Osteoporosis experiment will go up in final space shuttle mission

As part of an experiment related to progressive bone loss and osteoporosis, 30 mice are slated to be aboard the final space shuttle mission scheduled by the National Aeronautics and Space Administration (NASA).

Designed by researchers at the University of North Carolina at Chapel Hill and North Carolina State University, the test aims to determine what, if anything, can halt the steady loss of muscular and skeletal tissue during prolonged exposure to weightlessness.

The outcome of this experiment may affect the course of osteoporosis research, as well as impact future manned missions to Mars.



The problem with experiencing zero gravity is that, over time, an individual puts relatively little pressure on their muscles and bones, far less than they would on terra firma. This lack of physical strain leads to muscular atrophy and sometimes radical bone loss.



Currently, NASA astronauts aboard the International Space Station engage in extensive daily exercises as a may to mitigate the gradual reduction of bone tissue, but this regimen, intense as it may be, still does not totally prevent bone loss in space.

Back on Earth, individuals with osteoporosis often experience a similar issue. Progressive bone loss increases the risk of fracture, sometimes to a considerable degree. In the U.S., osteoporosis contributes to more than 2 million broken bones each year, according to the National Osteoporosis Foundation (NOF). These fractures often limit mobility, which can in turn increase the rate of bone loss.

Essentially, individuals who cannot walk, exercise or otherwise make use of their bones and muscles lose bone mass due to inactivity. This is one reason why the NOF strongly recommends that people with osteoporosis regularly engage in weight-bearing fitness routines.

In the experiment scheduled to be carried out aboard the space shuttle Atlantis, researchers will monitor how weightlessness affects the proteins created by osteocytes, which are bone-based cells that control mineral density based on the loads the the skeleton bears.

The team said that they expect to see high levels of sclerostin, a molecule that inhibits bone growth, in the mice on their return.

However, one-half of the rodents have been given an antibody to block the production of sclerostin. Scientists said that, with luck, those mice given what amounts to an inoculation against bone loss may return to Earth with relatively little bone loss.

The average person acquires up to 90 percent of their adult bone mass by age 20, according to the NOF. After that, individuals tend to lose bone density at a rate of about 1 percent each year, though unhealthy individuals may experience much faster decline.

By contrast, astronauts can experience a 1 to 2 percent total bone loss for each successive month they spend in orbit.

"On extended missions, beyond six months up to three years, such as on a Mars mission, this loss is going to be substantial," said team leader Ted Bateman. He concluded that this experiment may have significant consequences in the fields of spaceflight and earthbound osteoporosis research alike.
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