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Updated: Aug 10, 2026
Generation of Retinal Organoids from Healthy and Retinal Disease-Specific Human-Induced Pluripotent Stem Cells
Published on: December 9, 2022
Integrating human iPSC-derived macrophage progenitors into retinal organoids to generate a mature retinal microglial
Ayumi Usui-Ouchi1,2, Sarah Giles1,3, Sarah Harkins-Perry1,3
1Department of Molecular Medicine, The Scripps Research Institute, La Jolla, California, USA.
Abstract:
In the retina, microglia are resident immune cells that are essential for development and function. Retinal microglia play a central role in mediating pathological degeneration in diseases such as glaucoma, retinitis pigmentosa, age-related neurodegeneration, ischemic retinopathy, and diabetic retinopathy. Current models of mature human retinal organoids (ROs) derived from iPS cell (hiPSC) do not contain resident microglia integrated into retinal layers. Increasing cellular diversity in ROs by including resident microglia would more accurately represent the native retina and better model diseases in which microglia play a key role. In this study, we develop a new 3D in vitro tissue model of microglia-containing retinal organoids by co-culturing ROs and hiPSC-derived macrophage precursor cells (MPCs). We optimized the parameters for successful integration of MPCs into retinal organoids. We show that while in the ROs, MPCs migrate to the equivalent of the outer plexiform layer where retinal microglia cells reside in healthy retinal tissue. While there, they develop a mature morphology characterized by small cell bodies and long branching processes which is only observed in vivo. During this maturation process these MPCs cycle through an activated phase followed by a stable mature microglial phase as seen by the down regulation of pro-inflammatory cytokines and upregulation of anti-inflammatory cytokines. Finally, we characterized mature ROs with integrated MPCs using RNAseq showing an enrichment of cell-type specific microglia markers. We propose that this co-culture system may be useful for understanding the pathogenesis of retinal diseases involving retinal microglia and for drug discovery directly in human tissue.
Insights
Researchers developed a novel 3D model of human retinal organoids containing microglia. This advanced model accurately represents the retina for studying diseases and discovering new drugs.
Area of Science:
- Ophthalmology
- Immunology
- Stem Cell Biology
Background:
- Microglia are crucial retinal immune cells involved in development and disease pathology.
- Current human retinal organoids lack resident microglia, limiting their disease modeling capabilities.
- Integrating microglia is essential for accurately modeling retinal diseases like glaucoma and diabetic retinopathy.
Purpose of the Study:
- To develop a 3D in vitro model of human retinal organoids with integrated microglia.
- To optimize co-culture conditions for macrophage precursor cell integration into retinal organoids.
- To characterize the behavior and maturation of integrated microglia within the organoid model.
Main Methods:
- Co-culturing human induced pluripotent stem cell-derived retinal organoids (ROs) with hiPSC-derived macrophage precursor cells (MPCs).
- Optimizing co-culture parameters for successful MPC integration and migration.
- Utilizing RNA sequencing (RNAseq) to characterize the integrated cells and their markers.
Main Results:
- MPCs successfully integrated into ROs, migrating to the outer plexiform layer, mimicking native retinal microglia location.
- Integrated cells adopted mature microglial morphology with small cell bodies and branching processes.
- Maturation involved a transition from an activated to a stable microglial phase, indicated by cytokine expression changes.
- RNAseq confirmed enrichment of cell-type specific microglia markers in the integrated cells.
Conclusions:
- The developed co-culture system successfully generates microglia-containing human retinal organoids.
- This model provides a more accurate representation of the native retina for studying microglial roles in disease.
- The model holds potential for advancing research into retinal diseases and facilitating drug discovery.
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