Background: Rapid repair of sarcolemmal injury is needed to maintain myofiber integrity. Compromised membrane repair contributes to skeletal muscle degeneration in common muscle diseases including Limb Girdle muscular dystrophies, Miyoshi myopathy, Myositis and Duchenne muscular dystrophy. Sarcolemmal repair requires mitochondrial redox signaling, thus redox imbalance compromises repair. Facioscapulohumeral muscular dystrophy (FSHD) is characterized by increased sensitivity to oxidative stress and is associated with muscle wasting. However, it is unclear if sarcolemmal repair is compromised in FSHD.
Objective: To characterize cell membrane repair ability of FSHD patient and muscle cells and myofibers in FSHD mouse model.
Approach: Immortalized human myoblasts from individuals with FSHD and their unaffected siblings, as well as myofibers from the biceps of the FLExDUX4 murine model of FSHD were subjected to focal injury using pulsed laser. The kinetics and success of sarcolemmal membrane repair was determined using cell impermeant dye FM-1-43 and the proportion of cells that failed to repair was calculated.
Results: Immortalized myoblasts from individuals with FSHD exhibit poor repair, resulting in elevated FM1-43 dye entry in the injured cells and a greater proportion of FSHD myoblasts failing to repair compared to healthy myoblasts. Myofibers from FLExDUX4 mouse recapitulates poor sarcolemmal repair compared to the WT myofibers.
Conclusion: Myoblasts from individuals with FSHD demonstrate poor sarcolemmal repair, which may contribute to disease progression. Further analysis of the potential relationship between increased susceptibility to oxidative stress and reduced membrane repair capacity in FSHD is warranted.