Published Online:https://doi.org/10.1148/radiol.13130796

Endothelialization of the aneurysm neck proceeds from the parent artery and depends on an underlying smooth muscle cell substrate.

Purpose

To characterize the progression of healing across aneurysm necks following treatment with a flow diverter in a rabbit aneurysm model.

Materials and Methods

With institutional animal care and use committee approval, saccular aneurysms were created in 20 rabbits and treated with flow diverters. On days 1, 3, and 7 and weeks 4 and 8 after implantation, the aneurysm and the device-implanted vessel were harvested. En face staining of the gross specimen was performed for endothelial cells, endothelial progenitor cells, smooth muscle cells, and inflammatory cells.

Results

The parent artery segments covered by the flow diverters were completely devoid of endothelial cells at 1 and 3 days but had completely reendothelialized by 7 days. At all time points, the struts along the patent portions of the aneurysm necks harbored scattered tissue islands composed exclusively of inflammatory cells. At 4 and 8 weeks, all samples contiguous with the tissue along the parent arteries had translucent tissue present along the occluded segments of the aneurysm neck. The vast majority of endothelial cells were contiguous with the parent artery and had smooth muscle cells underlying them. Endothelial progenitor cells were not observed along the neck of any aneurysm. Aneurysm closure was noted only when complete or nearly complete endothelialization over the device struts was present.

Conclusion

The initial event following flow diversion treatment is adherence of clusters of inflammatory cells across the aneurysm neck. Endothelialization is relatively delayed and derived exclusively from cells in the adjacent parent artery.

© RSNA, 2013

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Article History

Received April 3, 2013; revision requested May 13; revision received June 11; accepted July 15; final version accepted July 19.
Published online: Feb 2014
Published in print: Feb 2014