We studied the response of
dysferlin-null and control skeletal muscle to large- and small-strain
injuries to the ankle dorsiflexors in mice. We measured contractile torque and counted fibers retaining 10-kDa
fluorescein dextran, necrotic fibers, macrophages, and fibers with central nuclei and expressing developmental
myosin heavy chain to assess contractile function, membrane resealing,
necrosis,
inflammation, and myogenesis. We also studied recovery after blunting myogenesis with X-irradiation. We report that
dysferlin-null myofibers retain 10-kDa
dextran for 3 days after large-strain injury but are lost thereafter, following
necrosis and
inflammation. Recovery of
dysferlin-null muscle requires myogenesis, which delays the return of contractile function compared with controls, which recover from large-strain injury by repairing damaged myofibers without significant
inflammation,
necrosis, or myogenesis. Recovery of control and
dysferlin-null muscles from small-strain injury involved
inflammation and
necrosis followed by myogenesis, all of which were more pronounced in the
dysferlin-null muscles, which recovered more slowly. Both control and
dysferlin-null muscles also retained 10-kDa
dextran for 3 days after small-strain injury. We conclude that
dysferlin-null myofibers can survive contraction-induced injury for at least 3 days but are subsequently eliminated by
necrosis and
inflammation. Myogenesis to replace lost fibers does not appear to be significantly compromised in
dysferlin-null mice.