To investigate the effect of the γ-secretase inhibitor N-[N-(3, 5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester (DAPT) on the transforming growth factor-β1 (TGF-β1)-induced differentiation of neural stem cells (NSCs) and Notch signaling.

Primary cultured NSCs were obtained from rat forebrain tissue. NSCs were divided stochastically into a control group (treated with vehicle only), a TGF-β1 group (treated with TGF-β1 at 5 ng/L), and a DAPT group (treated with TGF-β1 at 5 ng/L plus DAPT at 1 or 10 μmol/L). After culture for 3, 8, 24, and 48 h, the mRNA expression of Notch1 and Jagged1 was quantified by real-time RT-PCR. The protein expression of the astrocyte marker glial fibrillary acidic protein (GFAP) and the NSC marker Nestin was determined by Western blot. The expression and location of Notch1, Jagged1, GFAP, and Nestin in NSCs were detected by immunofluorescence staining.

After TGF-β1 treatment, the differentiation of NSCs was accelerated. At the early stage, Nestin was not expressed in NSCs. After 8 h, GFAP began to be expressed and increased with time. Conversely, Nestin was expressed in NSCs at the early stage, but it was down-regulated after 8 h, suggesting that TGF-β1 can induce the transformation of NSCs into astrocytes after 8 h. Further studies showed that the expression of Notch1 and Jagged1 was increased gradually after TGF-β1 treatment for 8 h, suggesting that TGF-β1 mediated the activation of Notch signaling during astrocyte transformation. After treatment with DAPT, GFAP expression was not inhibited at 8 h, but decreased gradually after 48 h, accompanied by down-regulation of Notch1 and Jagged1, suggesting that the transformation of NSCs to astrocytes was inhibited after DAPT treatment. The mechanism may be associated with the decrease in Notch signaling activity.

TGF-β1 induces the transformation of NSCs into astrocytes in a time-dependent manner; its mechanism may be related to the activation of Notch signaling. Intervention with DAPT blocks Notch signaling, which inhibits TGF-β1-mediated differentiation of NSCs into astrocytes at a certain time point.