This study utilized DRG NSCs from embryonic day (E) 14–16 and adult rats that were previously established in our laboratory. In brief, DRGs were dissected and removed from adult or pregnant (at gestation 14–16 days) Sprague-Dawley rats (Harlan-Sprague Dawley, Inc., Indianapolis, IN) under deep anesthesia. DRG were washed twice in sterile phosphate buffer before being transferred to Hank's balanced salt solution (HBSS) for further dissection of DRG cells. DRG NSCs were isolated and screened using 10 ng/ml of epidermal growth factor (EGF, Harlan Bioproducts for Science, Indianapolis, IN) and basic fibroblast growth factor (bFGF, Pepro-Tech, Rocky Hill, NJ) in Dulbecco's modified Eagle medium/F-12 Nutrient Mix (DMEM/F-12) media containing N2 supplement (12 μl/ml, Invitrogen, Carlsbad, CA), and penicillin-streptomycin (12 μl/ml, Sigma, St. Louis, MO) and grown in a humidified incubator at 37°C and 5% CO2. The neurospheres were formed within 72 h and were characterized for their neural stem cell capacity with nestin and BrdU staining every 3–6 months. The long-term DRG NSC cultures were maintained in the above-mentioned medium in the presence of EGF and basic fibroblast growth factor (bFGF)
