The aim of this study was to determine the role of P-selectin, an adhesion molecule found on the surface of activated platelets and endothelial cells during experimental aortic aneurysm formation. Infrarenal abdominal aortas of C57 black wild-type (WT) mice and P-selectin knockout (PKO) mice were measured in situ and then perfused with porcine pancreatic elastase (0.332 U mL). Whole blood was drawn from the tail artery on day 2 pre-perfusion to determine total and differential white blood cell (WBC) counts. On day 14 postperfusion, aortic diameters (AD) of WT mice ( N 19) and PKO mice ( N 9) were measured. An aortic aneurysm was defined as a 100 or greater increase in AD from pre-perfusion measurement. Immunohistochemistry, including H&E, trichrome and von Gieson staining, was performed on harvested aortic tissue. Statistical analysis was performed by t -test and Fisher's exact test. There were no significant differences in peripheral leukocyte counts at baseline between the two groups. WT mice had significantly larger AD compared to PKO mice at day 14 postperfusion (116 vs. 38 , P < 0.001). Aortic aneurysm penetrance was 52 in WT mice, while 0 ( P 0.01) of PKO mice formed aneurysms. On histologic examination, WT mouse aortas were associated with a significant inflammatory response and degradation of elastin and collagen fibers, while PKO mouse aortas lacked signs of inflammation or vessel wall injury. P-selectin deficiency attenuates aneurysm formation in the elastase aortic perfusion model. This was associated with a blunting of the inflammatory response and preserved vessel wall intergrity following elastase perfusion in the P-selectin knockout mice. Further investigation to elucidate the independent contributions of endothelial cell and platelet P-selectin in experimental aortic aneurysm formation is required
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