National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
Nat Commun. 2020 Jul 24;11(1):3722. doi: 10.1038/s41467-020-17579-6.
Human movement occurs through contraction of the basic unit of the muscle cell, the sarcomere. Sarcomeres have long been considered to be arranged end-to-end in series along the length of the muscle into tube-like myofibrils with many individual, parallel myofibrils comprising the bulk of the muscle cell volume. Here, we demonstrate that striated muscle cells form a continuous myofibrillar matrix linked together by frequently branching sarcomeres. We find that all muscle cells contain highly connected myofibrillar networks though the frequency of sarcomere branching goes down from early to late postnatal development and is higher in slow-twitch than fast-twitch mature muscles. Moreover, we show that the myofibrillar matrix is united across the entire width of the muscle cell both at birth and in mature muscle. We propose that striated muscle force is generated by a singular, mesh-like myofibrillar network rather than many individual, parallel myofibrils.
人类运动是通过肌肉细胞的基本单位——肌节的收缩来实现的。肌节长期以来一直被认为是沿着肌肉的长度一个接一个地排列成管状的肌原纤维，许多单独的、平行的肌原纤维构成了肌肉细胞体积的大部分。在这里，我们证明了横纹肌细胞形成了一个连续的肌原纤维基质，通过频繁分支的肌节连接在一起。我们发现，所有的肌肉细胞都含有高度连接的肌原纤维网络，尽管肌节分支的频率从出生后早期到晚期逐渐降低，并且在慢肌纤维比快肌纤维成熟的肌肉中更高。此外，我们还表明，肌原纤维基质在整个肌肉细胞的宽度上都是相连的，无论是在出生时还是在成熟的肌肉中。我们提出，横纹肌的力量是由一个单一的、网状的肌原纤维网络而不是许多单独的、平行的肌原纤维产生的。
