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How Scientists Are Growing Mini Brains In Petri Dishes For Experiments


All this week we are talking to our friends here at NPR about their favorite things from 2017. And we're nerding out here. These are not, like, simple best-of lists.

Today, science correspondent Jon Hamilton is here to share his highly specific superlative. Hello there.


MCEVERS: OK. What do you have?

HAMILTON: I have got what I consider, like, the weirdest and coolest advance in brain science. And what it is is researchers have gotten really good at growing tiny human brains in the lab.

MCEVERS: OK, like, in a petri dish?

HAMILTON: Well, kind of. They actually grow them in something called a bioreactor. And then as they grow, they actually begin to assemble themselves very much the way cells do in the human brain during development in the fetus.

MCEVERS: Do they look like tiny brains?

HAMILTON: Well, a little bit. They are about the size of a pinhead, so they're considerably smaller than a human brain. But they are round clusters of cells. As they grow, they acquire some of the structures of the human brain, but not all of them. So they don't have all of the areas that human brain has. They don't work like a fully functioning human brain.

MCEVERS: What are scientists doing with these tiny brains?

HAMILTON: They've got a couple of things that they've been able to do with these brains they haven't been able to do any other way. One of them is that they can actually study how the human brain develops. I mean, you can't go and look at what is happening inside of the womb, but you can study how these little clusters of cells grow. And it turns out they grow very much the way that cells do during early brain development. So they've learned that.

They are also testing experimental drugs for brain diseases because it turns out mouse brains are very different than human brains. And testing in human cells is really valuable. The final thing they're doing is they're looking at brain diseases. And one of the things that they actually have succeeded is they were able to figure out how Zika virus is altering the development, the early development, of the human brain by actually infecting some of these little mini brains with Zika.

MCEVERS: Wow. At some point, are we going to see scientists be able to grow, like, a full human brain?

HAMILTON: Right. That is the creepy question, right?

MCEVERS: Right. I mean, yeah.

HAMILTON: Short answer - no. For one thing, mini brains, as I said, have a couple hundred thousand cells. The human brain has 86 billion cells thereabout, right? So there are some order-of-magnitude differences here. But really, what's more important than that is the human brain doesn't become what it is just by growing more and more cells. The human brain is the product of input from our eyes and our ears and interactions with other people and thoughts. And mini brains don't have any inputs. They don't talk to other people. They don't have thoughts - or at least they don't yet.

MCEVERS: (Laughter) Any tiny anything that we - that you're excited about for next year?

HAMILTON: There are tiny lots of things. They are growing all different body parts in test tubes essentially in the lab. And so you're now able to have little tiny hearts and kidneys and livers and so on that they're able to test much the way they are the brains.

MCEVERS: NPR's Jon Hamilton, thanks so much for sharing your super specific superlative with us.

HAMILTON: My pleasure.


Jon Hamilton is a correspondent for NPR's Science Desk. Currently he focuses on neuroscience and health risks.