Quantification of stromal vascular cell mechanics with a linear cell monolayer rheometer

• Published in: Journal of rheology (New York : 1978) 2015-01, Vol.59 (1), p.33-50
• Main Authors: Elkins, Claire M., Shen, Wen-Jun, Khor, Victor K., Kraemer, Fredric B., Fuller, Gerald G.
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; ACTIN; ATOMIC FORCE MICROSCOPY; COLLAGEN; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; FILAMENTS; FLEXIBILITY; MICROTUBULES; PLATES; PROBES; RELAXATION; RHEOLOGY; SHEAR PROPERTIES; STRAINS; STRESSES; TRANSDUCERS
• ISSN: 0148-6055; 1520-8516
• DOI: 10.1122/1.4902437

Over the past few decades researchers have developed a variety of methods for measuring the mechanical properties of whole cells, including traction force microscopy, atomic force microscopy (AFM), and single-cell tensile testing. Though each of these techniques provides insight into cell mechanics, most also involve some nonideal conditions for acquiring live cell data, such as probing only one portion of a cell at a time, or placing the cell in a nonrepresentative geometry during testing. In the present work, we describe the development of a linear cell monolayer rheometer (LCMR) and its application to measure the mechanics of a live, confluent monolayer of stromal vascular cells. In the LCMR, a monolayer of cells is contacted on both top and bottom by two collagen-coated plates and allowed to adhere. The top plate then shears the monolayer by stepping forward to induce a predetermined step strain, while a force transducer attached to the top plate collects stress information. The stress and strain data are then used to determine the maximum relaxation modulus recorded after step-strain, Gr0, referred to as the zero-time relaxation modulus of the cell monolayer. The present study validates the ability of the LCMR to quantify cell mechanics by measuring the change in Gr0 of a confluent cell monolayer upon the selective inhibition of three major cytoskeletal components (actin microfilaments, vimentin intermediate filaments, and microtubules). The LCMR results indicate that both actin- and vimentin-deficient cells had ∼50% lower Gr0 values than wild-type, whereas tubulin deficiency resulted in ∼100% higher Gr0 values. These findings constitute the first use of a cell monolayer rheometer to quantitatively distinguish the roles of different cytoskeletal elements in maintaining cell stiffness and structure. Significantly, they are consistent with results obtained using single-cell mechanical testing methods, suggesting that the rheology-based LCMR technique may be a useful tool for rapid analysis of cell mechanics by shearing an entire cell monolayer.