Gene expression profiling of skeletal muscle after volumetric muscle loss

Volumetric muscle loss (VML), usually occurring following traumatic injury, results in a composite loss of muscle mass. These injuries manifest as decreased strength and functional impairments. Clinically, these injuries often heal with fibrosis, as opposed to skeletal muscle regeneration. This study examines the healing patterns of a skeletal muscle following VML in a murine model. Eight-week old male C57BL/6J mice used in the study underwent either bilateral VML injury or cryoinjury, a widely used model known to induce skeletal muscle regeneration. Skeletal muscle was harvested at 2 and 4 weeks following injury and subjected to histological analysis. H&E staining demonstrated skeletal muscle regeneration following cryoinjury, but not VML, at either timepoint post-injury. Additionally, samples were analyzed using a wound-healing PCR array to identify differentially regulated genes of interest in VML and cryoinjury, as compared to noninjured controls. The gene array data further demonstrated prolonged inflammation and increased pro-fibrotic activity in the VML injured muscles, as compared to cryoinjury. In addition, IGF1, a known myogenic factor, was significantly decreased following VML, as compared to cryoinjury, in both ELISA and PCR. This study offers an insight into the pathophysiology of VML injury and reveals a gene profile of a nonregenerating skeletal muscle.