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The effect of wall shear stress gradient on the deformation and rotation of each cell was investigated in vitro. To make a Couette-type of shear flow, the culture medium fluid was sandwiched with a constant gap between parallel walls: a lower stationary culture disk, and an upper rotating disk. Mouse fat precursor cells (3T3-L1) were used in this experiment. After cultivation without flow for 24 hours for adhesion of cells on the lower plate, a shear stress of less than 2 Pa was continuously applied to cells for 24 hours in the incubator. The behavior (deformation and major axis angle) of each single cell was tracked using time-lapse images observed by an inverted phase contrast microscope placed in the incubator. For wall shear stresses of less than 1.9 Pa, each cell exhibited active behavior: migration, deformation, and rotation. Whereas, the cells transformed into spheres when wall shear stress was higher than 1.9 Pa. In addition, the cells were observed to tilt against for a wall shear stress gradient approaching 50 Pa/m. |
