title: Cell shape-dependent early responses of fibroblasts to cyclic strain.
abstract: Randomly spread fibroblasts on fibronectin-coated elastomeric membranes respond to cyclic strain by a varying degree of focal adhesion assembly and actin reorganization. We speculated that the individual shape of the cells, which is linked to cytoskeletal structure and pre-stress, might tune these integrin-dependent mechanotransduction events. To this aim, fibronectin circles, squares and rectangles of identical surface area (2000μm(2)) were micro-contact printed onto elastomeric substrates. Fibroblasts plated on these patterns occupied the corresponding shapes. Cyclic 10% equibiaxial strain was applied to patterned cells for 30min, and changes in cytoskeleton and cell-matrix adhesions were quantified after fluorescence staining. After strain, megakaryocytic leukemia-1 protein translocated to the nucleus in most cells, indicating efficient RhoA activation independently of cell shape. However, circular and square cells (with radial symmetry) showed a significantly greater increase in the number of actin stress fibers and vinculin-positive focal adhesions after cyclic strain than rectangular (bipolar) cells of identical size. Conversely, cyclic strain induced larger changes in pY397-FAK positive focal complexes and zyxin relocation from focal adhesions to stress fibers in bipolar compared to symmetric cells. Thus, radially symmetric cells responded to cyclic strain with a larger increase in assembly, whereas bipolar cells reacted with more pronounced reorganization of actin stress fibers and matrix contacts. We conclude that integrin-mediated responses to external mechanical strain are differentially modulated in cells that have the same spreading area but different geometries, and do not only depend on mere cell size.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopaedics, University of Bern, Switzerland.
authors.forename: Neha
authors.initials: N
authors.lastname: Gadhari
authors.affiliation: Laboratory for Surface Science and Technology, Department of Material Science, ETH, Zurich, Switzerland.
authors.forename: Mirren
authors.initials: M
authors.lastname: Charnley
authors.affiliation: Microsystems Laboratory, Ecole Polytechnique Federale de Lausanne, EPFL, Lausanne, Switzerland.
authors.forename: Mattia
authors.initials: M
authors.lastname: Marelli
authors.affiliation: Microsystems Laboratory, Ecole Polytechnique Federale de Lausanne, EPFL, Lausanne, Switzerland.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Brugger
authors.affiliation: Department of Orthodontics and Dentofacial Orthopaedics, University of Bern, Switzerland. Electronic address: matthias.chiquet@zmk.unibe.ch.
authors.forename: Matthias
authors.initials: M
authors.lastname: Chiquet
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects; D005353:Fibronectins / Q000494:pharmacology; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism; D006736:Horses; D051379:Mice; D008954:Models, Biological; D011327:Printing; D021381:Protein Transport / Q000187:drug effects; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism; D013314:Stress, Mechanical; D015534:Trans-Activators / Q000378:metabolism; D060589:Zyxin / Q000378:metabolism; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D005353:Fibronectins; C511173:Mrtfa protein, mouse; D015534:Trans-Activators; D060589:Zyxin; D054460:rho-Associated Kinases
keywords: 4′,6-diamidino-2-phenylindole; Actin cytoskeleton; BSA; Bovine Serum Albumin; Cell shape; Cyclic strain; DAPI; DMEM; Dulbecco's Modified Eagle's Medium; ECM; FAK; FCS; Focal adhesion; HMDS; LIM; MEFs; MKL-1; Micro-contact printing; PBS; PDMS; ROCK; Ras homolog gene family, member A; Rho-associated Protein Kinase; RhoA; SRF; TRITC; extracellular matrix; fetal calf serum; focal adhesion kinase; hexamethyldisiloxane; lin-11, Isl-1 and mec-3; megakaryocytic leukemia-1; mouse embryonic fibroblasts; phosphate-buffered saline; polydimethylsiloxane; serum response factor; tetramethylrhodamine isothiocyanate