Olsson Karl, Cheng Arthur J, Alam Seher, Al-Ameri Mamdoh, Rullman Eric, Westerblad Håkan, Lanner Johanna T, Bruton Joseph D, Gustafsson Thomas
Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, 141 86 Sweden ; Department of Physiology and Pharmacology, Karolinska Institutet, von Eulers väg 8, Stockholm, 171 77 Sweden.
Department of Physiology and Pharmacology, Karolinska Institutet, von Eulers väg 8, Stockholm, 171 77 Sweden.
Skelet Muscle. 2015 Aug 20;5:26. doi: 10.1186/s13395-015-0050-x. eCollection 2015.
In skeletal muscle, intracellular Ca(2+) is an important regulator of contraction as well as gene expression and metabolic processes. Because of the difficulties to obtain intact human muscle fibers, human myotubes have been extensively employed for studies of Ca(2+)-dependent processes in human adult muscle. Despite this, it is unknown whether the Ca(2+)-handling properties of myotubes adequately represent those of adult muscle fibers.
To enable a comparison of the Ca(2+)-handling properties of human muscle fibers and myotubes, we developed a model of dissected intact single muscle fibers obtained from human intercostal muscle biopsies. The intracellular Ca(2+)-handling of human muscle fibers was compared with that of myotubes generated by the differentiation of primary human myoblasts obtained from vastus lateralis muscle biopsies.
The intact single muscle fibers all demonstrated strictly regulated cytosolic free [Ca(2+)] ([Ca(2+)]i) transients and force production upon electrical stimulation. In contrast, despite a more mature Ca(2+)-handling in myotubes than in myoblasts, myotubes lacked fundamental aspects of adult Ca(2+)-handling and did not contract. These functional differences were explained by discrepancies in the quantity and localization of Ca(2+)-handling proteins, as well as ultrastructural differences between muscle fibers and myotubes.
Intact single muscle fibers that display strictly regulated [Ca(2+)]i transients and force production upon electrical stimulation can be obtained from human intercostal muscle biopsies. In contrast, human myotubes lack important aspects of adult Ca(2+)-handling and are thus an inappropriate model for human adult muscle when studying Ca(2+)-dependent processes, such as gene expression and metabolic processes.
在骨骼肌中，细胞内钙离子（Ca(2+)）是收缩以及基因表达和代谢过程的重要调节因子。由于获取完整的人类肌纤维存在困难，人类肌管已被广泛用于研究成人肌肉中依赖钙离子的过程。尽管如此，尚不清楚肌管的钙离子处理特性是否能充分代表成人肌纤维的特性。
为了比较人类肌纤维和肌管的钙离子处理特性，我们建立了一个从人类肋间肌活检中获取的完整单根肌纤维的解剖模型。将人类肌纤维的细胞内钙离子处理与从股外侧肌活检中获得的原代人类成肌细胞分化产生的肌管的钙离子处理进行比较。
完整的单根肌纤维在电刺激时均表现出严格调控的胞质游离钙离子浓度（[Ca(2+)]i）瞬变和力的产生。相比之下，尽管肌管中的钙离子处理比成肌细胞更成熟，但肌管缺乏成人钙离子处理的基本特征，并且不会收缩。这些功能差异可通过钙离子处理蛋白的数量和定位差异以及肌纤维和肌管之间的超微结构差异来解释。
从人类肋间肌活检中可以获得在电刺激时表现出严格调控的[Ca(2+)]i瞬变和力产生的完整单根肌纤维。相比之下，人类肌管缺乏成人钙离子处理的重要特征，因此在研究依赖钙离子的过程（如基因表达和代谢过程）时，不是人类成人肌肉的合适模型。
