All statistical analyses were performed using SPSS 17.0 software. Data are expressed as mean ± SE, and mean values were compared using the Student's t-test and ANOVA. Data were as mean ± SE. Western blot, ELISA, PKG activity, and cGMP analysis were examined using one-way ANOVA. The χ2 and Fisher's exact test were used to analyze the differences of fibrosis grades in each group. Values of P < 0.05 were considered statistically significant.