Genetically Engineered Ripped Mice Offer Clues To Maintaining Muscles In Space

Gene-tweaked Might Mouse (right) and a typical mouse (left).  An image from a previous study by Se-Jin Lee, the lead author of the freshly published research. Se-Jin Lee/PLOS One/2007 CC Y 2.5

Scientists created muscle-bound mice using gene editing in a quest to see how human astronauts could be protected against muscle and bone density loss in the absence of gravity in space. Having landing back to Earth after a brief stint on the International Space Station (ISS), the buff mice are now helping scientists figure out how people might be able to stay fit and strong in microgravity using a key pathway that deals with muscle growth. 

Spending time in microgravity can seriously mess with your muscles and bones. Even though astronauts work out for an average of two hours per day to counteract this, they can still lose 40 percent of their muscle after five months in space. They also lose about 1 to 2 percent of bone tissue each month. Thanks to this new study, published in the journal Proceedings of the National Academy of Sciences, researchers have edged closer to understanding how we could avoid this undesirable side effect. 

For the new research, the team used so-called Mighty Mice that were genetically engineered to lack myostatin, a protein that inhibits muscle cell growth, resulting in them having around twice the muscle mass of an average lab mouse. 

The team from the University of Connecticut School of Medicine and NASA, led by Se-Jin Lee, blasted off around 40 mice to the ISS in December last year, where they stayed for 33 days in microgravity. Twenty-four of the mice were typical lab mice, eight were Mighty Mice missing the myostatin gene, and eight others were treated with a molecule that suppressed both myostatin and a protein known as activin A, which also regulates the growth of both muscle and bone.

Typical mouse (left) and gene-tweaked Mighty Mouse (right). An image from a previous study by Se-Jin Lee, the lead author of the new research. Se-Jin Lee/PLOS One/2007 CC BY 2.5

Once the mice were back home on Earth, the researchers studied how much muscle they lost after just over a month in microgravity living alongside astronauts on the ISS. The normal mice lost a significant amount of muscle and bone mass, while the genetically edited “Might Mice” largely retained their muscles during spaceflight. Furthermore, the mice that received the molecule suppressing myostatin and activin A saw “dramatic increases”  in both muscle and bone mass.

The key finding here is that muscle and bone mass in microgravity can be managed by targeting the signaling pathway that deals with myostatin and activin A. The study also indicates that this could potentially be done through some kind of drug. Of course, this is just an animal study at the moment and the results might not necessarily translate to humans. Nevertheless, muscle loss in microgravity is an important hurdle if astronauts are going to embark on longer voyages, such as landing humans on Mars. 

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