Key result
Long-term in vitro optogenetic exercise of myotubes accelerated contraction velocity and induced a shift towards a fast fiber phenotype via upregulation of neo-Myh8 and fast myosin heavy chain isoforms.
Why the study?
Skeletal muscle fiber type composition influences physiological characteristics and susceptibility to disease and ageing, requiring in vitro systems to account for fiber specification when modelling muscle conditions.
Long-term optogenetic stimulation induces a shift towards a fast fiber phenotype in cultured myotubes, providing a novel in vitro exercise strategy to study fiber specification and refine muscle disease modeling.
Enables fiber-type specific in vitro muscle modeling; leaves open translation to disease or ageing studies.
The composition of fiber types within skeletal muscle impacts the tissue’s physiological characteristics and susceptibility to disease and ageing. In vitro systems should therefore account for fiber type composition when modelling muscle conditions. To induce fiber specification in vitro , we designed a quantitative contractility assay based on optogenetics and particle image velocimetry. We submitted cultured myotubes to long-term intermittent light stimulation patterns and characterized their structural and functional adaptations. After several days of in vitro exercise, myotubes contract faster and are more resistant to fatigue. The enhanced contractile functionality was accompanied by advanced maturation such as increased width and upregulation of neuron receptor genes. We observed an upregulation in the expression of distinct myosin heavy chain isoforms (namely, neonatal-Myh8 and fast-Myh), which induced a shift towards a fast fiber phenotype. This long-term in vitro exercise strategy can be used to study fiber specification and refine muscle disease modelling.
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Hennig et al. (2022) studied In vitro muscle modeling. OptoTraining (long-term intermittent light stimulation) vs. Untrained control myotubes was evaluated on Contraction velocity and myosin heavy chain isoform expression. Long-term in vitro optogenetic exercise of myotubes accelerated contraction velocity and induced a shift towards a fast fiber phenotype via upregulation of neo-Myh8 and fast myosin heavy chain isoforms.
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