maintenance, is important in cancer prevention. The two functional germline variants of FEN1, rs174538 and rs4246215, regarding cancer susceptibility have been reported in lung, breast, liver, esophageal, gastric, colorectal cancer, glioma and leukemia, but not endometriosis. In this study, we firstly aimed at evaluating the contribution of FEN1 genotypes to endometriosis risk in a representative Taiwan population.

MATERIALS AND METHODS

In total, 153 patients with endometriosis and 636 non-cancer healthy controls were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methodology.

RESULTS

The genotypes of FEN1 rs174538, but not those of rs4246215, were differently distributed between the endometriosis and control groups. In detail, the AA of FEN1 rs174538 genotypes were significantly less frequently found among endometriosis patients than among controls (odds ratio [OR]=0.43, 95% confidence interval [CI]=0.24-0.78, p=0.0125). The A allele at FEN1 rs174538 was also significantly less frequent among cases than controls (OR=0.65, 95%CI=0.50-0.86, p=0.0021). As for age of first menarche, those with first menarche at the age >12.8 carrying the FEN1 rs174538 AA genotype conferred lower OR of 0.29 (95%CI=0.11-0.78, p=0.0381) for endometriosis. Regarding the full pregnancy status, those without having had a full-term pregnancy carrying the FEN1 rs174538 AA genotype were of lower risk (ORs=0.12, 95%CI=0.03-0.53, p=0.0050).

CONCLUSION

The FEN1 rs174538 A allele is a novel protective biomarker for endometriosis and this genotype may have interactions with age- and hormone-related factors on the development of endometriosis.

The role of gene polymorphisms in endometriosis

Endometriosis is a benign gynecologic disorder, affecting up to 10% of women, characterized by the presence of functional endometrial tissue at ectopic positions generally within the peritoneum. It is a heritable condition influenced by multiple genetic and environmental factors, with an overall heritability estimated at approximately 50%. In this study, we investigated whether single nucleotide polymorphisms (SNPs) rs7521902, rs10859871 and rs11031006, mapping to WNT4, VEZT and FSHB genetic loci, respectively, are associated with risk for endometriosis in a Greek population. This study included 166 women with histologically confirmed endometriosis diagnosed through surgery and 150 normal controls. Genotyping of the rs7521902, rs10859871 and rs11031006 SNPs was performed with Taqman primer/probe sets. A significant association was detected with the AC genotype of rs7521902 (WNT4) in patients with stage III and IV disease only. Evidence for association with endometriosis was also found for the AC genotype of the rs10859871 of VEZT. Notably, a significant difference in the distribution of the AG genotype and the minor allele A of FSHB rs11031006 SNP was found between the endometriosis patients and controls. We found a genetic association between rs11031006 (FSHB) SNP and endometriosis. WNT4 and VEZT genes constitute the most consistently associated genes with endometriosis. In the present study, an association of rs7521902 (WNT4) and rs10859871 (VEZT) was confirmed in women with endometriosis at the genotypic but not the allelic level.

The association between interleukin-4 -590C/T genetic polymorphism, IL-4 serum level, and advanced endometriosis

Aim of the study

Aim of the study was to investigate interleukin (IL)-4 serum levels in patients with advanced endometriosis and whether IL-4 promoter region (-590C/T) genetic polymorphism is involved in genetic susceptibility to endometriosis.

Material and methods

IL-4 serum levels and IL-4 -590C/T genetic polymorphism were determined for 80 patients with advanced endometriosis and 85 healthy fertile women using a multiplex cytokine kit, with a Luminex 200 system; high molecular weight genomic DNA was extracted from peripheral blood leukocytes, and further analyzed by PCR amplification and restriction fragment length polymorphism (PCR-PFLP). The relationship between IL-4 serum levels, genotypes and haplotypes and the presence of endometriosis was explored.

Results

Interleukin 4 serum levels were significantly higher in the endometriosis group compared to controls (138,459 compared to 84,710, p < 0.001). No significant difference was observed in IL-4 serum levels between genotypes. There were no differences in IL-4 -590C/T genotypes and allele frequencies between control women and patients with endometriosis (χ² = 0.496, and χ² = 0.928, OR = 1.3636, CI: 0.725-2.564).

Conclusions

The results suggest that in patients with advanced stages of endometriosis there is a higher serum level of IL-4, and that this value, or the presence of the disease, is not influenced by the presence of IL-4 -590C/T genetic polymorphism.

DNA methylation in endometriosis (Review)

Endometriosis is defined by the presence and growth of functional endometrial tissue, outside the uterine cavity, primarily in the ovaries, pelvic peritoneum and rectovaginal septum. Although it is a benign disease, it presents with malignant characteristics, such as invasion to surrounding tissues, metastasis to distant locations and recurrence following treatment. Accumulating evidence suggests that various epigenetic aberrations may play an essential role in the pathogenesis of endometriosis. Aberrant DNA methylation represents a possible mechanism repsonsible for this disease, linking gene expression alterations observed in endometriosis with hormonal and environmental factors. Several lines of evidence indicate that endometriosis may partially be due to selective epigenetic deregulations influenced by extrinsic factors. Previous studies have shed light into the epigenetic component of endometriosis, reporting variations in the epigenetic patterns of genes known to be involved in the aberrant hormonal, immunologic and inflammatory status of endometriosis. Although recent studies, utilizing advanced molecular techniques, have allowed us to further elucidate the possible association of DNA methylation with altered gene expression, whether these molecular changes represent the cause or merely the consequence of the disease is a question which remains to be answered. This review provides an overview of the current literature on the role of DNA methylation in the pathophysiology and malignant evolution of endometriosis. We also provide insight into the mechanisms through which DNA methylation-modifying agents may be the next step in the research of the pharmaceutical treatment of endometriosis.

Vascular endothelial growth factor pathway in endometriosis: genetic variants and plasma biomarkers

OBJECTIVE

To study single nucleotide polymorphisms (SNPs) involved in angiogenesis (VEGF, PLGF, VEGFR1, VEGFR2, HIF-1α) and plasma levels of the corresponding proteins (VEGF, PLGF, sVEGFR1, sVEGFR2) in women with and without endometriosis.

DESIGN

Allele frequencies of vascular endothelial growth factor (VEGF) pathway SNPs and plasma levels of the corresponding proteins were investigated in patients with endometriosis and in controls.

SETTING

University hospital.

PATIENT(S)

Samples of DNA from 1,931 Caucasian patients were included (1,109 patients with endometriosis and 822 controls). An additional study group included 973 DNA samples from volunteers, self-reported to be healthy without laparoscopic evaluation.

INTERVENTION(S)

Women who underwent a laparoscopy for subfertility and/or pain and healthy volunteers without laparoscopic evaluation.

MAIN OUTCOME MEASURE(S)

Functional SNPs of the VEGF, VEGFR1, VEGFR2, HIF-1α genes and Hap Map tagging SNPs of the PLGF gene were genotyped by using iPLEX technology on a Sequenom MassArray and TaqMan SNP Genotyping Assay. The VEGF levels were determined in ethylenediaminetetraacetic acid plasma samples by using Bio-Plex Protein Array System. PLGF, sVEGFR1, and sVEGFR2 levels were measured in ethylenediaminetetraacetic acid plasma samples by using ELISA Quantikine kits.

RESULT(S)

A significant association was found between the rs2268613 polymorphism in the PLGF gene and PLGF plasma levels. In all study subjects, women with the AA variant of the rs2268613 PLGF gene had significantly lower PLGF plasma levels (median [interquartile range] 9.36 [8.19-10.43] pg/mL) than those with the AG variant (12.1 [11.81-20.84] pg/mL; P(a)=.0085, P(b)=.04), both before and after multiple testing. Plasma levels of VEGF were elevated in endometriosis patients (especially in minimal-mild endometriosis during the menstrual cycle phase) compared with laparoscopic controls but had a moderate diagnostic performance (area under the curve, 0.73) in this discovery dataset. At a cut-off plasma level of VEGF >3.88 pg/mL, minimal-mild stages of endometriosis were diagnosed with a sensitivity of 74% and a specificity of 80% during the menstrual phase of cycle. The associations between the presence of endometriosis and SNPs in PLGF (rs2268614), HIF-1α (rs11549465), and VEGFR1 (rs9582036) genes lost statistical significance after multiple testing.

CONCLUSION(S)

Genetic variants in the PLGF rs2268613 gene may influence plasma levels of the corresponding protein. Plasma levels of VEGF were elevated in endometriosis patients compared with controls. The associations between the presence of endometriosis and SNPs in PLGF (rs2268614), HIF-1α (rs11549465), and VEGFR1 (rs9582036) genes lost statistical significance after multiple testing.

A current view of the role of epigenetic changes in the aetiopathogenesis of endometriosis

The purpose of the study was to examine the role of epigenetic changes in the aetiopathogenesis of endometriosis. The analysis and review of the relevant current literature in English language related to the role of epigenetic changes in the aetiopathogenesis of endometriosis. Epigenetic changes are common denominators for hormonal, immunological and inflammatory aberrations which play a key role in the aetiopathogenesis of endometriosis. Many internal and external factors may cause the different running of the epigenetic mechanism. As yet fully unknown genetic factors may increase the sensitivity of the epigenetic mechanism to various internal and external factors. The breakdown of epigenetic regulation is the main factor initiating the pathogenetic mechanisms for endometriosis formation.

Replication and meta-analysis of previous genome-wide association studies confirm vezatin as the locus with the strongest evidence for association with endometriosis

STUDY QUESTION

Is it possible to replicate the genetic association of single nucleotide polymorphisms (SNPs) rs13394619, rs4141819, rs7739264, rs17694933 and rs10859871 in five genetic loci previously identified as associated with endometriosis in an Italian Caucasian population?

SUMMARY ANSWER

SNP rs10859871 near the vezatin (VEZT) gene was found to be significantly associated with endometriosis in general while SNPs rs17694933 and rs4141819 were associated with Stage III/IV and ovarian disease, respectively.

WHAT IS KNOWN ALREADY

Endometriosis represents a complex disease in which the phenotypic manifestations are influenced by both genetic and environmental factors. Recent genome-wide association studies (GWASs) have allowed to identify some SNPs associated with the predisposition to the disease. A meta-analysis published in 2014 combined results from GWAS and replication studies showing that of the nine loci found to be associated with the disease in at least one of the studies, six (rs7521902, rs1270667, rs13394619, rs7739264, rs1537377 and rs10859871) remained genome-wide significant while two others (rs1250248 and rs4141819) showed borderline genome-wide significant association with more severe disease.

STUDY DESIGN, SIZE, DURATION

Allele frequencies of selected SNPs (rs13394619, rs4141819, rs7739264, rs17694933 and rs10859871) were investigated in 305 women with laparoscopically proven endometriosis, 285 laparoscopic controls and 2425 healthy, blood donor controls from the general population. A meta-analysis with previous data was also conducted.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 590 women who underwent endoscopic surgery were enrolled in the study and a blood sample was collected. After DNA extraction, genotype was obtained using Taq-Man pre-designed assay. Genotype data from healthy blood donor women were obtained from an existing genotype bank.

MAIN RESULTS AND THE ROLE OF CHANCE

A statistically significant association with endometriosis was found for SNP rs10859871, close to the VEZT gene, compared with both general population [odds ratio (OR) = 1.43, 95% confidence interval (CI): 1.20-1.71, P = 6.9 × 10(-5)] and laparoscopic controls (OR = 1.58, 95% CI: 1.24-2.02, P = 2.1 × 10(-4)). Meta-analysis with previous data confirmed the rs10859871 SNP as that with the strongest evidence for association with endometriosis (OR = 1.19, 95% CI: 1.15-1.24, P = 7.9 × 10(-20)). A further meta-analysis conducted using data from Stage III-IV endometriosis resulted in stronger genome-wide significant effect sizes for four out of the five SNPs tested.

LIMITATIONS, REASONS FOR CAUTION

The inability to confirm all previous demonstrated associations considering all stages of endometriosis may be due to a lack of statistical power and differences in the definition of cases included.

WIDER IMPLICATIONS OF THE FINDINGS

The associations with the SNPs identified so far have been obtained with a relatively small sample size supporting a limited heterogeneity across the various datasets. This represents an important advance in the identification of genetic markers of this disease.

STUDY FINDING/COMPETING INTERESTS

No funding to declare. The authors have no competing financial interests in relation to the content of this research paper.

Association study between CYP17 gene polymorphism and endometriosis risk: a meta-analysis

The cytochrome P450 subfamily 17 (CYP17) gene T > C polymorphism is associated with endometriosis risk. However, studies on the association between the genotyping of MspA1 polymorphism in the 5'-untranslated region of the CYP17 gene and endometriosis risk have reported controversial results. The aim of the present study was to obtain a more precise estimate of the relationship of CYP17 gene polymorphism with endometriosis risk. Relevant articles published up to April 2014 were obtained from Pubmed, Embase, and Cochrane Central electronic databases. Case-control studies about the association between CYP17 gene polymorphisms and endometriosis were selected. Eligible data were extracted by two independent reviewers. The strength of the association between CYP17 and endometriosis was assessed by pooled odds ratios (OR) with 95% confidence intervals (CI). Eligible case-control studies involving 1000 cases and 1167 controls were analyzed from 280 studies. The pooled results showed no association between the CYP17 gene T > C polymorphism and endometriosis risk in the overall population (CC vs TT: OR = 0.92, 95% CI = 0.52-1.61, P = 0.762; TC vs TT: OR = 1.01, 95% CI = 0.72-1.42, P = 0.949; dominant model: OR = 0.94, 95% CI = 0.64-1.39, P = 0.763; recessive model: OR = 0.93, 95% CI = 0.64-1.35, P = 0.712). In the subgroup analysis based on ethnicity, no significant association was found in Asians, Caucasians and mixed population under a recessive model (Asians: OR = 0.76, 95% CI = 0.53-1.07, P = 0.118; Caucasians: OR = 2.47, 95% CI = 0.45-13.66, P = 0.300; mixed population: OR = 1.40, 95% CI = 0.65-3.02, P = 0.712). In conclusion, the meta-analysis suggested that the CYP17 gene polymorphism was not associated with endometriosis risk. Considering the limited sample size and ethnicity included in our meta-analysis, an updated meta-analysis needs to be conducted when larger and more well-designed studies are published.

Ovarian endometriosis signatures established through discovery and directed mass spectrometry analysis

New molecular information on potential therapeutic targets or tools for noninvasive diagnosis for endometriosis are important for patient care and treatment. However, surprisingly few efforts have described endometriosis at the protein level. In this work we enumerate the proteins in patient endometrium and ovarian endometrioma by extensive and comprehensive analysis of minute amounts of cryosectioned tissues in a three-tiered mass spectrometric approach. Quantitative comparison of the tissues revealed 214 differentially expressed proteins in ovarian endometrioma and endometrium. These proteins are reported here as a resource of SRM (selected reaction monitoring) assays that are unique, standardized, and openly available. Pathway analysis of the proteome measurements revealed a potential role for Transforming growth factor β-1 in ovarian endometriosis development. Subsequent mRNA microarray analysis further revealed clear ovarian endometrioma specificity for a subset of these proteins, which was also supported by further in silico studies. In this process two important proteins emerged, Calponin-1 and EMILIN-1, that were additionally confirmed in ovarian endometrioma tissues by immunohistochemistry and Western blotting. This study provides the most comprehensive molecular description of ovarian endometriosis to date and researchers with new molecular methods and tools for high throughput patient screening using the SRM assays.

Screening of a panel of steroid-related genes showed polymorphisms of aromatase genes confer susceptibility to advanced stage endometriosis in the Taiwanese Han population

OBJECTIVE

To establish a multilocus model for studying the effect of steroid-related genes on advanced stage endometriosis.

MATERIALS AND METHODS

A total of 121 patients with advanced stage endometriosis and 171 control women were included. Eighteen single-nucleotide polymorphisms (SNPs) from nine genes (HSD17B1, HSD17B2, HSD17B5, HSD17B6, CYP17, CYP19, ERα, ERβ, and PGR) were genotyped using the TaqMan assays. Logistic regression models were used to evaluate the genetic effects, with adjustment for other covariates.

RESULTS

Only the presence of the mutant CYP19 (aromatase gene) was associated with a significantly increased risk of endometriosis after adjusting for age, BMI, and parity (p = 0.002, OR = 2.69; 95% CI = 1.44-5.02). No association was ascertained between the other investigated SNPs and endometriosis.

CONCLUSION

Polymorphisms of the aromatase gene confer susceptibility to advanced stage endometriosis in the Taiwanese Han population.

Ser312Gly Polymorphism of the HSD17β1 Gene is not Associated with Endometriosis in Brazilian Patients

Purpose

The aim of this study was to determine whether a polymorphism of the HSD17β1 gene (rs605059), involved in estrogen synthesis, is associated with endometriosis in Brazilian patients.

Methods

A case-control study was conducted in 231 women. All patients in the case group had a histopathological diagnosis of endometriosis. Genomic DNA was genotyped by nested-PCR, followed by digestion of the PCR product with the enzyme BstUI.

Results

The frequencies of the genotypes detected in the case and control groups were 22.4% GG, 52.2% AG and 25.4% AA; and 31.3% GG, 49.3% AG and 19.4% AA, respectively, with no significant difference between groups. The prevalence of the G allele was 48.5% and 56% in the case and control groups, respectively. No significant difference in genotype or allele frequency was detected between the different stages of endometriosis (p>0.05).

Conclusions

The results suggested that the Ser312Gly polymorphism of the HSD17β1 gene is not associated with endometriosis in Brazilian patients.

Gene polymorphisms in female reproduction

This chapter presents an overview of the gene polymorphisms underlying the functions of ovarian receptors and their clinical implications in the female fecundity. A selection of genetic studies revealing significant associations between receptor polymorphisms, gene mutations, and some pathological conditions (i.e., female infertility, premature ovarian failure, polycystic ovary syndrome, endometriosis) are reviewed.

Genetic Polymorphisms Associated with Endometriosis in Pakistani Women

Background

Endometriosis is a common disease that causes pain and infertility. The heritable predisposition toward endometriosis motivates an interest to identify the genes and genomic variants involved in the pathogenesis of endometriosis. Both genetic and environmental factors contribute to this disease. Here we investigated in Pakistani women the association of endometriosis and single nucleotide polymorphisms (SNP) in genes previously identified in the development of this disease.

Methods

DNA samples from 52 genetically unrelated endometriosis subjects with endometriosis and 52 randomly selected controls were analyzed by direct sequencing to determine polymorphisms in four genes. These included estrogen receptor alpha (ESR1) (rs2234693 C/T, rs9340799 G/A SNP), estrogen receptor beta (ESR2) (rs4986938 G/A SNP), progesterone receptor (PGR) (rs1042838 G/T, rs10895068 G/A SNPs) and interleukin 10 (IL10) (rs1800871 C/T, rs1800872 C/A and rs1800896 G/A SNPs).

Results

The allele A at −592, T at −819 and G at −1080 of IL10 and all of the SNPs studied at ESR2 and PGR show strong, statistically significant associations with the disease. However, the genetic variation at ESR1 was distributed similarly among cases and control groups.

Conclusion

These findings suggest that the functional promoter polymorphism of the IL10 gene, identified by the “ATG” genotype, may contribute to the risk of endometriosis. Genetic variants of ESR2 and PGR gene may also be a risk factor as well as influence the fertility status of patients with endometriosis.

Interplay between Misplaced Müllerian-Derived Stem Cells and Peritoneal Immune Dysregulation in the Pathogenesis of Endometriosis

In the genetic regulation of Müllerian structures development, a key role is played by Hoxa and Wnt clusters, because they lead the transcription of different genes according to the different phases of the organogenesis, addressing correctly cell-to-cell interactions, allowing, finally, the physiologic morphogenesis. Accumulating evidence is suggesting that dysregulation of Wnt and/or Hox genes may affect cell migration during organogenesis and differentiation of Müllerian structures of the female reproductive tract, with possible dislocation and dissemination of primordial endometrial stem cells in ectopic regions, which have high plasticity to differentiation. We hypothesize that during postpubertal age, under the influence of different stimuli, these misplaced and quiescent ectopic endometrial cells could acquire new phenotype, biological functions, and immunogenicity. So, these kinds of cells may differentiate, specializing in epithelium, glands, and stroma to form a functional ectopic endometrial tissue. This may provoke a breakdown in the peritoneal cavity homeostasis, with the consequent processes of immune alteration, documented by peripheral mononuclear cells recruitment and secretion of inflammatory cytokines in early phases and of angiogenic and fibrogenic cytokines in the late stages of the disease.

Environmental Influences on the Development of Endometriosis

Purpose

Several environmental toxicants (ETs), including dioxins and dioxin-like compounds (DLCs), perfluorochemicals, organochlorine pesticides, phthalates, and heavy metals (especially cadmium with its estrogen-like properties in animal models) have been investigated as possibly being related to endometriosis.

Methods

Systematic review of pertinent literature.

Results

DLCs have been the most investigated ETs. DLCs are persistent organic pollutants with highly toxic potential and include three types of compounds: polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) or furans, and polychlorinated biphenyls (PCBs). The most toxic is 2, 3, 7, 8- tetrachlorodibenzo-p-dioxin (TCDD). The connection mechanism between dioxins and endometriosis is still unclear. However, dioxins and DLCs are endocrine-disrupting compounds that can affect the pathobiology of endometriosis at multiple levels. Part of the dioxin and DLCs toxic effects can be accounted for by their interaction with the aryl hydrocarbon receptor (AhR). It has been proposed that dioxin can initiate or promote endometriosis by means of interaction with estrogen receptors or by suppressing the expression of progesterone receptors. Furthermore, TCDD alters the expression of cytokines and growth factors, remodeling enzymes and cytochrome P450 expression and activity.

Conclusions

Studies in rhesus models have revealed a correlation between dioxin exposure and endometriosis. However, evidence from epidemiologic studies is inconclusive.

Replication of endometriosis-associated single-nucleotide polymorphisms from genome-wide association studies in a Caucasian population

STUDY QUESTION

Is it possible to replicate the previously identified genetic association of four single-nucleotide polymorphisms (SNPs), rs12700667, rs7798431, rs1250248 and rs7521902, with endometriosis in a Caucasian population?

SUMMARY ANSWER

A borderline association was observed for rs1250248 and endometriosis (P = 0.049). However, we could not replicate the other previously identified endometriosis-associated SNPs (rs12700667, rs7798431 and rs7521902) in the same population.

WHAT IS KNOWN ALREADY

Endometriosis is considered a complex disease, influenced by several genetic and environmental factors, as well as interactions between them. Previous studies have found genetic associations with endometriosis for SNPs at the 7p15 and 2q35 loci in a Caucasian population.

STUDY DESIGN, SIZE, DURATION

Allele frequencies of SNPs were investigated in patients with endometriosis and controls.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Blood samples and peritoneal biopsies were taken from a Caucasian female population consisting of 1129 patients with endometriosis and 831 controls. DNA was extracted for genotyping. The study was performed at a University hospital and research laboratories.

MAIN RESULTS AND THE ROLE OF CHANCE

A weak association with endometriosis (all stages) was observed for rs1250248 (P = 0.049). No significant associations were observed for the SNPs rs12700667, rs7798431 and rs7521902. A non-significant trend towards the association of rs1250248 with moderate/severe endometriosis was observed (odds ratio 1.18, 95% confidence interval 0.97-1.44).

LIMITATIONS, REASONS FOR CAUTION

The inability to confirm all previous findings may result from differences between populations and type II errors.

WIDER IMPLICATIONS OF THE FINDINGS

Our result demonstrates the difficulty of identifying common genetic variants in complex diseases.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grants from the Karolinska Institutet and Stockholm City County/Karolinska Institutet (ALF), Stockholm, Sweden, Swedish Medical Research Council (K2007-54X-14212-06-3, K2010-54X-14212-09-3), Stockholm, Sweden, Leuven University Research Council (Onderzoeksraad KU Leuven), the Leuven University Hospitals Clinical Research Foundation (Klinisch onderzoeksfonds) and by the National Scientific Foundation (Fonds voor Wetenschappelijk Onderzoek, FWO). The authors have no conflict of interest.

A search to identify genetic risk factors for endometriosis

PROBLEM

To search for molecular markers of endometriosis the following polymorphisms: p53 codon 72 Pro (apoptosis), TNF alpha-308 (inflammation), VEGF-1164AA (angiogenesis), and SOD2 (oxidative stress) were investigated.

METHOD OF STUDY

Forty-two women-24 with surgically proven endometriosis and 18 with no endometriosis found at the time of laparoscopy-had buccal swabs taken for DNA analyses of 4 gene polymorphisms including p53codon72, TNF-308 G/A, VEGF-1154G/A, SOD Ala16Val DNA. The frequencies of genotypes and alleles of these polymorphisms were compared between women with and without endometriosis.

RESULTS

No specific gene mutation differences for the four genes tested nor differences in the frequencies of heterozygous and homozygous mutations were found between patients with endometriosis and controls. In addition, no differences in allelic frequencies of the four genetic polymorphisms were observed between patients with endometriosis and control.

CONCLUSION

Endometriosis is not associated with gene mutations for p53codon72, TNF-308 G/A, VEGF-1154G/A, SOD Ala16Val.

Functional analyses of endometriosis-related polymorphisms in the estrogen synthesis and metabolism-related genes

Endometriosis is determined by genetic factors, and the prevalence of genetic polymorphisms varies greatly depending on the ethnic group studied. The objective of this study was to investigate the relationship between single nucleotide polymorphisms (SNPs) of 9 genes involved in estrogen biosynthesis and metabolism and the risks of endometriosis. Three hundred patients with endometriosis and 337 non-endometriotic controls were recruited. Thirty four non-synonymous SNPs, which change amino acid residues, were analyzed using matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). The functions of SNP-resulted amino acid changes were analyzed using multiple web-accessible databases and phosphorylation predicting algorithms. Among the 34 NCBI-listed SNPs, 22 did not exhibit polymorphism in this study of more than 600 Taiwanese Chinese women. However, homozygous and heterozygous mutants of 4 SNPs - rs6165 (genotype GG+GA, 307(Ala/Ala)+307(Ala/Thr)) of FSHR, rs 6166 (genotype GG+GA, 680(Ser/Asn)+680(Ser/Ser)) of FSHR, rs2066479 (genotype AA+AG, 289(Ser/Ser)+289(Ser/Gly)) of HSD17B3 and rs700519 (genotype TT+TC, 264(Cys/Cys)+264(Cys/Arg)) of CYP19, alone or in combination, were significantly associated with decreased risks of endometriosis. Bioinformatics results identified 307(Thr) of FSHR to be a site for O-linked glycosylation, 680(Ser) of FSHR a phosphorylated site by protein kinase B, and 289(Ser) of HSD17B3 a phosphorylated site by protein kinase B or ribosomal protein S6 kinase 1. Results of this study suggest that non-synonymous polymorphisms of FSHR, HSD17B3 and CYP19 genes may modulate the risk of endometriosis in Taiwanese Chinese women. Identification of the endometrosis-preferential non-synonymous SNPs and the conformational changes in those proteins may pave the way for the development of more disease-specific drugs.

Insights into Assessing the Genetics of Endometriosis

Endometriosis is a complex disease arising from the interplay between multiple genetic and environmental factors. The genetic variants potentially underlying the hereditary component of endometriosis have been widely investigated through hypothesis-driven candidate gene studies, an approach that generally has proven to be inherently difficult and problematic for a number of reasons. Recently, through major collaborative efforts in the endometriosis research field, hypothesis-free genome-wide approaches have started to provide new insights into potential pathways leading to development of endometriosis, as well as highlighting the phenotypic heterogeneity of the condition. This review summarizes the most recent studies investigating the genetic variation contributing to endometriosis, with a particular focus on genome-wide approaches, and discusses promising future directions of genetic research.

Tissue remodeling and nonendometrium-like menstrual cycling are hallmarks of peritoneal endometriosis lesions

We identified differentially expressed genes comparing peritoneal endometriosis lesions (n = 18), eutopic endometrium (n = 17), and peritoneum (n = 22) from the same patients with complete menstrual cycles using microarrays (54 675 probe sets) and immunohistochemistry. Peritoneal lesions and peritoneum demonstrated 3901 and 4973 significantly differentially expressed genes compared to eutopic endometrium, respectively. Peritoneal lesions significantly revealed no correlation with a specific menstrual cycle phase by gene expression and histopathology, exhibited low expressed proliferation genes, and constant levels of steroid hormone receptor genes. Tissue remodeling genes in cytoskeleton, smooth muscle contraction, cellular adhesion, tight junctions, and O-glycan biosynthesis were the most significant to lesions, including desmin and smooth muscle myosin heavy chain 11. Protein expression and location of desmin, alpha-actin, and h-caldesmon in peritoneal lesions discriminated between smooth muscle hyperplasia and metaplasia. Peritoneal lesions demonstrate no menstrual cycle phasing but constant steroid hormone receptor expression where a slow but steady growth is linked with tissue remodeling. Our study contributes to the molecular pathology of peritoneal endometriosis and will help to identify clinical targets for treatment and management.

MUC2 polymorphisms are associated with endometriosis development and infertility: a case-control study

BACKGROUND

Mucins are highly glycosylated proteins protecting and lubricating epithelial surface of respiratory, gastrointestinal and reproductive tracts. Members of the mucin protein family have been suggested to play an important role in development of endometriosis and infertility. This study investigates genetic association of mucin2 (MUC2) with the risk of endometriosis and endometriosis-related infertility.

METHODS

This case-control study was conducted at China Medical University Hospital, with 195 endometriosis patients and 196 healthy controls enrolled. Genotyping of six SNPs (rs2856111, rs11245936, rs10794288, rs10902088, rs7103978 and rs11245954) within MUC2 gene were performed by using Taqman genotyping assay; individual SNP and haplotype associations with endometriosis and endometriosis-related infertility were assessed by χ² test.

RESULTS

Endometriosis patients exhibit significantly lower frequency of the rs10794288 C allele, the rs10902088 T allele and the rs7103978 G allele (P = 0.030, 0.013 and 0.040, respectively). In addition, the rs10794288 C allele and the rs10902088 T allele were also less abundant in patients with infertility versus fertile ones (P = 0.015 and 0.024, respectively). Haplotype analysis of the endometriosis associated SNPs in MUC2 also showed significantly association between the most common haplotypes and endometriosis or endometriosis-related infertility.

CONCLUSIONS

MUC2 polymorphisms, especially rs10794288 and rs10902088, are associated with endometriosis as well as endometriosis-related infertility. Our data present MUC2 as a new candidate involved in development of endometriosis and related infertility in Taiwanese Han women.

A novel gene-environment interaction involved in endometriosis

OBJECTIVE

To establish a well-defined cohort for genetic epidemiology studies of endometriosis and conduct a pilot study to confirm validity using existing data associated with endometriosis.

METHODS

Between January and May 2010, a nested cohort within a population-based biobank was established in Marshfield, Wisconsin, USA. The inclusion criteria were women who had laparoscopy or hysterectomy. Fifty-one pleiotropic genetic polymorphisms and other established risk factors, such as smoking status and body mass index, were compared between endometriosis cases and controls.

RESULTS

From the existing biobank, 796 cases and 501 controls were identified, and 259 women with endometriosis were enrolled specifically for the nested cohort within this biobank. A single nucleotide polymorphism in the MMP1 gene significantly differed between cases and controls only when stratified by smoking status. Minor allele frequency was higher in control women who smoked than in women with endometriosis who smoked (55.5% versus 45.5%, χ(2)=8.2, P=0.017); the inverse relationship was found in non-smoker control women.

CONCLUSIONS

Women with endometriosis were successfully recruited to participate in a general biobank, and a novel gene-environment interaction was identified. The findings suggest that important potential genetic associations may be missed if gene-environment interactions with known epidemiologic risk factors are not considered.

Effects of polymorphisms in gonadotropin and gonadotropin receptor genes on reproductive function

Gonadotropins, the action of which is mediated at the level of their gonadal receptors, play a key role in sexual development, reproductive functions and in metabolism. The involvement of the gonadotropins and their receptor genotypes on reproductive function are widely studied. A large number of gonadotropins and their receptors gene polymorphisms are known, but the only one considerable as a clear, absolute genetic marker of reproductive features or disfunctions is the FSHR Asn680Ser polymorphism, since it modulates ovarian response to FSH. The aim of these studies would to be the prediction of the genetic causes of sex-related diseases to enable a customized clinical setting based on individual response of patients undergoing gonadotropin stimulation. In this review we discuss the latest information about the effects of polymorphisms of the gonadotropins and their receptor genes on reproductive functions of both male and female, and discuss their patho-physiological implications.

Single-nucleotide polymorphisms in the lysyl oxidase-like protein 4 and complement component 3 genes are associated with increased risk for endometriosis and endometriosis-associated infertility

This study was conducted to assess genetic associations with endometriosis in a Puerto Rican population. Statistically significant differences in the allelic frequencies and genotype distribution of genetic variants in lysyl oxidase-like protein 4 (LOXL4) and complement component 3 (C3) were documented in patients with endometriosis-associated infertility versus controls, and in patients with endometriosis versus controls, respectively. In women who have the risk genotype at both single-nucleotide polymorphisms, the estimated risk for endometriosis nearly doubled.