Previous studies have focused on the 92-kD (MMP-9; gelatinase B) and 72-kD (MMP-2; gelatinase A) gelatinase/type IV collagenase, both most prominent elastolytic enzymes secreted by the AAA tissues in organ culture and in vivo, which are expressed by macrophages, vascular SMCs, fibroblasts, or ECs, most often in the areas adjacent to the infiltrated inflammatory cells [62, 66–70]. The gene discussed is MMP9; the disease is triple-A syndrome.