Neuroimmune, neurochemical and behavioral studies in humanized heterozygous-IL-34 and wild-type NOG mice

Abstract Objective Humanized NOG mice are increasingly used to investigate neuroimmune disorders, but their baseline behavioral, neurochemical, and immunological characteristics remain poorly characterized. Methods We evaluated the effect of IL-34 mediated human microglial engraftment on peripheral immune T-cell reconstitution, brain metabolites, and behavior in humanized heterozygous HSC-NOG-IL-34 (HET) and wild-type HSC-NOG (WT) mice. Neonatal mice were engrafted with human CD34+ hematopoietic stem cells and assessed using flow cytometry, immunohistochemistry, proton magnetic resonance spectroscopy ( 1 H-MRS), and behavioral testing. Multivariable linear regression analysis was used to evaluate the effect of genotype, sex, age and their interactions. Results Peripheral human CD45 + , CD3 + , and CD4 + T-cell populations increased with age but did not differ by genotype. HET mice showed higher number of IBA1+ and HuNu+ cells in the brain than WT mice, indicating enhanced human microglial engraftment. 1 H-MRS metabolites did not differ by genotype, sex or age. Locomotor activity declined with age in both the groups. HET mice showed age-related reductions in exploration of novel and familiar objects, whereas WT mice showed increased exploration of familiar objects. The discrimination index remained unchanged in both the groups. HET mice also spent more time in the stranger zone and showed reduced investigation of the empty cup with age. In contrast, WT mice showed reduced time in the stranger zone. Conclusions HET mice showed greater human microglial engraftment and more pronounced age-related declines in exploratory behavior than WT mice. These findings support the utility of HSC-NOG-IL-34 mouse model for investigating neuroimmune disorders underlying behavioral dysfunction.