INDUCTION OF NEURONAL DIFFERENTIATION OF EMBRYONIC RAT CORTICAL NEUROSPHERES BY NERVE GROWTH FACTOR AND FETAL BOVINE SERUM ON THE NONADHERENT AND ADHERENT SUBSTRATES

Abstract

Regulating neural stem cells will greatly aid in developing regenerative medicine for the repair purpose of central nervous system (CNS). In this study, we explored the effect of nerve growth factor (NGF) on the differentiation of neural stem cells from embryonic rat cerebral cortex on nonadherent and adherent substrates at neurosphere level. The results showed that NGF could not promote adhesion and differentiation of neural stem cells when neurospheres were cultured on nonadherent tissue culture polystyrene (TCPS) substrates under serum-free condition. However, when 10% fetal bovine serum (FBS) was added to the culture system, FBS could induce the attachment of neurospheres onto an originally nonadherent substrate and almost all of the neurosphere-forming cells would migrate away from the spheres with the protoplasmic astrocyte morphology. Furthermore, when NGF was added into the FBS-containing medium, a significant number of differentiated neurons developed and distributed on the astrocyte layer. For comparison, adherent poly-D-lysine (PDL) substrates were also used. It was found that NGF could enhance differentiation of neural stem cells into neurons on PDL under serum-free condition but neurons and astrocytes could not migrate far away from the spheres. Similar to the TCPS results were also observed on PDL that differentiated neurons migrated out from the spheres and developed on the astrocyte layer when the medium contained NGF and FBS. Since the development of neurons needs glia cells to form a cellular substratum and to support neuronal migration to appropriate location, these results provide evidences that FBS-induced glia cells, serving as an architectural support layer, are essential for the growth and migration of NGF-induced neurons.