“…As a matter of fact, the various protocols for the generation of iNSCs give rise to distinct iNSC populations that slightly differ in self renewal capacity, marker expression, and regional identity, as well as in vitro and in vivo differentiation potential. While Kim et al [11] reported passage of their mouse iNSCs for 3-5 times only, more recent studies demonstrated maintenance of NSC characteristics for more than 30 passages [13,14,28,34,36,38,58,73]. In order to demonstrate selfrenewal potential and clonal growth ability, iNSCs were either cultivated as primary and secondary neurospheres [33,34], analyzed in colony formation assays [28,33,36,39,42,48,72], and/or passaged several times [11,13,14,26,30,32,33,38,57,59,60,73].…”