Thrombus versus wall biological activities in experimental aortic aneurysms.

BACKGROUND/AIM The intraluminal thrombus (ILT) is considered to participate in abdominal aortic aneurysm (AAA) evolution. To assess whether this role proceeds via ILT influence on biological activity of the AAA wall, we studied the relationships between the levels of some relevant proteases and microparticles (MP) released by ILT versus wall in rat experimental AAAs. METHODS AND RESULTS Two weeks after elastase perfusion, ILT and AAA wall were incubated in cell culture medium and studies were performed on conditioned media. As shown by gelatin zymography, ILT released higher amounts of MMP9 than the wall, whereas the level of MMP2 activation (active/pro) was similar. Levels of elastase and urokinase plasminogen activator, plasmin and MPs, determined, respectively, by casein zymography, substrate hydrolysis and flow cytometry, were higher in ILT than in wall. Aneurysm diameter positively correlated with wall MMP9 levels, MMP2 activation, plasmin activity and MP release. Moreover, wall and ILT levels of pro- and active forms of MMP2, elastase and plasmin were positively correlated. Wall levels of MMP2 activation and plasmin activity also correlated with ILT weight. CONCLUSION The present data suggest that, in this experimental model, ILT may contribute to AAA evolution via its influence on the level of aneurysmal wall protease activity.