Laboratory InvestigationsComparison of the Endothelialization of Small Intestinal Submucosa, Dacron, and Expanded Polytetrafluoroethylene Suspended in the Thoracoabdominal Aorta in Sheep
Section snippets
Animals
The study involved 12 adult female sheep weighing 49.7–70.6 kg (mean, 58.2 kg). All together, 36 devices were implanted in their thoracic aortas. The study was approved by the institutional animal care and use committee of the Oregon Health and Science University.
Devices
The devices used in the study were handmade in our research laboratory. They consisted of two parts, a small carrier for the membrane and a large square stent frame for its suspension (Fig 1) as previously described by Brountzos et al (
RESULTS
Thoracoabdominal aorta diameters ranged from 17.5 mm to 20.0 mm (mean, 19.01 mm). Thirty-five devices were successfully placed, and they self-centered in the longitudinal axis of the thoracoabdominal aorta. In one animal, the ePTFE device placed as the most proximal of the three devices tilted 90° and was positioned perpendicularly with no adverse sequelae. In all cases, including the tilted device, the suspended membranes were not in contact with the wall of the thoracoabdominal aorta.
SIS
Thickness of the SIS leaflets (Table 2) measured in their midportions ranged from 240 μmto520 μm (mean ± SD, 367.5 ± 120.8 μm) at 8 weeks and from 210 μmto490 μm (mean, 320 ± 121.9 μm) at 18 weeks. The SIS membrane material was still visible in the centers of the leaflets. At 8 weeks, it showed early remodeling, with host fibroblasts, neutrophils, plasma cells, and few macrophages interspersed among collagen fibers. At 18 weeks, SIS membranes exhibited advanced remodeling, with collagen fibers
ePTFE
Thickness of the ePTFE leaflets (Table 4) at their midportions ranged from 200 μmto360 μm (mean, 272 ± 67.6 μm) at 8 weeks and from 190 μm to 430 μm (mean, 268.3 ± 85.2 μm) at 18 weeks. Two leaflets were bare without any neointimal coating, and two were bare on their external surface. Neointima consisting of spindleshaped host cells and white blood cells covered the other membranes. On the internal surface, thickness of the neointima ranged from 10 μm to 130 μm (mean, 78.3 ± 66.4 μm) at 8 weeks
DISCUSSION
Recurring problems with endografts for endovascular aneurysm repair indicate that endograft design and coverings are both important (1, 2, 3, 4, 5, 6). Endografts should be flexible but strong enough to avoid kinking, perforation, or rupture. They also should become incorporated into the aortic wall to prevent migration and endoleaks. Endograft endothelialization could be beneficial and might decrease thrombus formation and occasional endograft occlusion that occurs mainly at its branch
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Evaluation of a hybrid small caliber vascular graft in a rabbit model
2020, Journal of Thoracic and Cardiovascular SurgeryThe effects of stent interaction on porcine urinary bladder matrix employed as stent-graft materials
2014, Journal of BiomechanicsCitation Excerpt :Small intestinal submucosa (SIS) and urinary bladder matrix (UBM) are 2 porcine derived ECMs that have demonstrated potential for tissue regeneration in stented environments (Hoppo et al., 2012; Ishii et al., 2005; Nakata et al., 2003; Niyyati et al., 2005; Schoder et al., 2004; Yamada et al., 2001; Yavuz et al., 2006). Studies investigating SIS ‘stent-grafts’ have demonstrated incorporation of the stent-graft into aortic tissue after deployment (Noishiki et al., 2001; Schoder et al., 2004; Yamada et al., 2001; Yavuz et al., 2006). Over time the ECM was replaced by a dense neointima with partial re-endothelisation of the aortic wall.
Animal models for the assessment of novel vascular conduits
2010, Journal of Vascular SurgeryComparison of Tissue Reaction with Three Different Endografts Used for Exclusion of Carotid Artery Aneurysm in a Dog Model
2009, Journal of Vascular and Interventional RadiologyCitation Excerpt :The most commonly used stent-covering materials include PTFE, polyester, polyurethane, Dacron, and biomembranes. Although Dacron was frequently used in early studies, it lacks elasticity and causes an acute inflammatory reaction that leads to stent blockage. (6) Thus, Dacron can be used only when the diameter of blood vessel is more than 6 mm, and is currently used only rarely.
Polytetrafluoroethylene-covered stents in the venous and arterial system: angiographic and pathologic findings in a swine model
2008, Cardiovascular PathologyCitation Excerpt :These factors make it an attractive choice as a covering material for devices deployed in the vasculature. Recent studies have demonstrated that PTFE grafts generated the smallest degree of neointimal formation and a significant decrease in the degree of vessel stenosis when compared to SIS- and Dacron-covered stent-grafts in both the venous and arterial systems [16,17]. Our work with PTFE-covered stents confirms prior work that these devices generate a small degree of neointimal formation and no evidence of stenosis in the arterial system [22].
Animal Model for Percutaneous Creation of Traumatic Thoracic Aortic Transection
2008, Journal of Vascular and Interventional RadiologyCitation Excerpt :Future research with this model will be directed toward studying acute and chronic healing of transections treated with current endografts. The impact on acute and chronic healing by external coatings on an endograft, such as small intestinal submucosa, could be studied (12,13). Other potential treatment options would be absorbable endografts or removable endografts.
This study was supported by a grant from Cook, Inc., Bloomington, IN. J.H. is an employee of Cook Biotech. None of the authors have identified a conflict of interest