SP07. Mechanical Stimulation Improves Functional Recovery after Skeletal Muscle Injury in Rats

PURPOSE: Skeletal muscle injury (SMI) cause by trauma or surgery can result in permanent disability and loss of function. Physical therapy is the current standard of care for SMI but long-term recovery of muscle strength has shown to be inadequate in severe SMI. Initial evidence suggests that in animals invasive mechanical stimulation can increase up to 3-fold the tetanic torque after SMI. Here, we hypothesized that mechanical stimulation can improve functional recovery after SMI by stimulating skeletal muscle regeneration and by mitigating fibrosis. METHODS: A standard excisional muscle injury (8mm ∅) was created in the left Tibialis Anterior (TA) muscle of female adult (200-250 grams) Sprague Dawley rats (n= 10/group). Post-injury, animals were either followed up with no treatment (control group) or subjected to controlled mechanical stimulation of injured muscles (experimental group). Functional recovery was measured at 14 and 28 days post-injury (PID) by measuring the TA tetanic torque and the animals’ endurance on a treadmill run. In addition, as a measure of not challenging physical activity, the distance traveled was measured by fixed-point observation using a camera.At PID 28, samples of injured TAs were processed for histology (Masson) and immunohistochemistry (markers: MHC, Col-1, CD31, CD68) to measure myocyte/fibrosis percentage composition. RESULTS: At PID 28, the tetanic torque in the experimental group was significantly higher than in controls (73.1±18.7% of pre-injury baseline vs. 47.0±23.7%, p=0.014).The resistance to fatigue in the experimental group was significantly higher than in controls (88.7±24.9% of pre-injury baseline vs. 56.6±27.5%, p=0.014).Endurance on a treadmill run was also significantly higher in the experimental group compared to controls (97.8±58.5% of pre-injury baseline vs. 40.6±35.4%; P=0.016) at the same timepoint.At histology, the treatment group showed less fibrosis and more myocyte percentage composition. CONCLUSION: In rats, mechanical stimulation promotes improves functional recovery after skeletal muscle injury. Validation of these findings in large animal models and in humans might help develop novel treatment for patients with muscle injuries caused by trauma or surgery.