Depletion of neural stem cells from the subventricular zone of adult mouse brain using cytosine b‐Arabinofuranoside

INTRODUCTION Neural stem cells (NSCs) reside along the ventricular axis of the mammalian brain. They divide infrequently to maintain themselves and the down-stream progenitors. Due to the quiescent property of NSCs, attempts to deplete these cells using antimitotic agents such as cytosine b-Aarabinofuranoside (Ara-C) have not been successful. We hypothesized that implementing infusion gaps in Ara-C kill paradigms would recruit the quiescent NSCs and subsequently eliminate them from their niches in the subventricular zone (SVZ). METHODS We infused the right lateral ventricle of adult mice brain with 2% Ara-C using four different paradigms--1: one week; 2: two weeks; 3, 4: two weeks with an infusion gap of 6 and 12 h on day 7. Neurosphere assay (NSA), neural colony-forming cell assay (N-CFCA) and immunofluorescent staining were used to assess depletion of NSCs from the SVZ. RESULTS Neurosphere formation dramatically decreased in all paradigms immediately after Ara-C infusion. Reduction in neurosphere formation was more pronounced in the 3rd and 4th paradigms. Interestingly 1 week after Ara-C infusion, neurosphere formation recovered toward control values implying the presence of NSCs in the harvested SVZ tissue. Unexpectedly, N-CFCA in the 3rd paradigm, as one of the most effective paradigms, did not result in formation of NSC-derived colonies (colonies >2 mm) even from SVZs harvested 1 week after completion of Ara-C infusion. However, formation of big colonies with serial passaging capability, again confirmed the presence of NSCs. CONCLUSIONS Overall, these data suggest Ara-C kill paradigms with infusion gaps deplete NSCs in the SVZ more efficiently but the niches would repopulate even after the most vigorous kill paradigm used in this study.