Common carotid arteries of HCII^−/− mice 3 weeks after mechanical dilation with a beaded wire probe. (A,C) Cross sections stained with Verhoeff van Gieson stain for elastin. (B,D) Cross sections stained with a monoclonal anti–α-smooth muscle actin IgG. (C,D) Injured (left) arteries. (A,B) Contralateral uninjured (right) arteries. IEL indicates internal elastic lamina; EEL, external elastic lamina.