New research adds to our knowledge of the causes of deafness.
In 2010, a unique genetic mutation-known as SERPINB6-was first identified as causing hearing loss in humans, but until now, it was unclear what caused the hearing loss.
Researchers at the University of Melbourne and at Monash University have just discovered how hearing loss in humans is caused by that unique genetic mutation.
The study, published this week in the American Journal of Pathology, found this mutation induces malfunction of an inhibitor of an enzyme commonly found in our body that destroys proteins.
The defect is associated with progressive cellular degeneration within the cochlea. This begins with the hair cells, and then involves the primary auditory neurons, and, finally, the fibrotytes in the lateral wall.
The lead researcher, Dr. Tan, excited that the role of SERPINB6 as an inhibitor is now being ignored, is eager for what the discovery means for our hearing.
For the study, mice were genetically modified to carry the SEPINB6 mutation. The researchers found that upon hitting adolescence, the mice sensory hair cells in the inner ear began to degrade.
When the inner ears of these mice were examined under the microscope, a cluster of tiny, specialized cells called fibroocytes that are responsible for generating the power needed in the inner ear to detect sound also began to wear out and die.
Humans require the good cells in both ears to transform sound into electrical signals in our hearing nerve. It has been known for decades that mutations affecting the sensory hair cells cause hearing loss in humans but mutations affecting the fibrocytes remain uncommon.
The mice started to lose their hearing at three weeks of age, which is equivalent to teenage years in humans. Hearing loss continued to decline as the mice agreed, a trend that was also noted in humans.
Individuals who lack good copies of this gene were reported to lose their hearing from 20 years of age; however, most people show gradual signs of age-related hearing loss from 60 years of age onwards.
Mutations in SERPINB6 accelerate the hearing loss process.
The next step in the team's research will be to explore whether carriers of the SERPINB6 mutation can become deaf due to environmental influences, for example, through exposure to traumatic or loud noise which people are exposed to at music venues, festivals or even listening to MP3 players.
To test this hypothesis, Dr Tan's team will expose mice carrying the SERPINB6 gene to loud noise to see if this increases their susceptibility to hearing loss.
Deafness is extraordinarily complex genetically because there are literally hundreds of different genes that can be faulty to cause deafness.
Unfortunately, in the majority of individuals with deafness, doctors can not put a finger on the cause. It's actually the exception rather than the rule that doctors are able to establish the true cause let alone how to prevent or repair the damage.
Finding a way of introducing healthy copies of the gene could prevent the deafness ever occurring, which is much more likely to succeed than reversing problems that are already there.
Although that is believed to be quite a few years away, a vast amount of research is trying to develop that sort of technology.
To lose your hearing has a serious, significant impact on your social life, your family relations and your occupation or profession.
Concerned about your hearing health? Advances in technology and medical procedures provide a great many treatment options.