Tissue-Engineered Cochlear Fibrosis Model Links Complex Impedance to Fibrosis Formation for Cochlear Implant Patients.

Cochlear implants are a life-changing technology for those with severe sensorineural hearing loss, partially restoring hearing through direct electrical stimulation of the auditory nerve. However, they are known to elicit an immune response resulting in fibrotic tissue formation in the cochlea which is linked to residual hearing loss and suboptimal outcomes. Intracochlear fibrosis is difficult to track without post-mortem histology, and no specific electrical marker for fibrosis exists. In this study, we developed a tissue-engineered model of cochlear fibrosis following implant placement to examine the electrical characteristics associated with fibrotic tissue formation around electrodes. We characterized the model using electrochemical impedance spectroscopy and found an increase in the resistance and a decrease in capacitance of the tissue using a representative circuit. This result informed a new marker of fibrosis progression over time that is extractable from voltage waveform responses, which can be directly measured in cochlear implant patients. This marker was tested in a small sample size of recently implanted cochlear implant patients, showing a significant increase over two post-operative timepoints. Using this system, we demonstrated complex impedance as a marker of fibrosis progression that is directly measurable from cochlear implants to enable real-time tracking of fibrosis formation in patients, creating opportunities for earlier treatment intervention to improve cochlear implant efficacy. This article is protected by copyright. All rights reserved.