Table 1.
The effects of culturing conditions and stretching regimes on protein turnover, hypertrophy, and atrophy of myotubes.
| Cells | Stretching parameters | Major effects on protein turnover and myotube hypertrophy | References | ||||
|---|---|---|---|---|---|---|---|
| Culture before stretch | Culture during stretch | Stretching mode | Amplitude | Frequency | Regimen | ||
| Avian primary myoblasts were fused to form myotubes in medium containing 10% horse serum and 5% chicken embryo extract for 72 h | Culture in medium containing 10% horse serum and 5% chicken embryo extract | Radial; static; continuous | 10.80% | NA | 8 and 18 h | Inhibited protein degradation | Vandenburgh and Kaufman, 1980 |
| Avian primary myoblasts were fused to form myotubes in medium containing 10% horse serum and 5% chicken embryo extract for 48 h, and were embedded in collagen gel matrix for several days | Culture in medium containing 10% horse serum and 5% chicken embryo extract | Radial; cyclic; intermittent | 20% | 0.25 HZ | Stretch and relax during a 20 s period followed by a 10 s rest; this pattern is repeated three times, followed by a 30-min rest period. The entire stretching period ranges from hours to days | Inhibited protein synthesis during short-term stretch; elevated protein synthesis and myotube diameter during long-term stretch | Vandenburgh et al., 1989, 1990 |
| Avian primary myoblasts were fused to form myotubes in medium containing 10% horse serum and 5% chicken embryo extract for 48 h, and were embedded in collagen gel matrix for several days | Culture in serum-free medium containing basal medium and bovine serum albumin, as well as different levels of exogenous IGF-1 or insulin | Radial; cyclic; intermittent | 12% | 0.25 HZ | Stretch and relax during a 20 s period followed by a 10 s rest; this pattern is repeated three times, followed by a 30-min rest period. The entire stretching period ranges from hours to days | Elevated protein synthesis during short-term stretch | Perrone et al., 1995 |
| Human skeletal muscle cells (HSkMC) were fused to form myotubes in F12/DMEM medium containing 5% horse serum | Culture in serum-free medium | Radial; cyclic; intermittent | 10 and 20% | 0.25 HZ | Stretch and relax during 20 s followed by a 30 s rest period, this pattern is repeated five times, followed by a 30-min rest period. This cycle continued for a 4 h period followed by a 12 h recovery period. The entire stretching period lasts for 7 days | Elevated protein synthesis | Clarke and Feeback, 1996 |
| C2C12 myoblasts were fused to form myotubes in serum-free medium | Culture in DMEM containing 10% FBS | Radial; cyclic; intermittent | 6.70% | 0.25 HZ | Stretch and relax during a 20 s period followed by a 10 s rest; this pattern is repeated three times, followed by a 30-min rest period. The entire stretching period lasts for 48 h | Elevated protein synthesis | Frenette and Tidball, 1998 |
| C2C12 myoblasts were fused to form myotubes in medium containing 10% horse serum and 1% chicken embryo extract, co-cultured with 4% C3H10T fibroblasts | Culture in serum-free medium | Uniaxial; cyclic; continuous | 7% | Strain rates ranges from 1.4% per second to 70% per second (0.1 −5 HZ) | 1 h | Significantly elevated protein synthesis at rate of 14% per second (1 HZ), inhibited protein synthesis at rate >30% | Clark et al., 2001 |
| C2C12 myoblasts were fused to form myotubes in medium containing 5% horse serum | Culture in serum-free medium containing bovine serum albumin (BSA) | Uniaxial; cyclic; continuous | 10% | 1/6 HZ | 3 days | Elevated myotube diameter | Adachi et al., 2003 |
| C2C12 myoblasts were fused to form myotubes in medium containing 2% horse serum | Culture in medium containing 2% horse serum | Radial; cyclic; intermittent | 12% | 0.7 HZ | Stretched 1 h/d for 5 days (5dSTR) or for 2 days followed by 3 days cessation of stretch (2dSTR3dCES) | Elevated myotube diameter during 5dSTR and inhibited myotube diameter during 2dSTR3dCES | Soltow et al., 2013 |
| C2C12 myoblasts were fused to form myotubes in medium containing 2% horse serum supplemented with insulin | Culture in medium containing 2% horse serum | Radial; cyclic; continuous | 15% | 1 HZ | 6 h | Elevated myotube diameter immediately after stretch and returned to control level after cessation of stretch | Ilaiwy et al., 2016 |
| C2C12 myoblasts were fused to form myotubes in medium containing 2% horse serum | Culture in medium containing 2% horse serum | Uniaxial; cyclic; continuous | (a) 15% (b) 10% (c) 10% (d) 2% (e) 2% |
(a) 1 HZ (b) 1 HZ (c) 0.25 HZ (d) 0.25 HZ (e) 0.25 HZ |
(a) 15 min (b) 1 h (c) 1 h (d) 12 h (e) 24 h |
Increased anabolism at low strain, low frequency for long duration; increased catabolism at high strain, high frequency for intermediate or short duration; | Moustogiannis et al., 2020 |
| L6 myoblasts were fused to form myotubes in medium containing 2% horse serum | Culture in medium containing 2% horse serum | Radial; cyclic; continuous | 18% | 1/6 HZ | 96 h | Elevated protein synthesis | Yamashita-Goto et al., 2002; Goto et al., 2003 |
| C2C12 myoblasts were fused to form 3D cultured myotubes in medium containing 2% horse serum | Culture in medium containing 2% horse serum | Uniaxial; static; continuous | 15% | NA | Continuously increasing load to achieve 15% stretch over 1 h; maintain static 15% stretch for further 2 h | Elevated myotube diameter 21 and 45 h after stretch | Aguilar-Agon et al., 2019 |
| C2C12 myoblasts were fused to form myotubes in medium containing 2% horse serum | Culture in tumor cell conditioned medium (CM) was diluted to 20% in medium containing 2% horse serum | Radial; cyclic; continuous | 6% | 0.5 HZ | 2 daily series of 2 h cyclic stretching, with a 3 h-pause between them | CM culture led to decreased diameter of myotubes and reduced fusion index, which was counteracted by stretching | Baccam et al., 2019 |
| C2C12 myoblasts were fused to form myotubes in medium containing 1% heat-inactivated FBS | Culture in medium containing 2% horse serum and 0.2 μM doxorubicin (DOX) | Radial; static; continuous | 5% | NA | Stretch was started 30 min following the first DOX treatment, lasted for 1 h, and media were replaced with fresh media with or without DOX for a duration of 23 h | DOX inhibited protein synthesis and promoted protein degradation, which was counteracted by stretching | Guigni et al., 2019 |
| Avian primary myoblasts were fused to form myotubes in medium containing 10% horse serum and 5% chicken embryo extract for 96–120 h | Serum-free medium containing varying concentrations of dexamethasone (Dex) | Radial; cyclic; continuous | 10% | 0.25 HZ | Stretch and relax during a 20 s period followed by a 10 s rest; this pattern is repeated three times, followed by a 5-min rest period. Thus, the cells were mechanically stimulated for a total of 60 s every 6 min 20 s | Dex inhibited protein synthesis, which was counteracted by stretching | Chromiak and Vandenburgh, 1992, 1994 |
| C2C12 myoblasts were fused to form 3D cultured myotubes in medium containing 2% horse serum | Culture in medium containing 2% horse serum | Uniaxial; static; continuous | 15% | NA | Continuously increasing load to achieve 15% stretch over 1 h; maintain static 15% stretch for further 2 h | Dex induced myotube atrophy with decreased diameter, which was counteracted by stretching | Aguilar-Agon et al., 2020 |