Establishment of a New Abdominal Aortic Aneurysm Model in Rats by a Retroperitoneal Approach.

Constructing an ideal model of abdominal aortic aneurysm (AAA) is of great significance to elucidate its complex pathogenesis. Therefore, we introduce a new and simple method to simulate human AAA and construct a rat AAA model through a retroperitoneal approach. Forty healthy adult Sprague Dawley (SD) rats were randomly divided into a control group, elastase + calcium chloride group (PPE+CaCl2), elastase group (PPE), and elastase + beta aminopropionitrile group (PPE+BAPN) according to a male-female ratio of 1:1, with 10 rats in each group. A retroperitoneal approach was used to free the infrarenal abdominal aorta in all four groups. In the PPE + CaCl2 group, 0.1 ml of elastase (approximately 5 U) was perfused into the arterial cavity for 20 min, and 1.0 mol/L calcium chloride was infiltrated out of the arterial cavity for 10 min. In the PPE group, 0.1 mL of elastase (approximately 5U) was perfused into the arterial cavity for 20 min, and normal saline was infiltrated out of arterial cavity for 10 min; the PPE + BAPN group combined with 0.3% BAPN drinking water/day on the basis of PPE group; the control group was treated with saline instead of elastase and calcium chloride. Abdominal aortic specimens were collected after 4 weeks of feeding. The diagnostic criteria of AAA were 50% dilation of the abdominal aorta or rupture of the aneurysm at 4 weeks after the operation. Histopathology, immunohistochemistry, quantitative PCR (qPCR), western blotting assay, gelatine zymogram, and other methods were used. The operation time of the four groups was controlled at approximately 40 min, and the success rate of the operation was 100%. Survival rate: Control Group (100%) = PPE Group (100%) > PPE + CaCl2 Group (90%) > PPE + BAPN Group (40%); Aneurysm formation rate: PPE + BAPN Group (100%) > PPE + CaCl2 Group (80%) > PPE Group (60%) > Control Group (0%); Aneurysm rupture rate: PPE + BAPN group (60%) > PPE + CaCl2 group (12.5%) > PPE group (0%);Inflammatory cells (macrophages, T cells, B cells, dendritic cells) infiltrated in different degrees in the PPE + CaCl2, PPE and PPE + BAPN groups. Vascular thickness, elastic fiber content, collagen fiber content, and vascular smooth muscle cell content in the PPE + CaCl2 group and PPE + BNPA group were significantly lower than those in Control group (P < 0.05). The content of elastic fibers and vascular smooth muscle cells in the PPE group were significantly lower than that in Control group (P < 0.05). The expression and activity of matrix metalloproteinase 2 (MMP2) and MMP9 in the PPE + CaCl2 group, PPE group, and PPE + BNPA group were significantly higher than those in the control group (P < 0.05). A new, simple, and reproducible rat AAA model can be constructed by a retroperitoneal approach. The pathological features of the three models are effective simulation of human AAA inflammatory cell infiltration, protease activity enhancement, and extracellular matrix destruction. The PPE+ CaCl2 model has the advantages of a high survival rate, high aneurysm formation rate, good stability, and reproducibility. It is an ideal animal model for studying the pathogenesis of AAA. The PPE + BAPN model can simulate the characteristics of spontaneous rupture of aneurysms. It is an ideal animal model to study the mechanism of AAA rupture.

Zhu JX ，Tang QQ ，Zhou C ，Shi XC ，Yi SY ，Yang Y ... -  《Frontiers in Cardiovascular Medicine》

A novel chronic advanced stage abdominal aortic aneurysm murine model.

The purpose of this study was to establish a reliable, chronic model of abdominal aortic aneurysm (AAA). Wild-type 8-week-old C56BL/6 male mice (n = 120) were equally divided into three groups: (1) BAPN group: 0.2% 3-aminopropionitrile fumarate salt (BAPN) drinking water was provided to mice 2 days before surgery until the end of study. Sham aneurysm induction surgery was performed using 5 μL of heat deactivated elastase. (2) Elastase group: mice were given regular drinking water without BAPN. During aneurysm induction surgery, 5 μL of the active form of elastase (10.3 mg protein/mL, 5.9 U/mg protein) was applied on top of the infrarenal abdominal aorta adventitia for 5 minutes. (3) BAPN+elastase group: mice were given BAPN drinking water and the active form of elastase application, as above. On postoperative days 7, 14, 21, 28, and 100, aortic samples were collected for histology, cytokine array, and gelatin zymography after aortic diameter measurement. Compared with the elastase group, the BAPN+elastase group had a higher AAA formation rate (93% vs 65%; P < .01) with more advanced AAAs (25 of 42 vs 1 of 40 for stage II and III; P < .001). Aneurysms from the BAPN+elastase group demonstrated persistent long-term growth (221.5% ± 36.6%, 285.8% ± 78.6%, and 801% ± 160% on days 21, 28, and 100, respectively; P < .001), with considerable thrombus formation (54%) and rupture (31%) at the advanced stages of AAA development. Cytokine levels (pro-matrix metalloproteinase 9, interleukin-1β, interleukin-6, chemokine [C-C motif] ligand 5, triggering receptor expressed on myeloid cells 1, monocyte chemotactic protein 1, and tissue inhibitor of metalloproteinase 1) in the BAPN+elastase group were higher than in the elastase group on day 7. After day 7, cytokine levels returned to baseline, with the exception of elevated matrix metalloproteinase 2 activity. By histology, CD3-positive T cells in the BAPN+elastase group were elevated on days 28 and 100. A combination of oral BAPN administration and periaortic elastase application induced a chronic, advanced-stage AAA with characteristics of persistent aneurysm growth, thrombus formation, and spontaneous rupture. Future studies should use this model, especially for examining tissue remodeling during the late stages of aneurysm development.

Lu G ，Su G ，Davis JP ，Schaheen B ，Downs E ，Roy RJ ，Ailawadi G ，Upchurch GR Jr ... -  《-》

Mechanical and matrix effects of short and long-duration exposure to beta-aminopropionitrile in elastase-induced model abdominal aortic aneurysm in mice.

Evaluate the mechanical and matrix effects on abdominal aortic aneurysms (AAA) during the initial aortic dilation and after prolonged exposure to beta-aminopropionitrile (BAPN) in a topical elastase AAA model. Abdominal aortae of C57/BL6 mice were exposed to topical elastase with or without BAPN in the drinking water starting 4 days before elastase exposure. For the standard AAA model, animals were harvested at 2 weeks after active elastase (STD2) or heat-inactivated elastase (SHAM2). For the enhanced elastase model, BAPN treatment continued for either 4 days (ENH2b) or until harvest (ENH2) at 2 weeks; BAPN was continued until harvest at 8 weeks in one group (ENH8). Each group underwent assessment of aortic diameter, mechanical testing (tangent modulus and ultimate tensile strength [UTS]), and quantification of insoluble elastin and bulk collagen in both the elastase exposed aorta as well as the descending thoracic aorta. BAPN treatment did not increase aortic dilation compared with the standard model after 2 weeks (ENH2, 1.65 ± 0.23 mm; ENH2b, 1.49 ± 0.39 mm; STD2, 1.67 ± 0.29 mm; and SHAM2, 0.73 ± 0.10 mm), but did result in increased dilation after 8 weeks (4.3 ± 2.0 mm; P = .005). After 2 weeks, compared with the standard model, continuous therapy with BAPN did not have an effect on UTS (24.84 ± 7.62 N/cm2; 18.05 ± 4.95 N/cm2), tangent modulus (32.60 ± 9.83 N/cm2; 26.13 ± 9.10 N/cm2), elastin (7.41 ± 2.43%; 7.37 ± 4.00%), or collagen (4.25 ± 0.79%; 5.86 ± 1.19%) content. The brief treatment, EHN2b, resulted in increased aortic collagen content compared with STD2 (7.55 ± 2.48%; P = .006) and an increase in UTS compared with ENH2 (35.18 ± 18.60 N/cm2; P = .03). The ENH8 group had the lowest tangent modulus (3.71 ± 3.10 N/cm2; P = .005) compared with all aortas harvested at 2 weeks and a lower UTS (2.18 ± 2.18 N/cm2) compared with both the STD2 (24.84 ± 7.62 N/cm2; P = .008) and ENH2b (35.18 ± 18.60 N/cm2; P = .001) groups. No differences in the mechanical properties or matrix protein concentrations were associated with abdominal elastase exposure or BAPN treatment for the thoracic aorta. The tangent modulus was higher in the STD2 group (32.60 ± 9.83 N/cm2; P = .0456) vs the SHAM2 group (17.99 ± 5.76 N/cm2), and the UTS was lower in the ENH2 group (18.05 ± 4.95 N/cm2; P = .0292) compared with the ENH2b group (35.18 ± 18.60 N/cm2). The ENH8 group had the lowest tangent modulus (3.71 ± 3.10 N/cm2; P = .005) compared with all aortas harvested at 2 weeks and a lower UTS (2.18 ± 2.18 N/cm2) compared with both the STD2 (24.84 ± 7.62 N/cm2; P = .008) and ENH2b (35.18 ± 18.60 N/cm2; P = .001) groups. Abdominal aortic elastin in the STD2 group (7.41 ± 2.43%; P = .035) was lower compared with the SHAM2 group (15.29 ± 7.66%). Aortic collagen was lower in the STD2 group (4.25 ± 0.79%; P = .007) compared with the SHAM2 group (12.44 ± 6.02%) and higher for the ENH2b (7.55 ± 2.48%; P = .006) compared with the STD2 group. Enhancing an elastase AAA model with BAPN does not affect the initial (2-week) dilation phase substantially, either mechanically or by altering the matrix content. Late mechanical and matrix effects of prolonged BAPN treatment are limited to the elastase-exposed segment of the aorta. This paper explores the use of short- and long-term exposure to beta-aminopropionitrile to create an enhanced topical elastase abdominal aortic aneurysm model in mice. Readouts of aneurysm severity included loss of mechanical stability and vascular extracellular matrix composition reminiscent of what is seen in the course of human disease. Additionally, we show that the thoracic aorta, unlike the findings below the renal arteries, is not damaged in our animal model.

Gueldner PH ，Marini AX ，Li B ，Darvish CJ ，Chung TK ，Weinbaum JS ，Curci JA ，Vorp DA ... -  《-》

A novel rat model of abdominal aortic aneurysm using a combination of intraluminal elastase infusion and extraluminal calcium chloride exposure.

Tanaka A ，Hasegawa T ，Chen Z ，Okita Y ，Okada K ... -  《-》

A Mouse Abdominal Aortic Aneurysm Model by Periadventitial Calcium Chloride and Elastase Infiltration.

Ge J ，Weng C ，Zhang X ，Zhao J ，Zhang H ，Yuan D ，Wang T ... -  《-》