The average daily radiation dose on the International Space Station (ISS) is about 100 times stronger than that on Earth, and the effect of this radiation on germ cells could pose serious reproductive problems for space-dwelling organisms, including humans.

Researchers dispatched samples of freeze-dried mouse spermatozoa to be stored on the ISS for 288 days, from August 2013 to May 2014. Following the samples’ return to Earth, the spermatozoa were compared with control samples preserved on Earth during the same period under similar conditions.

The authors found evidence of slightly increased DNA damage in the space-preserved samples, compared with the control samples.

Embryos fertilized in vitro with sperm from either space-preserved or control samples were transferred into females, and the mean birth rates of pups derived from space-preserved sperm samples were comparable to those of pups derived from control samples. The sex ratio of pups from space-preserved spermatozoa was within the normal range, whole genome analysis revealed only minor differences from control pups, and the pups from space-preserved spermatozoa developed into adults with normal fertility, suggesting that the DNA damage observed in the space-preserved sperm samples was largely repaired in embryos after fertilization.

According to the authors, the results demonstrate the possibility of producing healthy mammalian offspring from spermatozoa preserved in space.

http://www.pnas.org/content/early/2017/05/16/1701425114