title: Relationship between cell stiffness and stress fiber amount, assessed by simultaneous atomic force microscopy and live-cell fluorescence imaging.
abstract: Actomyosin stress fibers, one of the main components of the cell's cytoskeleton, provide mechanical stability to adherent cells by applying and transmitting tensile forces onto the extracellular matrix (ECM) at the sites of cell-ECM adhesion. While it is widely accepted that changes in spatial and temporal distribution of stress fibers affect the cell's mechanical properties, there is no quantitative knowledge on how stress fiber amount and organization directly modulate cell stiffness. We address this key open question by combining atomic force microscopy with simultaneous fluorescence imaging of living cells, and combine for the first time reliable quantitative parameters obtained from both techniques. We show that the amount of myosin and (to a lesser extent) actin assembled in stress fibers directly modulates cell stiffness in adherent mouse fibroblasts (NIH3T3). In addition, the spatial distribution of stress fibers has a second-order modulatory effect. In particular, the presence of either fibers located in the cell periphery, aligned fibers or thicker fibers gives rise to reinforced cell stiffness. Our results provide basic and significant information that will help design optimal protocols to regulate the mechanical properties of adherent cells via pharmacological interventions that alter stress fiber assembly or via micropatterning techniques that restrict stress fiber spatial organization.
authors.affiliation: School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London, E1 3NS, UK. n.gavara@qmul.ac.uk.
authors.forename: Núria
authors.initials: N
authors.lastname: Gavara
authors.affiliation: Auditory Mechanics Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Building 10 Rm. 5D49, 10 Center Drive, MSC-1417, Bethesda, MD, 20892, USA.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Chadwick
mesh_terms: D000205:Actomyosin / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D003599:Cytoskeleton / Q000378:metabolism; D055119:Elastic Modulus; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051379:Mice; D018625:Microscopy, Atomic Force / Q000379:methods*; D008856:Microscopy, Fluorescence / Q000379:methods*; D009218:Myosins / Q000378:metabolism; D041681:NIH 3T3 Cells; D022502:Stress Fibers / Q000378:metabolism*; D014162:Transfection
chemical_list: D049452:Green Fluorescent Proteins; D000205:Actomyosin; D009218:Myosins
keywords: Actomyosin; Atomic force microscopy; Cell mechanics; Cytoskeleton; Image processing and quantification; Stress fibers