Microglia integration into human midbrain organoids leads to increased neuronal maturation and functionality

Abstract

The human brain is a complex, three‐dimensional structure. To better recapitulate brain complexity, recent efforts have focused on the development of human‐specific midbrain organoids. Human iPSC‐derived midbrain organoids consist of differentiated and functional neurons, which contain active synapses, as well as astrocytes and oligodendrocytes. However, the absence of microglia, with their ability to remodel neuronal networks and phagocytose apoptotic cells and debris, represents a major disadvantage for the current midbrain organoid systems. Additionally, neuroinflammation‐related disease modeling is not possible in the absence of microglia. So far, no studies about the effects of human iPSC‐derived microglia on midbrain organoid neural cells have been published. Here we describe an approach to derive microglia from human iPSCs and integrate them into iPSC‐derived midbrain organoids. Using single nuclear RNA Sequencing, we provide a detailed characterization of microglia in midbrain organoids as well as the influence of their presence on the other cells of the organoids. Furthermore, we describe the effects that microglia have on cell death and oxidative stress‐related gene expression. Finally, we show that microglia in midbrain organoids affect synaptic remodeling and increase neuronal excitability. Altogether, we show a more suitable system to further investigate brain development, as well as neurodegenerative diseases and neuroinflammation.

Evidence for Oxidative Pathways in the Pathogenesis of PD: Are Antioxidants Candidate Drugs to Ameliorate Disease Progression?

“…Interestingly, the recent development of novel cellular models such as human-brain based organoids [217,218] and patient-derived pluripotent stem cells [219] may provide additional experimental models that have greater translation capacity for therapeutic development [220] than the models described above. For example, microglia integration with human-brain based organoids is demonstrated to enhance neuronal maturation and functionality in these three-dimensional structures [221] and may provide a superior experimental model to test drug/antioxidant efficacy, although to date no data has been made available for evaluation. Overall, further clinical trials are necessary to further elucidate the therapeutic potential of antioxidants.…”

Human cerebral organoids — a new tool for clinical neurology research

“…Consequently, these cells are rare in standard protocols. They can form spontaneously in organoids 246 , although controlled mixing procedures provide greater control over the ratio of cell types 237 , 247 – 249 . Methods for generating holistic 3D cultures that have the same high throughput as traditional methods are required to build more precise models and to study processes such as demyelination and neuroinflammation.…”

Cerebral Organoids as an Experimental Platform for Human Neurogenomics

“…For example, microglia are the tissue-resident macrophages of the brain that arise in the yolk sac and are involved in innate immune and homeostatic functions [ 106 ]. Incorporation of microglia into organoids via transplantation or induction of the PU.1 transcription factor expression in a subset of organoid cells [ 107 , 108 , 109 , 110 ] ( Figure 1 d) has been shown to attenuate DNA damage responses in organoids and to promote the maturation of neuronal activity.…”