A MARTÍNEZ, HOST:
It's an exciting time for stem cell research, and not just here on Earth. Scientists are looking into the benefits of growing human tissue in space. Here's NPR's Will Stone.
WILL STONE, BYLINE: Let's start with the obvious. If you're waiting for a space-grown organ, don't hold your breath. We're a world away from a spaceship filled with actual organs ready to be harvested. But if all goes according to plan, there will be tiny liver organoids taking shape at the International Space Station next year. These organoids are made from stem cells. They're 3D clusters of cells that mimic the function of liver. Tammy Chang, a surgeon at the University of California, San Francisco, is leading this experiment.
TAMMY CHANG: The stem cell-derived organoids will be in these tissue orbs.
STONE: These tissue orbs are bioreactors. Inside, the cells will float around and stick to each other.
CHANG: We have a central conduit, which is a blood vessel mimic. And our hypothesis is that our organoids will actually assemble and organize on this blood vessel mimic.
STONE: You can simulate microgravity here on Earth with special rotating bioreactors. This isn't perfect, but Chang's research shows these liver organoids function better when grown under those conditions, compared to when they're cultured on top of a protein mixture in a plastic dish.
CHANG: In the environment of microgravity, cells don't have to fight the forces of gravity to come together, like a constant settling force settling to the bottom of the dish.
STONE: Chang suspects that when these organoids are up there in real, sustained microgravity, they'll get larger, more complex and potentially grow blood vessels.
ARUN SHARMA: The thing that everybody's looking for is something that can only be done up there, and you cannot do it down here.
STONE: That's Arun Sharma, a stem cell biologist at Cedars-Sinai Medical Center in Los Angeles. Often, these organoids are used to model diseases and test drugs. Sharma's lab focuses on the heart and is also working with NASA astronauts on stem cell research at the International Space Station.
SHARMA: We and others have shown that certain stem cell populations can proliferate or divide faster in space.
STONE: Scientists researching organoids hope they might one day be used for transplants, although, Sharma stresses...
SHARMA: I don't think we're close yet to fully, perfectly approximating a human heart on Earth from stem cell-derived cells.
STONE: When it comes to microgravity and space, he sees it as another tool.
SHARMA: By having better model systems - systems that have, say, blood vessels incorporated into them - we can better approximate how certain drugs would affect the heart.
STONE: How to bring those organoids back down in good condition is a whole other challenge. In a future experiment, the UCSF team will be testing whether supercooling technology can do that successfully. Dr. Abba Zubair is medical director at the Center for Regenerative Biotherapeutics at the Mayo Clinic in Florida.
ABBA ZUBAIR: Doing research in a microgravity environment is very challenging.
STONE: Things you take for granted, like how to get fluid to mix so you can feed the cells, becomes a new problem to solve. But, he says, this is exciting new territory because there are still many unanswered questions about how gravity - or a lack thereof - influences the way cells function.
ZUBAIR: The effect of gravity on cells is not the same for all type of cells. That's really important, to understand that.
STONE: His research has found in microgravity that certain stem cells grow better and were more immunosuppressive, which could be relevant when thinking about transplants. Yes, it's early days, but he doesn't mind speculating that this research could eventually lead to other insights about how humans can adapt as we voyage deeper into space.
Will Stone, NPR News.
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