The aim of this study was to evaluate and compare the efficacy of different remobilization protocols in different skeletal muscles considering the changes induced by hindlimb suspension of the tail. Thirty-six female Wistar rats were divided into six groups: control I, control II, suspended, suspended free, suspended trained on a declined treadmill and suspended trained on a flat treadmill. Fragments of soleus and tibialis anterior (TA) muscle were frozen and processed by different histochemical methods. The suspended soleus showed a significant increase in the proportional number of intermediate/hybrid fibers and a decrease in the number of type I fibers. Some of these changes proved to be reversible after remobilization. The three remobilization programs led to the recovery of both the proportional number of fibers and their size. The TA muscle presented a significant increase in the number and size of type I fibers and a cell size reduction of type IIB fibers, which were recovered after training on a declined treadmill and free movement. Especially regarding the soleus, the present findings indicate that, among the protocols, training on a declined treadmill was found to induce changes of a more regenerative nature, seemingly indicating a better tissue restructuring after the suspension procedure.
Extracellular matrix and costamere proteins transmit the concentric, isometric, and
eccentric forces produced by active muscle contraction. The expression of these
proteins after application of passive tension stimuli to muscle remains unknown. This
study investigated the expression of laminin and dystrophin in the soleus muscle of
rats immobilized with the right ankle in plantar flexion for 10 days and subsequent
remobilization, either by isolated free movement in a cage or associated with passive
stretching for up to 10 days. The intensity of the macrophage response was also
evaluated. One hundred and twenty-eight female Wistar rats were divided into 8
groups: free for 10 days; immobilized for 10 days; immobilized/free for 1, 3, or 10
days; or immobilized/stretched/free for 1, 3, or 10 days. After the experimental
procedures, muscle tissue was processed for immunofluorescence
(dystrophin/laminin/CD68) and Western blot analysis (dystrophin/laminin).
Immobilization increased the expression of dystrophin and laminin but did not alter
the number of macrophages in the muscle. In the stretched muscle groups, there was an
increase in dystrophin and the number of macrophages after 3 days compared with the
other groups; dystrophin showed a discontinuous labeling pattern, and laminin was
found in the intracellular space. The amount of laminin was increased in the muscles
treated by immobilization followed by free movement for 10 days. In the initial
stages of postimmobilization (1 and 3 days), an exacerbated macrophage response and
an increase of dystrophin suggested that the therapeutic stretching technique induced
additional stress in the muscle fibers and costameres.
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