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    Oral Communication

    Vascular Biology

    Mechanisms Regulating Vessel Wall Function and Integrity

    OC 10.2 - Mechanical stress induces an anti-fibrinolytic and pro-thrombotic state in macrophages and smooth muscle cells in atherosclerotic lesions

    Saturday, June 24, 2023
    13:15 – 13:30 ET
    Room: 515
    Session Available As: On-Demand
    Background: Arterial vessel narrowing due to plaque development and calcification causes higher mechanical shear forces in atherosclerotic plaques. Mechanically stressed cells express Yes-associated-protein-1 (YAP), which is a transcriptional co-activator and promotes cell proliferation and suppresses apoptosis.

    Aims: In this project we want to investigate the effect of mechanical stress on macrophages and smooth-muscle-cells (SMCs) on their effector function during atherosclerosis.

    Methods: LDLR-/- mice were fed with high fat diet for 16 weeks and hearts were extracted to analyse plaque development in the aortic roots. We used immunohistochemistry to analyse mouse and human plaques regarding their YAP expression and localisation of cells within the plaque. To mimic mechanical force in atherosclerotic plaques in vitro, we used the flexcell device to stretch cells. Protein and RNA expression were analysed by ELISA, qPCR and extracellular vesicles by flow cytometry.

    Results: Our data revealed that macrophages and SMCs in human and mouse atherosclerotic plaques are exposed to mechanical stress, indicated by YAP expression. Determining YAP localisation showed that mechanically stressed macrophages are located in the SMC layer and in the core of the plaque. Macrophages in the core had a higher YAP expression compared to the average arterial endothelial cell indicating that there are higher mechanical forces within the lesion as compared to areas with blood flow. In vitro, mechanical stress led to decreased uPA expression and an increase in PAI levels, leading to an anti-fibrinolytic state. Further analysis of extracellular vesicles released by mechanically stressed macrophages showed a significant higher amount of tissue factor in lipopolysaccharid and interferon-γ-polarized M1 macrophages compared to other subsets and untreated macrophages, highlighting a pro-thrombotic state. Additionally, SMCs and macrophages showed an increase in IL-6 and uPAR mRNA expression, signs of mechanically induced inflammation.

    Conclusion(s): Mechanical stress on macrophages and SMCs induces an anti-fibrinolytic, pro-thrombotic and inflammatory phenotype.

    Learning Objectives:

    • Mechanically stressed macrophages in atherosclerosis are not necessarily located by the endothelial cell layer. They also occure in the plaque core.
    • Mechanical stress (in vivo and in viro) induces phenotype changes in macrophages.
    • Mechanical stress leads to a pro inflammatory state in macrophages