Adult and embryonic DRG NSCs were maintained under proliferating conditions in vitro for 4–5 years following procurement. Screening with EGF and bFGF allowed for isolation of NSCs, which aggregated to form neurospheres—spherical clusters of NSCs. The gross morphology in the phase contrast image of eDRG-NSCs (Fig. 1A) and aDRG NSCs (Fig. 1B) appeared similar, occurring as clustered as neurospheres (arrow), as shown nearly 3 weeks after procurement, or existing as individual cells. The trophic factor responsiveness, of 4–5 years' nondissociated aDRG NSCs, to EGF, bFGF, or a cocktail of EGF + bFGF was indicated by the continued formation of neurospheres (Fig. 1C). Significant differences in the number of neurospheres over time as well as day × treatment interactions (p < 0.05) were demonstrated. The neurosphere formation of eDRG and aDRG NSCs were similar despite the age difference of the animals at the start of NSC isolation.
