Hmox1 expression and reduction of centrally located nuclei in mdx5cv mice following treatment with sildenafil. (A) Representative Hematoxylin and Eosin (H&E) staining of tibialis anterior (TA) and diaphragm (DIA) muscle sections in mdx5cv mouse treated with sildenafil citrate. Bars: 50 μm. (B) Mdx5cv mice showed significantly more centrally located nuclei in random non-overlapping fields of H&E-stained diaphragm muscle than in strain-matched wild type. Sildenafil showed significant reduction of central nuclei in TA and DIA muscle compared with the untreated mdx5cv TA and DIA. (n = 4, 11–12 weeks old). Mdx5cv mice were given water for 7–8 weeks at a 400 mg/l concentration of sildenafil Mdx5cv and strain-matched C57Bl6/J wild type received vehicle. *P = 0.0012, n = 4, t-test, **P = 8.98328E-07, t-test, n = 4. (C and D) Upregulation of Hmox1 expression in mdx5cv mice following treatment with sildenafil. Hmox1 expression in mice treated with sildenafil was analyzed via immunoblot (*P = 0.0015, versus wild type, t-test, n = 4).