Post-injury stretch promotes recovery in a rat model of muscle damage induced by lengthening contractions
We investigated the cellular mechanisms and therapeutic effect of post-injury stretch on the recovery process from muscle injury induced by lengthening contractions (LC). One day after LC, a single 15-min bout of muscle stretch was applied at an intensity of 3 mNm. The maximal isometric torque was measured before and at 2–21 days after LC. The myofiber size was analyzed at 21 days after LC. Developmental myosin heavy chain-immunoreactive (dMHC-ir) cells, a marker of regenerating myofibers, were observed in the early recovery stage (2–5 days after LC). We observed that LC-induced injury markedly decreased isometric torque and myofiber size, which recovered faster in rats that underwent stretch than in rats that did not. Regenerating myofiber with dMHC-ir cells was observed earlier in rats that underwent stretch. These results indicate that post-injury stretch may facilitate the regeneration and early formation of new myofibers, thereby promoting structural and functional recovery from LC-induced muscle injury.
KeywordsLengthening contractions Muscle injury Stretch Mechanical stimulation Regeneration Developmental myosin heavy chain
This work was supported in part by Grants-in-Aid for Scientific Research (B) (JSPS KAKENHI Grant numbers JP15H03042 to KK, and JP25282160 and JP16H03202 to TT) and for Challenging Exploratory Research (JP25560254 and JP16K12938 to KK), as well as by the Japan Agency for Medical Research and Development (AMED) Grant 16gm0810010h0502 (to TT) and by funding from the Hori Sciences and Arts Foundation (to TT).
TM, NA, YI, and MI-M performed the histological analyses and muscle function tests; TM, TT, and KK conceived the study and drafted the manuscript; KM and MS revised the manuscript critically.
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Conflict of interest
The authors declare that they have no conflict of interest.