A. Hakvoort et al., THE POLARITY OF CHOROID-PLEXUS EPITHELIAL-CELLS IN-VITRO IS IMPROVED IN SERUM-FREE MEDIUM, Journal of neurochemistry, 71(3), 1998, pp. 1141-1150
The influence of culture conditions on the development of normal chara
cteristics of the choroid plexus epithelium has been investigated in v
itro with respect to polarity, barrier properties, transport, and secr
etory activity. Withdrawal of serum supplement in the culture medium o
f cells grown on filters caused morphologically visible changes by an
increased trimming of microvilli at the apical membrane side, which is
accompanied by an increased expression of the Na+, K+-ATPase. Moreove
r cells under serum-free conditions exhibit structural changes in ligh
t junctional zonula occludens protein-1 (ZO-1) organization, a reduced
permeability, and a drastically increased electrical resistance from
150 Omega.cm(2) in the presence of serum to 1,500 Omega.cm(2) after se
rum withdrawal. Under these conditions, cell monolayers are able to bu
ild up a transcellular proton gradient and to secrete fluid into the u
pper (apical) filter compartment, which is accompanied by a polarized
secretion of proteins like transthyretin. Active transport of the dyes
fluorescein and phenol red by the organic anion transporter is found
to be driven by the Na+, K+-ATPase. We come to the conclusion that rem
oval of serum favors the differentiation process of the plexus epithel
ium in vitro, which brings the cell culture model closer to the physio
logical situation in vivo. We present preliminary evidence that epider
mal growth factor may be one component in serum preventing the proper
in vitro differentiation.