title: Probing the viscoelastic behavior of cultured airway smooth muscle cells with atomic force microscopy: stiffening induced by contractile agonist.
abstract: Complex rheology of airway smooth muscle cells and its dynamic response during contractile stimulation involves many molecular processes, foremost of which are actomyosin cross-bridge cycling and actin polymerization. With an atomic force microscope, we tracked the spatial and temporal variations of the viscoelastic properties of cultured airway smooth muscle cells. Elasticity mapping identified stiff structural elements of the cytoskeletal network. Using a precisely positioned microscale probe, picoNewton forces and nanometer level indentation modulations were applied to cell surfaces at frequencies ranging from 0.5 to 100 Hz. The resulting elastic storage modulus (G') and dissipative modulus (G'') increased dramatically, with hysteresivity (eta = G''/G') showing a definitive decrease after stimulation with the contractile agonist 5-hydroxytryptamine. Frequency-dependent assays showed weak power-law structural damping behavior and universal scaling in support of the soft-glassy material description of cellular biophysics. Additionally, a high-frequency component of the loss modulus (attributed to cellular Newtonian viscosity) increased fourfold during the contractile process. The complex shear modulus showed a strong sensitivity to the degree of actin polymerization. Inhibitors of myosin light chain kinase activity had little effect on the stiffening response to contractile stimulation. Thus, our measurements appear to be particularly well suited for characterization of dynamic actin rheology during airway smooth muscle contraction.
authors.affiliation: Department of Physics, Nanoscience & Scanning Probe Microscopy Group, McGill University, Montreal, Quebec, Canada. bsmith@physics.mcgill.ca
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: Smith
authors.forename: Barbara
authors.initials: B
authors.lastname: Tolloczko
authors.forename: James G
authors.initials: JG
authors.lastname: Martin
authors.forename: Peter
authors.initials: P
authors.lastname: Grütter
mesh_terms: D000199:Actins / Q000737:chemistry; D000205:Actomyosin / Q000737:chemistry; D000818:Animals; D001703:Biophysics / Q000379:methods*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D004548:Elasticity; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D018625:Microscopy, Atomic Force / Q000379:methods*; D008954:Models, Biological; D015233:Models, Statistical; D009119:Muscle Contraction; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors; D051381:Rats; D011916:Rats, Inbred F344; D012212:Rheology; D012701:Serotonin / Q000494:pharmacology; D013314:Stress, Mechanical; D013997:Time Factors; D014132:Trachea / Q000378:metabolism / Q000473:pathology*; D014783:Viscosity
chemical_list: D000199:Actins; D004791:Enzyme Inhibitors; D015638:Cytochalasin D; D012701:Serotonin; D000205:Actomyosin; D009219:Myosin-Light-Chain Kinase