Cytokine and chemokine expression in a rat endometriosis is similar to that in human endometriosis

Cytokine and chemokine profiles in women with endometriosis, polycystic ovary syndrome, and unexplained infertility

Numerous factors (including immunological, congenital, hormonal, and morphological disorders) can lead to infertility. In this regard, 3 specific diseases associated with infertility are discussed in this review study (i.e., polycystic ovary syndrome [PCOS], endometriosis [EMS], and unexplained infertility [UI]). PCOS is a common endocrine disorder characterized by chronic low-grade inflammation, and EMS is a benign disease characterized by the presence of ectopic endometrial tissue. UI refers to couples who are unable to conceive for no known reason. Conception and pregnancy are significantly affected by the immune system; in this regard, chemokines and cytokines play important roles in the regulation of immune responses. Patients with PCOS, EMS, and UI have altered cytokine and chemokine profiles, suggesting that dysregulation of these molecules may contribute to infertility in these conditions. Accordingly, the issue of infertility is addressed in this review study, a condition that affects approximately 16% of couples worldwide.

Establishment of endometriotic models: the past and future

Endometriosis is a prevalent chronic disease that affects approximately 6% to 10% of reproductive-aged women. Although numerous researchers have endeavored to explore the etiology of endometriosis over a century, its etiology still remains an enigma. The exploration of pathophysiologic mechanism and novel therapy for endometriosis depends on ideal endometriotic models. In the previous decade, various endometriotic models have been established; therefore, we made a conclusion for available information on these models. This review summarized the common experimental models used in endometriotic studies, including their origins, characteristics, applications, and limitations. Endometriotic models played an important role in studying etiologies and novel treatments of endometriosis during the last decades. Among them, animal models and endometriotic cell lines were viewed as most common studying tools to explore the intrinsic entities of endometriosis. In addition, endometrial organoid also emerged and was regarded as an ideal studying tool for endometriosis research. Different research models collectively complement each other to advance the endometriosis research. The successful establishment of endometrial organoids means that organoids are expected to become an ideal model for studying endometriosis in the future.

Expression of monocyte chemotactic protein 2 and tumor necrosis factor alpha in human normal endometrium and endometriotic tissues

Endometriosis is a gynocological disease characterized by the presence of the endometrial glands and stroma outside the uterine cavity. This disease affects % 6-10 of women with reproductive age and it causes serious problems such as pelvic pain, dysmenorrhea and infertility. Although endometriosis is one of the most investigated disease of gynecology, its pathogenesis is not clear completely. In recent years, many studies revealed the inflammatory nature of endometriosis. Many of the immune cells and their secretory products cytokines and chemokines has been detected in body fluids of women with endometriosis. Cytokines are protein or glycoprotein in structures and hormon-like molecules that act generally in a paracrine fashion to regulate immun responses. They involved in chemotaxis, cell proliferation, cell activation, motility, adhesion and morphogenesis. Tumor necrosis factor alpha (TNF-α) is a proinflammatory cytokine secreted by the macrophages, monocytes, neutrophiles, T cells and natural killer cells. It stimulates increase in the level of the chemokines in body fluids. Monocyte chemotactic protein 2 (MCP-2) is a chemokine act to recruit and activate monocytes into sites of inflammation area. The aim of this study to investigate the ultrastructural properties and whether the expression and localization of TNF-α and MCP-2 in the eutopic endometrium (normal endometrium of women with endometriosis) and endometritic tissues of women with endometriosis. Eutopic endometrial and endometriotic tissue samples were obtained from women with endometriosis between 20-41 y and normal endometrial tissues were collected from 5 women without endometriosis as a control group. Tissues were processed for light and electron microscopy and examined. The epithelial cells of endometriotic tissues were revealed strongly cytoplasmic TNF-α and MCP-2 immunreactivities. Eutopic endometrial tissues were also stained prominently for both TNF-α and MCP-2. Furthermore, a significant increase in stromal macrophages were observed in endometriotic tissues. Moreover, the ultrastructural observations on the normal and endometriotic tissues were exhibited microvilli-rich cells and ciliated cells. These findings suggest that TNF-α and MCP-2 may be involved in normal endometrial biology and in the pathogenesis of endometriosis.

Endometriosis-Associated Pain - Do Preclinical Rodent Models Provide a Good Platform for Translation?

Pelvic pain is a common symptom of endometriosis. Our understanding of its etiology remains incomplete and medical management is limited by poor translation from preclinical models to clinical trials. In this review, we briefly consider the evidence, or lack thereof, that different subtypes of lesion, extra-uterine bleeding, and neuropathic pathways add to the complex and heterogeneous pain experience of women with the condition. We summarize the studies in rodent models of endometriosis that have used behavioral endpoints (evoked and non-evoked) to explore mechanisms of endometriosis-associated pain. Lesion innervation, activation of nerves by pronociceptive molecules released by immune cells, and a role for estrogen in modulating hyperalgesia are key endometriosis-associated pain mechanisms replicated in preclinical rodent models. The presence of ectopic (full thickness uterus or endometrial) tissue may be associated with changes in the spinal cord and brain, which appear to model changes reported in patients. While preclinical models using rats and mice have yielded insights that appear relevant to mechanisms responsible for the development of endometriosis-associated pain, they are limited in scope. Specifically, most studies are based on models that only resulted in the formation of superficial lesions and use induced (evoked) behavioral 'pain' tests. We suggest that translation for patient benefit will be improved by new approaches including models of ovarian and deep infiltrating disease and measurement of spontaneous pain behaviors. Future studies must also capitalize on new advances in the wider field of pain medicine to identify more effective treatments for endometriosis-associated pain.

Development of a domestic animal model for endometriosis: Surgical induction in the dog, pigs, and sheep

Background:

Endometriosis affects one in ten women of reproductive age but it is diagnosed at advanced stages. Our objective was to develop a domestic animal model that would permit sequential assessment of endometriotic changes.

Materials and methods:

Surgical transplantation of endometrial tissue and fat (n = 4 grafts/tissue/animal) was done in dogs (n = 5), pigs (n = 4), and sheep (n = 5). Autologous grafts were sutured to the visceral (urinary bladder in dogs and pigs and uterus in sheep) and parietal peritoneum. Sham surgeries were performed (dogs and sheep n = 5 and pigs n = 3) by placing fat grafts alone. Plasma estrogen and progesterone concentration was performed prior to surgery and weekly following surgery until euthanasia. Animals were euthanized between 80 and 110 days after surgery. Gross and histopathologic features of endometriotic lesions were recorded.

Results:

A variety of lesions from transplanted endometrial grafts included endometriotic cysts, vesicles, solid lesions, or absence of lesions. The proportion of cysts was greater (p < 0.01) in dogs (18/20 grafts) than in pigs (5/16) and sheep (5/20). The area of endometriotic lesions at the time of euthanasia was greater than at the time of surgery in dogs (0.89 ± 0.11 cm2 vs 0.50 ± 0.09 cm2; p < 0.05), whereas, the size of lesions decreased (p < 0.05) by half or more in pigs and sheep. In dogs, endometrial cysts were characterized by simple cuboidal/columnar epithelium, endometrial glands, stromal tissue with hemorrhage and/or hemosiderin-laden macrophages, and smooth muscle cells.

Conclusion:

The development of endometriotic cysts was apparent in dogs than in sheep and pigs. Therefore, dog is a better domestic animal model for endometriosis.

Relevant human tissue resources and laboratory models for use in endometriosis research

Endometriosis is characterized by the growth of endometrium‐like tissue outside the uterus, most commonly on the pelvic peritoneum and ovaries. Although it may be asymptomatic in some women, in others it can cause debilitating pain, infertility or other symptoms including fatigue. Current research is directed both at understanding the complex etiology and pathophysiology of the disorder and at the development of new nonsurgical approaches to therapy that lack the unwanted side effects of current medical management. Tools for endometriosis research fall into two broad categories; patient‐derived tissues, and fluids (and cells isolated from these sources) or models based on the use of cells or animals. In this review, we discuss the literature that has reported data from the use of these tools in endometriosis research and we highlight the strengths and weaknesses of each. Although many different models are reported in the literature, hypothesis‐driven research will only be facilitated with careful experimental design and selection of the most appropriate human tissue from patients with and without endometriosis and combinations of physiologically relevant in vitro and in vivo laboratory models.

Endometriosis-associated changes in serum levels of interferons and chemokines

BACKGROUND/AIM

The aim of the study was to evaluate the serum concentration of main chemokines and interferons in patients with diagnosed endometriosis.

MATERIALS AND METHODS

A total of 160 women were divided in two study groups (group 1 - endometriosis; group 2 - healthy women). Serum levels of IFN-α, IFN-γ, MCP-1, MIP-1α, MIP-1β, RANTES, eotaxin, IL-8, MIG, IP-10, and IL-17A were measured with Human Multiplex Cytokine Panels. Results. Serum levels of IFN-γ, MCP-1, and IL-8 were significantly higher (mean 14.03, 57.24, and 534.24, respectively, compared to 0.58, 20.51, and 259.82, respectively), and serum levels of IP-10 and eotaxin were significantly lower in women with endometriosis compared to the controls (mean 1.15 and 1.01, respectively, compared to 3.90 and 3.22, respectively). Conclusions. According to our results women with endometriosis have elevated levels IFN-γ, MCP-1, and IL-8, and lower serum levels of IP-10 and eotaxin, indicating unbalanced immune activity in endometriosis.

Sciatic endometriosis induces mechanical hypersensitivity, segmental nerve damage, and robust local inflammation in rats

BACKGROUND

Endometriosis is a common cause of pain including radicular pain. Ectopic endometrial tissue may directly affect peripheral nerves including the sciatic, which has not been modelled in animals.

METHODS

We developed a rat model for sciatic endometriosis by grafting a piece of autologous uterine tissue around the sciatic nerve. Control animals underwent a similar surgery but received a graft of pelvic fat tissue.

RESULTS

The uterine grafts survived and developed fluid-filled cysts; the adjacent nerve showed signs of swelling and damage. Mechanical and cold hypersensitivity and allodynia of the ipsilateral hindpaw developed gradually over the first 2 weeks after the surgery, peaked at 2-5 weeks, and was almost resolved by 7 weeks. Control animals showed only minor changes in these pain behaviours. Histological signs of inflammation in the uterine graft and in the adjacent nerve were observed at 3 weeks but were resolving by 7 weeks. In vivo fibre recording showed increased spontaneous activity, especially of C-fibres, in sciatic nerve proximal to the uterine graft. Several pro-inflammatory cytokines including interluekin-18, VEGF, fractalkine, and MIP-1α, were elevated in the uterine graft plus sciatic nerve samples, compared to samples from normal nerve or nerve plus fat graft. Growth associated protein 43 (GAP43), a marker of regenerating nerve fibres, was observed in the adjacent sciatic nerve as well as in the uterine graft.

CONCLUSIONS

This model shared many features with other rat models of endometriosis, but also had some unique features more closely related to neuropathic pain models.

WHAT DOES THIS STUDY/REVIEW ADD

Some especially painful forms of endometriosis are essentially neuropathic, because peripheral nerves are directly affected by nearby ectopic endometrial tissue. We modelled endometriosis by implanting autologous uterine tissue around rat sciatic nerve. We observed mechanical and cold pain behaviours along with signs of inflammation and nerve damage and increased pro-inflammatory cytokines at the implant site. Pain behaviours correlated with signs of nerve inflammation and damage rather than with cyst survival.

Lipoxin A4 suppresses the development of endometriosis in an ALX receptor-dependent manner via the p38 MAPK pathway

BACKGROUND AND PURPOSE

Lipoxins can function as endogenous 'breaking signals' in inflammation and play important roles in the progression of endometriosis. In this study, we further investigated the molecular mechanism by which lipoxin A4 (LXA4 ) suppresses the development of endometriosis.

EXPERIMENTAL APPROACH

Primary endometriotic stromal cells (ESCs) were treated with IL-1β, or pre-incubated with LXA4 before incubation with IL-1β. The LXA4 receptor (ALX receptor) antagonist Boc-2 and gene-silencing approaches were used to study the involvement of the ALX receptor in anti-inflammatory signalling responses in ESCs. An animal model of endometriosis was induced in BALB/c mice by i.p. injection of an endometrium-rich fragment.

KEY RESULTS

Decreased levels of LXA4 and 15-LOX-2 expression but increased expression of AXL receptors were observed in endometriotic tissues. LXA4 inhibited the release of inflammatory factors and phosphorylation of p38 MAPK in IL-1β-induced ESCs, an effect mediated by ALX receptors. LXA4 inhibited the proliferation of ESCs, as indicated by reduced DNA replication, caused G0 /G1 phase cell cycle arrest and down-regulated the expression of proliferating cell nuclear antigen in ESCs. LXA4 also attenuated the invasive activity of ESCs mainly by suppressing the expression and activity of MMP-9. In vivo, we further confirmed that LXA4 could inhibit the progression of endometriosis by acting as an anti-inflammatory.

CONCLUSIONS AND IMPLICATIONS

LXA4 exerted anti-inflammatory, anti-proliferative and anti-invasive effects on endometriosis through a mechanism that involved down-regulating the activities of p38 MAPK, which was mediated by ALX receptors.

Upregulation of α₂δ-1 Calcium Channel Subunit in the Spinal Cord Contributes to Pelvic Organ Cross-Sensitization in a Rat Model of Experimentally-Induced Endometriosis

Pelvic organ cross-sensitization, also termed as viscero-visceral referred hyperalgesia, is a major contributor to painful endometriosis. Its underlying mechanism is poorly understood. Clinical and basic studies have shown that gabapentin, a drug that binds to the α2δ-1 subunit of voltage-dependent calcium channels (Cavα2δ-1), is effective in treating chronic visceral pain. Accordingly, we hypothesized that pelvic organ cross-sensitization in painful endometriosis is mediated by an upregulation of Cavα2δ-1 in the spinal cord. We examined if the dysregulation of spinal Cavα2δ-1 subunit may play an important role in the development of ectopic growths-to-colon cross-sensitization in a rat model of experimentally-induced endometriosis. Our findings suggest that there was an increased Cavα2δ-1 expression in the dorsal horn and an ectopic growths-to-colon cross-sensitization in female rats with established endometriosis. Intrathecal administration of gabapentin (300 μg) remarkably reduced the ectopic growths-to-colon cross-sensitization in rats with established endometriosis. Furthermore, intrathecal injection of Cavα2δ-1 antisense oligodeoxynucleotides reversed the ectopic growths-to-colon cross-sensitization and also normalized the upregulation of spinal Cavα2δ-1 expression in endometriosis rats. The current study suggests that the upregulation of Cavα2δ-1 in the spinal cord may contribute to pelvic organ cross-sensitization in painful endometriosis. Our study may provide a biological basis for selectively targeting this pathway to relieve viscero-visceral referred hyperalgesia in patients with painful endometriosis.

Screening the role of pronociceptive molecules in a rodent model of endometriosis pain

Chronic pain is a major symptom in patients with endometriosis, a common gynecologic condition affecting women in their reproductive years. Although many proalgesic substances are produced by endometriosis lesions, experimental evidence supporting their relative roles is still lacking. Furthermore, it is unclear whether these proalgesic agents directly activate nociceptors to induce endometriosis pain. To determine their relative contribution to pain associated with endometriosis, we evaluated the intrathecal administration of oligodeoxynucleotides (ODNs) antisense to messenger RNA for receptors for 3 pronociceptive mediators known to be produced by the ectopic endometrium. Two weeks after the implant of autologous uterine tissue onto the gastrocnemius muscle, local mechanical hyperalgesia was observed in operated rats. Intrathecal antisense ODN targeting messenger RNA for the interleukin 6 receptor-signaling complex subunit glycoprotein 130 and the nerve growth factor tyrosine kinase receptor A, but not their mismatch ODNs, reversibly attenuated mechanical hyperalgesia at the implant site. In contrast, intrathecal antisense ODN targeting the tumor necrosis factor receptor 1, at a dose that markedly inhibited intramuscularly injected tumor necrosis factor alpha, had only a small antihyperalgesic effect in this model. These results indicate the relative contribution of pronociceptive mediators produced by ectopic endometrial tissue to endometriosis pain. The experimental approach presented here provides a novel method to evaluate for the differential contribution of mediators produced by other painful lesions as well as endometriosis lesions as targets for novel treatment of pain syndromes.

PERSPECTIVE

This article presents evidence for the relative contribution of proalgesic mediators to primary hyperalgesia displayed by rats submitted to a model of endometriosis pain. This approach can be used to identify potential targets for the treatment of endometriosis pain.

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.

Ectopic uterine tissue as a chronic pain generator

While chronic pain is a main symptom in endometriosis, the underlying mechanisms and effective therapy remain elusive. We developed an animal model enabling the exploration of ectopic endometrium as a source of endometriosis pain. Rats were surgically implanted with autologous uterus in the gastrocnemius muscle. Within two weeks, visual inspection revealed the presence of a reddish-brown fluid-filled cystic structure at the implant site. Histology demonstrated cystic glandular structures with stromal invasion of the muscle. Immunohistochemical studies of these lesions revealed the presence of markers for nociceptor nerve fibers and neuronal sprouting. Fourteen days after surgery rats exhibited persistent mechanical hyperalgesia at the site of the ectopic endometrial lesion. Intralesional, but not contralateral, injection of progesterone was dose-dependently antihyperalgesic. Systemic administration of leuprolide also produced antihyperalgesia. In vivo electrophysiological recordings from sensory neurons innervating the lesion revealed a significant increase in their response to sustained mechanical stimulation. These results are consistent with clinical and pathological findings observed in patients with endometriosis, compatible with the ectopic endometrium as a source of pain. This model of endometriosis allows mechanistic exploration at the lesion site facilitating our understanding of endometriosis pain.

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.

Pathological study for the effects of in utero and postnatal exposure to diesel exhaust on a rat endometriosis model

Previous studies have shown that prenatal and postnatal exposure to diesel exhaust (DE), which is known to be one of the main constituents of air pollution, enhances the persistence of endometriosis in a rat model. The aim of this study is to investigate the pathological changes induced by DE exposure in a rat model of endometriosis. Pregnant Sprague-Dawley rats were exposed to DE or clean air beginning on gestational day 2 and neonatal rats were persistently exposed to DE or clean air. Endometriosis was induced by autotransplantation of endometrium onto the peritoneum of eight-week-old female offspring. Endometriotic lesions were examined at 7 and 14 days post-transplantation. As a result, infiltration of activated mast cells remained in deeper area of peritoneal tissue around the endometriosis model compared to the control group at 14 days post-autotransplantation. In the DE exposure group, 14 days post-transplant, the remaining lesions contained fibroblasts and activated mast cells, which were surrounded by collagen fibers. The data showed that prenatal and postnatal DE exposure enhances the activation of mast cells and prolongs the persistence of collagen fibers in the induced rat model of endometriosis.

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

AIMS

To characterize the biochemical alterations that occur in the peritoneal tissue of the mouse endometriosis model during early development of the lesion using microarray analysis.

MAIN METHODS

The endometriosis model was induced by autotransplantation of endometrium in 8-week-old female ICR mice. Peritoneum only (excluding the transplant) was obtained 24, 48, and 96 h after the autotransplantation and subjected to microarray analysis. To interpret the large amounts of data generated and to enable a functional analysis, genes were classified using Gene Ontology (GO) and Medical Subject Heading (MeSH) terms, and the results were compared with previous reports on endometriosis.

KEY FINDINGS

Of the upregulated genes, those involved in the inflammatory response, cell adhesion, extracellular matrix, wound healing, hormones, and leukocytes were significantly enriched 24 and 48 h after autotransplantation. Those of cytokines, antibody-producing cells, dendritic cells, inflammation, and infertility were enriched after 96 h. Analysis using GO and MeSH provided different information. Particularly, MeSH showed a link between an anatomical and diseased phenotype with common genes found to be upregulated.

SIGNIFICANCE

The factors occurring during early development of endometriosis induced by endometrium autotransplantation are increase in adhesion molecules and inflammatory responses rather than angiogenesis. Data presented herein may reveal a novel therapeutic gene targets and will contribute to knowledge for the treatment of this currently incurable disease.

Change of proinflammatory cytokines follows certain patterns after induction of endometriosis in a mouse model

OBJECTIVE

To examine the change in proinflammatory cytokines in the pathologic processes of endometriosis in mice.

DESIGN

A dynamic study on a murine model of endometriosis.

SETTING

Medical school.

ANIMAL(S)

Female BALB/c mice.

INTERVENTION(S)

Endometriosis was induced by injecting endometrial fragments of syngenic mice into the peritoneal cavity of model mice; in control group, phosphate-buffered saline instead of fragments was injected. The peritoneal fluid and the endometriotic lesions were harvested 1 to 21 days after the induction.

MAIN OUTCOME MEASURE(S)

The endometriotic lesions were weighed, the gene and protein levels of some proinflammatory cytokines, including interleukin 1beta, tumor necrosis factor alpha, vascular endothelial growth factor, and monocyte chemoattractant protein 1, were determined by real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively.

RESULT(S)

The levels of these cytokines reached the first peak on the first day and no endometriotic lesions were found. The lesions began to appear on the second day, presenting red color during the initial 6 days, and then they turned dark-red, brown, or bluish. The adhesion took place on the 9th day, and all the lesions evolved into white or transparent cysts on the 15th day. Corresponding to these changes, the second and the third peaks were identified during the 3rd-6th day and the 12th-15th day, respectively.

CONCLUSION(S)

The change pattern of cytokines over time might bear some relationship with the development and progression of the endometriosis.