Korean J Radiol.  2014 Oct;15(5):622-629. 10.3348/kjr.2014.15.5.622.

Tissue Responses to Stent Grafts with Endo-Exo-Skeleton for Saccular Abdominal Aortic Aneurysms in a Canine Model

• Kim YI
• Choi YH
• Chung JW
• Kim HC
• So YH
• Kim HB
• Min SK
• Park JH

• KMID: 1734947
• DOI: http://doi.org/10.3348/kjr.2014.15.5.622

Abstract

OBJECTIVE
We evaluated the effect of close contact between the stent and the graft on the induction of endothelial covering on the stent graft placed over an aneurysm.
MATERIALS AND METHODS
Saccular abdominal aortic aneurysms were made with Dacron patch in eight dogs. The stent graft consisted of an inner stent, a expanded polytetrafluoroethylene graft, and an outer stent. After sacrificing the animals, the aortas with an embedded stent graft were excised. The aortas were inspected grossly and evaluated microscopically.
RESULTS
The animals were sacrificed at two (n = 3), six (n = 3), and eight months (n = 2) after endovascular repair. In two dogs, the aortic lumen was occluded at two months after the placement. On gross inspection of specimens from the other six dogs with a patent aortic lumen, stent grafts placed over the normal aortic wall were covered by glossy white neointima, whereas, stent grafts placed over the aneurysmal aortic wall were covered by brownish neointima. On microscopic inspection, stent grafts placed over the normal aortic wall were covered by thin neointima (0.27 +/- 0.05 mm, mean +/- standard deviation) with an endothelial layer, and stent grafts placed over the aneurysmal aortic wall were covered by thick neointima (0.62 +/- 0.17 mm) without any endothelial lining. Transgraft cell migration at the normal aortic wall was more active than that at the aneurysmal aortic wall.
CONCLUSION
Close contact between the stent and the graft, which was achieved with stent grafts with endo-exo-skeleton, could not enhance endothelial covering on the stent graft placed over the aneurysms.

Keyword

Aorta; Aortic aneurysm; Stent-graft; Neointima; Endothelium

MeSH Terms

Animals
Aortic Aneurysm, Abdominal/pathology/*therapy
Blood Vessel Prosthesis Implantation
Disease Models, Animal
Dogs
Endothelium, Vascular/cytology/pathology
*Stents
Tomography, X-Ray Computed

Figure

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  Fig. 1 Stent graft with endo-exo-skeleton consisting of inner bare stent, middle graft, and outer bare stent.

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  Fig. 2 Angiography before and after stent graft placement. A. Conventional angiography shows aortic saccular aneurysm to left of aorta. B. On completion angiography after stent graft placement, middle part of inserted stent graft shows outward convexity towards saccular aneurysm. C. CT angiography at two months demonstrates complete exclusion of aneurysm, no endoleak, and patent lumen.

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  Fig. 3 Gross inspection findings and transgraft cell migration. A. Gross inspection after longitudinal incision of abdominal aorta at opposite side of aneurysm demonstrates thick brown neointima (arrow) over aneurysmal aortic wall, which protrudes towards aortic lumen. Glossy white neointima (arrowhead) is noted over normal aortic wall. B. Microscopic examination (Masson's trichrome stain, original magnification × 1) shows thin neointima over normal aortic wall (thin-lined rectangular block) and thick neointima over aneurysmal aortic wall (thick-lined rectangular block). C, D. Magnified view of thin-lined rectangular block in B located in normal aortic wall (original magnification, × 40 and × 400) shows graft with lot of collagen (bright blue) and more than ten spindle cells (violet) rated as Grade 3. Brown band between footprints of inner and outer stent wire struts in C and E is graft. E, F. Magnified view of thick-lined rectangular block in B located in stent graft placed over excluded saccular aneurysm (original magnification, × 40 and × 400) shows graft with little collagen and few spindle cells rated as Grade 1.

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  Fig. 4 Immunohistochemical staining of endothelial covering. A. Cross-section of bisected aorta contains stent graft and aneurysm (Factor VIII-related antigen immunohistochemical staining, original magnification × 1). Thin-lined rectangular block is normal aortic wall and thick-lined rectangular block is aneurysmal aortic wall. B, C. Magnified view of thin-lined rectangular block in A located in normal aorta (B; Factor VIII-related antigen immunohistochemical staining, C; Hematoxylin-Eosin staining, original magnification, × 400) shows layer of cells strongly reactive to Factor VIII-related antigen immunohistochemical staining, which indicates endothelial covering on neointima. D, E. Magnified views of thick-lined rectangular block in A located in stent graft placed over excluded saccular aneurysm (D; Factor VIII-related antigen immunohistochemical staining, E; Hematoxylin-Eosin staining, original magnification, × 400) show layer of cells in neointima that are not stained on Factor VIII-related antigen immunohistochemical staining.

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