University of Washington researchers have revealed that, in mice with atherosclerosis, it is the expression of an active form of the enzyme MMP-9, by macrophages located within plaque buildup in narrowed coronary arteries, that triggers plaque rupture. This rupture can cause blood clots and block blood flow to the heart and brain, causing a heart attack or stroke. The results appear online on December 22 in advance of print publication in the January 2006 issue of the Journal of Clinical Investigation. Atherosclerosis involves the slow buildup of fatty substances, cholesterol, collagen and elastin fibers, macrophages, and other molecules in the...