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We demonstrate the existence of such a regime in the living cell, but only at high frequencies

Fast and slow dynamics of the cytoskeleton.

NATURE MATERIALS, no. 8 (2006): 636.0-640

Cited by: 296|Views38
WOS SCOPUS NATURE

Abstract

Material moduli of the cytoskeleton (CSK) influence a wide range of cell functions(1-3). There is substantial evidence from reconstituted F-actin gels that a regime exists in which the moduli scale with frequency with a universal exponent of 3/4. Such behaviour is entropic in origin and is attributable to fluctuations in semi flexible pol...More

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Introduction
  • A major constituent of the CSK is F-actin. Reconstituted F-actin gels in vitro show clear evidence of semiflexible-polymer network dynamics[6,7,10,11].
  • Where G∗(f ) is the complex modulus, ρ,κ,ζ, and lp are the density, bending stiffness, lateral drag coefficient, and persistence length of actin filaments in the gel, respectively, and i2 = −1; here the authors have suppressed a small newtonian viscosity that contributes little except at very high frequencies.
  • In a variety of cell types, as well as in F-actin gels that are pre-stressed and crosslinked by filamin, dynamics of a rather different type have recently been reported[8,9,18,19,20].
Highlights
  • A major constituent of the CSK is F-actin
  • In a variety of cell types, as well as in F-actin gels that are pre-stressed and crosslinked by filamin, dynamics of a rather different type have recently been reported[8,9,18,19,20]. To fill this gap and to assess the existence of a regime comparable to that suggested by equation (1), here we report rheological properties of the freshly isolated living airway smooth muscle (ASM) cell
  • Compared with the CSK of the smooth muscle cell passaged in culture, that of the freshly isolated smooth muscle cell has substantially more organization[21], higher density of contractile filaments, more smooth-muscle-specific actin-binding proteins (h-caldesmon, h-1 calponin, and sm22) and myofilament bundles, but fewer microtubules (K.M., personal communication)
  • The observation of G∗ approaching f 3/4 at higher frequencies suggests the emergence of entropic dynamics associated with semiflexible polymers and in this report it is identified for the first time in living cells
  • Single ASM cells were freshly isolated from bovine trachea by enzymatic digestion, which was adopted from a previously described method[23]
  • The mean of α was 0.05 (95% confidence interval 0.04–0.06) and was different from zero (p < 0.00001); as described below, this implies that at low frequencies the system did not approach a hookean limit
  • In constantly oxygenated Krebs solution (120 mM NaCl, 5.9 mM KCl, 1.2 mM NaH2PO4, 25 mM NaHCO3, 11.5 mM dextrose, 1 mM CaCl2, and 1.4 mM MgCl2), 50 mg wet weight of ASM was dissected from the trachea and cut into 2 × 3 mm pieces
Results
  • To fill this gap and to assess the existence of a regime comparable to that suggested by equation (1), here the authors report rheological properties of the freshly isolated living airway smooth muscle (ASM) cell.
  • The mean of β was 0.75, (95% confidence interval 0.69–0.79) and was different from unity (p < 0.00001); as described below, this implies that at high frequencies the system did not approach a newtonian limit.
  • Such high-frequency dynamics have not been noted previously in the living cell in retrospect, a hint of such behaviour is evident in cells passaged in culture[24].
  • At lower frequencies semiflexible-polymer dynamics became subdominant, with the complex modulus scaling as f 0.05.
  • The exponent β was not influenced by relaxation, but decreased during contraction from 0.75 to 0.64 (95% confidence interval 0.57 to 0.71) (Supplementary Information Fig. S2, top), suggesting that contraction altered the qualitative nature of the high-frequency behaviour, whereas relaxation did not.
  • The observation of G∗ approaching f 3/4 at higher frequencies suggests the emergence of entropic dynamics associated with semiflexible polymers and in this report it is identified for the first time in living cells.
  • The authors conclude that in the living cell the dynamics of semiflexible polymers and soft glasses coexist, but each dominates nature materials VOL 5 AUGUST 2006 www.nature.com/naturematerials
Conclusion
  • All prior measurements in other cell systems show power-law responses with non-universal exponents in the range 0.1–0.3, and it was not clear from those measurements if a distinct highfrequency regime might exist.
  • The authors measured the complex modulus as a function of frequency by applying an oscillatory magnetic field and measuring the resultant oscillatory bead motions with light microscopy[24,37] (Fig. 1c).
  • This can be converted to familiar material moduli with the use of a length scale derived from a model of cell deformation[40], but to avoid model-dependent assumptions here the authors report all data in primary measurement units of Pa nm−1.
Summary
  • A major constituent of the CSK is F-actin. Reconstituted F-actin gels in vitro show clear evidence of semiflexible-polymer network dynamics[6,7,10,11].
  • Where G∗(f ) is the complex modulus, ρ,κ,ζ, and lp are the density, bending stiffness, lateral drag coefficient, and persistence length of actin filaments in the gel, respectively, and i2 = −1; here the authors have suppressed a small newtonian viscosity that contributes little except at very high frequencies.
  • In a variety of cell types, as well as in F-actin gels that are pre-stressed and crosslinked by filamin, dynamics of a rather different type have recently been reported[8,9,18,19,20].
  • To fill this gap and to assess the existence of a regime comparable to that suggested by equation (1), here the authors report rheological properties of the freshly isolated living airway smooth muscle (ASM) cell.
  • The mean of β was 0.75, (95% confidence interval 0.69–0.79) and was different from unity (p < 0.00001); as described below, this implies that at high frequencies the system did not approach a newtonian limit.
  • Such high-frequency dynamics have not been noted previously in the living cell in retrospect, a hint of such behaviour is evident in cells passaged in culture[24].
  • At lower frequencies semiflexible-polymer dynamics became subdominant, with the complex modulus scaling as f 0.05.
  • The exponent β was not influenced by relaxation, but decreased during contraction from 0.75 to 0.64 (95% confidence interval 0.57 to 0.71) (Supplementary Information Fig. S2, top), suggesting that contraction altered the qualitative nature of the high-frequency behaviour, whereas relaxation did not.
  • The observation of G∗ approaching f 3/4 at higher frequencies suggests the emergence of entropic dynamics associated with semiflexible polymers and in this report it is identified for the first time in living cells.
  • The authors conclude that in the living cell the dynamics of semiflexible polymers and soft glasses coexist, but each dominates nature materials VOL 5 AUGUST 2006 www.nature.com/naturematerials
  • All prior measurements in other cell systems show power-law responses with non-universal exponents in the range 0.1–0.3, and it was not clear from those measurements if a distinct highfrequency regime might exist.
  • The authors measured the complex modulus as a function of frequency by applying an oscillatory magnetic field and measuring the resultant oscillatory bead motions with light microscopy[24,37] (Fig. 1c).
  • This can be converted to familiar material moduli with the use of a length scale derived from a model of cell deformation[40], but to avoid model-dependent assumptions here the authors report all data in primary measurement units of Pa nm−1.
Funding
  • X.T. is supported by a postdoctoral fellowship from the Spanish Ministerio de Educacion y Ciencia
  • This study was financially supported by NIH HL65960, HL33009 and HL31704
Study subjects and analysis
data: 64
Although our technology is limited to frequencies below 1 kHz, our data were sufficient to resolve the exponents α and β and put relatively narrow bounds on their values (see the additional comments on statistical tests in the Supplementary Information). Across the cell population (N = 64), the distributions of α and β were approximately normal (Fig. 4). The mean of α was 0.05 (95% confidence interval 0.04–0.06) and was different from zero (p < 0.00001); as described below, this implies that at low frequencies the system did not approach a hookean limit

Reference
  • Chicurel, M. E., Chen, C. S. & Ingber, D. E. Cellular control lies in the balance of forces. Curr. Opin. Cell. Biol. 10, 232–239 (1998).
    Google ScholarLocate open access versionFindings
  • Discher, D. E., Janmey, P. & Wang, Y. L. Tissue cells feel and respond to the stiffness of their substrate. Science 310, 1139–1143 (2005).
    Google ScholarLocate open access versionFindings
  • Janmey, P. A. & Weitz, D. A. Dealing with mechanics: mechanisms of force transduction in cells. Trends Biochem. Sci. 29, 364–370 (2004).
    Google ScholarLocate open access versionFindings
  • Gittes, F., Schnurr, B., Olmsted, P. D., MacKintosh, F. C. & Schmidt, C. F. Microscopic viscoelasticity: Shear moduli of soft materials determined from thermal fluctuations. Phys. Rev. Lett. 79, 3286–3289 (1997).
    Google ScholarLocate open access versionFindings
  • Morse, D. C. Viscoelasticity of concentrated isotropic solutions of semiflexible polymers.
    Google ScholarFindings
  • 2. Linear response. Macromolecules 31, 7044–7067 (1998).
    Google ScholarLocate open access versionFindings
  • 6. Gardel, M. L., Valentine, M. T., Crocker, J. C., Bausch, A. R. & Weitz, D. A. Microrheology of entangled F-actin solutions. Phys. Rev. Lett. 91, 158302 (2003).
    Google ScholarLocate open access versionFindings
  • 7. Gardel, M. L. et al. Elastic behavior of cross-linked and bundled actin networks. Science 304, 1301–1305 (2004).
    Google ScholarLocate open access versionFindings
  • 8. Fabry, B. et al. Scaling the microrheology of living cells. Phys. Rev. Lett. 87, 148102 (2001).
    Google ScholarLocate open access versionFindings
  • 9. Bursac, P. et al. Cytoskeletal remodelling and slow dynamics in the living cell. Nature Mater. 4, 557–561 (2005).
    Google ScholarLocate open access versionFindings
  • 10. Kas, J., Strey, H. & Sackmann, E. Direct imaging of reptation for semiflexible actin filaments. Nature 368, 226–229 (1994).
    Google ScholarLocate open access versionFindings
  • 11. MacKintosh, F. C., Kas, J. & Janmey, P. A. Elasticity of semiflexible biopolymer networks. Phys. Rev. Lett. 75, 4425–4428 (1995).
    Google ScholarLocate open access versionFindings
  • 12. Gittes, F. & MacKintosh, F. C. Dynamic shear modulus of a semiflexible polymer network. Phys. Rev. E 58, R1241–R1244 (1998).
    Google ScholarLocate open access versionFindings
  • 13. Gisler, T. & Weitz, D. A. Scaling of the microrheology of semidilute F-actin solutions. Phys. Rev. Lett. 82, 1606–1609 (1999).
    Google ScholarLocate open access versionFindings
  • 14. Gardel, M. L. et al. Scaling of F-actin network rheology to probe single filament elasticity and dynamics. Phys. Rev. Lett. 93, 188102 (2004).
    Google ScholarLocate open access versionFindings
  • 15. Morse, D. C. Viscoelasticity of tightly entangled solutions of semiflexible polymers. Phys. Rev. E 58, R1237–R1240 (1998).
    Google ScholarLocate open access versionFindings
  • 16. Morse, D. C. Viscoelasticity of concentrated isotropic solutions of semiflexible polymers.
    Google ScholarFindings
  • 1. Model and stress tensor. Macromolecules 31, 7030–7043 (1998).
    Google ScholarLocate open access versionFindings
  • 17. Stamenovic, D., Suki, B., Fabry, B., Wang, N. & Fredberg, J. J. Rheology of airway smooth muscle cells is associated with cytoskeletal contractile stress. J. Appl. Physiol. 96, 1600–1605 (2004).
    Google ScholarLocate open access versionFindings
  • 18. Alcaraz, J. et al. Microrheology of human lung epithelial cells measured by atomic force microscopy. Biophys. J. 84, 2071–2079 (2003).
    Google ScholarLocate open access versionFindings
  • 19. Desprat, N., Richert, A., Simeon, J. & Asnacios, A. Creep function of a single living cell. Biophys. J. 88, 2224–2233 (2005).
    Google ScholarLocate open access versionFindings
  • 20. Gardel, M. L. et al. Prestressed F-actin networks cross-linked by hinged filamins replicate mechanical properties of cells. Proc. Natl Acad. Sci. USA 103, 1762–1767 (2006).
    Google ScholarLocate open access versionFindings
  • 21. Draeger, A., Stelzer, E., Herzog, M. & Small, J. Unique geometry of actin-membrane anchorage sites in avian gizzard smooth muscle cells. J. Cell Sci. 94, 703–711 (1989).
    Google ScholarLocate open access versionFindings
  • 22. Bagby, R. M., Young, A. M., Dotson, R. S., Fisher, B. A. & McKinnon, K. Contraction of single smooth muscle cells from Bufo marinus stomach. Nature 234, 351–352 (1971).
    Google ScholarLocate open access versionFindings
  • 23. DeFeo, T. T. & Morgan, K. G. Responses of enzymatically isolated mammalian vascular smooth muscle cells to pharmacological and electrical stimuli. Pflugers Arch. 404, 100–102 (1985).
    Google ScholarLocate open access versionFindings
  • 24. Fabry, B. et al. Time scale and other invariants of integrative mechanical behavior in living cells. Phys. Rev. E 68, 041914 (2003).
    Google ScholarLocate open access versionFindings
  • 25. Sollich, P., Lequeux, F., Hebraud, P. & Cates, M. E. Rheology of soft glassy materials. Phys. Rev. Lett. 78, 2020–2023 (1997).
    Google ScholarLocate open access versionFindings
  • 26. Cates, M. E. & Sollich, P. in Foams and Emulsions (eds Sadoc, J. F. & Rivier, N.) 207–236 (Kluwer Academic, Dordrecht, 1999).
    Google ScholarFindings
  • 27. Mason, T. G., Gisler, T., Kroy, K., Frey, E. & Weitz, D. A. Rheology of F-actin solutions determined from thermally driven tracer motion. J. Rheol. 44, 917–928 (2000).
    Google ScholarLocate open access versionFindings
  • 28. Gopal, A. D. & Durian, D. J. Relaxing in foam. Phys. Rev. Lett. 91, 188303 (2003).
    Google ScholarLocate open access versionFindings
  • 29. Puig-de-Morales, M. et al. Cytoskeletal mechanics in adherent human airway smooth muscle cells: probe specificity and scaling of protein-protein dynamics. Am. J. Physiol. Cell Physiol. 287, C643–C654 (2004).
    Google ScholarLocate open access versionFindings
  • 30. Wang, N. et al. Cell prestress. I. Stiffness and prestress are closely associated in adherent contractile cells. Am. J. Physiol. Cell Physiol. 282, C606–C616 (2002).
    Google ScholarLocate open access versionFindings
  • 31. Bulatov, V. V. & Argon, A. S. A stochastic-model for continuum elastoplastic behavior. 2. A study of the glass-transition and structural relaxation. Modelling Simul. Mater. Sci. Eng. 2, 185–202 (1994).
    Google ScholarLocate open access versionFindings
  • 32. Weeks, E. R., Crocker, J. C., Levitt, A. C., Schofield, A. & Weitz, D. A. Three-dimensional direct imaging of structural relaxation near the colloidal glass transition. Science 287, 627–631 (2000).
    Google ScholarLocate open access versionFindings
  • 33. Mazurin, O. V. Theory of glass-transition—chemical-equilibria approach. J. Non-Cryst. Solids 129, 259–265 (1991).
    Google ScholarLocate open access versionFindings
  • 34. Kovacs, A. J., Aklonis, J. J., Hutchinson, J. M. & Ramos, A. R. Isobaric volume and enthalpy recovery of glasses.
    Google ScholarFindings
  • 2. Transparent multi-parameter theory. J. Polym. Sci. Polym. Phys. 17, 1097–1162 (1979).
    Google ScholarLocate open access versionFindings
  • 35. Chen, H. S. & Turnbull, D. Evidence of a glass–liquid transition in a gold–germanium–silicon alloy. J. Chem. Phys. 48, 2560–2571 (1968).
    Google ScholarLocate open access versionFindings
  • 36. Sollich, P. Rheological constitutive equation for a model of soft glassy materials. Phys. Rev. E 58, 738–759 (1998).
    Google ScholarLocate open access versionFindings
  • 37. Wang, N., Butler, J. P. & Ingber, D. E. Mechanotransduction across the cell surface and through the cytoskeleton. Science 260, 1124–1127 (1993).
    Google ScholarLocate open access versionFindings
  • 38. Deng, L., Fairbank, N. J., Fabry, B., Smith, P. G. & Maksym, G. N. Localized mechanical stress induces time-dependent actin cytoskeletal remodeling and stiffening in cultured airway smooth muscle cells. Am. J. Physiol. Cell Physiol. 287, C440–C448 (2004).
    Google ScholarLocate open access versionFindings
  • 39. Choquet, D., Felsenfeld, D. P. & Sheetz, M. P. Extracellular matrix rigidity causes strengthening of integrin-cytoskeleton linkages. Cell 88, 39–48 (1997).
    Google ScholarLocate open access versionFindings
  • 40. Mijailovich, S. M., Kojic, M., Zivkovic, M., Fabry, B. & Fredberg, J. J. A finite element model of cell deformation during magnetic bead twisting. J. Appl. Physiol. 93, 1429–1436 (2002).
    Google ScholarLocate open access versionFindings
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