Light microscopic analysis (original magnification ×200) of sections of noninjured control arteries and of sections taken from the center of injured arteries (position 3 in the inset) after 1 week in MMP-3^−/− mice. Staining is performed with hematoxylin-eosin (panels a and b) or with antiserum against MMP-2 (panels c and d) or against MMP-9 (panels e and f). The inset shows a longitudinal section through the artery, and the arrows indicate the presumed migration of smooth muscle cells. Positions 1 and 5 correspond to normal sections, positions 2 and 4 to the borders of the injury, and position 3 to the center of the injury (modified from Carmeliet et al26). The arrows and arrowheads indicate the internal and external elastical lamina, respectively.