Brain cells develop faster in space than on Earth

In space, the force of gravity is reduced to miniscule levels, known as microgravity. This absence of gravitational pull is known to influence muscles, bones, cognition and the immune system, but its specific effects on the brain have remained largely unexplored.

To investigate, scientists from Scripps Research collaborated with the New York Stem Cell Foundation to send brain cell organoids to the International Space Station (ISS).

These tiny, stem-cell-derived clumps offer a unique window into understanding the neurological effects of microgravity.

Brain cells in space

After a month, the organoids returned from the ISS in a healthy state, showcasing an unexpected resilience. Even more remarkable was that these cells matured faster than their Earth-bound counterparts.

Published in the journal Stem Cells Translational Medicine, the study revealed that the space cells were closer to becoming adult neurons and had begun showing specialization.

“The fact that these cells survived in space was a big surprise,” said co-senior author Dr. Jeanne Loring, professor emeritus at Scripps Research.

“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.”

Organoids and their earthly counterparts

On Earth, the researchers cultivated organoids from stem cells to mimic specific brain cells like cortical and dopaminergic neurons.

These types are significant as they are impacted by conditions like multiple sclerosis and Parkinson’s disease. Some organoids also included microglia, immune cells that play a key role in brain inflammation.

To ensure the organoids could sustain themselves aboard the ISS, the team innovated a method using cryovials – small, airtight containers designed for freezing – in which to grow smaller-than-usual organoids.

This eliminated the need for constant maintenance in orbit, as the nutrient-rich medium within the cryovials remained stable for the duration of the experiment.

From Earth to orbit and back

Prepared at Kennedy Space Center, the organoids traveled to the ISS in a miniature incubator. After spending a month in microgravity, the brain-mimicking organoids returned to Earth intact and healthy.

The researchers then compared the RNA expression patterns – a measure of gene activity – between the space-exposed organoids and those that had remained on Earth.

The results were striking. The brain organoids grown in microgravity exhibited a gene expression pattern that indicated they were more mature than their Earth-grown counterparts.

“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,” explained Dr. Loring.

“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.”

Response of brain cells in space

Interestingly, the study also revealed reduced inflammation and lower expression of stress-related genes in space-grown organoids. This finding contradicted initial hypotheses and raised new questions about the unique environment of microgravity.

Dr. Loring speculates that microgravity may more closely replicate the natural conditions experienced by brain cells.

“The characteristics of microgravity are probably also at work in people’s brains, because there’s no convection in microgravity – in other words, things don’t move,” noted Dr. Loring.

“I think that in space, these organoids are more like the brain because they’re not getting flushed with a whole bunch of culture medium or oxygen. They’re very independent; they form something like a brainlet, a microcosm of the brain.”

Next steps in space-based research

Building on this initial success, the team has since launched four additional missions to the ISS, replicating the conditions of the first and introducing new experiments.

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

“We also want to know whether there are differences in 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.”

New frontiers in neuroscience

This remarkable research was supported by the National Stem Cell Foundation.

The paper, titled “Effects of microgravity on human iPSC-derived neural organoids on the International Space Station,” includes contributions from Scripps Research scientists and collaborators at the New York Stem Cell Foundation Research Institute, Space Tango, and the National Stem Cell Foundation.

The findings represent a significant step in understanding how microgravity impacts brain development and function.

As research progresses, these insights may lead to innovative treatments for neurodegenerative diseases and a deeper understanding of human biology in space.

The study is published in the journal Stem Cells Translational Medicine.

Image Credit: Jeanne Loring

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