Evaluating the shear resistance of human endothelial cells under physiological conditions for 3D substrate materials

The development of a healthy endothelial layer, crucial for successful graft implantation and compatibility, may be viable under conventional static conditions in a laboratory setting. However, the integrity of this endothelial layer comes into question when exposed to mechanical shear forces experienced in vivo. For a more comprehensive pre-clinical evaluation the seeded materials must be exposed to shear stress conditions which mimic those produced in vivo, allowing the shear-resistance of the endothelial layer to be truly assessed. An in vitro methodology was developed to assess 3D scaffolds in terms of their ability to grow and maintain a healthy endothelial layer under physiological flow conditions. This will enable multidisciplinary communities to predict the in vivo performance of materials, aiding the material selection process. The cone and plate system, utilised for this study, has the capacity to deliver a controlled uniform shear stress distribution across the plate surface as well as allowing small areas of material to be tested. The bioreactor design has been modified to allow for 3D cell-seeded materials to be securely positioned within a glass well for the duration of testing and removed with ease for further analysis. The effect which porous materials, or materials with complex surface topography, have on the uniformity of the shear stress distributed across the material surface was analysed using experimental and computational techniques. Upon extensive investigation, the set-up was deemed feasible for these material types. This type of experimental set-up creates an ideal platform for analysing all cell-seeded materials, porous or non-porous, under physiological like flow conditions to evaluate their clinical potential as a graft material in terms of cellular performance.