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Rat sperm exposed to weightlessness still produces healthy rats

An experiment that flew on ISS has found that rat sperm exposed to weightlessness and space radiation and then used on Earth to fertilize eggs still produce healthy rats.

The first issue for the researchers was how best to get the sperm up there. They decided to have the samples freeze-dried, just like instant coffee. This meant the sperm weighed almost nothing and could be kept at room temperature, ideal for travel on a rocket, or on a distant planet. The mouse sperm then spent 288 days on the ISS before coming back to Earth to be compared with fresh sperm from the same mice.

First, the scientists analysed how space travel affected the integrity of the DNA within the sperm. We know that high levels of fragmentation of sperm DNA are associated with male infertility. As expected, the scientists discovered that the space sperm had higher amounts of fragmented DNA than the sperm which had stayed on Earth. However, when used to fertilise a mouse egg, the space sperm resulted in a similar number of healthy embryos being generated – and these offspring had the ability to develop into normal, fertile adult mice. A final test the researchers did was to compare the patterns of genes being expressed within the brains of the adult mice. Here, the researchers saw no overall differences and concluded the space sperm was equally capable of generating offspring.

Obviously, this result is encouraging, but we are still a long way from nonchalantly letting women get pregnant and give birth in space. The risks on the child remain too great and are unknown.

In fact, I suspect the first time a child is born and raised in space will be an event that is unplanned.

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