Stranded past their limit, the stem cells refused to die

In early 2024, lab-grown clusters of neural stem cells flew to the International Space Station to be exposed to microgravity. Their return trip kept getting delayed by bad weather at the landing site, so the cells sat outside controlled conditions far longer than anyone expected them to survive. Back at Uppsala Biomedical Center, they looked wrong — fragments of clusters, not healthy spheres. Then the team changed the growth medium and waited. A month later the surviving cells were not only growing again but developing into nerve cells and glial cells and working normally in tests. Cells held in 3D-printed support structures survived best of all. Published in the peer-reviewed journal npj Microgravity, the work hints at a future where long space missions can grow replacement cells and tissues on site to treat injured astronauts — and could teach doctors on Earth new tricks about healing nerves, back pain and diabetes.