Future studies will define a role for early macrophage influx and MMP activity in the development of myocardial necrosis in Smad3 KO RAS mice on the 129 background, akin to the reported role for macrophage mediated influx on the development of aortic aneurysms in Smad3 KO mice on the C57BL/6J background. This evidence concerns the gene SMAD3 and aortic aneurysm.