MMP9 and triple-A syndrome: Levels of hypoxia-inducible factor-1α (HIF-1α) [22], matrix metalloproteinase (MMP)-2 [17], MMP-9 [17], MMP-12 [23], M1 [24] and M2 [25] macrophages, and monocyte chemotactic protein-1 (MCP-1) [26], which are increased in the human abdominal aortic wall, were also significantly increased in the aneurysmal wall (the dilated region) of the hypoperfusion-induced AAA animal model compared with the non-dilated normal region.