Why the study?
It was unknown whether muscle fibers in myostatin knockout mice are merely larger or also exhibit morphological, metabolic, and functional differences from wild-type mice.
Does myostatin knockout alter the morphological, metabolic, and functional properties of muscle fibers in mice?
Does myostatin knockout alter the morphological, metabolic, and functional properties of muscle fibers in mice?
Myostatin knockout mice have larger muscle fibers with greater force-generating capacity due to increased cross-sectional area, but normal muscle quality and function.
Higher absolute force in larger MSTN-/- fibers without altered specific tension; leaves open translation to human myostatin-targeted therapies.
INTRODUCTION: We assessed whether muscle fibers in myostatin knockout (MSTN-/-) mice are just larger or also exhibit morphological, metabolic, and functional differences from MSTN+/+ mice. METHODS: We compared single fiber contractile properties and histological fiber properties in muscles from MSTN-/- and MSTN+/+ mice. RESULTS: Even though in permeabilized muscle fibers from the extensor digitorum longus and soleus muscle maximal force was higher (p < 0.001) there were no significant differences in specific power (power per unit volume), specific tension (force per cross-sectional area), maximal shortening velocity, or curvature of the force-velocity relationship between MSTN-/- and MSTN+/+ mice. In histological sections of the soleus muscle, fibers were larger (p < 0.001), but the succinate dehydrogenase staining intensity and capillary density did not differ significantly between MSTN-/- and MSTN+/+ mice, which was explicable by the larger number of capillaries around a fiber (p < 0.001). A model showed no significant differences in soleus muscle oxygenation. DISCUSSION: The larger force-generating capacity of fibers from MSTN-/- mice is explicable by the larger fiber cross-sectional area. The data indicate that muscle fibers from MSTN-/- mice are quantitatively, but not qualitatively different from muscle fibers from MSTN+/+ mice. Myostatin inhibition may help increase muscle mass in conditions accompanied by muscle weakness without a detrimental impact on muscle quality, but systemic side effects need to be considered.
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Degens et al. (2025) studied this question.
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