Downhill Running Induced Myogenic And Cell-Cycle Regulatory Factor mRNA Expression In Mice

Abstract

0059 Downhill running induces skeletal muscle injury that can activate quiescent muscle satellite cells (SC) in rats. Regulation of SC activity by myogenic and cell cycle regulatory factors is essential for skeletal muscle regeneration. However, little is known about the sequential expression of myogenic and cell cycle regulatory factors after a novel session of downhill running in mice. PURPOSE: To determine the expression of myogenic and cell cycle regulatory factors at the onset and after 72 hr of recovery from downhill running in mice. METHODS: Forty-one C57BL6 mice exercised on a treadmill at 25 m×min−1 and −14 % grade for 150 min or served as non-exercise controls. Mice were sacrificed immediately (0), 12, and 72 h post-run. Soleus muscle mRNA abundance for the myogenic regulatory factors MyoD and myogenin and the cell cycle regulatory factors Cyclin D1 and p21 were assessed by RT-PCR. Data were analyzed by ANOVA. RESULTS: SOL muscle wt to body wt ratio was not different from control at any time point post exercise. Cyclin D1, MyoD, and myogenin mRNA abundance was not significantly different from control at any time point. However, p21 mRNA abundance was 2.5 and 2.8 fold greater at 0 h and 12 h post exercise (p<0.05), and returned to control levels by 72 h. CONCLUSIONS: The absence of Cyclin D1, MyoD, or myogenin induction at 72 h suggests downhill running did not induce detectable SC proliferation in the mouse soleus muscle. However, the early p21 induction may reflect resident macrophage activation in the exercised soleus muscle. Funded by Glenn/AFAR Student Award