Intracrine Vascular Endothelial Growth Factor Maintains Hippocampal Neural Stem Cell Quiescence

In the dentate gyrus (DG) of the adult mouse hippocampus, neural stem cells (NSCs) balance self-renewal and differentiation to produce neurons that support hippocampal function. Vascular endothelial growth factor (VEGF) is a well-known supporting factor for adult neurogenesis, but conflicting studies have left it uncertain how VEGF signals to NSCs. Here, we identified a VEGF-VEGFR2 intracrine signaling mechanism within adult DG NSCs that prevents their exhaustion. We show both in vitro and in vivo that NSC-VEGF loss caused cell-autonomous exhaustion of adult DG NSCs. In contrast, extracellular VEGF was neither necessary nor sufficient to maintain NSC quiescence or to stimulate VEGFR2 signaling, most likely due to sheddase-mediated cleavage of extracellular VEGFR2 ligand binding domains. Our findings support an exclusively intracellular mechanism for VEGF signaling in adult DG NSCs, thereby providing resolution to previously conflicting studies and suggesting cellular source can dictate the functional impact of soluble ligands in DG NSCs. An in vivo model of conditional VEGF knockdown was used where adult NestinCreERT2;VEGFfloxed;ROSA-STOP-EYFP mice and VEGFWT controls were submitted to TAM administration to knockdown NSC-specific VEGF expression. 21 days after TAM administration DGs from 5 WT and 5 KO mice were harvested and submitted to fluorescently activated cell sorting for EYFP+ cells and then single cell sequencing on the 10x Genomics platform.