CD151-null mice show diminished angiogenesis, ex vivo and in vivo. (A) Thoracic aortic rings were embedded in Matrigel and incubated for 4 days. Shown are phase-contrast images of branching vessel-like structures in WT and CD151-null explants. Lengths of vessel-like structures were quantitated (n = 6; *P < .005). (B) After implantation for 7 days, sections of Matrigel plugs were stained with hematoxylin and eosin (H&E) and for endothelial marker CD34. Percentage of vascular area stained with CD34 was calculated, in 5 fields, using Scion Image software. Results are shown as the mean ± SEM. (*P < .01). Hemoglobin content was also determined (n = 5; *P < .05). Data are representative of 3 independent experiments with similar results. Scale bars represent 1 mm (A) and 100 μm (B). Bar graphs in panels A-B, and in every other figure, show mean ± SEM.