Localized Provoked Vulvodynia-An Ignored Vulvar Pain Syndrome

The Involvement of Glutamate-mGluR5 Signaling in the Development of Vulvar Hypersensitivity

Provoked vulvodynia (PV) is the leading cause of vulvar pain and dyspareunia. The etiology of PV is multifactorial and remains poorly understood. PV is associated with a history of repeated vulvar inflammation and is often accompanied by sensory neuromodulation as a result of activation of the metabotropic glutamate receptor 5 (mGluR5) in the sensory nerve terminals. Therefore, this study aims to examine the role of glutamate-mGluR5 signaling during the initial inflammatory phase in chronic vulvar pain development in an animal model of PV.Thermal and mechanical vulvar sensitivity was assessed for three weeks following zymosan vulvar challenges. Anxiety-like behavior and locomotor activity were assessed at the end of the experiment. To investigate the role of glutamate mGluR5, the MTEP (mGluR5 antagonist) was injected into the vulva during vulvar inflammation. On the other hand, glutamate or CHPG (mGluR5 agonist) were injected in order to examine the effects of mGluR5 activation. RT-PCR was performed to assess changes in the transcription of genes related to neuroinflammation, neuromodulation, and neuroplasticity in the spinal cord (L6-S3). Zymosan-induced inflammation resulted in a significant thermal and mechanical vulvar hypersensitivity that persisted for over a month after the zymosan injection. However, local treatment with MTEP enhanced the vulvar mechanical and thermal hypersensitivity. On the other hand, activation of the mGluR5 via injection of glutamate or CHPG into the vulva leads to long-lasting vulvar mechanical and thermal hypersensitivity. The activation of the glutamate pathway was found to be accompanied by an increase in the transcription level of genes related to neuroinflammation and neuroplasticity in the sacral spine region. The present findings indicate that vulvar hypersensitivity is mediated by mGluR5 activation during inflammation. Hence, modulation of the mGluR5 pathway during the critical period of inflammation contributes to preventing chronic vulvar pain development. Conversely, activation of the mGluR5 pathway leads to long-lasting mechanical and thermal hypersensitivity.

Cytokine profiles and their roles in development of provoked vulvodynia

Provoked, localized, vulvodynia (PVD) is the main subtype of vulvodynia. Although the etiology of PVD is still a topic of debate, inflammation caused by cytokines responding to a dysregulated microbiome is one of the leading proposed theories. Therefore, the purpose of our study is to further explore the cytokine profiles in the study group with PVD using multiplex immunoassays based on electrochemiluminescence. We compared a panel of 26 distinct cytokines levels in the study group with PVD (n = 23) to the control group (n = 18) and cytokine concentrations were measured using MESO QuickPlex SQ 120 instrument with 5 different multiplex assays. Statistical analysis used the Mann-Whitney U test, two-sided p-values, and a significance level of α = 0.05. Differences in cytokine concentrations are described as negligible, small, medium, or large based on Cliff's δ. Concentrations of three cytokines were significantly lower in the PVD group: a large difference in IP-10 (p = 0.029*) and medium differences in IL-1RA4 (p = 0.030*) and IL-12 (p = 0.034*). One cytokine level was significantly higher in the PVD group: a medium difference for IL-6 (p = 0.037*). Due to the lack of consistency in elevation of inflammatory profiles, it is not enough to support persistent inflammation as the etiology behind PVD. However, these findings may indicate there is a possible immune response deficiency in some patients who have PVD. The resemblance of cytokine profile in our study to cytokine profile of people with chronic yeast infection further support this proposed mechanism behind PVD. Future studies involving history and testing for yeast infection are necessary to explore this possibility further.

Vestibulodynia: Clinical characteristics, first-line treatments, and factors associated with escalation of treatment with EMG-guided injections of botulinum toxin in a retrospective french cohort study

BACKGROUND

Vestibulodynia is a highly prevalent chronic pain disorder affecting the vulva having a major impact on women's physical, psychological, and sexual well-being. It remains an underrecognized disease that responds insufficiently to therapies such as physiotherapy and medication.

AIM

To assess the global efficacy of first-line therapies and factors associated with treatment escalation in women with vestibulodynia.

PATIENTS AND METHODS

This retrospective cohort study was conducted at the dermatology outpatient clinic of the University Hospital in Besancon (France) between 2013 and 2017 and follow-up until 2021.

RESULTS

Among 132 patients, the mean [standard deviation] age at diagnosis was 27.2 [±9.45] years, with an average duration of symptoms of 42.3 [±37.92] months. Most cases comprised provoked (75.0%) or secondary (72.7%) vestibulodynia. At least one comorbid pain or psychologic condition was identified respectively in 63 (47.7%) and 23 patients (54.5%). Vulvar hyperesthesia associated with pelvic floor muscle dysfunction was present in 121 patients (91.6%) and vulvar erethism was noted in 94 patients (71.2%). First-line treatments consisted of pelvic floor physiotherapy with biofeedback in 85% of patients, associated with amitriptyline in 36% of cases, and of additional lidocaine cream in 17%. Fifty-two patients (39%) presented at least a good response to first-line treatment, with only 21 (15%) being in complete remission, irrespective of therapeutic strategy (p = 0.25). Botulinum toxin injections were performed in 54 patients. Patients with either primary vestibulodynia (p = 0.04) or spontaneous vestibulodynia (p = 0.03) were more likely to receive this treatment.

CONCLUSION

Our study highlights the current lack of efficacy of first-line treatments in vestibulodynia. Considering the high prevalence of muscular dysfunction, botulinum toxin injections are of particular interest despite a lack of randomized controlled trials in this indication.

Changes in the Vaginal Microbiota of Women With Secondary Localized Provoked Vulvodynia

OBJECTIVE

The etiology of localized provoked vulvodynia (LPV) remains unknown, but observations suggest the involvement of the vaginal microbiota. We examined the vaginal microbiota of women with LPV and healthy controls, upon after a low-oxalate diet (LOD).

MATERIALS AND METHODS

A total of 9 women diagnosed with secondary LPV and 21 healthy controls were recruited from the Galilee Medical Center in Israel and subjected to prospective evaluations of their vaginal microbiota. Total DNA was extracted from vaginal discharge samples provided before and after following LOD for 3 weeks and was then subjected to 16S sequencing. Data obtained were then used to evaluate α and β diversity, identify differentially abundant bacterial taxa in LPV, and determine their impact on the metabolism.

RESULTS

These evaluations revealed decreased diversity in the vaginal microbiota of women with LPV and identified the Ochrobactrum genus and Pseudomonadaceae family as indicators for LPV. In addition, we identified 23 differentially expressed bacterial metabolic pathways between the LPV and control samples and revealed that LOD could induce changes in the β diversity of LPV vaginal microbiomes, which was further supported by some degree of pain reduction in patients.

CONCLUSIONS

Localized provoked vulvodynia and LOD were associated with shifts in the vaginal microbiota. However, the impact of these changes on the development of LPV requires additional studies with a larger cohort.

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.