A thin-layer model for viscoelastic, stress-relaxation testing of cells using atomic force microscopy: Do cell properties reflect metastatic potential?
Eric M Darling 1, Stefan Zauscher 2, Joel A Block 3 and Farshid Guilak 1*
1 Duke University Medical Center
2 Duke University
3 Rush University Medical Center
* To whom correspondence should be addressed. E-mail: guilak{at}duke.edu.
Submitted on February 9, 2006
Revised on May 30, 2006
Accepted on 27 November 2006
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Abstract |
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Atomic force microscopy (AFM) has rapidly become a valuable tool for quantifying the biophysical properties of single cells. The interpretation of AFM-based indentation tests, however, is highly dependent on the use of an appropriate theoretical model of the testing configuration. In this study, a novel, thin-layer viscoelastic model for stress relaxation was developed to quantify the mechanical properties of chondrosarcoma cells in different configurations to examine the hypothesis that viscoelastic properties reflect the metastatic potential and invasiveness of the cell using three well-characterized human chondrosarcoma cell lines (JJ012, FS090, 105KC) that show increasing chondrocytic differentiation and decreasing malignancy, respectively. Single-cell stress relaxation tests were conducted at 2 hrs and 2 days following plating to determine cell mechanical properties in either spherical or spread morphologies and analyzed using the new theoretical model. At both time points, JJ012 cells had the lowest moduli of the cell lines examined, while FS090 typically had the highest. At 2 days, all cells showed an increase in stiffness and a decrease in apparent viscosity compared to the 2 hr time point. Fluorescent labeling showed that the F-actin structure in spread cells was significantly different between FS090 cells and JJ012/105KC cells. Taken together with results of previous studies, these findings indicate that cell transformation and tumorigenicity are associated with a decrease in cell modulus and apparent viscosity, suggesting that cell mechanical properties may provide insight into the metastatic potential and invasiveness of a cell.
Key Words:
F-actin cytoskeleton, cancer, cartilage, cell mechanics, chondrosarcoma, scanning probe microscope
