UCSF scientists have determined that the quality of bone matrix, a key component of bone, is regulated by a molecule known as transforming growth factor beta. The finding, they say, suggests a possible target for preventing and treating bone fractures associated with aging and genetic diseases. The study will be reported later this week in the Online Early Edition of Proceedings of the National Academy of Sciences (PNAS). The ability of bone to resist damage depends on the mass, or quantity, of bone, its architecture and the quality of bone matrix, the mineralized material between cells. Several molecular factors have been shown to regulate the mass and architecture of bone. So far, however, none have been shown to regulate bone matrix, which is responsible for bone elasticity and toughness. There has been significant disagreement about whether the quality of bone matrix varies among individuals and, if it does, whether it could be altered for therapeutic reasons. In any case, until now, scientists have lacked a strategy for measuring its quality and teasing out its impact, says senior study author Tamara Alliston, PhD, UCSF assistant adjunct professor of Cell and Tissue Biology.