About Bones In Space

The laboratory of cell growth has performed a number of studies which investigated the effect of microgravity conditions on mammalian cell function. Dr Millie Hughes-Fulford, the laboratory director flew as a payload specialist on STS-40, the first Spacelab mission dedicated entirely to space life sciences research in 1991. 

The laboratory investigated osteoblast growth activation in microgravity, in a series of experiments in the Biorack facility onboard the Space Shuttle. Osteoblasts are cells responsible for maintaining bone growth. During spaceflight astronauts steadily loose bone mass, which could be a serious obstacle to a very long duration mission such as a voyage to Mars. Furthermore, bone mass is lost during ageing eventually resulting in brittle bones susceptible to fracture (osteoporosis). Therefore, understanding the mechanisms of bone loss under microgravity is important for both long term space exploration and osteoporosis. 

The laboratory experiments on osteoblast growth under microgravity are described in detail here:

The Osteo Patch
Background: Astronauts lose bone during spaceflight 
Why do experiments in space?
Experimenting in Space
Understanding and Combatting Osteoporosis