Histological Comparison of Papain-induced and Elastase-induced Saccular Aneurysms in Rabbits

Abstract

A saccular aneurysm is a localized, pouch arterial abnormality, Varous kinds of experimental saccular aneurysm models have been developed to treat aneurysms, and more effective ways to create aneurysm model is also needed. This study aims to compare aneurysm models induced by either porcine pancreatic elastase or papain from papaya latex. Eleven New Zealand white rabbits were divided into three treatment groups: normal saline (n=3), papain (n=4), and elastase (n=4). The right common carotid artery was selected as the aneurysmal site, and the respective substance was incubated for 20 minutes. No neurological signs occurred after operation. Hematoxylin-eosin (H&E) staining and modified elastic trichrome stain were performed 2 weeks after the procedure for pathological analysis. Histological findings for the control group showed normal vascular wall structure, normal elastic fiber, and no signs of inflammation. In samples of the papain group, the vascular walls were damaged and the endothelium was detached. Most of the elastic fibers were destructed. All samples of the papain group showed elastic fragmentation. In the elastase group, all samples showed severe inflammation and destruction of the vascular structure. There was also an elastase-induced sterile abscess. These findings indicate that elastase does not induce stable aneurysms at a dose of 1 mg because of excessive inflammation and destruction of the vascular structure.Elastase induces inflammation and apoptosis which results in the vascular wall to weaken before an aneurysm is formed. Papain at the dose of 1 mg, in contrast, seems to be a suitable candidate for enzymatic aneurysm models in the rabbit.