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.