MMP9 and acute myocardial infarction: In the early phase after acute myocardial infarction MMP‐9 is secreted by neutrophils and potentially by macrophages [66]; it can modulate white blood cell function and further create a positive feedback loop for neutrophil activation and chemotaxis via IL‐1 beta (interleukin), i.e. lymphocyte activating factor and IL‐8 [67].