Dynamic Proteomic Responses to Skeletal Muscle Damage and Repair in Mice

Skeletal muscle is an innately plastic organ that responds to damage in an organized and highly conserved manner. We measured turnover rates across the skeletal muscle proteome following physiological muscle injury and repair in young male mice. Animals were challenged by a bout of 60 unilateral eccentric contractions during which hind limb plantarflexor muscles were forcibly lengthened while being concomitantly stimulated to contract. This induced an immediate 30% isometric force deficit 24‐hrs after injury, with functional restoration in 4 weeks. To determine whether changes in protein kinetics accompanied alterations in limb function, we labeled mice with D 2 O at varying time points post‐injury (day 0‐1, 1‐3, 3‐7, 8‐13 and 2‐12), and performed high‐resolution LC/MS/MS of muscle digests to measure fractional synthetic rates (FSR) of hundreds of proteins. Protein kinetics revealed distinct time‐dependent signatures in muscle in response to eccentric damage. With the notable exceptions of desmin and a few other proteins, FSRs of many myofibrillar and extracellular matrix (ECM) proteins were significantly decreased at both 0‐1 and 1‐3 days after injury. In contrast, FSR of myofibrillar and ECM proteins were significantly increased after day 3, indicating enhanced remodeling of the contractile apparatus. Similar changes were seen in many mitochondrial and cytosolic proteins in the repair phase. In conclusion, dynamic proteomics represents a powerful technique to explore temporal responses to skeletal muscle damage and recovery in mice, with potential for development of robust biological and PD markers of repair in clinical settings.