cyclic stress at mhz frequencies aligns fibroblasts in direction of zero strain循环应力在兆赫频率对齐成纤维细胞在零压力的方向.pdfVIP

Cyclic Stress at mHz Frequencies Aligns Fibroblasts in Direction of Zero Strain 1. 1. 1 1¤ 2 1 Uta Faust , Nico Hampe , Wolfgang Rubner , Norbert Kirchgeßner , Sam Safran , Bernd Hoffmann *, Rudolf Merkel1 ¨ ¨ 1 Institute of Complex Systems, ICS-7, Biomechanics, Forschungszentrum Julich GmbH, Julich, Germany, 2 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot, Israel Abstract Recognition of external mechanical signals is vital for mammalian cells. Cyclic stretch, e.g. around blood vessels, is one such signal that induces cell reorientation from parallel to almost perpendicular to the direction of stretch. Here, we present quantitative analyses of both, cell and cytoskeletal reorientation of umbilical cord fibroblasts. Cyclic strain of preset amplitudes was applied at mHz frequencies. Elastomeric chambers were specifically designed and characterized to distinguish between zero strain and minimal stress directions and to allow accurate theoretical modeling. Reorientation was only induced when the applied stretch exceeded a specific amplitude, suggesting a non-linear response. However, on very soft substrates no mechanoresponse occurs even for high strain. For all stretch amplitudes, the angular distributions of reoriented cells are in very good agreement with a theory modeling stretched cells as active force dipoles. Cyclic stretch increases the number of stress fibers and the coupling to adhesions. We show that changes in cell shape follow cytoskeletal reorie