Scientists have produced the cells that make up delicate inner ear hairs in mouse embryos, a step that could point the way to reversing hearing loss and curing congenital deafness. Sensory hair cells inside the cochlea, the auditory portion of the inner ear, convert sound waves into electrical impulses that are delivered to the brain. The loss of these minute hairs, or the nerves that control them, is the most common cause of hearing impairment and so-called nerve deafness [ABC Science].
Researchers used gene therapy to create the crucial cells: They used a virus to introduce a gene into the mice embryos, which caused non-sensory cells to turn into cochlear hair cells. While this preliminary experiment was done on normal-hearing mice, the discovery that the engineered cochlear cells functioned as well as natural cells was an important step. Says lead researcher John Brigande: “One approach to restore auditory function is to replace defective cells with healthy new cells…. Our work shows that it is possible to produce functional auditory hair cells in the mammalian cochlea” [Reuters].
Humans are born with about 30,000 inner ear hair cells, which are fairly fragile; loud noises can damage the hair cells and age can deplete them, resulting in hearing loss [ScienceNOW Daily News]. Humans, like other mammals, can’t regenerate these sensory cells naturally, so people who experience hearing loss try to get get around the problem in another way. Currently, people can have a cochlear implant which works by bypassing the damaged cochlear hair cells and stimulating the auditory nerve directly. An implant cannot restore hearing to normal but it does give the sensation of sounds [BBC News].
The new study, published in the journal Nature [subscription required], suggests that deafness could be entirely reversed by creating new cells. But researchers say the current study is only the first step in that direction. As for human tests, Dr Brigande says that the work is at too early a stage to say when they can start: “There is no present plan for tests in humans. The next step is to restore hearing in a deaf mouse [Telegraph].
Image: flickr/sutefani in orlando
August 28th, 2008 at 4:02 pm
This is great news for several years from now. My only concern is that when or if they’re able to perform this on humans they might not be able to help people who currently have cochlear implants because to get the electrodes on there they need to remove all of the existing hair cells and adhere the strip of electrodes. If they can only regrow so many or if removing the electrodes or initially removing the hair cells causes any sort of scar tissue it would be quite a hurdle in the least.
August 28th, 2008 at 4:41 pm
You have a knack for finding the cutest mouse photos.
October 1st, 2008 at 4:27 am
I’m hopeful this is the beginning of gene therapy on the Human ear. As a child I suffered from sudden deafness in my right ear. Diagnosed as damaged/depleted hair cells in the Cochlea, caused by a viral infection. A Cochlea implant in my case and others similar, (with one normal hearing ear, and one profoundly deaf), would be no good. As a Cochlea implant generates distorted sounds, which the Brain will have difficulty in recognising against the normal hearing ear. If, of course, both Cochlea’s were damaged, then Cochea implants would work, as the Brain can be re-tuned to the implants output, normalizing the sound. For the time being there is little that can be done for people like me, with a single non-hearing ear.