Matrix Metalloproteinase-13/Collagenase-3 Deletion Promotes Collagen Accumulation and Organization in Mouse Atherosclerotic Plaques

BACKGROUND: Interstitial collagen plays a crucial structural role in arteries. Matrix metalloproteinases (MMPs), including MMP-13/collagenase-3, likely contribute to collagen catabolism in atherosclerotic plaques. METHODS AND RESULTS: To test the hypothesis that a specific MMP-collagenase influences the development and structure of atherosclerotic plaques, this study used atherosclerosis-susceptible apolipoprotein E-deficient mice that lack MMP-13/collagenase-3 (Mmp-13(-/-)/apoE(-/-)) or express wild-type MMP-13/collagenase-3 (Mmp-13(+/+)/apoE(-/-)). Both groups consumed an atherogenic diet for 5 (n=8) or 10 weeks (n=9). Histological analyses of the aortic root of both groups revealed similar plaque size and accumulation of smooth muscle cells (a collagen-producing cell type) and macrophages (a major source of plaque collagenases) after 5 and 10 weeks of atherogenic diet. By 10 weeks, the plaques of Mmp-13(-/-)/apoE(-/-) mice contained significantly more interstitial collagen than those of Mmp-13(+/+)/apoE(-/-) mice (P<0.01). Furthermore, quantitative optical analyses revealed thinner and less aligned periluminal collagen fibers within the plaques of Mmp-13(+/+)/apoE(-/-) mice versus those from Mmp-13(-/-)/apoE(-/-) mice. CONCLUSIONS: These data support the hypothesis that MMP-13/collagenase-3 plays a vital role in the regulation and organization of collagen in atherosclerotic plaques.