Light-based Gene Therapy Cochlear Implants can Restore Hearing Loss
Researchers from University Medical Center (University of Göttingen) in Germany proved that a micro LED based cochlear implant is potentially better than the standard electrical cochlear implants to aid hearing impairment.
Cochlear implants are among the best bionic device available and are helping people to restore hearing since it was unveiled in the 1970. This technique acts as the “lost sound sensitive hair cells” and generates electric currents and stimulates the spiral ganglion neurons (SGNs). SGN’s are responsible for sending signals by activating the auditory pathway.
Figure 1. Mould of the human cochlea showing how tiny it is (Photo credit: Graeme Clark Foundation).
The standard procedure for the treatment of hearing loss from 1970 to now is generating electric currents. The electric current is generated by placing an electrode inside the cochlea.
Figure 2. Cochlear implant (Photo credit: Blausen.com staff. “Blausen gallery 2014”).
Cochlea is spiral-shaped cavity in the inner ear containing organ of Corti which generates nerve impulses in response to sound vibrations. A normal person without deafness can differentiate 2000 different types of vibrations and sound frequencies, whereas with electrical cochlear implants only two dozen of those frequencies are distinguished by deaf people. As a result of which the sound that is heard is distorted, subdued and muffled.
Figure 3. Multi-channel stimulation, or cochlear implant discovered by University of Melbourne research team (Photo credit: Graeme Clark Foundation).
Contrary to electricity, light do not spread through tissues making it easy to focus and create more channels thereby increasing the number of frequencies easily than current. This was proved by Tobias Moser and his team through experimental mouse model.
Moser and his team of researchers are trying to create 100 channels with micro light emitting devices (LEDs) as the optical source. The technique used is called optogenetic.
Optogenetic Approach Based Cochlear Implant
Prior to trying the optical approach, the animals were treated to 4 weeks of gene therapy, where the team inserted a gene by adeno-associated virus (AAV) to the mice and made the nerves sensitive to exposed light. After gene therapy, they exposed the experimental models to the optical source, which were the tiny LEDs. As a result, spiral ganglion neurons (SGNs) were activated which in turn activated the auditory pathway. Further, the team studied the spatial spread of cochlear excitation response of the experimental models to optical, acoustic, and electrical stimuli by recording local field potentials (LFPs). Final result obtained proved that optical stimulation proved to be better than the other two.
According to Martin Sumser at the Ludwig Maximilian University of Munich, Germany, some people would be willing to have gene therapy if it gave them more sensitive hearing. He said “There are plenty of people who are not happy with existing cochlear implants.”
Many similar optogenetic therapies are being tested for several other problems like blindness. Other alternative approaches to hearing aid are released in the market a year back which uses magnetic stimulation instead of electric. In 2015, Sophono was bought by Medtronic for an undisclosed amount, which develops magnetic hearing implant.
According to the researchers they are yet to determine the safety of this in human. Also they are trying to increase the LED staying power.
This video explains the mechanism of how a cochlear implant works (video credit: Advanced Bionics).
Credit: This news was first published on New Scientist.
Featured Image: 3D illustration of ear anatomy with music or sound coming. © goa novi (Stock Photo ID: 115123526)