Experimental modeling of skeletal muscle injury is a multifaceted task. Muscle injuries are commonly divided into an
in situ necrosis type and a shearing type. In situ necrosis
injuries are characterized by necrotized muscle fibers but
intact basal laminae, whereas basal laminae, blood vessels,
and mysial sheets are also impaired in shearing-type injuries, depending on severity.23,27 CTX-induced myolysis as
applied in the present study induces a reproducible
necrosis-regeneration cycle6 while leaving blood vessels and
major parts of the basal laminae intact.17 It thus preserves
the classic satellite cell niche and likely provides a suitable
model to investigate satellite cell behavior after necrosistype injury. However, because the phases of repair have
been found to be similar between the different types of muscle injury,24 it is not at all unlikely that the CTX model is also
valid for shearing-type injuries. In agreement with this, present therapies are already mainly selected according to the
severity of the muscle injury rather than according to type.24
The results of the present study provide a clear indication that ESWT is able to accelerate the time course of
regeneration in rat skeletal muscle after acute CTX-induced
injury. Our results suggest that shock wave treatment
applied shortly after muscle damage induces measurable
effects on cellular repair mechanisms during both the initiation and maturation phases of the regeneration process.
Although the present study provides evidence for a positive
effect of ESWT on muscle repair, the exact mechanism of
interaction between shock waves and tissue remains unclear.
It has been postulated that the biological effect is based on
mechanotransduction,14 which results in specific gene expression patterns in target tissues.15 Indeed, skeletal muscle is
known to be highly responsive to mechanical stimulation,41
resulting in muscle fiber growth mediated by increased protein synthesis and/or satellite cell recruitment.20 In addition,
shock waves have been shown to upregulate a variety of signaling factors relevant to regeneration, including nitric oxide,
insulin-like growth factor, and fibroblast growth factor, in
a variety of tissues.7,9,31 It may thus be assumed that it is
a complex combination of several factors by which shock
waves act to stimulate muscle healing
