Our sense of hearing relies upon many factors within the ear, but none so much as the cochlea hair cells. Ears need inner and outer hair cells to create the electromotile responses needed to collect information from incoming sound to enable us to hear. Over time, age—mostly for those older than 60—and noise damage cause outer hair cell functioning to deteriorate. Specifically, the number of healthy outer hair cells that push against the tectoral membrane becomes smaller and smaller. It becomes more difficult to hear certain sounds or in certain situations.
Sounds, especially loud ones, produce pressure waves upon inner ear hair cells. A study by the National Institute on Deafness and Other Communication Disorders says nearly 26 million Americans suffer from hearing loss attributed to high levels of noise exposure. In the UK, more than 10 million people suffer from hearing impairment or deafness. Where age doesn’t play a factor, noise-induced hearing loss makes up a significant portion of the rest of the 10 million people.
With the development of gene therapy, I believe many individuals who lose hearing due to the damage or loss of hair cells might regain some hair cell functioning and reduce their hearing loss.
What is gene therapy?
Oxford University defines gene therapy as “the transplantation of normal genes into cells in place of missing or defective ones in order to correct genetic disorders.” Yet, this term encompasses a large scope. Stanford School of Medicine gives a bit more clarity to gene therapy as it relates to hearing loss: a focus on re-establishment of the three genes that cause hearing loss. Stem cell gene therapy treatments, specifically through the forced development of ATOH1, might supplement these three genes, however.
Other studies have shown that aiming at the supporting cells around the hair cells will also result in the restoration and help to prevent hearing loss. The gene therapy study report by Lisa L. Cunningham says that supporting cells “must survive in order to transduce sound.” In her study of heat shock proteins (HSPs), she found that HSP70 resisted hearing loss and hair cell loss. By regenerating the HSP70 through gene therapy, hair cells could have a slower rate of deterioration resulting in reduced hearing loss.
Does gene therapy restore hearing loss?
Gene therapy has shown positive results in field testing. Columbia University Medical Center conducted a study using mice with genetic mutations to their hearing. Development of cells and implementation of genetically developed cells in the mice resulted in the regeneration of a significant amount of hair cells. Mice share a similar genetic makeup with humans, so many audiologists and scientists predict that this might be the breakthrough genetic science needs to boost technology for preventing hearing loss.
The case of Robb Gerk offers additional evidence of gene therapy’s worth. Treated by Hinrich Staecker, Robb Gerk underwent gene therapy for a hearing loss condition caused by spinal meningitis. Gerk is the first person to undergo this gene therapy.
The process uses non-harmful viruses to stimulate hair cells in the ear. Definitive results aren’t available yet, but preliminary findings lean to the positive as Gerk reports better balance—a function fundamentally controlled by the hearing nerve—along with other subtle improvements.