Stressed polystyrene causes increased membrane sensitivity of adherent cells to fluid shear force: technical note

Adherent cells transduce signals from the extracellular matrix, which result in changes to various cell functions, including cell spreading and morphology. However, changes to mechanical properties of cell membranes due to adherence to a substratum have not been studied. Adherent Nara Bladder Tumour (NBT) II cells on polystyrene (PS) discs made from pure, atactic polystyrene react differently between the peripheral 1mm zone and centre of the disc. After application of a fluid shear force, cells on the peripheral zone resulted in 91.1-/+0.8% cell death due to instantaneous rupture of apical cell membrane, as determined by the Live/Dead cell assay, whereas cells on the disc's centre and surrounding glass surface showed 7.1-/+5.7% and 4.3-/+1.7% cell death, respectively. Under cross-polarized light, the edge of the PS disc showed a low degree of birefringence whereas the centre of the disc did not. We also detached the PS disc and applied various weights (0.0 g to 40 g) to the disc at 100 degrees C for 2 hours and then cooled rapidly at 4 degrees C. We found that birefringence developed with stress to PS. NBT II cells grown on stressed PS showed an average of 55.8-/+14.1% cell death after a fluid shear force while cells on the glass surfaces resulted in only 5.0-/+2.7% cell death. Interestingly, increased birefringence is associated with increased lipophilicity on stressed PS, as determined by Nile Red staining. We propose that NBT II cell interaction with certain molecular characteristics of stressed PS results in altered cell membrane sensitivity to mechanical forces.