Rabbit Elastase Aneurysm: Imaging and Histology Correlates for Inflammation and Healing.

Abstract: OBJECTIVE Aneurysmal subarachnoid hemorrhage remains a devastating event with poorly understood pathophysiology. Previous studies have suggested that aneurysm wall inflammation may play a part in the development and potential rupture of aneurysms. The rabbit elastase aneurysm model is a well-established model, which produces aneurysms closely mimicking human cerebral aneurysms in flow dynamics and histopathology. The primary aim of this study was to correlate inflammatory changes after aneurysm formation using sequential vessel wall imaging with histopathological analysis. A secondary aim was to evaluate the potential effect of gender and anti-inflammatory treatment with aspirin on this inflammatory response. METHODS Twenty-seven New Zealand rabbits underwent surgery to create an aneurysm using elastase infusion at the right common carotid artery origin. Vessel wall imaging and histopathological analysis was obtained at different time points after aneurysm creation. The rabbits were also randomized by gender and to treatment groups with or without aspirin. RESULTS Histopathological analysis revealed three distinct phases after aneurysm formation. These phases were an initial inflammatory phase, followed by a regeneration phase, and finally a connective tissue deposition phase. Vessel wall imaging demonstrated two distinct imaging patterns. No appreciable differences were seen in histology or imaging when comparing gender or treatment with aspirin. CONCLUSIONS Inflammatory changes induced by the rabbit elastase aneurysm model can be correlated with histopathological findings and observed on noninvasive vessel wall imaging. This may provide a method to study the inflammatory pathway as it pertains to aneurysmal development and subsequent rupture.