Quantitative morphodynamics of endothelial cells within confluent culturesin response to fluid shear stress

To evaluate shear stress-induced effects on cultured cells we have extended the mechanical setup of a multichannel in vitro rheological system and dev eloped software allowing entire processing control and image data analysis. The Values of cell motility, degree of orientation (alignment), and cell e longation were correlated as a function of time (morphodynamics). Collectiv e and individual endothelial cells within confluent cultures displayed a sh ear stress-dependent characteristic phase behavior of the following time co urse: resting conditions (phase I), change of motility (phase II), onset of alignment (phase III), and finally cell elongation (phase IV). Especially cell motility was characterized by a randomized zigzag movement around mean trajectories (fluctuations) together with mean cell locomotion. Onset of s hear stress caused a down-regulation of fluctuations of 30% within <10 min and simultaneously increased locomotion velocities preferring the flow dire ction (phase II). After a lag period of 10 to 20 min cells orientated in th e direction of flow (phase III) without significant cell elongation, which finally occurs within hours (phase IV). These data provide first evidence t hat cells within confluent endothelial monolayers respond to shear stress w ith a characteristic phase behavior.