Freeze-dried mouse sperm survived in Space for 6 years and is now being used to conceive pups. Successful experiment, baby mice are all healthy
Healthy baby mice were born from freeze-dried mouse sperm that orbited in space for nearly 6 years aboard the International Space Station. That's what was revealed in a new study by Japanese researchers, published in Science Advances, which explains how positive the result is, given that DNA-damaging radiation on the Iss is 100 times stronger than on Earth. The paper's authors wrote that "examining the effects of space radiation" is important "even for future generations before the space age arrives." If human sperm were just as resilient in space and if Earth were to become unlivable in the future, then, freeze-dried liquid could potentially play a role in repopulating space colonies.
The study on mouse sperm sent into space
At the heart of the research would be concerns about mutations in offspring after space exploration. Researchers are trying to figure out whether space radiation can damage the DNA of mammals and other animals, thus making it impossible for humanity to reproduce and keep alive. Japanese scientists freeze-dried mouse sperm using a technique that allowed it to be stored at room temperature for more than a year. This allowed the team to launch the substance on the Iss without the need for a freezer.
This also kept costs down because the sperm was stored in small, lightweight vials. The sperm were sent to the Iss in August 2013, and only once they arrived did the astronauts store them in a freezer at minus 139 degrees Fahrenheit, or -95°C. Some samples then came back after nine months, others after two years and nine months, and the last one came back after five years and 10 months. In a paper published in 2017 in the Proceedings of the National Academy of Sciences, the researchers reported that there was slightly more damage to sperm DNA and male gamete nuclei after nine months, but fertilization and birth rates were similar to the healthy version.
In the new study, the researchers used so-called "plastic nuclear track detectors," devices made of polymers that are sensitive to charged particles, and "thermoluminescent dosimetry," which absorbs and traps radiation energy, to figure out how much radiation the sperm absorbs. So they tested the amount of damage to the sperm's DNA, finding that long-term storage aboard the Iss did not result in significant defects.
After rehydration, the fluid was used to fertilize female specimens, which then gave birth to eight healthy pups. The researchers also noted that although there are differences in DNA damage caused by X-rays versus space radiation, they estimate that freeze-dried mouse sperm can be stored on the Iss for more than 200 years before becoming non-viable. It now remains to be seen how the results would translate into human embryos.
In the meantime, after the mouse sperm, 128 small bioluminescent squids are also preparing to be sent into space, which will be part of an experiment on life in space.