Investigation of mouse gastrocnemius-soleus muscle complex satellite and non-satellite stem cell responses to acute and chronic swimming exercise

Exercise protocols are widely used in the prevention and treatment of muscle diseases. However, the mechanisms of muscle damage and regeneration in response to different exercise protocols, the roles of muscle satellite and non-satellite cells in these processes, and the possible interactions of these stem cells with each other over time have not yet been clearly revealed. In this PhD thesis, it was aimed to examine satellite and non-satellite cell responses in muscle damage and regeneration processes in the early (3 hours) and late (48 hours) periods following acute and long-term swimming exercise in mice. 8-12 week old adult Balb/C male mice were first grouped as control and swimming exercise. After the exercise groups were divided into two as acute and chronic exercise, each was divided into two again (n = 10) in terms of the time passed from exercise to termination of the experiment (3 hours, 48 hours). Acute swimming exercise was applied for 30 minutes in a single session, while long-term exercise was implemented as 6 weeks / 30 minutes, 5 days a week. At the end of the experimental period, blood samples were taken from the aortas and gastrocnemius-soleus muscle complexes were collected under Ketamine-HCl/Xylazine-HCl (75mg/kg-10 mg/kg) anesthesia. Serum creatine kinase (CK) activity was measured using a commercial kit, and muscle damage was determined histologically by damage scoring and leukocyte infiltration. Muscle regeneration was evaluated by histological examination and immunohistochemically by obtaining an H Score for staining of Pax7, Sca1 and CD45 antibodies in the nucleus and sarcoplasm. Variables were given as mean ± standard deviation (SD). One-Way Analysis of Variance (ANOVA, post hoc: Tukey test) was used for statistical analysis. p<0.05 values were considered as statistically significant. Muscle damage was detected in the gastrocnemius-soleus complex at the 3rd hour following acute swimming exercise. Serum CK activity was also found to be statistically significantly higher in the acute 3-hour group compared to control and lower in the acute 48-hour group (p<0.05). Histologically significant muscle regeneration identified by centrally located nuclei was observed in the acute 48-hour and chronic 3-hour groups. Immunohistochemical analysis revealed an increase in the expression of Pax7, a satellite cell marker, in the acute 48-hour and chronic 3-hour groups. There was no evidence that the muscle regeneration observed in the gastrocnemius-soleus muscle complexes at the 3rd and 48th hours following acute and long-term swimming exercises was mediated by non-satellite cells. Our data confirm the positive effects of long-term exercises on muscle health and explain the mechanisms. It is anticipated that the results of this thesis may contribute to the introduction of new approaches to the prevention and treatment of muscle diseases.