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Muscle disuse atrophy is not accompanied by changes in skeletal muscle satellite cell content
Snijders, Tim Wall, Benjamin T. Dirks, Marlou L. Senden, Joan M. G. Hartgens, Fred Dolmans, John Losen, Mario Verdijk, Lex B. van Loon, Luc J. C.
Snijders, Tim
Wall, Benjamin T.
Dirks, Marlou L.
Senden, Joan M. G.
Hartgens, Fred
Dolmans, John
Losen, Mario
Verdijk, Lex B.
van Loon, Luc J. C.
Abstract
Muscle disuse leads to a considerable loss in skeletal muscle mass and strength. However, the cellular mechanisms underlying disuse-induced muscle fibre atrophy remain to be elucidated. Therefore we assessed the effect of muscle disuse on the CSA (cross-sectional area), muscle fibre size, satellite cell content and associated myocellular signalling pathways of the quadriceps muscle. A total of 12 healthy young (24±1 years of age) men were subjected to 2 weeks of one-legged knee immobilization via a full-leg cast. Before and immediately after the immobilization period and after 6 weeks of natural rehabilitation, muscle strength [1RM (one-repetition maximum)], muscle CSA [single slice CT (computed tomography) scan] and muscle fibre type characteristics (muscle biopsies) were assessed. Protein and/or mRNA expression of key genes [i.e. MYOD (myogenic differentiation), MYOG(myogenin) and MSTN (myostatin)] in the satellite cell regulatory pathways were determined using Western blotting and RT-PCR (real-time PCR) analyses respectively. The present study found that quadriceps CSA declined following immobilization by 8±2% (P < 0.05). In agreement, both type I and type II muscle fibre size decreased 7±3% and 13±4% respectively (P < 0.05). No changes were observed in satellite cell content following immobilization in either type I or type II muscle fibres. Muscle MYOG mRNA expression doubled (P < 0.05), whereas MSTN protein expression decreased 30±9% (P < 0.05) following immobilization. Muscle mass and strength returned to the baseline values within 6 weeks of recovery without any specific rehabilitative programme. In conclusion, 2 weeks of muscle disuse leads to considerable loss in skeletal muscle mass and strength. The loss in muscle mass was attributed to both type I and type II muscle fibre atrophy, and was not accompanied by a decline in satellite cell content.
Keywords
disuse atrophy, immobilization, muscle stem cell, myostatin, quadriceps muscle
Date
2014
Type
Journal article
Journal
Clinical Science
Book
Volume
126
Issue
8
Page Range
557-566
Article Number
ACU Department
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Open Access Status
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Controlled