Physiological cyclic stretching potentiates the cell-cell junctions in vascular endothelial layer formed on aligned fiber substrate

In vascular tissue engineering, formation of stable endothelial cell-cell and cell-substrate adhesions is essential for maintaining long-term patency of the tissue -engineered vascular grafts (TEVGs). In this study, sheet -like aligned fibrous substrates of poly(L-lactide-co-caprolactone) (PLCL) were prepared by electrospinning to provide basement membrane -resembling structural support to endothelial cells (ECs). Cyclic stretching at physiological and pathological levels was then applied to human umbilical vein endothelial cells (HUVECs) cultured on chosen fibrous substrate using a force -loading device, from which effects of the cyclic stretching on cell-cell and cell-substrate adhesions were examined. It was found that applying uniaxial 1 Hz cyclic stretch at physiological levels (5 % and 10 % elongation) strengthened the cell-cell junctions, thus leading to improved structural integrity, functional expression and resistance to thrombin -induced damaging impacts in the formed endothelial layer. The cell-cell junctions were disrupted at pathological level (15 % elongation) cyclic stretching, which however facilitated the formation of focal adhesions (FAs) at cell-substrate interface. Mechanistically, the effects of cyclic stretching on endothelial cell-cell and cell-substrate adhesions were identified to be correlated with the RhoA/ROCK signaling pathway. Results from this study highlight the relevance between applying dynamic mechanical stimulation and maintaining the structural integrity of the formed endothelial layer, and implicate a necessity to implement appropriate dynamic mechanical training (i.e., preconditioning) to obtain tissueengineered blood vessels with long-term patency post -implantation.