Effect of Cyclic Strain on the Orientation of Cultured Macrophages

Abstract

When macrophages are cultured under cyclic strain, they align parallel to the direction of strain, in contrast to the perpendicular alignment reported for other types of cells. However, the time at which their orientation starts and the influence of fluid shear stress acting on cells during cyclic stretching have not been identified. In the present study, murine peritoneal macrophages were attached to silicone membranes and cultured up to 8 hours under cyclic uniaxial stretch of 10% amplitude and 1 Hz frequency. Cell morphology was observed and the angle of orientation of spindle-shaped cells (spindle cells) was determined. Distributions of actins in macrophages were also examined after the application of cyclic strain. Percentage of spindle cells increased with culture period, and the cells were getting longer with time. After around 2 hours, spindle cells started to align parallel to the direction of strain. At 8 hours, 53% of spindle cells were aligned within the angle of 20 degrees to the direction of strain. Prior to the orientation of cell bodies, accumulation of actin filaments was observed in the peripheral area of cells in the direction parallel to the strain direction. When the silicone membranes were moved back-and-forth in culture medium without stretching for 8 hours, macrophages did not show preferential orientation. These results suggest that macrophages actively align parallel to the direction of strain and start to orient around 2 hours after the initiation of cyclic strain.

Keywords

• cellular biomechanics
• macrophage
• culture
• cyclic strain
• cell orientation
• actin filament