Expression and localisation of osteopontin and prominin-1 (CD133) in patients with endometriosis

Effects of Progestin on Modulation of the Expression of Biomarkers in Endometriosis

BACKGROUND

Our study aimed to examine the osteopontin (OPN) serum levels and tissue expression of CD44 and OPN in endometriosis-affected women both undergoing and not undergoing progestin treatment, and also to determine their involvement in the pathogenesis of endometriosis.

METHODS

Using an ELISA kit, we evaluated the OPN serum levels of healthy and endometriosis-affected women both undergoing and not undergoing progestin treatment. Immunohistochemical (IHC) analyses were used to assess the endometriotic tissue expressions of CD44 and OPN.

RESULTS

There were statistically significant higher OPN serum levels in the healthy control group compared to the women with endometriosis. Furthermore, there were higher OPN serum levels in the endometriosis-affected women undergoing the progestin treatment, but the difference did not reach statistical significance. In comparison to OPN, CD44 expression was significantly higher in all the endometriotic tissue glands and stroma, regardless of the patient's treatment status. Compared to the group receiving therapy, the OPN levels were higher in the endometriosis group not receiving therapy. OPN's robust cytoplasmic expression seemed to be associated with the non-treatment group.

CONCLUSION

Endometriosis, CD44, and OPN appear to be closely related. This study suggests that endometriosis that has not been treated has an immunological profile distinct to endometriosis that has received treatment.

Osteopontin Splicing Isoforms Contribute to Endometriotic Proliferation, Migration, and Epithelial-Mesenchymal Transition in Endometrial Epithelial Cells

Osteopontin (OPN) isoforms, including OPNb and OPNc, promote malignancy and may contribute to the pathogenesis of endometriosis, a benign disorder with multiple characteristics resembling malignant tumors. In our experiments, OPNb and OPNc were significantly overexpressed in both endometriosis and adenomyosis compared to the normal endometrium. Upregulation of CD44v and the epithelial-mesenchymal transition (EMT) process was also present in endometriotic lesions. Overexpression of OPNb and OPNc splicing variants in endometriotic cells evoked morphological changes, actin remodeling, cell proliferation, cell migration, and EMT through binding OPN ligand receptors CD44 and αvβ3, subsequently activating the PI3K and NF-ĸB pathways. We elucidated the causal role of OPN splice variants in regulating endometriotic cell growth, which may promote the development of OPN-targeted therapies for patients suffering from endometriotic disorders.

Controlling Semi-Invasive Activity of Human Endometrial Stromal Cells by Inhibiting NF-kB Signaling Pathway Using Aloe-emodin and Aspirin

Background:

Inflammation and its master regulator, Nuclear Factor-kB (NF-kB), have been implicated in the development of endometriosis. Inhibition of NF-kB pathway using small molecules ameliorated disease progression and reduced the lesion size; nevertheless, the underlying mechanism is not fully understood. Therefore, this study, is an attempt to assess whether inhibiting NF-kB signaling by aloe-emodin (AE) or aspirin (Asp), as anti-inflammatory compounds, can suppresses the invasive activity of human endometrial stromal cells at stage IV endometriosis.

Methods:

The eutopic and healthy endometrial biopsies from a total of 8 infertile women with confirmed endometriosis and 8 women without endometriosis were digested and the single cells were cultured. Gene and protein markers of proliferation, migration, adhesion, and invasion of eutopic endometrial stromal cells (EuESCs) with and without treatment with AE or Asp, as well as control endometrial stromal cells (CESCs) was analyzed using q-PCR and immunofluorescence staining, respectively. Comparison between groups was performed using one-way ANOVA and the Bonferroni post hoc and p≤0.5 was considered statistically significant.

Results:

There was an association between NF-kB overexpression and higher proliferation/adhesion capacity in EuESCs. EuESCs (at stage IV endometriosis) displayed no invasive and migratory behaviors. Pre-treatment of EuESCs with AE or Asp significantly attenuated NF-kB expression and reduced proliferative, adhesive, invasive, and migratory activity of endometrial cells (p≤0.5).

Conclusion:

Eutopic endometrial stromal cells seem to have a semi-invasive activity which is largely suppressed by AE or Asp. It can be suggested that both Asp and AE (as potent NF-kB inhibitors) can be used as a supplement in conventional endometriosis treatments.

Hypoxia‑induced lactate dehydrogenase A protects cells from apoptosis in endometriosis

The pathological expression and function of lactate dehydrogenase A (LDHA), a key enzyme that converts pyruvate into lactic acid during glycolysis, remains unknown in endometriosis. In the present study, LDHA expression in tissue samples was determined by immunohistochemistry. To examine whether LDHA was induced by hypoxia, primary cultured endometrial stromal cells (ESCs) and glandular epithelial Ishikawa cells were exposed to 1% O₂ (hypoxia) or 21% O₂ (normoxia). Cellular functions were assessed by flow cytometry, Transwell and Cell Counting Kit-8 assays in LDHA-silenced ESCs and Ishikawa cells. Mitochondrial functions were evaluated using mitochondrial membrane potential JC-1 staining, reactive oxygen species flow cytometric analysis and ATP detection. Additionally, lactic acid production was examined and western blotting was used to evaluate the expression levels of proteins associated with apoptosis, cell cycle and glycolysis, as well as regulatory proteins involved in epithelial-mesenchymal transformation and glycolytic pathways. LDHA was localized to endometrial glandular cells and stromal cells. However, LDHA protein expression was higher in endometriotic lesions compared with that in normal and eutopic endometria. LDHA expression levels in ectopic glandular cells were higher during the proliferative stage compared with during the secretory stage. Hypoxia treatment of Ishikawa cells and ESCs markedly induced the mRNA and protein expression of LDHA. Silencing of LDHA expression in Ishikawa cells and THESC cells significantly promoted impaired mitochondrial function and apoptosis while inhibiting migration and glycolysis. However, it had no obvious effect on proliferation. In conclusion, the present study revealed that LDHA was highly expressed in endometriotic tissues, where it may serve a notable role in the occurrence and development of endometriosis.

Osteopontin Regulates Endometrial Stromal Cell Migration in Endometriosis through the PI3K Pathway : Osteopontin Regulates Endometrial Cell Migration in Endometriosis

Endometriosis is generally characterized as a tumor-like disease because of its potential for distant metastasis and local tissue invasion, while whether osteopontin (OPN) plays a role in the pathogenesis of endometriosis has not been thoroughly investigated. We investigated the expression of OPN, urokinase plasminogen activator (uPA), phosphatidylinositol 3 kinase (PI3K), and phospho-PI3 kinase (p-PI3K) in endometrial stromal cells (ESCs). The serum concentration of OPN was determined by enzyme-linked immunosorbent assays (ELISA). OPN was downregulated to explore the corresponding change of uPA, p-PI3K, F-actin, and α-tubulin. The expression of OPN, uPA, PI3K, and p-PI3K was evaluated by western blot and quantitative real-time PCR (RT-qPCR) and the expression of F-actin and α-tubulin was confirmed by immunofluorescence assay. The proliferation and migration abilities of ESCs were investigated by CCK8, transwell, and wound scratch assays. Endometrial OPN, p-PI3K, and uPA expressions and serum OPN levels were increased in patients with endometriosis compared with the control. The expressions of p-PI3K, uPA, and α-tubulin were decreased by siRNA-OPN interference in ectopic ESCs. Activation and inhibition of the PI3K pathway apparently upregulate and downregulate uPA expression. Knockdown of OPN and inhibition of the PI3K pathway remarkably inhibited cell migration in ectopic ESCs. Meanwhile, activation of the PI3K pathway promoted the migration ability of ectopic ESCs. OPN may regulate the expression of uPA through the PI3K signal pathway to affect the migration ability of ESCs, indicating that OPN, uPA, and the PI3K pathway may be potential targets for interrupting development of endometriosis.

Plasma High Mobility Group Box 1 (HMGB1), Osteopontin (OPN), and Hyaluronic Acid (HA) as Admissible Biomarkers for Endometriosis

Identification of biomarkers for endometriosis is an unmet medical need that demands to be fulfilled. In this study, we first used a mouse model of endometriosis and evaluated the potential utility of select biomarkers based on serial observations. Since fibrosis is the end result of lesional development, we chose high mobility group box 1 (HMGB1), osteopontin (OPN), and hyaluronic acid (HA), all three of them have been well documented to be involved in endometriosis and fibrosis, as potential biomarkers. In addition, we performed immunohistochemistry analysis of HMGB1, OPN, and the receptors for HMGB1, such as toll-like receptor 4 (TLR4), nuclear factor κB (NF-κB), proliferating cell nuclear antigen (PCNA), interleukin-33 (IL-33), and receptor for advanced glycation endproducts (RAGE)–a pattern recognition receptor, with HMGB1 being its important ligand. We then evaluated the same set of putative markers in 30 women with ovarian endometriomas and 20 without endometriosis, and reevaluated the 3 plasma markers 3 months after the surgical removal of all visible endometriotic lesions. In mouse, the lesional staining levels of OPN, RAGE, and IL-33 were all significantly higher than that of normal endometrium, and increased progressively as lesions progressed. In contrast to HMGB1, TLR4, p-p65 and PCNA staining levels were decreased progressively. In humans, lesional staining levels of OPN correlated positively, while that of HMGB1 correlated negatively with the extent of fibrosis. All three plasma markers correlated positively with the extent of lesional fibrosis. Through this integrated approach, we identified plasma HMGB1, OPN and HA as promising admissible biomarkers for endometriosis.

Prominin-1 glycosylation changes throughout early pregnancy in uterine epithelial cells under the influence of maternal ovarian hormones

In preparation for uterine receptivity, the uterine epithelial cells (UECs) exhibit a loss of microvilli and glycocalyx and a restructuring of the actin cytoskeleton. The prominin-1 protein contains large, heavily glycosylated extracellular loops and is usually restricted to apical plasma membrane (APM) protrusions. The present study examined rat UECs during early pregnancy using immunofluorescence, western blotting and deglycosylation analyses. Ovariectomised rats were injected with oestrogen and progesterone to examine how these hormones affect prominin-1. At the time of fertilisation, prominin-1 was located diffusely in the apical domain of UECs and 147- and 120-kDa glycoforms of prominin-1 were identified, along with the 97-kDa core protein. At the time of implantation, prominin-1 concentrates towards the APM and densitometry revealed that the 120-kDa glycoform decreased (P<0.05), but there was an increase in the 97-kDa core protein (P<0.05). Progesterone treatment of ovariectomised rats resulted in prominin-1 becoming concentrated towards the APM. The 120-kDa glycoform was increased after oestrogen treatment (P<0.0001), whereas the 97-kDa core protein was increased after progesterone treatment (P<0.05). Endoglycosidase H analysis demonstrated that the 120-kDa glycoform is in the endoplasmic reticulum, undergoing protein synthesis. These results indicate that oestrogen stimulates prominin-1 production, whereas progesterone stimulates the deglycosylation and concentration of prominin-1 to the apical region of the UECs. This likely presents the deglycosylated extracellular loops of prominin-1 to the extracellular space, where they may interact with the implanting blastocyst.

Prominin-2 Prevents the Formation of Caveolae in Normal and Ovarian Hyperstimulated Pregnancy

During early pregnancy, uterine epithelial cells (UECs) become less adherent to the underlying basal lamina and are subsequently removed so the blastocyst can invade the underlying stroma. This process involves the removal of focal adhesions from the basal plasma membrane of UECs. These focal adhesions are thought to be internalized by caveolae, which significantly increase in abundance at the time of blastocyst implantation. A recent in vitro study indicated that prominin-2 prevents the formation of caveolae by sequestering membrane cholesterol. The present study examines whether prominin-2 affects the formation of caveolae and loss of focal adhesions in UECs during normal and ovarian hyperstimulation (OH) pregnancy in the rat. At the time of fertilization during normal pregnancy, prominin-2 is distributed throughout the basolateral plasma membrane. However, at the time of implantation and coincident with an increase in caveolae, prominin-2 is lost from the basal plasma membrane. In contrast, prominin-2 remains in the basolateral plasma membrane throughout OH pregnancy. Transmission electron microscopy showed that this membrane contained few caveolae throughout OH pregnancy. Our results indicate that prominin-2 prevents the formation of caveolae. We suggest the retention of prominin-2 in the basal plasma membrane during OH pregnancy prevents the formation of caveolae and is responsible for the retention of focal adhesions in this membrane, thereby contributing to the reduced implantation rate observed after such treatments.

Decreased zinc and increased lead blood levels are associated with endometriosis in Asian Women

Endometriosis is an inflammatory disease associated with multiple pathogenic factors and studies regarding roles of trace metals in endometriosis have been inconsistent and limited. The aim of this cross-sectional study was to compare the blood levels of miscellaneous trace metals measured by inductively coupled plasma mass spectrometry in infertile women with and without endometriosis. Zinc level is associated with declining odds (adjusted OR=0.39, 95% CI=0.18-0.88) of endometriosis. By contrast, lead level is associated with increasing odds (adjusted OR=2.59, 95% CI=1.11-6.06) of endometriosis. The cadmium levels were higher in women with endometriosis, but the aOR was not significant. Zinc has anti-inflammatory characteristics and regulates homeostasis of zinc-containing superoxide dismutase. High lead levels might induce reactive oxygen species and deplete antioxidant defense mechanisms. Further prospective study is needed to test for their causal associations.

Meta-signature of human endometrial receptivity: a meta-analysis and validation study of transcriptomic biomarkers

Previous transcriptome studies of the human endometrium have revealed hundreds of simultaneously up- and down-regulated genes that are involved in endometrial receptivity. However, the overlap between the studies is relatively small, and we are still searching for potential diagnostic biomarkers. Here we perform a meta-analysis of endometrial-receptivity associated genes on 164 endometrial samples (76 from 'pre-receptive' and 88 from mid-secretory, 'receptive' phase endometria) using a robust rank aggregation (RRA) method, followed by enrichment analysis, and regulatory microRNA prediction. We identify a meta-signature of endometrial receptivity involving 57 mRNA genes as putative receptivity markers, where 39 of these we confirm experimentally using RNA-sequencing method in two separate datasets. The meta-signature genes highlight the importance of immune responses, the complement cascade pathway and the involvement of exosomes in mid-secretory endometrial functions. Bioinformatic prediction identifies 348 microRNAs that could regulate 30 endometrial-receptivity associated genes, and we confirm experimentally the decreased expression of 19 microRNAs with 11 corresponding up-regulated meta-signature genes in our validation experiments. The 57 identified meta-signature genes and involved pathways, together with their regulatory microRNAs could serve as promising and sought-after biomarkers of endometrial receptivity, fertility and infertility.

Genetic risk factors for ovarian cancer and their role for endometriosis risk

OBJECTIVE

Several genetic variants have been validated as risk factors for ovarian cancer. Endometriosis has also been described as a risk factor for ovarian cancer. Identifying genetic risk factors that are common to the two diseases might help improve our understanding of the molecular pathogenesis potentially linking the two conditions.

METHODS

In a hospital-based case-control analysis, 12 single nucleotide polymorphisms (SNPs), validated by the Ovarian Cancer Association Consortium (OCAC) and the Collaborative Oncological Gene-environment Study (COGS) project, were genotyped using TaqMan® OpenArray™ analysis. The cases consisted of patients with endometriosis, and the controls were healthy individuals without endometriosis. A total of 385 cases and 484 controls were analyzed. Odds ratios and P values were obtained using simple logistic regression models, as well as from multiple logistic regression models with adjustment for clinical predictors.

RESULTS

rs11651755 in HNF1B was found to be associated with endometriosis in this case-control study. The OR was 0.66 (95% CI, 0.51 to 0.84) and the P value after correction for multiple testing was 0.01. None of the other genotypes was associated with a risk for endometriosis.

CONCLUSIONS

As rs11651755 in HNF1B modified both the ovarian cancer risk and also the risk for endometriosis, HNF1B may be causally involved in the pathogenetic pathway leading from endometriosis to ovarian cancer.

Evaluation of two endometriosis models by transplantation of human endometrial tissue fragments and human endometrial mesenchymal cells

BACKGROUND

The animal models of endometriosis could be a valuable alternative tool for clarifying the etiology of endometriosis.

OBJECTIVE

In this study two endometriosis models at the morphological and molecular levels was evaluated and compared.

MATERIALS AND METHODS

The human endometrial tissues were cut into small fragments then they were randomly considered for transplantation into γ irradiated mice as model A; or they were isolated and cultured up to fourth passages. 2×106 cultured stromal cells were transplanted into γ irradiated mice subcutaneously as model B. twenty days later the ectopic tissues in both models were studied morphologically by Periodic acid-Schiff and hematoxylin and eosin staining. The expression of osteopontin (OPN) and matrix metalloproteinase 2 (MMP2) genes were also assessed using real time RT-PCR. 17-β estradiol levels of mice sera were compared before and after transplantation.

RESULTS

The endometrial like glands and stromal cells were formed in the implanted subcutaneous tissue of both endometriosis models. The gland sections per cubic millimeter, the expression of OPN and MMP2 genes and the level of 17-β estradiol were higher in model B than model A (p=0.03).

CONCLUSION

Our observation demonstrated that endometrial mesenchymal stromal cells showed more efficiency to establish endometriosis model than human endometrial tissue fragments.

Platelets drive smooth muscle metaplasia and fibrogenesis in endometriosis through epithelial-mesenchymal transition and fibroblast-to-myofibroblast transdifferentiation

Smooth muscle metaplasia (SMM) and fibrotic tissues are frequently seen in endometriotic lesions, yet the mechanisms underlying their formation are poorly understood. In this study, we investigated the roles of activated platelets in driving epithelial-mesenchymal transition (EMT) and fibroblast-to-myofibroblast transdifferentiation (FMT) in endometriosis. Through in vitro experimentations, we found that activated platelets, through the release of TGF-β1 and the induction of TGF-β/Smad signaling pathway, promoted EMT and FMT in endometriosis, resulting in increased cell contractility, collagen production, and ultimately to fibrosis. TGF-β blockade reversed these processes. Prolonged exposure of endometriotic stromal cells to activated platelets induced increased expression of α-SMA as well as markers of differentiated smooth muscle cells. Consequently, endometriotic lesions and their microenvironment contain all the necessary molecular machinery to promote SMM and fibrogenesis. Our results suggest that endometriotic lesions are wounds that undergo repeated injury and healing, highlighting the importance of platelets in the development of endometriosis.

Blood biomarkers for the non-invasive diagnosis of endometriosis

BACKGROUND

About 10% of reproductive-aged women suffer from endometriosis, a costly chronic disease causing pelvic pain and subfertility. Laparoscopy is the gold standard diagnostic test for endometriosis, but is expensive and carries surgical risks. Currently, there are no non-invasive or minimally invasive tests available in clinical practice to accurately diagnose endometriosis. Although other reviews have assessed the ability of blood tests to diagnose endometriosis, this is the first review to use Cochrane methods, providing an update on the rapidly expanding literature in this field.

OBJECTIVES

To evaluate blood biomarkers as replacement tests for diagnostic surgery and as triage tests to inform decisions on surgery for endometriosis. Specific objectives include:1. To provide summary estimates of the diagnostic accuracy of blood biomarkers for the diagnosis of peritoneal, ovarian and deep infiltrating pelvic endometriosis, compared to surgical diagnosis as a reference standard.2. To assess the diagnostic utility of biomarkers that could differentiate ovarian endometrioma from other ovarian masses.

SEARCH METHODS

We did not restrict the searches to particular study designs, language or publication dates. We searched CENTRAL to July 2015, MEDLINE and EMBASE to May 2015, as well as these databases to 20 April 2015: CINAHL, PsycINFO, Web of Science, LILACS, OAIster, TRIP, ClinicalTrials.gov, DARE and PubMed.

SELECTION CRITERIA

We considered published, peer-reviewed, randomised controlled or cross-sectional studies of any size, including prospectively collected samples from any population of reproductive-aged women suspected of having one or more of the following target conditions: ovarian, peritoneal or deep infiltrating endometriosis (DIE). We included studies comparing the diagnostic test accuracy of one or more blood biomarkers with the findings of surgical visualisation of endometriotic lesions.

DATA COLLECTION AND ANALYSIS

Two authors independently collected and performed a quality assessment of data from each study. For each diagnostic test, we classified the data as positive or negative for the surgical detection of endometriosis, and we calculated sensitivity and specificity estimates. We used the bivariate model to obtain pooled estimates of sensitivity and specificity whenever sufficient datasets were available. The predetermined criteria for a clinically useful blood test to replace diagnostic surgery were a sensitivity of 0.94 and a specificity of 0.79 to detect endometriosis. We set the criteria for triage tests at a sensitivity of ≥ 0.95 and a specificity of ≥ 0.50, which 'rules out' the diagnosis with high accuracy if there is a negative test result (SnOUT test), or a sensitivity of ≥ 0.50 and a specificity of ≥ 0.95, which 'rules in' the diagnosis with high accuracy if there is a positive result (SpIN test).

MAIN RESULTS

We included 141 studies that involved 15,141 participants and evaluated 122 blood biomarkers. All the studies were of poor methodological quality. Studies evaluated the blood biomarkers either in a specific phase of the menstrual cycle or irrespective of the cycle phase, and they tested for them in serum, plasma or whole blood. Included women were a selected population with a high frequency of endometriosis (10% to 85%), in which surgery was indicated for endometriosis, infertility work-up or ovarian mass. Seventy studies evaluated the diagnostic performance of 47 blood biomarkers for endometriosis (44 single-marker tests and 30 combined tests of two to six blood biomarkers). These were angiogenesis/growth factors, apoptosis markers, cell adhesion molecules, high-throughput markers, hormonal markers, immune system/inflammatory markers, oxidative stress markers, microRNAs, tumour markers and other proteins. Most of these biomarkers were assessed in small individual studies, often using different cut-off thresholds, and we could only perform meta-analyses on the data sets for anti-endometrial antibodies, interleukin-6 (IL-6), cancer antigen-19.9 (CA-19.9) and CA-125. Diagnostic estimates varied significantly between studies for each of these biomarkers, and CA-125 was the only marker with sufficient data to reliably assess sources of heterogeneity.The mean sensitivities and specificities of anti-endometrial antibodies (4 studies, 759 women) were 0.81 (95% confidence interval (CI) 0.76 to 0.87) and 0.75 (95% CI 0.46 to 1.00). For IL-6, with a cut-off value of > 1.90 to 2.00 pg/ml (3 studies, 309 women), sensitivity was 0.63 (95% CI 0.52 to 0.75) and specificity was 0.69 (95% CI 0.57 to 0.82). For CA-19.9, with a cut-off value of > 37.0 IU/ml (3 studies, 330 women), sensitivity was 0.36 (95% CI 0.26 to 0.45) and specificity was 0.87 (95% CI 0.75 to 0.99).Studies assessed CA-125 at different thresholds, demonstrating the following mean sensitivities and specificities: for cut-off > 10.0 to 14.7 U/ml: 0.70 (95% CI 0.63 to 0.77) and 0.64 (95% CI 0.47 to 0.82); for cut-off > 16.0 to 17.6 U/ml: 0.56 (95% CI 0.24, 0.88) and 0.91 (95% CI 0.75, 1.00); for cut-off > 20.0 U/ml: 0.67 (95% CI 0.50 to 0.85) and 0.69 (95% CI 0.58 to 0.80); for cut-off > 25.0 to 26.0 U/ml: 0.73 (95% CI 0.67 to 0.79) and 0.70 (95% CI 0.63 to 0.77); for cut-off > 30.0 to 33.0 U/ml: 0.62 (95% CI 0.45 to 0.79) and 0.76 (95% CI 0.53 to 1.00); and for cut-off > 35.0 to 36.0 U/ml: 0.40 (95% CI 0.32 to 0.49) and 0.91 (95% CI 0.88 to 0.94).We could not statistically evaluate other biomarkers meaningfully, including biomarkers that were assessed for their ability to differentiate endometrioma from other benign ovarian cysts.Eighty-two studies evaluated 97 biomarkers that did not differentiate women with endometriosis from disease-free controls. Of these, 22 biomarkers demonstrated conflicting results, with some studies showing differential expression and others no evidence of a difference between the endometriosis and control groups.

AUTHORS' CONCLUSIONS

Of the biomarkers that were subjected to meta-analysis, none consistently met the criteria for a replacement or triage diagnostic test. A subset of blood biomarkers could prove useful either for detecting pelvic endometriosis or for differentiating ovarian endometrioma from other benign ovarian masses, but there was insufficient evidence to draw meaningful conclusions. Overall, none of the biomarkers displayed enough accuracy to be used clinically outside a research setting. We also identified blood biomarkers that demonstrated no diagnostic value in endometriosis and recommend focusing research resources on evaluating other more clinically useful biomarkers.

Endometrial biomarkers for the non-invasive diagnosis of endometriosis

BACKGROUND

About 10% of reproductive-aged women suffer from endometriosis, which is a costly, chronic disease that causes pelvic pain and subfertility. Laparoscopy is the gold standard diagnostic test for endometriosis, but it is expensive and carries surgical risks. Currently, there are no non-invasive tests available in clinical practice that accurately diagnose endometriosis. This is the first diagnostic test accuracy review of endometrial biomarkers for endometriosis that utilises Cochrane methodologies, providing an update on the rapidly expanding literature in this field.

OBJECTIVES

To determine the diagnostic accuracy of the endometrial biomarkers for pelvic endometriosis, using a surgical diagnosis as the reference standard. We evaluated the tests as replacement tests for diagnostic surgery and as triage tests to inform decisions to undertake surgery for endometriosis.

SEARCH METHODS

We did not restrict the searches to particular study designs, language or publication dates. To identify trials, we searched the following databases: CENTRAL (2015, July), MEDLINE (inception to May 2015), EMBASE (inception to May 2015), CINAHL (inception to April 2015), PsycINFO (inception to April 2015), Web of Science (inception to April 2015), LILACS (inception to April 2015), OAIster (inception to April 2015), TRIP (inception to April 2015) and ClinicalTrials.gov (inception to April 2015). We searched DARE and PubMed databases up to April 2015 to identify reviews and guidelines as sources of references to potentially relevant studies. We also performed searches for papers recently published and not yet indexed in the major databases. The search strategies incorporated words in the title, abstract, text words across the record and the medical subject headings (MeSH).

SELECTION CRITERIA

We considered published peer-reviewed, randomised controlled or cross-sectional studies of any size that included prospectively collected samples from any population of reproductive-aged women suspected of having one or more of the following target conditions: ovarian, peritoneal or deep infiltrating endometriosis (DIE).

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data from each study and performed a quality assessment. For each endometrial diagnostic test, we classified the data as positive or negative for the surgical detection of endometriosis and calculated the estimates of sensitivity and specificity. We considered two or more tests evaluated in the same cohort as separate data sets. We used the bivariate model to obtain pooled estimates of sensitivity and specificity whenever sufficient data were available. The predetermined criteria for a clinically useful test to replace diagnostic surgery was one with a sensitivity of 94% and a specificity of 79%. The criteria for triage tests were set at sensitivity at or above 95% and specificity at or above 50%, which in case of negative results rules out the diagnosis (SnOUT test) or sensitivity at or above 50% with specificity at or above 95%, which in case of positive result rules in the diagnosis (SpIN test).

MAIN RESULTS

We included 54 studies involving 2729 participants, most of which were of poor methodological quality. The studies evaluated endometrial biomarkers either in specific phases of the menstrual cycle or outside of it, and the studies tested the biomarkers either in menstrual fluid, in whole endometrial tissue or in separate endometrial components. Twenty-seven studies evaluated the diagnostic performance of 22 endometrial biomarkers for endometriosis. These were angiogenesis and growth factors (PROK-1), cell-adhesion molecules (integrins α3β1, α4β1, β1 and α6), DNA-repair molecules (hTERT), endometrial and mitochondrial proteome, hormonal markers (CYP19, 17βHSD2, ER-α, ER-β), inflammatory markers (IL-1R2), myogenic markers (caldesmon, CALD-1), neural markers (PGP 9.5, VIP, CGRP, SP, NPY, NF) and tumour markers (CA-125). Most of these biomarkers were assessed in single studies, whilst only data for PGP 9.5 and CYP19 were available for meta-analysis. These two biomarkers demonstrated significant diversity for the diagnostic estimates between the studies; however, the data were too limited to reliably determine the sources of heterogeneity. The mean sensitivities and specificities of PGP 9.5 (7 studies, 361 women) were 0.96 (95% confidence interval (CI) 0.91 to 1.00) and 0.86 (95% CI 0.70 to 1.00), after excluding one outlier study, and for CYP19 (8 studies, 444 women), they were were 0.77 (95% CI 0.70 to 0.85) and 0.74 (95% CI 0.65 to 84), respectively. We could not statistically evaluate other biomarkers in a meaningful way. An additional 31 studies evaluated 77 biomarkers that showed no evidence of differences in expression levels between the groups of women with and without endometriosis.

AUTHORS' CONCLUSIONS

We could not statistically evaluate most of the biomarkers assessed in this review in a meaningful way. In view of the low quality of most of the included studies, the findings of this review should be interpreted with caution. Although PGP 9.5 met the criteria for a replacement test, it demonstrated considerable inter study heterogeneity in diagnostic estimates, the source of which could not be determined. Several endometrial biomarkers, such as endometrial proteome, 17βHSD2, IL-1R2, caldesmon and other neural markers (VIP, CGRP, SP, NPY and combination of VIP, PGP 9.5 and SP) showed promising evidence of diagnostic accuracy, but there was insufficient or poor quality evidence for any clinical recommendations. Laparoscopy remains the gold standard for the diagnosis of endometriosis, and using any non-invasive tests should only be undertaken in a research setting. We have also identified a number of biomarkers that demonstrated no diagnostic value for endometriosis. We recommend that researchers direct future studies towards biomarkers with high diagnostic potential in good quality diagnostic studies.

Update on Biomarkers for the Detection of Endometriosis

Endometriosis is histologically characterized by the displacement of endometrial tissue to extrauterine locations including the pelvic peritoneum, ovaries, and bowel. An important cause of infertility and pelvic pain, the individual and global socioeconomic burden of endometriosis is significant. Laparoscopy remains the gold standard for the diagnosis of the condition. However, the invasive nature of surgery, coupled with the lack of a laboratory biomarker for the disease, results in a mean latency of 7–11 years from onset of symptoms to definitive diagnosis. Unfortunately, the delay in diagnosis may have significant consequences in terms of disease progression. The discovery of a sufficiently sensitive and specific biomarker for the nonsurgical detection of endometriosis promises earlier diagnosis and prevention of deleterious sequelae and represents a clear research priority. In this review, we describe and discuss the current status of biomarkers of endometriosis in plasma, urine, and endometrium.

Molecular aspects of development and regulation of endometriosis

Endometriosis is a common and painful condition affecting women of reproductive age. While the underlying pathophysiology is still largely unknown, much advancement has been made in understanding the progression of the disease. In recent years, a great deal of research has focused on non-invasive diagnostic tools, such as biomarkers, as well as identification of potential therapeutic targets. In this article, we will review the etiology and cellular mechanisms associated with endometriosis as well as the current diagnostic tools and therapies. We will then discuss the more recent genomic and proteomic studies and how these data may guide development of novel diagnostics and therapeutics. The current diagnostic tools are invasive and current therapies primarily treat the symptoms of endometriosis. Optimally, the advancement of "-omic" data will facilitate the development of non-invasive diagnostic biomarkers as well as therapeutics that target the pathophysiology of the disease and halt, or even reverse, progression. However, the amount of data generated by these types of studies is vast and bioinformatics analysis, such as we present here, will be critical to identification of appropriate targets for further study.