Investigation on the effects of variable shear stress on monocyte cell morphology

Abstract

Microchannels fabricated by soft lithography have been favourable in mechanobiological applications for cell culture platforms, especially shear stress studies. Normally, physiological shear stress levels for veins are between 10 and 70 dynes/cm 2 (1-7 Pa) and arteries between 1 and 6 dynes/cm 2 (0.1-0.7 Pa). In this work, a circular system has been set up by microfluidic pump to mimic physiological environment of monocyte cells for monitoring structural changes at various levels of shear stresses. Shear stresses at 4, 15 and 45 Pa, low, medium and high stresses, respectively, simulated by CFD have been applied on THP-1 cells under different flow rates for 0.5 and 3 h. These cells, which passed through microchannels under these experimental conditions were analysed for their F-actin content by staining with phalloidin and determination of mean fluorescence intensity by fluorescence microscopy and flow cytometry. An increase in THP-1 monocytic cell actin polymerisation is significant in the case of 15 Pa, and slight in the case of 45 Pa shear stress conditions for 0.5 h. This may reflect the structural adaptation of monocytes during a pathological condition such as atherosclerosis.

Mechanical shear stress and leukocyte phenotype and function: Implications for ventricular assist device development and use

“…Monocytes can react to biomaterials through 'frustrated phagocytosis' 45 and high shear on monocytes induces F-actin synthesis for pseudopod extension. 72 This might be why monocyte deactivation occurred. 8 Immunosuppression can also occur through effects on T cells.…”

“…71 While F-actin becomes condensed in neutrophils, an increase in its synthesis in monocytes has been observed when applying 12 Pa shear stress using a microfluidic pump. 72 F-actin is used for pseudopod extension in phagocytosis 73 so it is possible that elevated shear stress underpins the 'frustrated phagocytosis' noted earlier.…”