We are developing a method to visualize functional hair cells and other cellular elements of the inner ear within the intact mammalian cochlea using fluorescence microendoscopy. Our laboratory has begun work on this minimally invasive in vivo imaging technique to provide high-resolution images of deep tissues previously inaccessible in live subjects. Using microendoscopes as small as 0.3 mm in diameter, we have successfully imaged individual red blood cells flowing within capillaries inside the mammalian cochlea. We are extending this work by labeling functional neural elements with fluorescent dyes to concurrently reveal mechanotransduction as well as microanatomy.

Current work includes microendoscopy using a styryl dye (FM-143) in the guinea pig. It is anticipated t hat this will allow us to accurately map hair cell injury following ototoxin exposure, and to observe the recovery of hair cells from temporary threshold shift noise damage. The use of microendoscopes should provide an opportunity to observe specific hair cell populations over time -- information previously unavailable through conventional techniques.

An imaging technology to observe functional hair cells and dendrites within live mammalian subjects will provide considerable benefit, and enable progress in a broad range of previously intractable hearing science questions. The success of inner ear microendoscopy will provide a basis on which inner ear surgery can be established. The inner ear is one of the last areas of the human body to remain largely inaccessible to direct examination and surgical intervention. This is because of the combination of its small size and its extraordinary fragility to mechanical manipulation. The development of non-destructive imaging techniques will enable diagnostic and therapeutic manipulations, including the optimal placement of cochlear implant arrays, or the specific delivery of stem cells or growth factors to enable hearing restoration.