SMAD3 and aneurysm: Consistent with the increased aortic size, histopathological analyses revealed apparent changes in the vessel wall architecture of Smad3−/− mice versus Smad3+/+ and Smad3+/− mice: H&E staining showed that there is marked thickening of the wall with outward remodeling: this is distinct from most aneurysms showing thinning and degradation of vessel wall.