Human Neural Stem Cells in Space Proliferate more than Ground Control Cells: Implications for Long-Term Space Travel

Abstract

Long-term travel and lengthy stays for astronauts in outer space are imminent. To date, more than 500 astronauts have experienced the extreme conditions of space flight including microgravity and radiation. For the past decade, many studies associated with long-duration spaceflight have shown the recurring occurrence of ophthalmic abnormalities. The reasons of the observed changes in some astronauts remained unclear. However, factors such as the increase in intracranial pressure and fluid shifts are among the top potential contributing elements. Here we report a study that specifically looked at the effect of space environment on the proliferation and physiology of human Neural Stem Cells (NSCs) onboard the International Space Station (ISS) as compared to ground controls. The study revealed that human NSCs proliferated seven times more while in space (SPC) when compared to on Earth (1G) control cultures. We also examined by continuous live imaging the behavior of space flown NSCs upon return to Earth. We found that after space flight, they continued proliferating at the same pace as 1G controls. Interestingly, NSCs flown to space displayed a larger diameter than control cells. These phenomena, increased proliferation while in space and larger cell soma may contribute to intracranial hypertension found in astronauts, representing a risk factor and potential limitation to long duration space missions such as travelling to the Moon or Mars. In addition, NSCs are essential to maintain Central Nervous System (CNS) function, as they are the basis for the regeneration of CNS cell populations in health and disease.