Characteristics of locomotion, muscle strength, and muscle tissue in regenerating rat skeletal muscles

Abstract

Although numerous studies have aimed to elucidate the mechanisms used to repair the structure and function of injured skeletal muscles, it remains unclear how and when movement recovers following damage. We performed a temporal analysis to characterize the changes in movement, muscle function, and muscle structure after muscle injury induced by the drop-mass technique. At each time-point, movement recovery was determined by ankle kinematic analysis of locomotion, and functional recovery was represented by isometric force. As a histological analysis, the cross-sectional area of myotubes was measured to examine structural regeneration. The dorsiflexion angle of the ankle, as assessed by kinematic analysis of locomotion, increased after injury and then returned to control levels by day 14 post-injury. The isometric force returned to normal levels by day 21 post-injury. However, the size of the myotubes did not reach normal levels, even at day 21 post-injury. These results indicate that recovery of locomotion occurs prior to recovery of isometric force and that functional recovery occurs earlier than structural regeneration. Thus, it is suggested that recovery of the movement and function of injured skeletal muscles might be insufficient as markers for estimating the degree of neuromuscular system reconstitution.

A Two Stage Model of Skeletal Muscle Necrosis in Muscular Dystrophy - The Role of Fiber Branching in the Terminal Stage

“…Regenerating muscle has different functional characteristics from uninjured muscle. During regeneration, muscles display contractile differences such as reduced isometric force (Beitzel et al 2004;Stupka et al 2007;Iwata et al 2010), longer twitch contraction and relaxation times (Beitzel et al 2004;Stupka et al 2007) and a dependence of contractility upon the extracellular Ca 2+ concentration (Louboutin et al 1996). Although branched fibers are a well-documented phenomenon of regenerating muscle, only a handful of studies have examined how their physiological properties may differ from those of morphologically normal fibers (Head et al 1990(Head et al , 1992(Head et al , 2004Chan et al 2007;Lovering et al 2009;Friedrich et al 2010;Head, 2010 …”

Muscle injury in rats induces upregulation of inflammatory cytokines in injured muscle and calcitonin gene–related peptide in dorsal root ganglia innervating the injured muscle

“…In addition, Iwata et al . reported that myotubes were detected in the regenerative area, and myotubes were still clearly observed at day 21 postinjury 16. These findings indicate that muscle injury induces edema and hematoma during the acute phase of injury, but as time passes the injured muscle fibers are repaired.…”

“…Consistent with our findings, Iwata et al . reported that muscle injury induced a larger angle of ankle dorsiflexion, and the height of the calcaneus was lower in the stance phase during the acute phase after muscle injury, but these gait changes normalized during the subacute phase after muscle injury 16. Here, we evaluated gait change after a contusion injury using the CatWalk system.…”

Midkine-deficient mice delayed degeneration and regeneration after skeletal muscle injury

“…Seven regions of each HE section were photographed at 20x objective, and analyzed over the whole transverse section. In regenerating muscle, all myotubes contained in the sections from each muscle tissue were counted and the percentage of myotubes to total muscle fibers calculated (Iwata et al, 2010). The percentage of the number of myotubes to total muscle fibers of Mdk −/− mice was compared with that of Mdk +/+ mice.…”