Single-Cell Imaging of Mitochondrial Metabolism and Remodeling in C2C12 Murine Skeletal Muscle Cells upon Differentiation.

As primary sites for oxygen consumption and energy production via oxidative phosphorylation (OXPHOS), mitochondria play a central role in the regulation of bioenergetics and generation of key metabolic intermediates for myogenic cell growth. Common methods to study mitochondria and their metabolism typically rely on population-level analyses, which can mask potential differences in individual cells. In this study, we used various imaging approaches to investigate the interplay between intracellular oxygenation, mitochondrial metabolism and dynamics in a model of myogenic differentiation. Fluorescence imaging of intracellular oxygen revealed that myogenic differentiation is accompanied by progressive shifts in intracellular oxygenation that depend upon and reflect changes in mitochondrial metabolism (i.e., higher oxygen consumption and adenosine triphosphate (ATP) production). By measuring intracellular oxygenation, we showed that mitochondrial metabolism reduces oxygen availability in the cytosol and the nucleus. Real-time redox imaging at the single-cell level further highlighted substantial metabolic heterogeneity and a shift toward OXPHOS as differentiation progressed. Morphological analyses revealed that during myogenic differentiation, mitochondria increase in size while becoming less mobile and overlapping less with microtubules. Overall, this study illustrates the value of combining complementary imaging approaches to provide a comprehensive single-cell perspective on mitochondrial metabolism, remodeling and spatial organization during myogenesis.