Engineering A Coronary Artery-On-A-Chip Model Of Endothelial Dysfunction

Abstract

Atherosclerosis, lipid deposition into the inner endothelial cell (EC) layer of arteries, underlies heart attacks and stroke. Endothelial dysfunction, characterised by impaired endothelial barrier function, greater lipid infiltration, and increased inflammatory protein expression, enables immune cell adhesion. This preferentially occurs at regions of low wall shear stress (WSS), a frictional force acting on blood vessels, such as bifurcations in the coronary arteries supplying the heart. Accurate disease models are crucial, but standard in vitro models cannot replicate blood flow conditions while in vivo systems are resource-intensive and face increasing ethical barriers. This thesis describes the development of a coronary artery-on-a-chip with human ECs and flow conditions.

The chip reproduced changes in cell morphology and proteins such as ICAM-1 and eNOS with changing local WSS. Importantly, under dysfunctional conditions, endothelial alignment was impaired with ICAM-1 seen closer to the bifurcation. Also, relative to higher WSS regions, immune cell adhesion to ECs at the bifurcation increased 2-fold. Treatment with simvastatin decoupled ICAM-1 expression from WSS, reducing immune cell adhesion to levels seen with healthy ECs.

To develop a co-culture of endothelial and smooth muscle cells, the two key arterial cell types, required modifying the microfluidic surfaces to improve cell growth and culturing cells on a porous membrane to allow cell-cell signalling. PAC and APPJ, plasma treatments, improved cell growth by covalently immobilising biomolecules without chemical reagents. While commercially available membranes contained fused pores up to 3-times larger than the pre-specified pore size, causing cell leakage, a custom-made membrane showed promising results, and future work will optimise cell growth and bonding. The coronary artery-on-a-chip holds immense potential for personalised medicine and drug screening, aiming to save the lives of mice and men.