Stiffness of the Aligned Fibers Affects Structural and Functional Integrity of the Oriented Endothelial Cells

Abstract

Promoting healthy endothelialization of the tissue-engineered vascular grafts is of great importance in preventing the occurrence of undesired post-implantation complications including neointimal hyperplasia, late thrombosis, and neoatherosclerosis. Previous researches have demonstrated the crucial role of scaffold topography or stiffness in modulating the behavior of the monolayer endothelial cells (ECs). However, stiffness influence of the substrate/scaffold with anisotropic topography on ECs with in vivo like oriented morphology has rarely been attempted. In this study, aligned fibrous substrates (AFSs) with tunable stiffness (14.68~2141.72 MPa) resembling that of the healthy and diseased subendothelial matrix were used to investigate the effects of aligned fiber stiffness on EC attachment, orientation, proliferation, function, remodeling and dysfunction. The results demonstrate that stiffness of the AFSs capable of providing topographical cues is a crucial endothelium-protective microenvironmental factor by maintaining the long-standing, stable and quiescent endothelium with in vivo like orientation and strong cell-cell junctions. Stiffer AFSs exacerbated disruption of endothelium integrity, occurrence of endothelial-to-mesenchymal transition (EndMT), and inflammation-induced activation in endothelial monolayer. This study provides new insights into the understanding on how the stiffness of biomimicking anisotropic substrate regulates the structural and functional integrity of the in vivo like endothelial monolayer, and offers essential designing parameters in engineering biomimicking small-diameter vascular grafts for the regeneration of viable blood vessels.