MMP9 and triple-A syndrome: Numerous biological factors have been identified that contribute to AAA occurrence, e.g., serum elastin peptides (SEP), plasmin-antiplasmin (PAP) complexes, metalloproteinase-2 (MMP-2), metalloproteinase-9 (MMP-9), P-elastase, cystein C, tissue plasminogen activator (tPA), interferon-gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), interleukin-8 (Il-8), interleukin-6 (Il-6), macrophage migration inhibitory factor (MIF), osteopontin, osteoprogerin, fibrynogen, homocysteine, Staphylococcus sp., Chlamydophila pneumoniae, Treponema pallidum, and arachidonic acid [3].