After hurtling around the planet for nine months, freeze-dried mouse sperm exposed to the harsh environment of space have successfully produced litters of healthy baby mice, researchers report today.
While not entirely surprising to medical experts, the result is good news for those thinking about whether assisted reproductive technologies could be used to make future space babies if and when humans begin populating worlds beyond this one.
Actually having sex in space is a simple Newtonian physics problem that may or may not have already been solved (try getting someone to admit it). The tricky part is that people and animals in space are exposed to both reduced gravity and high-energy cosmic particles that can easily damage genetic material.
A YEAR IN SPACE Astronaut Scott Kelly is sent off into space for one year to test the impact of space travel on the human body.
How the reproductive machinery that turns sperm and eggs into organisms deals with those conditions is a mystery from start to finish, says Kris Lehnhardt, a physician at George Washington University who specialises in emergency and extreme environment medicine.
“We really don’t know any of the things that we need to know to say that human reproduction in space is going to be successful or safe,” he says. “It’s not been studied in much detail.”
The new mouse study, described in the Proceedings of the National Academy of Sciences, not only suggests that space sperm can survive and be viable, but also offers some insight into future fertility.
“It’s a nice, well-designed study,” says Joe Tash of the University of Kansas Medical Center. But astronauts will face an even more intense radiation environment in deep space, which is an important caveat to consider when interpreting the study’s conclusions.
On Earth, everything alive evolved within the framework of gravity and under the protection of the planet’s magnetic field, which deflects most of the high-energy cosmic particles that hurtle through the cosmos. In deep space, on the moon, or even on Mars, gravity is much weaker, and radiation is much more of a danger.
So far, scientists have studied how a handful of organisms reproduce in space, including rats, fish, salamanders, and sea urchins. The results are mixed: Rats didn’t manage to produce pups at all during a 1979 experiment conducted on the Russian Cosmos 1129 satellite. While sea urchin sperm also didn’t do so well, fish, fruit flies, and nematodes successfully reproduced.
With those tidbits in mind, developmental biologist Teruhiko Wakayama, who once wanted to be an astronaut, set out to investigate whether assisted reproductive technologies could eventually be used to make baby mice in space.
“We found that only a few studies were performed about mammalian reproduction in space, and most of them showed no clear results due to the difficulty of taking the mice or rat into space,” says Wakayama, of Japan’s University of Yamanashi.
Wakayama specialises in domestic animal reproduction and has previously shown that freeze-drying mouse sperm could produce normal mouse pups on Earth. But when he and his colleagues stored mouse sperm in a chamber that simulated microgravity, it didn’t produce as many pups as expected.
“We very much wanted to perform a real space experiment,” Wakayama says. So the team designed an experiment, nicknamed Space Pup, to test the effects of actual space travel on mouse sperm cells.
After extracting spermatozoa from several mice, the team freeze-dried the cells and sent them to the International Space Station in August 2013. Freeze-drying helped the sperm stay stable during the several days surrounding their rocket ride into Earth orbit.
Header Image: These baby mice were born from sperm flown aboard the International Space Station for about nine months. PHOTOGRAPH BY TERUHIKO WAKAYAMA