Skeletal muscle adaptations at 8 and 12 weeks post-hemorrhagic stroke
LeAnn Snow, LaDora V. ThompsonAbstract
Objectives
Skeletal muscle structure and function contribute significantly to post-stroke hemiparesis, but stroke-related muscle adaptations are incompletely understood. Fiber atrophy and faster-to-slower fiber type shifts were previously described in rat tibialis anterior (TA) at 2 and 4 weeks after hemorrhagic stroke, whereas such changes were absent in soleus (SOL). The aim of this study was to extend to 8 and 12 weeks the evaluation of spontaneous muscle adaptations in SOL and TA after hemorrhagic stroke.
Methods
24 young Sprague Dawley rats were randomized into stroke (STR) and control (CTRL) groups for each of the 8 and 12 week post-stroke time periods. Motor deficit was verified by testing hindlimb function before stroke induction and prior to muscle harvest. Hemorrhagic stroke was induced in the right striatum of STR animals. After 8 or 12 weeks, bilateral SOL and TA muscles were harvested for evaluation of fiber cross-sectional areas and fiber types.
Results
SOL in STR groups showed no differences from control at 8 or 12 weeks post-stroke. Selective fiber type hypertrophy occurred in TA of the STR group, unilaterally by 8 weeks, and bilaterally by 12 weeks. Fiber type profile was slower in distinct locations of bilateral TA at both 8 and 12 weeks.
Conclusions
Skeletal muscle fiber type and size are plastic after stroke. Adaptations are muscle-specific and time- specific, and are likely related to neurologic and intrinsic muscle factors. These results suggest that muscle-related rehabilitative therapies require optimal time frames to influence this plasticity for improved function.