"This study cuts straight to the bone in terms of why our skeletons deteriorate with disuse," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "As is the case with human intelligence, bone loss is an example of 'use it or lose it.' This study from space has pinpointed the cellular culprits that destroy our bones when we don't use them to support weight."

Using two sets of bone-destroying cells, called "osteoclasts," obtained from the bone marrow of mice femurs, the scientists launched one set into space via the European Space Agency's 2007 FOTON-M3 mission and kept the other set on Earth. On the satellite, the cells were maintained in custom-designed bioreactors equipped with automatic nutrient providers. At the same time, the other set of cells were kept in the same type of bioreactors on the Earth's surface. After twelve days, the experiment was stopped and the cells were examined. The analysis revealed an increase in genes involved in osteoclast maturation and activity, as well as increased bone loss when compared to the cells on Earth.

"Space might be the final frontier, but we've got some serious hurdles to clear before we conquer microgravity, and bone loss is one of them," Weissmann added. "Even here on Earth, we all face bone loss. Osteoporosis inexorably hits men and women alike, and this European study points to one cause: lack of resistance."

According to NASA, an astronaut could lose as much as 10 to 15 percent of pre-flight bone mass after only six months in space. The National Osteoporosis Foundation reports that at least 25 million people in the United States suffer from bone loss.

Note: If no author is given, the source is cited instead.

• Osteoporosis
• Bone and Spine
• Leukemia
• Women's Health
• Stem Cells
• Menopause

• Bone
• Human skeleton
• Bone marrow
• Bone age
• Natural killer cell
• Osteoporosis