Purpose

To experimentally measure selected passive properties of skeletal muscle at three different scales (macroscopic scale: whole muscle, microscopic scale: single skinned fiber, and submicron scale: single myofibril) within the same animal model (mice), and to compare a primarily slow-twitch fiber muscle (soleus) and a primarily fast-twitch fiber muscle (extensor digitorum longus, EDL) for each scale.

Methods

Healthy 3 months old wild-type C57BL6 mice were used. To characterize each scale, soleus (N = 11), EDL (N = 9), slow fibers (N = 17), fast fibers (N = 16), and myofibrils from soleus (N = 11) and EDL (N = 11) were harvested. Passive mechanical (ramp, relaxation) tests were applied at each scale to compare the passive properties (Young's modulus, static and dynamic stresses) within a given scale, across scales and between muscle types.

Results

The soleus and EDL showed significant passive mechanical differences at the macroscopic scale while no variation was observed between both tissues at the microscopic and submicron scales. The results highlight the importance of the scale that is used to mechanically characterize a multiscale tissue.

Conclusion

The present work will allow for a better understanding of the multiscale passive mechanical properties for two muscles with vastly differing physiological and metabolic properties. This study provides referent data to the body of literature that can be built upon in future work.

中文翻译：

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啮齿动物骨骼肌的多尺度被动机械表征

目的

为了在同一动物模型（小鼠）内以三种不同尺度（宏观尺度：整个肌肉、微观尺度：单皮纤维和亚微米尺度：单肌原纤维）实验测量骨骼肌的选定被动特性，并比较主要慢速每个尺度都有肌纤维肌（比目鱼肌）和主要的快肌纤维肌（趾长伸肌，EDL）。

方法

使用健康的 3 个月大的野生型 C57BL6 小鼠。为了表征每个尺度，比目鱼肌 (N = 11)、EDL (N = 9)、慢纤维 (N = 17)、快纤维 (N = 16) 以及比目鱼肌 (N = 11) 和 EDL (N = 11) 的肌原纤维）被收获。在每个尺度上应用被动机械（斜坡、松弛）测试，以比较给定尺度内、跨尺度和肌肉类型之间的被动特性（杨氏模量、静态和动态应力）。

结果

比目鱼肌和 EDL 在宏观尺度上表现出显着的被动机械差异，而在微观和亚微米尺度上两种组织之间没有观察到变化。结果强调了用于机械表征多尺度组织的尺度的重要性。

结论

目前的工作将有助于更好地理解具有截然不同的生理和代谢特性的两块肌肉的多尺度被动机械特性。这项研究为未来工作中可以借鉴的文献提供了参考数据。