21.10.2019

A mouse kept at the International Space Station (Provided by the Japan Aerospace Exploration Agency)

Male mice kept in outer space in special cages can retain their ability to breed, according to a study that could provide a sense of comfort to astronauts on extended stays far from Earth.

“As there is an increasingly real prospect of space travel, the discovery will help ease the feeling of anxiety about a risk of becoming unable to have offspring after such travel,” said Masahito Ikawa, a reproductive biology professor at Osaka University.

A team of scientists primarily from Osaka University, including Ikawa, discovered that the sperm of mice kept outside Earth can fertilize ova, and the offspring are as healthy as those that have never stayed in outer space.

The impact of exposure to the cosmic environment on an animal’s breeding performance has long been a mystery.

In outer space, gravity-free conditions, radiation and psychological stress are believed to exert an influence on a creature’s body, but the actual effects have not been ascertained.

The key to the latest experiment’s success was a special container created by the Japan Aerospace Exploration Agency (JAXA).

The JAXA box solved another problem: survival.

Scientists from Italy, Russia and elsewhere have tried to raise mice in space. But their projects have failed to keep all tested mice alive upon their return to Earth after at least a month in space.

The JAXA boxes allow the animals inside to drink water and eat food whenever they like.

In gravity-free conditions, feces and urine float in the air, creating an unhygienic environment. In the boxes, the excrement is blown to the walls to keep the atmosphere clean.

While each cage accommodates one mouse, the containers were arranged so that neighboring rodents could see one another to give them a sense of security. Each unit was equipped with a camera, enabling staff and veterinarians on Earth to check the mice’s conditions.

The research team devised a plan to keep six mice in an almost no-gravity environment and another six in a place where the gravity level is around the same as that on Earth.

The 12 male mice were launched aboard U.S.-based Space Exploration Technologies Corp.’s Falcon 9 rocket from NASA’s John F. Kennedy Space Center in Florida on July 18, 2016. They were carried to the International Space Station (ISS) by the Dragon resupply spacecraft.

After a 35-day stay on the ISS, the mice were sent back aboard a supply spacecraft on Aug. 26, and all 12 arrived safely in waters off Los Angeles.

The scientists collected and froze the mice’s sperm within around two days of their return. Production of sperm cells in the body requires 30 days, so the sampled sperm were highly likely generated in space.

Analyzing the shapes of the sperm, DNA damage and breeding ratio through in vitro fertilization, the researchers found that the space mice’s breeding performance was as high as that of their counterparts raised on Earth.

“Though the effects on female mice and other elements need to be surveyed as the next step, the research has provided important findings as human beings expand their activities to outer space,” Ikawa said.

Quelle: The Asahi Shimbun