Cell motility and local viscoelasticity of fibroblasts
S. Park 1*, D. Koch 2, R. Cardenas 1, J. Kas 2 and C. K. Shih 1
1 University of Texas at Austin
2 University Leipzig
* To whom correspondence should be addressed. E-mail: sypark20{at}physics.utexas.edu.
Submitted on September 25, 2004
Revised on November 23, 2004
Accepted on 15 September 2005
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Abstract |
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Viscoelastic changes of the lamellipodial actin cytoskeleton are a fundamental element of cell motility. Thus, the correlation between the local viscoelastic properties of the lamellipodium (including the transitional region to the cell body) and the speed of lamellipodial extension is studied for normal and malignantly transformed fibroblasts. Using our AFM-based microrheology technique, we found different mechanical properties between the lamellipodia of malignantly transformed fibroblasts (H-ras transformed and SV-T2 fibroblasts) and normal fibroblasts (BALB 3T3 fibroblasts). The average elastic constants, K, in the leading edge of SV-T2 fibroblasts (0.48±0.51 kPa) and of H-ras transformed fibroblasts (0.42±0.35 kPa) are significantly lower than that of BALB 3T3 fibroblasts (1.01±0.40 kPa). The analysis of time-lapse phase contrast images shows that the decrease in the elastic constnat, K, for malignantly transformed fibroblasts is correlated with the enhanced motility of the lamellipodium. The measured mean speeds are 6.1±4.5 µm/h for BALB 3T3 fibroblast, 13.1& [plusmn]5.2 µm/h for SV-T2 fibroblast, and 26.2±11.5 µm/h for H-ras fibroblast. Furthermore, the elastic constant, K, increases towards the cell body in many instances which coincide with an increase in actin filament density towards the cell body. The correlation between the enhanced motility and the decrease in viscoelastic moduli supports the Elastic Brownian Ratchet model for driving lamellipodia extension (1).
Key Words:
AFM, actin, cell motility, cytoskeleton, microrheology, viscoelasticity
