Myogenesis contributes to functional electrical stimulation (fes)‐induced recovery of myofiber excitability and mass of human long‐term denervated muscles in spinal cord injury (SCI)

Many months after SCI, when an irreversible injury involves lower motoneurons, severe atrophy of human muscle is complicated by fibrosis and fat substitution (denervated, degenerated muscle, DDM). We will describe the effects of long-term lower motoneuron denervation on human muscle and present the structural results of muscle trained using FES. Antibody for embryonic myosin demonstrates that sustained myogenesis occurs in human DDM. By electron microscopy we studied: a) the overall structure of fibers and myofibrils in long-term DDM, including the effects of FES, and b) the structure and localization of calcium release units, or triads, the structure deputed to activate muscle contraction during excitation-contraction coupling (ECC). The poor excitability of human long-term DDM fibers during the first stages of FES training could be explained in terms of spatial disorder of both the ECC and contractile apparati. The structural studies are extremely encouraging since they demonstrate that FES training is effective in reverting long-term DDM atrophy and in maintaining the trophic state of the recovered myofibers.