Chronic sildenafil treatment normalizes TNFα and decreases MMP-13 expression, but does not impact TGFβ1 in mdx diaphragms. The impact of sildenafil on regulators of inflammation (TNFα) and fibrosis (TNFα, MMP-13, TGFβ1) was evaluated at the transcript level by quantitative PCR. (A) TNFα expression was elevated 3.2-fold in mdx diaphragm tissue, but normalized to wild-type levels by sildenafil treatment. (B) Profibrotic TGFβ1 transcript expression was substantially elevated in mdx diaphragms 5.8-fold, but unaffected by sildenafil treatment. (C) MMP-13 expression was increased 2.7-fold in mdx diaphragm and was also significantly reduced by sildenafil. Wild-type vehicle- (n = 5), wild-type sildenafil- (n = 3), mdx vehicle- (n = 6), and sildenafil-treated mdx mice (n = 9).