Photo of me by me.
“I hope that in five years, we are at a point that we can say that it is possible to cure deafness, at least in an animal.” Dr. Stefan heller. August 7, 2006
Stick your fingers in your ears. Both of them. Can you hear your cell phone ring? Is the guy on CNBC saying “vrumph, vrumph, vrumph?”
It’s called “hearing loss”.
I’ve had “fingers stuck in my ears” for years. And there are invisible fingers lusting for your ears too. About 10% of the population has hearing problems. If you stick around long enough, it’ll probably happen to you. More than half of “seniors” are affected by this annoying and, often, disabling thing.
HAIR CELLS AND HEARING
If the gills of our swimming ancestors hadn’t evolved into the ears of homo sapiens, we wouldn’t have developed speech. No point in talking if you can’t hear the words. And, without speech, we humans could still stand up straight and could still throw rocks. But it wouldn’t be quite the same, would it? So imagine how disappointing it is to discover that our wonderful and much taken for granted ears wear out! In fact, they are SO delicate! A good thumping beat at a high volume slowly and inexorably grinds up our gears. It’s like your mother said, “Turn down the damn VOLUME before we BOTH go deaf!”
You may remember from biology class, that the ear has a cochlea that looks like the spirals of a sea shell. Inside this cochlea are hair cells (“stereocillia”) on a membrane. They’re made of actin, the same stuff that makes mucles flex. When sound waves wash over the hair cells, they’re bent back and forth, converting mechanical motion into electrical signals for the nervous system.
This structure, the cochlea, tantalizes researchers. Obviously, this is where the action is. But, because of its location in the body, it’s hard to study. The size of the hair cells, a few hundredths of a millimeter in width, doesn’t help much either. But it is these delicate cells that are complicit in the most common type of deafness: age-related hearing loss (presbycusis). Once damaged, they’re gone forever. It’s this sad fact that explains why most of us adults are slowly, slowly losing our high frequency hearing. Or worse.
Image is from 29th edition, Gray’s Anatomy via Wikipedia Commons and, ultimately, from Wikipedia article on the inner ear.
FIXING THE PROBLEM
In the modern era, some hearing problems can be addressed with surgery or by removing impacted ear wax. Leaches, ear candling, aldosteron, B12, folic acid, and hypnosis are all in there somewhere too. But there doesn’t seem to be much you can do about the slow drip-drip-drip of age-related hearing loss except go find yourself a hearing aid (see rant below).
HOWEVER, in the 1980′s, it was discovered that hair cells in the ears of birds DO regenerate. Sensational news!
As the scientific world discovered the potential of stem cells which can differentiate into all kinds of things, researchers, such as Stefan Heller of Stanford University, began to look for connections. In 2002, Dr. Heller, then at Harvard, discovered that stem cells are present in the inner ear of human beings, suggesting that there’s a latent potential for regeneration of hair cells. One of his goals is to develop a drug that can be introduced into the ear as an ear drop.
I don’t mind admitting that he’s one of my heroes. In this video, he describes what he’s up to.
THE AUDACITY OF HOPE
Headlines can be heartbreakers. I like science. Why ELSE would I write about it? But headlines like Cell Transplants May Cure Deafness and Cultivated Ear Cells May Lead To Cure For Deafness raise hopes only to crush them again under the cruel heel of “maybe” and “someday”. These breakthroughs ARE important steps and MAY lead to a cure. But, not to be cynical, they’re more likely to lead to another round of grants for the lab. I guess that’s a TERRIBLE way to introduce this section because there IS a lot of great science being done:
The role of neurotrophins, chemicals that bathe the auditory nerve, is being worked out by Robin Davis, Professor of Cell Biology and Neuroscience, Rutgers.
Dr. Karen Avraham, Department of Human Molecular Genetics, Sackler School of Medicine, Tel Aviv University, has shown that “microRNAs” can be responsible for hair cell death. Link. If I understand this right, it’s an exciting insight for people who’s hearing starts to go at a younger age. The therapy would involved inserting microRNAs directly. Science now. Medicine later. Maybe.
Hair cells are kept “tuned up” by certain proteins. Knowing how this happens seems to be another important step in understanding what can go wrong. Very interesting and very basic.
Helge Rask-Anderson, Professor of Experimental Otology, Uppsala University, is studying growth of stem cells and trying to find ways to coax them into the right places with electromagnetic fields. Cool!
Marcelo Rivolta of the University of Sheffield is working with human ear cells created in the lab with foetal cells.
Work in Itay with stem cells from human umbilical cored blood. Link.
HEARING AIDS – A RANT
What’s wrong with hearing aids? Don’t get me started!
WHAT a disconnect between the wearer, often elderly or very young, and a device which is easily damaged and high maintenance! Good ones are expensive, rarely covered by medical plans, and are often uncomfortable. And you gotta be SO good to use these things right. Choosing the right one, inserting it right, maintaining it, keeping it free of wax and knowing what to do under which conditions, dealing with telecoils and various “program settings”, manipulating tiny controls in crazy places. This is hard stuff. And I’m a Biomedical Engineer! No wonder so many hearing aid users give up.
Knowing when they’re on the fritz and need a trip to the audiologist might SEEM like the easy part. But it isn’t. The changes in hearing may be gradual and hearing isn’t as obvious as sight. Maybe your spouse is mumbling.And getting caught in the rain or forgetting to remove them before showering can destroy an investment of thousands of dollars.
Even IF your’re really good at all this stuff, hearing aids just don’t bring you all the way back. Not even the best of them. It ain’t like the old days. The High Fi’s gone.
But they help. And I don’t mean to be ungracious.