Papers of the Year
Dynamic Changes of Traction Force at Focal Adhesions during Macroscopic Cell Stretching Using an Elastic Micropillar Substrate: Tensional Homeostasis of Aortic Smooth Muscle Cells
In order to determine how cells change their traction forces at focal adhesions (FAs) under macroscopic deformation conditions, we investigated the dynamic changes in traction force at FAs by culturing porcine aortic smooth muscle cells (SMCs) on elastic micropillar substrates and giving them macroscopic deformation by stretching the substrates. We patterned adhesion region on the top surface of a polydimethylsiloxane-based micropillar array using our original micropatterning technique to align the cells on the pillar array parallel to the stretch direction. SMCs plated on the micropillars successfully spread in the adhesion region and their actin stress fibers (SFs) aligned in the direction to be stretched. Cells were then stretched and released cyclically with strain rates of 0.3%/15s up to 3--6% strain, and deflection of micropillars at both side regions of cells were measured simultaneously to obtain the traction force at each FA in situ. SMCs aligned in the stretch direction showed two types of responses: almost a half of the SMCs changed their force in phase with the applied strain, and showed gradual active contraction with the stretch cycles (synchronous group); and the rest tended to keep their force constant and became elongated with the cycles (asynchronous group). In the asynchronous group, the force sometimes changed in antiphase with the cell strain as if the cells maintain intracellular traction force at a constant level. These results may indicate that SMCs sometimes exhibit active homeostatic responses to keep their pretension constant during macroscopic stretching, and such tensional homeostatic responses may occur concurrently with cell elongation.
- Cell Biomechanics, Mechanical Properties, Stress Fibers, Force Transmission, Cytoskeleton
- Paper information
- Kazuaki NAGAYAMA, Akifumi ADACHI and Takeo MATSUMOTO, “Dynamic Changes of Traction Force at Focal Adhesions during Macroscopic Cell Stretching Using an Elastic Micropillar Substrate: Tensional Homeostasis of Aortic Smooth Muscle Cells”, Journal of Biomechanical Science and Engineering, Vol. 7, No. 2 (2012), pp.130-140 . doi:10.1299/jbse.7.130
High Time Resolution Time-Lapse Imaging Reveals Continuous Existence and Rotation of Stress Fibers under Cyclic Stretch in HUVEC
- Release Date :
Cells under cyclic stretch sense their environments and induce responses such as actin stress fiber (SF) reorientation and morphological changes. These physiological responses are thought to occur when cells sense incompatibility between SF orientation and stretching direction. This hypothesis requires existence of SFs. However, such existence of SFs in cells under cyclic stretch remains unclear since few studies attempted to track the existence of SFs throughout cyclic stretch. In order to track the existence of SFs throughout cyclic stretch, high time resolution time-lapse imaging was improved in two points. First, SFs were clearly imaged with coexpression of DsRed-zyxin and GFP-actin. Second, time resolution was improved so that fluorescence images were obtained every 28 sec. With the improved high time resolution time-lapse imaging, it was revealed, for the first time, that SFs could exist continuously throughout cyclic stretch. Moreover, physiological responses including morphological change as well as SF reorientation occurred during the time when SFs formed incompatibility between SF orientation and stretching direction. These results demonstrated that SFs continuously existed in cells under cyclic stretch and in turn suggested that continuous presence of incompatibility between orientation of long-lasting SFs and the stretching direction might be important for mechanosensing which induces physiological responses.
- Cyclic Stretch, Stress Fiber, Orientation Dynamics, Morphological Change, Time-Lapse Imaging, HUVEC
- Paper information
- Yusuke MITSUOKA, Akira TSUKAMOTO, Shunsuke IWAYOSHI, Katsuko S. FURUKAWA and Takashi USHIDA, “High Time Resolution Time-Lapse Imaging Reveals Continuous Existence and Rotation of Stress Fibers under Cyclic Stretch in HUVEC”, Journal of Biomechanical Science and Engineering, Vol. 7, No. 2 (2012), pp.188-198 . doi:10.1299/jbse.7.188