BACKGROUND:Folic acid is essential for normal functioning of the nervous system.Previous studies have focused on the effects of folic acid on astrocyte proliferation. OBJECTIVE:To explore the effects of folic acid on astrocyte differentiation of neural stem cells (NSCs) and the related mechanisms in vitro. DESIGN,TIME AND SETTING:A randomized,controlled,grouping experiment was performed in Tianjin Medical University between August 2007 and October 2008. MATERIALS:Folic acid and 5-bromo-2-deoxyuridine(BrdU) were obtained from Sigma,MO,USA. Primary antibodies[rabbit anti-rat nestin,β-tubulin-Ⅲ,glial fibrillary acidic protein,and neurogenin1 (Ngn1);mouse anti-rat BrdU andβ-actin monoclonal antibodies]were purchased from Santa Cruz Biotechnology,USA. METHODS:At 6 days of NSC proliferation from 24-hour-old neonatal rats,BrdU incorporation assay was performed.Seven days after primary culture,NSCs were induced to differentiate with medium containing 5%fetal bovine serum.Cultured NSCs were assigned to three groups:control,low-dose (liquid media with 8 mg/L folic acid),and high-dose folic acid(liquid media with 44 mg/L folic acid). MAIN OUTCOME MEASURES:At day 7 after primary culture,the cells were identified as NSCs by immunocytochemical methods.Double-label immunofluorescence technique for glial fibrillary acidic protein/BrdU detected differentiated cells 7 days after induction.Western blot was used to analyze expression of Ngn1 protein in NSCs. RESULTS:In serum-free suspension medium,neurospheres comprised a large number of Nestin-, glial fibrillary acidic protein-,β-tubulin-Ⅲ-,and BrdU-positive cells.Compared with the control group, high-dose folic acid supplementation led to an marked increase in the percentage of glial fibrillary acidic protein/BrdU-positive cells(P<0.05),and significantly decreased Ngn1 protein expression (P<0.05). CONCLUSION:Folic acid promotes astrocytic differentiation of NSCs,which might be related to downregulation of Ngn1 protein expression.
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