PHYSIOLSCI : Vol. 58 (2008) , No. 6 397-404

Functional Overloading Facilitates the Regeneration of Injured Soleus Muscles in Mice

Shigeta Morioka¹⁾²⁾, Katsumasa Goto¹⁾³⁾, Atsushi Kojima²⁾, Toshihito Naito¹⁾²⁾, Yusuke Matsuba²⁾, Tatsuo Akema¹⁾, Hiroto Fujiya⁴⁾, Takao Sugiura⁵⁾, Yoshinobu Ohira⁶⁾, Moroe Beppu²⁾, Haruhito Aoki²⁾ and Toshitada Yoshioka¹⁾⁷⁾

1) Department of Physiology, St. Marianna University School of Medicine
2) Department of Orthopaedic Surgery, St. Marianna University School of Medicine
3) Laboratory of Physiology, Toyohashi SOZO University
4) Department of Sports Medicine, St. Marianna University School of Medicine
5) Faculty of Education, Yamaguchi University
6) Graduate School of Medicine, Osaka University
7) Hirosaki Gakuin University

Abstract: The effect of functional overloading on the regenerating process of injured skeletal muscle was investigated in 10-week-old male mice (C57BL/6J). Functional overloading on soleus of both hindlimbs was performed by cutting the distal tendons of plantaris and gastrocnemius muscles for 2 weeks before cardiotoxin (CTX) injection as the preconditioning and also during 10 weeks of recovery. To activate the necrosis- regeneration cycle, 0.1 ml of 10-μM CTX was injected into soleus muscle. The mean values of absolute muscle weight and the percentage of Pax7-positive nuclei in soleus were increased by the preconditioning. These values, as well as total muscle protein content, in the group with CTX injection plus overloading were larger than in the group with CTX injection alone. Fibers with central nucleus were noted in the group with CTX injection with or without overloading. The rate of disappearance of fibers having central nucleus during recovery was stimulated by overloading. Histological analyses revealed that the regeneration of injured soleus muscle with overloading proceeded more rapidly than the muscle without overloading. These results, in combination with previous lines of evidence, strongly suggest that functional overloading may facilitate the regeneration of injured skeletal muscles.

Key words: satellite cell, skeletal muscle, regeneration, loading