Spinal neuronal activity and neuroinflammatory component in a mouse model of CFA-induced vestibulodynia.

Vestibulodynia is a complex pain disorder characterized by chronic discomfort in the vulvar region, often accompanied by tactile allodynia and spontaneous pain. In patients a depressive behaviour is also observed. In this study, we have used a model of vestibulodynia induced by complete Freund's adjuvant (CFA) focusing our investigation on the spinal cord neurons and microglia. We investigated tactile allodynia, spontaneous pain, and depressive-like behavior as key behavioral markers of vestibulodynia. In addition, we conducted in vivo electrophysiological recordings to provide, for the first time to our knowledge, the characterization of the spinal sacral neuronal activity in the L6-S1 dorsal horn of the spinal cord. Furthermore, we examined microglia activation in the L6-S1 dorsal horn using immunofluorescence, unveiling hypertrophic phenotypes indicative of neuroinflammation in the spinal cord. This represents a novel insight into the role of microglia in vestibulodynia pathology. To address the therapeutic aspect, we employed pharmacological interventions using GABApentin, amitriptyline, and PeaPol. Remarkably, all three drugs, also used in clinic, showed efficacy in alleviating tactile allodynia and depressive-like behavior. Concurrently, we also observed a normalization of the altered neuronal firing and a reduction of microglia hypertrophic phenotypes. In conclusion, our study provides a comprehensive understanding of the CFA-induced model of vestibulodynia, encompassing behavioral, neurophysiological and neuroinflammatory aspects. These data pave the way to investigate spinal cord first pain plasticity in vestibulodynia.

Reduced concentrations of vaginal metabolites involved in steroid hormone biosynthesis are associated with increased vulvar vestibular pain and vaginal muscle tenderness in provoked vestibulodynia: An exploratory metabolomics study.

Provoked vestibulodynia (PVD) is a chronic vulvar pain disorder characterized by hypersensitivity and severe pain with pressure localized to the vulvar vestibule. Knowledge regarding pathophysiological mechanisms contributing to the etiology and production of symptoms in PVD remains incomplete but is considered multifactorial. Using a cross-sectional observational study design, data from untargeted metabolomic profiling of vaginal fluid and plasma in women with PVD and healthy women was combined with pain testing and brain imaging in women with PVD to test the hypotheses that women with PVD compared to healthy women show differences in vaginal and plasma metabolites involved in steroid hormone biosynthesis. Steroid hormone metabolites showing group differences were correlated with vulvar vestibular pain and vaginal muscle tenderness and functional connectivity of brain regions involved in pain processing in women with PVD to provide insight into the functional mechanisms linked to the identified alterations. Sensitivity analyses were also performed to determine the impact of hormonal contraceptive use on the study findings. Women with PVD compared to healthy controls had significant reductions primarily in vaginal fluid concentrations of androgenic, pregnenolone and progestin metabolites involved in steroidogenesis, suggesting localized rather than systemic effects in vagina and vulvar vestibule. The observed reductions in androgenic metabolite levels showed large effect size associations with increased vulvar vestibular pain and vulvar muscle tenderness and decreases in androgenic and progestin metabolites were associated with decreased connectivity strength in primary sensorimotor cortices. Women with PVD showed symptom-associated reductions in vaginal fluid concentrations of metabolites involved in the biosynthesis of steroid hormones previously shown to affect the integrity of vulvar and vaginal tissue and nociceptive processing. Deficiency of certain steroids may be an important mechanism contributing to the pathophysiology of symptoms in PVD may provide potential diagnostic markers that could lead to new targets for therapeutic intervention.

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.

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.

Decreased concentration of protease inhibitors: possible contributors to allodynia and hyperalgesia in women with vestibulodynia.

OBJECTIVE: Women with vestibulodynia exhibit increased pain sensitivity to contact with the vaginal vestibule as well as with vaginal penetration. The mechanism(s) responsible for this effect remains incompletely defined. Based on reports of a possible role for proteases in induction of pain, we compared levels of proteases and protease inhibitors in vaginal secretions from women with vestibulodynia and controls. STUDY DESIGN: Vaginal secretions from 76 women with vestibulodynia and from 41 control women were assayed by an enzyme-linked immunosorbent assay for the protease inhibitors, secretory leukocyte protease inhibitor (SLPI) and human epididymis protein-4 (HE-4), and the proteases, kallikrein-5 and cathepsins B and S. Concentrations between subjects and controls were compared and levels related to clinical and demographic variables. RESULTS: Concentrations of HE-4 and SLPI were markedly reduced in vaginal samples from women with vestibulodynia compared with controls (P ≤ .006). All other compounds were similar in both groups. HE-4 (P = .0195) and SLPI (P = .0033) were lower in women with secondary, but not primary, vestibulodynia than in controls. Subjects who had constant vulvar pain had lower levels of HE-4 and SLPI than did healthy control women (P ≤ .006) or women who experienced vulvar pain only during sexual intercourse (P ≤ .0191). There were no associations between HE-4 or SLPI levels and event associated with symptom onset, duration of symptoms, age, number of lifetime sexual partners, or age at sex initiation. CONCLUSION: Insufficient vaginal protease inhibitor production may contribute to increased pain sensitivity in an undefined subset of women with secondary vestibulodynia who experience constant vulvar pain.

Dysregulation in Sphingolipid Signaling Pathways is Associated With Symptoms and Functional Connectivity of Pain Processing Brain Regions in Provoked Vestibulodynia.

Provoked vestibulodynia (PVD) is a chronic pain disorder characterized by local hypersensitivity and severe pain with pressure localized to the vulvar vestibule. Despite decades of study, the lack of identified biomarkers has slowed the development of effective therapies. The primary aim of this study was to use metabolomics to identify novel biochemical mechanisms in vagina and blood underlying brain biomarkers and symptoms in PVD, thereby closing this knowledge gap. Using a cross-sectional case-control observational study design, untargeted and unbiased metabolomic profiling of vaginal fluid and plasma was performed in women with PVD compared to healthy controls. In women with PVD, we also obtained assessments of vulvar pain, vestibular and vaginal muscle tenderness, and 24-hour symptom intensity alongside resting-state brain functional connectivity of brain regions involved in pain processing and modulation. Compared to healthy controls, women with PVD demonstrated differences primarily in vaginal (but not plasma) concentrations of metabolites of the sphingolipid signaling pathways, suggesting localized effects in vagina and vulvar vestibule rather than systemic effects. Our findings reveal that dysregulation of sphingolipid metabolism in PVD is associated with increased vulvar pain and muscle tenderness, sexual dysfunction, and decreased functional connectivity strength in pain processing/modulatory brain regions. This data collectively suggests that alterations in sphingolipid signaling pathways are likely an important molecular biomarker in PVD that could lead to new targets for therapeutic intervention. PERSPECTIVE: This manuscript presents the results of a robust, unbiased molecular assessment of plasma and vaginal fluid samples in women with provoked vestibulodynia compared to healthy controls. The findings suggest that alterations in sphingolipid signaling pathways are associated with symptoms and brain biomarkers and may be an important molecular marker that could provide new targets for therapeutic intervention.

Histologic and receptor analysis of primary and secondary vestibulodynia and controls: a prospective study.

OBJECTIVE: The objective of the study was to assess the association between hormone receptor densities, pain nerves, and inflammation in vestibulodynia patients. STUDY DESIGN: In a prospective study, tender and nontender biopsies from 10 primary and 10 secondary vestibulodynia patients were compared with biopsies in 4 nontender controls. Hormone receptors were evaluated using immunohistochemistry for estrogen receptor-alpha and -beta, androgen, and progesterone receptors. Inflammation, nerves, and mast cells were assessed histologically. Statistical analysis was by Fisher's exact test, analysis of variance, paired Student t test, and Wilcoxon rank test. RESULTS: Tender sites from primary vestibulodynia had increased nerve density compared with secondary and control biopsies (P = .01). Tender sites in secondary vestibulodynia had more lymphocytes than tender primary sites and control biopsies (P < .0001). Mast cells were increased in tender sites compared with nontender and controls. There were no differences in hormone receptor expression. CONCLUSION: Markers of inflammation differed between primary and secondary vestibulodynia and controls.

Cytokine profiles of women with vulvodynia: Identification of a panel of pro-inflammatory molecular targets.

OBJECTIVE: The vulvar pain syndrome (VPS) is a multifactorial disease severely influencing the lifestyle of affected women. Among possible etiological factors, local injury, peripheral and/or central sensitization of the nervous system, and a chronic inflammatory status have been positively associated with the development of VPS. The identification of a constitutive altered local inflammatory profile in VPS women may represent an important point in the characterization of patients' phenotype as a useful marker influencing the vulvar micro-environment. The aim of this study was to investigative the possible role of the local cytokines production in women with VPS in comparison to healthy women. STUDY DESIGN: In this study were collected vaginal swabs from 57 healthy women (HC) who never suffered from VPS and from 30 patients diagnosed with vulvodynia (VPS) by at least 3 years and currently symptomatic. All patients included in this study showed the absence of Sexually Transmitted (STD) diseases and Reproductive Tract Infection. Real-time PCR was performed to assess the genomic sequences of ST pathogens. The Luminex Bio-Plex platform was used for the analysis of a panel of 48 immune factors. RESULTS: Eleven molecules, specifically involved in the pro-inflammatory pathway were significantly modulated in VPS patients in comparison to healthy women, suggesting a persistent inflammatory process. CONCLUSIONS: Therefore, these inflammatory factors could be possible biological markers involved in this disease. Nevertheless, other studies are needed to consider this specific immune profile as a valid marker of the vulvodynia.

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.

Local and Systemic Inflammation in Localized, Provoked Vestibulodynia: A Systematic Review.

OBJECTIVE: To synthesize and critically evaluate all available evidence investigating whether localized, provoked vestibulodynia is associated with a specific inflammatory profile at both a local and a systemic level. DATA SOURCES: Comprehensive electronic searches were performed in MEDLINE, EMBASE, Scopus, PubMed, Web of Science, Cumulative Index to Nursing and Allied Health Literature, the Cochrane Collaboration databases, and ClinicalTrials.gov. The search strategy was developed using MeSH terms related to localized, provoked vestibulodynia, and inflammatory markers. METHODS OF STUDY SELECTION: Two independent investigators screened titles and abstracts and performed data extraction and risk of bias assessments. Studies were included if they reported at least one baseline inflammatory marker in women with localized, provoked vestibulodynia and compared them with healthy women. Reference lists from published reviews on localized, provoked vestibulodynia were screened for additional studies. TABULATION, INTEGRATION, AND RESULTS: There were 1,619 studies identified. Eighteen studies met the inclusion criteria, including 400 women with localized, provoked vestibulodynia and 212 healthy women in a control group. Risk of bias assessment revealed that the methodologic quality was generally low. Fifteen studies investigated local inflammation and three studies investigated systemic inflammation. On a local level, the number of mast cells expressed in vestibular tissues was greater in women with localized, provoked vestibulodynia expressed than in women in the control group. Several studies reported undefined inflammatory infiltrate in vestibular tissues to a greater level in women with localized, provoked vestibulodynia than in women in the control group. Systemically, levels of natural killer cells were lower in women with localized, provoked vestibulodynia than in women in the control group. There were no systemic differences in systemic interferon-α and interferon-υ levels between groups. CONCLUSION: There is limited and contradictory evidence regarding the characteristics of local and systemic inflammation in women with localized, provoked vestibulodynia.

Differences in primary compared with secondary vestibulodynia by immunohistochemistry.

OBJECTIVE: To assess whether primary and secondary vestibulodynia represent different pathologic pathways. METHODS: This was an analysis of archived vestibulectomy specimens from 88 premenopausal women with vestibulodynia (2002-2008). Patient records were reviewed to classify the type of vestibulodynia, duration of symptoms, and hormone status. Histologic sections were stained for hematoxylin and eosin to grade inflammation, S100 to highlight nerves, CD117 for mast cells, estrogen receptor α, and progesterone receptor. Differences between primary and secondary vestibulodynia were tested by t tests, chi-square analysis, and linear and logistic regression. RESULTS: Primary vestibulodynia showed significant neural hypertrophy and hyperplasia (P=.02, adjusted odds ratio [OR] 3.01, 95% confidence interval [CI] 1.2-7.6) and increased progesterone receptor nuclear immunostaining (P=.004, adjusted OR 3.94, CI 1.6-9.9) compared with secondary vestibulodynia. Estrogen receptor α expression was also greater in primary vestibulodynia when symptom diagnosis was less than 5 years (P=.004, adjusted OR 5.53 CI 1.71-17.91). CONCLUSION: Primary and secondary vestibulodynia have significantly different histologic features, suggesting that they may have separate mechanistic pathways. Clinically, this may mean the discovery of distinct conditions.