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determinants of functional outcome because muscle fibers progressively
undergo an irreversible degeneration process, if reinnervation does not
occur (
Battiston, Geuna, Ferrero, & Tos, 2005; Wada, Katsuta, &
Soya, 2008
).
The study of muscle changes following denervation is attracting more
and more attention among clinicians, because of the relevance, number
of traumas, and diseases which affect the neuromotor system. However
the basic mechanisms that regulate the adaptation of muscle fibers to the
absence of innervations are not fully understood. Muscle contraction and
relaxation require the action of creatine kinase (CK), which is an
important enzyme for supplying a source of energy for the muscle. Phospho-
creatine, formed by the reaction of this enzyme, constitutes a reservoir of
high-energy phosphate which is available for quick resynthesis of adenosine
triphosphate (ATP). This high concentration of ATP is then accessible for
muscle contraction. Following muscle denervation, the level of CK and
muscle weight decreases (
Goldspink, 1976
) and induces significant changes
in acetylcholine receptor (AChR) density and distribution (
Guzzini et al.,
2008
). Preservation of the muscle endplate structures and CK content is
an important parameter for posttraumatic neuromuscular recovery.
Posttraumatic neuromuscular recovery continues to be a major challenge
in restorative medicine. Among the various proposed methods, photother-
apy has received increasing attention for enhancing nerve repair. The term
phototherapy refers to the use of light for producing a therapeutic effect on
living tissues. An extensive review of the literature (
Gigo-Benato, Geuna, &
Rochkind, 2005
) showed that more than 80% of the experimental studies
carried out so far on the use of laser phototherapy for promoting peripheral
nerve repair led to a positive outcome on posttraumatic/postoperative nerve
recovery. Our previous studies focused on the effectiveness of laser photo-
therapy in treating severely injured peripheral nerve and potential applica-
tion on denervated muscle (
Rochkind, Geuna, & Shainberg, 2009
).
We chose to investigate the influence of low-power laser irradiation on
intact muscle (
in vivo
) and muscle cell culture because it is accessible to study
the cellular mechanism of laser-muscle interaction. Cell growth and differ-
entiation are usually exclusive (
Ontell, 1975
). The myogenic cell culture
provides a good
in vitro
model for studying the metabolic processes of the
muscle tissue. During myogenesis, mononucleated cells derived from fetal
skeletal muscle, when maintained in culture, withdraw from the cell cycle
alignment and subsequently fuse to form multinucleated myotubes
(
Shainberg, Yagil, & Yaffe, 1971; Yaffe, 1969
). These myogenic processes
