Carotid Atherosclerotic Plaque Matrix Metalloproteinase‐12–Positive Macrophage Subpopulation Predicts Adverse Outcome After Endarterectomy

Background Matrix metalloproteinase‐12 (MMP‐12) promotes atherosclerosis in animal models. MMP‐12 is expressed in only a subset of foam‐cell macrophages (FCMs) in human plaques. We investigated whether the prevalence of this MMP‐12–expressing subpopulation is a prognostic indicator of adverse outcome in patients after carotid endarterectomy (CEA). Methods and Results Serial sections of culprit lesions from 236 patients who underwent CEA and had undergone 3 years of clinical follow‐up were stained immunocytochemically for MMP‐12 and for CD68, and the MMP‐12/CD68 ratio was used to quantify the MMP‐12–expressing subpopulation. A high MMP‐12/CD68 ratio correlated with a high content of lipid and total macrophages and a low content of vascular smooth muscle cells, as well as with MMP‐8 (R=0.211, P=0.001), MMP‐9 (R=0.251, P