AMPA receptors and seizures mediate hippocampal radial glia‐like stem cell proliferation

Neurogenesis is sustained throughout life in the mammalian brain, supporting hippocampus‐dependent learning and memory. Its permanent alteration by status epilepticus (SE) is associated with learning and cognitive impairments. The mechanisms underlying the initiation of altered neurogenesis after SE are not understood. Glial fibrillary acidic protein‐positive radial glia (RG)‐like cells proliferate early after SE, but their proliferation dynamics and signaling are largely unclear. We have previously reported a polarized distribution of AMPA receptors (AMPARs) on RG‐like cells in vivo and postulated that these may signal their proliferation. Here, we examined the acute effects of kainate on hippocampal precursor cells in vitro and in kainate‐induced SE on proliferating and quiescent clones of 5‐bromo‐2‐deoxyuridine prelabeled hippocampal precursors in vivo. In vitro, we found that 5 μM kainate shortened the cell cycle time of RG‐like cells via AMPAR activation and accelerated cell cycle re‐entry of their progeny. It also shifted their fate choice expanding the population of RG‐like cells and reducing the population of downstream amplifying neural progenitors. Kainate enhanced the survival of all precursor cell subtypes. Pharmacologically, kainate's proliferative and survival effects were abolished by AMPAR blockade. Functional AMPAR expression was confirmed on RG‐like cells in vitro. In agreement with these observations, kainate/seizures enhanced the proliferation and expansion predominantly of constitutively cycling RG‐like cell clones in vivo. Our results identify AMPARs as key potential players in initiating the proliferation of dentate RG‐like cells and unravel a possible receptor target for modifying the radial glia‐like cell response to SE. Main Points AMPAR activation induces the proliferation, cell cycle re‐entry and expansion of hippocampal RG‐like stem cells in vitro and contributes to the expansion of precursor cell populations and subsequent neurogenesis after Status Epilepticus in vivo.