Hindlimb suspension reduces muscle regeneration.
Exposure of juvenile skeletal muscle to a weightless environment reduces growth and satellite cell mitotic activity. However, the effect of a weightless environment on the satellite cell population during muscle repair remains unknown. Muscle injury was induced in rat soleus muscles using the myotoxic snake venom, notexin. Rats were placed into hindlimb-suspended or weightbearing groups for 10 days following injury. Cellular proliferation during regeneration was evaluated using 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry and image analysis. Hindlimb suspension reduced (P < 0.05) regenerated muscle mass, regenerated myofiber diameter, uninjured muscle mass, and uninjured myofiber diameter compared to weightbearing rats. Hindlimb suspension reduced (P < 0.05) BrdU labeling in uninjured soleus muscles compared to weight-bearing muscles. However, hindlimb suspension did not abolish muscle regeneration because myofibers formed in the injured soleus muscles of hindlimb-suspended rats, and BrdU labeling was equivalent (P > 0.10) on myofiber segments isolated from the soleus muscles of hindlimb-suspended and weightbearing rats following injury. Thus, hindlimb suspension (weightlessness) does not suppress satellite cell mitotic activity in regenerating muscles before myofiber formation, but reduces growth of the newly formed myofibers.
Department of Anatomy, University of Wisconsin-Medical School, Madison 53706, USA.
P E
PE
Mozdziak
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Q
Truong
A
A
Macius
E
E
Schultz
D000818:Animals; D001835:Body Weight / Q000502:physiology; D001973:Bromodeoxyuridine / Q000378:metabolism; D004546:Elapid Venoms / Q000494:pharmacology; D006614:Hindlimb / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008938:Mitosis / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D012038:Regeneration / Q000502:physiology*; D014893:Weightlessness
D004546:Elapid Venoms; C005082:notexin; D001973:Bromodeoxyuridine