Abstract
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
References
- 1. . A new endoluminal, flow-disrupting device for treatment of saccular aneurysms. Stroke 2007;38(8):2346–2352.
- 2. . A second-generation, endoluminal, flow-disrupting device for treatment of saccular aneurysms. AJNR Am J Neuroradiol 2009;30(6):1153–1158.
- 3. . An original flow diversion device for the treatment of intracranial aneurysms: evaluation in the rabbit elastase-induced model. Stroke 2009;40(3):952–958.
- 4. . Efficient pipeline for image-based patient-specific analysis of cerebral aneurysm hemodynamics: technique and sensitivity. IEEE Trans Med Imaging 2005;24(4):457–467.
- 5. . Creation of saccular aneurysms in the rabbit: a model suitable for testing endovascular devices. AJR Am J Roentgenol 2000;174(2):349–354.
- 6. . Aspirin, but not clopidogrel, reduces collateral conductance in a rabbit model of femoral artery occlusion. J Am Coll Cardiol 2005;46(6):994–1001.
- 7. . Effects of combined therapy of clopidogrel and aspirin in preventing thrombus formation on mechanical heart valves in an ex vivo rabbit model. Thromb Res 2002;107(1-2):39–43.
- 8. . Endothelial cell recovery between comparator polymer-based drug-eluting stents. J Am Coll Cardiol 2008;52(5):333–342.
- 9. . Pipeline embolization device (PED) for neurovascular reconstruction: initial experience in the treatment of 101 intracranial aneurysms and dissections. Neuroradiology 2012;54(4):369–382.
- 10. . Pipeline flow-diverter stent for endovascular treatment of intracranial aneurysms: preliminary experience in 20 patients with 27 aneurysms. World Neurosurg 2011;76(1-2):114–119.
- 11. . Flow-diverter stent for the endovascular treatment of intracranial aneurysms: a prospective study in 29 patients with 34 aneurysms. Stroke 2010;41(10):2247–2253.
- 12. . Flow diverters for treatment of intracranial aneurysms: current status and ongoing clinical trials. J Clin Neurosci 2011;18(6):737–740.
- 13. . Utility of VasoCT in the treatment of intracranial aneurysm with flow-diverter stents. J Neurosurg 2012;117(1):45–49.
- 14. . Angiographic assessment of the performance of flow divertors to treat cerebral aneurysms. Conf Proc IEEE Eng Med Biol Soc 2006;1:3210–3213.
- 15. . Correlation of aneurysm occlusion with actual metal coverage at neck after implantation of flow-diverting stent in rabbit models. Neuroradiology 2012;54(6):607–613.
- 16. . Histopathologic findings in human cerebral aneurysms embolized with platinum coils: report of two cases and review of the literature. AJNR Am J Neuroradiol 2002;23(6):970–974.
- 17. . Gross and microscopic histopathological findings in aneurysms of the human brain treated with Guglielmi detachable coils. J Neurosurg 1999;91(2):284–293.
- 18. . Histological evaluation of endothelial reactions after endovascular coil embolization for intracranial aneurysm: clinical and experimental studies and review of the literature. Interv Neuroradiol 2003;9(Suppl 1):69–82.
- 19. . Contribution of mural and bone marrow–derived neointimal cells to thrombus organization and wall remodeling in a microsurgical murine saccular aneurysm model. Neurosurgery 2006;58(5):936–944; discussion 944.
- 20. . Endothelial progenitor cells contribute to neointima formation in rabbit elastase-induced aneurysm after flow diverter treatment. CNS Neurosci Ther 2013;19(5):352–357.
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
