Pelvic Pain and Endometriosis
Pelvic pain is a global health problem often linked to endometriosis and vulvodynia (chronic vulvar pain). Although common in women of reproductive age, pelvic pain is underreported, poorly understood, and difficult to manage. Worldwide, 13-32% of women of childbearing age (up to 600 million people) suffer from pelvic pain severe enough to routinely miss work or school. Furthermore, there is no guidance for the use of opioid therapy in gynecologic pain, and few alternatives exist.
Transient receptor potential (TRP) channels respond to a wide array of physical and chemical stimuli including temperature, pressure, and pH. Clinical trials have focused on inhibiting TRPV1, which has been implicated in chemotherapy induced peripheral neuropathy, diabetic neuropathy, cancer pain, chronic cough, endometriosis, arthritis pain, and migraine. TRPV1 is activated in response to noxious heat, protons, and capsaicin, the spicy component found in chili peppers. Paradoxically, capsaicin can exhibit analgesic properties, although the effects at most last months, depending on the application and dosage, and is accompanied by unpleasant side effects (e.g. stinging, burning). TRPV1 has been clearly implicated in endometriosis pain and lesion development. There also is evidence linking increased TRPV1 innervation to vulvodynia, and capsaicin has been used clinically to treat vulvodynia with some success. TRPV1 is expressed in other pelvic organs, such as the ovaries and has been implicated in bladder and bowel pain, which are often comorbid with gynecologic pain. We have strong supporting data that TRPV1 is involved in the vulvodynia mechanism and could represent a new therapeutic target for pelvic pain. We have already established that TRPV4, another member of the TRP vanilloid subfamily, is a key player in vulvar pain, and targeting it has therapeutic effects.
