New models of regenerating VML injured rat skeletal muscle : single muscle fiber injection and resistance exercise

Volumetric muscle loss (VML) is a traumatic soft tissue injury that is common in recent battle fields and causes permanent losses of muscle mass and function in affected muscle. Since a new VML injury model has been developed in our lab which defects large mass of rat lateral gastrocnemius (LGAS), several sources of extracellular matrix (ECM) and stem cells including adipose tissue derived stem cells and mesenchymal stem cells have been utilized to enhance the regeneration of defected muscle. In the current study, regenerative effects of resistance exercise and satellite cells injection after the VML injury were tested. Satellite cells transplanted via single muscle fiber injection significantly enhanced generation of a specific force of defected muscle possibly via suppressing fibrotic tissue build-up and inducing significant hypertrophy of regenerating muscle at the sites of injury. However it did not increase muscle mass and tetanic force of the defected LGAS. Resistance exercise intervention after the injury improved all morphological and functional recoveries. Defected muscle mass and functions (tetanic and specific forces) were significantly increased in the resistance exercised group compared to the non-exercised. Cross sectional area (CSA) of mature and regenerating muscle fibers in injured muscle were also significantly increased by the resistance training. Single muscle fiber injection with resistance exercise did not further increase muscle mass or functions, but it had an impact on decreasing accumulation of the non-functional (fibrotic tissue and residual injured) area. These results indicate that resistance exercise is a great rehabilitative intervention after traumatic muscle injury to enhance muscle mass and function with or without satellite cells injection.Kinesiology and Health Educatio