title: Pitfalls in assessing microvascular endothelial barrier function: impedance-based devices versus the classic macromolecular tracer assay.
abstract: The most frequently used parameters to describe the barrier properties of endothelial cells (ECs) in vitro are (i) the macromolecular permeability, indicating the flux of a macromolecular tracer across the endothelium, and (ii) electrical impedance of ECs grown on gold-film electrodes reporting on the cell layer's tightness for ion flow. Due to the experimental differences between these approaches, inconsistent observations have been described. Here, we present the first direct comparison of these assays applied to one single cell type (human microvascular ECs) under the same experimental conditions. The impact of different pharmacological tools (histamine, forskolin, Y-27632, blebbistatin, TRAP) on endothelial barrier function was analyzed by Transwell(®) tracer assays and two commercial impedance devices (xCELLigence(®), ECIS(®)). The two impedance techniques provided very similar results for all compounds, whereas macromolecular permeability readings were found to be partly inconsistent with impedance. Possible reasons for these discrepancies are discussed. We conclude that the complementary combination of both approaches is highly recommended to overcome the restrictions of each assay. Since the nature of the growth support may contribute to the observed differences, structure-function relationships should be based on cells that are consistently grown on either permeable or impermeable growth supports in all experiments.
authors.affiliation: Institute of Pharmaceutical Biology, Biocenter, Goethe University Frankfurt/Main, Germany.
authors.forename: Iris
authors.initials: I
authors.lastname: Bischoff
authors.affiliation: Pharmaceutical Biology, Department of Pharmacy, Center for Drug Research, University of Munich, Germany.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Hornburger
authors.affiliation: Pharmaceutical Biology, Department of Pharmacy, Center for Drug Research, University of Munich, Germany.
authors.forename: Bettina A
authors.initials: BA
authors.lastname: Mayer
authors.affiliation: Institute of Pharmaceutical Biology, Biocenter, Goethe University Frankfurt/Main, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Beyerle
authors.affiliation: Institute of Analytical Chemistry, Chemo- and Biosensing, University of Regensburg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Wegener
authors.affiliation: Institute of Pharmaceutical Biology, Biocenter, Goethe University Frankfurt/Main, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Fürst
mesh_terms: D000577:Amides / Q000494:pharmacology; D001681:Biological Assay; D002199:Capillary Permeability / Q000187:drug effects*; D002478:Cells, Cultured; D017097:Electric Impedance; D042783:Endothelial Cells / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D011725:Pyridines / Q000494:pharmacology
chemical_list: D000577:Amides; D011725:Pyridines; C108830:Y 27632; D006632:Histamine