Effects of TNF-alpha on type I collagen and TGF-beta1 mRNA expression in muscle cells
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The purpose of this study was to determine whether treatment of cultured C 2 C 12 myoblasts and mytotubes with TNF-α over time (24, 48 and 72hrs) would stimulate collagen metabolism either directly or indirectly through a TGF-β1 dependent pathway. We found that TNF-α treatment of C 2 C 12 myoblasts (regardless of dose) resulted in a significant decrease in type I collagen mRNA at each time point, however there was no impact on the level of TGF-β1 mRNA. In myotubes, significant decreases in type I collagen mRNA levels were observed at 24 and 48 hours in the TNF-α treatment group, but not at 72 hours. In contrast with the myoblasts, TNF-α resulted in a significant decrease in myotube TGF-β1 mRNA levels at all three time points. These findings show that muscle cells exposed to TNF-α in vitro do not respond by increasing TGF-β1 or type I collagen mRNA expression.