A group of mice have returned to Earth after a record-breaking 91-day mission. They were part of a project to learn more about the deterioration of bone in zero gravity, but the findings could also help those suffering from osteoporosis here on Earth.
Astronauts can lose over a fifth of their bone weight whilst in space. This is because cells that break down bone, as part of the continuous remodelling process that occurs in all our bodies, become more active when there is no impact on the bone. This occurs in zero gravity but also in people who are bed-ridden, who may then develop osteoporosis.
Scientists sent six mice to the International Space Station to test whether pleiotrophin (PTN), a bone growth factor, would protect bones from deterioration. Three of the six mice were genetically engineered to produce more PTN. All the mice showed loss of bone density in their spine compared with the control mice that stayed on Earth, but the ones with extra PTN lost only 3% whilst the normal mice lost 41.5%.
The mission was the longest time ever spent in space by an animal (apart from humans) and allowed scientists to test specially designed modules for housing mice in orbit. Although only a small study with a few animals, these results suggest that PTN might be an important factor in the loss of bone strength due to inactivity. It also shows that mice in zero gravity could be a useful and accurate way of replicating the effects of osteoporosis, which could help future studies to find new ways of treating the condition, perhaps even using PTN.