**3. Conclusions**

*Aortic Aneurysm and Aortic Dissection*

mice [41, 43].

whether DOCA- or Aldo-salt-induced aortic aneurysms have these pathologic features, paraffin-embedded aortic cross-sections were subjected to Elastic-Van Gieson staining of elastin. Interestingly, elastin degradation was only observed in AAA induced by DOCA- or Aldo-salt [41, 43]. Immunocytochemistry studies revealed that MMP2, MMP9, F4/80 (macrophages), Ly6B2 (neutrophils), caldesmon (smooth muscle cells), terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL; apoptosis), and dihydroethidium (DHE; oxidative stress) were increased in aortas with AAA compared with that in control aortas [41, 43].

In agreement with these immunocytochemical studies, we determined mRNA expression of several inflammatory genes, including vascular cell adhesion molecule 1 (Vcam-1), chemokine (C-C motif) ligand 2 (Ccl2, also known as MCP-1), tumor necrosis factor (Tnf), and Ncf1 (also known as p47phox) in both abdominal and thoracic aortas from mice-administrated DOCA-salt or control mice. We found that Vcam-1, Ccl2, Ncf1, and Tnf were all markedly upregulated in thoracic aortas from mice-administrated DOCA-salt compared to control mice. Interestingly, Vcam-1, Ccl2, and Ncf1, but not Tnf, were also significantly upregulated by DOCAsalt in abdominal aorta from mice-administrated DOCA-salt compared to control

**2.8 Unique features of the DOCA- or Aldo-salt mouse model of aortic aneurysm**

The DOCA- or Aldo-salt mouse model exhibited several unique features that may be relevant to the human aortic aneurysm. First, DOCA- or Aldo-salt-induced aortic aneurysm required to use 10-month-old mice [41, 43] rather than 10-weekold mice (mostly used by the Ang II AAA mouse model [13, 19–23] and other chemical-induced mouse modes [17, 18, 24, 25]). Given the fact that human AAA occurs in old peoples [2, 3, 7], the DOCA- or Aldo-salt mouse model of aortic aneurysm may more resemble human AAA than other chemical-induced aortic aneurysms in this regard. Second, DOCA- or Aldo-salt-induced aortic aneurysm used wild-type C57BL/6 mice [41, 43] rather than hyperlipidemia mice (i.e., apoli-

poprotein E-deficient (ApoE<sup>−</sup>/<sup>−</sup>) used by Ang II infusion mouse models

[13, 19–23]), thus avoiding the potential confounding effects of hyperlipidemia on aortic aneurysm. Third, using Aldo, a physiological agonist of MR, rather than chemicals (i.e., calcium chloride or pancreatic elastase) to induce aortic aneurysm, highlights its potential role in the etiology of aortic aneurysm. Moreover, the plasma concentration of Aldo in mice infused with Aldo [41] could be seen in human congestive heart failure and primary aldosteronism [31, 46, 47], suggesting that the Aldo-salt AAA mouse model is a pathological model rather than a pharmacological model that would cause concerns due to the use of high doses of reagent. Finally, high salt intake was required for DOCA to induce aortic aneurysm [41], indicating that high salt intake may be a new risk factor for the development of human AAA.

**2.9 Significance and potential impact of the DOCA- or Aldo-salt mouse model of** 

We described a new mouse model of aortic aneurysm induced by administration of MR agonist DOCA or Aldo plus high salt to 10-month-old male mice and provided compelling preclinical evidence that reveals a previously unrecognized, but potentially significant, role of Aldo, MR, and high salt in the pathogenesis of AAA. It is worth pointing out that this new mouse model of aortic aneurysm could be used as a platform to study intervention including medication (i.e., we have tested the effect of ACE inhibitor (enalapril), ARB (losartan), and MR antagonist (eplerenone and spironolactone) [41]). It is also worth pointing out at least three

**82**

**aortic aneurysm**


suggesting that activation of MR is a prerequisite for DOCA- or Aldo-salt to induce aortic aneurysm, and more importantly, spironolactone and eplerenone, two clinically approved drugs, may also be effective for the treatment of some aortic aneurysm.

6.There is no correlation between blood pressure and aortic dilation or AAA formation in the DOCA- or Aldo-salt mouse model of aortic aneurysm, suggesting that DOCA-salt induces AAA independent of increased blood pressure.
