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.

Background/Objectives: Localized provoked vulvodynia (LPV) is characterized by chronic vulvar pain upon light touch to the vestibule, a specialized ring of tissue immediately surrounding the vaginal opening. LPV affects about 14 million people in the US, yet the etiopathology of the disease is unknown. In LPV, the vestibule expresses elevated levels of the pro-nociceptive pro-inflammatory mediators prostaglandin E₂ (PGE2) and interleukin-6 (IL-6), which corresponds to lower pain thresholds. Previous studies have shown reduced amounts of arachidonic acid (AA)-derived pro-resolving lipid mediators in tissue biopsies from LPV patients that might impede the resolution of inflammation. AA is obtained from dietary linoleic acid, pointing to a defect in the metabolism of dietary polyunsaturated fatty acids in LPV. We aimed to further explore the involvement of AA metabolism in LPV, which appears dysregulated in the vestibule of LPV patients and culminates in chronic inflammation and chronic pain. Methods: Vestibular and vulvar tissue biopsies obtained from LPV and non-LPV patients were used to generate fibroblast strains and assessed for COX/LOX expression using qRT-PCR. Fibroblast strains were treated with inflammatory stimuli, and then COX-1 and COX-2 expression was assessed using Western blot analysis. Pro-inflammatory mediator production was assessed using enzyme-linked immunosorbent assays (ELISAs). ALOX5 and ALOX12 expression was assessed using qRT-PCR. Finally, lipidomic analysis was carried out to screen for 143 lipid metabolites following inflammatory challenge. Results: Tissue and fibroblasts from LPV patients exhibited altered expression of COX/LOX enzymes and production of AA-derived lipid mediators compared to non-LPV patients. Conclusions: Lipid profiles of tissue and vestibular fibroblasts from LPV patients differed from non-LPV patients, and this difference was attributed to differential COX/LOX expression and activity, which metabolizes AA derived from dietary linoleic acid. This dysregulation fosters chronic inflammation and reduced resolution capacity in LPV patients, causing chronic pain. While further work is needed, these findings suggest that dietary modifications could impact the LPV mechanism.