A microscope image of mouse embryos after they had returned from the International Space Station
Teruhiko Wakayama/University of Yamanashi
Mouse embryos have been cultured on the International Space Station (ISS) for the first time to explore whether it might be safe for humans to become pregnant in space.
“There is a possibility of pregnancy during a future trip to Mars because it will take more than 6 months to travel there,” says Teruhiko Wakayama at the University of Yamanashi in Japan, who led the study. “We are conducting research to ensure we will be able to safely have children if that time comes.”
Wakayama and his colleagues performed the first steps of the experiment in their lab on Earth, extracting embryos that were at an early two-cell stage from pregnant mice and freezing them.
The frozen embryos were sent to the ISS on a SpaceX rocket that launched from Florida in August 2021. They were stored inside special devices that Wakayama’s team designed so that astronauts on the station could easily thaw the embryos and culture them for 4 days. The astronauts then chemically preserved the embryos and sent them back to Earth on a return vessel.
The embryos were only grown for four days because they can only survive for that length of time outside a uterus, says Wakayama.
His team studied the returned embryos to see if their development had been affected by their exposure to the higher radiation and low gravity – known as microgravity – in space.
The embryos didn’t show signs of DNA damage from the radiation exposure, possibly because they were only in space for a short time.
They also displayed normal structural development, including differentiation into two groups of cells that form the basis of the fetus and placenta. This was an important finding because it was previously thought that microgravity may affect the ability of embryos to separate into these two different cell types, says Wakayama.
It is unclear whether later stages of embryo development would be disrupted by being in space, but a previous study that sent pregnant rats on NASA spaceflights for 9 to 11 days during the second halves of their pregnancies found they gave birth to typical-weight pups when they came back to Earth, hinting the pups had developed normally.
“Based on [this] and our results, perhaps mammalian space reproduction is possible,” says Wakayama.
However, it is still unknown whether the actual delivery of a mouse pup or human baby at full term would be difficult under microgravity conditions, he says.
His team now plans to test whether mouse embryos that have been sent to the ISS and then returned to Earth can implant in female mice and develop into healthy offspring, as this will provide further clues about the viability of embryos exposed to space radiation and microgravity. The researchers would also like to test whether mouse sperm and eggs sent to the ISS can be used to create embryos via IVF in space.
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