Jocelyne Bloch: After An Injury, Can The Brain Heal Itself? Neurosurgeon Jocelyne Bloch and her colleague were studying brain samples of head trauma patients when they made an amazing discovery — brain cells with the ability to generate new cells.

Jocelyne Bloch: After An Injury, Can The Brain Heal Itself?

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I know this is stating the obvious, but the brain is, by far, the most complex part of the human body, right?

JOCELYNE BLOCH: In a way, yes, I think so.

RAZ: This is Jocelyne Bloch.

BLOCH: Because we do not understand completely what the brain is - how the brain is performing. And we still know that there is much to discover.

RAZ: Jocelyne's a neurosurgeon who's trying to rethink how we can heal the brain by helping the brain heal itself.

BLOCH: So if you break your arm, I mean, your bone can be reconstructed. And even if the bone is not perfect, you want to have a stiff bone to make your arm hold. But if - in the brain, since some of the area of the brain are responsible for function, if you lose these areas, it's difficult for the rest of the brain to take over.

RAZ: That's because the brain can't grow enough new cells to fully repair damaged ones. Even with advancements in technology, like neural stimulation through electricity, we're still kind of limited with what we can actually do to fix the brain. But Jocelyne believes those boundaries can be pushed and pushed far.

BLOCH: What I see with a deep brain stimulation is that it really helps for symptoms but not - it doesn't cure a disease. So what we really would like to do is to not only to stimulate areas of the brain but also to add new cells to have more possibilities to stimulate and to make the brain work.

RAZ: So I guess the dream you're talking about is actually not just allowing the brain to kind of improvise for the parts of the brain that were damaged but to actually fix the damaged part of the brain.


RAZ: So about two decades ago, while Jocelyne was working in the emergency room, she and another colleague, Jean-Francois Brunet, started studying brain samples of head trauma patients.

BLOCH: So Jean-Francois wanted to grow cells from the cortex. The cortex is the layer that is surrounding our brain. And from these pieces of cortex, we wanted to see what kind of culture we were able to grow. And so what we saw under the microscope were really looking like stem cells culture, which was really surprising. That was surprising.

RAZ: So, I mean, this is kind of a big deal - right? - because, I mean, stem cells produce more cells, right?

BLOCH: Yeah. It was a big deal because they looked like stem cells, but they were not behaving exactly the same as stem cells. So probably you know that stem cells renew very rapidly, and they almost never die. They divide and divide and divide. And they are not getting old. But in our cell culture, we saw that the cells were dividing slower. And, also, after a few weeks of culture, they had the tendency to get older and eventually even die.

When I say that cells are dividing all the time and never die, you always think of a tumor formation because that's exactly the definition of a tumor, cells that divide, divide and that you lose control of. So people are a bit scared of stem cells - to implant stem cells knowing that they may eventually turn to tumors after a while because they never stop this division. And so we were quite happy to see that we had to kind of stem cells that was more quiet and that would have a death after a while.

RAZ: And this was significant because maybe those cells could be used to regrow damaged parts of the brain. But Jocelyne and her lab partner weren't sure. They needed proof.

BLOCH: The problem was that, you know, in all these experiments, you cannot start with humans.

RAZ: So they use the closest substitute they could find, monkeys. In a moment, what happened with that experiment and how its findings could fundamentally change the way we think about our brains. I'm Guy Raz. And you're listening to the TED Radio Hour from NPR.


RAZ: It's the TED Radio Hour from NPR. I'm Guy Raz. And before the break, we were hearing from neurosurgeon Jocelyne Bloch. About 20 years ago, she and another colleague were trying to find out if the brain could repair itself using its own cells.

BLOCH: The idea was to try to use them to put them back in the host, in the same person that gave his own cells for the culture.

RAZ: So to test this idea, they ran an experiment comparing what happens in a healthy monkey brain with a damaged monkey brain. Jocelyne picks up the story from the TED stage.


BLOCH: So the first question we had - what will happen if we reimplant these cells in a normal brain? And what will happen if you reimplant the same cells in the lesion brain? So in the first case scenario, we reimplanted the cells in the normal brain. And what we saw is that they completely disappeared after a few weeks, as if they are taken from the brain. They go back home. The space is already busy. They are not needed there, so they disappear. In the second case scenario, we perform the lesion, we re-implanted exactly the same cells. And in this case, the cells remains, and they became mature neurons. But we could not stop here, of course. Do these cells also help the monkey to recover after a lesion? So for that, we trained monkeys to perform a manual dexterity task. They had to retrieve food pellets from a tray.

So that was the first step.

RAZ: You had them retrieve food from a tray. You just taught them...

BLOCH: Exactly.

RAZ: OK. And they got pretty good at it.

BLOCH: Food pellets from a tray. They were really good.

RAZ: Yeah.

BLOCH: So it's a task that you can ask monkeys to do. And they're really - after a while, when they get used to do it, they're really good at it, and they can make it fast.


BLOCH: And when they had reached a plateau of performance, we did a lesion in the motor cortex corresponding to the hand motion. So the monkeys were plegic. They could not move their hand anymore. And exactly the same as humans would do, they spontaneously recovered to a certain extent - exactly the same after a stroke. Patients are completely plegic. And then they try to recover. Due to brain spasticity mechanism, they recover to a certain extent - exactly the same for the monkey.

RAZ: OK. So essentially, after the lesion, where you deliberately damaged the monkey's brain to kind of simulate what a stroke would be like, you guys were just watching the monkeys, just observing them because you knew they could recover some of their ability to use their hands to retrieve the food pellets, right?

BLOCH: Exactly.

RAZ: But you also knew that it was unlikely that the monkey would be able to do it as well as it did before the lesion, right?

BLOCH: Yeah, they did. But that's what we can model that we know because we've been working on this kind of lesions for years in the lab where we work. So we knew that they would recover to a certain extent. And generally, it's about 30 to 50 percent of the previous function, when everything was normal.

BLOCH: So, at this point, the monkey's - he's able to grab the food but slowly.

BLOCH: Exactly.


BLOCH: So when we were sure that the monkey has reached his plateau of spontaneous recovery, we implanted his own cells. So on the left side, you see the monkey that has spontaneously recovered. So he's about 40 to 50 percent of his previous performance before the lesion. He's not so accurate, not so quick. And look now when we reimplant the cells. Two months after implantation, the same individual.

RAZ: And what happened? Did it - what was going on in that monkey's brain?

BLOCH: So we observed that after the reimplantation, the monkey starts to improve. So the way he retrieved these food pellets in the tray is becoming more accurate and faster.


BLOCH: It was, for us, also a very exciting result, I tell you.

RAZ: So, essentially, without doing anything, we know that the brain is going to recover - probably to a certain extent. But after you implanted the monkey's own cells back into the monkey's brain, it recovered even further. I mean, you can see - I mean, you showed this video on stage. You can see it.

BLOCH: Correct. Exactly.

RAZ: I mean, it's...

BLOCH: It's pretty surprising.

RAZ: It's incredible.

BLOCH: And what is also very incredible is that we do not do much. Actually, we leave the cells go wherever they want. We do not guide them. So they are clever enough to participate to this recovery without any help from us. I mean, the brain itself is giving them the role they need to play to help the individual to recover.

RAZ: I mean, of course, the implications of this are enormous because if we could figure out how to do this in humans who suffer from strokes or have other neurological disorders, it could completely change the way our brains are treated by medicine.

BLOCH: Yeah. I think so, too. But the problem is to have the possibility to do it. And that's the problem we face. It's an incredible weapon. We may have to cure ourselves, you know? But it's - until we try it, it's hard to say if it's going to work in humans who have large lesions, for example, you know, because we've been working with monkeys that have a very restricted lesion of the brain. We've shown that they improved.

But in humans - sometimes people have larger lesions. And will it be also enough to bring a few cells surrounding lesions in these patients? This we don't know. But I think that it's a kind of new personalized medicine. So - now, is it going to work in everybody the way we would love to? Maybe not. But I think it's the way the medicine is going to evolve.

RAZ: Jocelyne Bloch is a neurosurgeon at Lausanne University Hospital in Lausanne, Switzerland. You can see her full talk at On the show today ideas about Rethinking Medicine.

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