Investigating normal physiology and blast-induced damage of hair cells in a mature cochlea

Image shows stereocilia - hair cells in the cochlea.

Principle Investigator: Dr Andriy Kozlov
Department / Centre: Centre for Neurotechnology
Group / lab: Kozlov Lab
Funding Agency: U.S. Army

Project summary:

Among all injuries sustained during combat by active-duty military personnel in war zones, the traumatic brain injury (TBI) is considered the “signature wound” due to its prevalence. The leading cause of TBI is explosive blasts. The impact of TBI on hearing can be severe and extensive. It is estimated that more than half of all patients recovering from TBI develop tinnitus and auditory processing disorders. These forms of hearing impairment can have a dramatic effect on people’s lives: the reduced sense of awareness of our surroundings often leads to social isolation, causing depression and suicidal thoughts. As stated by American author and educator Helen Keller—she was both deaf and blind—: “Blindness cuts us off from things, but deafness cuts us off from people”. 

Our goal is to understand what parts of the auditory system are affected by explosive blast injuries, how they are affected, and to develop diagnostic measures and therapeutic interventions to prevent the development of auditory disorders as well as to enable treatment. We have several projects running in parallel in the lab (www.kozlovlab.com) to achieve this goal, focusing on both the peripheral and central auditory systems. The project funded by the US Army Research Office focuses specifically on the effects of explosive blasts on the cochlea.

The cornerstone of the auditory system is the sensory receptors located in the cochlea that convert sounds into electrical signals that are then processed by the brain. These receptors are called hair cells. They are arranged in rows along the cochlea (shown flattened in the figure below), which works as a biological frequency analyzer by distributing the energy of different sound frequencies onto different groups of hair cells.

Hair cells can detect vibrations at the atomic scale. However, their exquisite sensitivity makes them susceptible to mechanical trauma, which can contribute to noise-induced hearing loss. Extreme mechanical loading from exposure to loud sounds and explosive blasts can kill hair cells, and in humans they never regenerate. To develop rational and effective mitigation strategies to reduce injury caused by explosive blast and cure noise-induced hearing disorders, we must understand how hair-cell mechanotransduction and sound transmission, in mature hair cells, respond to mechanical trauma from loud sounds and blast wave exposure. In this effort, we investigate structural and functional molecular physiology of hair cells in the mature cochlea to identify cellular and molecular correlates of injury to mechano-electrical transduction and sound processing.