Strain‐specific differential expression of astrocytes and microglia in the mouse hippocampus

INTRODUCTION: Genetic background influences neurotransmitter expression and function of the hippocampus. Genetic background influences the phenotype of the hippocampus, but expression of neuroglia in hippocampus has not been well established dependent on various mouse strains. OBJECTIVES: In this study, we investigated the effects of genetic background on cell population of astrocytes and microglia in eight widely used inbred strains (C57BL/6J, A/J, BALB/c, C3H/HeJ, FVB, 129/SvJ, DBA/1, and DBA/2) and one outbred strain (ICR). METHODS: In all mouse strains, glial fibrillary acidic protein (GFAP)‐immunoreactive astrocytes and ionized calcium‐binding adaptor molecule 1 (Iba‐1)‐immunoreactive microglia were found in almost all layers of hippocampal CA1‐4 regions and the dentate gyrus. RESULTS: We observed significant differences in the number of astrocytes and microglia. In the CA1 and CA3 regions, the number of GFAP‐immunoreactive astrocytes was highest in the C3H/HeJ strain, and lowest in the 129/SvJ and FVB strains. In the polymorphic layer of the dentate gyrus, the number was highest in the DBA/1 strain and lowest in the 129/SvJ strain. Among the nine mouse strains, the number of Iba‐1‐immunoreactive microglia was highest in the CA1 and CA3 regions in the ICR and in the dentate gyrus of the C57BL/6 strain. The CA1 region of the FVB strain and the CA3 region and dentate gyrus of DBA/2 had the lowest number of Iba‐1‐immunoreactive microglia. CONCLUSION: These results suggest that the numbers of astrocytes and microglia differ depending on the mouse strain and these differences may be related to strain‐dependent function of astrocytes.