The electrical pulses used in cochlear implants could be part of the solution to curing a range of nervous system and brain illnesses, including Parkinson’s disease and depression, researchers at the University of New South Wales have discovered.
The findings are the result of five years of work by Professor Gary Housley and a team at UNSW, who were chasing one of the Holy Grails of medicine, gene therapy, which inserts DNA into cells to repair them.
In a major technological breakthrough, they were able to successfully regrow auditory nerves using the implant technique and believe the method may have wider applications.
The difficulty for researchers in gene therapy is penetrating the membrane which protects cells. Viral delivery has been a popular method in recent decades, but the search has been on to find a safe non-viral approach.
The researchers knew auditory nerve endings regenerate if neurotrophins – a naturally occurring family of proteins crucial for the development, function and survival of neurons – are delivered to the cochlea, in the inner ear, but until now, research had stalled because safe, localised delivery of the neurotrophins could not be achieved using drug delivery, or viral-based gene therapy.
Their experiments, involving guinea pigs, saw them develop a way of using electrical pulses from the cochlear implant to deliver the DNA to cells close to the array of implanted electrodes. These cells then produce neurotrophins.
Prof Housley, senior author of a research paper which details the breakthrough and is published today, April 24, in the journal Science Translational Medicine, said that it was the first time anyone had tried to use the cochlear implant for gene therapy.
“With our technique, the cochlear implant can be very effective for this,” he said. The benefit for the hearing-impaired is that while the implant is good for understanding speech, it’s less effective for music, so the improved connection via the regrowth of auditory nerves was vital.
“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,” Prof. Housley said.
The technique would be done during the existing implant surgery, adding only a few minutes to the operation. The surgeon would inject a DNA solution into the cochlea and then fire electrical impulses to trigger the DNA transfer once the implant is inserted.
The possibilities of this technique extend to other ‘bionic’ devices such as electrode arrays used in deep brain stimulation to treat Parkinson’s disease and depression and other complex neurological disorders.
Associate Professor Matthias Klugmann, from the UNSW Translational Neuroscience Facility research team and a co-author of the research said that because the technique used safe, existing technology to deliver gene therapy, clinical trials could begin within three years.
“Our work has implications far beyond hearing disorders,” Assoc Prof Klugmann 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 UNSW research has the support of Cochlear Ltd through an Australian Research Council Linkage Project grant.