New research using organoids has found that brain cells in space remain healthy, but mature faster than they would on Earth.

Numerous studies have outlined the effect microgravity, or limited gravity, on muscles, bones, the immune system and cognitive function. But until now, no studies have specifically looked into how space impacts brain cells.

To better understand how the brain is impacted, a team at Scripps Research Institute in California, with the New York Stem Cell Foundation, sent tiny clumps of stem cells – that came from brain cells –  to the International Space Station (ISS).

After a month  the organoids returned to Earth healthy and intact.

“The fact that these cells survived in space was a big surprise,” says co-author Jeanne Loring, founding director of the Center for Regenerative Medicine at Scripps.

However, the cells from the ISS had matured faster than compared to identical cells that remained on Earth.

“We discovered that in both types of organoids, the gene expression profile was characteristic of an older stage of development than the ones that were on ground,” says Loring.

After the month of growth, the researchers compared the RNA expression patterns on the ISS cells to a control group of cells that remained on Earth.

This comparison in RNA expression allowed the team to examine how the space environment impacts the brain at a cellular level.

The RNA in cells from the ISS contained a higher level of genes associated with mature cells rather than new cells.

“In microgravity, they developed faster, but it’s really important to know these were not adult neurons, so this doesn’t tell us anything about aging,” says Loring.

One challenge the team faced was that for the cells to have access to adequate nutrition they required a particular nutrient-rich liquid which needs to be changed regularly.

To reduce the amount of lab work on the ISS, the team created a method that produced smaller cells in cryovials, small airtight cylinders. These cryovials were then transported in an incubator up to the ISS for one month.

The researchers also found that the cells on the ISS replicated less than those on Earth.

“This lays the groundwork for future experiments in space, in which we can include other parts of the brain that are affected by neurodegenerative disease,” Loring says.

While the paper, published in Stem Cells Translational Medicine, only focused on this first mission, the team has since sent four more missions to the ISS.

“The next thing we plan to do is to study the part of the brain that’s most affected by Alzheimer’s disease,” says Loring.

The team hope to continue their study by looking deeper into the way neurons connect with each other in space.

“With these kinds of studies, you can’t rely on earlier work to predict what the result would be because there is no earlier work.”

“We’re on the ground floor, so to speak; in the sky, but on the ground floor.”

Astronauts and their brains