Cochlear Implant Gene Therapy

Cover image expansionCochlear implants are among the most successful bionic devices ever developed. Available since the 1970s, they have restored some measure of hearing to more than 300,000 people around the world. Now, scientists from the University of New South Wales have found a way of making the implants even more effective—by turning them into delivery vehicles for genes that promote the growth of dying neurons in the ear. Their work appeared in Science Translational Medicine today (April 23).

Many people lose their hearing when the sound-sensitive hair cells in their cochleas die off. When this happens, the spiral ganglion neurons (SGNs), which send signals from the hair cells to the brain, also start to atrophy.  Cochlear implants stand in for the vanished hair cells and producing electric currents that stimulate the SGNs directly. But these shrunken neurons usually lie some distance away from the implants, on the other side of a bony wall. As a result, it takes strong currents to excite the cells, and they lose the ability to convey information about pitch. People who use cochlear implants can typically process speech, but their hearing falters in noisy environments and they rarely grasp the rich texture of music or tonal languages.

Jeremy Pinyon’s team has devised a solution. Before surgically adding a cochlear implant to guinea pigs, the scientists infused the surrounding cells with rings of DNA containing brain-derived neurotrophic factor (BDNF)—a gene that encourages neurons to grow. The implants then use small electrodes to deliver strong but brief electric bursts—just 1 pulse to 5 pulses, each 15 milliseconds long. These disrupt the membranes of nearby cells long enough for the DNA to enter. The cells express BDNF, and the once-atrophied SGNs grow toward them. “They pop out through little pores in the bone and migrate down very close to the electrodes,” said Gary Housley, who led the study. “That was really unexpected, but it helps a lot.”

Read the full article here.

© The UCLA Institute for Society and Genetics. All Rights Reserved.

X