Structural differentiation of skeletal muscle fibers in the absence of innervation in humans

This study investigates how muscle structure recovers in patients with spinal cord injuries who underwent functional electrical stimulation (FES) for several years. These patients experienced muscle denervation, which usually leads to muscle atrophy and disorganization. The research found that FES could remarkably restore muscle structure, mass, and force, even after long periods of denervation. This recovery occurred without nerve signals, suggesting muscle activity alone can drive structural improvements. The muscle recovery process induced by FES mimics normal muscle development, indicating that electrical stimulation can initiate similar biological mechanisms in denervated muscles.

• 1
  FES treatment significantly increased muscle fiber diameter in denervated muscles compared to untreated muscles. The fiber size increase was accompanied by a reduction in connective and adipose tissues.
• 2
  Electron microscopy revealed a striking restoration of the fiber’s internal architecture in FES-treated muscles. Myofibrils were well-aligned, and sarcomeres exhibited ordered arrangements of filaments.
• 3
  The restoration of muscle structure occurs in a pattern that mimics normal muscle development, with myofibrillogenesis starting at the fiber's periphery and proceeding centrally.