Activation of vestibule-associated lymphoid tissue in localized provoked vulvodynia

Exploring Localized Provoked Vulvodynia: Insights from Animal Model Research

Provoked vulvodynia represents a challenging chronic pain condition, characterized by its multifactorial origins. The inherent complexities of human-based studies have necessitated the use of animal models to enrich our understanding of vulvodynia's pathophysiology. This review aims to provide an exhaustive examination of the various animal models employed in this research domain. A comprehensive search was conducted on PubMed, utilizing keywords such as "vulvodynia", "chronic vulvar pain", "vulvodynia induction", and "animal models of vulvodynia" to identify pertinent studies. The search yielded three primary animal models for vulvodynia: inflammation-induced, allergy-induced, and hormone-induced. Additionally, six agents capable of triggering the condition through diverse pathways were identified, including factors contributing to hyperinnervation, mast cell proliferation, involvement of other immune cells, inflammatory cytokines, and neurotransmitters. This review systematically outlines the various animal models developed to study the pathogenesis of provoked vulvodynia. Understanding these models is crucial for the exploration of preventative measures, the development of novel treatments, and the overall advancement of research within the field.

Inflammation, lipid dysregulation, and transient receptor potential cation channel subfamily V member 4 signaling perpetuate chronic vulvar pain

ABSTRACT

Localized provoked vulvodynia is characterized by chronic vulvar pain that disrupts every aspect of the patient's life. Pain is localized to the vulvar vestibule, a specialized ring of tissue immediately surrounding the vaginal opening involved in immune defense. In this article, we show inflammation is the critical first step necessary for the generation of pain signals in the vulva. Inflammatory stimuli alone or combined with the transient receptor potential cation channel subfamily V member 4 (TRPV4) agonist 4α-phorbol 12,13-didecanoate stimulate calcium flux into vulvar fibroblast cells. Activity is blocked by the TRPV4 antagonist HC067047, denoting specificity to TRPV4. Using lipidomics, we found pro-resolving lipids in the vulvar vestibule were dysregulated, characterized by a reduction in pro-resolving mediators and heightened production of inflammatory mediators. We demonstrate specialized pro-resolving mediators represent a potential new therapy for vulvar pain, acting on 2 key parts of the disease mechanism by limiting inflammation and acutely inhibiting TRPV4 signaling.

Neuroproliferative dyspareunia in endometriosis and vestibulodynia

INTRODUCTION

Endometriosis is a common cause of deep dyspareunia, while provoked vestibulodynia is a common cause of superficial dyspareunia. The etiology of dyspareunia in both conditions is multifactorial and may include the role of local nerve growth (neurogenesis or neuroproliferation) that sensitizes pelvic structures and leads to pain with contact.

OBJECTIVES

To review the evidence for neuroproliferative dyspareunia in endometriosis and provoked vestibulodynia.

METHODS

Narrative review.

RESULTS

The pelvic peritoneum and vulvar vestibule receive somatic and autonomic innervation. Various markers have been utilized for nerve subtypes, including pan-neuronal markers and those specific for sensory and autonomic nerve fibers. The nerve growth factor family includes neurotrophic factors, such as nerve growth factor and brain-derived neurotrophic factor, and their receptors. Studies of endometriosis and provoked vestibulodynia have demonstrated the presence of nerve fibers around endometriosis epithelium/stroma in the pelvic peritoneum and within the vulvar vestibule. The number of nerve fibers is higher in these pain conditions as compared with control tissue. Nerve growth factor expression by endometriosis stroma and by immune cells in the vulvar vestibule may be involved in local neuroproliferation. Local inflammation is implicated in this neuroproliferation, with potential roles of interleukin 1β and mast cells in both conditions. Several studies have shown a correlation between nerve fibers around endometriosis and dyspareunia severity, but studies are lacking in provoked vestibulodynia. There are several possible clinical ramifications of neuroproliferative dyspareunia in endometriosis and provoked vestibulodynia, in terms of history, examination, biopsy, and surgical and medical treatment.

CONCLUSIONS

A neuroproliferative subtype of dyspareunia may be implicated in endometriosis and provoked vestibulodynia. Additional research is needed to validate this concept and to integrate it into clinical studies. Neuroproliferative pathways could serve as novel therapeutic targets for the treatment of dyspareunia in endometriosis and provoked vestibulodynia.

The Association Between Immune-Related Conditions Across the Life-Course and Provoked Vulvodynia

Vulvodynia, impacts up to 8% of women by age 40, and is hypothesized to manifest through an altered immune-inflammatory response. To test this hypothesis, we identified all women born in Sweden between 1973 and 1996 diagnosed with localized provoked vulvodynia (N76.3) and/or vaginismus (N94.2 or F52.5) between 2001 and 2018. We matched each case to two women from the same birth year with no vulvar pain ICD codes. As a proxy for immune dysfunction, we used Swedish Registry data to capture 1) immunodeficiencies, 2) single organ and multiorgan autoimmune conditions, 3) allergy and atopies, and 4) malignancies involving immune cells across the life course. Women with vulvodynia, vaginismus or both were more likely to experience immune deficiencies (OR 1.8, 95% CI, 1.2-2.8), single organ (OR 1.4, 95% CI, 1.2-1.6) and/or multi-organ (OR 1.6, 95% CI, 1.3-1.9) immune disorders, and allergy/atopy conditions (OR 1.7, 95% CI, 1.6-1.8) compared to controls. We observed greater risk with increasing numbers of unique immune related conditions (1 code: OR = 1.6, 95% CI, 1.5-1.7; 2 codes: OR = 2.4, 95% CI, 2.1-2.9; 3 or more codes: OR = 2.9, 1.6-5.4). These findings suggest that women with vulvodynia may have a more compromised immune system either at birth or at points across the life course than women with no vulvar pain history. PERSPECTIVE: Women with vulvodynia are substantially more likely to experience a spectrum of immune related conditions across the life course. These findings lend support to the hypothesis that chronic inflammation initiates the hyperinnervation that causes the debilitating pain in women with vulvodynia.

Inflammation, lipids, and pain in vulvar disease

Localized provoked vulvodynia (LPV) affects ∼14 million people in the US (9% of women), destroying lives and relationships. LPV is characterized by chronic pain (>3 months) upon touch to the vulvar vestibule, which surrounds the vaginal opening. Many patients go months or years without a diagnosis. Once diagnosed, the treatments available only manage the symptoms of disease and do not correct the underlying problem. We have focused on elucidating the underlying mechanisms of chronic vulvar pain to speed diagnosis and improve intervention and management. We determined the inflammatory response to microorganisms, even members of the resident microflora, sets off a chain of events that culminates in chronic pain. This agrees with findings from several other groups, which show inflammation is altered in the painful vestibule. The vestibule of patients is acutely sensitive to inflammatory stimuli to the point of being deleterious. Rather than protect against vaginal infection, it causes heightened inflammation that does not resolve, which coincides with alterations in lipid metabolism that favor production of proinflammatory lipids and not pro-resolving lipids. Lipid dysbiosis in turn triggers pain signaling through the transient receptor potential vanilloid subtype 4 receptor (TRPV4). Treatment with specialized pro-resolving mediators (SPMs) that foster resolution reduces inflammation in fibroblasts and mice and vulvar sensitivity in mice. SPMs, specifically maresin 1, act on more than one part of the vulvodynia mechanism by limiting inflammation and acutely inhibiting TRPV4 signaling. Therefore, SPMs or other agents that target inflammation and/or TRPV4 signaling could prove effective as new vulvodynia therapies.

Morphological Characteristics of Genital Organ-Associated Lymphoid Tissue in the Vaginal Vestibule of Goats and Pigs

Mucosa-associated lymphoid tissue (MALT) is a specialized form of peripheral lymphoid tissue (LT), which is found on mucosal surfaces exposed to the environment. However, morphological data of these tissues in farm animals are scarce. This study investigated the gross anatomical and histological features of genital organ-associated lymphoid tissues (GOALTs) in the vaginal vestibule (VV) of healthy, non-pregnant, adult goats and pigs. Their VVs were composed of stratified squamous, non-keratinized epithelium, and various-sized dark-blue hematoxylin-positive spots were observed in whole-mount specimens, which were diffusely distributed throughout the mucosal surfaces. These spots were histologically identified as LTs and consisted of lymphatic nodules (LNs) or diffuse lymphoid tissue (DLTs). Both LNs and DLTs contained B cells, T cells, macrophages, dendritic cells, plasma cells, and high endothelial venules. Only the numbers of B cells were significantly higher in both the LNs and DLTs of pigs compared to goats. Furthermore, the surface of the VV epithelium covering the LTs was partially disrupted with a large intercellular space containing abundant connective tissue fibers with numerous lymphocytes. In conclusion, GOALTs in the VV appear to be common local immunological barriers in both examined animals. This knowledge is crucial for understanding the structures and disorders of female reproductive organs in farm animals.

Characterization of Early Inflammatory Events Leading to Provoked Vulvodynia Development in Rats

Background

Provoked vulvodynia (PV) is the main cause of vulvar pain and dyspareunia. The etiology of PV has not yet been elucidated. However, PV is associated with a history of recurrent inflammation, and its often accompanied by increases in the numbers of mast cells (MCs) and sensory hyperinnervation in the vulva. Therefore, this study aimed to examine the role of MCs and the early inflammatory events in the development of chronic vulvar pain in a rat model of PV.

Methods

Mechanical and thermal vulvar sensitivity was measured for 5 months following zymosan vulvar challenges. Vulvar changes in glutamate and nerve growth factor (NGF) were analyzed using ELISA. Immunofluorescence (IF) staining of the vulvar section after 20, 81, and 160 days of the zymosan challenge were performed to test MCs accumulation, hyperinnervation, and expression of pain channels (transient receptor potential vanilloid/ankyrin-1-TRPV1 & TRPA1) in vulvar neurons. Changes in the development of vulvar pain were evaluated following the administration of the MCs stabilizer ketotifen fumarate (KF) during zymosan vulvar challenges.

Results

Zymosan-challenged rats developed significant mechanical and thermal vulvar sensitivity that persisted for over 160 days after the zymosan challenge. During inflammation, increased local concentrations of NGF and glutamate and a robust increase in MCs degranulation were observed in zymosan-challenged rats. In addition, zymosan-challenged rats displayed sensory hyperinnervation and an increase in the expression of TRPV1 and TRPA1. Treatment with KF attenuated the upregulated level of NGF during inflammation, modulated the neuronal modifications, reduced MCs accumulation, and enhanced mechanical hypersensitivity after repeated inflammation challenges.

Conclusion

The present findings suggest that vulvar hypersensitivity is mediated by MCs accumulation, nerve growth, and neuromodulation of TRPV1 and TRPA1. Hence, KF treatment during the critical period of inflammation contributes to preventing chronic vulvar pain development.

A Pilot Proteomic Study of Vestibular Fluid From Patients With Vulvodynia

OBJECTIVE

Many women are affected by vulvodynia, but medical therapies to date have proven ineffective. We performed a pilot study using gel-based proteomics to develop a map of proteins present in vaginal/vestibular secretions and identify proteins that could be considered for future evaluation as potential therapeutic targets.

MATERIALS AND METHODS

We collected vestibular fluid from 4 controls and 4 patients with vulvodynia by placing a cotton swab in the vestibule and extracting the absorbed proteins. The proteins underwent 2-dimensional difference gel electrophoresis and mass spectrometry to develop a protein map. Immunohistochemistry was used to validate proteomic findings.

RESULTS

A map was constructed of 32 of the more abundant proteins in vestibular fluid and their levels compared in control subjects and vulvodynia patients. Among these were annexin A1, interleukin 1 receptor antagonist, protein S100 A9, and a number of antiproteases and proteases. Many of these proteins differed by at least 50% between groups, but only annexin A1, one of the protease inhibitors, and immunoglobulin G κ chain were significantly different. The results with annexin A1 were validated by similar findings with immunohistochemistry.

CONCLUSIONS

The findings of this pilot study demonstrate a set of vestibule mucosa proteins that differ significantly-either increasing or decreasing-in vulvodynia patients compared with controls, and several others that exhibited greater than 1.5-fold change but did not reach statistical significance. This study constitutes a proof-of-principle that an open, unbiased proteomic approach can identify molecular participants in vulvodynia, some of which had not been identified to date by hypothesis-driven studies.

Clodronate Treatment Prevents Vaginal Hypersensitivity in a Mouse Model of Vestibulodynia

Introduction

Improved understanding of vestibulodynia pathophysiology is required to develop appropriately targeted treatments. Established features include vulvovaginal hyperinnervation, increased nociceptive signalling and hypersensitivity. Emerging evidence indicates macrophage-neuron signalling contributes to chronic pain pathophysiology. Macrophages are broadly classified as M1 or M2, demonstrating pro-nociceptive or anti-nociceptive effects respectively. This study investigates the impact of clodronate liposomes, a macrophage depleting agent, on nociceptive signalling in a mouse model of vestibulodynia.

Methods

Microinjection of complete Freund’s adjuvant (CFA) at the vaginal introitus induced mild chronic inflammation in C57Bl/6J mice. A subgroup was treated with the macrophage depleting agent clodronate. Control mice received saline. After 7 days, immunolabelling for PGP9.5, F4/80+CD11c+ and F4/80+CD206+ was used to compare innervation density and presence of M1 and M2 macrophages respectively in experimental groups. Nociceptive signalling evoked by vaginal distension was assessed using immunolabelling for phosphorylated MAP extracellular signal-related kinase (pERK) in spinal cord sections. Hyperalgesia was assessed by visceromotor response to graded vaginal distension.

Results

CFA led to increased vaginal innervation (p < 0.05), increased pERK-immunoreactive spinal cord dorsal horn neurons evoked by vaginal-distension (p < 0.01) and enhanced visceromotor responses compared control mice (p < 0.01). Clodronate did not reduce vaginal hyperinnervation but significantly reduced the abundance of M1 and M2 vaginal macrophages and restored vaginal nociceptive signalling and vaginal sensitivity to that of healthy control animals.

Conclusions

We have developed a robust mouse model of vestibulodynia that demonstrates vaginal hyperinnervation, enhanced nociceptive signalling, hyperalgesia and allodynia. Macrophages contribute to hypersensitivity in this model. Macrophage-sensory neuron signalling pathways may present useful pathophysiological targets.

Desquamative Inflammatory Vaginitis and Plasma Cell Vulvitis Represent a Spectrum of Hemorrhagic Vestibulovaginitis

OBJECTIVE

The aim of the study was to identify whether desquamative inflammatory vaginitis (DIV) and plasma cell vulvitis (PCV) are distinct clinicopathologic entities.

MATERIALS AND METHODS

The pathology database identified biopsies described as "vaginitis" or "vulvitis" occurring in nonkeratinized epithelium or mucocutaneous junction. Exclusions were age less than 18 years, unavailable slides or records, concurrent neoplasia, or histopathology consistent with other entities. Clinical data included demographics, symptoms, examination, microbiology, treatment, and response. Histopathologic review documented site, epithelial thickness and characteristics, infiltrate, and vascular abnormalities. Cases were analyzed according to histopathologic impression of DIV or PCV based on previous pathologic descriptions.

RESULTS

There were 36 specimens classified as DIV and 18 as PCV from 51 women with mean age of 51 years; 3 (6%) had concurrent biopsies with both. Pain was more common in PCV, but rates of discharge, itch, and bleeding were comparable. Rates of petechiae or erythema were similar and vaginal examination was abnormal in 72% of PCV cases. All DIV and 33% of PCV occurred in squamous mucosa; the remaining PCV cases were from mucocutaneous junction. Mean epithelial thickness, rete ridge appearance, exocytosis, and spongiosis were similar in DIV and PCV. Epithelial erosion, wide-diameter lesions, plasma cells, and stromal hemosiderin occurred in both but were more common in PCV. Lymphocyte-obscured basal layer, narrow-diameter lesions, hemorrhage, and vascular congestion were seen in both, but more common and marked in DIV.

CONCLUSIONS

Desquamative inflammatory vaginitis and PCV have overlapping symptoms, signs, and histopathologic features. They may represent a single condition of hemorrhagic vestibulovaginitis with varying manifestations according to location and severity.

Specialized Pro-resolving Mediators Reduce Pro-nociceptive Inflammatory Mediator Production in Models of Localized Provoked Vulvodynia

Localized provoked vulvodynia (LPV) is the most common cause of chronic dyspareunia in premenopausal women, characterized by pain with light touch to the vulvar vestibule surrounding the vaginal opening. The devastating impact of LPV includes sexual dysfunction, infertility, depression, and even suicide. Yet, its etiology is unclear. No effective medical therapy exists; surgical removal of the painful vestibule is the last resort. In LPV, the vestibule expresses a unique inflammatory profile with elevated levels of pro-nociceptive proinflammatory mediators prostaglandin E2 (PGE2) and interleukin-6 (IL-6), which are linked to lower mechanical sensitivity thresholds. Specialized pro-resolving mediators (SPMs), lipids produced endogenously within the body, hold promise as an LPV treatment by resolving inflammation without impairing host defense. Ten of 13 commercially available SPMs reduced IL-6 and PGE2 production by vulvar fibroblasts, administered either before or after inflammatory stimulation. Using a murine vulvar pain model, coupling proinflammatory mediator quantification with mechanical sensitivity threshold determination, topical treatment with the SPM, maresin 1, decreased sensitivity and suppressed PGE2 levels. Docosahexaenoic acid, a precursor of maresin 1, was also effective in reducing PGE2 in vulvar fibroblasts and rapidly restored mouse sensitivity thresholds. Overall, SPMs and their precursors may be a safe and efficacious for LPV. Perspective: Vulvodynia, like many pain conditions, is difficult to treat because disease origins are incompletely understood. Here, we applied our knowledge of more recently discovered vulvodynia disease mechanisms to screen novel therapeutics. We identified several specialized pro-resolving mediators as likely potent and safe for treating LPV with potential for broader application.

Localized Provoked Vulvodynia-An Ignored Vulvar Pain Syndrome

Localized provoked vulvodynia (LPV) causes dyspareunia among reproductive aged women. We review the pathogenesis of LPV and suggest that LPV is an inflammatory pain syndrome of the vestibular mucosa triggered by microbial antigens in a susceptible host. Tissue inflammation and hyperinnervation are characteristic findings which explain symptoms and clinical signs. Education of health care providers of LPV is important since this condition is common, often unrecognized, and patients often become frustrated users of health care. Research is needed on the antigen triggers of the syndrome. Randomized clinical trials are needed to evaluate treatment modalities.

Reproductive system infections in women: lower genital tract syndromes

Gynecological and obstetrical infectious diseases are an important component of women's health. A system approach to gynecological and obstetrical infection helps unify and classify microbial etiology and pathogenesis within a clinical anatomical framework of lower and upper genital tract syndromes. The reproductive system of women includes the vulva, vagina, cervix, uterus, fallopian tubes and ovaries. During pregnancy, additional tissues include the chorioamnion and placenta together with the fetus and amniotic fluid. We review in two parts reproductive system infection syndromes in women using selected research results to illustrate the clinical utility of the system approach in terms of diagnosis, treatment and prevention. We conclude that a reproductive system perspective will lead to improvements in understanding, management and prevention of these diseases.

Clinicopathologic Diagnostic Criteria for Vulvar Lichen Planus

OBJECTIVE

The aim of the study was to describe the clinical and histopathologic features required for a clinicopathologic diagnosis of vulvar lichen planus (LP), which is divided into 3 types: erosive, classic, and hypertrophic.

MATERIALS AND METHODS

The International Society of the Study of Vulvovaginal Diseases tasked the Difficult Pathologic Diagnoses committee with development of a consensus document for the clinicopathologic diagnosis of vulvar LP, lichen sclerosus, and differentiated vulvar intraepithelial neoplasia. The LP subgroup reviewed the literature and formulated diagnostic criteria, then approved by the International Society of the Study of Vulvovaginal Diseases membership.

RESULTS

The clinicopathologic diagnosis of erosive LP incorporates 5 criteria: (a) a well-demarcated, glazed red macule or patch at labia minora, vestibule, and/or vagina, (b) disease affects hairless skin, mucocutaneous junction, and/or nonkeratinized squamous epithelium, (c) evidence of basal layer damage, categorized as degenerative or regenerative, (d) a closely applied band-like lymphocytic infiltrate, and (e) absent subepithelial sclerosis. The clinicopathologic diagnoses of classic and hypertrophic LP each require a characteristic clinical appearance accompanied by hyperkeratosis, hypergranulosis, acanthosis, basal layer degeneration, a closely applied lymphocytic infiltrate, and absent dermal sclerosis, with hypertrophic LP showing marked epithelial abnormality compared with classic LP.

CONCLUSIONS

Clinicopathological correlation yields the most reliable diagnosis of vulvar LP. Disease appearance overlaps with other physiologic, dermatologic, infectious, and neoplastic entities; a low threshold for biopsy at all morphologically distinct areas is recommended. Use of the histopathologic criteria described in this document may reduce the nondiagnostic biopsy rate for clinically diagnosed LP.

Vaginal Microbiota and Mucosal Immune Markers in Women With Vulvovaginal Discomfort

BACKGROUND

Up to 30% of women with vaginal symptoms are not assigned a diagnosis after standard diagnostic assessment.

METHODS

We compared premenopausal women with idiopathic vaginitis (IV) or vulvodynia (VVD) to healthy controls. Microbiota were characterized using rRNA sequencing. Cytokines/chemokines (IL-10, IL-1α, IL-1β, IL-6, IL-8, IL-2, IL-18, IL-4, IL-9, and IL-13) were measured in vaginal lavage fluid using the Meso Scale Discovery platform or ELISA (IL-1ra). Immunoglobulins were measured in vaginal lavage fluid using a bead-based immunoassay (Millipore). Cases and controls were compared using Kruskal-Wallis, analysis of variance, and linear regression or (for microbiome composition) the Bray-Curtis dissimilarity statistic.

RESULTS

We compared 20 women with IV, 30 with VVD, and 52 controls. Most (80%) had greater than 90% 16S rRNA gene sequences from Lactobacillus crispatus, L. jensenii, L. gasseri, or L. iners. In analyses adjusted for age and hormonal contraception (HC), Gardnerella vaginalis was less prevalent and abundant in women with VVD (2/30, 7%) versus controls (16/52, 31%) or IV (5/20, 25%) (P = 0.030). Bray-Curtis dissimilarity was not significantly different between IV and controls or VVD. Fungal sequences were only detected in 5 participants: 2 control, 1 IV, 2 VVD. In univariate analysis, cytokines were not associated with diagnosis. Median vaginal concentration of IgE (but not other immunoglobulins) was lower in women with VVD (P = 0.006).

CONCLUSIONS

Minimal differences in vaginal microbiota and inflammatory markers between women with IV, VVD or controls suggest no striking association between vaginal bacteria, fungi or inflammation and diagnosis in these women.

Activation of the Complement System in the Lower Genital Tract During Pregnancy and Delivery

Background

Human pregnancy alters profoundly the immune system. The local involvement and mechanisms of activation of the complement system in the cervicovaginal milieu during pregnancy and delivery remain unexplored.

Objectives

To determine whether normal pregnancy and delivery are associated with local activation of complement or changes in the immunoglobulin profile in the cervix.

Study Design

This study was designed to assess IgA, IgG, and complement activation in the cervicovaginal area in three groups of patients: i) 49 pregnant women (week 41+3–42+0) not in active labor, ii) 24 women in active labor (38+4–42+2), and iii) a control group of nonpregnant women (n=23) at child-bearing age. We collected mucosal samples from the lateral fornix of the vagina and external cervix during routine visits and delivery. The Western blot technique was used to detect complement C3 and its activation products. For semiquantitative analysis, the bands of the electrophoresed proteins in gels were digitized on a flatbed photo scanner and analyzed. IgA and IgG were analyzed by Western blotting and quantified by ELISA. One-way ANOVA and Tukey’s Multiple Comparison tests were used for statistical comparisons.

Results

A higher abundance but lower activation level of C3 in both the external cervix (P<0.001) and lateral fornix of the vagina (P<0.001) was observed during delivery (58 ± 22, n= 24) in comparison to the groups of nonpregnant (72 ± 13%; mean ± SD, n=23) and pregnant women (78 ± 22%, n=49). Complement activating IgG was detected in higher abundance than IgA in the cervicovaginal secretions of pregnant women. In a small proportion samples also C3-IgG complexes were detected.

Conclusions

Our results reveal an unexpectedly strong activation of the complement system and the presence IgG immunoglobulins in the cervicovaginal area during pregnancy, active labor, and among nonpregnant women. In contrast to the higher amounts of C3 in the cervicovaginal secretions during labor, its activation level was lower. Complement activating IgG was detected in higher concentrations than IgA in the mucosal secretions during pregnancy and labor. Taken together our results imply the presence a locally operating humoral immune system in the cervicovaginal mucosa.

Expression of Estrogen-Related Receptors in Localized Provoked Vulvodynia

Eight percent of women suffer from vulvodynia, a chronic pain condition with unknown etiology. Inflammation and dysregulation of estrogen signaling have been suggested to play a role in the pathogenesis of localized provoked vulvodynia (LPV). Therefore, the aim of the study was to analyze protein expression levels of estrogen-related receptors ERRα, ERRß, ERRγ, estrogen receptor (ERα), and progesterone receptor (PRα) and CD3-positive T cells in the vulvar vestibulum obtained from women suffering from LPV in comparison to healthy, unaffected controls. Vulvar vestibulum tissue specimens were obtained from LPV patients (n = 12) who had undergone modified posterior vestibulectomy and from 15 healthy controls. Protein expression of ERRα, ERRß, ERRγ, ERα, and PRα and CD3-positive T cells was analyzed by immunohistochemistry (IHC). Expression of ERRß was significantly more pronounced in samples from LPV compared to healthy controls (p = 0.006). No significant difference in the expression patterns of ERRα, ERRγ, ERα, PRα, or CD3 cells was detected. To our knowledge, this is the first study reporting ERR expression in normal vestibulum and in vestibulectomy samples from LPV patients. The higher level of ERRß expression detected by IHC may reflect dysregulation of estrogen signaling in LPV.

Emerging Evidence of Macrophage Contribution to Hyperinnervation and Nociceptor Sensitization in Vulvodynia

Vulvodynia is an idiopathic chronic pain disorder and a leading cause of dyspareunia, or pain associated with sexual intercourse, for women. The key pathophysiological features of vulvodynia are vaginal hyperinnervation and nociceptor sensitization. These features have been described consistently by research groups over the past 30 years, but currently there is no first-line recommended treatment that targets this pathophysiology. Instead, psychological interventions, pelvic floor physiotherapy and surgery to remove painful tissue are recommended, as these are the few interventions that have shown some benefit in clinical trials. Recurrence of vulvodynia is frequent, even after vestibulectomy and questions regarding etiology remain. Vestibular biopsies from women with vulvodynia contain increased abundance of immune cells including macrophages as well as increased numbers of nerve fibers. Macrophages have multiple roles in the induction and resolution of inflammation and their function can be broadly described as pro-inflammatory or anti-inflammatory depending on their polarization state. This state is not fixed and can alter rapidly in response to the microenvironment. Essentially, M1, or classically activated macrophages, produce pro-inflammatory cytokines and promote nociceptor sensitization and mechanical allodynia, whereas M2, or alternatively activated macrophages produce anti-inflammatory cytokines and promote functions such as wound healing. Signaling between macrophages and neurons has been shown to promote axonal sprouting and nociceptor sensitization. This mini review considers emerging evidence that macrophages may play a role in nociceptor sensitization and hyperinnervation relevant to vulvodynia and considers the implications for development of new therapeutic strategies.

Toll-Like Receptor Signaling Contributes to Proinflammatory Mediator Production in Localized Provoked Vulvodynia

OBJECTIVES

Localized provoked vulvodynia (LPV) afflicts approximately 8% of women in the United States and represents a huge financial, physical, and psychological burden. Women with LPV experience intense pain localized to the vulvar vestibule (area immediately surrounding vaginal opening). We have identified mechanisms involved in the development of LPV whereby vulvar fibroblasts respond to proinflammatory stimuli to perpetuate an inflammatory response that causes pain. However, these mechanisms are not fully elucidated. Therefore, we explored the role of toll-like receptors (TLRs), a class of innate immune receptors that rapidly respond to microbial assaults.

MATERIALS AND METHODS

To determine whether TLRs are expressed by vulvar fibroblasts and whether these contribute to proinflammatory mediator production and pain in LPV, we examined TLR expression and innate immune responses in fibroblasts derived from painful vestibular regions compared with nonpainful external vulvar regions.

RESULTS

Human vulvar fibroblasts express functional TLRs that trigger production of inflammatory mediators associated with chronic pain. We focused on the TLR-7-imiquimod proinflammatory interaction, because imiquimod, a ligand of TLR-7, may exacerbate pain in women during treatment of human papillomavirus-associated disease.

CONCLUSIONS

Human vulvar fibroblasts express a broad spectrum of TLRs (a new finding). A significantly higher TLR-mediated proinflammatory response was observed in LPV case vestibular fibroblasts, and with respect to the imiquimod-TLR 7 interaction, development of chronic vestibular pain and inflammation may be a possible sequelae of treatment of vulvar human papillomavirus-associated disease. Suppressing enhanced TLR-associated innate immune responses to a spectrum of pathogen-associated molecular patterns may represent a new/effective therapeutic approach for vulvodynia.

Differentiating overlapping symptoms of vulvodynia and pudendal neuralgia

Context

Vulvodynia is defined as a chronic vulvar pain non-associated with infectious, inflammatory, neoplastic or hormonal disorders.

Objectives

To present a case demonstrating the difficulty in assessing concomitant disease in vulvodynia.

Methods

A 26-year-old woman, presented with persistent vulvodynia. She received oral and topical medications and behavioural interventions to lessen sexual pain and restore sexuality. As sexual pain decreased, the patient reported symptoms previously not mentioned: continuous, intense periclitoral pain and numbness at the perineum when sitting for a long time. These new symptoms suggest the involvement of the peripheral neural system. The physical evaluation confirmed right-side pelvic distortion, and pathological increase in lumbar lordosis, which caused neuralgia radiating to the external genitalia and perineum, and overlapping with sexual pain. After diagnosing pudendal neuralgia according to the Nantes criteria, physical treatment and relaxation exercises to de-contract the spine were added to the vulvodynia regimen.

Results

During treatment, vulvodynia was sometimes present but never unbearable, allowing satisfactory sex. With physical therapy, the symptoms of pudendal neuralgia decreased.

Conclusion

Differentiating the presence of two conditions with overlapping symptoms is difficult because the vestibular pain had shadowed pudendal neuralgia symptoms at initial assessment. Syndromes of chronic pain tend to associate with each other and one syndrome may shadow symptoms of the concomitant condition affecting adjacent anatomical areas. Only the accurate identification of all the syndromes involved allows adopting the correct treatment.

Inflammatory Renin-Angiotensin System Disruption Attenuates Sensory Hyperinnervation and Mechanical Hypersensitivity in a Rat Model of Provoked Vestibulodynia

Vestibulodynia is characterized by perivaginal mechanical hypersensitivity, hyperinnervation, and abundant inflammatory cells expressing renin-angiotensin system proteins. We developed a tractable rat model of vestibulodynia to further assess the contributions of the renin-angiotensin system. Complete Freund's adjuvant injected into the posterior vestibule induced marked vestibular hypersensitivity throughout a 7-day test period. Numbers of axons immunoreactive for PGP9.5, calcitonin gene-related peptide, and GFRα2 were increased. Numbers of macrophages and T cells were also increased whereas B cells were not. Renin-angiotensin-associated proteins were abundant, with T cells as well as macrophages contributing to increased renin and angiotensinogen. Media conditioned with inflamed vestibular tissue promoted neurite sprouting by rat dorsal root ganglion neurons in vitro, and this was blocked by the angiotensin II receptor type 2 receptor antagonist PD123319 or by an angiotensin II function blocking antibody. Sensory axon sprouting induced by inflamed tissue was dependent on activity of angiotensin-converting enzyme or chymase, but not cathepsin G. Thus, vestibular Complete Freund's adjuvant injection substantially recapitulates changes seen in patients with provoked vestibulodynia, and shows that manipulation of the local inflammatory renin-angiotensin system may be a useful therapeutic strategy.

PERSPECTIVE

This study provides evidence that inflammation of the rat vestibule induces a phenotype recapitulating behavioral and cytological features of human vestibulodynia. The model confirms a crucial role of the local inflammatory renin-angiotensin system in hypersensitivity and hyperinnervation. Targeting this system holds promise for developing new nonopioid analgesic treatment strategies.

Repeated hapten exposure induces persistent tactile sensitivity in mice modeling localized provoked vulvodynia

Background

Vulvodynia is a remarkably prevalent chronic pain condition of unknown etiology. Epidemiologic studies associate the risk of vulvodynia with a history of atopic disease. We used an established model of hapten-driven contact hypersensitivity to investigate the underlying mechanisms of allergy-provoked prolonged sensitivity to pressure.

Methods

We sensitized female ND4 Swiss mice to the hapten oxazolone on their flanks, and subsequently challenged them four days later with oxazolone or vehicle for ten consecutive days on the labia. We evaluated labiar sensitivity to touch, local mast cell accumulation, and hyperinnervation after ten challenges.

Results

Oxazolone-challenged mice developed significant tactile sensitivity that persisted for over three weeks after labiar allergen exposures ceased. Allergic sites were characterized by mast cell accumulation, sensory hyper-innervation and infiltration of regulatory CD4⁺CD25⁺FoxP3⁺ T cells as well as localized early increases in transcripts encoding Nerve Growth Factor and nerve-mast cell synapse marker Cell Adhesion Molecule 1. Local depletion of mast cells by intra-labiar administration of secretagogue compound 48/80 led to a reduction in both nerve density and tactile sensitivity.

Conclusions

Mast cells regulate allergy-provoked persistent sensitivity to touch. Mast cell-targeted therapeutic strategies may provide novel means to manage and limit chronic pain conditions associated with atopic disease.

Immune activation enhances epithelial nerve growth in provoked vestibulodynia

BACKGROUND

Provoked vestibulodynia manifests as allodynia of the vulvar vestibular mucosa. The exact mechanisms that result in altered pain sensation are unknown. Recently, we demonstrated the presence of secondary lymphoid tissue, which is the vestibule-associated lymphoid tissue in the vestibular mucosa, and showed that this tissue becomes activated in provoked vestibulodynia.

OBJECTIVE

The purpose of this study was to examine whether expression of intraepithelial nerve fibers and nerve growth factor are related to immune activation in provoked vestibulodynia.

STUDY DESIGN

Vestibular mucosal specimens were obtained from 27 patients with severe provoked vestibulodynia that was treated by vestibulectomy and from 15 control subjects. We used antibodies against the protein gene product 9.5, the neuron specific neurofilament, and nerve growth factor for immunohistochemistry to detect intraepithelial nerve fibers and nerve growth factor expressing immune cells in the vestibular mucosa. For intraepithelial nerve fibers, we determined their linear density (fiber counts per millimeter of the outer epithelial surface, protein gene product 9.5) or presence (neuron specific neurofilament). Nerve growth factor was analyzed by counting the staining-positive immune cells. Antibodies against CD20 (B lymphocytes) and CD3 (T lymphocytes) were used to identify and locate mucosal areas with increased density of lymphocytes and the presence of germinal centers (ie, signs of immune activation). B-cell activation index was used to describe the overall intensity of B-cell infiltration.

RESULTS

We found more protein gene product 9.5-positive intraepithelial fibers in vestibulodynia than in the control samples (6.3/mm [range, 0.0-15.8] vs 2.0/mm [range, 0.0-12.0]; P=.006). Neuron specific neurofilament -positive intraepithelial fibers were found in 17 of 27 vestibulodynia cases (63.0%) and in none of the control cases. Protein gene product 9.5-positive intraepithelial fibers were more common in samples with more pronounced immune activation. The density of these fibers was higher in samples with than without germinal centers (6.1/mm [range, 4.3-15.8] vs 3.0/mm [range, 0.0-13.4]; P=.020). A positive correlation between the fiber density and B-cell activation index score of the sample was found (Spearman's Rho, 0.400; P=.004; R²=0.128). No significant difference, however, was found in the density or presence of nerve fibers between samples with high and low T-cell densities. We identified areas of minor and major vestibular glands in 16 of the patient samples and in 1 control sample. Protein gene product 9.5-positive nerve fibers were found more often in glandular epithelium surrounded by B-cell infiltration than in glands without B cells (P=.013). Also, the presence of neuron specific neurofilament-positive fibers in glandular epithelium was associated with B-cell infiltrates (P=.053). Nerve growth factor-positive immune cells were more common in mucosal areas with than without B-cell infiltration and intraepithelial nerve fibers.

CONCLUSION

Excessive epithelial nerve growth in provoked vestibulodynia is associated with increased B-cell infiltration and the presence of germinal centers. This supports the fundamental role of immune activation in provoked vestibulodynia.

A Role for Bradykinin Signaling in Chronic Vulvar Pain

Chronic vulvar pain is alarmingly common in women of reproductive age and is often accompanied by psychological distress, sexual dysfunction, and a significant reduction in quality of life. Localized provoked vulvodynia (LPV) is associated with intense vulvar pain concentrated in the vulvar vestibule (area surrounding vaginal opening). To date, the origins of vulvodynia are poorly understood, and treatment for LPV manages pain symptoms, but does not resolve the root causes of disease. Until recently, no definitive disease mechanisms had been identified; our work indicates LPV has inflammatory origins, although additional studies are needed to understand LPV pain. Bradykinin signaling is one of the most potent inducers of inflammatory pain and is a candidate contributor to LPV. We report that bradykinin receptors are expressed at elevated levels in LPV patient versus healthy control vestibular fibroblasts, and patient vestibular fibroblasts produce elevated levels of proinflammatory mediators with bradykinin stimulation. Inhibiting expression of one or both bradykinin receptors significantly reduces proinflammatory mediator production. Finally, we determined that bradykinin activates nuclear factor (NF)κB signaling (a major inflammatory pathway), whereas inhibition of NFκB successfully ablates this response. These data suggest that therapeutic agents targeting bradykinin sensing and/or NFκB may represent new, more specific options for LPV therapy.

PERSPECTIVE

There is an unmet need for the development of more effective vulvodynia therapies. As we explore the mechanisms by which human vulvar fibroblasts respond to proinflammatory/propain stimuli, we move closer to understanding the origins of chronic vulvar pain and identifying new therapeutic targets, knowledge that could significantly improve patient care.

Vestibular Mast Cell Density in Vulvodynia: A Case-Controlled Study

OBJECTIVES

To identify whether mast cell densities in vulvar biopsies from the vestibule are associated with vulvodynia.

METHODS

We enrolled 100 women aged 19 to 59 years with confirmed vulvodynia cases, 100 racially matched controls, and 100 black control women. All had vulvar biopsies performed at the 7 o'clock position of the vestibule, which were then immunostained to detect c-KIT protein. The numbers of c-KIT positive mast cells per ×400 magnification field were manually counted, and t tests and logistic regression were used to assess the association with case-control status.

RESULTS

Of the biopsies, 235 were adequate samples for c-KIT testing for mast cells. The mast cell density was substantially lower in black control women (13.9 ± 10.9) in comparison to white control women (22.5 ± 13.2 p < 0.001): hence the analysis was confined to white cases and racially matched control women. Compared with racially matched controls, cases were younger, more likely to be married, and reported a higher household income. The average number of mast cells per ×400 magnification field overall was 19.1 ± 13.2 (range, 0-62). There was no difference in the mast cell count between racially matched cases (22.4 ± 13.9 per ×400 field) and controls (22.5 ± 13.2) in either the univariate or multivariable analyses. Within the group of cases, there was no difference in mast cell density based on the presence or absence of a variety of urogenital symptoms.

CONCLUSIONS

No difference in mast cell density in biopsies of the vestibule was found between white cases and racially matched controls. Black control women have a lower mast cell density compared with white control women.

A review of the available clinical therapies for vulvodynia management and new data implicating proinflammatory mediators in pain elicitation

Localised provoked vulvodynia (LPV) is a common, chronic, and disabling condition: patients experience profound pain and a diminished quality of life. The aetiologic origins of vulvodynia are poorly understood, yet recent evidence suggests a link to site-specific inflammatory responses. Fibroblasts isolated from the vestibule of LPV patients are sensitive to proinflammatory stimuli and copiously produce pain-associated proinflammatory mediators (IL-6 and PGE₂ ). Although LPV is a multifactorial disorder, understanding vulvar inflammation and targeting the inflammatory response should lead to treatment advances, especially for patients exhibiting signs of inflammation. NFκB (already targeted clinically) or other inflammatory components may be suitable therapeutic targets.

TWEETABLE ABSTRACT

Vulvodynia is a poorly understood, prevalent, and serious women's health issue requiring better understanding to improve therapy.

Familiality analysis of provoked vestibulodynia treated by vestibulectomy supports genetic predisposition

BACKGROUND

Provoked vestibulodynia is a poorly understood disease that affects 8-15% of women in their lifetime. There is significant inflammation and nerve growth in vestibular biopsies from affected women treated by vestibulectomy compared with matched female population controls without vestibulodynia. The triggers leading to this neurogenic inflammation are unknown, but they are likely multifactorial.

OBJECTIVE

Our objective was to determine whether vestibulodynia is more common in close and distantly related female relatives of women diagnosed with the disease and those specifically treated by vestibulectomy. Excess familial clustering would support a potential genetic predisposition for vestibulodynia and warrant further studies to isolate risk alleles.

STUDY DESIGN

Using population-based genealogy linked to University of Utah Hospital CPT coded data, we estimated the relative risk of vestibulectomy in female relatives of affected women. We also compared the average pairwise relatedness of cases to the expected relatedness of the population and identified high-disease-burden pedigrees.

RESULTS

A total of 183 potential vestibulectomy probands were identified using CPT codes. The relative risk of vestibulectomy was elevated in first-degree (20 [6.6-47], P < .00001), second-degree (4.5 [0.5-16], P = .07), and third-degree female relatives (3.4 [1.2-8.8], P = .03). Seventy of these 183 CPT-based probands had available clinical history to confirm a diagnosis of moderate to severe vestibulodynia. Notably, this smaller group of confirmed probands (n = 70) revealed a similar familiality in first-degree (54 [17.5-126], P < .00001), second-degree (19.7 [2.4-71], P = .005), and third-degree relatives (12 [3.3-31], P = .0004), despite less statistical power for analysis. Overall, the average pairwise relatedness of affected women was significantly higher than expected (P < .001) and a number of high-disease-burden Utah families were identified.

CONCLUSION

Our data suggest that vestibulodynia treated by vestibulectomy has a genetic predisposition. Future studies will identify candidate genes by linkage analysis in affected families and sequencing of distantly related probands.