In a significant scientific advancement that bridges space exploration and neuroscience, researchers have discovered that human brain cells develop differently in the weightless environment of space compared to Earth. While scientists have long known that microgravity affects muscles, bones, the immune system and cognition, little was understood about its specific impact on the brain until now. The research sheds new light on our understanding of how the human brain adapts during space travel, and could even offer new perspectives for studying neurological diseases like Parkinson’s and multiple sclerosis.
The study, published in Stem Cells Translational Medicine, documents the first successful growth and analysis of human brain tissue models – called neural organoids – on the International Space Station (ISS). These three-dimensional clusters of brain cells, measuring a few hundred micrometers in diameter, spent 30 days in orbit approximately 250 miles above Earth’s surface in what scientists call microgravity.
The research team created these organoids using human induced pluripotent stem cells (iPSCs) – adult cells that have been reprogrammed to regain the ability to develop into different cell types. They developed two distinct varieties of neural organoids: some containing cells similar to those found in the brain’s cortex (the outer layer involved in thinking and memory), and others containing dopamine-producing neurons, which are typically affected in Parkinson’s disease.
The study included cells from four individuals – two healthy donors and two patients with neurological conditions (one with Parkinson’s disease and one with primary progressive multiple sclerosis). To make the models more comprehensive, the researchers added immune cells called microglia to half of the organoids to observe how the brain’s resident immune system might function in the space environment.
A key innovation was the method developed to maintain these delicate structures during spaceflight. Organoids are usually grown in nutrient-rich liquid that must be changed regularly to provide nutrition and remove waste products. To avoid the need for laboratory work on the ISS, the research team pioneered a method for growing smaller-than-usual organoids in cryovials—small, airtight containers originally designed for deep freezing. Each organoid was sealed in a vial containing one milliliter of specially formulated growth medium.
The organoids were prepared in laboratories at the Kennedy Space Station and launched to the ISS in a miniature incubator. “The fact that these cells survived in space was a big surprise,” says Jeanne Loring, PhD, professor emeritus in the Department of Molecular Medicine and founding director of the Center for Regenerative Medicine at Scripps Research, in a statement.
When analyzing the returned organoids, the researchers found distinct differences between the space-grown samples and their Earth-bound 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,” says 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.”
The research team found that when placed in laboratory dishes after returning to Earth, these cells demonstrated their viability by extending networks of connecting fibers called neurites. Contrary to what might be expected, the analysis showed minimal evidence of cellular stress or inflammation in the space-grown organoids—in fact, there was less inflammation and lower expression of stress-related genes compared to Earth-grown samples.
The study revealed alterations in cellular communication pathways, particularly in Wnt signaling, which plays fundamental roles in brain development. The researchers also observed changes in the proteins secreted by the cells into their surrounding environment, though these changes varied between the different types of organoids.
Notably, these cellular changes appeared to be primarily influenced by the microgravity environment rather than space radiation. The radiation exposure during the 30-day mission was approximately 12 milligrays – comparable to what airline crew members might experience over a similar period of long-haul flights.
Why might brain cells develop differently in space? “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,” says 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.”
These findings contribute to both space exploration research and potential medical applications. Understanding how brain cells respond to microgravity could inform strategies to support astronaut health during extended space missions. Additionally, studying how these cells develop differently in space might provide new perspectives for investigating neurological conditions on Earth.
This initial success has paved the way for continued research. Since this first mission, and before the publication of these results, the research team has already completed four more missions to the ISS, each building upon their initial findings while adding new experimental conditions. Future studies will examine brain regions affected by Alzheimer’s disease and investigate potential differences in how neurons connect with each other in space.
Source: https://studyfinds.org/brain-cells-international-space-station/