A system to reproduce and quantify the biomechanical environment of the cell

Abstract

An in vitro system that permits application of a uniform biomechanical stimulus to a population of cells with great precision has been developed. The device is designed to subject living cells to reproducible and quantifiable biaxial strains from 0 to 10% at rates from quasi-static to 1 s-1 and frequencies from 0 to 5 Hz. Equations for determining the strain in the substrate upon which the cells are grown, based on easily measured parameters, are derived and validated experimentally. The mechanical properties of the substrate are determined, and it is demonstrated that cells can easily be cultured in the apparatus. By use of the system, cloned bovine pulmonary artery endothelial cell clones are subjected to 5% biaxial strains applied at a peak strain rate of 0.5 s-1 and a frequency of 1 Hz for 7 h with cell viability greater than 84% and cell detachment less than 8%. We demonstrate that cells must be attached to the substrate for them to be stretched and that cell strain and substrate strain are not equal. With the use of fluorescently labeled beads as cell surface markers to measure the actual strain produced in the cells as a result of the deformation of the substrate, cell elongation was found to be approximately 60% of the strain in the substrate. This constant appeared to be affected by both in vitro cell age and morphology.

Adaptation of the endothelium to fluid flow: in vitro analyses of gene expression and in vivo implications

“…V ascular M edicine 2004; 9: [35][36][37][38][39][40][41][42][43][44][45] portion of a vessel. 40 Regions proximal to and in the throat of the stenosis experienced time-averaged, uniform normal and high shear, respectively, while immediately distal to the stenosis, complex, non-uniform ow patterns that included ow separation, stagnation points, low laminar ow and eddy currents were observed.…”

Mechanical Analysis of a Pneumatically Actuated Concentric Double-Shell Structure for Cell Stretching

“…The most widely used commercial device (Flexcell: FX-4000, Flexcell International Corp, Hillsborough, NC, USA) utilized pneumatic pressure to stretch the soft substrate so as to apply the tensile strain in cells [12]. Different from FX-4000, another differential pressure flexible-substrate system that was driven by positive pressure was introduced by Winston et al [13]. The mechanical strain in this device was achieved by out-of-plane distension of the substrate membrane.…”

“…For instance, Thompson et al [17] developed a fluid structure interaction model for a commercial device (FX-4000) to quantify the fluid shear stress and biaxial mechanical strain of the substrate. Yoon et al [18] presented a model of circular PolyDiMethylSiloxane (PDMS) microballoons with ultra-large deflection, which was correlated to the device introduced by Winston et al [13]. Zhao et al [19] modeled a microfluidic platform of tunable microlens arrays (with a deformable PDMS cover) to generate mechanical strains on cells.…”

An integrated instrument for rapidly deforming living cells using rapid pressure pulses and simultaneously monitoring applied strain in near real time

“…For instance, the cams used in compression-based models can lose contact with their specimen, 34 and while the incorporation of pressure sensors can rule out that leaks in pressure based systems, and allow applied pressure to be measured, 36 accurate assessment of the rate and magnitude of applied strain is not readily achievable with the systems that are currently available. systems have been designed that measure strain or deflection using depth gauges, a molding resin to replicate the bulging membranes, 37,38 static imaging of pressurized disks 37 or optical tracking of cell strain by induced pressure, 39 these systems do not in general result in real or near real time data. In addition, it is also desirable, from a data analysis standpoint, to translate displacements measured during perturbation experiments into functional strains.…”

“…In addition, it is also desirable, from a data analysis standpoint, to translate displacements measured during perturbation experiments into functional strains. While previous work has resolved strain using finite element analysis 40 and calculations that assume spherical deformation with loading, 39,41 the degree of strain itself affects whether a spherical or an elliptical geometry is most appropriate to assume, as elliptical caps form at low pressures, and more spherical caps at higher pressure. 36 We discuss here the design, construction, and evaluation of an integrated strain device that uses pressure to displace the bottoms of deformable well plates upon which living cells are cultured, and where applied strain can in turn be optically determined.…”