Experimental Treatment Kept Muscle on ‘Mighty Mice’ in Space

By Bryan Lynn
09 September 2020

Scientists say an experimental treatment helped "mighty mice" keep healthy muscle mass during a recent stay in space of one month.

The treatment might one day prevent muscle and bone loss in astronauts during long periods in space. It could also be used to treat people suffering muscle or bone loss on Earth.

Astronauts in space live in an environment of microgravity, or weightlessness. This environment can cause muscles and bones to weaken and lose mass over time.

The U.S. space agency NASA has developed specialized exercise programs for astronauts living on the International Space Station. The goal of the exercises is to limit muscle and bone loss.

But such programs are likely to be ineffective during very long space missions planned by NASA for the future, such as extended stays on the moon or Mars. The "Mighty Mice in Space" experiment was created to test a possible preventive treatment for muscle and bone loss during long space missions.

The project involved 40 female mice that were launched into space on a SpaceX rocket last December. The animals lived on the International Space Station for 33 days before returning to Earth in January.

Sixteen mice were given the experimental treatment, which involved a genetic engineering method. Researchers removed a gene responsible for producing myostatin, a protein that controls and can limit the growth of muscles and bone.

The mice that lacked the myostatin gene – the so-called mighty mice – showed muscle growth during the experiment.

Eight of these mice had at least twice the muscle mass of the untreated mice before being sent to space. The researchers said during their stay on the space station, these mice kept their muscle mass. Their muscles appeared very similar to the other mighty mice kept back on Earth at NASA's Kennedy Space Center.

The 24 mice that did not get the treatment lost a lot of muscle and bone mass in space, the researchers reported. Those mice lost between eight and 18 percent of weight in individual muscles compared to the mice on Earth. They also lost up to 11 percent of bone mineral density - a measure of bone strength.

Eight of the mice received another compound from astronauts on the space station. That compound has been found to block a protein that limits muscle and bone growth. The mice given this treatment in space gained 27 percent lean body weight, compared to 18 percent in mice on the ground. The mice receiving the compound – both in space and on the ground – also had increases in bone mineral density, the researchers found.

Some of the untreated mice were given the treatments after returning to earth. They quickly built up more muscle than untreated mice in the laboratory, the researchers reported.

The research was led by a team from the Jackson Laboratory, a nonprofit biomedical research center based in Bar Harbor, Maine. Results recently appeared in a study published in Proceedings of the National Academy of Sciences.

Jackson Laboratory's Dr. Se-Jin Lee was the lead writer of the study. He told The Associated Press the experiment identified additional molecules and signaling pathways relating to muscle and bone loss that could use more investigating. He said he would also like to send more "mighty mice" to the space station for additional study.

Lee's wife, Emily Germain-Lee of Connecticut Children's Medical Center, also took part in the study. While excited by the findings, she told the AP much more work is needed before the treatment can be tested on humans to build up muscle and bone.

"We're years away. But that's how everything is when you go from mouse to human studies," Germain-Lee said.

I'm Bryan Lynn.

Bryan Lynn wrote this story for VOA Learning English, based on reports from the Jackson Laboratory, The Associated Press, NASA and Proceedings of the National Academy of Sciences. Mario Ritter was the editor.

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Words in This Story

mighty – adj. very large, powerful or important

mission – n. an important task, usually involving travel somewhere

lean – adj. thin and healthy