Patterns of Gelatinase Activation Induced by Injury in the Murine Femoral Artery

Background: Intimal hyperplasia remains the principal lesion in the development of restenosis after vessel wall injury. Modulation of the extracellular matrix by proteases is a pivotal component of the response to injury. The aim of this study is to characterize the changes in gelatinase (MMP-2/TIMP-2 and MMP-9/TIMP-1) systems in a murine model. Methods: The murine femoral wire injury model was used in which a microwire is passed through a branch of the femoral and used to denude the common femoral artery. Pluronic gel was used to apply a proteass inhibitor (GM6001) to the exterior of the vessels. Specimens were perfusion-fixed and sections were stained with hematoxylin and eosin and Movat's stain such that morphometry could be performed by using an ImagePro system. Additional specimens of femoral artery were also harvested and snap frozen for Western blotting and zymography to allow for the study of gelatinase expression and activation. Contralateral vessels were used as controls. Results: MMP-2 activity increased significantly at day 1, peaked again at day 7, and then showed a continual decline in activity to day 56. MMP-9 activity peaked early at day 3 and declined thereafter. Protein expression for both MMP-2 and MMP-9 increased significantly after injury and both were maximal at day 14. There was an initial decrease in TIMP-1 and TIMP-2 expression and activity after injury until day 5. Both expression and activation gradually increased thereafter to level out by day 21 and correlated well with the early increases in MMP-2 and MMP-9 activity and their subsequent decline. Local application of protease inhibitor (GM6001) within a pluronic gel decreased cell proliferation, and at 14 d there was a decrease in intimal hyperplasia. Conclusions: These data demonstrate that femoral wire injury in the mouse is associated with a time-dependent increase in gelatinase activity. Cell proliferation is associated with increased MMP-2/MMP-9 activity and decreased TIMP-2/TIMP-1 activity, whereas migration is associated with increased in MMP-2 activity. Modulation of proteases and their inhibitors control the vessels' response to injury.