Characterization and use of human brain microvascular endothelial cells to examine β-amyloid exchange in the blood-brain barrier

Alzheimer's disease (AD) is characterized by excessive cerebrovascular deposition of the beta-amyloid peptide (A beta). The investigation of A beta transport across the blood-brain barrier (BBB) has been hindered by inherent limitations in the cellular systems currently used to model the BBB, such as insufficient barrier properties and poor reproducibility. In addition, many of the existing models are not of human or brain origin and are often arduous to establish and maintain. Thus, we characterized an in vitro model of the BBB employing human brain microvascular endothelial cells (HBMEC) and evaluated its utility to investigate A beta exchange at the blood-brain interface. Our HBMEC model offers an ease of culture compared with primary isolated or coculture BBB models and is more representative of the human brain endothelium than many of the cell lines currently used to study the BBB. In our studies, the HBMEC model exhibited barrier properties comparable to existing BBB models as evidenced by the restricted permeability of a known paracellular marker. In addition, using a simple and rapid fluormetric assay, we showed that antagonism of key A beta transport proteins significantly altered the bi-directional transcytosis of fluorescein-A beta (1-42) across the HBMEC model. Moreover, the magnitude of these effects was consistent with reports in the literature using the same ligands in existing in vitro models of the BBB. These studies establish the HBMEC as a representative in vitro model of the BBB and offer a rapid fluorometric method of assessing A beta exchange between the periphery and the brain.