MMP-2 expression (A–B) was higher in both cusp and annulus tissue compared to MMP-9 expression (C–D). Both MMP-2 and MMP-9 expression was unchanged in the cusp region (p=NS, E) and increased in the annulus region (p<0.01, E) in aged Eln+/− valves (B″, D″), as compared to WT valves (A″, C″). MMP-2 and MMP-9 are stained green; cell nuclei, blue (ToPro3). Cusps (A′ – D′), annulus (A″ – D″). Sections are oriented in the long axis. Scale bars: 60 μm (A–D); 10 μm (all others). Dotted lines isolate valve tissue from aortic and/or myocardial tissue.