How We Hear

Our ears detect the pitch and loudness of sound, they tune and filter – and they send all that information to the brain, which then interprets into sounds that you hear, recognize and understand.

Hearing is a complex process involving three parts of the ear – the outer, middle and inner.

Sounds exist as pressure waves moving through the air, and our ears are built to convert those waves into electrical signals.

The outer ear, shaped like a funnel, collects the sound waves from the air and moves them into the ear drum, where tiny bones in the middle ear (ossicles) vibrate, conducting sound into the inner ear.

Lost Sensory Hair Cells and Hearing

of all hearing loss is caused by damage to the inner ear, known as sensorineural hearing loss.

The Role of Hair Cells

The inner ear is full of fluid. When sound energy moves into the fluid of the inner ear (the cochlea), special cells that sense and perceive sound – hair cells – convert the energy from the vibrations into an electrical signal that travels up the nerve from the ear to the brain.

Hair cells are specially designed to convert sounds into electrical signals. At one end, they have little fibers that stick up (stereocilia). These fibers sit in the cochlear fluid and are sensitive to movement. The stereocilia move back and forth through the fluid, creating a chemical signal in the hair cell.

The bottom of the cell is connected to the brain by hearing nerve fibers, auditory neurons. Every time the stereocilia move, the hair cell initiates a nerve signal to the brain, which interprets the signal into sounds that we hear.

Because the human ear does not spontaneously restore lost or damaged hair cells, hearing loss is a permanent condition. Today, there are no FDA-approved therapeutic options to restore lost hair cells.

FX-322 is designed to treat the underlying cause of this type of hearing loss (sensorineural hearing loss) by regenerating hair cells through activation of progenitor cells already present in the cochlea.