Controlled disturbed flows on the endothelium result in increased inflammation, nuclear lamin disruption and heterochromatin condensation

Abstract

Early atherosclerotic lesions often develop in areas of disturbed flow within arterial curvatures and bifurcations. Complex flows alter the signaling of inflammatory and other signaling molecules that may exacerbate the disease phenotype. Microfluidic platforms to assess changes in endothelial mechanobiology generally employ laminar unidirectional or oscillatory flows generated in straight channels; such platforms do not however mimic the complex time-varying bi-directional shear patterns on arterial walls. We fabricated an endothelium-on-chip device to generate "controlled" disturbed flows, characterized using a wall shear rosette, such as those reported in aneurysmal vessels and in regions with atherosclerotic plaques. We cultured human aortic endothelial cells (HAEC) in the device and subjected the monolayer to a circular shear rosette which represents bidirectional and oscillatory shear stresses. Immunofluorescence results show large cuboidal cells with significantly higher nuclear areas, changes in the localization of VE-Cadherin, elevated actin and NF-kB expressions in the device as compared to cell monolayers subjected to laminar flow, unidirectional oscillatory flow, and No-flow conditions. The creation of a dysfunctional endothelial monolayer due to bidirectional oscillatory flows also correlated with dramatic changes to the lamin A/C distribution and heterochromatin organization in the nucleus that have not been reported earlier. Such studies are potentially useful to assess novel therapeutics, mitigate effects of vascular disease for personalized medicine, study thrombus creation in the vicinity of inflamed endothelial monolayers, and reduce ourreliance on animal trials. Our device and analytical method represent the first successful demonstration of generating controlled disturbed flows in microfluidic devices