Intracochlear Delivery of Newly Developed Gene Therapies for Preventing and Restoring Noise-Induced Hearing Loss via Novel Dual Lumen Microneedle Technology

Inner ear disorders, including hearing loss, tinnitus, and balance disorders, are common. According to a Centers for Disease Control and Prevention analysis, military personnel and Veterans are 30 percent more likely than non-Veterans to have severe hearing impairment due to noise exposure, often from gunfire, aircraft, tanks, heavy equipment, and roadside bombs. Untreated, hearing impairment can have widespread consequences on function, social integration, professional development, cognition, and quality of life. Common to all forms of traumatic injury to the inner ear is an inflammatory reaction to stress caused by reactive oxygen species (ROS) that is mainly produced by an inner ear-specific enzyme called NOX3. Animals devoid of NOX3 are protected against several forms of acquired hearing loss, such as age-related or toxin-induced hearing loss. Based on preliminary data, it is reasonable to assume that inhibiting NOX3 through innovative genetic therapies (silencing RNA and gene knock-down strategies) is a promising strategy to prevent hearing loss induced by noise exposure, even if given after the trauma. However, implementation of these therapies in humans is impeded by lack of an atraumatic means to introduce these precise molecular therapies into the inner ear. Protected by one of the hardest bones in body, the inner ear remains an extremely challenging target for delivery of therapeutic agents; some have proposed cochlear and vestibular fenestration to deliver gene therapy into the inner ear, but these approaches are associated with damage and hearing loss. Accessing the inner ear through its only membranous structure, the round window membrane (RWM), is an attractive portal for intracochlear access and delivery of biologic agents. However, simple diffusion of medications across the RWM is limited and precise dosing is impossible. Hollow microneedle technology offers an elegant solution to overcome this bottleneck by facilitating reliable and predictable intracochlear delivery across the RWM without anatomic or functional damage. Using microneedles, concentrations of therapeutic agents within the cochlea can be controlled with a precision that intratympanic injections simply cannot provide. We have developed novel ultra-sharp precision microneedles, polymeric and metallic, with significant freedom of design and potential biocompatibility. Using 2-Photon Polymerization (2PP), dual-lumen hollow needles that allow for simultaneous injection and aspiration of fluid can be fabricated. These needles will be tested for their ability to facilitate injection of large volumes into the cochlea, which may be necessary for effective treatment. We will assess the spatio-temporal distribution of therapeutics within the cochlea as this information is critical in designing patient-specific treatment strategies. The effect of these needles on RWM histology, healing, mechanical properties, and hearing will be assessed. The potential utility of hollow microneedles to safely and precisely inject RNA and gene therapies to silence NOX3 will be evaluated in an appropriate guinea pig animal model. The main outcome measure will be the preservation of the hearing function in treated vs. untreated noise-exposed animals. The proposed research combines atraumatic inner ear delivery through microneedles and NOX3-silencing for the common goal of preventing hearing loss after noise exposure, an important unmet clinical need. If successful, this project has the potential to transform the treatment of patients with noise-induced and other forms of acquired hearing loss. Microneedle and NOX3-silencing strategies working in concert may yield sufficient conceptual and practical power to open the door for a new era in inner ear medicine for civilians and military personnel, with patient-specific interventions in both clinical settings and remote and austere environments.