Integration and functionality of human iPSC-derived microglia in a chimeric mouse retinal model.

Area of Science:

• Neuroscience
• Immunology
• Stem Cell Biology

Background:

• Microglia are crucial for central nervous system homeostasis and neuroinflammation.
• Rodent models have limitations in accurately representing human microglia for retinal disease research.

Purpose of the Study:

• To develop a novel ex vivo chimeric model for studying human microglia in the retinal context.
• To overcome limitations of current animal models in human microglia research.

Main Methods:

• Elimination of endogenous mouse microglia using PLX5622.
• Transplantation of human induced pluripotent stem cell-derived microglia (hiPSC-microglia) into mouse retinal explants.
• Quantification of xenotransplanted microglia (xMG) integration and function (proliferation, phagocytosis).
• Transcriptomic analysis using single-cell RNA sequencing (scRNA-seq).

Main Results:

• Successful migration and integration of human microglia (xMG) into mouse retinal explants (>86% integration).
• xMG maintained homeostatic morphology and key functions including proliferation, immune response, and synaptic pruning over 14 days.
• scRNA-seq revealed an in vivo-like phenotype shift in xMG compared to monoculture hiPSC-microglia.
• xMG showed activation and migration towards degenerated photoreceptors in a retinal degeneration model.

Conclusions:

• The developed ex vivo model is a powerful platform for studying human microglia in retinal diseases.
• This model offers significant insights for advancing research and developing therapeutic strategies for retinal degenerative diseases.
• Future applications include using patient-derived iPSCs to investigate disease-specific microglial behaviors and pathogenesis.