Masson staining results also showed that the level of collagen fiber in the DCM group was higher than that in the Control group, and that in the Ad-PRR group was higher than that in the Ad-EGFP group (Figure 4D), suggesting that the overexpression of PRR significantly aggravated the fibrosis level in the DCM myocardium. This evidence concerns the gene ATP6AP2 and familial dilated cardiomyopathy.