Localized and limited changes in the expression of myosin heavy chains in injured skeletal muscle fibers being repaired.

The process of skeletal muscle repair was investigated by immunocytochemical evaluation of chicken leg muscles injured by a localized crush or superficial cut. Only the damaged parts of the muscle fibers, approximately 400-500 microm across, along the longitudinal axis, expressed ventricular myosin heavy chain. The level of this myosin heavy chain along the fiber length further decreased with time. Unlike the newly generated independent regenerating myotubes, even the injured parts of original mature muscle fibers positive for ventricular myosin heavy chain in the immediate vicinity of injury did not show changes in the expression of slow or fast myosin heavy chains in these regions. It is concluded that muscle fibers injured by superficial cut or crush methods used in this study despite being multinucleated were rapidly repaired by localized changes without affecting the major gene expression in the uninjured parts of the fibers.