Microarray analysis provides insight into the early steps of pathophysiology of mouse endometriosis model induced by autotransplantation of endometrium

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.

The Pathogenesis of Endometriosis: Molecular and Cell Biology Insights

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

Antibiotic therapy with metronidazole reduces endometriosis disease progression in mice: a potential role for gut microbiota

STUDY QUESTION

Does altering gut microbiota with antibiotic treatment have any impact on endometriosis progression?

SUMMARY ANSWER

Antibiotic therapy reduces endometriosis progression in mice, possibly by reducing specific gut bacteria.

WHAT IS KNOWN ALREADY

Endometriosis, a chronic condition causing abdominal pain and infertility, afflicts up to 10% of women between the ages of 25 and 40, ~5 million women in the USA. Current treatment strategies, including hormone therapy and surgery, have significant side effects and do not prevent recurrences. We have little understanding of why some women develop endometriosis and others do not.

STUDY DESIGN, SIZE, DURATION

Mice were treated with broad-spectrum antibiotics or metronidazole, subjected to surgically-induced endometriosis and assayed after 21 days.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The volumes and weights of endometriotic lesions and histological signatures were analysed. Proliferation and inflammation in lesions were assessed by counting cells that were positive for the proliferation marker Ki-67 and the macrophage marker Iba1, respectively. Differences in faecal bacterial composition were assessed in mice with and without endometriosis, and faecal microbiota transfer studies were performed.

MAIN RESULTS AND THE ROLE OF CHANCE

In mice treated with broad-spectrum antibiotics (vancomycin, neomycin, metronidazole and ampicillin), endometriotic lesions were significantly smaller (~ 5-fold; P < 0.01) with fewer proliferating cells (P < 0.001) than those in mice treated with vehicle. Additionally, inflammatory responses, as measured by the macrophage marker Iba1 in lesions and IL-1β, TNF-α, IL-6 and TGF-β1 in peritoneal fluid, were significantly reduced in mice treated with broad-spectrum antibiotics (P < 0.05). In mice treated with metronidazole only, but not in those treated with neomycin, ectopic lesions were significantly (P < 0.001) smaller in volume than those from vehicle-treated mice. Finally, oral gavage of faeces from mice with endometriosis restored the endometriotic lesion growth and inflammation (P < 0.05 and P < 0.01, respectively) in metronidazole-treated mice.

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

These findings are from a mouse model of surgically-induced endometriosis. Further studies are needed to determine the mechanism by which gut bacteria promote inflammation, identify bacterial genera or species that promote disease progression and assess the translatability of these findings to humans.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that gut bacteria promote endometriosis progression in mice. This finding if translated to humans, could aid in the development of improved diagnostic tools and personalised treatment strategies.

STUDY FUNDING AND COMPETING INTEREST(S)

This work was funded, in part, by: a National Institutes of Health (NIH)/ National Institute of Child Health and Human Development (NICHD) grant (R00HD080742) to RK; Washington University School of Medicine start-up funds to RK; an Endometriosis Foundation of America Research Award to R.K.; and an NIH/NICHD grant (R01HD091218) to IUM. The authors report no conflict of interest.

Trauma and endometriosis. A review. May we explain surgical phenotypes and natural history of the disease?

OBJECTIVE

The study was performed to evaluate whether trauma is an initial event of development of endometriosis.

METHOD

Using Medline database from January 1960 up to December 2014, a systematic review was made of all published studies using the keywords trauma, healing, injury, infection, hyperperistaltism, stretch and endometriosis, adenomyosis and trauma. Studies and review articles written in French and/or in English related to the topic were included and reviewed independently by two authors.

RESULTS

The role of trauma is well-established for endometriotic lesions diagnosed in surgical scars. Various traumas including delivery, uterine curettage or incision, intraperitoneal hemorrhage, or occult pelvic inflammatory diseases could be involved to explain other localizations of the disease. Many data suggested that the healing process, particularly growth factors and the associated estrogen production, may facilitate the implantation and the growth of ectopic endometrial cells. After the initial, a traumatic event, the phenotype of the disease would depend on the tissue in which the endometriotic lesion grows.

CONCLUSIONS

The present literature review may support a potential role of a trauma as an initial event of endometriosis.

Uterine Leukocyte Function and Dysfunction: A Hypothesis on the Impact of Endometriosis

Endometriosis is a chronic inflammatory disease characterized by the growth of endometrial glands and stroma outside of the uterus. The disease affects approximately 10-15% of women of reproductive age and presents with clinical symptoms of pelvic pain and infertility. Changes in the leukocyte populations within the ectopic tissue and eutopic endometrium have been reported, and data suggest these alterations contribute to the pathology and symptoms of the disease. In this review, we discussed differences when comparing uterine NK cells and regulatory T cells within the eutopic endometrium between patients with endometriosis and healthy patients, and how these differences relate to implantation failure and/or decreased clearance of menstrual tissue in patients with the disease. The data demonstrate a critical need to examine endometrium and menstrual tissue in patients with endometriosis excluded from studies examining unknown causes of infertility and heavy menstrual bleeding. The information gathered from excluded patients will further enhance our understanding of how the immune system contributes to the pathophysiology of endometriosis and help to identify biomarkers for patients at higher risk for developing endometriosis-associated infertility.

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

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

Activated AKT pathway promotes establishment of endometriosis

The pathogenesis of endometriosis remains unclear, and relatively little is known about the mechanisms that promote establishment and survival of the disease. Previously, we demonstrated that v-akt murine thymoma viral oncogene homolog (AKT) activity was increased in endometriosis tissues and cells from ovarian endometriomas and that this increase promoted cell survival as well as decreased levels of progesterone receptor. The objective of this study was to demonstrate a role for AKT in the establishment of ectopic lesions. First, a dose-dependent inhibition of AKT in stromal cells from human ovarian endometriomas (OSIS) as well as endometrial stromal cells from disease-free patients (ESC) with the allosteric AKT inhibitor MK-2206 was demonstrated by decreased levels of phosphorylated (p)(Ser473)-AKT. Levels of the AKT target protein, p(Ser256)-forkhead box O1 were increased in OSIS cells, which decreased with MK-2206 treatment, whereas levels of p(Ser9)-glycogen synthase kinase 3β did not change in response to MK-2206. Although MK-2206 decreased viability of both OSIS and ESC in a dose-dependent manner, proliferation of OSIS cells was differentially decreased significantly compared with ESC. Next, the role of hyperactive AKT in the establishment of ectopic lesions was studied using the bigenic, PR(cre/+)Pten(f/+) heterozygous mouse. Autologous implantation of uterine tissues was performed in these mice. After 4 weeks, an average of 4 ± 0.33 lesions per Pten(f/+) mouse and 7.5 ± 0.43 lesions in the PR(cre/+)Pten(f/+) mouse were found. Histological examination of the lesions showed endometrial tissue-like morphology, which was similar in both the Pten(f/+) and PR(cre/+)Pten(f/+) mice. Treatment of mice with MK-2206 resulted in a significantly decreased number of lesions established. Immunohistochemical staining of ectopic lesions revealed decreased p(Ser473)-AKT and the proliferation marker Ki67 from MK-2206-treated mice compared with vehicle-treated mice. Furthermore, levels of FOXO1 and progesterone receptor increased in lesions of mice receiving MK-2206. These results demonstrate that heightened AKT activity plays an active role in the establishment of ectopic endometrial tissues.

Effect of high-fat diet prior to pregnancy on hepatic gene expression and histology in mouse offspring

Maternal overnutrition and obesity are associated with fetal development and cause long-term effects in offspring. However, the effects of a high-fat diet specific to the pre-pregnancy period are not determined. The present study aimed to examine the effect of high-fat diet prior to pregnancy on the liver of mouse offspring. Female C57BL/6J mice were fed a normal chow (15.2% fat by energy) [control diet (CTR) and CTR pre-pregnancy (PP) groups] or a high-fat chow (31.2% fat by energy) [high-fat diet (HFD) and HFD-pre-pregnancy (PP) groups] for 3-4 weeks and then mated with male C57BL/6J mice fed normal chow. Some mothers continued on the same diet until pups reached 21 days of age (CTR and HFD), and others were fed the different chows from gestational day 0 (CTR-PP and HFD-PP) to determine the effects of a high-fat diet during the pre-pregnancy period in HFD-PP/CTR and HFD/CTR-PP comparisons. Liver tissues from pups were subjected to gene expression analysis by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and microarray, and histological analysis using Oil Red O staining (Sigma Chemical Co., Ltd., Balcatta, WA, USA). Lipid droplets were increased in hepatocytes of mice in HFD-PP compared to CTR and those in HFD compared to CTR-PP. Expression of stearoyl-coenzyme A desaturase 1 (Scd1), acetyl-coenzyme A carboxylase beta (Acacb), and fatty acid binding protein 5 (Fabp5) was increased by maternal high-fat diet during pre-pregnancy. The results showed that maternal high-fat diet intake prior to pregnancy uniquely affects metabolic phenotype related to health and disease in the liver of the next generation.

Evaluation of the testicular toxicity of prenatal exposure to bisphenol A based on microarray analysis combined with MeSH annotation

Bisphenol A (BPA) is known to be an endocrine disruptor that affects the development of reproductive system. The aim of the present study was to investigate a group of testicular genes dysregulated by prenatal exposure to BPA. Pregnant ICR mice were treated with BPA by subcutaneous administration on days 7 and 14 of pregnancy. Tissue and blood samples were collected from 6-week-old male offspring. Testes were subjected to gene expression analysis using a testis-specific microarray (Testis2), consisting of 2,482 mouse cDNA clones annotated with Medical Subject Headings (MeSH) terms indicative of testicular components and functions. To interpret the microarray data, we used the MeSH terms significantly associated with the altered genes. As a result, MeSH terms related to androgens and Sertoli cells were extracted in BPA-treated groups. Among the genes related to Sertoli cells, downregulation of Msi1h, Ncoa1, Nid1, Hspb2, and Gata6 were detected in the testis of mice treated with BPA (twice administered 50 mg/kg). The MeSH terms associated with this group of genes may provide useful means to interpret the testicular toxicity of BPA. This article concludes that prenatal BPA exposure downregulates expression of genes associated with Sertoli cell function and affects the reproductive function of male offspring. Additionally, a method using MeSH to extract a group of genes was useful for predicting the testicular and reproductive toxicity of prenatal BPA exposure.

Expression profile of extracellular matrix and adhesion molecules in the development of endometriosis in a mouse model

Ectopic endometrial tissue induces various reactions in surrounding tissues, such as the surface of the ovary and peritoneal cavity, leading to endometriosis. The aim of this study is to investigate the expression profile of extracellular matrix (ECM) and adhesion molecules in the early steps of development of experimental mouse endometriosis, specifically in peritoneum adjacent to endometrium transplants attached via autotransplantation. The endometriosis model was induced by autotransplantation of endometrium to peritoneal tissue. Peritoneal tissues adjacent to the transplant were obtained at 1, 4, and 7 days posttransplantation. The results showed that messenger RNA expression levels of most of the integrins, collagens, and other ECM reached a peak at 7 days posttransplantation. Uniquely, Lamc2 was significantly increased to its maximum level within 24 hours posttransplantation and may be strongly associated with initiation of the development of endometriosis. These data will be helpful in further investigations of the treatment of endometriosis.

Evaluation of testicular toxicology of doxorubicin based on microarray analysis of testicular specific gene expression

Testicular toxicity of chemical substances has been generally assessed by sperm properties and histology. However, the methods can provide only a few information of the mechanism of the toxicity. The aim of this study is to show a method that can evaluate an overview of testicular toxic mechanisms using a tissue-specific microarray and classification of genes using Medical Subject Headings (MeSH). Male ICR mice (6 weeks old) were treated with doxorubicin hydrochloride (0, 0.1, 0.3 mg/kg/time, three times per week) by subcutaneous injection for 6 weeks (until 11 weeks old). Six weeks after the final administration, tissue and blood samples were obtained. Testes were subjected to gene expression analysis using quantitative RT-PCR and cDNA microarray (testis2). To interpret the microarray data, genes were classified using MeSH related to the functions of testis and sperm. Doxorubicin (both 0.1 and 0.3 mg/kg group) induced a decrease in sperm normal morphology and mortality, daily sperm production, and the number of Sertoli cells in the seminiferous tubules. Quantitative RT-PCR and microarray analysis showed dysregulation of mRNA expression levels of genes related to Sertoli cells, germ cells and spermatogenesis. Analysis of microarray data showed a significant enrichment of a total of ten MeSH categories including Spermatogenesis, Sertoli cells, Germ cells and Male infertility. This article concluded that analysis using testicular specific microarray combined with MeSH showed a more comprehensive overview of testicular toxic mechanisms than existing methods; i.e., examination of sperm properties and the histological examinations.

Induction of endometriosis alters the peripheral and endometrial regulatory T cell population in the non-human primate

BACKGROUND

Endometriosis is a gynecological condition that is characterized by extreme abdominal pain and also decreased fertility. Regulatory T cells (Tregs) have immunosuppressive activity critical for embryonic implantation and likewise the acceptance of tissue engraftment. Utilizing the induced non-human primate (Papio anubis) model of endometriosis, we hypothesize that endometriosis decreases the peripheral and endomet rial Treg profile, whereas ectopic lesions have increased Treg localization.

METHODS

Peripheral blood and endometrium were obtained throughout the menstrual cycle prior to and after induction of disease. Animals were randomly assigned to control (n = 7) or diseased (n = 16) treatment groups. Endometriosis was induced by i.p. injection of autologous menstrual tissue for 2 consecutive months during menses. Peripheral blood and endometrial tissue were collected at d9-11PO at 1, 3, 6, 9, 12 and 15 months post-induction of disease for fluorescence-activated cell sorting, quantitative RT-PCR and immunohistochemistry. Ectopic lesions were excised at 1 and 6 months post-inoculation and also harvested at necropsy (15 months) and processed for RNA of IHC. Identification of Tregs through analysis of FOXP3 expression was conducted utlilizing several methodologies. Differences were determined by non-parametric statistical analysis between all treatment groups and time points.

RESULTS

In control animals, the proportion of peripheral natural Tregs (nTregs) was reduced (P < 0.05) during the mid- and late secretory stages of the menstrual cycle compared with menses. The induction of disease decreased peripheral Treg expression at early time points (P < 0.05) and this remained low throughout the time course, compared with the pre-inoculatory level of an individual. FOXP3 gene expression and Treg populations were also decreased in the eutopic endometrium (P < 0.05) compared with control animals, whereas these parameters were increased in ectopic lesions (P < 0.05), compared with the eutopic endometrium.

CONCLUSIONS

Our data suggest that a reduction in peripheral Tregs may be a causative factor for endometriosis-associated infertility, while the increase in ectopic Treg expression may aid lesion development. Furthermore, endometriosis appears to disrupt Treg recruitment in both eutopic and ectopic endometrium.

New insights into the pathophysiology of endometriosis: from chronic inflammation to danger signal

BACKGROUND

Various theories try to explain the development and progression of endometriosis, however, no single theory can explain all aspects of this disorder. Gene expression profiling studies might reveal factors that explain variability in disease development and progression, which can serve as specific biomarkers for endometriosis and novel drug development. We have recently showed that the upregulated genes were predominantly clustered in stress and detoxification, providing a mechanistic explanation for the oxidative stress and chronic inflammatory response in endometriosis.

OBJECTIVE

This review aims: (1) to analyse the published data, with the aim of identifying pathways consistently regulated by the endometriosis genotype and (2) to summarise the findings of specific genes, which are involved in the process of oxidative stress and inflammation.

METHODS

We identified gene array and proteomics studies whose data were accessible in PubMed.

RESULTS

A major finding is the increased expressions of several markers including heat shock protein, S100, fibronectin, and neutrophil elastase, which might be involved in the process of Toll-like receptor (TLR)-dependent sterile inflammation. The study reviews a convergence in the main pathogenic process, where the TLR-mediated inflammation occurs possibly through the endogenous ligands.

CONCLUSIONS

In conclusion, a circulus vitiosus of both the oxidative stress pathway and the TLR pathways is generated when the process becomes chronic (danger signal spiral).

Endometriosis research: animal models for the study of a complex disease

Endometriosis is a common gynaecological disease that is characterized and defined as the presence of endometrial tissue outside the uterus, causing painful periods and subfertility in approximately 10% of women. After more than 50 years of research, little is known about the mechanisms underlying the development and establishment of this condition. Animal models allow us to study the temporal sequence of events involved in disease establishment and progression. Also, because this disease occurs spontaneously only in humans and non-human primates and there are practical problems associated with studying the disease, animal models have been developed for the evaluation of endometriosis. This review describes the animal models for endometriosis that have been used to date, highlighting their importance for the investigation of disease mechanisms that would otherwise be more difficult to elucidate, and proposing new alternatives aimed at overcoming some of these limitations.

Maternal exposure to nanoparticulate titanium dioxide during the prenatal period alters gene expression related to brain development in the mouse

Background

Nanotechnology is developing rapidly throughout the world and the production of novel man-made nanoparticles is increasing, it is therefore of concern that nanomaterials have the potential to affect human health. The purpose of this study was to investigate the effects of maternal exposure to nano-sized anatase titanium dioxide (TiO₂) on gene expression in the brain during the developmental period using cDNA microarray analysis combined with Gene Ontology (GO) and Medical Subject Headings (MeSH) terms information.

Results

Analysis of gene expression using GO terms indicated that expression levels of genes associated with apoptosis were altered in the brain of newborn pups, and those associated with brain development were altered in early age. The genes associated with response to oxidative stress were changed in the brains of 2 and 3 weeks old mice. Changes of the expression of genes associated with neurotransmitters and psychiatric diseases were found using MeSH terms.

Conclusion

Maternal exposure of mice to TiO₂ nanoparticles may affect the expression of genes related to the development and function of the central nervous system.

The non-human primate model of endometriosis: research and implications for fecundity

The development of an animal model of endometriosis is crucial for the investigation of disease pathogenesis and therapeutic intervention. These models will enhance our ability to evaluate the causes for the subfertility associated with disease and provide a first-line validation of treatment modulators. Currently rodents and non-human primate models have been developed, but each model has their limitations. The aim of this manuscript is to summarize the current findings and theories on the development of endometriosis and disease progression and the effectiveness of therapeutic targets using the experimental induced model of endometriosis in the baboon (Papio anubis).