A data-driven analysis of fiber type architecture over the entire muscle
Abstract Background Skeletal muscle function is inferred from the spatial arrangement of muscle fibers architecture, which corresponds to myofiber molecular and metabolic features. Myofiber types can be distinguished by the expression of myosin heavy chain (MyHC) isoforms, representing contraction properties. In most studies, myofiber typing is determined from a local sampling, typically obtained from the muscle median region. This median region is assumed to represent the entire muscle. However, it remains largely unknown to what extent this local sampling represents the entire muscle. Methods We present here a pipeline to study the architecture of muscle fiber type over the entire muscle, from sectioning, staining, imaging to image quantification and data-driven analysis. Results We reconstructed muscle architecture from consecutive cross-sections stained for laminin and MyHC isoforms. Examining the entire muscle using consecutive cross-sections is extremely laborious, we provide consideration to reduce dataset and yet to cover the entire muscle. Analyses of over 15,000 myofibers, showed spatial variations in myofiber geometric features, myofiber type and the distribution of neuromuscular junctions along the entire muscle. Conclusions We suggest that asymmetric spatial distribution of myofiber types, geometric features of myofibers and the neuromuscular junctions along the muscle could affect muscle function. Therefore, instead of a single sampling from a median region, representative regions covering the entire muscle should be investigated in future studies.