Endothelial Denudation of Isolated Human Internal Mammary Artery Segments

Victor Lamin, Michael Worthington, James Edwards, Fabiano Viana, Robert Stuklis, David Wilson and John Beltrame

Background: Endothelial denudation is an important approach to evaluate the role of the endothelium in vascular reactivity studies. Although approaches to remove the endothelium are well established in animal models, these methods have proved difficult to effectively translate to remnants of human Internal Mammary Artery (IMA) obtained during coronary bypass. This study sought to identify the optimal technique for endothelial denudation of IMA while preserving vascular contractile responses. Methods: IMA segments were subject to endothelial denudation using one of the following techniques: (1) surface abrasion, rubbing with stainless steel wire, (2) vasoconstriction abrasion or (3) shear abrasion via infusion of an effervescent solution. Following intervention, IMA segments were evaluated by: (1) histochemistry to quantify structural damage and endothelial cell abundance and (2) functional endothelium-dependent vasodilator response using vascular myography in an organ bath preparation. Results: Vasoconstriction abrasion removed endothelial cells and caused disruption of the internal elastic lamina, these vessels failed to respond to the vasoconstrictor Phenylephrine (PE) or the endothelium-dependent vasodilator A23187. Surface abrasion alone was incomplete in removing endothelial cells, vessel vasodilated partially when challenged with A23187 in the presence of PE. Shear abrasion removed endothelial cells most effectively, as these pre-constricted vessels did not relax to A23187 but demonstrated increased sensitivity to PE. Conclusions: In this controlled comparative study assessing both structural and functional endpoints of endothelial denudation techniques, we have demonstrated that shear abrasion by infusion of an effervescent solution is the optimal technique to remove the endothelium and preserve vascular function in human IMA.