MCB Seminar | Effects of Gravitational Changes on the Bone System, March 16

Shiyu Yuan

The Molecular and Cellular Biology Seminar series features Shiyu Yuan discussing “Effects of Gravitational Changes on the Bone System” on March 16 from 4:35 – 5:55 p.m.

• Contact Dr. Sarah Wyatt, MCB director, for Teams information.

Yuan is a graduate student in Biological Sciences at Ohio University and a member of the Molecular and Cellular Biology program.

Abstract: Bones are not unchanging calcium structures; they constantly reshape themselves in relation to the stress that is put on them. Long-term exposure of microgravity (μG) by spaceflight and bed rest on the ground result in severe osteoporosis whereas mechanical loading by exercise recovers the bone mass¹. Thus, mechanical force plays a critical role in bone metabolism. Bone metabolism is precisely maintained by the balance between osteoclastic bone resorption and new bone formation by osteoblasts. Osteoclast is a multi-nuclear giant cell differentiated from macrophage lineage cells and possesses the bone-resorbing activity, while osteoblast controls bone formation and mineralization. Studies showed that short-term period (18–22 days) of exposure to microgravity affects skeletal tissue dynamics in rat aboard different space flights. These experiments revealed a reduced osteogenesis and new bone apposition in the weight-bearing bones (femurs and tibiae). Moreover, the rate of osteoid maturation and the degree of mineralization in these bones was diminished². The bone growth reduction could be associated with a failure of differentiation of osteoprogenitor cells and their conversion to osteoblasts. On the other hand, Tominari et al. reported that artificial produced 2G hypergravity on mice for 2 weeks elevated the bone mass including humerus, femur, tibia and calvaria by the increased expression of osteogenic genes in mice³. The study of how bone tis-sue responds to gravity variations is essential, not only for space flight effect research but, more than ever, in our contemporary ageing society in which bone pathologies become a ma-jor medical problem in the most elderly people.