Cardozo, P. L. | bioRxiv Science

bioRxiv2024

hiPSC-derived astrocytes from individuals with schizophrenia promote alterations in phagocytosis and chemotaxis of microglial-like cells

Neuroinflammation, particularly astrocyte reactivity, is increasingly linked to schizophrenia (SCZ). Yet, the crosstalk between astrocytes and microglia in SCZ, especially under pro-inflammatory conditions, remains unclear. Here, we employed human induced-pluripotent stem cells to compare how astrocytes from five age-matched individuals with SCZ and five neurotypical controls, upon stimulation with TNF-, affected microglial biology. TNF-[a] stimulation of SCZ astrocytes, relative to their control counterparts, triggered increased mRNA expression of pro-inflammatory cytokines and CX3CL1. Interestingly, transcriptomic and gene set enrichment analyses revealed that reactive SCZ astrocytes promoted the downregulation of biological processes associated with immune cell proliferation and activation, phagocytosis and cell migration in induced microglial-like cells (iMGs). Under such conditions, iMGs assumed a dystrophic/senescent-like phenotype, which was associated with accelerated transcriptional aging. Functional validations showed that TNF-[a]-stimulated SCZ astrocytes promoted reduced synaptoneurosomes phagocytosis by iMGs. Interestingly, only reactive control astrocytes were capable to induce significant microglial migration in a CX3CR1-dependent manner, despite the greater CX3CL1 secretion by reactive SCZ astrocytes compared to their stimulated control counterparts. This was likely due to SCZ astrocytes triggered reduction in CX3CR1 plasma membrane levels in iMGs. Altogether, these findings suggest that astrocytes contribute to SCZ pathology by altering normal microglial function and inducing a dystrophic phenotype. Main pointsO_LISCZ astrocytes display an increased pro-inflammatory profile upon stimulation with TNF-. C_LIO_LIReactive SCZ astrocytes induce microglial-like cells to assume a dystrophic phenotype. C_LIO_LIReactive SCZ astrocytes secreted factors impair microglial-like cells synaptoneurosome phagocytosis and limit their migration. C_LI

neuroscience↗

bioRxiv2022

Spatial proteomics and iPSC modeling uncover mechanisms of axonal pathology in Alzheimer's disease

Axonal spheroids (dystrophic neurites) are commonly found around amyloid deposits in Alzheimers disease (AD). They impair electrical conduction, disrupt neural circuits, and correlate with AD severity. Despite their significance, the mechanisms underlying spheroid formation remain unknown. To address this, we developed a proximity labeling proteomics approach to uncover the proteome of spheroids in human postmortem and mouse brains. Additionally, we established a human iPSC-derived AD model allowing mechanistic investigation of spheroid pathology and optical electrophysiology. This approach revealed the subcellular molecular architecture of spheroids and identified abnormalities in key biological processes, including protein turnover, cytoskeleton dynamics, and lipid transport. Notably, the PI3K/AKT/mTOR pathway, which regulates these processes, was activated within spheroids. Furthermore, phosphorylated mTOR levels in spheroids strongly correlated with AD severity in humans. Importantly, inhibition of mTOR in iPSC-derived neurons and in mice ameliorated spheroid pathology. Altogether, our study provides a multidisciplinary toolkit for investigating mechanisms and novel targets for axonal pathology in neurodegeneration.

neuroscience↗