Gravitational unloading inhibits the regenerative potential of atrophied soleus muscle in mice.
OBJECTIVE
The present study was performed to investigate the influence of unloading on the regeneration of atrophied and injured skeletal muscle.


METHODS
Male mice (C57BL/6J), aged 8 weeks, were used. Cardiotoxin (CTX) was injected into soleus muscles bilaterally. Gravitational unloading on soleus muscle was performed by hind limb suspension for 2 weeks before and additionally 6 weeks after CTX injection in one group. Soleus muscles in the remaining groups were loaded keeping the mice in the cages and were dissected 14, 28 and 42 days after the injection.


RESULTS
Recovery of the wet weight and protein content of soleus in the CTX-injected group was inhibited by unloading. Increase in satellite cell number, induced by CTX injection and loading, was also inhibited by unloading. Disappearance of infiltration of mononucleated cells into the necrotic area was also delayed. This phenomenon suggests that regeneration, which is indicated by the appearance of fibres with central nuclei, was inhibited by unloading.


CONCLUSIONS
Results suggested that loading plays an important role in the activation of the regenerating potential of injured skeletal muscle.
Matsuba
Y
Y
Department of Orthopaedic Surgery, St Marianna University School of Medicine, Kawasaki, Japan.
Goto
K
K
Morioka
S
S
Naito
T
T
Akema
T
T
Hashimoto
N
N
Sugiura
T
T
Ohira
Y
Y
Beppu
M
M
Yoshioka
T
T
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D001835:Body Weight / Q000502:physiology; D054715:Cardiotoxins / Q000494:pharmacology; D002452:Cell Count; D002465:Cell Movement / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D019417:Hindlimb Suspension / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D009124:Muscle Proteins / Q000032:analysis; D018482:Muscle, Skeletal / Q000737:chemistry / Q000187:drug effects / Q000473:pathology / Q000502:physiology*; D009133:Muscular Atrophy / Q000139:chemically induced*; D009929:Organ Size / Q000502:physiology; D051763:PAX7 Transcription Factor / Q000378:metabolism; D010586:Phagocytes / Q000378:metabolism / Q000473:pathology; D012038:Regeneration / Q000502:physiology*; D032496:Satellite Cells, Skeletal Muscle / Q000473:pathology; D016474:Weight-Bearing / Q000502:physiology
D054715:Cardiotoxins; D009124:Muscle Proteins; D051763:PAX7 Transcription Factor; C497322:Pax7 protein, mouse; D000135:Acid Phosphatase