1. “Hearing for those who have lost it” Flipping a Broken Switch?

2. Mechanics of Hearing The 1,000s of sensory receptors are made up of tiny hairs in the inner ear. Sound waves are amplified by the hairs, which vibrate when exposed to sound waves. The hair-vibration open ion channels (chemical channels) that let neurotransmitters flow in – triggering electrical activity in cochlear neurons. Electrical activity in the cochlea is passed on to the brain for processing.

3. The Procedure For volunteers who have lost their hearing through damage (constant exposure to high decibels) or disease. Injection of a virus containing a gene that should trigger the regrowth of sensory receptors in the ear. – The virus has been stripped of its DNA, which has been replaced with a gene that will hopefully trigger sensory receptor regrowth (has worked in mice).

4. Questions Why are they using an engineered virus carrying the gene that triggers hair growth? What happens once the virus is inside the inner ear? How does the gene work once it has been delivered?

5. Gene Incorporation The virus “injects” the gene into the genome of the cells that make the inner ear’s hairs. Once incorporated into the DNA of the cells, it throws a switch to restart the cells that control the growth of the hairs. The procedure has been performed successfully in mice and has been approved for trials in people who have lost their hearing. – Replaces cochlear implants.