(A) SEM analysis of rat femoral arteries transduced with Ad-Null. The arterial wall shows ridges formed due to contractions in the underlying smooth muscle cells (top panel, scale bar: 50 μm). Higher magnification detail of the Ad-Null–infected artery demonstrates the continuous endothelial monolayer (bottom panel, scale bar: 10 μm). (B) SEM analysis of Ad-FGFR1DN–transduced rat femoral artery. The area with remaining endothelial cells is shown (left panels, scale bars: 50 μm [top]; 10 μm [bottom]). Endothelial cells are swollen and have lost contacts with neighboring cells. Underlying matrix layer is partially exposed (white arrows). Area demonstrating severe loss of the endothelium with exposure of the subjacent basement membrane is also shown (right panels, scale bar: 50 μm [top]). Higher magnification shows a few cells, presumably platelets by size, adhering to the vessel wall (white arrowheads) (right panels, scale bar: 10 μm [bottom]). (C) Transmission electron microscopy analysis of Ad-Null–transduced rat femoral artery (day 2). Adjacent endothelial cells form a tightly sealed junction indicated by black arrows. Scale bar: 500 nm. (D) Ad-FGFR1DN–transduced artery (day 1). Scale bar: 2 μm. Inset: a gap is formed between endothelial cells. Arrow (inset) indicates open cell-cell junction. Scale bar: 500 nm. (E) Ad-FGFR1DN–transduced artery (day 2) shows an open endothelial junction (black arrows). A platelet (PLT) adheres to the open space and extends a cellular process (white arrowhead). Scale bar: 500 nm. (F) Ad-FGFR1DN–transduced artery showing a wide gap in the endothelium (black arrow) and an EC detaching from the basement membrane. Scale bar: 2 μm.