TITLE:
In Situ Observation and Measurement of Actin Stress Fiber Deformation in Stretched Osteoblast like Cell
AUTHORS:
Katsuya Sato, Kenta Nunobiki, Shoichiro Fujisawa, Tasuku Nakahara, Kazuyuki Minami
KEYWORDS:
Actin Cytoskeleton, Stretching Stimuli, Osteoblast, Cell Biomechanics, MEMS
JOURNAL NAME:
Advances in Bioscience and Biotechnology,
Vol.8 No.11,
November
21,
2017
ABSTRACT: It is
believed that mechanical stimuli, such as stretching of the extracellular matrix,
are transmitted into cells via focal adhesion complexes and the actin cytoskeleton. Transmission dynamics of strain from
the extracellular matrix into intracellular
organelles is crucial to clarify the mechanosensing mechanisms of cells.
In this study, we observed deformation behavior of actin stress fibers under
uniaxial stretch using an originally developed cell-stretching microelectromechanical system
(MEMS) device. It was difficult to conduct in situ observation
of cells under stretch using conventional cell stretching devices, because motion artifacts such as rigid displacement
during stretch application were not
negligible. Our novel cell-stretching MEMS device suppressed rigid displacement
while stretching, and we succeeded in obtaining time-lapse images of stretched cells. Uniaxial strain with a 10% magnitude and
strain rate of 0.5%/sec was applied
to cells. Deformation behaviors of the cells and actin stress fibers were recorded
using a confocal laser scanning microscope. In time-lapse images of stretched cells, strains along each stress
fiber were measured manually. As a result,
in cells with a relatively homogeneous stress fiber structure oriented
in one direction, distribution of the axial strain on stress fibers generally
corresponded to deformation of the stretching sheet on which the cells had
adhered. However, in cells with a heterogeneous
stress fiber structure oriented in several directions, we found that the
strain distribution along stress fibers was not homogeneous. In regions around
the cell nucleus, there was a more complicated
strain distribution compared with other regions. Our results suggest the
cell nucleus with a stiff mechanical resistance
yields such a complicated strain distribution in stress fibers.