DAVID GREENE, HOST:
Some tiny brains are making big news this week at the world's largest neuroscience meeting. Minibrains are these lab-created clusters of living human brain cells that mimic some of the functions of actual, fully developed brains. As NPR's Jon Hamilton reports, they are helping scientists answer questions about everything from early brain development to infection with the Zika virus.
JON HAMILTON, BYLINE: Unlike real brains, minibrains are made in laboratories - labs like this one at Johns Hopkins University in Baltimore. Hongjun Song, the scientist in charge, takes me to a small, windowless room with a powerful air filtration system. He opens an incubator the size of a dorm fridge and points inside.
HONGJUN SONG: So this is the device we've developed.
HAMILTON: The device is only a bit larger than a cell phone, but Song says it's a complete minibrain factory. The lower half looks like a miniature muffin pan with a dozen separate compartments.
SONG: Yeah, we can grow up to five to 10 minibrain in each one.
HAMILTON: These minibrains aren't just random clumps of human brain cells. They contain many of the structures and connections found in real brains. And figuring out how to grow them has taken a lot of work. About three years ago, scientists in Europe showed how to coax brain cells into specializing and organizing much the way a developing brain does. The Hopkins team has streamlined and improved the process. Guo-Li Ming, a professor at Hopkins, says each minibrain is just big enough to see with the naked eye.
GUO-LI MING: It's basically, like, a ball of cells clustering together. But if you open it up, you really see something very similar to the early embryonic brain.
HAMILTON: It's not just that they look like embryonic brains. They also grow the way a brain does in the womb. And that led to a big discovery with a minibrain just a few months ago. It involved the Zika virus, which was suspected of derailing brain development in early pregnancy. Ming says she and Hongjun Song, who are married, thought their minibrains might offer a way to figure out what was happening. And by chance, the couple knew a researcher at Florida State University who was studying the Zika virus.
MING: So Hongjun called him right away, saying, well, we have the perfect system to work. Do you have the Zika? And he said yes.
HAMILTON: That call led to experiments in minibrains that showed how the infection was attacking certain critical brain cells. The Hopkins team described this research Sunday during a press conference at the Society for Neuroscience meeting in San Diego. Elsewhere at the meeting, scientists are presenting minibrain research on a range of other diseases and disorders, including brain cancer and Down syndrome. Thomas Hartung from Hopkins Bloomberg School of Public Health says minibrains may offer a better way for drug companies to test new products.
THOMAS HARTUNG: One company after the other failed on things like stroke, multiple sclerosis, but also new degenerative diseases, like Alzheimer's and Parkinson's.
HAMILTON: Those drugs worked on animals but failed with people. Hartung says that's because animal brains aren't like human brains.
HARTUNG: We need human systems to tell us about humans, and that's why this is such a big step forward.
HAMILTON: One potential obstacle for minibrain research is public acceptance. Hartung says when people hear about scientists growing brains in a lab, they sometimes imagine a fully functioning organ. And in some ways, he says, the clusters are like real brains.
HARTUNG: These cells are communicating. These neurons are talking to each other. You could say it's a primitive type of thinking.
HAMILTON: But Hartung says these brains contain thousands of cells, not billions like a real brain. And even if they could get bigger, they wouldn't be conscious.
HARTUNG: This has nothing to do with consciousness. This has nothing to do with any type of information which is digested here by these cells because they have no input.
HAMILTON: So they don't have anything to think about. Jon Hamilton, NPR News.
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