‘Mighty mice’ given experimental drug built muscle while orbiting on the ISS

One of the biggest challenges for astronauts on long-haul space flights will be muscle wastage – our bodies have evolved to work in Earth’s gravity and in the weightless environment of interplanetary space muscles and bones left with little to do will waste away.

But in an experiment on the International Space Station mice injected with a new muscle-building drug actually gained muscle and bone mass during their month in orbit.

They were given an injection of a new compound that blocks the growth-limiting protein myostatin before takeoff, and then once a week as long as they were on the ISS.

The experimental subjects’ muscle and bone mass increased by around 20% while a group of unlucky mice who weren’t given the drug in orbit, muscle mass decreased by 10%.

When mice that hadn’t been given the drug returned to Earth they were given a dose of the drug and rapidly started gaining muscle.

Some of the mice involved in the experiment been were genetically engineered to produce less myostatin so they had twice the average muscle mass to start with. They were nicknamed "mighty mice" by the research team.

Emily Germain-Lee, one of the researchers at the University of Connecticut involved in developing the treatment, says it’s not just useful for astronauts.

"It could help any condition, any prolonged illness, in which someone is bedridden," she told New Scientist.

She says that the mice were "surprisingly resilient" when it came to adjusting to the stresses of space travel: "We knew that mice had been sent to space in the past, but we still found it remarkable that after spending a month at the ISS, they seemed to resume normal activity very quickly after returning to Earth."

The treatment will be essential for the next stage of manned space flight.

With a journey to Mars taking anything from six months to a year and the Red Planet’s gravity being only 38% of Earth’s, muscle and bone loss will represent a serious challenge.

A version of the drug that’s suitable for humans is already in development, but early trials had to be halted because it produces some unwelcome side-effects including severe nosebleeds.

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