An investigation of the effects of endometriosis on the proteome of human eutopic endometrium: A heterogeneous tissue with a complex disease

Chronic Pelvic Pain, Vulvar Pain Disorders, and Proteomics Profiles: New Discoveries, New Hopes

Chronic pelvic pain (CPP) is generally defined as non-cyclic pain perceived in the pelvic area that has persisted from three to six months or longer and is unrelated to pregnancy. The etiology of CPP is complex, multifactorial, with heterogeneous presentation, and includes several diseases such as endometriosis, adenomyosis, and interstitial cystitis/bladder pain syndrome. It may also be associated with sexual dysfunction, musculoskeletal disorders, and comorbid psychiatric symptoms. Vulvar pain disorders (VPDs) are typically categorized separately from chronic pelvic pain; among all VPDs, vulvodynia is a chronic vulvar pain of unknown etiology, lasting at least 3 months and that might be associated with other potentially linked factors. Proteomics represents a useful approach to study the proteome profiles of clinical samples. In this review, we have considered a selection of articles that have analyzed the protein abundance and novel protein species from various biological samples, including eutopic/ectopic endometrium, urine, serum, follicular, peritoneal fluid, and cervical mucus, potentially involved in the pathogenesis and progression of CPP and VPDs. These findings could represent valuable targets for paving the way for the differential diagnosis and therapeutic management of CPP and VDPs, thereby optimizing both the prevention and treatment of these conditions.

Endometriosis and inflammatory immune responses: Indian experience

Endometriosis is a public health disorder affecting ∼ 247 million women globally and ∼ 42 million women in India. Women with endometriosis suffer from dysmenorrhea, chronic pelvic pain, dyspareunia, dyschezia, fatigue, depression, and infertility leading to significant socioeconomic impact and morbidity. The etiology of endometriosis is not understood well even after 100 years of research. Currently, there is no permanent cure for endometriosis. The inflammatory immune response is one of the important features of etiopathogenesis of endometriosis and therefore understanding the inflammatory immune response would lead to a better understanding of this enigmatic disorder and may also lead to biomarker discovery for diagnosis of endometriosis. We investigated the autoimmune etiology of endometriosis in the Indian population. Using the proteomics approach, anti-endometrial antibodies (AEAs) were detected in Indian women with endometriosis [anti-endometrial antibodies - tropomyosin 3 (TPM3), stomatin-like protein2 (SLP-2), and tropomodulin 3 (TMOD3)]. The studies on AEAs provided a better understanding of autoimmune mechanisms in endometriosis. All three subtypes of endometriosis; superficial peritoneal, ovarian endometrioma, and deep infiltrating endometriosis were reported in Indian women. In this review, we discuss our experiences of the inflammatory immune response, autoimmunity, comorbidities, and clinical phenotypes in women with endometriosis in India.

The Eutopic Endometrium Proteome in Endometriosis Reveals Candidate Markers and Molecular Mechanisms of Physiopathology

Endometriosis is a common chronic gynaecological disease causing various symptoms, such as infertility and chronic pain. The gold standard for its diagnosis is still laparoscopy and the biopsy of endometriotic lesions. Here, we aimed to compare the eutopic endometrium from women with or without endometriosis to identify proteins that may be considered as potential biomarker candidates. Eutopic endometrium was collected from patients with endometriosis (n = 4) and women without endometriosis (n = 5) during a laparoscopy surgery during the mid-secretory phase of their menstrual cycle. Total proteins from tissues were extracted and digested before LC-MS-MS analysis. Among the 5301 proteins identified, 543 were differentially expressed and enriched in two specific KEGG pathways: focal adhesion and PI3K/AKT signaling. Integration of our data with a large-scale proteomics dataset allowed us to highlight 11 proteins that share the same trend of dysregulation in eutopic endometrium, regardless of the phase of the menstrual cycle. Our results constitute the first step towards the identification of potential promising endometrial diagnostic biomarkers. They provide new insights into the mechanisms underlying endometriosis and its etiology. Our results await further confirmation on a larger sample cohort.

Differential expression of Lumican, Mimecan, Annexin A5 and Serotransferrin in ectopic and matched eutopic endometrium in ovarian endometriosis: a case-control study

AIM

Endometriosis is a debilitating disease marked by recurrent gynecological proliferations. The present study aimed at performing differential proteomic analysis of matched eutopic and ectopic endometrium from women with ovarian endometriosis.

MATERIALS AND METHODS

Proteomes were resolved using nano LC-MS and further identified and quantified using ProteinLynx Global SERVER (PLGS) software. Selected proteins were further chosen for validation by real time-polymerase chain reaction (RT-PCR).

RESULTS

The protein profiles uncovered several differentially expressed proteins in the diseased sample (ectopic endometrium) as compared to the reference sample (eutopic endometrium). The study involved an advanced proteomic approach, nano LC-MS, and validates for the first time the upregulation of Mimecan and Lumican proteins in endometriosis.

CONCLUSIONS

These proteins may hence prove as potentially useful tools in the search for diagnostic markers for early detection of the disease.

The endometrial proteomic profile around the time of embryo implantation†

Embryo implantation is an intricate process which requires competent embryo and receptive endometrium. The failure of endometrium to achieve receptivity is a recognized cause of infertility. However, due to multiplicity of events involved, the molecular mechanisms governing endometrial receptivity are still not fully understood. Traditional one-by-one approaches, including western blotting and histochemistry, are insufficient to examine the extensive changes of endometrial proteome. Although genomics and transcriptomics studies have identified several significant genes, the underlying mechanism remains to be uncovered owing to post-transcriptional and post-translational modifications. Proteomic technologies are high throughput in protein identification, and they are now intensively used to identify diagnostic and prognostic markers in the field of reproductive medicine. There is a series of studies analyzing endometrial proteomic profile, which has provided a mechanistic insight into implantation failure. These published studies mainly focused on the difference between pre-receptive and receptive stages of endometrium, as well as on the alternation of endometrial proteomics in women with reproductive failure. Here, we review recent data from proteomic analyses regarding endometrium around the time of embryo implantation and propose possible future research directions.

Molecular signature of eutopic endometrium in endometriosis based on the multi-omics integrative synthesis

PURPOSE

To synthesise data from genome-wide studies reporting molecular signature of eutopic endometrium through the phases of the menstrual cycle in endometriosis.

METHODS

Extraction of data from publications reporting genetic signatures characterising endometrium associated with endometriosis. The nomenclature of extracted differentially expressed transcripts and proteins was adopted according to the HUGO Gene Nomenclature Committee (HGNC). Loci were further sorted according to the different phases of the menstrual cycle, i.e. menstrual (M), proliferative (P), secretory (S), early-secretory (ES), mid-secretory (MS), late-secretory (LS), and not specified (N/S) if the endometrial dating was not available. Enrichment analysis was performed using the DAVID bioinformatics tool.

RESULTS

Altered molecular changes were reported by 21 studies, including 13 performed at the transcriptomic, 6 at proteomic, and 2 at epigenomic level. Extracted data resulted in a catalogue of total 670 genetic causes with available 591 official gene symbols, i.e. M = 3, P = 188, S = 81, ES = 82, MS = 173, LS = 36, and N/S = 28. Enriched pathways included oestrogen signalling pathway, extracellular matrix organization, and endothelial cell chemotaxis. Our study revealed that knowledge of endometrium biology in endometriosis is fragmented due to heterogeneity of published data. However, 15 genes reported as dysregulated by at least two studies within the same phase and 33 significantly enriched GO-BP terms/KEGG pathways associated with different phases of the menstrual cycle were identified.

CONCLUSIONS

A multi-omics insight into molecular patterns underlying endometriosis could contribute towards identification of endometrial pathological mechanisms that impact fertility capacities of women with endometriosis.

Characterization of exosomes in peritoneal fluid of endometriosis patients

OBJECTIVE

To demonstrate the feasibility of studying exosomes directly from peritoneal fluid, we isolated exosomes from endometriosis patient samples and from controls, and characterized their cargo.

DESIGN

Case-control experimental study.

SETTING

Academic clinical center.

PATIENT (S)

Women with and without endometriosis who underwent laparoscopic surgery (n = 28 in total).

INTERVENTION (S)

None.

MAIN OUTCOME MEASURE (S)

Concentration of exosomes within peritoneal fluid and protein content of the isolated exosomes.

RESULT (S)

Peritoneal fluid samples were pooled according to the cycle phase and disease stage to form six experimental groups, from which the exosomes were isolated. Exosomes were successfully isolated from peritoneal fluid in all the study groups. The concentration varied with cycle phase and disease stage. Proteomic analysis showed specific proteins in the exosomes derived from endometriosis patients that were absent in the controls. Five proteins were found exclusively in the endometriosis groups: PRDX1, H2A type 2-C, ANXA2, ITIH4, and the tubulin α-chain.

CONCLUSION (S)

Exosomes are present in peritoneal fluid. The characterization of endometriosis-specific exosomes opens up new avenues for the diagnosis and investigation of endometriosis.

Proteomics in the Diagnosis of Endometriosis: Opportunities and Challenges

The non-surgical diagnosis of endometriosis is still challenging for the clinician. Ultrasonography and magnetic resonance imaging can be used to diagnose ovarian endometriotic cysts and deep infiltrating endometriosis; but their performance is poor in the diagnosis of initial stages of endometriosis. CA-125 and other serum markers (such as CA 19-9, serum protein PP14, interleukins, and angiogenetic factors) have been measured in women with endometriosis but they are not reliable for the diagnosis of the disease. Although several studies used proteomics technologies to identify plasmatic markers of endometriosis, the non-invasive diagnosis of endometriosis is far from being achieved. In this issue, Manousopoulou et al. compare the integrated quantitative proteomic profile of eutopic endometrium and serum of women with endometriosis and controls. 1214 proteins are differentially expressed in the eutopic endometrium and 404 proteins in the serum of the two study groups. 21 proteins are aberrantly expressed in both eutopic endometrium and serum of women with endometriosis. More work is needed to assess if the differentially expressed proteins identified in this study can be used as clinical markers of endometriosis.

[Endometriosis and miscarriage: Systematic review]

OBJECTIVES

In spontaneous pregnancies, endometriosis appears to be a risk factor of miscarriage. The aim of this study is to evaluate the association between endometriosis and miscarriage in spontaneous pregnancy.

METHODS

We searched the Cochrane Library, Medline of eligible studies from inception to December 2016, without any restriction. We selected studies that compared endometriosis-affected pregnant women to disease-free pregnant women. To ensure the quality of the methodology, the PRISMA criteria have been met at all stages of the development of this meta-analysis. The primary adverse pregnancy outcomes studied was miscarriage. Three reviewers independently extracted the studies' characteristics and outcome data.

RESULTS

Of 225 identified abstracts, 4 primary studies met our inclusion criteria by comparing spontaneous pregnant patients with endometriosis to disease-free women. Miscarriage rate was higher in the endometriosis group (OR 1.77 [CI 95% 1.13-2.78]).

CONCLUSION

In spontaneous pregnancies, endometriosis appears to be a risk factor of miscarriages (almost 80% increased risk). Further prospective studies are needed to confirm these results in order to establish the exact impact of endometriosis on spontaneous pregnancy course.

Effect of interleukin-1β and lipoxin A4 in human endometriotic stromal cells: Proteomic analysis

AIM

Lipoxin A₄ (LXA₄ ) can function as an endogenous 'breaking signal' in inflammation and plays an important role in the progression of endometriosis. The proteome responses to interleukin-1β (IL-1β) or LXA₄ in human endometriotic stromal cells (ESC) are not well understood.

METHODS

In this study, primary ESC were cultured from ovarian endometriosis tissue. Three groups were established: the control group; the IL-1β stimulation group; and the IL-1β and LXA₄ incubation group. Proteins were assessed on 2-D polyacrylamide gel electrophoresis (2D-PAGE), and differentially expressed protein spots were further identified on matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MALDI-TOF-MS). Wound healing and transwell assays were performed to assess the migration and invasion of ESC after treatment.

RESULTS

In total, 40 differentially expressed protein spots were identified successfully on MALDI-TOF-MS. The proteins identified were related to cell structure, metabolism, signal transduction, protein synthesis and membrane structure, processes that may be involved in the development of endometriosis. Vinculin and IL-4 were further analyzed on western blot and quantitative real-time polymerase chain reaction. Moreover, LXA₄ could suppress the migration and invasion of ESC induced by IL-1β.

CONCLUSION

LXA₄ may inhibit the progression of endometriosis partly by lowering or raising the effect of IL-1β, mediated via some inflammation-related proteins (e.g. vinculin) and immune response-related protein (e.g. IL-4) in vitro.

Uterine flushing proteome of the tammar wallaby after reactivation from diapause

The marsupial tammar wallaby has the longest period of embryonic diapause of any mammal, up to 11 months, during which there is no cell division or blastocyst growth. Since the blastocyst in diapause is surrounded by acellular coats, the signals that maintain or terminate diapause involve factors that reside in uterine secretions. The nature of such factors remains to be resolved. In this study, uterine flushings (UFs) were used to assess changes in uterine secretions of tammars using liquid chromatography–mass spectrometry (LC–MS/MS) during diapause (day 0 and 3) and reactivation days (d) 4, 5, 6, 8, 9, 11 and 24 after removal of pouch young (RPY), which initiates embryonic development. This study supports earlier suggestions that the presence of specific factors stimulate reactivation, early embryonic growth and cell proliferation. A mitogen, hepatoma-derived growth factor and soluble epidermal growth factor receptors were observed from d3 until at least d11 RPY when these secreted proteins constituted 21% of the UF proteome. Binding of these factors to specific cellular receptors or growth factors may directly stimulate DNA synthesis and division in endometrial gland cells. Proteins involved in the p53/CDKN1A (p21) cell cycle inhibition pathway were also observed in the diapause samples. Progesterone and most of the oestrogen-regulated proteins were present in the UF after d3, which is concomitant with the start of blastocyst mitoses at d4. We propose that once the p21 inhibition of the cell cycle is lost, growth factors including HDGF and EGFR are responsible for reactivation of the diapausing blastocyst via the uterine secretions.

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.

A mass spectrometric insight into the origins of benign gynecological disorders

Applications of mass spectrometry (MS) are rapidly expanding and encompass molecular and cellular biology. MS aids in the analysis of in vivo global molecular alterations, identifying potential biomarkers which may improve diagnosis and treatment of various pathologies. MS has added new dimensionality to medical research. Pioneering gynecologists now study molecular mechanisms underlying female reproductive pathology with MS-based tools. Although benign gynecologic disorders including endometriosis, adenomyosis, leiomyoma, and polycystic ovarian syndrome (PCOS) carry low mortality rates, they cause significant physical, mental, and social detriments. Additionally, some benign disorders are unfortunately associated with malignancies. MS-based technology can detect malignant changes in formerly benign proteomes and metabolomes with distinct advantages of speed, sensitivity, and specificity. We present the use of MS in proteomics and metabolomics, and summarize the current understanding of the molecular pathways concerning female reproductive anatomy. Highlight discoveries of novel protein and metabolite biomarkers via MS-based technology, we underscore the clinical application of these techniques in the diagnosis and management of benign gynecological disorders. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:450-470, 2017.

Expression and clinical significance of annexin A2 and human epididymis protein 4 in endometrial carcinoma

Background

It is well-known that the treatment and monitoring methods are limited for advanced stage of endometrial carcinoma. Biological molecules with expression changes during tumor progression become potential therapeutic targets for advanced stage endometrial carcinoma. Annexin A2 (ANXA2) has been reported to be overexpressed in recurrent endometrial carcinoma, and the expression of human epididymis protein 4 (HE4) is upregulated in endometrial carcinoma. What’s more, ANXA2 and HE4 interacted in ovarian cancer and promoted the malignant biological behavior. We speculated that their interaction may exist in endometrial carcinoma as well. We evaluated the expression and the correlation relationship of ANXA2 and HE4 in endometrial carcinoma.

Methods

The expression of ANXA2 and HE4 protein in 84 endometrial carcinoma, 30 endometrial atypical hyperplasia, and 18 normal endometrial tissue samples were then measured using an immunohistochemical assay in paraffin embedded endometrial tissues. The structural relationship between ANXA2 and HE4 was explored by immunoprecipitation and double immunofluorescent staining.

Results

ANXA2 and HE4 co-localized in both endometrial tissues and endometrial carcinoma cells. ANXA2 and HE4 were expressed in 95.2 % and 85.7 % of the the endometrial carcinoma, respectively, which were significantly higher than normal endometrium (55.6 % and 16.7 %, both p < 0.05). The expression of ANXA2 and HE4 was significantly correlated with FIGO stage, degree of differentiation, myometrial invasion, and lymph node metastasis. ANXA2 was an independent risk factor for the prognosis of endometrial carcinoma (p < 0.05, hazard ratio [HR] = 8.004). The expression of ANXA2 and HE4 was positively correlated (Spearman correlation coefficient = 0.228, p < 0.05). HE4 was an independent factor for ANXA2 in multivariate linear regression model (p < 0.05).

Conclusion

We revealed the co-localization of ANXA2 and HE4 in endometrial carcinoma. Expression levels of ANXA2 and HE4 were closely related to the malignant biological behavior of endometrial carcinoma, and ANXA2 was an independent risk factor for poor prognosis. The expression of ANXA2 and HE4 can affect each other.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0208-8) contains supplementary material, which is available to authorized users.

Follicular fluid alterations in endometriosis: label-free proteomics by MS(E) as a functional tool for endometriosis

Endometriosis is a chronic gynecological condition that affects 10-32% of women of reproductive age and may lead to infertility. The study of protein profiles in follicular fluid may assist in elucidating possible biomarkers related to this disease. For this, follicular fluid samples were obtained from women with tubal factor or minimal male factor infertility who had pregnancy outcomes after in vitro fertilization (IVF) treatment (control group, n = 10), women with endometriosis (endometriosis group, n = 10), along with the endometrioma from these same patients were included (endometrioma group, n = 10). For proteomic analysis, samples were pooled according to their respective groups and normalized to protein content. Proteins were analyzed by in tandem mass spectrometry (MS(E)) Spectra processing and the ProteinLynx Global Server v.2.5. was used for database searching. Data was submitted to the biological network analysis using Cytoscape 2.8.2 with ClueGO plugin. As a result, 535 proteins were identified among all groups. The control group differentially or uniquely expressed 33 (6%) proteins and equal expression of 98 (18%) proteins was observed in the control and endometriosis groups of which 41 (7%) proteins were further identified and/or quantified. Six (1%) proteins were observed in both the endometriosis and endometrioma groups, but 212 (39%) proteins were exclusively identified and/or quantified in the endometrioma group. There were 9 (1%) proteins observed in both the control and endometrioma groups and there were 139 (25%) proteins common among all three groups. Distinct differences among the protein profiles in the follicular fluid of patients included in this study were found, identifying proteins related to the disease progression and IVF success. Thus, some pathways related to endometriosis are associated with the presence of specific proteins, as well as the absence of others. This study provides a first step to the development of more sensitive diagnostic tests and treatment.

Application of gel-based proteomic technique in female reproductive investigations

Recently, gel-based proteomics has been increasingly applied to investigate proteins involved in female reproductive tract in healthy and disease states. Gel-based proteomics coupled by mass spectrometry (MS) facilitate the identification of new proteins playing roles in cellular and molecular interactions underlying female reproductive biology and it is a useful method to identify novel biomarkers of diseases by studying thousands of proteins simultaneously involved in female reproductive tract in healthy state compared to disease state. This review will discuss the best studies areas contributed to female reproductive biology in which gel-based proteomics coupled by MS has been applied to generate proteome of female reproductive tract in a healthy state.

Investigation of serum proteome alterations in human endometriosis

Endometriosis is a common benign gynecological disease, characterized by proliferation of functional endometrial glands and stroma outside the uterine cavity. The present study involves investigation of alterations in the serum proteome of endometriosis patients compared to healthy controls using 2DE and 2D-DIGE combined with MALDI TOF/TOF-MS. Comparison of serum proteome of endometriosis patients and healthy subjects revealed 25 significant differentially expressed proteins. Gene ontology and network analysis, performed using PANTHER, DAVID, WebGestalt and STRING, revealed that the differentially expressed proteins are majorly involved in response to stimulus, immune system, metabolic, localization and cellular processes. For serum diagnostic marker identification, several robust statistical screening procedures were applied to identify the set of the most significant proteins responsible for successful diagnosis of different endometriosis stages. Partial least squares (PLS) based marker selection tool and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to identify the most significant proteins for disease prediction. Western blotting validation in a separate cohort of patients revealed that haptoglobin (HP), Ig kappa chain C region (IGKC), alpha-1B-glycoprotein (A1BG) can be considered effective serum protein markers for the diagnosis of Stage II, III and IV endometriosis. For diagnosis of Stage I, only IGKC and HP seemed promising.

BIOLOGICAL SIGNIFICANCE

Globally, about 12 in 100 women of reproductive age are diagnosed with endometriosis. The pathogenesis of the disease still remains unclear, leading to non-specific therapeutic approaches for disease management. Moreover, there is a delay of 8-12years in correct diagnosis after the initial onset of symptoms leading to a considerable impact on the woman's lifestyle. Also, the gold standard for diagnosis of endometriosis, laparoscopy, is an invasive procedure. The value of a noninvasive or semi-invasive diagnostic test for endometriosis with easily accessible fluids such as plasma, serum, urine, and saliva is, therefore, rightfully recognized. The present study is expected to considerably improve the understanding of the disease pathogenesis along with improved diagnostics and therapeutic approaches leading to better management of the disease.

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.

Knockdown of prohibitin expression promotes glucose metabolism in eutopic endometrial stromal cells from women with endometriosis

In this in-vitro study, the effect of prohibitin (PHB) on glucose metabolism in eutopic endometrial stromal cells from women with endometriosis was investigated. Endometrial stromal cells were isolated from endometrium in women with endometriosis, in women without endometriosis, or from endometrioma tissues. Glucose metabolic phenotype of stromal cells were examined in vitro. Quantitative polymerase chain reaction was used to measure the mRNA expression of glycolysis-related genes. Glucose consumption and lactate production were examined after knockdown of PHB expression in women with endometriosis with siRNA. In endometrioma tissue, significantly increased glucose consumption, lactate production and aberrant expression of glycolysis-related enzymes were found in women with endometriosis compared with women who do not have endometriosis (P < 0.05 versus P < 0.001). In women with endometriosis, PHB mRNA and protein were under-expressed in endometrioma tissue; in women without endometriosis, PHB mRNA and protein were over-expressed. Knockdown of PHB expression in women with endometriosis increased glucose consumption, although it had no effect on lactate production. This study suggests that aberrant expression of glycolysis-related enzymes in endometrioma tissue is associated with enhanced glycolytic metabolism. The malignant-like feature may be partially caused by low-expression of PHB gene in endometriotic stromal cells.

OMICS: Current and future perspectives in reproductive medicine and technology

Many couples present fertility problems at their reproductive age, and although in the last years, the efficiency of assisted reproduction techniques has increased, these are still far from being 100% effective. A key issue in this field is the proper assessment of germ cells, embryos and endometrium quality, in order to determine the actual likelihood to succeed. Currently available analysis is mainly based on morphological features of oocytes, sperm and embryos and although these strategies have improved the results, there is an urgent need of new diagnostic and therapeutic tools. The emergence of the - OMICS technologies (epigenomics, genomics, transcriptomics, proteomics and metabolomics) permitted the improvement on the knowledge in this field, by providing with a huge amount of information regarding the biological processes involved in reproductive success, thereby getting a broader view of complex biological systems with a relatively low cost and effort.

Identification of biomarkers for endometriosis in plasma from patients with endometriosis using a proteomics approach

The present study aimed to examine potential biomarkers for the diagnosis of endometriosis. A plasma-based proteomic approach, including 2-dimentional electrophoresis and mass spectrometry, was used. Samples were obtained from patients with (n=15) and without (n=15) endometriosis, or from mice with surgically induced endometriosis. Seven spots corresponding to six differentially expressed proteins were identified in the human plasma samples. However, only haptoglobin (Hp) was identified to be significantly decreased in the plasma levels of patients with endometriosis (P<0.05) and in mice with surgically induced endometriosis (P<0.05). The results demonstrated that Hp was downregulated in females with endometriosis, and it therefore, may be a useful diagnostic tool as a biomarker of endometriosis.

Power of proteomics in linking oxidative stress and female infertility

Endometriosis, PCOS, and unexplained infertility are currently the most common diseases rendering large numbers of women infertile worldwide. Oxidative stress, due to its deleterious effects on proteins and nucleic acids, is postulated to be the one of the important mechanistic pathways in differential expression of proteins and in these diseases. The emerging field of proteomics has allowed identification of proteins involved in cell cycle, as antioxidants, extracellular matrix (ECM), cytoskeleton, and their linkage to oxidative stress in female infertility related diseases. The aim of this paper is to assess the association of oxidative stress and protein expression in the reproductive microenvironments such as endometrial fluid, peritoneal fluid, and follicular fluid, as well as reproductive tissues and serum. The review also highlights the literature that proposes the use of the fertility related proteins as potential biomarkers for noninvasive and early diagnosis of the aforementioned diseases rather than utilizing the more invasive methods used currently. The review will highlight the power of proteomic profiles identified in infertility related disease conditions and their linkage with underlying oxidative stress. The power of proteomics will be reviewed with regard to eliciting molecular mechanisms for early detection and management of these infertility related conditions.

Proteomic analysis of the sheep caruncular and intercaruncular endometrium reveals changes in functional proteins crucial for the establishment of pregnancy

The expression and regulation of endometrial proteins are crucial for conceptus implantation and development. However, little is known about site-specific proteome profiles of the mammalian endometrium during the peri-implantation period. We utilised a two-dimensional gel electrophoresis/mass spectrometry-based proteomics approach to compare and identify differentially expressed proteins in sheep endometrium. Caruncular and intercaruncular endometrium were collected on days 12 (C12) and 16 (C16) of the oestrous cycle and at three stages of pregnancy corresponding to conceptus pre-attachment (P12), implantation (P16) and post-implantation (P20). Abundance and localisation changes in differentially expressed proteins were determined by western blot and immunohistochemistry. In caruncular endometrium, 45 protein spots (5% of total spots) altered between day 12 of pregnancy (P12) and P16 while 85 protein spots (10% of total spots) were differentially expressed between P16 and C16. In intercaruncular endometrium, 31 protein spots (2% of total spots) were different between P12 and P16 while 44 protein spots (4% of total spots) showed differential expression between C12 and C16. The pattern of protein changes between caruncle and intercaruncle sites was markedly different. Among the protein spots with implantation-related changes in volume, 11 proteins in the caruncular endometrium and six proteins in the intercaruncular endometrium, with different functions such as protein synthesis and degradation, antioxidant defence, cell structural integrity, adhesion and signal transduction, were identified. Our findings highlight the different but important roles of the caruncular and intercaruncular proteins during early pregnancy.

In utero exposure to environmentally relevant concentrations of PCB 153 and PCB 118 disrupts fetal testis development in sheep

Polychlorinated biphenyls (PCB) are environmental pollutants linked to adverse health effects including endocrine disruption and disturbance of reproductive development. This study aimed to determine whether exposure of pregnant sheep to three different mixtures of PCB 153 and PCB 118 affected fetal testis development. Ewes were treated by oral gavage from mating until euthanasia (d 134), producing three groups of fetuses with distinct adipose tissue PCB levels: high PCB 153/low PCB 118 (n = 13), high PCB 118/low PCB 153 (n = 14), and low PCB 153/low PCB 118 (n = 14). Fetal testes and blood samples were collected for investigation of testosterone, testis morphology, and testis proteome. The body weight of the offspring was lower in the high PCB compared to the low PCB group, but there were no significant differences in testis weight between groups when corrected for body weight. PCB exposure did not markedly affect circulating testosterone. There were no significant differences between groups in number of seminiferous tubules, Sertoli cell only tubules, and ratio between relative areas of seminiferous tubules and interstitium. Two-dimensional (2D) gel-based proteomics was used to screen for proteomic alterations in the high exposed groups relative to low PCB 153/low PCB 118 group. Twenty-six significantly altered spots were identified by liquid chromatography (LC)-mass spectroscopy (MS)/MS. Changes in protein regulation affected cellular processes as stress response, protein synthesis, and cytoskeleton regulation. The study demonstrates that in utero exposure to different environmental relevant PCB mixtures exerted subtle effects on developing fetal testis proteome but did not significantly disturb testis morphology and testosterone production.

Vitamin D binding protein plays an important role in the progression of endometriosis

Endometriosis, characterized by the growth of the endometrial gland and stroma outside the uterine cavity, is a gynecological disorder affecting 6‑10% of women of reproductive age. However, the pathogenesis of endometriosis and the molecular mechanisms involved in the progression of this disease remain to be clarified. Therefore, in this study two-dimensional gel electrophoresis (2‑DE) combined with mass spectrometry (MS) were applied to explore endometrial proteins with a role in the progression of endometriosis. Expression of global proteins in ectopic endometrial tissue (n=13; endometriosis group) was compared with that of the normal endometrial tissue (n=6; control group). Sixteen differently expressed proteins, including Vitamin D binding protein (DBP), with various functions were primarily identified in the ectopic endometrial tissue. DBP was confirmed to be significantly increased in the ectopic endometrial tissue compared with that in the normal endometrial tissue (P<0.05). Results of the present study therefore showed that DBP may play an important role in the progression of endometriosis.

Biomarkers of endometriosis

BACKGROUND

Diagnosis of endometriosis is surgical through laparoscopy, which is invasive, costly and associated with potential complications.

OBJECTIVES

A non-invasive test for diagnosis of endometriosis will focus the use of laparoscopy on women who are highly suspected of having endometriosis. This review includes studies about different biomarkers for endometriosis and their potential for the non-surgical diagnosis of this disease.

METHODS

This review covers studies that investigated different biomarkers in blood or endometrium. Studies that identified definite cutoff points and evaluated the diagnostic performance of the biomarker as a blood test for endometriosis are focused on.

RESULTS/CONCLUSIONS

Some of the markers investigated showed a good specificity, none of them showed a high sensitivity. More multi-center studies involving larger numbers of patients are required to identify the most useful biomarker.

Caldesmon: new insights for diagnosing endometriosis

Considerable effort has been invested in searching for less invasive methods of diagnosing endometriosis. Previous studies have indicated altered levels of the CALD1 gene (encoding the protein caldesmon) in endometriosis. The aims of our study were to investigate whether average CALD1 expression and caldesmon protein levels are differentially altered in the endometrium and endometriotic lesions and to evaluate the performance of the CALD1 gene and caldesmon protein as potential biomarkers for endometriosis. Paired biopsies of endometrial tissue (eutopic endometrium) and endometriotic lesions (ectopic endometrium) were obtained from patients with endometriosis to evaluate CALD1 gene expression and caldesmon protein levels by real-time PCR and Western blot analysis, respectively. In addition, immunostaining for caldesmon to determine cellular localization was also performed. Endometrium from women without endometriosis was used as a control. Increased CALD1 expression and caldesmon levels were detected in the endometriotic lesions. The electrophoretic profile of caldesmon by Western blot analysis was clearly different between the control group (endometrium of women without endometriosis) and the group of women with endometriosis (eutopic endometrium and endometriotic lesions). Caldesmon expression as determined by immunostaining showed no variation among the cell types in endometriotic lesions and eutopic endometrium. Stromal cells marked positively in eutopic endometrium from control patients and in the endometriotic lesions. The presence of caldesmon in the endometrium of patients with and without endometriosis permitted diagnoses with 95% sensitivity (specificity 100%) and 100% sensitivity (specificity 100%) for the disease and for minimal to mild endometriosis in the proliferative phase of the menstrual cycle, respectively. In the secretory phase, minimal to mild endometriosis was detected with 90% sensitivity and 93.3% specificity. Caldesmon is a possible predictor of endometrial dysregulation in patients with endometriosis. A potential limitation of our study is the fact that other endometrial diseases were not excluded, and therefore prospective studies are needed to confirm the potential of caldesmon as a biomarker exclusively for endometriosis.

Cellular and molecular basis for endometriosis-associated infertility

Endometriosis is a gynecological disease characterized by the presence of endometrial glandular epithelial and stromal cells growing in the extra-uterine environment. The disease afflicts 10%–15% of menstruating women causing debilitating pain and infertility. Endometriosis appears to affect every part of a woman’s reproductive system including ovarian function, oocyte quality, embryo development and implantation, uterine function and the endocrine system choreographing the reproductive process and results in infertility or spontaneous pregnancy loss. Current treatments are laden with menopausal-like side effects and many cause cessation or chemical alteration of the reproductive cycle, neither of which is conducive to achieving a pregnancy. However, despite the prevalence, physical and psychological tolls and health care costs, a cure for endometriosis has not yet been found. We hypothesize that endometriosis causes infertility via multifaceted mechanisms that are intricately interwoven thereby contributing to our lack of understanding of this disease process. Identifying and understanding the cellular and molecular mechanisms responsible for endometriosis-associated infertility might help unravel the confounding multiplicities of infertility and provide insights into novel therapeutic approaches and potentially curative treatments for endometriosis.

Proteomics in reproductive biology: beacon for unraveling the molecular complexities

Proteomics, an interface of rapidly evolving advances in physics and biology, is rapidly developing and expanding its potential applications to molecular and cellular biology. Application of proteomics tools has contributed towards identification of relevant protein biomarkers that can potentially change the strategies for early diagnosis and treatment of several diseases. The emergence of powerful mass spectrometry-based proteomics technique has added a new dimension to the field of medical research in liver, heart diseases and certain forms of cancer. Most proteomics tools are also being used to study physiological and pathological events related to reproductive biology. There have been attempts to generate the proteomes of testes, sperm, seminal fluid, epididymis, oocyte, and endometrium from reproductive disease patients. Here, we have reviewed proteomics based investigations in humans over the last decade, which focus on delineating the mechanism underlying various reproductive events such as spermatogenesis, oogenesis, endometriosis, polycystic ovary syndrome, embryo development. The challenge is to harness new technologies like 2-DE, DIGE, MALDI-MS, SELDI-MS, MUDPIT, LC-MS etc., to a greater extent to develop widely applicable clinical tools in understanding molecular aspects of reproduction both in health and disease.

Annexin A2 is critical for embryo adhesiveness to the human endometrium by RhoA activation through F-actin regulation

Annexin A2 (ANXA2) is present in vivo in the mid- and late-secretory endometria and is mainly localized in the luminal epithelium. Our aim was to evaluate its function in regulating the human implantation process. With an in vitro adhesion model, constructed to evaluate how the mouse embryo and JEG-3 spheroids attach to human endometrial epithelial cells, we demonstrated that ANXA2 inhibition significantly diminishes embryo adhesiveness. ANXA2 is also implicated in endometrial epithelial cell migration and trophoblast outgrowth. ANXA2 was seen to be linked to the RhoA/ROCK pathway and to regulate cell adhesion. We noted that ANXA2 inhibition significantly reduces active RhoA, although RhoA inactivation does not alter the ANXA2 levels. RhoA inactivation and ROCK inhibition also moderate embryo adhesiveness to endometrial epithelial cells. We corroborated that the induction of constitutively active RhoA partially reverses the effects of ANXA2 inhibition on endometrial adhesiveness. These molecules colocalize on the plasma membrane of endometrial epithelial cells, and a large proportion of ANXA2 and RhoA are colocalized in the F-actin networks. The functional effects of ANXA2 inhibition and RhoA/ROCK inactivation are associated with significant alterations in F-actin organization and its depolymerization. ANXA2 may act upstream of the RhoA/ROCK pathway by regulating F-actin remodeling and is a key factor in human endometrial adhesiveness.

Assessment of endometrial receptivity

OBJECTIVE

To provide a focused review of the scientific literature pertaining to endometrial receptivity.

DESIGN

Review of the literature and appraisal of relevant articles.

SETTING

Academic teaching hospital.

PATIENT(S)

Women with infertility.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Critical review of the literature.

RESULT(S)

Although a consensus has been achieved regarding the existence of a temporally defined period during which embryo attachment and invasion can occur (called the "window of implantation"), reliable methods to assess "receptivity" have not been established or adequately validated. In women with certain gynecologic disorders, including endometriosis, tubal disease, and polycystic ovary syndrome, endometrial receptivity seems to be compromised, leading to infertility and pregnancy loss. The establishment of reliable biomarkers for the detection of defects in endometrial receptivity has been a long-sought goal that remains an elusive target. The validation of endometrial biomarkers will require properly designed and implemented studies based on the recognition that endometrial receptivity defects are not equally distributed in women with endometriosis or these other conditions.

CONCLUSION(S)

Rapidly advancing technologies are bringing new biomarkers to the clinical arena that promise to further reveal the complexities of the implantation process.

The role of DJ-1 in the pathogenesis of endometriosis

BACKGROUND

Endometriosis is an estrogen-dependent disease causing pelvic pain and infertility in 10% of reproductive-aged women. Despite a long history of the disease the pathogenesis of endometriosis is poorly understood. It is known that the expression of several proteins is either up or down regulated during endometriosis, but their precise role remains to be determined. DJ-1 is one such protein that is upregulated in eutopic endometrium of women having endometriosis suggesting that DJ-1 may be involved in the pathogenesis of endometriosis.

METHODOLOGY AND PRINCIPAL FINDINGS

The role of DJ-1 in the pathogenesis of endometriosis was investigated. For this purpose the influence of DJ-1 on endometrial cell survival, attachment, proliferation, migration, and invasion either by overexpressing DJ-1 in normal endometrial cells or by knocking down DJ-1 expression in endometriotic cells using siRNA was investigated. The results indicated that DJ-1 protects endometrial cells from oxidative stress mediated apoptosis. Overexpression of DJ-1 in normal endometrial epithelial cells increases the adhesion on collagen type IV. However, no significant difference was observed incase of stromal cells. It was further demonstrated that DJ-1 regulates cell proliferation, migration, and invasion in normal endometrial and endometriotic epithelial cells whereas in the case of normal endometrial and endometriotic stromal cells, it regulates cell proliferation and invasion but not migration. Furthermore, the present study also indicated that DJ-1 regulates these cellular processes by modulating PI3K/Akt pathway by interacting and negatively regulating PTEN.

CONCLUSIONS

Abnormally high levels of DJ-1 expression may be involved in endometriosis, possibly by stimulating endometrial cell survival, proliferation, migration, and invasion.

Urinary peptide profiling identifies a panel of putative biomarkers for diagnosing and staging endometriosis

OBJECTIVE

To identify a potential diagnostic endometriosis marker using matrix-enhanced laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS)-based urinary proteomics.

DESIGN

Prospective randomized pilot study.

SETTING

University hospital, tertiary referral center for endometriosis.

PATIENT(S)

53 women undergoing laparoscopic surgery for pain and/or infertility comprising 30 women without endometriosis and 23 with endometriosis.

INTERVENTION(S)

Laparoscopy and urine specimens.

MAIN OUTCOME MEASURE(S)

Urinary peptide profiles.

RESULT(S)

We observed distinct patterns of peptide profiles in the urine samples of women presenting with typical clinical symptoms of endometriosis. Six statistically significant putative peptide markers were identified (four during the periovulatory phase and two during the luteal phase) by comparing controls with moderate/severe endometriosis patients. The periovulatory peptide mass of 1,767.1 Da and the luteal peptide mass of 1,824.3 Da both showed a sensitivity of 75% and a specificity of 85% and 71%, respectively. Also detected were seven peptide markers (two during the periovulatory phase and five during the luteal phase) by comparing the urinary peptide profiles of patients with minimal/mild to moderate/severe endometriosis. The periovulatory peptide mass of 3,280.9 Da and the luteal peptide mass of 1,933.8 Da showed a sensitivity of 82% and 75% and a specificity of 88% and 75%, respectively.

CONCLUSION(S)

Urinary proteomic analysis may provide a novel method of diagnosing and staging endometriosis.

Comparative analysis of Annexin A1-formyl peptide receptor 2/ALX expression in human leukocyte subsets

Recent studies have associated the dysregulated expression of Annexin-A1/Formyl peptide receptor 2 (FPR2/ALX) system with the development of autoimmune diseases. In this study we systematically scanned human leukocyte subsets for the presence of this pathway aiming to provide a roadmap that will help investigators to explore possible links between the development of immune related disorders and the expression of this system. Our results show that neutrophils, monocytes and NK cells express higher levels of both AnxA1 and FPR2/ALX compared to T or B cells. Further analysis of specific T cell subsets revealed higher levels in activated CD25(+) and memory CD45RO CD4 T cells compared to resting CD25(-) or naïve CD45RA CD4 T cells. Together the results expand our knowledge of the AnxA1-FPR2/ALX system in immune cells and provide new avenues for investigation into the functions of this signalling pathway in systems other than that classically described for neutrophils.

TRIzol treatment of secretory phase endometrium allows combined proteomic and mRNA microarray analysis of the same sample in women with and without endometriosis

BACKGROUND

According to mRNA microarray, proteomics and other studies, biological abnormalities of eutopic endometrium (EM) are involved in the pathogenesis of endometriosis, but the relationship between mRNA and protein expression in EM is not clear. We tested for the first time the hypothesis that EM TRIzol extraction allows proteomic Surface Enhanced Laser Desorption/Ionisation Time-of-Flight Mass Spectrometry (SELDI-TOF MS) analysis and that these proteomic data can be related to mRNA (microarray) data obtained from the same EM sample from women with and without endometriosis.

METHODS

Proteomic analysis was performed using SELDI-TOF-MS of TRIzol-extracted EM obtained during secretory phase from patients without endometriosis (n = 6), patients with minimal-mild (n = 5) and with moderate-severe endometriosis (n = 5), classified according to the system of the American Society of Reproductive Medicine. Proteomic data were compared to mRNA microarray data obtained from the same EM samples.

RESULTS

In our SELDI-TOF MS study 32 peaks were differentially expressed in endometrium of all women with endometriosis (stages I-IV) compared with all controls during the secretory phase. Comparison of proteomic results with those from microarray revealed no corresponding genes/proteins.

CONCLUSION

TRIzol treatment of secretory phase EM allows combined proteomic and mRNA microarray analysis of the same sample, but comparison between proteomic and microarray data was not evident, probably due to post-translational modifications.