Porcine choroid plexus epithelial cells in culture: Regulation of barrier properties and transport processes

The epithelial cells of the choroid plexus are the structural basis of the blood-cerebrospinal fluid (CSF)-barrier. Here we summarise our recent effor ts to culture those cells mainly on permeable supports in vitro. Isolated f rom porcine brains, we report a simple protocol for the primary culture usi ng cytosine arabinoside as an additive that is cytotoxic for other cells ex cept the plexus epithelial cells. Enhanced barrier properties are obtained by withdrawal of serum from the culture medium after confluency is reached. Cells improve their polarity, permeability for hydrophilic substrates is l owered, electrical resistance is increased tenfold, and a pH-gradient is bu ilt up across the eel monolayer. Polarised secretion of proteins and most i mportantly fluid secretion into the apical filter compartment was attained and proven to be dependent on the Na+,K+-ATPase activity. Active transport processes (penicillin G, riboflavin, myo-inositol, ascorbic acid) were stud ied and clearly showed the involvement of the organic anion transporter. Th e permeability of the barrier was found to be regulated by cyclic adenosine monophosphate (cAMP). Moreover, we report that cell proliferation and diff erentiation is controlled by components of the extracellular matrix. The pr esent culture model could now be used as an in vitro system to quantify dru g transport across the blood-CSF-barrier. (C) 2001 Wiley-Liss, Inc.