The effect of shear stress on human endothelial cells seeded on cylindrical viscoelastic conduits: an investigation of gene expression

The present study assesses the effect of physiological shear stress on gene expression from human ECs (endothelial cells) seeded on a small-diameter cylindrical bypass graft constructed from nanocomposite based on poly(carbonate-silsesquioxane-bridge-urea)urethane. ECs were seeded on to 5-mm-diameter conduits, placed in a physiological flow circuit and exposed to 1 or 4 h of shear stress at 1.4 +/- 0.3 Pa. Subsets of conduits were incubated at 37 degrees C and 5% CO2/95% O-2 for a further 4 h to determine if gene expression returned to basal levels. PCR was conducted for glyceraldehyde-3-phosphate dehydrogenase, TGF beta-I (transforming growth factor beta-I), COL-I (collagen-I) and PECAM-I (platelet/EC adhesion molecule-I). Increases in gene expression were seen following flow in nanocomposite conduits. These were significant at 4 h for TGF beta-I, COL-I and PECAM-I. After a 4 h recovery period, there were no significant differences in gene intensity, suggesting that this change is transient. These data prove that mRNA can be obtained from ECs seeded on tubular conduits and exposed to shear stress and that gene-expression studies can be successfully carried out. We believe this is a substantial improvement on studies based on flat sheets.