Evidence for the contribution of muscle stem cells to nonhypertrophic skeletal muscle remodeling in humans.
The purpose of this study was to explore the possible role of muscle stem cells, also referred to as satellite cells (SCs), in adaptation and remodeling following a nonhypertrophic stimulus in humans. Muscle biopsies were obtained from the vastus lateralis of previously untrained women (n=15; age: 27±8 yr, BMI: 29±6 kg/m(2)) before and after 6 wk of aerobic interval training. The fiber type-specific SC response to training was analyzed using immunofluorescent microscopy of muscle cross sections. Following training, the number of SCs associated with fibers expressing myosin heavy-chain type I and II isoforms (hybrid fibers) increased (pre: 0.062±0.035 SC/hybrid fiber; post: 0.38±0.063 SC/hybrid fiber; P<0.01). In addition, there was a greater number of MyoD(+)/Pax7(-) SCs, indicative of differentiating SCs, associated with hybrid fibers (0.18±0.096 MyoD(+)/Pax7(-) SC/hybrid fiber) compared to type I (0.015±0.00615 MyoD(+)/Pax7(-) SC/type I fiber) or II (0.012±0.00454 MyoD(+)/Pax7(-) SC/type II fiber) fibers (P<0.05). There was also a training-induced increase in the number of hybrid fibers containing centrally located nuclei (15.1%) compared to either type I (3.4%) or II fibers (3.6%) (P<0.01). These data are consistent with the hypothesis that SCs contribute to the remodeling of muscle fibers even in the absence of hypertrophy.
1Departments of Kinesiology and Medical Physics and Applied Radiation Sciences, McMaster University, Hamilton, Ontario, Canada L8S 4L8. pariseg@mcmaster.ca.
Sophie
S
Joanisse
Jenna B
JB
Gillen
Leeann M
LM
Bellamy
Bryon R
BR
McKay
Mark A
MA
Tarnopolsky
Martin J
MJ
Gibala
Gianni
G
Parise
D000222:Adaptation, Physiological; D000328:Adult; D015444:Exercise; D005260:Female; D006801:Humans; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000378:metabolism; D051763:PAX7 Transcription Factor / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*
D017570:MyoD Protein; C057363:MyoD1 myogenic differentiation protein; D051763:PAX7 Transcription Factor; C497321:PAX7 protein, human; D020033:Protein Isoforms; D018995:Myosin Heavy Chains
Pax7; aerobic interval training; satellite cells