Coaxing Nerves To Repair Breaks

7:16 minutes

Researchers reported this week that they’ve made progress in helping peripheral nerves (ones outside the central nervous system) regrow after injury. These nerves, which serve to connect the brain and spinal cord to the other parts of the body, can regrow small amounts after injury. However, until now, doctors have had to repair larger gaps by grafting nerve tissue taken from elsewhere in the body. In the new work, reported in the journal Science Translational Medicine, researchers built a synthetic conduit across a nerve gap in a monkey’s arm. The conduit released a nerve growth factor, encouraging the new nerve cells to fill in the missing tissue. 

Illustration of nerve cells
Credit: Shutterstock

Sophie Bushwick, technology editor at Scientific American, joins Ira to talk about the work and what it could mean for humans with nerve injuries. They’ll also talk about other stories from the week in science, including an analysis of the speed at which popular culture evolves, a look at the link between depression and cell phone use, and work that attempted to reconstruct the vocal tract of a 3000-year-old mummy.

Further Reading

Segment Guests

Sophie Bushwick

Sophie Bushwick is senior news editor at New Scientist in New York, New York. Previously, she was a senior editor at Popular Science and technology editor at Scientific American.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. A little later in the hour, we’ll be talking about the coronavirus that has caused China to shut down a dozen cities. But first, researchers reported this week that they’ve made progress in helping peripheral nerves regrow. Those are the nerves outside the central nervous system like in an arm or a leg. Joining me to talk more about that and other short subjects in science is Sophie Bushwick, Technology Editor at Scientific American. Hi, Sophie.


IRA FLATOW: I’ve been following stories like these for years, but this one really seemed special.

SOPHIE BUSHWICK: This one’s really interesting. So a lot of nerve regrowth studies try to use stem cells. This one doesn’t. So that could give it an edge at getting FDA approval because it’s very straightforward. Essentially, what the researchers did was they took a small tube made of a material sort of like that in dissolving stitches, and they put a protein that encourages nerve growth in it and then implanted it in monkeys and in rodents that had peripheral nerve injuries.

And the idea is that this would encourage– if you have a nerve with, say, a small gap in it, you can put this in there, and the nerve will regrow itself along the tube, and the tube will then dissolve. And they had really– they had a lot of success.

In a lot of cases of nerve injury, the person often only regains maybe 50% to 60% of their use of that nerve. In this case, the animals got back 80%. And in the case of the monkeys, these macaques, they were able to pinch food pellets between two fingers instead of having to grasp them in a fist. And they slowly learned how to do that as their nerve healed.

IRA FLATOW: And from looking at the research, what was really interesting about it is the gap that they could cover over was over an inch wide.



SOPHIE BUSHWICK: In a lot of cases, that type of injury might require a transplant. They might have to take a nerve from elsewhere in the body and use it as a patch which gives the patient two injuries to then recover from. So the idea that they could regrow this nerve without requiring that kind of treatment is really exciting.

IRA FLATOW: So this is not for spinal cord injuries like that, right?

SOPHIE BUSHWICK: That’s right. The spinal cord is too complex for this type of treatment. This would be more if there was an injury to the nerves in the hand or the arm or maybe the feet or the legs, it could help restore function in those parts. And there are about 600,000 peripheral nerve injuries per year, so this really has the potential to help.

IRA FLATOW: Not to mention the military.

SOPHIE BUSHWICK: Absolutely. It’s a big issue there because a lot of body armor might be concentrated over the torso and the head and can leave limbs more vulnerable.

IRA FLATOW: Interesting. Let’s change directions from peripheral nerves to our general mental health. There’s been concern about what all this smartphone use might be doing to our brains, especially in teens, and there’s some news on that front?

SOPHIE BUSHWICK: Yes, there’s some positive news, actually, for once. [LAUGHS]


SOPHIE BUSHWICK: So there’s a lot of people who have pointed out that there are increasing rates of disorders like depression and anxiety, and they have tied that to an increase in screen time. So researchers went and looked at more than 200 studies of screen time and mental disorders, and they found that there’s only a very slight connection.

And there’s the possibility that it’s not a case of cause and effect. It could just be a case of correlation. So it’s not necessarily that spending more time on the screen makes a teenager feel more likely to develop depression. It could be that a teenager who is prone to depression might spend more time on their screen. So these studies haven’t proven that it’s one thing or the other.

IRA FLATOW: It’s not a cause and effect sort of study.


IRA FLATOW: It something called a meta analysis– a study of studies.

SOPHIE BUSHWICK: A study of studies. And they looked at a lot of studies, and there’s been a lot of people. This isn’t the only study to reexamine the sort of body of evidence amassed so far. And it does look like some of the fears about screen time were overblown, and that they don’t have quite the detrimental effect that people worried about.

IRA FLATOW: That’s good. It’s good to hear. There is some news out. Our popular culture seems to be in a state of constant flux. But there’s some new research trying to quantify just how fast it changes, right?

SOPHIE BUSHWICK: Yes, this was really cool. So basically, they took a lot of pop cultural, I guess, artifacts, you could say. So they looked at pop music during the decades from, I think, the ’60s to the present. They looked at more than 2,000 cars that run on fossil fuels and how those cars kind of changed over time.

They also looked at 19th century books and literature in the English language, and they looked at more than 100,000 medical studies. And so they tried to say, in each of these cases, what is something that we can– what is a feature we can isolate and see how it changes over time, like maybe the size of a certain part of the car or a topic that comes up a lot? Like the topic of the English aristocracy in these novels, how is the treatment changed? Is it paid attention to more or less over time?

And what they found is that the evolution of these traits is very gradual. And they compared it, actually, to the animal evolution. So they looked at some cases of, for example, Darwin’s finches and how their beak size changed over time. And the researchers in this paper concluded that pop culture and animals evolved at roughly the same rates.

IRA FLATOW: Wow, that is interesting. Finally, there’s a study that features this sound–



SOPHIE BUSHWICK: So that is a 3,000– more than 3,000-year-old sound that we’re hearing again, brought back from the dead. It’s no longer under wraps.

IRA FLATOW: Well, what is it?

SOPHIE BUSHWICK: Oh, I’ll get to the point. [LAUGHS]

SOPHIE BUSHWICK: This is the recreated voice of a mummy, an ancient Egyptian mummy. So researchers scanned the ACT scans to look at the vocal tract of this mummy. And then they 3D-printed a replica, and they hooked it up to this machine that does, basically, it imitates the vocal chords. So they sent a simulation of an adult male’s production of his vocal cords through this replica of the vocal tract, and it went, ehh, ehh.

IRA FLATOW: Ehh, ehh. It sounds like it’s backing up.


IRA FLATOW: What about the other parts, you know, the mouth, the throat, and the head? Wouldn’t that change the way it actually sounds?

SOPHIE BUSHWICK: Absolutely. So the vocal tract sort of goes from the voice box up to the nasal cavity and the mouth. And basically, what this thing reflects is basically the shape that this vocal tract had when the mummy was at rest. So when I talk, I’m constantly moving my vocal tract to make these different vowel sounds that are coming out of my mouth.

And you can actually– researchers have looked at people doing this in MRI machines and in CT scans. But this is a case of doing it for someone who is much, much, much, much, much older than your average subject. And so it’s less a reflection of what the real voice sounded like and more a reflection of the current shape of the vocal tract.

IRA FLATOW: Great. Cool stuff you always bring us, Sophie.


IRA FLATOW: Sophie Bushwick, Technology Editor at Scientific American.

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