Mmp17 encodes a member of the matrix metalloproteinase family of extracellular matrix-degrading enzymes that are involved in tissue remodeling, wound repair, progression of atherosclerosis and tumor invasion. The encoded preproprotein undergoes proteolytic processing to generate a mature, zinc-dependent endopeptidase enzyme. Mice lacking the encoded protein exhibit dysfunctional vascular smooth muscle cells and altered extracellular matrix in the vessel wall leading to an increased susceptibility to angiotensin-II-induced thoracic aortic aneurysm.