Regenerated auditory nerves after treatment (top) and untreated (below).
(Credit: UNSW Translational Neuroscience Facility)
Researchers at the University of New South Wales have, for the first time, used a cochlear implant to regrow auditory nerves and restore hearing in guinea pigs.
Cochlear implants help the deaf to hear artificially, but a new way to use the existing technology may show promise for one day restoring patients' natural hearing. By applying electrical impulses from a cochlear implant to administer gene therapy, a team of researchers at the University of New South Wales, led by PhD student Jeremy Pinyon and supervised by Professor Gary Housley, has regrown damaged auditory nerves in adult guinea pigs, an animal that has a similar auditory system to humans.
The team modified an existing cochlear implant to administer a type of therapy known as close-field electroporation (CFE) gene therapy. Electroporation involves administering electric pulses to a cell membrane to increase its permeability. This allows new gene constructs to be delivered to the membrane, which encourages growth.
When it comes to the cochlea, a family of proteins called neurotrophins can regenerate auditory nerve endings, but administering treatment — either by drug or viral-based gene therapy — is not safe. However, using the cochlear implant has allowed Professor Housley's team to administer the treatment in a safe, localised fashion.
The implant is modified with an electrode array that delivers the electrical pulses, stimulating an injected complementary DNA gene construct that encourages production of neurotrophins. After a few months, the neurotrophin production dropped, but the team believes that the changes in the auditory nerves may be maintained by the neural activity the implant generated.
"People with cochlear implants do well with understanding speech, but their perception of pitch can be poor, so they often miss out on the joy of music," Professor Housley said. "Ultimately, we hope that after further research, people who depend on cochlear implant devices will be able to enjoy a broader dynamic and tonal range of sound, which is particularly important for our sense of the auditory world around us and for music appreciation."
The team believes the technology may have implications for other kinds of implant therapy, too — deep brain stimulation to treat Parkinson's disease, for example.
"Our work has implications far beyond hearing disorders," co-author Associate Professor Matthias Klugmann, from the UNSW Translational Neuroscience Facility research team, said. "Gene therapy has been suggested as a treatment concept even for devastating neurological conditions and our technology provides a novel platform for safe and efficient gene transfer into tissues as delicate as the brain."
The full research was published today in the journal Science Translational Medicine.