A Canine Model of Proximal Descending Thoracic Aortic Aneurysm Created with an Autologous Pericardial Patch

Recommendations for Design, Execution, and Reporting of Studies on Experimental Thoracic Aortopathy in Preclinical Models

There is a recent dramatic increase in research on thoracic aortic diseases that includes aneurysms, dissections, and rupture. Experimental studies predominantly use mice in which aortopathy is induced by chemical interventions, genetic manipulations, or both. Many parameters should be deliberated in experimental design in concert with multiple considerations when providing dimensional data and characterization of aortic tissues. The purpose of this review is to provide recommendations on guidance in (1) the selection of a mouse model and experimental conditions for the study, (2) parameters for standardizing detection and measurements of aortic diseases, (3) meaningful interpretation of characteristics of diseased aortic tissue, and (4) reporting standards that include rigor and transparency.

A canine model of aortic arch aneurysm created with autologous pericardium

Background

To establish a canine model of aortic arch aneurysm that is suitable for research on new devices and techniques applied to the aortic arch.

Materials and methods

Fifteen mongrel dogs underwent surgery. The autologous pericardial patch was sewn on the aortotomy site in the anterior wall of the aortic arch. The animals were followed up for 3 months postoperatively. Computed tomography angiography was used to visualize and measure the aneurysm model. Hematoxylin and eosin staining was used to observe the histological characteristics of the aneurysm model. Changes in aneurysm diameter over time were analyzed using analysis of variance.

Results

One dog died of hemorrhage during surgery. Fourteen dogs survived the surgical procedure. Two of them died on the first postoperative day because of ruptures at the suturing margin. The diameter of the aneurysm model was twice as large as that of the aortic arch. There was no significant change in the maximum diameter of the aneurysm model during the follow-up period.

Conclusions

We established a controllable and stable aortic arch aneurysm model created with an autologous pericardium patch. The aneurysm model can be used to research endoleaks after thoracic endovascular aortic repair and new endovascular techniques can be applied to the aortic arch.

A reproducible swine model of a surgically created saccular thoracic aortic aneurysm

A reproducible swine thoracic aortic aneurysm (TAA) model is useful for investigating new therapeutic interventions. We report a surgical method for creating a reproducible swine saccular TAA model. We used eight female swine weighing 20-25 kg (LWD; ternary species). All procedures were performed under general anesthesia and involved left thoracotomy. Following aortic cross-clamping, the thoracic aorta was surgically dissected and the media and intima were resected, and the dissection plane was extended by spreading the outer layer for aneurysmal space. Subsequently, only the adventitial layer of the aorta was sutured. At 2 weeks after these procedures, angiography and computed tomography were performed. After follow-up imaging, the model animals were euthanized. Macroscopic, histological, and immunohistological examinations were performed. All model animals survived, and a saccular TAA was confirmed by follow-up imaging in all cases. The mean length of the shorter and the longer aortic diameter after the procedure were 14.01 ± 1.0 mm and 18.35 ± 1.4 mm, respectively (P<0.001). The rate of increase in the aortic diameter was 131.7 ± 13.8%, and the mean length of aneurysmal change at thoracic aorta was 22.4 ± 1.9 mm. Histological examination revealed intimal tears and defects of elastic fibers in the media. Immunostaining revealed MMP-2 and MMP-9 expressions at the aneurysm site. We report our surgical method for creating a swine saccular TAA model. Our model animal may be useful to investigate new therapeutic interventions for aortic disease.

A new porcine model of ascending aortic aneurysm established using a cover-then-cut method

PURPOSE

To establish a reproducible porcine model of ascending aortic aneurysm (AsAA).

METHODS

We created an AsAA in twelve domestic pigs using a cover-then-cut method, stitching a glutaraldehyde tanned bovine pericardial patch onto the anterolateral aortic wall, then cutting off aortic wall tissue within the patch, and closing the incision in the patch.

RESULTS

The AsAA creation was completed successfully in 11 out of the 12 pigs (91.7%). The mean maximal diameter of the ascending aorta increased significantly by 1.77 times, immediately after the operation (p < 0.05). Significantly continuous expansion of the aneurysm was observed during the follow up period, to 48.9 ± 1.80 mm at 3 months and 50.3 ± 2.25 mm at 6 months (p < 0.05).

CONCLUSIONS

This porcine model of AsAA, created using a repeatable cover-then-cut method, represents a reproducible platform for studying and training, which could contribute to the development of new feasible endovascular treatments of AsAAs.

New Large Animal Model for Aortic Aneurysms in the Viscerorenal Segment

BACKGROUND

Aortic aneurysms in the viscerorenal-segment are nowadays treatable by endovascular means. Previously, new endograft techniques were only tested in healthy animals. We aimed to establish a new large animal model for testing complex endovascular stent techniques preclinically.

METHODS

In sheep, four juxtarenal and two type IV thoracoabdominal aortic aneurysms were surgically created via a retroperitoneal approach. Two pieces out of a 10 × 15-cm bovine pericardial patch were sewn with the healthy aorta longitudinally. The viscerorenal segment was clamped, and the aorta was incised longitudinally. Then, the patches were longitudinally sewn together. In the meantime, antegrade flow through the native part of the aorta was already established by tangential clamping. Computed tomography angiography was performed after 4, 8, and 52 wk.

RESULTS

Technical success was 100%. The median surgical procedure time was 3 h, the median blood loss was 210 mL, and the viscerorenal-segment clamping time was 2-4 min. The animals started drinking 1 h after arousal from anesthesia. One animal died after 1 wk because of delayed bleeding and another died after 1 y because of aneurysm rupture by a secondary bacterial infection. Four animals survived. The proximal landing zone diameter and the clock position of the vessel were stable over 52 wk.

CONCLUSIONS

Surgical creation of an aortic aneurysm in the viscerorenal-segment in sheep was successful, without an ischemia/reperfusion injury. This animal model offers a new platform for evaluating innovative endovascular therapy options in vivo.

Pericardial flap to repair a pulmonary laceration in a cat with pyothorax

Case summary

A 2-year-old female neutered domestic shorthair cat was presented for investigation of acute onset tachypnoea and dyspnoea. Pyothorax was diagnosed based on thoracic radiographs and fluid analysis. Medical treatment consisted of bilateral thoracostomy tube placement, antibiotic therapy and thoracic lavage. After 12 days of medical management infection was still present, warranting exploratory thoracotomy. At surgery, encapsulated abscesses were found in the left lung, right cranial and right middle lobes. The right caudal lobe was the only macroscopically non-abscessated lobe, and appeared to have a parenchymal laceration 8 mm long over the dorsolateral surface. Following partial pericardiectomy, mediastinectomy and debridement of abscesses, a pericardial flap was reflected caudolaterally and apposed over the laceration to seal the affected lung lobe. This flap was sutured to a rim of fibrinous adhesion that was partially covering this lobe. After 8 days the cat was discharged with antibiotic therapy for 3 more weeks. Follow-up assessment at 19 and 38 weeks postoperatively confirmed the cat to have good exercise tolerance. Thoracic radiographs at 19 weeks revealed good bilateral aeration of the pulmonary parenchyma without pleural effusion.

Relevance and novel information

Lung lobe laceration can be treated by lung lobectomy or direct suturing of the lung parenchyma. This is the first report using a pericardial flap to repair a lung laceration. Pericardial flap was successfully used to treat this lung laceration where lobectomy was contraindicated. Encouraging results were present at 8 months postoperatively.

A reproducible swine model of proximal descending thoracic aortic aneurysm created with intra-adventitial application of elastase

OBJECTIVE

Animal models are required to explore the mechanisms of and therapy for proximal descending thoracic aortic aneurysm (TAA). This study aimed to establish a reproducible swine model of proximal descending TAA that can further explain the occurrence and progression of proximal descending TAA.

METHODS

Eighteen Chinese Wuzhishan miniature pigs (30.32 ± 1.34 kg) were randomized into the elastase group (n = 12) and the control group (n = 6). The elastase group received intra-adventitial injections of elastase (5 mL, 20 mg/mL), and the control group received injections of physiologic saline solution. A 4-cm descending thoracic aortic segment proximal to the left subclavian artery was isolated. The distance between the left subclavian artery and the injection starting point of the descending thoracic aorta was 0.5 cm. Elastic protease was circumferentially injected intra-adventitially into the isolated segment of the aortic wall in the elastase group by a handmade bent syringe. The length of the elastic protease injection was 2 cm. An average of 12 injection points were distributed in this 2-cm aortic segment. Each injection point used about 0.4 mL of elastic protease. The distance between two injection points was about 1.5 cm. All animals underwent digital subtraction angiography preoperatively and 3 weeks after operation. Three weeks after TAA induction, aortas were harvested for biochemical and histologic measurements.

RESULTS

All animals in the elastase group developed TAAs. No aneurysms were observed in the control group. The distance between the left subclavian artery and the TAA was 8.00 ± 4.19 mm. Preoperative and postoperative aortic diameters of the elastase group were 15.42 ± 0.43 mm and 24.53 ± 1.41 mm, respectively (P < .0001). Preoperative and postoperative aortic diameters of the control group were 15.31 ± 0.33 mm and 15.57 ± 0.40 mm, respectively (P = .5211). The changes of aortic structure and composition included reduction of smooth muscle cells and degradation of elastic fibers. Levels of matrix metalloproteinases 2 and 9 were increased in TAA tissue.

CONCLUSIONS

This study established a reproducible large animal model of proximal descending TAA. This model has the same biochemical characteristics as human aneurysms in the aspects of aortic expansion, aortic middle-level degeneration, and changes in the levels of matrix metalloproteinases and provides a platform for further study.