Muscle-specific transgenic overexpression of the α7β1 integrin can protect against exercise induced-injury and promote the appearance of multipotent mesenchymal-like (Sca-1+CD45-) stem cells in skeletal muscle. PURPOSE: The purpose of this study was to determine if overexpression of the α7β1 integrin also results in enhanced and/or accelerated myogenesis following a single bout of eccentric exercise. METHODS: 5-wk old, female wild type (WT) and α7 integrin transgenic (α7Tg) mice completed a single bout of downhill running exercise (-20o, 17 m/min, 60 min) and gastrocnemius-soleus complexes were collected 2, 4, and 7 d post-exercise.Myogenesis was quantified using embryonic myosin heavy chain (eMHC) expression and the presence of centrally located nuclei (CLN). RESULTS:Whereas gradual increases in eMHC expression were detected in WT mice following exercise, a 5-fold increase in eMHC+ fibers was present at 2 d post-exercise in α7Tg mice compared to α7Tg mice that did not exercise (P < 0.001).Consistent with this adaptation, WT mice had gradual increases in numbers of CLN until 7 d post-exercise, whereas α7Tg mice had a 5-fold increase in CLN levels at 2 d post-exercise (P<0.001). CONCLUSION: This study suggests that the protection from injury and increased appearance of mesenchymal stem cells observed with α7β1 integrin overexpression may directly or indirectly contribute to accelerated myogenesis following eccentric exercise. This study provides the first evidence that the α7β1 integrin participates in myogenesis acceleration.
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The α7β1 integrin accelerates exercise-induced myogenesis
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