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

Abstract

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 tissue-engineered blood vessels with long-term patency post-implantation.