The expression of keratan sulfate reveals a unique subset of microglia in the mouse hippocampus after pilocarpine-induced status epileptics.
J Comp Neurol 2019;
528:14-31. [PMID:
31237692 DOI:
10.1002/cne.24734]
[Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 06/03/2019] [Accepted: 06/18/2019] [Indexed: 12/22/2022]
Abstract
Induction of keratan sulfate in microglia has been found in several animal models of neurological disorders. However, the significance of keratan sulfate-expressing microglia is not fully understood. To address this issue, we analyzed the characteristics of microglia labeled by the 5D4 epitope, a marker of high-sulfated keratan sulfate, in the mouse hippocampus during the latent period after pilocarpine-induced status epilepticus (SE). Only 5D4-negative (5D4- ) microglia were found in the CA1 region of vehicle-treated controls and pilocarpine-treated mice at 1 day after SE onset. A few 5D4+ microglia appeared in the strata oriens and radiatum at 5 days post-SE, and they were distributed into the stratum pyramidale at 14 days post-SE. The expressions of genes related to both anti- and pro-inflammatory cytokines were higher in 5D4+ cells than in 5D4- cells at 5 but not 14 days post-SE. The expressions of genes related to phagocytosis were higher in 5D4+ cells than in 5D4- cells throughout the latent period. The phagocytic activity of microglia, as measured by engulfment of the zymosan bioparticles, was higher in 5D4+ cells than in 5D4- cells. The contact ratios between excitatory synaptic boutons and microglia were also higher in 5D4+ cells than in 5D4- cells at 5 and 14 days post-SE. The excitatory/inhibitory ratios of synaptic boutons within the microglial domain were lower in 5D4+ cells than in 5D4- cells at 14 days post-SE. Our findings indicate that 5D4+ microglia may play some role in epileptogenesis via pruning of excitatory synapses during the latent period after SE.
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