In early 2024, laboratory-grown neurospheres (i.e. clusters of neural stem cells) were sent to the International Space Station (ISS) to be exposed to microgravity. The return trip was delayed several times due to bad weather in the landing zone. As a result, the cells were outside controlled culture conditions for longer than anticipated—beyond the limit of what they were expected to survive.

When they finally arrived at the laboratory at the Uppsala Biomedical Center (BMC), no one knew whether it would be possible to complete the experiment.

"When the cells came back, they didn't look normal, but we were still cautiously optimistic. It looked as though there were only small fragments of neurospheres in some groups, but not all of them. Only the cells that had previously been in space on the sounding rocket had survived. So we changed the medium and waited. Then some of the cells recovered and began to grow, very slowly," explains Elena Kozlova.

A month later, the experiments could begin. The results have now been analyzed and are presented in an article in npj Microgravity.

The 3D structure protected the cells
Despite being subjected to severe stress, some of the cells survived. After recovery, they were still able to develop into nerve cells and glial cells and functioned normally in the researchers' tests.

A key finding is that cells placed in 3D-printed support structures fared particularly well across all groups. They survived and continued to divide.

"Thanks to the experiment being extended, we were able to see just how significant the 3D-printed structure was for the cells' survival...