Hepatocyte Growth Factor in Mouse Soleus Muscle Increases with Reloading after Unloading

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Hepatocyte growth factor (HGF) has been suggested as a mitogen for skeletal muscle satellite cells and participates in skeletal muscle hypertrophy. The present study assessed HGF levels in mouse soleus and plantaris muscles during 14 days of tail suspension and 3 days of reloading using the enzyme-linked immunosorbent assay. Immunohistochemical analyses were used to determine the locations of HGF, its receptor (c-Met) and proliferating cell nuclear antigen. In normal mice, HGF contents were 4.4 ± 0.5 ng/g tissue in the soleus muscle and 5.9 ± 1.2 ng/g tissue in the plantaris muscle, significantly higher than in the soleus muscle. HGF level in the soleus muscle was increased 314% from normal by reloading. HGF and c-Met were expressed in small cells contiguous to muscle fibers. Cells in similar positions displayed reactivity for PCNA, suggesting that these represent activated satellite cells. Thus, production of HGF protein appears to stimulated in satellite cells during recovery from disuse atrophy.