As life expectancy increases, the burden of degenerative diseases is growing. Sensorineural hearing loss is nearly epidemic in proportions, affecting one third of individuals over the age of 65 years and 278 million people worldwide.
- Given its prevalence, it is one of the most common neurodegenerative disorders in humans.
- In over 80% of cases, the cause of hearing loss is degeneration and death of inner ear hair cells.
- Developing effective means of preventing neurodegeneration and of treating it when it does occur is a major challenge.
- Previous studies provide snapshots of the cellular degeneration at individual time points using different cohorts of animals, but lack the ability to directly visualize cellular processes in vivo due to the cochlea’s inaccessibility.
- The cochlea is encased deep within the temporal bone and opening the hard dense cochlear capsule requires considerable force, often leading to damage of the fragile inner ear structures. Thus, a major limitation to the present technology is the inability to study inner ear cellular pathways and degeneration in vivo.
- Because of these difficulties, most studies use immature in vitro preparations to study function or obtain single time point histological data coupled with gross functional assays like distortion products or auditory brainstem responses, post treatment.
- Our approach: Micro-endoscopy using gradient refractive index optics (GRIN) offers a new approach to overcome this challenge. GRIN micro-endoscopy is an emerging imaging modality that provides micron-scale optical resolution in tissues inaccessible to standard light microscopy.
Cochlear GRIN micro-endoscopy will be used to monitor inner ear treatment interventions such as drug or gene-induced regeneration, viral transfection of remaining supporting cells, or stem cell transplantation studies where individual cells can be visualized. Complete hearing preservation would establish in vivo cochlear micro-endoscopy as a potential intervention in human otologic disease.
For example, optical micro-endoscopy imaging may be carried out to better define the cause of sudden sensorineural hearing loss, better define Meniere’s disease (endolymphatic hydrops) or for evaluating cochlear anatomy prior to cochlear implantation in difficult patients (abnormal development of the cochlea).