This study evaluated the influence of growth factors on muscle regeneration when the bone is distracted, relative to the distraction rate.

The influence of bone distraction on the tibialis anterior and soleus muscles of 6-month-old Sprague-Dawley rats was evaluated. IGF-I, PDGF, and bFGF expression were used as growth markers. The rats were divided into two groups containing six rats each. In each group, the right tibia was distracted and the left tibia was used as the control. The distraction rates were 0.35 and 0.7 mm/day in the respective groups.

For the tibialis anterior, the level of IGF-I expression in the group distracted at 0.35 mm/day was significantly higher (p<0.001) but significantly lower (p<0.01) in the group distracted at 0.7 mm/day than in the control. In contrast, there was no significant change in the soleus muscle (p>0.05). In the tibialis anterior, PDGF expression was higher in the group distracted at 0.7 mm/day but this increase was not significant (p=0.145). In the soleus, the expression level was lower in the group distracted at 0.7 mm/day but the difference was not significant (p>0.05). bFGF was not expressed in the tibialis anterior or soleus.

Bone distraction promotes the release of growth factors but the amount of growth factor released in mature muscle decreases in proportion to the distraction rate. bFGF is not related to myoblast proliferation and differentiation. Moreover, the amount of muscle growth decreases with increasing rate of muscle distraction.