Cochlear Implant Plus Gene Therapy Could Restore Hearing to the Deaf

By Breanna Draxler | April 23, 2014 1:38 pm

cochlear-implantCochlear implants have restored hearing to many deaf people, but they haven’t advanced much since they were unveiled in the 1970s. That may be set to change with an exciting new advance, not in the technology of the device itself, but rather in using gene therapy to increase the device’s effectiveness. Today researchers announced that they’ve been able to restore tonal hearing in guinea pigs with the new method of gene delivery.

Cochlear Implants, Then and Now

Cochlear implants, or “bionic ears,” work by stimulating the auditory nerve to restore a rudimentary kind of hearing. This works pretty well, but the gap between the electrodes and the degenerating nerve is pretty big, which makes communication difficult. And even the state-of-the-art implants only have 22 electrodes, enabling them to hear 22 different tones. They can’t, for example, distinguish between the soft buzz of a clarinet and the shrill sound of a flute.

Teams of researchers have tried to improve upon the implants over the last decade by trying to focus the electrical currents more narrowly, to stimulate a smaller, more pitch-specific area of the nerve, or to use drugs that improve the communication between the electrodes and the neurons. But this new method, reported today in Science Translational Medicine, has a distinct advantage: it actually encouraged the regrowth of the auditory nerve. This decreased the gap between the nerve and the cochlear implant, and improved communication between the two.

Image credit: Science Translational Medicine

Image credit: Science Translational Medicine

Bionic Guinea Pigs

The team implanted “bionic ears” in deaf guinea pigs, whose auditory systems are very similar to humans’. With the device, then, they delivered DNA that coded for a protein called brain-derived neruotrophic factor (BDNF), which encourages nerves to grow. The DNA was taken up by cells in the cochlea and, after two weeks, the nerves had grown significantly toward the electrodes. When the guinea pigs’ hearing was tested they found that animals that were once completely deaf had their hearing restored to almost normal levels.

It’s unclear, however, whether the treatment will work long-term: neuron production in the guinea pigs dropped off six weeks after the gene therapy. Researchers are also unsure whether tones heard after this treatment accurately reflect how they sound with normal hearing.

The technique is very close to being ready for human trials, where some of these questions should be answered. If it proves successful in clinical trials, the technique of combining gene therapy with device could also be used for other implants like retinal prosthesis and deep brain stimulation.

Top image credit: Elizabeth Hoffmann/Shutterstock

CATEGORIZED UNDER: Health & Medicine, top posts
  • Alberto Cano

    I often here deaf people talk about “deaf culture”…like it’s some sort of..splinter section of humanity, meaning they are somehow proud or glad to be that way…how do this people feel when the prospect stands on deafness being eliminated in the very near future?

    • Bearpants42

      They’re not fans of the idea.

      • Alberto Cano

        Evidently from the responses here….Logic would dictate that having a disadvantage would not be something desirable to bestow to your children…nor having a disability should be considered something to be proud of if a solution is readily available…

        • sam

          I think the real problem is that to you, it seems appropriate to tell people what part of themselves they should or should not be proud of.

          Deaf people have made friends who they never would have met if they didn’t have this on common. They’ve shared experiences with each other and formed a bond that we now recognize as a culture. Many of my Deaf friends see “hearing” people as the ones at a disadvantage, because they are too close-minded to understand that other ways of life could be just as fulfilling.

    • jon

      Deafness will not be eliminated in the near future. It is not a splinter section of humanity, it is a culture like any other, based on a shared language and customs. But if two deaf people whose first language is sign language have a deaf child, which happens often, they will want to speak to that child in their native language and communicate naturally to that child.

    • Morgan Soja

      It’s really important to remember that choosing a cochlear implant, or choosing a specific treatment is a CHOICE, not a requirement. And there will always be reasons why someone may not be a good candidate for a certain therapy or procedure. There are also people who are very proud to be Deaf, and feel (rightly) that they are fine just the way they are. It’s also important to note that many, MANY therapies and treatments are costly. Cochlear Implants cost an average of $40,000. . . which makes it prohibitive for many people.

  • jon

    A lot of this information regarding cochlear implants is radically inaccurate. From the first paragraph, the fact that they can only hear 22 tones is wrong. CIs have somewhere between 22-28 electrodes, but the 8 electrodes representing the auditory filters with the greatest acoustic energy for each sound stimulus are activated for each sound. This means that the different combinations of 8 electrodes fire for every sound, like a chord on a piano or a guitar. This leads to many more than 22 tones available. Only 4 electrodes, or channels, are needed for speech recognition, 16 channels needed for melody recognition. Music perception is a problem due to the difficulty in low frequency perception. Someone should fact-check this info. I do not know as much about the cell/ genetic biology aspect of this, but I’m already suspicious.

    • David Landsberger

      It ia true that CI users can hear more than 22 tones. However, it is worth noting that the maximum number of intracochlear electrodes in an FDA approved CI is 22 (I.e. the Cochlear Nucleus system). Advanced Bionics uses 16 intracochlear electrodes and Med-El uses 12. I suspect you may be thinking of the ACE strategy in Nucleus devices in which on every pass, only a subset of the electrodes (typically about 8) stimulate.

      Now having said this, it is wrong to think that CI users can only hear a maximum if 22 pitches. For example, when two adjacent electrodes are stimulated, the perceived pitch is in between the percept of each electrode alone. Furthermore, pitch can also be coded via temporal coding which is not restricted by the number of electrodes.

      Please forgive the typing as I am writing this on a bouncing bus using my phone.

  • 18235

    deafness, like being blind, isolates a person from rest of humanity…so, hopefully, this implant will work.

  • Fred Van Leuven

    Most interesting scientific/medical approach & hope-giving for deaf people. Equally interesting discussion and added info (and not all of it is radically inaccurate …) while I recognize all too well the technical Qs and “social” remarks.

    We have no family-history of deafness, but my god-child, now 21, was born deaf as 3rd & youngest daughter of my youngest brother. She received her first cochlear implant (CI) when she was 2, the 2nd at the opposite side at 10, while the first was replaced with a modern CI only 2 years ago. She is in her last year bachelor in applied psychology and does very well both in studies as socially, while speaking fluent an “nearly normal” flemish, and of course sign language with sign-spelling as add-on.

    Her boy-friend is deaf with no CI and “speaks” only sign language – the flemish dialect that is ! They plan eventually 4 children (but so did my wife and I when we were young – and we stopped with 2).

    That is the context to show that I know what is at stake here !

    Deaf people have their own culture and language (and ‘dialects’ abound!). They prefer to hang out with their equals for that reason – the same as why neuroscientists (like me), soccer-fans, startrek-nerds and beatle-maniacs huddle together (per category – of course !).

    I have great difficulty to carry a “normal” conversation with them, and when they converse (smoothly and rapidly) with each other, with their parents and friends, I feel largely excluded because I fail to understand details – let alone “subtilities” and jokes …
    We see each other not that often, as we are all quite busy professionally and socially, and we live at “opposite ends of Flanders” (car traffic thru Brussels is “hell”). So we converse mainly by e-mail and SMS, which is fine but “not the real thing”.

    We definitely hope that combining CI with any form of biomedical engineering, be it gene-therapy with BDNF or any other (growth) factor, or (stem)cell-therapy will solve the evident problems of deaf people.
    In the mean time – and even then – I realise as a neuroscientist that this can/will never be a complete cure and I accept, and even appreciate that they have their own social circles, with preferred (inter)actions and partners – even if that “excludes us normal hearing people”.

    Fred Van Leuven, emeritus professor at KULeuven,


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