Hiroshima R1, Yamaji J2, Mori Y1
1Kansai University of Welfare Sciences, Department of Rehabilitation Sciences, Kashiwara-City, Osaka, Japan, 2Kansai University of Welfare Sciences, Department of Nutrition Sciences, Kashiwara-City, Osaka, Japan
Background: Disuse atrophy in skeletal muscle has been the issue in the rehabilitation fields since it frequently induces the secondary problems including muscle weakness, decreased ability of walking, loss of independence, and so on. However, the atrophied muscle can be returned to the normal state by increasing activity. Therefore, the physical therapy has played an essential role to treat patients with muscle atrophy. Our previous studies have revealed that the atrophied muscle becomes fragile and weak, therefore, easily injures itself just by bearing own weight. Then, this muscle injury triggers the inflammation which serves as a starting point for the recovery process.
Purpose: The study aimed to investigate the change of mRNA in the myosin heavy chain (MHC), which is the primary contractile protein in skeletal muscle, and the interleukin 6 (IL-6), which acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine, in the inflammatory stage of the recovery process from disuse atrophy in rat soleus muscle.
Methods: Male Wistar rats aged 11 weeks were randomly assigned into the healthy control (CON), 2-week hindlimb casting with anti-inflammatory injection (INJ), or 2-week hindlimb casting without injection (NO-INJ) groups. In INJ group, Depo-Medrol was injected as an anti-inflammatory steroid in the soleus muscle immediately after releasing from cast. Soleus muscles were extracted on 3 and 7 days after releasing from 2-week casting and measured its wet muscle mass (WMM). For mRNA analysis, real-time PCR was performed using specific primers for MHC-I as slow type, MHC-IIa as fast type, IL-6 and GAPDH.
Results: The WMM was decreased by 2-week casting compared to CON. NO-INJ group decreased WMM further on 3-day after releasing from cast, but slightly increased on 7-day. In INJ group, the WMM was increased more than the CON level on 3-day, but decreased to the 2-week casting level on 7-day. The mRNA IL-6 was significantly increased by 2-week casting, then decreased on 3-day, but slightly increased on 7-day in both INJ and NO-INJ groups. However, the amount of mRNA was significantly lower in INJ than NO-INJ group. The mRNA MHC-I was decreased by 2-week casting, then further decreased on 3-day, and much further decreased on 7-days in both groups. The mRNA MHC-IIa was increased by 2-week casting, then further increased on 3-day, but decreased on 7-days in both groups. However, the amounts in both MHC-I and MHC-IIa were lower in NO-INJ compared to INJ group.
Conclusion(s): The results of the study demonstrated the muscle atrophy and a tendency of transition toward the fast type, which was consistent to the other studies. The anti-inflammatory steroid supposed to alleviate the decrease of slow type MHC and to amplify the increase of fast type MHC. The study suggested the anti-inflammatory injection could promote early recovery process on 3-day but not much difference on 7-day.
Implications: This study can provide the relevant information when physical therapists evaluate the patients with muscle atrophy and choose the appropriate treatment options.
Keywords: Recovery from muscle atrophy, myosin heavy chain (MHC), interleukin 6 (IL-6)
Funding acknowledgements: The study was funded by “Grants-in Aid for Scientific Research” of Japan Society for the Promotion of Science.
Purpose: The study aimed to investigate the change of mRNA in the myosin heavy chain (MHC), which is the primary contractile protein in skeletal muscle, and the interleukin 6 (IL-6), which acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine, in the inflammatory stage of the recovery process from disuse atrophy in rat soleus muscle.
Methods: Male Wistar rats aged 11 weeks were randomly assigned into the healthy control (CON), 2-week hindlimb casting with anti-inflammatory injection (INJ), or 2-week hindlimb casting without injection (NO-INJ) groups. In INJ group, Depo-Medrol was injected as an anti-inflammatory steroid in the soleus muscle immediately after releasing from cast. Soleus muscles were extracted on 3 and 7 days after releasing from 2-week casting and measured its wet muscle mass (WMM). For mRNA analysis, real-time PCR was performed using specific primers for MHC-I as slow type, MHC-IIa as fast type, IL-6 and GAPDH.
Results: The WMM was decreased by 2-week casting compared to CON. NO-INJ group decreased WMM further on 3-day after releasing from cast, but slightly increased on 7-day. In INJ group, the WMM was increased more than the CON level on 3-day, but decreased to the 2-week casting level on 7-day. The mRNA IL-6 was significantly increased by 2-week casting, then decreased on 3-day, but slightly increased on 7-day in both INJ and NO-INJ groups. However, the amount of mRNA was significantly lower in INJ than NO-INJ group. The mRNA MHC-I was decreased by 2-week casting, then further decreased on 3-day, and much further decreased on 7-days in both groups. The mRNA MHC-IIa was increased by 2-week casting, then further increased on 3-day, but decreased on 7-days in both groups. However, the amounts in both MHC-I and MHC-IIa were lower in NO-INJ compared to INJ group.
Conclusion(s): The results of the study demonstrated the muscle atrophy and a tendency of transition toward the fast type, which was consistent to the other studies. The anti-inflammatory steroid supposed to alleviate the decrease of slow type MHC and to amplify the increase of fast type MHC. The study suggested the anti-inflammatory injection could promote early recovery process on 3-day but not much difference on 7-day.
Implications: This study can provide the relevant information when physical therapists evaluate the patients with muscle atrophy and choose the appropriate treatment options.
Keywords: Recovery from muscle atrophy, myosin heavy chain (MHC), interleukin 6 (IL-6)
Funding acknowledgements: The study was funded by “Grants-in Aid for Scientific Research” of Japan Society for the Promotion of Science.
Topic: Musculoskeletal; Health promotion & wellbeing/healthy ageing; Research methodology & knowledge translation
Ethics approval required: Yes
Institution: Kansai University of Welfare Sciences
Ethics committee: the committee of the management in animal experiments
Ethics number: 44576
All authors, affiliations and abstracts have been published as submitted.
