Interleukin-4 restores neurogenic plasticity of the primary human neural stem cells through suppression of Kynurenic acid production upon Amyloid-beta42 toxicity

The immune response is an important determinant of the plasticity and neurogenic capacity of neural stem cells (NSCs) upon amyloid-beta42 (Aß42) toxicity in Alzheimer's disease (AD). However, the direct effects of individual immuno-modulatory effectors on NSC plasticity remain to be elucidated and are the motivation for reductionist tissue-mimetic culture experiments. Using starPEG-Heparin hydrogel system that provides a defined 3D cell-instructive neuro-microenvironment culture system, sustains high levels of proliferative and neurogenic activity of human NSCs, and recapitulates the fundamental pathological consequences of Amyloid toxicity upon Aß42 administration, we found that the anti-inflammatory cytokine interleukin-4 (IL4) restores the plasticity and neurogenic capacity of NSCs by suppressing the Aß42-induced kynurenic acid-producing enzyme kynurenine aminotransferase 2 (KAT2), which we also found to be upregulated in the brains of the AD model, APP/PS1dE9 mouse. Our transcriptome analyses showed that IL4 treatment restores the expression levels of NSC and cortical subtype markers. Thus, our dissective neuro-microenvironment culture revealed IL4-mediated neuroinflammatory crosstalk for human NSC plasticity and predicted a new mechanistic target for therapeutic intervention in AD. Primary (from Gestation week 21 of human fetus) and induced (adult human fibroblast-derived) neural stem cells are cultured in 2D and 3D. Next generation sequencing is performed at 3 weeks of culture. Overall design: pNSC neural stem cells are cultured in 3D. Next generation sequencing is performed at 3 weeks of culture. For 3D cultures, Abeta42 is mixed with heparin solution at the time the gels are prepared. Cultures are performed for three weeks with frequent media changes. DMSO, KYNA and IL4 were present in the culture medium throughout the culture at the following concentrations: IL4 (10 nM), KYNA (10 uM), DMSO (0.1%). Cultures are performed for three weeks with frequent media changes.