Cessation of cyclic stretch induces atrophy of C2C12 myotubes

QA Soltow, EH Zeanah, VA Lira, DS Criswell - Biochemical and biophysical …, 2013 - Elsevier
QA Soltow, EH Zeanah, VA Lira, DS Criswell
Biochemical and biophysical research communications, 2013Elsevier
Cyclic stretch of differentiated myotubes mimics the loading pattern of mature skeletal
muscle. We tested a cell culture model of disuse atrophy by the cessation of repetitive bouts
of cyclic stretch in differentiated C2C12 myotubes. Myotubes were subjected to cyclic strain
(12%, 0.7 Hz, 1h/d) on collagen-I-coated Bioflex plates using a computer-controlled vacuum
stretch apparatus (Flexcell Int.) for 2 (2dSTR) or 5 (5dSTR) consecutive days. Control
cultures were maintained in the Bioflex plates without cyclic stretch for 2d or 5d. Additionally …
Cyclic stretch of differentiated myotubes mimics the loading pattern of mature skeletal muscle. We tested a cell culture model of disuse atrophy by the cessation of repetitive bouts of cyclic stretch in differentiated C2C12 myotubes. Myotubes were subjected to cyclic strain (12%, 0.7Hz, 1h/d) on collagen-I-coated Bioflex plates using a computer-controlled vacuum stretch apparatus (Flexcell Int.) for 2 (2dSTR) or 5 (5dSTR) consecutive days. Control cultures were maintained in the Bioflex plates without cyclic stretch for 2d or 5d. Additionally, some cultures were stretched for 2d followed by cessation of stretch for 3d (2dSTR3dCES). Cyclic stretching (5dSTR) increased myotube diameter and overall myotube area by ∼2-fold (P<0.05) compared to non-stretched controls, while cessation of stretch (2dSTR3dCES) resulted in ∼80% smaller myotubes than 5dSTR cells, and 40–50% smaller than non-stretched controls (P<0.05). Further, the calpain-dependent cleavage products of αII-spectrin (150kDa) and talin increased (3.5-fold and 2.2-fold, respectively; P<0.05) in 2dSTR3dCES myotubes, compared to non-stretched controls. The 1h cyclic stretching protocol acutely increased the phosphorylation of Akt (+4.5-fold; P<0.05) and its downstream targets, FOXO3a (+4.2-fold; P<0.05) and GSK-3β (+1.8-fold; P<0.05), which returned to baseline by 48h after cessation of stretch. Additionally, nitric oxide production increased during stretch and co-treatment with the NOS inhibitor, l-NAME, inhibited the effects of stretch and cessation of stretch. We conclude that cessation of cyclic stretching causes myotube atrophy by activating calpains and decreasing activation of Akt. Stretch-induced myotube growth, as well as activation of atrophy signaling with cessation of stretch, are dependent on NOS activity.
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