Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada.
Toronto Rehabilitation Institute, Toronto, Ontario, Canada.
J Appl Physiol (1985). 2021 Sep 1;131(3):871-880. doi: 10.1152/japplphysiol.00424.2021. Epub 2021 Jul 15.
Satellite cells (SC) play an integral role in the recovery from skeletal muscle damage and supporting muscle hypertrophy. Acute resistance exercise typically elevates type I and type II SC content 24-96 h post exercise in healthy young males, although comparable research in females is lacking. We aimed to elucidate whether sex-based differences exist in fiber type-specific SC content after resistance exercise in the untrained (UT) and trained (T) states. Ten young males (23.0 ± 4.0 yr) and females (23.0 ± 4.8 yr) completed an acute bout of resistance exercise before and after 8 wk of whole body resistance training. Muscle biopsies were taken from the vastus lateralis immediately before and 24 and 48 h after each bout to determine SC and myonuclear content by immunohistochemistry. Males had greater SC associated with type II fibers ( ≤ 0.03). There was no effect of acute resistance exercise on SC content in either fiber type ( ≥ 0.58) for either sex; however, training increased SC in type II fibers ( < 0.01) irrespective of sex. The change in mean 0-48 h type II SC was positively correlated with muscle fiber hypertrophy in type II fibers ( = 0.47; = 0.035). Furthermore, the change in myonuclei per fiber was positively correlated with type I and type II fiber hypertrophy (both = 0.68; < 0.01). Our results suggest that SC responses to acute and chronic resistance exercise are similar in males and females and that SC and myonuclear accretion is related to training-induced muscle fiber hypertrophy. We demonstrate that training-induced increase in SC content in type II fibers and myonuclear content in type I and II fibers is similar between males and females. Furthermore, these changes are related to the extent of muscle fiber hypertrophy. Thus, SC and myonuclear accretion appear to contribute to muscle hypertrophy irrespective of sex, highlighting the importance of these muscle stem cells in human skeletal muscle growth.
卫星细胞（SCs）在骨骼肌损伤恢复和支持肌肉肥大中起着至关重要的作用。急性抗阻运动通常会在健康年轻男性中，于运动后 24-96 小时内提高 I 型和 II 型 SC 的含量，尽管女性中缺乏类似的研究。我们旨在阐明在未经训练（UT）和训练（T）状态下，抗阻运动后，性别差异是否存在于纤维类型特异性 SC 含量中。10 名年轻男性（23.0±4.0 岁）和女性（23.0±4.8 岁）在全身抗阻训练 8 周前后完成了一次急性抗阻运动。在每次运动前后，从股外侧肌中采集肌肉活检，通过免疫组织化学法测定 SC 和肌核含量。男性的 II 型纤维与 SC 相关（≤0.03）。对于任何性别，急性抗阻运动都不会影响 SC 含量（≥0.58）；然而，无论性别如何，训练都增加了 II 型纤维中的 SC（<0.01）。0-48 小时 II 型 SC 的变化与 II 型纤维中的肌肉纤维肥大呈正相关（r=0.47；p=0.035）。此外，纤维内肌核的变化与 I 型和 II 型纤维肥大呈正相关（均 r=0.68；p<0.01）。我们的结果表明，男性和女性对急性和慢性抗阻运动的 SC 反应相似，SC 和肌核的积累与训练诱导的肌肉纤维肥大有关。我们证明，男性和女性中，II 型纤维中的 SC 含量和 I 型和 II 型纤维中的肌核含量的训练诱导增加是相似的。此外，这些变化与肌肉纤维肥大的程度有关。因此，SC 和肌核的积累似乎与性别无关，对肌肉肥大有贡献，突出了这些肌肉干细胞在人类骨骼肌生长中的重要性。
