Distinct patterns of fiber type adaptation in rat hindlimb muscles 4 weeks after hemorrhagic stroke

Objective The aim of this study was to evaluate adaptations in soleus (SOL) and tibialis anterior (TA) muscles in a rat model 4 weeks after hemorrhagic stroke. Design Young adult Sprague-Dawley rats were randomly assigned to two groups: stroke (STR) and control (CTRL), with 8 SOL and 8 TA muscles per group. Hemorrhagic stroke was induced in the right caudoputamen of the STR rats. CTRL rats had no intervention. Neurologic status was evaluated in both groups pre-stroke, and four weeks post-stroke. Muscles were harvested after post-stroke neurologic testing. Muscle fiber types and cross-sectional areas were determined in SOL and TA using immunohistochemical labeling for myosin heavy chain (MHC). Results No generalized fiber atrophy was found in any of the muscles. Fiber types shifted from faster to slower in the TA of the STR group, but no fiber type shifts occurred in the SOL muscles of STR animals. Conclusion Since slower MHC fiber types are associated with weaker contractile force and slower contractile speed, this faster-to-slower fiber type shift in TA muscles may contribute to weaker and slower muscle contraction in this muscle after stroke. This finding may indicate potential therapeutic benefit from treatments known to influence fiber type plasticity. Corresponding author: L. Snow, MMC 388, 420 Delaware St. SE, Minneapolis, MN 55455, Phone: 612-626-5782, FAX: 612-625-4274, Email: snow0018@umn.edu Disclosures: Funding: NIH-K08HD049459 Competing interests and financial benefits to authors: none The results of this study have not been previously presented at any professional association meeting. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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