Implantation of a Carotid Cuff for Triggering Shear-stress Induced Atherosclerosis in Mice

Summary

The constricting cuff presented in this article is designed to induce atherosclerosis in the murine common carotid artery. Due to the conical shape of its inner lumen the implanted cuff generates well-defined regions of low, high and oscillatory shear stress triggering the development of atherosclerotic lesions of different inflammatory phenotypes.

Abstract

It is widely accepted that alterations in vascular shear stress trigger the expression of inflammatory genes in endothelial cells and thereby induce atherosclerosis (reviewed in ¹ and ²). The role of shear stress has been extensively studied in vitro investigating the influence of flow dynamics on cultured endothelial cells ^1,3,4 and in vivo in larger animals and humans ^1,5,6,7,8. However, highly reproducible small animal models allowing systematic investigation of the influence of shear stress on plaque development are rare. Recently, Nam et al. ⁹ introduced a mouse model in which the ligation of branches of the carotid artery creates a region of low and oscillatory flow. Although this model causes endothelial dysfunction and rapid formation of atherosclerotic lesions in hyperlipidemic mice, it cannot be excluded that the observed inflammatory response is, at least in part, a consequence of endothelial and/or vessel damage due to ligation.

In order to avoid such limitations, a shear stress modifying cuff has been developed based upon calculated fluid dynamics, whose cone shaped inner lumen was selected to create defined regions of low, high and oscillatory shear stress within the common carotid artery ¹⁰. By applying this model in Apolipoprotein E (ApoE) knockout mice fed a high cholesterol western type diet, vascular lesions develop upstream and downstream from the cuff. Their phenotype is correlated with the regional flow dynamics ¹¹ as confirmed by in vivo Magnetic Resonance Imaging (MRI) ¹²: Low and laminar shear stress upstream of the cuff causes the formation of extensive plaques of a more vulnerable phenotype, whereas oscillatory shear stress downstream of the cuff induces stable atherosclerotic lesions ¹¹. In those regions of high shear stress and high laminar flow within the cuff, typically no atherosclerotic plaques are observed.

In conclusion, the shear stress-modifying cuff procedure is a reliable surgical approach to produce phenotypically different atherosclerotic lesions in ApoE-deficient mice.

Protocol

1. Preparing the shear stress modifier (cuff)

1. The shear stress modifier consists of two longitudinal halves of a cylinder with a cone shaped lumen. The half shells are made of thermoplastic polyetherketone produced by a plastic casting procedure. The cast elements are sent out while still connected to the runner. Hence, the half shells have to be cut off before usage. Each cast contains half shells of different sizes ranging from 150 μm - 300 μm (lowest inner diameter at downstream end).
2. The cuff preparation should be performed under a surgical microscope.
3. Hold the cuff half shell with blunt forceps and gently cut i....

Discussion

In order to minimize experimental variation it is recommended to work with animals of nearly the same age and with the same diet history. A recently published investigation demonstrates that the shear stress modifier applied in wildtype mice might be a good model for the investigation of endothelial dysfunction and early inflammatory responses induced by altered flow dynamics ¹³. However, for the enquiry of atherosclerotic plaque development transgenic hyperlipidemic mouse models (e.g. the ApoE knockout mouse).......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Shear stress modifier (polyetherketone)	Promolding BV