Spaceflight results in reduced mRNA levels for tissue-specific proteins in the musculoskeletal system.
The purpose of the present study in growing rats was to investigate the effects of short-term spaceflight on gene expression in bone and muscle and on cortical bone histomorphometry. Two experiments were carried out; Physiological Systems Experiments 1 and 2 were 4- and 10-day flights, respectively. Radial bone growth in the humerus was unchanged during the 4-day flight and decreased during the 10-day flight. Expression of mRNA for glyceraldehyde-3-phosphate dehydrogenase was unchanged in biceps, calvarial periosteum, and long-bone periosteum after spaceflight. Similarly, no changes in ribosomal RNA levels were observed in long-bone or calvarial periosteum after spaceflight. In contrast, spaceflight decreased steady-state mRNA levels for actin in muscle (4-day flight). Osteocalcin (both spaceflights) and the prepro-alpha 2[I] chain of type I precollagen (10-day flight) mRNA levels were decreased in long-bone and calvarial periosteum after spaceflight. These results indicate that the effects of spaceflight on the musculoskeletal system include decreased expression of some muscle- and bone-specific genes as well as decreased bone formation. Interestingly, detectable reductions in gene expression for bone matrix proteins preceded histological evidence for decreased bone formation.
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Department of Orthopedic Surgery and Biochemistry, Mayo Graduate School, Rochester, Minnesota 55905.
Westerlind
K
K
Harris
S
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Spelsberg
T
T
Kline
B
B
Turner
R
R
D000199:Actins / Q000235:genetics*; D000818:Animals; D015152:Blotting, Northern; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism*; D003094:Collagen / Q000235:genetics*; D008297:Male; D009132:Muscles / Q000378:metabolism*; D009141:Musculoskeletal System; D015675:Osteocalcin / Q000235:genetics*; D010012:Osteogenesis; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013026:Space Flight
D000199:Actins; D012333:RNA, Messenger; D015675:Osteocalcin; D003094:Collagen