Myofiber Damage Precedes Macrophage Infiltration after in Vivo Injury in Dysferlin-Deficient A/J Mouse Skeletal Muscle

Abstract

Mutations in the dysferlin gene (DYSF) lead to human muscular dystrophies known as dysferlinopathies. The dysferlin-deficient A/J mouse develops a mild myopathy after 6 months of age, and when younger models the subclinical phase of the human disease. We subjected the tibialis anterior muscle of 3- to 4-month-old A/J mice to in vivo large-strain injury (LSI) from lengthening contractions and studied the progression of torque loss, myofiber damage, and inflammation afterward. We report that myofiber damage in A/J mice occurs before inflammatory cell infiltration. Peak edema and inflammation, monitored by magnetic resonance imaging and by immunofluorescence labeling of neutrophils and macrophages, respectively, develop 24 to 72 hours after LSI, well after the appearance of damaged myofibers. Cytokine profiles 72 hours after injury are consistent with extensive macrophage infiltration. Dysferlin-sufficient A/WySnJ mice show much less myofiber damage and inflammation and lesser cytokine levels after LSI than do A/J mice. Partial suppression of macrophage infiltration by systemic administration of clodronate-incorporated liposomes fails to suppress LSI-induced damage or to accelerate torque recovery in A/J mice. The findings from our studies suggest that, although macrophage infiltration is prominent in dysferlin-deficient A/J muscle after LSI, it is the consequence and not the cause of progressive myofiber damage.

Diltiazem improves contractile properties of skeletal muscle in dysferlin-deficient BLAJ mice, but does not reduce contraction-induced muscle damage

“…We studied male mice, due to the availability of data from several published and pilot studies, on the response of control and dysferlin‐null male mice to injury by eccentric contractions (Roche et al. , , , ; Millay et al. ; Nagy et al.…”

“…As described in the Introduction, the MSFEE protocol is a refinement of the large‐strain injury (LSI) model that has been described and referenced in many publications (Roche et al. , , , ; Millay et al. ; Lovering et al.…”

“…To evaluate the general morphology of the TA and quantify myofiber damage, we performed hematoxylin and eosin (H&E) staining on 5 μ m cross sections as described (Roche et al. , ; Begam et al. ).…”

“…The in vivo data on the protective effect of DTZ against stress‐induced muscle fiber damage are of particular translational value, since dysferlin‐deficient A/J mice sustain severe delayed‐onset muscle damage, following injurious large‐strain eccentric contractions (large‐strain injury, LSI) to the tibialis anterior (TA) muscle (Roche et al. , , ). The data from A/J mice corroborate with the natural history of dysferlinopathies reported by patients, with regard to intense physical exercise and/or activity increasing muscle weakness (Angelini et al.…”

Enhanced Muscular Dystrophy from Loss of Dysferlin Is Accompanied by Impaired Annexin A6 Translocation after Sarcolemmal Disruption

“…50 Roche et al 10 showed that the Dysf-null mice on the AJ background have increased macrophage infiltration and muscle damage after large strain injury compared to A/WySnJ controls. Annexins, especially annexin A1, are linked to inflammation.…”