Engineering of cardiovascular implant surfaces towards endothelial cell regeneration

Cardiovascular implants play a significant role in the treatment of cardiovascular disease. However, increases the risk of thromboembolic complications and infection. The development of hemocompatible interfaces by generating an autologous endothelial monolayer at the luminal surface of cardiovascular implants may be a promising strategy. Intraluminal surface modification of cardiovascular implants aims to engineer physical properties of biomaterials, such as surface topography and improve endothelial cell performance towards long-term endothelialization. Indeed, many previous studies underlined the hypothesis that anisotropic topographies with gratings enhance the biomechanical properties of endothelial cells from healthy donors. However, typical recipients of cardiovascular implants are in advanced age and often present with chronic cardiovascular disease linked to premature endothelial cell senescence, a phenomenon associated with impaired endothelial cell function. Thus, endothelial cell senescence poses a significant obstacle to successful implant endothelialization. To study the impact of senescence on the biomechanical properties of endothelial cells as well as the impact of anisotropic topographies with gratings on senescence, we expanded in vitro fully characterized human umbilical vein endothelial cells until cell cycle arrest occurred. The biomechanical properties of senescent endothelial cells were then characterized under static and flow conditions after short- or long-term cultivation on flat or gridded surfaces. Senescent HUVECs revealed high levels of γ-H2AX nuclear foci, increased SA-β-gal activity and significantly decreased relative telomere length as evidence of replicative senescence. Senescent endothelial cells were enlarged considerably, revealed irregular inhomogeneous cell outlines, and lost their ability to form high-confluent monolayers. Moreover, senescent endothelial cells showed impaired monolayer connectivity and lost the ability to form well-organized elongated and aligned actin stress fibers in response to laminar flow. Short-term expansion of senescent endothelial cells on the gratings showed significant enhancement of cell-substrate, cell-cell adhesion as well as topographical-oriented cell elongation due to actin filaments remodeling. More interestingly, long-term expansion on the gratings enhanced the replicative capacity of endothelial cells without concomitant early onset of senescence. Our data suggest that micro-structured surfaces with anisotropic topographies may enhance the biomechanical properties of senescent endothelial cells, slow down the phenomenon of senescence and improve long-term endothelialization of cardiovascular implants