Electrical impedance of cultured endothelium under fluid flow

The morphological and functional status of organs, tissues, and cells can b e assessed by evaluating their electrical impedance. Fluid shear stress reg ulates the morphology and function of endothelial cells in vitro. In this s tudy, an electrical biosensor was used to investigate the dynamics of flow- induced alterations in endothelial cell morphology in vitro. Quantitative, real-time changes in the electrical impedance of endothelial monolayers wer e evaluated using a modified electric cell-substrate impedance sensing (ECI S) system. This ECIS/Flow system allows for a continuous evaluation of the cell monolayer impedance upon exposure to physiological fluid shear stress forces. Bovine aortic endothelial cells grown to confluence on thin film go ld electrodes were exposed to fluid shear stress of 10 dynes/cm(2) for a si ngle uninterrupted 5 h time period or for two consecutive 30 min time perio ds separated by a 2 h no-flow interval. At the onset of flow, the monolayer electrical resistance sharply increased reaching 1.2 to 1.3 times the base line in about 15 min followed by a sustained decrease in resistance to 1.1 and 0.85 times the baseline value after 30 min and 5 h of flow, respectivel y. The capacitance decreased at the onset of flow, started to recover after 15 min and after slightly overshooting the baseline values, decreased agai n with a prolonged exposure to flow. Measured changes in capacitance were i n the order of 5% of the baseline values. The observed changes in endotheli al impedance were reversible upon flow removal with a recovery rate that va ried with the duration of the preceding flow exposure. These results demons trate that the impedance of endothelial monolayers changes dynamically with flow indicating morphological and/or functional changes in the cell layer. This in vitro model system (ECIS/Flow) may be a very useful tool in the qu antitative evaluation of flow-induced dynamic changes in cultured cells whe n used in conjunction with biological or biochemical assays able to determi ne the nature and mechanisms of the observed changes. (C) 2001 Biomedical E ngineering Society.