title: Altered skeletal pattern of gene expression in response to spaceflight and hindlimb elevation.
abstract: Spaceflight leads to osteopenia, in part by inhibiting bone formation. Using an animal model (hindlimb elevation) that simulates the weightlessness of spaceflight, we and others showed a reversible inhibition of bone formation and bone mineralization. In this study, we have measured the mRNA levels of insulin-like growth factor I (IGF-I), IGF-I receptor (IGF-IR), alkaline phosphatase, and osteocalcin in the tibiae of rats flown aboard National Aeronautics and Space Administration Shuttle Flight STS-54 and compared the results with those obtained from their ground-based controls and from the bones of hindlimb-elevated animals. Spaceflight and hindlimb elevation transiently increase the mRNA levels for IGF-I, IGF-IR, and alkaline phosphatase but decrease the mRNA levels for osteocalcin. The changes in osteocalcin and alkaline phosphatase mRNA levels are consistent with a shift toward decreased maturation, whereas the rise in IGF-I and IGF-IR mRNA levels may indicate a compensatory response to the fall in bone formation. We conclude that skeletal unloading during spaceflight or hindlimb elevation resets the pattern of gene expression in the osteoblast, giving it a less mature profile.
authors: Department of Medicine, University of California, San Francisco.
authors: D D
authors: DD
authors: Bikle
authors: J
authors: J
authors: Harris
authors: B P
authors: BP
authors: Halloran
authors: E
authors: E
authors: Morey-Holton
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics; D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D008297:Male; D015675:Osteocalcin / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000235:genetics; D013026:Space Flight; D014893:Weightlessness
chemical_list: D012333:RNA, Messenger; D015675:Osteocalcin; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D000469:Alkaline Phosphatase