Photos of rat balloon-injured carotid arteries at various times post-injury treated with Evans blue dye (re-drawn from Ref. 7). Tissues were treated with Evans blue (0.5 ml of a 5% solution) in situ 10 min prior to sacrifice, perfusion-fixed, harvested intact, split longitudinally, and pinned out on a silicon-padded dish for analysis. A shows a contralateral uninjured right carotid artery 2 weeks following injury on the left carotid artery. Absence of Evans blue staining indicates an intact endothelial layer. B shows an injured left carotid artery 30 min post-injury, and complete loss of the endothelial lining is indicated by complete Evans blue staining of the sub-endothelial matrix along the entire length of the vessel. C and D illustrate two carotid arteries with partial endothelial regrowth from the border zones 2 weeks post-injury. White (unstained) regions at the proximal and distal ends of these vessels are indicated by arrowheads and suggest that endothelial cells have partially regenerated into the central injured section at this time point.