MMP9 and triple-A syndrome: First, we confirmed that the expressions of PAI-1, p21Cip1, MMP-2 and MMP-9 were all upregulated in human AAA tissues (Supplementary Figure 6); these data were consistent with previous findings by other groups, indicating that an increase in cell senescence, especially in the medial smooth muscle cells, was a prominent characteristic of human aneurysmal vessel wall [7, 8].