Dynamic alteration of dendrites and dendritic spines in the hippocampus and microglia in mouse brain tissues after kainate-induced status epilepticus

Abstract

Purpose To study the alteration of microglial subtypes, the representative markers of microglia, and the morphology of dendrites and dendritic spines after acute status epilepticus (SE) and during recurrent seizures. Methods A mouse kainate-induced SE model was used. Dendrites and dendritic spines of granule neurons in the dentate gyrus (DG) subregion and pyramidal neurons in the cornu ammonis (CA)1 and cornu ammonis (CA)3 subregions of the hippocampus were visualized by Golgi staining. Synaptic proteins were evaluated by Western blot analysis, and microglia and their markers were evaluated by flow cytometry. Results Extensive partial spine loss was observed in the dendrites of granule and pyramidal cells in the acute and early chronic stages of SE. In terms of spine loss, the thin and mushroom types predominated. Accompanying the spine loss in these two stages, the proportion of M1 microglia increased significantly with high CX3CR1 expression and low CD200R expression. However, at the transiting stage, the proportion of M2 microglia was increased dramatically, and high expression levels of CXCR3 on all microglia and CD68 on M1 microglia were observed. Morris water maze tests revealed significant learning and memory impairment in the chronic phase of epilepsy. Conclusion Dendritic spines in the hippocampus and microglia in the central nevus system are dynamically altered in epilepsy during the establishment and maintenance of spontaneous seizures. Microglia may contribute to the spine loss and related learning and memory impairment.