Sperm from Space is Viable

Mice conceived using sperm flown in space are healthy and have normal fertility themselves, Japanese scientists have announced this week.

Despite exposure to cosmic radiation 100 times higher than control samples left on earth, mouse sperm that spent 288 days aboard the International Space Station (ISS) between August 2013 and May 2014 was capable of forming viable embroys that grew into healthy pups.

The study adds to the list of animals that have had their sperm flown in orbit to test its ability to withstand the harsh environment in space. Previously salamanders, sea urchins, fish and birds had been studied, but not mammalian tissue. 

The work, which is published this week in the journal PNAS, was carried out by University of Yamanashi researcher Teruhiko Wakayama and his colleagues.

Prior to their flight aboard the ISS, the mouse sperm cells were freeze dried at -95 degrees celsius; a control sample remained on the ground while the rest of the batch went into space for nine months.

After the sperm were returned Earth, the Japanese scientists thawed out the samples and used a technique called ICSI to microinject individual sperms into mouse eggs.

The fertilisation success rates for the "space" sperm and the "Earth" sperm were equivalent, and the ratio of male to female pups was also the same between the two groups.

Implanted into female mice, the embryos matured and produced healthy mice with normal fertility.

Genetic analysis of sperm showed that they had succumbed to minor DNA damage while aloft although this clearly did not appear to have adversely compromised the integrity of the DNA message. And, as the Japanese team point out, egg cells are extremely good at repairing DNA damage, which may account for the lack of any obvious impact.

The study matters because it shows that mammalian sperm can be flown safely in space without obvious consequences to viability and despite encountering 100 times more radiation that would occur on the Earth's surface, for at least nine months, which is the anticipated duration of a journey to Mars.

According to Wakayama, "Our results demonstrate that generating human or domestic animal offspring from space-preserved spermatozoa is a possibility, which should be useful when the 'space age' arrives."