Abstract
Eccentric exercise leads to focal disruptions in the myofibrils, referred to as “lesions”. These structures are thought to contribute to the post-exercise muscle weakness, and to represent areas of mechanical damage and/or remodelling. Lesions have been investigated in human biopsies and animal samples after exercise. However, this approach does not examine the mechanisms behind lesion formation, or their behaviour during contraction. To circumvent this, we used electrical pulse stimulation (EPS) to simulate exercise in C2C12 myotubes, combined with live microscopy. EPS application led to the formation of sarcomeric lesions in the myotubes, resembling those seen in exercised mice, increasing in number with the time of application or stimulation intensity. Furthermore, transfection with an EGFP-tagged version of the lesion and Z-disc marker filamin-C allowed us to observe the formation of lesions using live cell imaging. Finally, using the same technique we studied the behaviour of these structures during contraction, and observed them to be passively stretching. This passive behaviour supports the hypothesis that lesions contribute to the post-exercise muscle weakness, protecting against further damage. We conclude that EPS can be reliably used as a model for the induction and study of sarcomeric lesions in myotubes in vitro.
Highlights
Skeletal muscle is plastic and adaptable, increasing in size with demanding exercise and decreasing with immobilisation, or during aging and disease[1,2,3]
In this work we present the application of the Electrical pulse stimulation (EPS) technology to study the formation and function of sarcomeric lesions in skeletal muscle cells
We show that EPS can induce those structures in cultured myotubes, proportionally to the amount of time of EPS application and protocol intensity
Summary
Skeletal muscle is plastic and adaptable, increasing in size with demanding exercise and decreasing with immobilisation, or during aging and disease[1,2,3]. EPS has been used to simulate exercise in cultured myotubes, and to study its effects on mouse[39,40,41,42,43,44,45,46] and human cells[47] using markers such as increased glucose metabolism[40,41,47], Akt phosphorylation[41], upregulation of exercise-related chemokines[42,43,44,45] and induction of Hsp[70] expression[46]. We conclude that EPS is a powerful tool for the induction of sarcomeric damage in cultured myotubes, and its analysis in living cells
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