Conditioned medium of the primary culture of rat choroid plexus epithelial (modified ependymal) cells enhances neurite outgrowth and survival of hippocampal neurons

The choroid plexus epithelial (modified ependymal) cells (CPECs) are specialized for cerebrospinal fluid (CSF) production and serve as blood-CSF barrier. It is suggested that, in addition to CSF production, the CPECs may regulate CNS function through expression of secretory factors into CSF. There have been reports that the CPECs express various types of factors including growth factors. However, the actual effects of the molecules produced and secreted from the CPECs on the central nervous system (CNS) are virtually unknown both in vivo and in vitro. With the use of pure culture of CPECs, we demonstrated that the conditioned medium (CM) from CPECs can enhance neurite outgrowth and survival of cultured neurons derived from rat hippocampus on postnatal day 1 in 24-h cultures. The effect of the CM was retained in fractions that contains complex of molecules larger than 50 kDa in native condition with ultrafiltration method and disappeared by trypsin digestion. The results of the present study indicate that CPECs can support the survival and function of neurons in vitro by secreting factors that are likely to be of peptide/protein nature rather than small chemicals.