Figure 6A demonstrates a marked reduction in macrophage infiltration in the elastase-perfused aortae, particularly in the medial layer, harvested from post-elastase + Nec-1s-treated mice. MMP9, produced primarily by inflammatory cells, plays important roles in aneurysm pathogenesis38. Consistent with the reduction of macrophage infiltration, immunostaining analysis revealed that MMP9 was reduced in both medial and adventitial layers of aortae from post-elastase Nec-1s-treated mice (Fig. 6B). Here, MMP9 is linked to aneurysm.