Three space mice have lots to share about astronaut health

A group of mice spent a record-breaking 91 days aboard the International Space Station. Here's a collection of what they can teach us, which includes aging, sperm production, and bone loss.
Written by Janet Fang, Contributor

As part of the Mice Drawer System Experiment, a group of 3 mice spent a record-breaking 91 days aboard the International Space Station… and lived to tell about it.

What they experienced can help us understand the effects of long-term space travel on the human body, according to a collection of PLoS studies. New Scientist reports.

On aging:

The thyroid produces hormones that control metabolism. Aging slows thyroid function, leading to impaired cognition and weight gain.

Earthbound mice have smaller follicles in the middle of their thyroids and larger ones around the edge. The follicles in the space mice, however, were all the same size. And they also had more receptors for a thyroid-stimulating hormone, suggesting they maintained a higher level of thyroid activity in adulthood.

So space flight seems to slow thyroid aging, and figuring this out could possibly help maintain thyroid function on Earth.

On blood:

Astronauts with a condition called space flight anemia have a 10 percent drop in their number of red blood cells and volume of plasma. Cells exposed to radiation produce chemicals that damage fat, protein, and DNA. One of the byproducts of those chemicals is called ‘thiobarbituric acid reactive substances’ (TBARS).

The level of TBARS in the space mice’s red blood cells were significantly higher than in mice back home.

Antioxidants can help undo some damage by donating an electron to the reactive chemical, suggesting that an antioxidant-rich diet may help counter some of the adverse effects of radiation in space.

On sperm:

Reproductive organs are particularly vulnerable to radiation in space, especially if there’s a solar flare. Additionally, without earth’s gravity, the testes are a lot closer to the body where it’s a lot warmer, interfering with sperm production.

The number of sperm present in the testes of space mice dropped by about 90 percent, though the mice did retain a limited ability to make mature sperm.

Male astronauts should be offered the option to preserve healthy semen samples before they go into space, researchers suggest.

On muscles:

Suspended in microgravity, astronauts don’t get to stretch their legs, leading to muscle loss. Slow-twitch muscles, which help maintain posture, are particularly vulnerable.

The space mice lost a similar amount of slow-twitch muscle fiber as did mice on shorter missions. It seems that there’re initial changes due to stress and microgravity, but then the situation stabilizes.

Fast-twitch muscles, for short bursts of power, were somehow unaffected. Once researchers have figured out how, they hope to offer similar protection for slow-twitch muscles.

On bones:

In microgravity, weight-bearing bones gradually break down without being rebuilt, as they would be on Earth.

To avoid this, researchers altered the genes of some of the space mice, giving them an extra protein for bone development. The modified mice lost just 3 percent of the bone mass in their spines, compared with a 41.5 percent loss in the other mice.

A similar protein might help protect astronauts. (Read more on space mice and bone health in my post from earlier this year.)

All these studies can be found in PLoS ONE.

[Via New Scientist]

Image: Lizzy Parisotto

This post was originally published on Smartplanet.com

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