Nanostructural organization of skeletal muscle myocytes revealed by scanning probe nanotomography

Objective: to perform a statistical analysis of the angular orientations of hexagonal myofilament lattices in rat skeletal muscle myofibrils using scanning probe nanotomography (SPN). Materials and methods. Skeletal muscle tissue samples were obtained from healthy Wistar rats for the study. Specimens of rat lumbar skeletal muscle fibers were embedded in epoxy resin. After sectioning with an ultramicrotome, the specimen surfaces were examined using SPN. Analysis of the resulting images of sarcomere cross-sections enabled the determination of the angular orientations of the hexagonal lattices formed by myosin myofilaments. Results. A method was developed to calculate the angular orientations of hexagonal lattices based on moiré patterns observed in images of sarcomere cross-sections. Statistical analysis of the obtained images showed that the relative rotations of the hexagonal lattices do not follow a normal distribution according to the Kolmogorov–Smirnov test (p = 0.3). The results indicate that the orientations of the lattices vary randomly along the myofibrils. Conclusion. Analysis of lattice orientations in adjacent sarcomeres made it possible, for the first time, to obtain and statistically evaluate data on their mutual orientations along myofibrils. The results revealed a low degree of alignment in the orientations of myosin filaments within myofibrils of rat skeletal muscle. The proposed methods and algorithms may be further applied to studies of the nanostructural organization of myocytes and cardiomyocytes in different species.

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