Original article
General thoracic
Tracheal Replacement With a Silicone-Stented, Fresh Aortic Allograft in Sheep

https://doi.org/10.1016/j.athoracsur.2009.09.005Get rights and content

Background

Tracheal tissue regeneration after allogeneic aortic transplants in sheep has been reported. We sought to confirm these findings and elucidate the mechanism of this transformation.

Methods

Ten male sheep underwent cervical tracheal replacement with fresh, descending thoracic aortic allografts, 8 cm long, from female sheep, without postoperative immunosuppressive therapy. A 10-cm silicone stent was placed to prevent airway collapse. Graft evaluations with flexible bronchoscopy and computed tomography were conducted between 2 weeks and 1 year after surgery.

Results

There were no procedural deaths, but 6 animals died or required euthanasia between 12 days and 3 months postoperatively owing to severe tracheitis, cervical lymphadenitis, pneumonia, graft necrosis, stent migration, or airway obstruction after stent removal. The 4 remaining sheep were euthanized as planned at 6 to 12 months after surgery. Harvested tracheas revealed no evidence of graft incorporation into the surrounding tissue, and there was no histologic evidence of any neocartilage within or around the graft at any point. Bronchoscopy revealed marked graft necrosis in the 4 animals surviving to planned euthanasia. In all sheep, computed tomography imaging revealed that the graft was replaced by connective tissue without any signs of cartilage regeneration. Image analysis also indicated profound shortening of the grafted area up to 87.5% at 1 year after implantation, secondary to axial shift of the native trachea.

Conclusions

Fresh aortic allografts appear to be unsuitable for primary tracheal replacement. However, the observed graft shortening may allow for two-staged, end-to-end reconstruction of large tracheal defects with temporary grafting techniques.

Section snippets

Material and Methods

The study was approved by the Beth Israel Deaconess Medical Center's Institutional Animal Care and Use Committee. All animals were cared for by a veterinarian in accordance with US Department of Agriculture regulations and the Guidelines for the Care and Use Committee of Laboratory Animals of Beth Israel Deaconess Medical Center and the National Research Council's Guide for the Care and Use of Laboratory Animals, prepared by the Institute of Laboratory Animals and published by the National

Morbidity and Mortality

A summary of the results is given in Table 1. All sheep tolerated the surgical procedure well and there was no perioperative mortality. However, 6 of 10 sheep (60%) had complications. Sheep 1 had severe tracheitis, which did not respond to medication. As a result, sheep 1 was euthanized on postoperative day 12. In sheep 3, the CT scan performed at 3 months revealed that the silicone stent had migrated to the proximal trachea (Fig 1A). The migrated stent was removed with a rigid bronchoscope,

Comment

Several approaches to tracheal reconstruction using a graft interposition have been reported with limited success [2]. Tracheal regeneration after fresh aortic allograft without immunosuppressive therapy has been reported by two groups [4, 7]. These reports seemed to be breakthroughs in this field. We therefore sought to replicate the results and to begin to understand the sequence of events resulting in tracheal regeneration from the aortic construct. If successful, we had subsequent plans to

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