Abstract

Background
The lack of a brain-derived endothelial cell-based model has led researchers to exploit non-brain endothelial/epithelial cells as in vitro models for blood-brain barrier (BBB) investigations. Of these, the endothelial-like human ECV304 cell line was initially characterized as endothelial cells and has been widely used as an in vitro BBB model. It was later shown to be T24 bladder carcinoma epithelial cells. To pursue its potential as a cell-based model for drug screening and transport machineries, ECV304 cells were evaluated for their barrier and plasma membrane characteristics.
Material and Method
ECV304 cells treated with some tight-junction modulators (e.g. cAMP elevators, butyric acid, dexamethasone, gamma-linolenic acid, and astrocytic factors) were examined for bioelectrical resistance, transcellular/paracellular permeability, and functionality expression of some key transporters.
Results
A significant (p<0.05) increase in trans-endothelial electrical resistance (TEER) was observed in ECV304 cells treated with astrocytic factors and cAMP elevators (i.e. to approximately 110Omega*cm2 vs. approximately 60 Omega*cm2 in the control). Such treatment also yielded high discrimination in the permeability coefficients of the transcellular marker propranolol (25x10-6 cm/sec) and the paracellular marker sucrose (11.3 x 10-6 cm/sec). Carrier-mediated transporters such as GLUT-1, system L, and P-glycoprotein (P-gp) as well as endocytic transport machineries (e.g. clathrin and caveolin) were found to be functionally expressed.
Conclusions
ECV304 cells failed to generate a discriminative tight barrier even in the presence of tight-junction modulators. Thus their implementation in drug permeability screening is not recommended. They display some important key carrier-mediated transport systems and can be considered as a useful cell-based in vitro model.

Keywords: Models, Biological, Membrane Transport Proteins - metabolism, Gene Expression Regulation - physiology, Epithelial Cells - cytology, Electric Impedance, Dexamethasone, Cell Membrane Permeability - physiology, Butyric Acid, Blood-Brain Barrier - cytology, Tight Junctions - metabolism, gamma-Linolenic Acid