A simple microfluidic device to study cell-scale endothelial mechanotransduction

Abstract

Atherosclerosis is triggered by chronic inflammation of arterial endothelial cells (ECs). Because atherosclerosis develops preferentially in regions where blood flow is disturbed and where ECs have a cuboidal morphology, the interplay between EC shape and mechanotransduction events is of primary interest. In this work we present a simple microfluidic device to study relationships between cell shape and EC response to fluid shear stress. Adhesive micropatterns are used to non-invasively control EC elongation and orientation at both the monolayer and single cell levels. The micropatterned substrate is coupled to a microfluidic chamber that allows precise control of the flow field, high-resolution live-cell imaging during flow experiments, and in situ immunostaining. Using micro particle image velocimetry, we show that cells within the chamber alter the local flow field so that the shear stress on the cell surface is significantly higher than the wall shear stress in regions containing no cells. In response to flow, we observe the formation of lamellipodia in the downstream portion of the EC and cell retraction in the upstream portion. We quantify flow-induced calcium mobilization at the single cell level for cells cultured on unpatterned surfaces or on adhesive lines oriented either parallel or orthogonal to the flow. Finally, we demonstrate flow-induced intracellular calcium waves and show that the direction of propagation of these waves is determined by cell polarization rather than by the flow direction. The combined versatility and simplicity of this microfluidic device renders it very useful for studying relationships between EC shape and mechanosensitivity.

Topography-driven alterations in endothelial cell phenotype and contact guidance

“…Literature shows a large variety of ranges and architectures affecting the EC alignment. ECs have been aligned by using: nanofibrils made of 30-50 nm collagen I fibers [13]; micropatterns mostly made of fibronectin with 2.5 μm-100 μm stripes [14,15,16]; microgrooves with ridges and grooves ranging from 200 nm to 10 μm and depths of 50 nm to 5 μm [17,18,19,20,21]; and fewer topographies with sinusoidal features with 20 μm wavelength and 6.6 μm amplitude [22]. Previously, we have shown that directional gradients can be used for screening the morphological and phenotypical response of osteoblasts [23,24], adipose tissue-derived stromal cells (ASCs) [25], and myoblasts [26].…”

A Review of Functional Analysis of Endothelial Cells in Flow Chambers

“…The flow estimations in the chamber were accompanied mostly by computational fluid dynamics (CFD). On the other hands, LDV to experimentally measure the flow was performed and compared with some calculated values by Avari et al [ 4 ], and microparticle image velocimetry was used by Lafaurie-Janvore et al [ 8 ]. In the pulsatile flow, the actin microfilament and NO production of ECs were compared in wall shear stress (WSS) during exercise in vivo [ 9 ].…”

“…Munn et al investigated cell fluxes under several flow conditions such as steady or saw-tooth patterns [ 12 ]. Lafaureie-Janvore et al showed the polarization of a cell on micron-size lines [ 8 ]. Anzai et al proposed the disturbance effect by the placement of a stent strut on the cell culture in a parallel flow chamber [ 13 ].…”

“…Changes in the components such as adding glucose [ 100 ], vascular endothelial growth factor (VEGF) [ 123 ], tumor necrosis factor (TNF-α) [ 124 , 125 ], adenosine triphosphate (ATP) [ 117 ], or EDTA [ 126 ] in the cell culture medium yield to exert chemical stimuli over the cells. Experiments combined with micropatterning can also be conducted by modifying the surface properties of the substrate like hardness and hydrophilicity by coating with hydrogel or other materials [ 127 , 128 ] or by plasma treatment [ 8 ]. Furthermore, the effects of oxygen tension on ECs can be studied by manipulating the dissolved gas components in the cell culture medium [ 125 , 129 , 130 ].…”

Mathematical modelling of calcium signalling taking into account mechanical effects

“…The model can also be used to model mechanochemical processes in a thin, one-dimensional, monolayer of cells (called 'tissue' from now on), that is assumed to be a continuum. Epithelial cells can spread or thicken when subjected to mechanical forces; through mechanosensing (the process by which cells sense forces and transduce them into biochemical signals), the forces lead to calcium release from internal cell calcium stores [27]. Also, the cells respond to an increase in intracellular free calcium by contracting.…”