Identification of Age and Injury Dependent Mechanisms of Elastic Fiber Dynamics in the Murine Vagina

Project Summary The average age of first-time mothers in the United States is increasing, and this delay can have deleterious effects on maternal health since pregnancies after the age of 35 have a 350% greater risk of obstetric injury. Furthermore, maternal age at the time of delivery is associated with increased risk of pelvic organ prolapse (POP) which is defined by the abnormal descent of the female pelvic organs due to impaired structural integrity of the pelvic floor and vagina. Treatment for POP typically involves surgery to restore normal anatomy, however one-in-three POP reconstructive surgeries will fail because they utilize native tissue that is degraded due to age or injury. While age and vaginal parity are leading risk factors for POP, the fundamental mechanisms linking age, injury, and postpartum healing to pelvic floor stability remains unknown. This lack of mechanistic understanding has slowed the development of effective non-surgical therapies for treating conditions of the pelvic floor. Towards this end, our data shows that vaginal compliance and contractility decrease with age in non-pregnant mice as a result of compromised elastic fiber functionality. We have also shown that surgical injury exacerbates disruption of the vaginal elastic fiber network, which in turn contributes to impaired vaginal wound healing. Taken together, these observations suggest functional elastic fibers are important for preserving vaginal integrity and postpartum healing potential with age and injury and may be an important biological target for improving pelvic floor stability. This led us to explore potential therapeutic approaches to induce elastic fiber synthesis. To this end, the anti- hypertensive drug minoxidil has shown beneficial effects on elastin production in blood vessels but had not been investigated in pelvic floor tissues; our initial observations suggest minoxidil induces both ex vivo elastin synthesis in cultured murine vaginal explants and in vivo vaginal elastic fiber deposition following local injections. Given these promising findings, and the importance of elastic fibers in vaginal stability, the current proposal will 1) determine which vaginal cells produce elastin during postpartum healing and if production is constrained by age or injury, 2) demonstrate the spatiotemporal dynamics of functional elastic fibers with and without vaginal injury, and 3) evaluate the efficacy of minoxidil to ameliorate deleterious changes in the vaginal wall with age and injury. In Aim 1 we will determine injury-dependent mechanisms of elastic fiber dynamics in the murine vaginal fibromuscular layer, and in Aim 2 we will elucidate if age is a key determinant of functional elastic fiber dynamics and vaginal healing potential. We expect to demonstrate that elastic fibers are produced by fibroblast- like cells and that age and injury decrease functional elastic fiber production. We also expect to reveal minoxidil’s ability to generate de novo functional elastic fibers and improve healing potential after treatment as a result of increased biomechanical stability. This work will evaluate a first-of-its-kind minimally invasive biological treatment to prevent or halt deleterious elastic fiber remodeling of the murine vaginal fibromuscular layer. We expect these results will be applicable for the treatment, or even prevention, of pathologies such as POP and vaginal atrophy.