Nerve fibres in peritoneal endometriosis

Endometriosis, Pain, and Related Psychological Disorders: Unveiling the Interplay among the Microbiome, Inflammation, and Oxidative Stress as a Common Thread

Endometriosis (EM), a chronic condition in endometrial tissue outside the uterus, affects around 10% of reproductive-age women, significantly affecting fertility. Its prevalence remains elusive due to the surgical confirmation needed for diagnosis. Manifesting with a range of symptoms, including dysmenorrhea, dyschezia, dysuria, dyspareunia, fatigue, and gastrointestinal discomfort, EM significantly impairs quality of life due to severe chronic pelvic pain (CPP). Psychological manifestations, notably depression and anxiety, frequently accompany the physical symptoms, with CPP serving as a key mediator. Pain stems from endometrial lesions, involving oxidative stress, neuroinflammation, angiogenesis, and sensitization processes. Microbial dysbiosis appears to be crucial in the inflammatory mechanisms underlying EM and associated CPP, as well as psychological symptoms. In this scenario, dietary interventions and nutritional supplements could help manage EM symptoms by targeting inflammation, oxidative stress, and the microbiome. Our manuscript starts by delving into the complex relationship between EM pain and psychological comorbidities. It subsequently addresses the emerging roles of the microbiome, inflammation, and oxidative stress as common links among these abovementioned conditions. Furthermore, the review explores how dietary and nutritional interventions may influence the composition and function of the microbiome, reduce inflammation and oxidative stress, alleviate pain, and potentially affect EM-associated psychological disorders.

Effects of osteopathic manipulative therapy on recurrent pelvic pain and dyspareunia in women after surgery for endometriosis: a retrospective study

BACKGROUND

Surgical removal of deep infiltrating endometriosis is frequently associated with improvement in symptoms. However, because of the complex pathogenesis of pain in endometriosis that includes central sensitization and myofascial dysfunction, symptoms can persist after surgery. The aim of the present observational study is to explore the effectiveness of osteopathic manipulative treatment (OMT) in reducing persistent pelvic pain and dyspareunia in a sample of symptomatic women surgically treated for endometriosis.

METHODS

Retrospective cohort analysis of 69 patients treated with OMT, for persistent myofascial pain, chronic pelvic pain (CPP) and dyspareunia after surgical eradication of endometriosis. Surgical, clinical and osteopathic reports were retrospectively analyzed in a chart review. Osteopathic interventions included myofascial release, balanced ligamentous/membranous tension and indirect fluidic technique.

RESULTS

During the study period 345 patients underwent surgery for symptomatic endometriosis. Among them, 97 patients (28.1%) complained of post-operative persistent CPP and dyspareunia and 69 patients underwent osteopathic treatment. OMT reports showed a significant improvement of the symptoms after the first OMT session. Particularly, lower scores of CPP (mean NRS 4±4.2 vs. 0.2±0.7, P value.

CONCLUSIONS

OMT, breaking the cycle of pain and normalizing the musculoskeletal pelvic activity, could be a successful technique to treat persistent chronic pain in women surgically treated for endometriosis.

Transcriptomic changes in eutopic endometrium and ectopic lesions during endometriosis progression in a mouse model

OBJECTIVE

To identify the transcriptomic changes of ectopic lesions and eutopic endometrial tissues during the progression of endometriosis, we performed transcriptomic analysis in the eutopic endometrium and ectopic lesions.

DESIGN

Laboratory study.

SETTING

Academic medical center.

ANIMALS

Four fertile and 4 subfertile Pgrcre/+Rosa26mTmG/+ mice with endometriosis, and 4 sham mice for each group of endometriosis mice as control. These mice underwent either surgery to induce endometriosis or sham surgery. Fertile sham and mice with endometriosis were used 1 month after surgery, whereas subfertile ones were used 3 months after surgery.

INTERVENTIONS

Early and chronic effects of endometriosis on transcriptomics of ectopic lesions and eutopic endometrium.

MAIN OUTCOME MEASURES

RNA-sequencing analysis and identification of differentially expressed genes and pathways in the ectopic lesions and eutopic uteri from mice with endometriosis and sham mice at day 3.5 of pregnancy.

RESULTS

Our mouse model recapitulates the transcriptomic changes of ectopic lesions in humans. RNA-sequencing analysis was performed in ectopic lesions and eutopic uteri from mice with or without endometriosis during the progression of the disease. Estrogen activity, inflammation, angiogenesis, and fibrosis pathways were consistently elevated in all the ectopic lesions compared with eutopic endometrium. Cholesterol/glucose synthesis and stem cell pluripotency pathways were more enhanced in ectopic lesions from subfertile mice compared with their eutopic endometrium. Dysregulation of infiltration of macrophage, dendritic, T and B cells was validated with the use of immunohistochemistry in ectopic lesions. Multiple ligand-receptor pairs between the ectopic and eutopic endometrium were altered compared with the sham endometrium. Suppressed WNT and EGF pathways were only found in the eutopic endometrium from subfertile not fertile mice compared with sham.

CONCLUSIONS

Our mouse endometriosis model recapitulates the transcriptomics of ectopic lesions in humans. Our transcriptomic analysis during endometriosis progression in our mouse model will help us understand the pathophysiology of endometriosis.

MRI Features of Pelvic Nerve Involvement in Endometriosis

Endometriosis is a common condition that mostly affects people assigned as female at birth. The most common clinical symptom of endometriosis is pain. Although the mechanism for this pain is poorly understood, in some cases, the nerves are directly involved in endometriosis. Endometriosis is a multifocal disease, and the pelvis is the most common location involved. Nerves in the pelvis can become entrapped and involved in endometriosis. Pelvic nerves are visible at pelvic MRI, especially when imaging planes and sequences are tailored for neural evaluation. In particular, high-spatial-resolution anatomic imaging including three-dimensional isotropic imaging and contrast-enhanced three-dimensional short inversion time inversion-recovery (STIR) fast spin-echo sequences are useful for nerve imaging. The most commonly involved nerves are the sciatic, obturator, femoral, pudendal, and inferior hypogastric nerves and the inferior hypogastric and lumbosacral plexuses. Although it is thought to be rare, the true incidence of nerve involvement in endometriosis is not known. Symptoms of neural involvement include pain, weakness, numbness, incontinence, and paraplegia and may be constant or cyclic (catamenial). Early diagnosis of neural involvement in endometriosis is important to prevent irreversible nerve damage and chronic sensorimotor neuropathy. Evidence of irreversible damage can also be seen at MRI, and radiologists should evaluate pelvic nerves that are commonly involved in endometriosis in their search pattern and report template to ensure that this information is incorporated into treatment planning.

IL-8 and IL-12p70 are associated with pelvic pain among infertile women with endometriosis

OBJECTIVE

To evaluate interleukin (IL)-1β, IL-6, IL-8, and IL-12p70 levels in serum and peritoneal fluid in women related to infertility and pelvic pain.

METHODS

Eighty-seven women were diagnosed with endometriosis or cases related to infertility. IL-1β, IL-6, IL-8, and IL-12p70 levels in serum and peritoneal fluid were determined by enzyme-linked immunosorbent assay (ELISA). Pain assessment was evaluated by the Visual Analog Scale (VAS) score.

RESULTS

Serum IL-6 and IL-12p70 levels increased in women with endometriosis compared to the control group. Serum and peritoneal IL-8 and IL-12p70 levels correlated with VAS scores in infertile women. A positive correlation was also found between peritoneal IL-1β and IL-6 with VAS score. A significant difference in peritoneal IL-1β levels was associated with menstrual pelvic pain, while peritoneal IL-8 levels were related to dyspareunia, menstrual, and post-menstrual pelvic pain in infertile women.

CONCLUSIONS

An association of IL-8 and IL-12p70 levels were related to pain in endometriosis, as well as a relationship between cytokine expression and VAS score. Further studies should be addressed to investigate the precise mechanism of cytokine-related pain in endometriosis.

Mechanisms of peripheral sensitization in endometriosis patients with peritoneal lesions and acyclical pain

PURPOSE

Endometriosis (EM) is one of the most frequent differential diagnoses concerning chronic pelvic pain. Women under hormonal therapy (HT) often benefit from it but sometimes suffer a setback and develop acyclical pelvic pain. Due to the assumption that mechanisms of neurogenic inflammation are involved in the generation of chronic pelvic pain, we aimed to investigate the expression of sensory nerve markers in EM-associated nerve fibers of patients with/without HT.

METHODS

Laparoscopically excised peritoneal samples from 45 EM and 10 control women were immunohistochemically stained for: PGP9.5, Substance P (SP), NK1R, NGFp75, TRPV-1, and TrkA. Demographics and severity of pain were documented.

RESULTS

EM patients showed a higher nerve fiber density (PGP9.5 and SP) and increased expression of NGFp75, TRPV1, TrkA, and NK1R in blood vessels and immune cells compared with controls. Patients with HT have cycle-dependent pelvic pain but suffer from acyclical pelvic pain. Interestingly, reducing NK1R expression in blood vessels under HT was observed. A correlation between dyspareunia severity and nerve fibers density and between NGFRp75 expression in blood vessels and cycle-dependent pelvic pain severity was observed.

CONCLUSION

Patients under HT have no ovulation and no (menstrual) bleeding, which correlate with inflammation and cyclical pain. However, acyclical pain seems to be due to peripheral sensitization once it is present under treatment. Neurotransmitters, like SP and their receptors, are involved in mechanisms of neurogenic inflammation, which are relevant for pain initiation. These findings indicate that in both groups (EM with/without HT), neurogenic inflammation is present and responsible for acyclical pain.

Understanding endometriosis from an immunomicroenvironmental perspective

ABSTRACT

Endometriosis, a heterogeneous, inflammatory, and estrogen-dependent gynecological disease defined by the presence and growth of endometrial tissues outside the lining of the uterus, affects approximately 5-10% of reproductive-age women, causing chronic pelvic pain and reduced fertility. Although the etiology of endometriosis is still elusive, emerging evidence supports the idea that immune dysregulation can promote the survival and growth of retrograde endometrial debris. Peritoneal macrophages and natural killer (NK) cells exhibit deficient cytotoxicity in the endometriotic microenvironment, leading to inefficient eradication of refluxed endometrial fragments. In addition, the imbalance of T-cell subtypes results in aberrant cytokine production and chronic inflammation, which contribute to endometriosis development. Although it remains uncertain whether immune dysregulation represents an initial cause or merely a secondary enhancer of endometriosis, therapies targeting altered immune pathways exhibit satisfactory effects in preventing disease onset and progression. Here, we summarize the phenotypic and functional alterations of immune cells in the endometriotic microenvironment, focusing on their interactions with microbiota and endocrine and nervous systems, and how these interactions contribute to the etiology and symptomology of endometriosis.

Neurotrophins and Their Receptors, Novel Therapeutic Targets for Pelvic Pain in Endometriosis, Are Coordinately Regulated by IL-1β via the JNK Signaling Pathway

Pelvic pain in women with endometriosis is attributed to neuroinflammation and afferent nociceptor nerves in ectopic and eutopic endometrium. The hypothesis that uterine nociception is activated by IL-1β, a prominent cytokine in endometriosis, was tested herein. Immunofluorescence histochemistry confirmed the presence of neurons in human endometrial tissue. Expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) and their receptors in endometrial tissue and cells was validated by immunohistochemistry and Western blotting. Isolated endometrial stromal cells (ESCs) were subjected to dose-response and time-course experiments with IL-1β and kinase inhibitors to characterize in vitro biomarkers. Neural biomarkers were co-localized in endometrial nerve fibers. NGF, BDNF, and their receptors tropomyosin receptor kinase (Trk) A, TrkB, and p75 neurotrophin receptor were all expressed in primary ESCs. IL-1β stimulated higher TrkA/B expression in ESCs derived from endometriosis cases (2.8- ± 0.2-fold) than cells from controls (1.5- ± 0.3-fold, t-test, P < 0.01), effects that were mediated via the c-Jun N-terminal kinase (JNK) pathway. BDNF concentrations trended higher in peritoneal fluid of endometriosis cases but were not statistically different from controls (P = 0.16). The results support the hypothesis that NGF and BDNF and their corresponding receptors orchestrate innervation of the endometrium, which is augmented by IL-1β. We postulate that JNK inhibitors, such as SP600125, have the potential to reduce neuroinflammation in women with endometriosis.

Non-response to first-line hormonal treatment for symptomatic endometriosis: overcoming tunnel vision. A narrative review

One-fourth to one-third of women with endometriosis receiving first-line hormonal treatment lacks an adequate response in terms of resolution of painful symptoms. This phenomenon has been ascribed to "progesterone resistance", an entity that was theorized to explain the gap between the ubiquity of retrograde menstruation and the 10% prevalence of endometriosis among women of reproductive age.Nevertheless, the hypothesis of progesterone resistance is not free of controversies. As our understanding of endometriosis is increasing, authors are starting to set aside the traditionally accepted tunnel vision of endometriosis as a strictly pelvic disease, opening to a more comprehensive perspective of the condition. The question is: are patients not responding to first-line treatment because they have an altered signaling pathway for such treatment, or have we been overlooking a series of other pain contributors which may not be resolved by hormonal therapy?Finding an answer to this question is evermore impelling, for two reasons mainly. Firstly, because not recognizing the presence of further pain contributors adds a delay in treatment to the already existing delay in diagnosis of endometriosis. This may lead to chronicity of the untreated pain contributors as well as causing adverse consequences on quality of life and psychological health. Secondly, misinterpreting the consequences of untreated pain contributors as a non-response to standard first-line treatment may imply the adoption of second-line medical therapies or of surgery, which may entail non-negligible side effects and may not be free of physical, psychological and socioeconomic repercussions.The current narrative review aims at providing an overview of all the possible pain contributors in endometriosis, ranging from those strictly organic to those with a greater neuro-psychological component. Including these aspects in a broader psychobiological approach may provide useful suggestions for treating those patients who report persistent pain symptoms despite receiving first-line hormonal medical treatment.

The role of CXCL1/CXCR2 axis in neurological diseases

The C-X-C chemokine ligand (CXCL) 1 and its receptor C-X-C chemokine receptor (CXCR) 2 are widely expressed in the peripheral nervous systems (PNS) and central nervous systems (CNS) and are involved in the development of inflammation and pain after various nerve injuries. Once a nerve is damaged, it affects not only the neuron itself but also lesions elsewhere in its dominant site. After the CXCL1/CXCR2 axis is activated, multiple downstream pathways can be activated, such as c-Raf/MAPK/AP-1, p-PKC-μ/p-ILK/NLRP3, JAK2/STAT3, TAK1/NF-κB, etc. These pathways in turn mediate cellular motility state or cell migration. CXCR2 is expressed on the surface of neutrophils and monocytes/macrophages. These cells can be recruited to the lesion through the CXCL1/CXCR2 axis to participate in the inflammatory response. The expression of CXCR2 in neurons can activate some pathways in neurons through the CXCL1/CXCR2 axis, thereby causing damage to neurons. CXCR2 is also expressed in astrocytes, and when CXCR2 activated, it increases the number of astrocytes but impairs their function. Since inflammation can occur at almost any site of injury, elucidating the mechanism of CXCL1/CXCR2 axis' influence on inflammation may provide a favorable target for clinical treatment. Therefore, this article reviews the research progress of the CXCL1/CXCR2 axis in neurological diseases, aiming to provide a more meaningful theoretical basis for the treatment of neurological diseases.

Prolactin and pain of endometriosis

Women experience chronic pain more often than men with some pain conditions being specific to women while others are more prevalent in women. Prolactin, a neuropeptide hormone with higher serum levels in women, has recently been demonstrated in preclinical studies to sensitize nociceptive sensory neurons in a sexually dimorphic manner. Dysregulation of prolactin and prolactin receptors may be responsible for increased pain especially in female predominant conditions such as migraine, fibromyalgia, and pelvic pain. In this review, we focus on the role of prolactin in endometriosis, a condition characterized by pelvic pain and infertility that affects a large proportion of women during their reproductive age. We discuss the symptoms and pathology of endometriosis and discuss how different sources of prolactin secretion may contribute to this disease. We highlight our current understanding of prolactin-mediated mechanisms of nociceptor sensitization in females and how this mechanism may apply to endometriosis. Lastly, we report the results of a systematic review of clinical studies conducted by searching the PubMed and EMBASE databases to identify association between endometriosis and blood levels of prolactin. The results of this search strongly indicate that serum prolactin levels are increased in patients with endometriosis and support the possibility that high levels of prolactin may promote pelvic pain in these patients and increase vulnerability to other comorbid pain conditions likely by dysregulating prolactin receptor expression. Targeting of prolactin and prolactin receptors may improve management of pain associated with endometriosis.

A Lifelong Impact on Endometriosis: Pathophysiology and Pharmacological Treatment

Endometriosis is a chronic inflammatory disease associated with bothersome symptoms in premenopausal women and is complicated with long-term systemic impacts in the post-menopausal stage. It is generally defined by the presence of endometrial-like tissue outside the uterine cavity, which causes menstrual disorders, chronic pelvic pain, and infertility. Endometriotic lesions can also spread and grow in extra-pelvic sites; the chronic inflammatory status can cause systemic effects, including metabolic disorder, immune dysregulation, and cardiovascular diseases. The uncertain etiologies of endometriosis and their diverse presentations limit the treatment efficacy. High recurrence risk and intolerable side effects result in poor compliance. Current studies for endometriosis have paid attention to the advances in hormonal, neurological, and immunological approaches to the pathophysiology and their potential pharmacological intervention. Here we provide an overview of the lifelong impacts of endometriosis and summarize the updated consensus on therapeutic strategies.

Neuroepithelial Interactions in Cancer

Nerves not only regulate the homeostasis and energetic metabolism of normal epithelial cells but also are critical for cancer, as cancer recapitulates the biology of neural regulation of epithelial tissues. Cancer cells rarely develop in denervated organs, and denervation affects tumorigenesis, in vivo and in humans. Axonogenesis occurs to supply the new malignant epithelial growth with nerves. Neurogenesis happens later, first in ganglia around organs or the spinal column and subsequently through recruitment of neuroblasts from the central nervous system. The hallmark of this stage is regulation of homeostasis and energetic metabolism. Perineural invasion is the most efficient interaction between cancer cells and nerves. The hallmark of this stage is increased proliferation and decreased apoptosis. Finally, carcinoma cells transdifferentiate into a neuronal profile in search of neural independence. The latter is the last stage in neuroepithelial interactions. Treatments for cancer must address the biology of neural regulation of cancer.

Potential link between the nerve injury-induced protein (Ninjurin) and the pathogenesis of endometriosis

Endometriosis remains a widespread but severe gynecological disease in women of reproductive age, with an unknown etiology and few treatment choices. The menstrual reflux theory is largely accepted as the underlying etiology but does not explain the morbidity or unpleasant pain sensations of endometriosis. The neurological and immune systems are both involved in pain mechanisms of endometriosis, and interlinked through a complex combination of cytokines and neurotransmitters. Numerous pieces of evidence suggest that the nerve injury-inducible protein, Ninjurin, is actively expressed in endometriosis lesions, which contributes to the etiology and development of endometriosis. It may be explored in the future as a novel therapeutic target. The aim of the present review was to elucidate the multifaceted role of Ninjurin. Furthermore, we summarize the association of Ninjurin with the pain mechanism of endometriosis and outline the future research directions. A novel therapeutic pathway can be discovered based on the potential pathogenic variables.

Emotional dysregulation in women with endometriosis with cyclical and non-cyclical chronic pelvic pain

BACKGROUND

Endometriosis is a pathophysiological condition characterized by glands and stroma outside the uterus in regions such as the bladder, ureter, fallopian tubes, peritoneum, ovaries, and even in extra pelvic sites. One of the main clinical problems of endometriosis is chronic pelvic pain (CPP), which considerably affects the patients' quality of life. Patients with endometriosis may, cyclically or non-cyclically (80% of cases) experience CPP. High levels of anxiety and depression have been described in patients with endometriosis related to CPP; however, this has not been evaluated in endometriosis women with different types of CPP. Therefore, the research question of this study was whether there is a difference in the emotional dysregulation due to the type of pain experienced by women with endometriosis?

METHODS

This work was performed in the National Institute of Perinatology (INPer) in Mexico City from January 2019 to March 2020 and aimed to determine if there are differences in emotional dysregulation in patients with cyclical and non-cyclical CPP. 49 women from 18 to 52 years-old diagnosed with endometriosis presenting cyclical and non-cyclical CPP answered several batteries made up of Mini-Mental State Examination, Visual Analog Scale, Beck's Depression Inventory, State Trait-Anxiety Inventory, and Generalized Anxiety Inventory. Mann-Whitney U and Student's t-test for independent samples to compare the difference between groups was used. Relative risk estimation was performed to determine the association between non-cyclical and cyclical CPP with probability of presenting emotional dysregulation.

RESULTS

We observed that patients with non-cyclical CPP exhibited higher levels of depression and anxiety (trait-state and generalized anxiety) than patients with cyclical pain, p < 0.05 was considered significant. No differences were observed in pain intensity, but there was a higher probability of developing emotional dysregulation (anxiety or depression) in patients with non-cyclical CPP. No differences were observed in cognitive impairment.

CONCLUSIONS

Our data suggest that patients with non-cyclical (persistent) CPP present a higher emotional dysregulation than those with cyclical pain.

Involvement of the calcitonin gene-related peptide system in the modulation of inflamed uterus contractile function in pigs

This study analyzed severe acute endometritis action on myometrial density and distribution of protein gene product (PGP)9.5- and calcitonin gene-related peptide (CGRP)-like immunoreactive nerve fibers and calcitonin receptor-like receptor (CLR) expression, and on CGRP receptor (CGRPR) participation in uterine contractility in pigs. E. coli suspension (E. coli group) or saline (SAL group) were injected into the uteri, or only laparotomy was performed (CON group). In the E. coli group myometrium, a lack of significant changes in PGP9.5 and CGRP innervation patterns and increased CLR protein level were revealed. In all groups, compared to the pretreatment period, human αCGRP increased amplitude in the myometrium, while reducing it in endometrium/myometrium. In the E. coli group endometrium/myometrium, human αCGRP lowered amplitude vs other groups. Human αCGRP reduced frequency in CON and SAL groups and enhanced it in the E. coli group endometrium/myometrium. The frequency in E. coli group increased vs other groups. CGRPR antagonist, human αCGRP8-37, reversed (CON, SAL groups) and eliminated (E. coli group) the rise in human αCGRP-induced myometrial amplitude. In endometrium/myometrium, human αCGRP8-37 abolished (CON group) and reversed (SAL group) a decrease in frequency, and reduced the rise in frequency (E. coli group) caused by human αCGRP. Collectively, in the myometrium, endometritis did not change PGP9.5 and CGRP innervation patterns and enhanced CLR protein level. CGRPR also mediated in CGRP action on inflamed uterus contractility.

The association of endosalpingiosis with gynecologic malignancy

OBJECTIVE

Endosalpingiosis is a poorly understood condition of ectopic epithelium resembling the fallopian tubes. It has been described as an incidental pathology finding, a disease similar to endometriosis, and in association with malignancy. The objective of this study is to determine if endosalpingiosis (ES) has an increased association with gynecologic malignancy when compared to endometriosis (EM).

METHODS

This is a retrospective case-control analysis of patients with a histologic diagnosis of endosalpingiosis or endometriosis at three affiliated academic hospitals between 2000 and 2020. All ES patients were included, and 1:1 matching was attempted to obtain a comparable cohort of EM patients. Demographic and clinical data were obtained, and statistical analysis was performed.

RESULTS

A total of 967 patients (515 ES and 452 EM) were included. ES patients were significantly older than EM patients (median age 52 vs 48 years, p < 0.001). The ES group had significantly more cancer diagnoses at surgery than the EM group (40.1% vs 18.1%, p < 0.001); this difference persisted in a sub-analysis excluding patients with known or suspected malignancy (20.9% vs 5.6%, p < 0.001). ES patients had lower overall survival (10-year freedom from death: 77.0% vs 90.5%, p < 0.001). After adjusting for confounders, multivariable analysis showed that ES patients had increased cancer diagnosed at surgery (OR = 2.48, p < 0.001) and greater risk of death (OR = 1.69, p = 0.017).

CONCLUSIONS

Endosalpingiosis was found concurrently with malignancy in 40% of cases, and this effect was preserved in multi-variable and sub-group analyses. Further research consisting of longer follow-up and exploration of molecular relationships between ES and cancer are forthcoming.

Hormonal treatments for endometriosis: The endocrine background

Endometriosis is a benign uterine disorder characterized by menstrual pain and infertility, deeply affecting women's health. It is a chronic disease and requires a long term management. Hormonal drugs are currently the most used for the medical treatment and are based on the endocrine pathogenetic aspects. Estrogen-dependency and progesterone-resistance are the key events which cause the ectopic implantation of endometrial cells, decreasing apoptosis and increasing oxidative stress, inflammation and neuroangiogenesis. Endometriotic cells express AMH, TGF-related growth factors (inhibin, activin, follistatin) CRH and stress related peptides. Endocrine and inflammatory changes explain pain and infertility, and the systemic comorbidities described in these patients, such as autoimmune (thyroiditis, arthritis, allergies), inflammatory (gastrointestinal/urinary diseases) and mental health disorders.The hormonal treatment of endometriosis aims to block of menstruation through an inhibition of hypothalamus-pituitary-ovary axis or by causing a pseudodecidualization with consequent amenorrhea, impairing the progression of endometriotic implants. GnRH agonists and antagonists are effective on endometriosis by acting on pituitary-ovarian function. Progestins are mostly used for long term treatments (dienogest, NETA, MPA) and act on multiple sites of action. Combined oral contraceptives are also used for reducing endometriosis symptoms by inhibiting ovarian function. Clinical trials are currently going on selective progesterone receptor modulators, selective estrogen receptor modulators and aromatase inhibitors. Nowadays, all these hormonal drugs are considered the first-line treatment for women with endometriosis to improve their symptoms, to postpone surgery or to prevent post-surgical disease recurrence. This review aims to provide a comprehensive state-of-the-art on the current and future hormonal treatments for endometriosis, exploring the endocrine background of the disease.

Anatomic and functional mapping of human uterine innervation

OBJECTIVE

To better understand the physiology of pain in pelvic pain pathological conditions, such as endometriosis, in which alterations of uterine innervation have been highlighted, we performed an anatomic and functional mapping of the macro- and microinnervation of the human uterus. Our aim was to provide a 3-dimensional reconstruction model of uterine innervation.

DESIGN

This was an experimental study. We dissected the pelvises of 4 human female fetuses into serial sections, and treated them with hematoxylin and eosin staining before immunostaining.

SETTING

Academic Research Unit.

PATIENTS

None.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Detection of nerves (S100 +) and characterization of the types of nerves. The slices obtained were aligned to construct a 3-dimensional model.

RESULTS

A 3-dimensional model of uterine innervation was constructed. The nerve fibers appeared to have a centripetal path from the uterine serosa to the endometrium. Within the myometrium, innervation was dense. Endometrial innervation was sparse but present in the functional layer of the endometrium. Overall innervation was richest in the supravaginal cervix and rarer in the body of the uterus. Innervation was rich particularly laterally to the cervix next to the parametrium and paracervix. Four types of nerve fibers were identified: autonomic sympathetic (TH+), parasympathetic (VIP+), and sensitive (NPY+, CGRP1+ and VIP+). They were found in the 3 portions and the 3 layers of the uterus.

CONCLUSIONS

We constructed a 3-dimensional model of the human uterine innervation. This model could provide a solid base for studying uterine innervation in pathologic situations, in order to find new therapeutic approaches.

Possible therapeutic effect of royal jelly on endometriotic lesion size, pain sensitivity, and neurotrophic factors in a rat model of endometriosis

Endometriosis is the abnormal growth of endometrial tissue. The goals of the study are: (1) Is any correlation between endometriosis pain and neurotrophins in the serum, dorsal root ganglion (DRG), and peritoneal fluid (PF) in rat models of experimental endometriosis?, (2) Possible therapeutic effects of royal jelly (RJ) on pain scores, size of endometriotic lesion, and neurotrophic factors. Forty-eight Sprague Dawley female rats weighing 205.023 ± 21.54 g were maintained in a standard condition. The rats were randomly divided into one of the six groups: Control (no intervention), Sham-1 (remove of uterine horn), RJ (administration of 200 mg/kg/day RJ for 21 days), Endometriosis (induction of endometriosis), Treatment (induction of endometriosis+administration of 200 mg/kg/day RJ for 21 days), and Sham-2 (induction of endometriosis+administration of water). Formalin test performed for pain evaluation. The levels of Brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), substance P, and calcitonin gene-related peptide (CGRP) were measured by enzyme-linked immunosorbent assay. The mean pain scores in all three phases of the formalin test were significantly increased by endometriosis induction (p < 0.05). The concentrations of BDNF, NGF, and CGRP in DRG of the endometriosis group were significantly higher than these factors in the Control, Sham-1, and RJ groups (p < 0.05). RJ could significantly (p < 0.001) decrease the mean lesion size and the mean pain score in the late phase (p < 0.05). The present results determine that endometriosis pain may be related to nervous system neurotrophic factors. Treatment with RJ could decrease the size of endometriosis lesions as well as pain scores. The findings may shed light on other complementary and alternative remedies for endometriosis.

Assessment of Nerve Fiber Density and Expression of Hormonal Receptors Within Rectosigmoid Endometriosis Nodules

STUDY OBJECTIVE

To assess nerve fiber density and expression of hormone receptors in bowel endometriosis.

DESIGN

Cross-sectional study.

SETTING

Private hospital.

PATIENTS

Women with endometriosis undergoing laparoscopic segmental bowel resection (n = 54).

INTERVENTIONS

Tissue samples were obtained from patients with surgically treated rectosigmoid endometriosis.

MEASUREMENTS AND MAIN RESULTS

The rectosigmoid specimen containing the endometriosis nodule was manually sectioned and divided into 3 areas: core of the nodule, margin of the nodule, and healthy bowel tissue. The intensity of expression of estrogen and progesterone receptors was evaluated by immunohistochemistry and measured according to the Allred score. Nerve fibers were stained by immunohistochemistry using Protein Gene Product 9.5, and the density of nerve fillets was counted and expressed in number/mm². All glandular and stromal cells stained for estrogen; however, glandular cells stained more strongly than stromal cells (61.1% vs 35.2%; p = .01). Most of glandular and stromal cells stained strongly for progesterone receptors (90.7% vs 98.1%; p = .2). The density of nerve fibers was very high in the margin of the nodule (172.22±45.66/mm²), moderate in healthy bowel tissue (111.48±48.57/mm²), and very low in the core of the nodule (7.31±4.9/mm²); p = .01.

CONCLUSION

Both glandular and stromal cells within the rectosigmoid endometriosis nodule express estrogen and progesterone receptors. Higher intensity of expression of estrogen receptors occurs in glandular cells. The density of nerve fibers is extremely high at the nodule margin and very low in the center of the nodule.

A mouse model of endometriosis that displays vaginal, colon, cutaneous, and bladder sensory comorbidities

Endometriosis is a painful inflammatory disorder affecting ~10% of women of reproductive age. Although chronic pelvic pain (CPP) remains the main symptom of endometriosis patients, adequate treatments for CPP are lacking. Animal models that recapitulate the features and symptoms experienced by women with endometriosis are essential for investigating the etiology of endometriosis, as well as developing new treatments. In this study, we used an autologous mouse model of endometriosis to examine a combination of disease features and symptoms including: a 10 week time course of endometriotic lesion development; the chronic inflammatory environment and development of neuroangiogenesis within lesions; sensory hypersensitivity and altered pain responses to vaginal, colon, bladder, and skin stimulation in conscious animals; and spontaneous animal behavior. We found significant increases in lesion size from week 6 posttransplant. Lesions displayed endometrial glands, stroma, and underwent neuroangiogenesis. Additionally, peritoneal fluid of mice with endometriosis contained known inflammatory mediators and angiogenic factors. Compared to Sham, mice with endometriosis displayed: enhanced sensitivity to pain evoked by (i) vaginal and (ii) colorectal distension, (iii) altered bladder function and increased sensitivity to cutaneous (iv) thermal and (v) mechanical stimuli. The development of endometriosis had no effect on spontaneous behavior. This study describes a comprehensive characterization of a mouse model of endometriosis, recapitulating the clinical features and symptoms experienced by women with endometriosis. Moreover, it delivers the groundwork to investigate the etiology of endometriosis and provides a platform for the development of therapeutical interventions to manage endometriosis-associated CPP.

A deep insight into pelvic pain and endometriosis: a review of the literature from pathophysiology to clinical expressions

Endometriosis is a chronic inflammatory disease that affects approximately 10% of women of reproductive age. Its clinical manifestations are highly heterogeneous, but pelvic pain is the most frequent, causing functional disability. Cyclic or acyclic chronic pelvic pain (CPP), dysmenorrhea and dyspareunia are frequent symptoms which often compromise all aspects of the women's quality of life (QoL). The pathophysiology of endometriosis-related pain is extremely complex and not always clear. The aim of this literature review is to focus on recent updates on the clinical presentation, the pathophysiology and the most important mechanisms involved in the pathogenesis of pelvic pain in endometriosis. A literature search in the Cochrane library, PubMed, Scopus and web of Science databases has been performed, identifying articles from January 1995 to November 2020. Several processes seem to be involved in the pathogenesis of pain, but many aspects are still unclear. Scientific evidence has shown that a correlation between pain severity and stage of endometriosis rarely occurs, whereas there is a significant correlation between pain and the presence of deep endometriosis. Onset and intensity of pain may be due to a complex process involving central sensitization and peripheral activation of nociceptive pathways as well as dysfunction of the immune system and of the hypothalamic-pituitary-adrenal (HPA) axis. A deeper understanding of these different pathogenetic mechanisms may improve future treatments in women with painful endometriosis.

Possible involvement of neuropeptide and neurotransmitter receptors in Adenomyosis

BACKGROUND

Accumulating data indicate that sensory nerve derived neuropeptides such as substance P and calcitonin gene related-protein (CGRP) can accelerate the progression of endometriosis via their respective receptors, so can agonists to their respective receptors receptor 1 (NK1R), receptor activity modifying protein 1 (RAMP-1) and calcitonin receptor-like receptor (CRLR). Adrenergic β2 receptor (ADRB2) agonists also can facilitate lesional progression. In contrast, women with endometriosis appear to have depressed vagal activity, concordant with reduced expression of α7 nicotinic acetylcholine receptor (α7nAChR). The roles of these receptors in adenomyosis are completely unknown.

METHODS

Adenomyotic tissue samples from 30 women with adenomyosis and control endometrial tissue samples from 24 women without adenomyosis were collected and subjected to immunohistochemistry analysis of RAMP1, CRLR, NK1R, ADRB2 and α7nAChR, along with their demographic and clinical information. The extent of tissue fibrosis was evaluated by Masson trichrome staining.

RESULTS

We found that the staining levels of NK1R, CRLR, RAMP1 and ADRB2 were all significantly elevated in adenomyotic lesions as compared with control endometrium. In contrast, α7nAChR staining levels were significantly reduced. The severity of dysmenorrhea correlated positively with lesional ADRB2 staining levels.

CONCLUSIONS

Our results suggest that SP, CGRP and noradrenaline may promote, while acetylcholine may stall, the progression of adenomyosis through their respective receptors on adenomyotic lesions. Additionally, through the activation of the hypothalamic-pituitary-adrenal (HPA)-sympatho-adrenal-medullary (SAM) axes and the lesional overexpression of ADRB2, adenomyosis-associated dysmenorrhea and adenomyotic lesions may be mutually promotional, forming a viscous feed-forward cycle.

Assessing Pain Behavioral Responses and Neurotrophic Factors in the Dorsal Root Ganglion, Serum and Peritoneal Fluid in Rat Models of Endometriosis

Objective: Pain is the most frequently reported symptom involving in endometriosis. The alterations of neurotrophic factors and certain neuropeptides in the dorsal root ganglion (DRG), as well as serum and peritoneal fluid (PF), were evaluated in rat models of endometriosis.

Materials and methods: Twenty-four Sprague Dawley female rats were selected and maintained in a standard condition with 12 hours’ dark-light cycles. All the rats were randomly assigned to 3 groups: Control (intact rats); Sham (the operation was conducted without endometriosis induction); and Endometriosis (endometriosis induction was performed). The formalin test was performed for all groups on the first and the 21^st day of the study. The assessments of Brain-Derived Neurotrophic Factor (BDNF), Nerve Growth Factor (NGF), Calcitonin Gene-Related Peptide (CGRP), and Substance P levels were carried out by enzyme-linked immunosorbent assay (Elisa). The data were analyzed by One-Way ANOVA. The Tukey’s test was used as post-hoc.

Results: Endometriosis induction significantly increased the mean pain scores in the endometriosis group in all three phases of the formalin test. The concentrations of DRG-CGRP (p=0.035), BDNF (p<0.001), and NGF (p=0.006) in the endometriosis group were significantly higher than that of the other groups while serum-BDNF (p<0.001), Substance P (p=0.009), and NGF (p=0.015) were significantly lower in endometriosis group compared to other groups. The concentrations of PF-BDNF (p=0.025) and Substance P (p=0.009) were significantly lower than those of other groups.

Conclusion: The present results delineate that endometriosis induction could lead to hyperalgesia. This may be related to the significant increases in the BDNF, NGF, and CGRP in DRG.

Reduced vagal tone in women with endometriosis and auricular vagus nerve stimulation as a potential therapeutic approach

Sensory and sympathetic nerves have been shown to promote the progression of endometriosis through the release of neuromediators and the lesional activation of respective receptors. The role of vagus nerves (VN) in lesional progression, however, is completely unclear, despite the signs suggestive of increased sympathetic tone in women with endometriosis. This study was undertaken to investigate whether VN plays any role in the progression of endometriosis. We recruited 45 patients with endometriosis and 42 healthy women, who were given electrocardiogram test and their heart rate variability was evaluated. In addition, three prospective, and randomized mouse experiments were conducted that evaluated, respectively, the effect of vagotomy, the effect of VN stimulation (VNS), and the therapeutic potential of VNS after the endometriosis was well established. All lesions were excised, weighed, and processed for immunohistochemistry and histochemistry analysis of select markers for lesional progression and fibrosis. We found that endometriosis patients exhibited reduced vagal activity as compared with controls, indicative of disrupted autonomic balance. Vagotomy increased while VNS decreased the lesion weight as compared with control mice, concomitant with more progressive and retarded lesion development and fibrogenesis, respectively. In addition, VNS demonstrated promising therapeutic effect, as evidenced by significantly reduced lesion weight, more attenuated lesional progression concomitant with improved hyperalgesia. Taken together, our data indicate that VN activity may play a dampening role in the progression of endometriosis. Consequently, boosting the VN activity may have therapeutic potentials for patients with endometriosis.

Inflammatory Mediators and Pain in Endometriosis: A Systematic Review

BACKGROUND

pain is one of the main symptoms of endometriosis and it has a deleterious effect on a patients' personal and social life. To date, the clinical management of pain includes prolonged medication use and, in some cases, surgery, both of which are disruptive events for patients. Hence, there is an urgency for the development of a sufficient non-invasive medical treatment. Inflammation is one of the causative factors of pain in endometriosis. It is well established that inflammatory mediators promote angiogenesis and interact with the sensory neurons inducing the pain signal; the threshold of pain varies and it depends on the state and location of the disease. The inhibition of inflammatory mediators' synthesis might offer a novel and effective treatment of the pain that is caused by inflammation in endometriosis.

OBJECTIVES

patients with endometriosis experience chronic pelvic pain, which is moderate to severe in terms of intensity. The objective of this systematic review is to highlight the inflammatory mediators that contribute to the induction of pain in endometriosis and present their biological mechanism of action. In addition, the authors aim to identify new targets for the development of novel treatments for chronic pelvic pain in patients with endometriosis.

DATA SOURCES

three databases (PubMed, Scopus, and Europe PMC) were searched in order to retrieve articles with the keywords 'inflammation, pain, and endometriosis' between the review period of 1 January 2016 to 31 December 2020. This review has been registered with PROSPERO (registry number: CRD42020171018). Eligibility Criteria: only original articles that presented the regulation of inflammatory mediators and related biological molecules in endometriosis and their contribution in the stimulation of pain signal were included.

DATA EXTRACTION

two authors independently extracted data from articles, using predefined criteria.

RESULTS

the database search yielded 1871 articles, which were narrowed down to 56 relevant articles of interest according to the eligibility criteria.

CONCLUSIONS

inflammatory factors that promote angiogenesis and neuroangiogenesis are promising targets for the treatment of inflammatory pain in endometriosis. Specifically, CXC chemokine family, chemokine fractalkine, and PGE2 have an active role in the induction of pain. Additionally, IL-1β appears to be the primary interleukin (IL), which stimulates the majority of the inflammatory factors that contribute to neuroangiogenesis along with IL-6. Finally, the role of Ninj1 and BDNF proteins needs further investigation.

[Endosalpingiosis - an Irrelevant Incidental Finding During Laparoscopy?]

Endosalpingiosis - an Irrelevant Incidental Finding During Laparoscopy? Abstract. Endosalpingiosis refers to the ectopic presence of tubal epithelium. However, this incidental finding received little attention, although it is the second most common benign peritoneal pathology in women following endometriosis. In contrast to endometriosis, endosalpingiosis shows an increase in prevalence with age beyond the menopause. Furthermore, it does not appear to be chronically inflammatory and, according to research to this date, does not cause chronic pain or infertility. Recent epidemiological and molecular pathological studies show a significantly higher incidence of ovarian and endometrial tumors in women with endosalpingiosis. These correlations have not been conclusively clarified. Generally accepted clinical recommendations for the detection of endosalpingiosis do not yet exist. In order to better understand the disease value of endosalpingiosis and its oncological correlations, this entity should be brought to the attention of surgical gynecology and involved pathology.

Purinergic Signaling in Endometriosis-Associated Pain

Endometriosis is an estrogen-dependent gynecological disease, with an associated chronic inflammatory component, characterized by the presence of endometrial tissue outside the uterine cavity. Its predominant symptom is pain, a condition notably altering the quality of life of women with the disease. This review is intended to exhaustively gather current knowledge on purinergic signaling in endometriosis-associated pain. Altered extracellular ATP hydrolysis, due to changes in ectonucleotidase activity, has been reported in endometriosis; the resulting accumulation of ATP in the endometriotic microenvironment points to sustained activation of nucleotide receptors (P2 receptors) capable of generating a persistent pain message. P2X3 receptor, expressed in sensory neurons, mediates nociceptive, neuropathic, and inflammatory pain, and is enrolled in endometriosis-related pain. Pharmacological inhibition of P2X3 receptor is under evaluation as a pain relief treatment for women with endometriosis. The role of other ATP receptors is also discussed here, e.g., P2X4 and P2X7 receptors, which are involved in inflammatory cell-nerve and microglia-nerve crosstalk, and therefore in inflammatory and neuropathic pain. Adenosine receptors (P1 receptors), by contrast, mainly play antinociceptive and anti-inflammatory roles. Purinome-targeted drugs, including nucleotide receptors and metabolizing enzymes, are potential non-hormonal therapeutic tools for the pharmacological management of endometriosis-related pain.

Pain in Endometriosis

Endometriosis is a chronic and debilitating condition affecting ∼10% of women. Endometriosis is characterized by infertility and chronic pelvic pain, yet treatment options remain limited. In many respects this is related to an underlying lack of knowledge of the etiology and mechanisms contributing to endometriosis-induced pain. Whilst many studies focus on retrograde menstruation, and the formation and development of lesions in the pathogenesis of endometriosis, the mechanisms underlying the associated pain remain poorly described. Here we review the recent clinical and experimental evidence of the mechanisms contributing to chronic pain in endometriosis. This includes the roles of inflammation, neurogenic inflammation, neuroangiogenesis, peripheral sensitization and central sensitization. As endometriosis patients are also known to have co-morbidities such as irritable bowel syndrome and overactive bladder syndrome, we highlight how common nerve pathways innervating the colon, bladder and female reproductive tract can contribute to co-morbidity via cross-organ sensitization.

Inhibition of receptor activity-modifying protein 1 suppresses the development of endometriosis and the formation of blood and lymphatic vessels

Neuroimmune interactions are involved in the development of endometriosis. Here, we examined the role of a neuropeptide, calcitonin gene–related peptide (CGRP), and its receptor, receptor activity–modifying protein (RAMP) 1, in growth of endometrial tissues and the formation of blood and lymphatic vessels in a mouse ectopic endometrial transplantation model. Endometrial fragments from donor wild‐type (WT) mice transplanted into the peritoneal wall of recipient WT mice grew with increased density of blood and lymphatic vessels. When tissues from RAMP1‐deficient (RAMP1^−/−) mice were transplanted into RAMP1^−/− mice, implant growth and angiogenesis/lymphangiogenesis were decreased. CGRP was up‐regulated in dorsal root ganglia, and CGRP⁺ nerve fibres were distributed into the implants from the peritoneum. RAMP1 was co‐expressed with CD11b (macrophages) and S100A4 (fibroblasts), but did not co‐localize with blood vessel endothelial cell marker CD31 or lymphatic vessel endothelial hyaluronan receptor (LYVE)‐1. Cultured with CGRP, macrophages up‐regulated vascular endothelial growth factor (VEGF)‐A, VEGF‐C and VEGF‐D, whereas fibroblasts up‐regulated VEGF‐C, but not VEGF‐A or VEGF‐D, in a RAMP1‐dependent manner. CGRP receptor antagonist CGRP8‐37 inhibited growth of and angiogenesis/lymphangiogenesis within endometrial tissue implants. These results suggest that RAMP1 signalling is crucial for growth and angiogenesis/lymphangiogenesis in endometrial tissue. Blockade of RAMP1 is a potential tool for the treatment of endometriosis.

The establishment of a mouse model of deep endometriosis

STUDY QUESTION

Is it possible to establish a mouse model of deep endometriosis (DE)?

SUMMARY ANSWER

A mouse DE model that is macroscopically and microscopically similar to nodular lesions in humans can be constructed in as short as 3 weeks by intraperitoneal injection of uterine fragments along with the infusion of substance P (SP) and/or calcitonin gene-related peptide (CGRP).

WHAT IS KNOWN ALREADY

Although a baboon DE model was reported 5 years ago, its prohibitive cost and demand for facilities and expertise associated with the use of non-human primates put its use out of reach for most laboratories.

STUDY DESIGN, SIZE, DURATION

A total of 48 female Balb/C mice were used for this study. Among them, 16 were randomly selected as donors that contributed uterine fragments, and the remaining 32 were recipient mice. The mice with induced endometriosis were followed up for 3-4 weeks.

PARTICIPANTS/MATERIALS, SETTING, METHODS

One day before the induction of endometriosis by intraperitoneal injection of uterine fragments, osmotic pumps were inserted into equal groups of recipient mice to infuse either sterile saline, SP, CGRP, or both SP and CGRP. The hotplate test was administrated to all mice at the baseline and before and after induction of endometriosis. Four (3 for the SP+CGRP group) weeks after induction, all mice were sacrificed. Their endometriotic lesions were excised, weighed and processed for histopathologic examination, and histochemistry, immunohistochemistry and immunofluorescence analyses of markers of proliferation, angiogenesis, epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT), smooth muscle metaplasia (SMM), mesothelial-mesenchymal transition (MMT) and endothelial-mesenchymal transition (EndoMT) were done. The extent of lesional fibrosis was evaluated by Masson trichrome staining. To further evaluate surrounding organ/tissue invasion, the peritoneal areas adhesive to the lesions were excised for immunohistochemical analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

Endometriotic lesions in mice treated with SP and/or CGRP satisfied all requirements for DE, i.e. presence of endometrial epithelial and stromal cells, abundance of fibromuscular content, and encapsulation in surrounding tissues or organs. The lesion weight in the CGRP, SP and SP+CGRP groups was 1.62, 2.14 and 2.18-fold, respectively, heavier than that of control group. Concomitantly, the SP, CGRP and SP+CGRP groups had significantly shorter hotplate latency than that of control group. Lesions in mice treated with SP and/or CGRP, especially with SP+CGRP, exhibited characteristics consistent with EMT, FMT, SMM and extensive fibrosis, along with signs of MMT and EndoMT. Lesional invasion into surrounding tissues/organs was found to be 25.0, 75.0 and 87.5% in mice treated with CGRP, SP and SP+CGRP, but none in control mice.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This study is limited by the use of histologic and immunohistochemistry analyses only and lacks molecular data.

WIDER IMPLICATIONS OF THE FINDINGS

The establishment of a mouse DE model supports the idea that endometriotic lesions are wounds undergoing repeated tissue injury and repair and underscores the importance of microenvironments in shaping the lesions' destiny. In addition, signs consistent with MMT and EndoMT indicate that there may be more culpable factors that still remain unidentified and should be pursued in the future. Moreover, the close correlation between the extent of lesional fibrosis and markers of EMT, MMT, EndoMT, FMT and SMM as shown here should facilitate our understanding of the molecular mechanisms underlying the DE pathophysiology. Since this DE model is based on a biologically plausible and evidence-backed theory, it should shed much needed insight into the molecular mechanisms underlying the pathophysiology of DE.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by Grants 81471434 (S.W.G.), 81530040 (S.W.G.), 81771553 (S.W.G.), 81671436 (X.S.L.) and 81871144 (X.S.L.) from the National Natural Science Foundation of China. None of the authors has any conflict of interest to disclose.

Endometriosis and the Fallopian Tubes: Theories of Origin and Clinical Implications

Endometriosis is a common, oestrogen driven chronic condition, where endometrium-like epithelial and stromal cells exist in ectopic sites. At present, no curative treatments are available and the existing evidence for disease progression is conflicting. The pathogenesis is still unknown and evidently complex, as mechanisms of initiation may depend on the anatomical distribution of endometriotic lesions. However, amongst the numerous theories and plethora of mechanisms, contributions of the fallopian tubes (FT) to endometriosis are rarely discussed. The FT are implicated in all endometriosis associated symptomatology and clinical consequences; they may contribute to the origin of endometriotic tissue, determine the sites for ectopic lesion establishment and act as conduits for the spread of proinflammatory media. Here, we examine the available evidence for the contribution of the human FT to the origin, pathogenesis and symptoms/clinical consequences of endometriosis. We also examine the broader topic linking endometriosis and the FT epithelium to the genesis of ovarian epithelial cancers. Further studies elucidating the distinct functional and phenotypical characteristics of FT mucosa may allow the development of novel treatment strategies for endometriosis that are potentially curative.

Macrophage-derived netrin-1 is critical for neuroangiogenesis in endometriosis

Netrin-1 is an extracellular guidance cue of neuronal navigation, mediated through interaction with its main receptors, and is known to be crucial in the development of multiple chronic inflammatory diseases. However, the expression pattern and mechanism of netrin-1 in endometriosis are currently undefined. Here we report that netrin-1 expression peaked in peritoneal macrophages found in endometriosis. Netrin-1 induced angiogenesis in ovarian endometriomas through interaction with CD146 in vascular endothelial cells. Through another receptor, neogenin, netrin-1 promoted neurite growth and sensitization in endometriosis through the up-regulation of MAP4, TAU, and CGRP. Targeted knockdown of neogenin in dorsal root ganglion (DRG) nerve cells compromised its response to netrin-1 through inhibiting phosphorylation of ERK1/2. The inhibition of netrin-1 using a neutralizing antibody reduced vascular and nerve infiltration in rat endometriotic lesions. In summary, our results suggest that netrin-1 is an important factor that promotes neuroangiogenesis in 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.

Endometriosis-Associated Macrophages: Origin, Phenotype, and Function

Endometriosis is a complex, heterogeneous, chronic inflammatory condition impacting ~176 million women worldwide. It is associated with chronic pelvic pain, infertility, and fatigue, and has a substantial impact on health-related quality of life. Endometriosis is defined by the growth of endometrial-like tissue outside the uterus, typically on the lining of the pelvic cavity and ovaries (known as "lesions"). Macrophages are complex cells at the center of this enigmatic condition; they are critical for the growth, development, vascularization, and innervation of lesions as well as generation of pain symptoms. In health, tissue-resident macrophages are seeded during early embryonic life are vital for development and homeostasis of tissues. In the adult, under inflammatory challenge, monocytes are recruited from the blood and differentiate into macrophages in tissues where they fulfill functions, such as fighting infection and repairing wounds. The interplay between tissue-resident and recruited macrophages is now at the forefront of macrophage research due to their differential roles in inflammatory disorders. In some cancers, tumor-associated macrophages (TAMs) are comprised of tissue-resident macrophages and recruited inflammatory monocytes that differentiate into macrophages within the tumor. These macrophages of different origins play differential roles in disease progression. Herein, we review the complexities of macrophage dynamics in health and disease and explore the paradigm that under disease-modified conditions, macrophages that normally maintain homeostasis become modified such that they promote disease. We also interrogate the evidence to support the existence of multiple phenotypic populations and origins of macrophages in endometriosis and how this could be exploited for therapy.

Endometrial biopsy and density of nerve fibers in eutopic endometrium. Looking for easier ways to diagnose endometriosis

The purpose of study was to evaluate if there is any difference between nerve fibers density in eutopic endometrium in women with and without endometriosis. The prospective case - control study conducted between October 2013 and December 2015. The study included 60 reproductive age women undergoing laparoscopy for suspected endometriosis, pelvic pain, or infertility and not currently receiving hormonal treatment for at least 3 months prior to laparoscopy. Immunohistochemical nerve fiber detection in endometrial curetting using anti-gene product 9.5 was compared with surgical diagnosis. The nerve fibers were detected in eutopic endometrium in women with and without endometriosis. PGP9.5 positive nerve fibers were found in 26 (43%) cases: 16 (50%) in women with endometriosis and 10 (36%) in women without endometriosis. The mean nerve fiber density was higher in the group with endometriosis (0.53 per mm² ± 0.68) than without endometriosis (0.48 per mm² ± 0.89), but no statistically significant difference was observed (p > .05). Test specificity was 64.3%, sensitivity 50%, positive predictive value - 61.5%, negative predictive value - 52.9%, and overall accuracy 56.7%. The detection of PGP9.5 positive nerve fibers in eutopic endometrium cannot be used as a reliable diagnostic test of diagnosing endometriosis.

Macrophage-derived insulin-like growth factor-1 is a key neurotrophic and nerve-sensitizing factor in pain associated with endometriosis

Endometriosis is a common incurable inflammatory disorder that is associated with debilitating pelvic pain in women. Macrophages are central to the pathophysiology of endometriosis: they dictate the growth and vascularization of endometriosis lesions and more recently have been shown to promote lesion innervation. The aim of this study was to determine the mechanistic role of macrophages in producing pain associated with endometriosis. Herein, we show that macrophage depletion in a mouse model of endometriosis can reverse abnormal changes in pain behavior. We identified that disease-modified macrophages exhibit increased expression of IGF-1 in an in vitro model of endometriosis-associated macrophages and confirmed expression by lesion-resident macrophages in mice and women. Concentrations of IGF-1 were elevated in peritoneal fluid from women with endometriosis and positively correlate with their pain scores. Mechanistically, we demonstrate that macrophage-derived IGF-1 promotes sprouting neurogenesis and nerve sensitization in vitro. Finally, we show that the Igf-1 receptor inhibitor linsitinib reverses the pain behavior observed in mice with endometriosis. Our data support a role for macrophage-derived IGF-1 as a key neurotrophic and sensitizing factor in endometriosis, and we propose that therapies that modify macrophage phenotype may be attractive therapeutic options for the treatment of women with endometriosis-associated pain.-Forster, R., Sarginson, A., Velichkova, A., Hogg, C., Dorning, A., Horne, A. W., Saunders, P. T. K., Greaves, E. Macrophage-derived insulin-like growth factor-1 is a key neurotrophic and nerve-sensitizing factor in pain associated with endometriosis.

Possible Role of the Posterior Compartment Peritonectomy, as a Part of the Complex Surgery, Regarding Recurrence Rate, Improvement of Symptoms and Fertility Rate in Patients with Endometriosis, Long-Term Follow-Up

STUDY OBJECTIVE

Beside the pain, there are 2 further problems in the management of endometriosis: the high recurrence rate (10% per year) and the high rate of impaired fertility. The objective of this study was to investigate the pathogenesis of these 2 factors.

DESIGN

This is a retrospective cohort study, and the aim is to evaluate the complete excision of endometriotic lesions, including the posterior compartment of the peritoneum, with regard to postoperative outcome, focusing on relieving pain, increasing fertility rate, and decreasing recurrence rate.

SETTING

Charité-University Clinic, Department of Gynaecology, Endometriosis research Centre.

PATIENTS

Fifty-four patients were enrolled in this study, with severe deep infiltrating endometriosis (scored by ENZIAN) and superficial endometriosis, as well as endometriomas (revised American Society for Reproductive Medicine [rASRM] I = 3; II = 15; III = 10; and IV = 26).

INTERVENTIONS

Posterior compartment peritonectomy (visible endometriotic lesions and inflamed altered peritoneum) was performed in all patients as part of a complex surgery: complete excision of endometriosis.

MEASUREMENTS AND MAIN RESULTS

Postoperative outcomes were evaluated, based on the postoperative follow-up (up to 5 years) of 54 investigated patients. In 36 women (66%) preoperative complaints were eliminated. Furthermore, of 28 women seeking improved fertility, pregnancy was reported in 13 cases (46%). In 7 (54%) cases pregnancy occurred spontaneously, and in the remainder with assisted fertilization. In addition, long-term follow-up demonstrated a recurrence rate in 1.8% of patients.

CONCLUSION

Overall, the number of complaints was significantly reduced. Only in the case of reproductive-aged women with ongoing postoperative complaints was it important to preserve the uterus. Although this pilot study on systematic posterior peritonectomy showed improvement in recurrence and fertility rate, the main question remains: will this surgical technique achieve better results and outcomes in the future? This has to be addressed in a prospective randomized study.

Endometriotic lesions

Endometriosis is a complex gynaecological condition affecting women of reproductive age. It is characterised by the presence of lesions containing endometrial glands and stroma outside the uterus. The disease is typically associated with pelvic pain (including dysmenorrhoea and dyspareunia), infertility and bowel-related symptoms. Endometriotic lesions have a highly variable presentation and most commonly occur in the abdominal cavity. These lesions are broadly classified into peritoneal, ovarian and deep infiltrating endometriosis. There have been observations of increased density of nerve fibres and neurological molecules in the endometriotic lesions compared to the uninvolved peritoneum of women without endometriosis and the presence of unmyelinated nerve fibres were higher near the glands. The lesion sites are characterised by a range of immunological alterations, and specific immune cell populations have also been known to synthesise and secrete neurogenic factors. Endometriotic lesions are capable of producing prostaglandins which are direct generators of pain and are capable of inducing inflammation. Diagnosing the disease involves direct visualisation of the lesions through a laparoscopic or laparotomy, which is followed by histopathological examination of biopsied or excised lesions. The staging of endometriosis due to its complexity is highly variable as presentation and gaps in knowledge pose a great challenge in the classification of the disease. The medical management of endometriosis aims at providing adequate analgesia and suppression of the activity of the lesion. A better understanding of endometriotic lesion relationships between innervations and specific clinical characteristics may elucidate aspects of pain mechanisms and infertility in endometriosis and facilitate the development of novel therapeutic approaches.

Neuropeptides Substance P and Calcitonin Gene Related Peptide Accelerate the Development and Fibrogenesis of Endometriosis

Endometriotic lesions are known to be hyperinnervated, especially in lesions of deep endometriosis (DE), which are frequently in close proximity to various nerve plexuses. DE lesions typically have higher fibromuscular content than that of ovarian endometriomas (OE) lesions, but the underlying reason remains elusive. Aside from their traditional role of pain transduction, however, whether or not sensory nerves play any role in the development of endometriosis is unclear. Here, we show that, thorough their respective receptors neurokinin receptor 1 (NK1R), calcitonin receptor like receptor (CRLR), and receptor activity modifying protein 1 (RAMP-1), neuropeptides substance P (SP) and calcitonin gene related peptide (CGRP) induce epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT) and further turn stromal cells into smooth muscle cells (SMCs) in endometriotic lesions, resulting ultimately in fibrosis. We show that SP and CGRP, or the rat dorsal root ganglia (DRG) supernatant, through the induction of NK1R and CGRP/CRLR/RAMP-1 signaling pathways, promoted EMT, FMT and SMM in endometriosis, resulting in increased migratory and invasive propensity, cell contractility, production of collagen, and eventually to fibrosis. Neutralization of NK1R and/or CGRP/CRLR/RAMP-1 abrogated these processes. Extended exposure of endometriotic stromal cells to SP and/or CGRP or the DRG supernatant induced increased expression of α-SMA, desmin, oxytocin receptor, and smooth muscle myosin heavy-chain. Finally, we show that DE lesions had significantly higher nerve fiber density, increased staining levels of α-SMA, NK1R, CRLR, and RAMP-1, concomitant with higher lesional fibrotic content than that of OE lesions. The extent of lesional fibrosis correlated positively with the staining levels of NK1R, CRLR, and RAMP-1, as well as the nerve fiber density in lesions. Thus, this study provides another piece of evidence that sensory nerves play an important role in promoting the development and fibrogenesis of endometriosis. It explains as why DE frequently have higher fibromuscular content than that of OE, highlights the importance of lesional microenvironment in shaping the lesional fate, gives more credence to the idea that ectopic endometrium is fundamentally wounds that go through repeated tissue injury and repair, and should shed much needed light into the pathophysiology of endometriosis.

GZFLW Induces Apoptosis of Ectopic Endometrial Stromal Cells via Promoting VPS53 Protein Stability

Endometriosis is still a major problem in obstetrics and gynecology. While GZFLW (Gui Zhi Fu Ling Wan) has been originally used for treating gynecological diseases, however, the molecular mechanism that GZFLW acts on endometriosis is not clear. To investigate the molecular mechanism that GZFLW plays role on endometriosis, iTRAQ (isobaric tags for relative and absolute quantification) proteomics and human endometrial stromal cells (Y14) obtained from a patient with endometriosis were used in in vitro study. Our results demonstrated that GZFLW decreased Y14 cells proliferation while increased cells apoptosis. The differential expression protein VPS53 (Vacuolar protein sorting 53 homolog) was predicted by iTRAQ coupled LC-MS/MS and further identified by western blot. Besides, GZFLW induced VPS53 protein level by promoting its stabilization. Our findings highlight a novel role for VPS53 in gynecology and provide a potent therapeutic strategy against endometriosis.

Partners in Crime: NGF and BDNF in Visceral Dysfunction

Neurotrophins (NTs), particularly Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF), have attracted increasing attention in the context of visceral function for some years. Here, we examined the current literature and presented a thorough review of the subject. After initial studies linking of NGF to cystitis, it is now well-established that this neurotrophin (NT) is a key modulator of bladder pathologies, including Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) and Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS. NGF is upregulated in bladder tissue and its blockade results in major improvements on urodynamic parameters and pain. Further studies expanded showed that NGF is also an intervenient in other visceral dysfunctions such as endometriosis and Irritable Bowel Syndrome (IBS). More recently, BDNF was also shown to play an important role in the same visceral dysfunctions, suggesting that both NTs are determinant factors in visceral pathophysiological mechanisms. Manipulation of NGF and BDNF improves visceral function and reduce pain, suggesting that clinical modulation of these NTs may be important; however, much is still to be investigated before this step is taken. Another active area of research is centered on urinary NGF and BDNF. Several studies show that both NTs can be found in the urine of patients with visceral dysfunction in much higher concentration than in healthy individuals, suggesting that they could be used as potential biomarkers. However, there are still technical difficulties to be overcome, including the lack of a large multicentre placebo-controlled studies to prove the relevance of urinary NTs as clinical biomarkers.

Villainous role of estrogen in macrophage-nerve interaction in endometriosis

Endometriosis is a complex and heterogeneous disorder with unknown etiology. Dysregulation of macrophages and innervation are important factors influencing the pathogenesis of endometriosis-associated pain. It is known to be an estrogen-dependent disease, estrogen can promote secretion of chemokines from peripheral nerves, enhancing the recruitment and polarization of macrophages in endometriotic tissue. Macrophages have a role in the expression of multiple nerve growth factors (NGF), which mediates the imbalance of neurogenesis in an estrogen-dependent manner. Under the influence of estrogen, co-existence of macrophages and nerves induces an innovative neuro-immune communication. Persistent stimulation by inflammatory cytokines from macrophages on nociceptors of peripheral nerves aggravates neuroinflammation through the release of inflammatory neurotransmitters. This neuro-immune interaction regulated by estrogen sensitizes peripheral nerves, leading to neuropathic pain in endometriosis. The aim of this review is to highlight the significance of estrogen in the interaction between macrophages and nerve fibers, and to suggest a potentially valuable therapeutic target for endometriosis-associated pain.

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.

Nerve fibre infiltration and expression in peritoneal lesions of endometriosis in a nonhuman primate model of endometriosis

Baboon ( Papio anubis) models of endometriosis are thought to mimic the early stages of spontaneous human peritoneal endometriotic disease. The objective of this study was to investigate the presence and course of nerve fibre ingrowth during peritoneal lesion formation in specimens collected at 3 months (early stage of lesion development) and 15 months (late stage of lesion development) after disease initiation compared to pelvic peritoneum (control). Five-micron sections of paraffin-embedded peritoneal lesions were obtained from normally cycling baboons with 3-month (n = 12), 15-month (n = 12) induced endometriosis and pelvic peritoneum (n = 10) from baboons with no endometriosis. Immunohistochemical staining was performed with specific antibodies: protein gene product 9.5 – broad marker of nerve fibres and neurones, neuropeptide Y – sympathetic neurones, substance P – sensory neurones, vasoactive intestinal peptide – parasympathetic neurones, nerve growth factor – development of new neurones and high-affinity receptor for nerve growth factor (tropomyosin receptor kinase A) – neuronal differential. Significantly, more nerve fibres were identified in peritoneal endometriotic lesions collected 15 months after the initiation of experimental protocols compared with 3-month and control samples (p < 0.001). Nerve fibres were immunoreactive for all the tested markers – protein gene product 9.5, neuropeptide Y, substance P, vasoactive intestinal peptide, nerve growth factor and tropomyosin receptor kinase A – indicating the presence of different types of nerve fibres. In conclusion, peritoneal lesions of endometriosis in a nonhuman primate model of endometriosis were found to be progressively and spontaneously innervated by both myelinated and unmyelinated sensory nerve fibres, parasympathetic and sympathetic neurones. These nerve fibres may play an important role in the mechanisms of pain generation in this condition.