Cell quality control. (A) Growth kinetics of a set of hNSCs lines showing the increasing, estimated overall cell number at each passage. (B) Clonal efficiency assay showing the percentage of cells that retain the ability to form clonal neurospheres over the total cell number plated is reported (Replicates n = 3), bars describe standard error. (C) hNSCs differentiate into astrocytes (left, green, GFAP), neurons (left, red, βIII-tubulin) and oligodendrocytes (right, GalC, red); nuclei are counterstained in blue (DAPI). (Bar = 50 μm). (D) All of the hNSCs lines tested undergo extinction in vitro upon growth factor removal, as shown by the negative growth kinetic in which the total cell number approaches zero in a few passages.