Petrella John K, Kim Jeong-Su, Mayhew David L, Cross James M, Bamman Marcas M
Department of Physiology and Biophysics, The University of Alabama, Birmingham, Alabama 35294-0005, USA.
J Appl Physiol (1985). 2008 Jun;104(6):1736-42. doi: 10.1152/japplphysiol.01215.2007. Epub 2008 Apr 24.
A present debate in muscle biology is whether myonuclear addition is required during skeletal muscle hypertrophy. We utilized K-means cluster analysis to classify 66 humans after 16 wk of knee extensor resistance training as extreme (Xtr, n = 17), modest (Mod, n = 32), or nonresponders (Non, n = 17) based on myofiber hypertrophy, which averaged 58, 28, and 0%, respectively (Bamman MM, Petrella JK, Kim JS, Mayhew DL, Cross JM. J Appl Physiol 102: 2232-2239, 2007). We hypothesized that robust hypertrophy seen in Xtr was driven by superior satellite cell (SC) activation and myonuclear addition. Vastus lateralis biopsies were obtained at baseline and week 16. SCs were identified immunohistochemically by surface expression of neural cell adhesion molecule. At baseline, myofiber size did not differ among clusters; however, the SC population was greater in Xtr (P < 0.01) than both Mod and Non, suggesting superior basal myogenic potential. SC number increased robustly during training in Xtr only (117%; P < 0.001). Myonuclear addition occurred in Mod (9%; P < 0.05) and was most effectively accomplished in Xtr (26%; P < 0.001). After training, Xtr had more myonuclei per fiber than Non (23%; P < 0.05) and tended to have more than Mod (19%; P = 0.056). Both Xtr and Mod expanded the myonuclear domain to meet (Mod) or exceed (Xtr) 2,000 mum(2) per nucleus, possibly driving demand for myonuclear addition to support myofiber expansion. These findings strongly suggest myonuclear addition via SC recruitment may be required to achieve substantial myofiber hypertrophy in humans. Individuals with a greater basal presence of SCs demonstrated, with training, a remarkable ability to expand the SC pool, incorporate new nuclei, and achieve robust growth.
肌肉生物学领域当前的一个争论点是，骨骼肌肥大过程中是否需要增加肌核。我们利用K均值聚类分析，根据肌纤维肥大情况，将66名接受16周伸膝抗阻训练的人分为极端反应者（Xtr，n = 17）、适度反应者（Mod，n = 32）或无反应者（Non，n = 17），其肌纤维肥大平均分别为58%、28%和0%（Bamman MM，Petrella JK，Kim JS，Mayhew DL，Cross JM。《应用生理学杂志》102：2232 - 2239，2007）。我们假设，极端反应者中出现的显著肥大是由更优的卫星细胞（SC）激活和肌核增加所驱动。在基线期和第16周时获取股外侧肌活检样本。通过神经细胞黏附分子的表面表达，免疫组织化学鉴定卫星细胞。在基线期，各聚类之间的肌纤维大小无差异；然而，极端反应者的卫星细胞群体数量比适度反应者和无反应者都多（P < 0.01），表明其基础生肌潜力更优。仅在极端反应者中，卫星细胞数量在训练期间显著增加（117%；P < 0.001）。适度反应者出现了肌核增加（9%；P < 0.05），而在极端反应者中最为显著（26%；P < 0.001）。训练后极端反应者每根纤维的肌核比无反应者更多（23%；P < 0.05），且倾向于比适度反应者更多（19%；P = 0.056）。极端反应者和适度反应者都扩大了肌核域，以达到（适度反应者）或超过（极端反应者）每个核2000μm²，这可能促使对增加肌核以支持肌纤维扩张的需求。这些发现有力地表明，在人类中，通过募集卫星细胞增加肌核可能是实现显著肌纤维肥大所必需的。具有更多基础卫星细胞的个体在训练后表现出显著的能力，能够扩大卫星细胞池、纳入新的细胞核并实现强劲生长。
