Induced Neural Stem Cells Protect Neuronal Cells against Apoptosis

BACKGROUND Neuronal cells are vulnerable to many stresses that can cause apoptosis. Reprogramming of fibroblasts into induced neural stem cells (iNSCs) is a potentially unlimited source of neurons. Discovering agents that can provide neuronal protection against these apoptotic stimuli is important for developing therapeutic strategies for various brain diseases. MATERIAL AND METHODS We investigated the therapeutic effects of iNSCs against apoptosis activator II (AAII)-induced apoptosis of cortical neuronal cells. Apoptosis was confirmed by double immunocytochemistry with NeuN and 4',6-diamidino-2-phenylindole using terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP-biotin nick-end labeling. We performed Western blot analyses for activated caspase-3, Bcl-2, phosphorylated Akt, and phosphorylated extracellular signal-regulated protein kinase (ERK). The level of vascular endothelial growth factor (VEGF) was analyzed using enzyme-linked immunosorbent assays (P<0.05). RESULTS Cortical neuronal cells cultured with iNSCs had fewer apoptotic cells than those cultured without iNSCs. We found that cells cultured with iNSCs had a significantly lower caspase-3 level and a significantly higher Bcl-2 level than cells cultured without iNSCs. Cells cultured with iNSCs had higher VEGF levels than cells cultured without iNSCs. The levels of phosphorylated Akt and phosphorylated ERK were significantly higher in cells cultured with iNSCs than in cells cultured without iNSCs. CONCLUSIONS Our findings suggest that iNSCs activate Akt and ERK, which are associated with the inhibition of neuronal apoptosis. Thus, treatment with iNSCs may help reduce neuronal loss in brain disease. Further studies aimed at proving this hypothesis might help establish therapeutic agents that can prevent neuronal cell death and help cure neurodegenerative diseases.