MMP-2 and MMP-9 are barely expressed in normal aortic tissue and are more highly expressed in early AAA than in late or ruptured AAA, suggesting that MMP-2 may be more critical for the early formation of AA.86 With inflammatory stimulation, the content of MMP-9 in aortic tissue is upregulated.87 Additionally, as the content of MMP-9 in aortic tissue increases, the content of protein hydrolases is also upregulated, which exacerbates the risk of AA rupture.88 Here, MMP2 is linked to triple-A syndrome.