Proteome Dynamics Rapidly Detect Protein Synthetic and Fibrogenic Changes Following Eccentric Contraction‐Induced Muscle Damage in <i>mdx</i> Mice

Turnover rates of the skeletal muscle proteome (proteome dynamics) may reveal pathophysiologic mechanisms and identify markers that change rapidly, for clinical monitoring in disease. Here, we used high resolution LC/MS/MS of tryptic peptides to compare the fractional synthetic rates (FSR) of hundreds of proteins in gastrocnemius (gastroc) muscles of 9‐11 month‐old wild type (wt) and mdx mice. One day after damage‐inducing hind‐limb eccentric muscle contraction that resulted in 40‐60% reduced contractile force, mice were labeled with heavy water (D 2 O) for 12 days. We also measured the FSR and content of hydroxyproline (OHP), representing total collagen, in the gastroc and diaphragm. Basal (non‐injured) mdx gastroc and diaphragm muscles had significantly higher FSRs for most proteins compared to wt mice. Basal OHP content and collagen abundance were also significantly increased from mdx vs wt. During the repair phase in response to injury, wt and mdx gastrocs had distinct dynamic proteomic signatures across several myofibril, extracellular matrix, cytosolic and mitochondrial protein ontologies. OHP and collagen FSR were also significantly increased in the damaged gastroc compared to contralateral limb. Thus, proteome dynamic measurements reveal increases in fibrosis and generalized skeletal muscle protein FSR in mdx vs wt mice, and repair following eccentric muscle damage is associated with unique dynamic proteomic signatures that include increased fibrogenesis. These findings hold promise for monitoring the response of muscle damage to therapy in muscle diseases, including muscular dystrophies.