Fig 2.

Histologic review of inducible abdominal aortic aneurysm (AAA) murine models. Histologic cross-sections from 28 days after aneurysm induction are presented with hematoxylin and eosin staining. The normal mouse infrarenal aorta is approximately 500 μm in diameter when perfused and contains a medial layer with four to five elastic lamellar units. One layer of endothelial cells lines the inner luminal layer, and a surrounding adventitia is composed of mainly connective tissue. In the external periadventitial elastase application (ePPE) (β-aminopropionitrile [+BAPN]) model, the adventitia and media show cellular enrichment and the medial elastin breakdown. Most notably is the intraluminal thrombus (ILT). In contrast, for the angiotensin II model (AngII) aorta, the media remains mostly intact and cellular enrichment is more prominent in the adventitia. Note the thrombus formation in between the media and the adventitia (washed out in parts owing to fixation). In the PPE model, the media is mostly disrupted, and the adventitia shows increased fibrosis, signs of chronic inflammation and angiogenesis (not shown). Finally, in the CaCl₂ model, the elastic fibers remain intact but thicken along with the adventitia and exhibits signs of fibrosis and inflammatory infiltrates in all layers. Scale bar = 100 μm; original magnification ×10; histologic images are courtesy of the authors.