DNA microarray analysis in a mouse model for endometriosis and validation of candidate factors with human adenomyosis

Endometriosis in the Mouse: Challenges and Progress Toward a ‘Best Fit’ Murine Model

Endometriosis is a prevalent gynecologic condition associated with pelvic pain and infertility characterized by the implantation and growth of endometrial tissue displaced into the pelvis via retrograde menstruation. The mouse is a molecularly well-annotated and cost-efficient species for modeling human disease in the therapeutic discovery pipeline. However, as a non-menstrual species with a closed tubo-ovarian junction, the mouse poses inherent challenges as a preclinical model for endometriosis research. Over the past three decades, numerous murine models of endometriosis have been described with varying degrees of fidelity in recapitulating the essential pathophysiologic features of the human disease. We conducted a search of the peer-reviewed literature to identify publications describing preclinical research using a murine model of endometriosis. Each model was reviewed according to a panel of ideal model parameters founded on the current understanding of endometriosis pathophysiology. Evaluated parameters included method of transplantation, cycle phase and type of tissue transplanted, recipient immune/ovarian status, iterative schedule of transplantation, and option for longitudinal lesion assessment. Though challenges remain, more recent models have incorporated innovative technical approaches such as in vivo fluorescence imaging and novel hormonal preparations to overcome the unique challenges posed by murine anatomy and physiology. These models offer significant advantages in lesion development and readout toward a high-fidelity mouse model for translational research in endometriosis.

Identification and analysis of novel endometriosis biomarkers via integrative bioinformatics

Endometriosis is a gynecological disease prevalent in women of reproductive age, and it is characterized by the ectopic presence and growth of the eutopic endometrium. The pathophysiology and diagnostic biomarkers of endometriosis have not yet been comprehensively determined. To discover molecular markers and pathways underlying the pathogenesis of endometriosis, we identified differentially expressed genes (DEGs) in three Gene Expression Omnibus microarray datasets (GSE11691, GSE23339, and GSE7305) and performed gene set enrichment analysis (GSEA) and protein-protein interaction (PPI) network analyses. We also validated the identified genes via immunohistochemical analysis of tissues obtained from patients with endometriosis or healthy volunteers. A total of 118 DEGs (79 upregulated and 39 downregulated) were detected in each dataset with a lower (fold change) FC cutoff (log2|FC| > 1), and 17 DEGs (11 upregulated and six downregulated) with a higher FC cutoff (log2|FC| > 2). KEGG and GO functional analyses revealed enrichment of signaling pathways associated with inflammation, complement activation, cell adhesion, and extracellular matrix in endometriotic tissues. Upregulation of seven genes (C7, CFH, FZD7, LY96, PDLIM3, PTGIS, and WISP2) out of 17 was validated via comparison with external gene sets, and protein expression of four genes (LY96, PDLIM3, PTGIS, and WISP2) was further analyzed by immunohistochemistry and western blot analysis. Based on these results, we suggest that TLR4/NF-κB and Wnt/frizzled signaling pathways, as well as estrogen receptors, regulate the progression of endometriosis. These pathways may be therapeutic and diagnostic targets for endometriosis.

IL-37 affects the occurrence and development of endometriosis by regulating the biological behavior of endometrial stromal cells through multiple signaling pathways

Endometriosis (EMs) is a chronic inflammatory condition. Interleukin (IL)-37 is a member of the IL-1 family and an anti-inflammatory cytokine. This study aimed to evaluate the possible role of IL-37 in the EMs pathogenesis. We investigated the in vivo effect of IL-37 on EMs by injection with recombinant human IL-37 (rhIL-37) into EMs mice. Furthermore, we evaluated the in vitro effects of IL-37 on proliferation, adhesion, migration and invasiveness of endometrial stromal cells (ESCs), and explored whether Wnt/β-catenin and mitogen-activated protein kinase (MAPK) pathways were involved in this process. In cultured ESCs, IL-37 overexpression significantly suppressed both protein and mRNA expression of the inflammation-associated cytokines, including IL-1β, IL-6, IL-10 and tumor necrosis factor (TNF-α). Furthermore, IL-37 overexpression significantly inhibited ESCs proliferation, adhesion, migration, invasion and the activity of matrix metalloproteinase (MMP)-2 and MMP-9. In contrast, knockdown of IL-37 exerted the opposite effects. Importantly, the IL-37-mediated action in ESCs was through inactivation of Wnt/β-catenin, p38 MAPK, extracellular signal-related kinases MAPK and c-Jun N-terminal kinase MAPK pathways. Moreover, EMs mice treated with rhIL-37 showed the decreased endometriotic-like lesion size and lesion weight, lower expression of IL-1β, IL-6, IL-10, TNF-α, vascular endothelial growth factor (VEGF), soluble intercellular adhesion molecule-I (ICAM-I) and MMP-2/9 activity in peritoneal fluid compared with the wide type (WT) EMs mice. These findings suggest that IL-37 suppresses cell proliferation, adhesion, migration and invasion of human ESCs through multiple signaling pathways, thereby affecting the occurrence and development of EMs.

The nervous system and genomics in endometriosis

Endometriosis is a gynaecological disease that occurs in approximately 10% to 15% of women of reproductive age and up to 47% of infertile women. The presence of implants of endometrial-like glands and stroma outside the uterus, characteristic of this disease, induce a wide variety of symptoms, mainly pelvic pain and infertility. Women suffering from this condition experience great distress, which significantly affects their quality of life. Numerous studies attempting to decipher the pathogenic mechanisms of endometriosis have been conducted around the world, yet its aetiology still remains unknown. It is widely believed that in women with endometriosis, the endometrium has characteristic features that allow the formation of implants once fragments have entered the peritoneal cavity through retrograde menstruation. Furthermore, a strong genetic tendency to develop the disease has been reported among patients and first-degree relatives. Thanks to the recent technological advances achieved in genomics and bioinformatics, a number of studies have had the potential to analyse several aspects of the pathogenesis of endometriosis from a genetic perspective. Due to the recent identification of nerve fibres in the endometrium of women with endometriosis, research on the neurogenesis of the disease has increased in the past few years. However, the genetic aspects of nerve growth in endometriosis have not been analysed in depth and further research providing important insights into the mechanisms that mediate pain in affected patients has the potential to contribute substantially to the future management of the condition.

The Association of Sonographic Evidence of Adenomyosis with Severe Endometriosis and Gene Expression in Eutopic Endometrium

STUDY OBJECTIVE

To examine the presence of sonographic evidence of adenomyosis (SEOA) in patients undergoing laparoscopic surgery for the investigation of endometriosis and to assess if there is an association between SEOA and endometriosis severity. Using gene expression analysis, we also aimed to determine if gene expression in eutopic endometria differed in patients with and without adenomyosis.

DESIGN

A prospective study (Canadian Task Force classification II-2).

SETTING

A tertiary medical center.

PATIENTS

Reproductive-age women who underwent laparoscopic surgery after presenting to a pelvic pain-focused gynecology clinic.

INTERVENTIONS

Endometrial tissue, detailed patient questionnaires, pathology, and surgical notes were collected. Sonographic data from tertiary ultrasounds performed up to 12 months before surgery were retrospectively added (n = 234, researchers blinded to surgical and pathological findings). Gene array data from endometrial biopsies (n = 41) were used to analyze differential gene expression; patients were divided into 2 groups according to the presence or absence of SEOA.

MEASUREMENTS AND MAIN RESULTS

Of the 588 patients recruited, 234 (40%) had an available pelvic scan and were included in this study. The average age of the included women was 30.6 years, with 35% having SEOA. Patients with SEOA were 5.4 years older (p = .02). There was no significant difference in the rates of endometriosis between groups; however, patients with SEOA were more likely to have stage IV endometriosis (41% vs 9.8%, p <.001). Patients with SEOA were also more likely to have other markers of severe endometriosis such as endometriomas and deep infiltrating endometriosis (p <.001). No significant difference was observed in endometrial gene expression between adenomyosis cases and controls after adjusting for menstrual c`ycle phases and the presence/absence of endometriosis.

CONCLUSION

Sonographic features of adenomyosis may be included as a component of the clinical assessment when attempting to predict the presence of severe endometriosis. No differences in gene expression were observed. Further research is needed to characterize uterine adenomyosis and to explore molecular pathways involved in its pathogenesis.

Molecular Characteristics of the Endometrium in Uterine Adenomyosis and Its Biochemical Microenvironment

Adenomyosis, which manifests with focally or diffusely scattered endometrial tissue within the uterine myometrium, is an endometriosis-like disease with controversial pathogenesis and compromised reproductive outcomes. This review, including the in vitro and in vivo studies performed on human or mouse models, is aimed to summarize the specific molecular characteristics of endometrium in the biochemical microenvironments of uterine adenomyosis. Many studies attributed the endometrium as the main cause of pathogenesis, with evidence of differential genetic expression and/or epigenetic modulation as well as estrogen-induced epithelial-mesenchymal transition. However, some studies indicated that the myometrium could play a role in the development of disease, based on findings of smooth muscle metaplasia and/or fibroblast-to-myofibroblast transdifferentiation by the influence of local biochemical factors. To date, it remains unclear whether adenomyosis is a genetically determined or a microenvironmentally induced disorder or whether the dysregulation of local factors may elicit the alteration of genetic expression in the endometrium. Similarly, it is uncertain whether the endometrial characteristics would remain consistent or could change along with a woman's reproductive life. Further longitudinal studies of the epigenetic controls or system biology are needed to elucidate the pathogenesis. Discovery of effective conservative treatments to improve the reproductive outcomes of patients with adenomyosis is still warranted.

Decreased Endometrial Expression of Leukemia Inhibitory Factor Receptor Disrupts the STAT3 Signaling in Adenomyosis During the Implantation Window

BACKGROUND

Adenomyosis was found to have negative impacts on embryo implantation. Leukemia inhibitory factor (LIF), proposed to be a molecular marker for endometrial receptivity, works through the LIF receptor (LIFR) on both the embryo and the endometrium. We aimed to evaluate the endometrial expression of LIF and LIFR and its subsequent signaling in patients with adenomyosis during the window of implantation (WOI).

METHODS

Endometrium was obtained during the WOI from patients with adenomyosis (age <45 years) who underwent hysterectomy and from age-matched controls who had no endometriosis or adenomyosis. The LIF and LIFR expressions were measured by polymerase chain reaction for messenger RNA expression, immunohistochemistry for protein intensity and localization, and immunofluorescent staining for colocalization. The ratio of signal transducer and activator of transcription 3 (STAT3) to extracellular signal-regulated kinase (ERK) phosphorylation was measured by Western blot of both the endometrium and the isolated human endometrial stromal cells (ESCs).

RESULTS

Patients with adenomyosis showed significantly and parallelly reduced LIF and LIFR expressions in the eutopic endometrium during WOI as compared with the control women and subsequently with remarkably reduced activation of STAT3 and ERK signaling. The significantly increased STAT3 and ERK phosphorylation induced by the LIF treatment in the cultured ESCs supported the linkage between the LIF-LIFR reaction and the signaling cascade.

CONCLUSION

Significant reduction in LIFR expression and the reduced activation of subsequent signaling strongly suggest a working model of how the implantation markers, LIF, may affect the endometrium of patients with adenomyosis. These molecular changes supported the declined implantation rates reported in patients with adenomyosis.

Genes Downregulated in Endometriosis Are Located Near the Known Imprinting Genes

There is now accumulating evidence that endometriosis is a disease associated with an epigenetic disorder. Genomic imprinting is an epigenetic phenomenon known to regulate DNA methylation of either maternal or paternal alleles. We hypothesize that hypermethylated endometriosis-associated genes may be enriched at imprinted gene loci. We sought to determine whether downregulated genes associated with endometriosis susceptibility are associated with chromosomal location of the known paternally and maternally expressed imprinting genes. Gene information has been gathered from National Center for Biotechnology Information database geneimprint.com. Several researchers have identified specific loci with strong DNA methylation in eutopic endometrium and ectopic lesion with endometriosis. Of the 29 hypermethylated genes in endometriosis, 19 genes were located near 45 known imprinted foci. There may be an association of the genomic location between genes specifically downregulated in endometriosis and epigenetically imprinted genes.

Calcium-binding protein expression in peritoneal endometriosis-associated nerve fibres

BACKGROUND

Recent studies demonstrated the potential involvement of nerve fibres in the chronic inflammatory process of endometriosis. We aimed to characterize nerve fibres in the proximal and distal areas of the peritoneal endometriotic lesions in order to understand the chronic inflammatory process in endometriosis.

METHODS

Peritoneal endometriotic lesions (proximal area) (n = 17), the matching unaffected peritoneum (distal area) and healthy peritoneum of patients without endometriosis (n = 15) were analysed with the neuronal markers PGP 9.5, calbindin, calretinin and parvalbumin. Peritoneal fluids of women with and without endometriosis were used for Western blot analysis and for the neuronal growth assay. The protein expression of neuronal PC-12 cells incubated with peritoneal fluids was analysed.

RESULTS

The overall nerve fibre density was significantly reduced in the distal area of the lesion when compared with the proximal area or with healthy peritoneum. The density of calbindin-, calretinin- and parvalbumin-positive nerve fibres was significantly increased in the endometriosis group. Calretinin expression was elevated in the peritoneal fluid of women with symptomatic endometriosis when compared with women with asymptomatic endometriosis. Furthermore, PC-12 cells incubated with peritoneal fluid of women with endometriosis showed a higher proliferation rate and a stronger neurite outgrowth than the control group. PC-12 cells incubated in peritoneal fluids of women with endometriosis expressed less calretinin but more calbindin than the control group.

CONCLUSIONS

Calcium-binding proteins seem to be increased in endometriosis-associated nerve fibres and might play an important role in the chronic inflammatory condition and the pain pathogenesis of endometriosis.