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While billionaires like Jeff Bezos and Elon Musk have been competing to launch themselves into space, scientists have been busy transporting freeze-dried rat sperm across the stars.
In new research published Friday in Science Advances, scientists studying the effects of space radiation on reproduction report that freeze-dried rat sperm survived a nearly six-year journey on the International Space Station without any damage and could eventually last for 200 years in space. . The discovery may not be immediately applicable to civilians looking forward to a trip to space, but researchers believe it could be a stepping stone to understanding the risks of reproduction if humans ever colonize Mars, as SpaceX CEO Elon Musk plans to start by 2020. 2050.
“I read a lot of science fiction books,” Teruhiko Wakayama, a scientist at Yamanashi University in Japan and author of the new study, said in an email. “I took an exam to be an astronaut (I failed of course), and then became a scientist, but I still wanted to include something about space.”
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Space radiation is one of the five major health risks facing humans emerging from planet Earth, particularly in terms of its potential to cause cancer, cardiovascular disease, and cognitive problems. For the short-term exploration missions that astronauts typically embark on today, the doses of space radiation they are exposed to are likely too low to cause reproductive problems.
“But as we move from space exploration to things like building colonies and living in space in the long-term, the doses of space radiation will build up and may manifest as fertility and decreased reproduction,” said Zarana Patel, a prominent tech scientist. and engineering company KBR, Inc. and the contractor for NASA’s Human Research Program, which was not involved in the study.
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Most studies of space radiation and its biological effects to date have been, unexpectedly, conducted on Earth. Astronauts are busy people who do not always have time to conduct complex or advanced experiments, and there is not always a lot of space in space. Live animals or cell cultures that require regular maintenance, especially samples such as sperm that must be kept in freezers, are not kept on the space station for long periods of time. However, it is difficult to reproduce the full force of radioactive ions in space, which is different from radiation on Earth.
“To learn about astrobiology, we have to do real space experiments,” Wakayama said.
So in 2013, Wakayama and his team sent 12 samples of freeze-dried sperm, which can be stored at room temperature, to the International Space Station to study the long-term effects of space radiation on reproduction. The first sperm samples were returned to Earth just nine months later, to make sure everything was intact and working properly. More samples returned after nearly three years, and the final samples were recovered after nearly six years in space.
The returned sperm were thawed and evaluated for DNA damage before being used to produce two generations of “space pups”. There were slight differences in DNA preservation and the resulting offspring rate between 3-year-old and 6-year-old sperm, but both were small enough that the researchers concluded that space radiation did no harm. Healthy mice were born from each set of freeze-dried samples. Wakayama also analyzed the gene expression of each generation and found that there was no difference between the space pups and the control group, which are produced using fresh sperm.
Experts say this is a new finding, although there are caveats that make it difficult to draw conclusions about its relevance to humans.
The International Space Station orbits within Earth’s gravitational field, which means that the radiation is not as strong as in deep space or on the surface of Mars. Sperm are already fortified against space radiation in the freeze-drying process, according to the researchers, who have also conducted experiments on Earth to monitor the effects of the freeze-drying process.
In addition, the study only looked at mature sperm, but scientists have known for decades that radiation affects the entire process of sperm development. And when the sperm landed on the ground to thaw, rehydrate and use it to fertilize female cells, the study used only one type of female rat.
“The diversity of the female’s ability to repair sperm damage is the most important thing,” said Andrew Werbek, a chief scientist at Lawrence Berkeley National Laboratory who has studied radiation and the reproductive system since 1975, and who was not involved in the study. .
In the short term, experts said, the study could draw necessary attention to the potential dangers of space radiation to the reproductive system. Mars needs to be explored before farms are built, and that mission could take two or three years, said Ulric Lauderre, director of the Center for Occupational and Environmental Health at the University of California, Irvine, who was also not involved in the mission. a study. To prepare, experts say an integrated approach to Earth and space research is needed, as both have limitations.
“It’s a very, very small group of elite people, but even so, these are the people who are going to take these risks,” Lauderre said.
While more research is needed to figure out the true risks of space radiation for human reproductive systems, Wakayama hopes the new study may prove that if humans go to Mars one day, other mammals could be brought in through freeze-dried reproductive cells.
“I think the results of our research will give the average person a sense of security about space,” Wakayama said.
When freeze-dried sperm was first launched into space in 2013, Wakayama and his team had been working on the proposal and setup for four years. The entire team cried with joy at the launch event. Wakayama took a video that day and played it regularly to the students.
“I think I’ve watched the movie over 100 times, but every time, it makes me cry.”
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