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Figure S1. Aortic segment preparation and image acquisition. Aortic segments containing the innominate bifurcation were removed from the proximal aorta and cut open for en face LSCM, as shown by the red dashed line along the greater curvature and base of the innominate artery. This opened segment was placed on a glass slide with the luminal side up. Composite images of the intimal layer spanning the lesser curvature in either a vertical (circumferential strip) or horizontal (lesser curvature strip) direction were created by stitching together several contiguous images captured with a 20× objective. Each image was collected with box dimensions of 600 μm. Bar, 500 μm.