Bistability of Dielectrically Anisotropic Nematic Crystals and the Adaptation of Endothelial Collectives to Stress Fields

Abstract

Endothelial monolayers physiologically adapt to flow and flow-induced wall shear stress, attaining ordered configurations in which elongation, orientation, and polarization are coherently organized over many cells. Here, with the flow direction unchanged, a peculiar bi-stable (along the flow direction or perpendicular to it) cell alignment is observed, emerging as a function of the flow intensity alone, while cell polarization is purely instructed by flow directionality. Driven by the experimental findings, the parallelism between endothelia is delineated under a flow field and the transition of dual-frequency nematic liquid crystals under an external oscillatory electric field. The resulting physical model reproduces the two stable configurations and the energy landscape of the corresponding system transitions. In addition, it reveals the existence of a disordered, metastable state emerging upon system perturbation. This intermediate state, experimentally demonstrated in endothelial monolayers, is shown to expose the cellular system to a weakening of cell-to-cell junctions to the detriment of the monolayer integrity. The flow-adaptation of monolayers composed of healthy and senescent endothelia is successfully predicted by the model with adjustable nematic parameters. These results may help to understand the maladaptive response of in vivo endothelial tissues to disturbed hemodynamics and the progressive functional decay of senescent endothelia.

4D Force Detection of Cell Adhesion and Contractility

“…55 In all these examples, the transmission of forces across the cell, from the free surface to the one in contact with the substrate, is an integral part of the adaptive response. 56,57 Atomic and traction force microscopy allow the manipulation and measurement of biological forces acting on and around adhering cells. 18,25,32,58,59 The technological advancements leading to state-of-the-art FluidFM and cTFM−Cellogram protocols introduced sufficient measurement capacity to overcome intrinsic intercellular variability with population analysis.…”

“…Similarly, apical shear paces interstitial cell advancement in a porous environment,54 and hydrostatic load controls the response of the inner linings in epithelial tissues 55. In all these examples, the transmission of forces across the cell, from the free surface to the one in contact with the substrate, is an integral part of the adaptive response 56,57. Atomic and traction force microscopy allow the manipulation and measurement of biological forces acting on and around adhering cells 18,25,32,58,59.…”