Saccular aneurysm induction by elastase digestion of the arterial wall: a new animal model

To develop a rabbit aneurysm model that is more realistic in gross appearance and histological features than previous models and to enable the development of a larger animal model.

Ten rabbits received porcine pancreatic elastase, five at the right common carotid artery bifurcation and five others at the right superior thyroid artery origin. One control animal received collagenase and another received papaverine, each at the right superior thyroid artery origin. The agents were topically delivered to the arterial adventitia with a microsyringe after surgical exposure of the targeted arteries. The arteries were monitored for aneurysm growth with a video camera for up to 3 hours and were then removed and processed for histology.

Saccular aneurysms developed in one of five animals after elastase application at the carotid bifurcation and in all five animals receiving elastase at the superior thyroid artery origin. Among the six aneurysms, recurrent minor hemorrhages occurred in four, thrombosis of the aneurysm sac in three, and rupture causing severe bleeding in one. Histological sections revealed thin-walled aneurysms composed only of collagen fibers and some cellular elements. No saccular dilation resulted from papaverine application. Collagenase application resulted in a hemorrhagic-thrombotic lesion in the arterial wall but no aneurysm formation.

Arterial saccular aneurysms were induced in rabbits by topical application of elastase with an easy and efficient method. These aneurysms are histologically similar to natural aneurysms, and their arterial nature renders them more authentic than those of surgical models. This aneurysm model may serve as a foundation for further aneurysm research.