A numerical analysis of forces exerted by laminar flow on spreading cells in a parallel plate flow chamber assay

Abstract

Exposure of spreading anchorage-dependent cells to laminar flow is a common technique to measure the strength of cell adhesion. Since cells protrude into the flow stream, the force exerted by the fluid on the cells is a function of cell shape. To assess the relationship between cell shape and the hydrodynamic force on adherent cells, we obtained numerical solutions of the velocity and stress fields around bovine aortic endothelial cells during various stages of spreading and calculated the force required to detach the cells. Morphometric parameters were obtained from light and scanning electron microscopy measurements. Cells were assumed to have a constant volume, but the surface area increased during spreading until the membrane was stretched taut. Two-dimensional models of steady flow were generated using the software packages ANSYS (mesh generation) and FIDAP (problem solution). The validity of the numerical results was tested by comparison with published results for a semicircle in contact with the surface. The drag force and torque were greatest for round cells making initial contact with the surface. During spreading, the drag force and torque declined by factors of 2 and 20, respectively. The calculated forces and moments were used in adhesion models to predict the wall shear stress at which the cells detached. Based upon published values for the bond force and receptor number, round cells should detach at shear stresses between 2.5 and 6 dyn/cm(2), whereas substantially higher stresses are needed to detach spreading and fully spread cells. Results from the simulations indicate that (1) the drag force varies little with cell shape whereas the torque is very sensitive to cell shape, and (2) the increase in the strength of adhesion during spreading is due to increased contact area and receptor densities within the contact area.

Label-free, microfluidic separation and enrichment of human breast cancer cells by adhesion difference

“…Additionally, F H should be modified as a function of the ratio of cell to channel height (c) in a microchannel geometry 35 and needs to be implemented with shape evolution during cell spreading. 36 For the cell shape elongated on the 400 nm line pattern as shown in Fig. 4(b), (f) with small c (,0.25), F H is given by the following form after algebraic manipulation:…”

Cellular and Subcellular Analysis on Chip

“…It was possible to remove fully spread fibroblasts at the end of the assay by applying ~6000 dynes/cm 2 , using a flow rate that is well within the technical limit of the system. This threshold of detachment force is comparable to macro scale experiments [10], and it is in agreement with theoretical calculations [11].…”

Impedance analysis of endothelial cells undergoing orbital shear stress.

“…Parallel plate flow chambers (PPFCs) are the CCF system traditionally used for carrying out adhesion assays (Olivier and Truskey, 1993). The use of a PPFC to perform an adhesion assay involves loading cells into the device, allowing them to adhere, and then incrementally increasing shear stress to ramp the force dissociating cells from the substrate (Young and Simmons, 2010).…”