A stolen future – aberrant hippocampal neurogenesis produces glial cells in epilepsy

Adult hippocampal neurogenesis is disturbed in epilepsy. The increased neuronal activity in the epileptic brain leads to an increased production of newborn cells, increased mossy fibre sprouting and altered integration of new neurons within the hippocampus. Here, we set out to investigate increased astrocyte numbers following status epilepticus. We used immunolabelling of brain sections from the mouse intra-amygdala kainic acid model of epilepsy and publicly available single cell RNA sequencing datasets to assess newborn cells in the dentate gyrus. Similar to published series we found on increased number of reactive astrocytes present in the epileptic hippocampus. Additionally, we identified a cell population that expressed neurogenesis (doublecortin) and astrocyte (glial fibrillary acidic protein) markers in the epileptic brain, both in mouse and in human tissue. We further evaluated the expression profile of these cells. Immunolabelling showed expression of mature astrocyte markers aquaporin 4 and glutamate transporter-1. The single cell RNA sequencing data highlighted expression of neurogenesis and astrocyte markers in the doublecortin/glial fibrillary acidic protein-expressing cells. In conclusion, epilepsy pushes early neuroblasts to fate-switch to an astrocyte lineage as seen in the kainic acid-induced mouse model and in human resected brain tissue. Further understanding how neurogenesis is altered in epilepsy and whether the neuroblast fate-switch can be reverted will help in finding novel therapy strategies for epilepsy and other neurological diseases associated with aberrant adult hippocampal neurogenesis.