Pathogenesis of endometriosis--current research

Endometriosis: Epidemiology, Classification, Pathogenesis, Treatment and Genetics (Review of Literature)

Endometriosis is a “mysterious” disease and its exact cause has not yet been established. Among the etiological factors, congenital, environmental, epigenetic, autoimmune and allergic factors are listed. It is believed that the primary mechanism of the formation of endometriosis foci is retrograde menstruation, i.e., the passage of menstrual blood through the fallopian tubes into the peritoneal cavity and implantation of exfoliated endometrial cells. However, since this mechanism is also observed in healthy women, other factors must also be involved in the formation of endometriosis foci. Endometriosis is in many women the cause of infertility, chronic pain and the deterioration of the quality of life. It also represents a significant financial burden on health systems. The article presents a review of the literature on endometriosis—a disease affecting women throughout the world.

Short treatment with antalarmin alters adrenal gland receptors in the rat model of endometriosis

Endometriosis is a chronic inflammatory disorder in which endometrial tissue is found outside the uterine cavity. Previous reports suggest that there is a dysregulation of the hypothalamic pituitary adrenal axis during the progression of endometriosis. Our previous report showed that a short-term treatment with antalarmin, a corticotrophin releasing hormone receptor type 1 (CRHR1) antagonist decreases the number and size of endometriotic vesicles in the auto-transplantation rat model of endometriosis. Our current goal was to examine the mRNA expression of intra-adrenal receptors to better understand the mechanisms of the hypothalamic pituitary adrenal (HPA) axis involvement in endometriosis. We used two groups of female rats. The first received sham surgery or endometriosis surgery before collecting the adrenals after 7 days of the disease progression. The second group of animals received endometriosis surgery and a treatment of either vehicle or antalarmin (20 mg/kg, i.p.) during the first 7 days after endometriosis induction and then the disease was allowed to progress until day 60. Rats with sham surgery served as controls. Results showed that the mRNA expression of the mineralocorticoid (MRC2) receptor was lower in the rats after 7 days of endometriosis surgery and in rats with endometriosis that received antalarmin. In addition, the CRHR1 was significantly elevated in animals that received antalarmin and this was counteracted by a non-significant elevation in CRHR2 mRNA. The glucocorticoid receptor mRNA within the adrenals was not affected by endometriosis or antalarmin treatment. This report is one of the first to explore intra-adrenal mRNA for receptors involved in the HPA axis signaling as well as in the sympatho-adrenal signaling, calling for additional research towards understanding the role of the adrenal glands in chronic inflammatory diseases such as endometriosis.

Evaluation of YB-1 levels in patients with endometriosis

OBJECTIVE

The objective of this study is the evaluation of serum YB-1 levels in the diagnosis of endometriosis.

STUDY DESIGN

Serum samples of 12 patients with histologically confirmed endometriosis and of 10 control patients were collected. Western blot analysis was used to assess serum YB-1 levels. Groups were compared with Student's t-test or, if not normally distributed, with the Mann-Whitney test. Sensitivity and specificity for the potential diagnostic performance of serum YB-1 were assessed by receiver operating characteristic (ROC) curves.

RESULTS

Serum YB-1 levels were significantly higher in patients with endometriosis (=0.004). The area under the curve was 0.867 (95% confidence interval 0.714-1.019) with sensitivity and specificity of 83.3% and 70% respectively.

CONCLUSIONS

Serum YB-1 levels in patients with endometriosis are significantly higher compared to control patients and may be used as a potential diagnostic biomarker for endometriosis.

Expression of DJ-1 and mTOR in eutopic and ectopic endometria of patients with endometriosis and adenomyosis

OBJECTIVE

Endometrial cells may aberrantly express molecules involved in invasion and migration, leading to endometriosis. The aim of this study was to investigate the expression of DJ-1 and phosphorylated mammalian target of rapamycin (p-mTOR) in ectopic and eutopic endometria of endometriosis and adenomyosis.

METHODS

Endometrial specimens were obtained from healthy non-menopausal women (n = 17) or patients with ovarian endometriotic cysts (n = 48) or adenomyosis (n = 30) during January 2011 to June 2012. The expressions of DJ-1 and p-mTOR were evaluated by immunohistochemistry and western blotting methods.

RESULTS

The expressions of DJ-1 and p-mTOR were significantly higher in the ectopic endometria than those in the eutopic endometria of endometriosis and adenomyosis patients or normal endometria (FDR < 0.05). DJ-1 expression was positively correlated with the p-mTOR expression no matter at endometriosis (r = 0.736, FDR < 0.001) or adenomyosis (r = 0.809, FDR < 0.001).

CONCLUSION

DJ-1 protein may be involved in endometrial cells proliferation, migration and angiogenesis by modulating the PI3K/Akt/p-mTOR signaling pathway, which provides an underlying theoretical target for endometriosis and adenomyosis.

CD44 antibodies and immune thrombocytopenia in the amelioration of murine inflammatory arthritis

Antibodies to CD44 have been used to successfully ameliorate murine models of autoimmune disease. The most often studied disease model has been murine inflammatory arthritis, where a clear mechanism for the efficacy of CD44 antibodies has not been established. We have recently shown in a murine passive-model of the autoimmune disease immune thrombocytopenia (ITP) that some CD44 antibodies themselves can induce thrombocytopenia in mice, and the CD44 antibody causing the most severe thrombocytopenia (IM7), also is known to be highly effective in ameliorating murine models of arthritis. Recent work in the K/BxN serum-induced model of arthritis demonstrated that antibody-induced thrombocytopenia reduced arthritis, causing us to question whether CD44 antibodies might primarily ameliorate arthritis through their thrombocytopenic effect. We evaluated IM7, IRAWB14.4, 5035-41.1D, KM201, KM114, and KM81, and found that while all could induce thrombocytopenia, the degree of protection against serum-induced arthritis was not closely related to the length or severity of the thrombocytopenia. CD44 antibody treatment was also able to reverse established inflammation, while thrombocytopenia induced by an anti-platelet antibody targeting the GPIIbIIIa platelet antigen, could not mediate this effect. While CD44 antibody-induced thrombocytopenia may contribute to some of its therapeutic effect against the initiation of arthritis, for established disease there are likely other mechanisms contributing to its efficacy. Humans are not known to express CD44 on platelets, and are therefore unlikely to develop thrombocytopenia after CD44 antibody treatment. An understanding of the relationship between arthritis, thrombocytopenia, and CD44 antibody treatment remains critical for continued development of CD44 antibody therapeutics.

Hepatocyte nuclear factor (HNF)-1β and its physiological importance in endometriosis

Endometriosis is associated with pelvic pain and female infertility. Endometriosis induces inflammation and is vulnerable to oxidative stress damage. To update and summarize the literature concerning the mechanisms that serve to protect genomic DNA from the oxidative damage, the present study reviews the English-language literature for biochemical studies on the transcription factor hepatocyte nuclear factor (HNF)-1β target genes. Findings demonstrated that retrograde flow of the menstrual blood might give rise to endometriosis. Iron may have a significant impact on endometriosis gene expression. HNF-1β regulates tissue-specific gene expression in endometriosis, as well as the expression of several genes, including CD44v9, which binds several molecules, including hyaluronan, epidermal growth factor receptor (EGFR), leukemia-associated Rho-guanine nucleotide exchange factor (LARG), IQ motif containing GTPase activating protein 1 (IQGAP1), macrophage migration inhibitory factor (MIF), major histocompatibility complex, class II invariant chain (CD74), cystine transporter subunit (xCT), Fas and extracellular matrix (ECM) proteins. The CD44v9 system is involved in cell migration, growth, survival, anti-apoptosis, immune response and anti-oxidative stress through maintaining higher levels of antioxidants. HNF-1β may serve to alleviate damage and promote survival of cells experiencing stress by upregulating antioxidant protein expression. This review expands current knowledge on the molecular mechanisms underlying the oxidative stress protection provided by HNF-1β and provides evidence that elevated HNF-1β activity might be associated with the CD44v9-dependent signaling cascades.

Cold-shock domain family member YB-1 expression in endometrium and endometriosis

BACKGROUND

The Y-box-binding protein (YB-1) is described as a potential oncogene highly expressed in tumors and associated with increased cell survival, proliferation, migration and anti-apoptotic signaling. The aim of our study was to examine the expression and role of YB-1 in human endometriosis (Eo) and its association with cell survival, proliferation and invasion.

METHODS

We analyzed the gene and protein expression levels of YB-1 by quantitative real-time RT-PCR and immunoassays, respectively, in peritoneal macrophages, ovarian endometrioma and eutopic endometrial tissues/cells derived from women with (n= 120) and without (n= 91) Eo. We also evaluated the functional consequences of YB-1 knockdown in the Z12 Eo cell line by measuring cell proliferation [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid cell proliferation assay], invasion (Matrigel invasion assay) and spontaneous and tumour necrosis factor (TNFα)-induced RANTES (regulated upon activation, normal T-cell expressed and secreted chemokine) expression and apoptosis (ELISA-based assay).

RESULTS

YB-1 gene and protein expression was statistically significantly higher in ovarian lesions, eutopic endometrium and peritoneal macrophages of patients with Eo in comparison with the control group. Interestingly, the strongest YB-1 expression was observed in the epithelial compartment of endometrial tissues. In the Z12 cell line, YB-1 knockdown resulted in significant cell growth inhibitory effects including reduced cell proliferation and increased rates of spontaneous and TNFα-induced apoptosis. Significantly, higher RANTES expression and decreased cell invasion in vitro were also associated with YB-1 inactivation.

CONCLUSION

High YB-1 expression could have an impact on the development and progression of Eo. This study suggests the role of YB-1 as a potential therapeutic target for Eo patients.

Silencing of cofilin-1 gene attenuates biological behaviours of stromal cells derived from eutopic endometria of women with endometriosis

BACKGROUND

Eutopic endometria with endometriosis (EMs) differ dramatically from normal endometria, physiologically and biochemically, yet the pathogenesis of EMs remains unclear. Cofilin-1 (CFL1), a critical modulator of the actin cystoskeleton, is associated with tumour progression, cell motility, cell adhesion, cell invasion and angiogenesis. Although eutopic endometria with EMs exhibit many malignant-like behaviours and a higher expression of CFL1 than normal endometria, the effects of CFL1 on the pathogenesis of EMs are unknown. The aim of this study was to explore the role of CFL1 expression in proliferation, apoptosis, adhesion, invasion, angiogenesis and ultrastructure of endometrial cells.

METHODS

We isolated and cultured stromal cells derived from the eutopic endometria of 30 patients with advanced ovarian EMs (ESCs, Stromal Cells of eutopic endometria in Endometriosis patients) and 30 control patients without EMs (NSCs, Stromal Cells of eutopic endometria in Non-endometriosis patients), and evaluated their proliferation, apoptosis, adhesion, invasion and expression of markers of adhesion, invasion and angiogenesis in vitro. In addition, these functions were examined after short hairpin RNA (shRNA) was used to silence the CFL1 gene in ESCs, and pEGFP-N1-CFL recombinant plasmid was transiently transfected into NSCs to up-regulate CFL1 expression.

RESULTS

Under basal conditions, CFL1 mRNA and protein were overexpressed in ESCs. Proliferation, adhesion, invasion and markers of adhesion, invasion and angiogenesis were enhanced in ESCs compared with NSCs; in contrast, the apoptosis rate was lower in ESCs than in NSCs. Silencing the CFL1 gene in ESCs markedly attenuated proliferation, adhesion, invasion and expression of the markers, but enhanced apoptosis. Conversely, up-regulation of CFL1 in NSCs increased proliferation, adhesion, invasion and expression of the markers but reduced apoptosis.

CONCLUSIONS

The overexpression of CFL1 in ESCs is associated with enhanced proliferation, adhesion, invasion and angiogenesis and reduced apoptosis in EMs. These malignant-like behaviours of ESCs in EMs can be attenuated by inducing CFL1 gene silencing with shRNA interference.

Cyclooxygenase-2 regulates survival, migration, and invasion of human endometriotic cells through multiple mechanisms

Endometriosis is a debilitating disease characterized by the presence of functional endometrial glandular epithelium and stroma outside the uterine cavity that affects up to 20% of women of child-bearing age. Cyclooxygenase-2 (COX-2), a rate-limiting enzyme in the biosynthesis of prostaglandin E(2) (PGE(2)), is highly expressed in endometriotic tissues and results in increased concentrations of peritoneal PGE(2) in women. In this study, we determined the expression of COX-2 protein in ectopic and eutopic endometria in humans and the role of COX-2 in endometriotic cell survival, migration, and invasion in humans. Our results indicate that COX-2 protein is abundantly expressed in ectopic endometria compared with eutopic endometria. Comparatively, expression of COX-2 protein is higher in eutopic endometria from women with endometriosis compared with women without endometriosis. Inhibition of COX-2 decreases survival, migration, and invasion of endometriotic cells that are associated with decreased production of PGE(2). Cell growth inhibitory effects of COX-2 inhibition/silencing are mediated through nuclear poly (ADP-ribose) polymerase-mediated apoptosis. Cell motility and invasion inhibitory effects of COX-2 inhibition/silencing are mediated through matrix metalloproteinase-2 and -9 activities. Interestingly, effects of COX-2 inhibition is more profound in endometriotic epithelial than in stromal cells. Furthermore, inhibition of COX-2 affects invasion rather than migration of endometriotic epithelial and stromal cells. It is the first evidence showing that inhibition of COX-2 decreases endometriotic epithelial and stromal cell survival, migration, and invasion in humans. Our results support the emerging concept that COX-2/PGE(2) promotes the pathophysiology and pathogenesis of endometriosis in humans.

Molecular profiling of experimental endometriosis identified gene expression patterns in common with human disease

OBJECTIVE

To validate a rat model of endometriosis using complimentary DNA (cDNA) microarrays by identifying common gene expression patterns between experimental and natural disease.

DESIGN

Autotransplantation rat model.

SETTING

Medical school department.

ANIMALS

Female Sprague-Dawley rats.

INTERVENTION(S)

Endometriosis was surgically induced by suturing uterine horn implants next to the small intestine's mesentery. Control rats received sutures with no implants. After 60 days, endometriotic implants and uterine horn were obtained.

MAIN OUTCOME MEASURE(S)

Gene expression levels determined by cDNA microarrays and real-time quantitative polymerase chain reaction (qPCR). The Cy5-labeled cDNA was synthesized from total RNA obtained from endometriotic implants. The Cy3-labeled cDNA was synthesized using uterine RNA from a control rat. Gene expression levels were analyzed after hybridizing experimental and control labeled cDNA to PIQOR (Parallel Identification and Quantification of RNAs) Toxicology Rat Microarrays (Miltenyi Biotec, Cologne, Germany) containing 1,252 known genes. The Cy5/Cy3 ratios were determined, and genes with >2-fold higher or <0.5-fold lower expression levels were selected. Microarray results were validated by QRT-PCR.

RESULT(S)

We observed differential expression of genes previously shown to be up-regulated in patients, including growth factors, inflammatory cytokines/receptors, tumor invasion/metastasis factors, adhesion molecules, and antiapoptotic factors.

CONCLUSION(S)

This study presents evidence in support of using this rat model to study the natural history of endometriosis and to test novel therapeutics for this incurable disease.

Identification of molecular markers for endometriosis in blood lymphocytes by using deoxyribonucleic acid microarrays

OBJECTIVE

To identify molecular biomarkers for endometriosis in peripheral blood lymphocytes by using DNA microarrays.

DESIGN

Case-control.

SETTING

Multicenter academic research programs.

PATIENT(S)

Premenopausal women with or without endometriosis, determined by obstetrics and gynecology specialists during surgery. Microarray analysis included six endometriosis patients and five controls; 15 endometriosis patients and 15 controls were analyzed by using real-time reverse-transcription polymerase chain reaction (RT-PCR). Patients with all disease stages were included.

INTERVENTION(S)

Peripheral blood samples were collected by venipuncture.

MAIN OUTCOME MEASURE(S)

The expression levels of mRNAs in blood lymphocytes from endometriosis patients and controls were compared with those of a standard total RNA. Gene expression data were validated by real-time RT-PCR analysis.

RESULT(S)

A gene selection program identified genes that were differentially expressed in samples from endometriosis patients. To validate the gene expression data, the nine most discriminatory genes were analyzed by real-time RT-PCR. Two of the nine genes identified, IL2RG and LOXL1, were shown to be significantly differentially expressed.

CONCLUSION(S)

This is the first report of genes that are differentially expressed in peripheral blood lymphocytes of patients with endometriosis, which may provide important clues regarding the pathogenesis of this disease. Moreover, they could be considered potential targets for noninvasive diagnostic assays for endometriosis and need to be validated in a larger population.