IRA FLATOW, host.
You're listening to Science Friday on NPR News. I'm Ira Flatow. Up first this hour, your body's own built-in mechanism to protect your ears from loud noises. This week, a group of researchers working with mice report that they have figured out a way to protect mouse ears from the damage caused by high volumes, loud noises. Reporting in the journal Public Library of Science Biology, the scientists say, a single genetic change in a protein gave mutant mice - these are mice with the altered protein - a kind of ear protection. They were better able to withstand high volumes without incurring the cell damage, you know, that can come with loud noises.
Now, we humans have that same protein in our ears, so does this mean that protein protection from hearing loss may one day be available to us? Hmm. Joining me now to talk more about it is my guest Paul Fuchs, professor of otolaryngology. I love the excuse to say that term.
(Soundbite of laughter)
FLATOW: And co-director of the Center for Sensory Biology at Johns Hopkins University Institute for Basic Biomedical Science. Welcome to Science Friday, Dr. Fuchs.
Dr. PAUL FUCHS (Professor, Otolaryngology; Co-Director, Center for Sensory Biology, Johns Hopkins University): Thank you, Ira. I'm pleased to be here and have a chance to talk about our work.
FLATOW: You're welcome. Let's talk about the ear first. What happens in the ear from a loud noise when it gets damaged?
Dr. FUCHS: Well, there's lots of things that happen. Eventually, the sensory receptor cells - they're called hair cells - die. And these are cells which are not replaced, and so once they're gone, that's it. We've lost the capacity to hear from those cells.
FLATOW: Mm hmm. And working with mice, their ears work the same way?
Dr. FUCHS: That's correct. Yeah, all the general features of a mouse ear and a human ear are pretty much the same. So, it's quite useful to look at molecular mechanisms in that species.
FLATOW: So, you found, in your research with the mice, sort of an ear protector? Would that be correct?
Dr. FUCHS: Yeah. Well, this has been known for a long time. We know that there's a population of neurons in the brain that project out to the ear. They're kind of analogous to motor neurons that innervate muscle, if you will. And their role in projecting out to the ear is to turn the ear off. And they do that by contacting the sensory receptor cells directly and turning them off.
FLATOW: So that when a loud noise comes by and shocks the hair cells, they don't get damaged?
Dr. FUCHS: Well, that's right. So...
Dr. FUCHS: A reflex, basically, that helps us to protect the ear from loud sound.
FLATOW: And why do we have this and how come some of us get damaged? Why isn't that mechanism working?
Dr. FUCHS: Well, you know, it doesn't work perfectly. It's not enough to completely protect us from the sorts of very loud sounds that some of us are exposed to, both in the workplace and recreationally. So, even though we have this, it's not enough, basically. It can help, but it can't do the whole job.
FLATOW: So, you tried to do that job in the mice?
Dr. FUCHS: We tried to make them better by changing the characteristics of the molecular receptor, the protein that's actually responsible for mediating this feedback effect.
FLATOW: And tell us what happened.
Dr. FUCHS: Well, the prediction was is that this protein should work better. So, we first asked if that was true, and we looked at, in fact, the effects within the in the inner ear itself, saw that that did work as we predicted. And then these animals had somewhat less sensitivity to sound normally because they had a stronger feedback effect from the brain. And then, when they were exposed to very loud sound for a number of hours, their counterparts that didn't have this genetic change experienced a certain level of hearing loss. But, the mutated mice - the ones that we generated with this change in the receptor - those animals experienced less hearing loss. So, they were better protected from the trauma of that loud sound.
FLATOW: How were you able to change that receptor?
Dr. FUCHS: There's a process in which one does transgenesis.
FLATOW: Mm hmm.
Dr. FUCHS: You make a mutated form of the gene itself and then incorporate that into a mouse. And so, transgenic mouse technology is something that's been around now for a quite a while and has really made incredible kinds of experiments possible in which one can look at molecular mechanisms by these very specific kinds of changes.
FLATOW: Now, let me make the jump that I know I shouldn't make.
Dr. FUCHS: OK.
FLATOW: To people.
Dr. FUCHS: Yeah.
FLATOW: Are we - is there any possibility we could create, not transgenic people, but some sort of treatment to be used in…
Dr. FUCHS: Yeah, so that's why we're particularly interested in the way we did this experiment, because what we did was to make a change in this receptor, which we can actually mimic with some kinds of drugs. So, by showing that this effect was beneficial in an animal model, then that gives more motivation to look for drugs which could produce that same change. We know about some already, but they actually are ones that would have kind of widespread effects throughout the body. So, now we need to look a little more carefully and find things which would potentially act specifically within the ear to have a similar kind of helpful effect.
FLATOW: Now, as someone who thinks like an engineer sometimes, I know there's always a tradeoff.
Dr. FUCHS: Mm hmm.
FLATOW: I mean, if you make the hair cells stronger to withstand the shock of a sound, do you make them less sensitive to more sensitive noises?
Dr. FUCHS: That's exactly right. So, in fact our transgenic mice - the ones that we made with the mutated protein - were less sensitive to low-level sounds than their normal counterparts. So, they kind of had, you know, inhibition of the ear ongoing all the time.
FLATOW: Mm hmm. So...
Dr. FUCHS: So, that's not such a great thing.
FLATOW: No. So, if you want to hear fine music - fine classical music then - with all those nuances - you're not going to be able to hear it?
Dr. FUCHS: Well, that's right.
FLATOW: As well.
Dr. FUCHS: Or least very, very quite sounds. So, the advantage, though, of having perhaps a drug that one could take is that you wouldn't have to exposed to this change all the time but rather could perhaps take it prophylactically, if you knew that you were going to be in a circumstance of unavoidable loud sound.
FLATOW: Mm hmm. Sort of a rock concert or something?
Dr. FUCHS: Yeah, or your workplace or in...
FLATOW: Or your workplace.
Dr. FUCHS: The armed forces. You know, these are all situations where there's lot of damaging levels of sound, and sometimes you just can't avoid them.
FLATOW: Now, people who have hearing damage - and I do have; I have some percussion damage from a bad "Newton's Apple" demonstration with a firecracker many years ago.
(Soundbite of laughter)
FLATOW: I have tinnitus; I have ringing in my ear - in one of my ears.
Dr. FUCHS: Oh, yeah.
FLATOW: Is there any hope for curing something like that with your research?
Dr. FUCHS: Well, this is a really huge problem. Tinnitus afflicts many, many people. It can be really debilitating in some cases. It's very common. It's often associated with some level of hearing loss as well. And so, what we've been doing right now is not directly related to say, treating tinnitus, because we don't really understand what's the underlying pathogenesis for tinnitus. But having said that, what we have done is to begin to establish a kind of pharmacology of the inner ear, understanding what kinds of neurochemicals work there. And that gives us some insights into how we might think about treating those sorts of disorders.
FLATOW: We have a question from Second Life from Paxus Infinity(ph). He says, can we perhaps use stem cells to repair these hearing losses and these damaged hairy cells?
Dr. FUCHS: Great question. And this is really the holy grail of people that are working on the medicine of the ear, if you will, that - the idea that we can find a way to re-grow those cells which are permanently wiped out by loud sound damage would be a wonderful thing. And the amazing thing is that we mammals are sort of behind the eight ball on this. Other vertebrates - birds in particular - can re-grow their hair cells, no problem.
FLATOW: They can?
Dr. FUCHS: Yeah, yeah.
FLATOW: They - wow. Do we know why and how they do that?
Dr. FUCHS: So, this is one of those kinds of lines of investigation where people doing interesting comparative studies are hoping to find cues that will allow us to do the same thing for mammals. If we can figure out how a bird's hair cells are able to be regenerated, what the molecular controls are for that, then we may be able to reactivate those kinds of controls in a mammal.
FLATOW: Wow, it's sort of like understanding how some of these lizards regenerate their limbs.
Dr. FUCHS: Exactly. Yep, right. It's a good analogy.
FLATOW: Making it work here or the - we talk about nerve damage a lot - using embryonic stem cells. There was a success - or a trial announced just this week.
Dr. FUCHS: Yes, yes.
FLATOW: So, where do you go from here? What do you want to know next?
Dr. FUCHS: Well, we're going to continue to look into these kinds of mechanisms. There's some really intriguing associations that other workers in the field have drawn between the strength of this efferent feedback mechanism and other kinds of more complex auditory dysfunction. So for instance, there's a group in France headed by Lionel Collet, who for years has been asking whether there might be some association between this feedback process and learning - auditory learning or even learning to read. And there's some intriguing connections between children with dyslexia and the strength of this efferent feedback pathway.
FLATOW: Oh, you mean there may be some disruption in the pathway?
Dr. FUCHS: Yeah. It looks like - for instance, if you would look at professional musicians, they tend to have much stronger efferent feedback to the ear than non-musicians. It's as though this system can be made stronger through use, and it's helpful for some reasons and in some situations to do better signals analysis by the ear.
FLATOW: When you say they have control over that efferent feedback, is that to better hear the music or to survive the loudness of it?
Dr. FUCHS: Now, that's a good question, very insightful.
FLATOW: Thank you.
Dr. FUCHS: That would be something one would like to look into. But the presumption is, in fact, that we not only use this system for protecting the ear, but because it helps to improve some aspects of signals analysis by the ear, in fact, it's also useful for the requirements of understanding speech and music and other difficult listening environments.
FLATOW: Because we also echolocate, too, with our ears, don't we? Try to figure out where sounds are coming from and…
Dr. FUCHS: Yeah, that's right. Yes, another circumstance where this could be very helpful because in fact, our capacity to localize a sound in space is better if we slightly inhibit our ears than if we use them with their normal sensitivity. Sounds a little paradoxical…
Dr. FUCHS: But turns out to be true - the case.
FLATOW: So, if you're paying attention to try to figure out where you are, maybe you're turning down - you're tweaking down the part that's sensitive but maybe turning up the part that helps you locate where you are?
Dr. FUCHS: Exactly. Because what happens is you actually get better temporal resolution when your ear's a little bit inhibited. So, you can kind of trade-off sensitivity for temporal resolution. And so, there are some times when you want to know where something is, other times you want to know exactly what it is and use your most delicate sensitivity.
FLATOW: You know, I don't think any of us have realized that the ear is a two-way street.
Dr. FUCHS: Isn't that amazing? Yeah.
Dr. FUCHS: In fact, the ear produces sound.
FLATOW: Tell us.
(Soundbite of laughter)
Dr. FUCHS: This is a very strange phenomenon but very real. And that is that in about one-third of adults and in many newborns - most newborns, there are spontaneous sounds that emanate from the ear. They're typically very quiet, and so one can't hear them oneself, but with a sensitive microphone stuck into the ear canal - the external ear - you can pick these things up and measure them.
FLATOW: This is not the ringing that I'm hearing in my ear?
Dr. FUCHS: No, that's right. This is distinct from it. In fact, this is a feature of a normal, healthy ear. And these so-called "ear sounds" - or "local acoustic emissions" is the term in the scientific literature - these are a feature of normal function of the ear, and they can be used diagnostically. In fact, they are for newborn infants, to ask, is the cochlea working normally? If you put a sensitive microphone in the ear of a newborn infant, without having to ask it a question, you can tell whether its cochlea is in fact healthy.
FLATOW: Wow, this is fascinating stuff.
Dr. FUCHS: Yeah, I think it is, too (Laughing).
FLATOW: I'll bet you do, and you're lucky to be working in it. Thank you, Dr. Fuchs, for taking time to be with us.
Dr. FUCHS: I very much appreciate it and thank you for your interest.
FLATOW: You're welcome. We'll have you back when you make some new progress. Please, come back.
Dr. FUCHS: Thanks very much.
FLATOW: Paul Fuchs is a professor of otolaryngology and co-director of the Center for Sensory Biology at Johns Hopkins School of - well, Basic Biomedical Sciences Department. We're going to take a break. When we come back, we're going to change gears a little bit and talk about, well, researchers in the journal Nature talking about Antarctica. Antarctica is really cooling; it's not warming like they say. New research about that. Stay with us; we'll be right back.
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