ENGINEERING A MULTICELLULAR NEUROIMMUNE COMPETENT HUMAN BRAIN ORGANOID MODEL FOR ALZHEIMER’S DISEASE

Alzheimer’s disease (AD) is neuropathologically characterized by amyloid-beta (Aβ) plaques and neurofibrillary tangles. AD occurs as familial or sporadic (genetic and environmental factors). Increasing evidence highlights microglia as key mediators in AD pathogenesis, with human-specific factors crucial for modeling the disease spectrum, emphasizing the need for improved human models. Here, we optimized a protocol to derive human microglia from pluripotent stem cells (hPSC) through exposure of primitive macrophage precursors (PMPs) to an IGMT cytokine cocktail (IL34, GM-CSF, M-CSF, and TGFβ1) that results in a population with enriched microglial-specific gene expression and typical microglia ramified morphology. In contrast, classical cultures using FBS showed endothelial-like contamination. Transcriptomic analysis revealed upregulated microglial gene signatures, enhanced cytokine response, cytoskeletal reorganization, and extracellular matrix remodeling. Compared to PMPs and H9 hPSCs, IGMT microglia displayed a canonical microglial transcriptome.
Upon exposure to Aβ fibrils, microglia showed higher motility, rapid recruitment, aggregation, and efficient phagocytosis. Transcriptomic profile of Aβ-treated microglia revealed enriched pathways associated with AD, as well as Interferon response, TNF-alfa signaling and mitochondrial-associated pathways. However, phagocytosis capacity, cytoskeleton and extracellular matrix-associated pathways were downregulated, suggesting a state of progressive microglial dysfunction.
We established a human multicellular brain organoid (hmBOs) model that incorporates microglia. Optimal integration and survival was achieved by a combination of PMPs and IGMT cytokines, which led to high neuronal viability and microglial densities comparable to the in vivo cortex.
In conclusion, we developed neuroimmune-competent hmBOs that could serve to study neurodegenerative disorders characterized by an important immune component, such as AD