Measurement of Microvascular Endothelial Barrier Dysfunction and Hyperpermeability In Vitro

Loss of microvascular endothelial barrier integrity leads to vascular hyperpermeability and vasogenic edema in a variety of disease processes including trauma, ischemia and sepsis. Understanding these principles gives valuable information on pathophysiology and therapeutic drug development. While animal models of traumatic and ischemic injuries are useful to understand vascular dysfunctions associated with such injuries, in vitro barrier integrity assays are reliable and helpful adjuncts to understand the cellular and molecular changes and signaling mechanisms that regulate barrier function. We describe here the endothelial monolayer permeability assay and transendothelial electrical resistance (TEER) measurement as in vitro methods to test changes in microvascular integrity and permeability. These in vitro assays are based on either the measurement of electrical resistance of the monolayer or the quantitative evaluation of fluorescently tagged molecules (e.g., FITC-dextran) that pass through the monolayer when there is damage or breakdown.