Uniaxial cyclic stretch regulates the expression of thrombomodulin and von Willebrand factor on endothelial cells.

Deep vein thrombosis (DVT) is the formation of a thrombus in the valvular sinuses of the veins in the lower limbs. It is often associated with blood stasis during prolonged immobilization, however, the triggers for DVT are not well understood. Venous valvular sinuses experience unique blood flow patterns due to the cyclic opening and closing of the valve. We hypothesize that stretching helps maintain vein antithrombotic properties, and its absence could contribute to the onset of DVT. To test this idea, confluent human endothelial cells are cultured on hydrogel-coated elastic membranes subjected to uniaxial cyclic stretching at rates of 60 cycles per minute. We study how different levels and duration of stretching influence the expression of 2 important proteins of the hemostatic system, thrombomodulin (TM) and von Willebrand factor (VWF). Our results show that the cells elongate and align orthogonal to the stretch direction. Stretch amplitude of 10% increases TM levels by 75% within 6 hours and remains high up to 24 hours. Interestingly, no significant change occurred at the 5% stretch even after 24 hours. When 10% stretching is interrupted after 24 hours, VWF levels measured 6 hours after interruption increase significantly. Additionally, we show that stretching flattens the nuclei and aligns them orthogonal to the stretching direction. Notably, the epigenetic acetylation mark histone H3 lysine 27 acetylation, which regulates TM gene expression, increases by 1.6-fold. Taken together, our findings suggest that cyclic stretch contributes to the regulation of endothelium thromboresistance and might prevent thrombosis.