Stem Cells in Space Survived a Rough Trip They Shouldn't Have Endured

Stem cells in space were never supposed to survive what happened to this batch. In early 2024, lab-grown clusters of neural stem cells called neurospheres were sent to the International Space Station for a stretch of microgravity exposure, according to phys.org. Bad weather at the landing zone delayed the return several times, leaving the cells outside carefully controlled culture conditions for far longer than they were ever expected to endure.

When the samples finally reached Uppsala University's Biomedical Center in Sweden, only a fraction had made it. The stem cells in space that survived shared one history: they had already flown once before, aboard a 2023 sounding rocket above Kiruna's Esrange Space Center, where they experienced six minutes of weightlessness. Researcher Elena Kozlova said the team simply changed the culture medium and waited. Some cells recovered and, as Kozlova put it, began to grow again "very slowly" — so slowly that the real experiments could not begin until a month later.

The stem cells in space that beat the odds

The clearest finding was structural. Cells placed in 3D-printed support structures fared particularly well across all groups: they survived the ordeal and kept dividing. Those survivors could still develop into nerve cells and glial cells, and they functioned normally in the researchers' tests. Because the delays had extended the experiment well past its planned length, the team could see just how significant the printed structure was for survival — a discovery that might have stayed hidden in a shorter trial.

Uppsala University said the result builds on a longer story. That sounding-rocket test showed the cells dividing faster, growing more robust, and maturing more slowly, which left behind a larger pool of stem cells. The following January, fifty million stem cells grown from a mouse embryo rode to the space station alongside Swedish astronaut Marcus Wandt, the country's third astronaut; despite a weather delay that stretched the return, they landed in perfect condition. The full results appeared in the journal npj Microgravity in October 2026, drawing on a research network spanning the US, the UK, Italy, Switzerland, and other countries, with several groups now working the material for fresh insights.

Not every batch of stem cells in space fares the same

The contrast with other cell types is the second big takeaway. A 2025 study from the University of California, San Diego, published in Cell Stem Cell, found that human blood-forming stem cells aged faster after 32 to 45 days on the station — burning through energy reserves, losing rest, accumulating DNA damage, and growing shorter telomeres, according to the study's authors. Blood stem cells, in other words, deteriorated in orbit while neural-crest stem cells in printed scaffolds survived an even rougher ride. Co-author Catriona Jamieson described space as "the ultimate stress test" for the human body.

What stem cells in space mean for a Mars trip

For anyone following plans for crewed deep-space missions, this matters. Future astronauts will need ways to treat injuries and illnesses on site, possibly by growing replacement cells and tissues for transplants far from any hospital. The Uppsala group works with induced pluripotent stem cell technology — the approach recognized by the 2012 Nobel Prize, in which skin cells are reprogrammed into stem cells able to become practically any cell type. Stem cells in space could one day supply exactly that kind of on-demand medicine.

The payoff is not only for astronauts. The same group studies how microgravity affects cells and tissues tied to back pain and type 1 diabetes, and upcoming lab experiments will recreate the effects of weightlessness without leaving Earth. If a printed scaffold can keep neural stem cells alive through a botched return trip, it may also teach scientists how to keep the body's repair systems working when gravity is not there to help.

More missions will keep testing the limits. Readers can also see how NASA's Three Tiny Satellites Test the Future of Spaceflight, and follow all of our coverage on the science topic page. The stem cells in space that outlasted their own survival odds may have just written the first draft of the medical playbook for the long trip to Mars.