Rapid and Efficient Induction of Functional Astrocytes from Human Pluripotent Stem Cells

Assessing Gq-GPCR-induced human astrocyte reactivity using bioengineered neural organoids

Astrocyte reactivity can directly modulate nervous system function and immune responses during disease and injury. However, the consequence of human astrocyte reactivity in response to specific contexts and within neural networks is obscure. Here, we devised a straightforward bioengineered neural organoid culture approach entailing transcription factor-driven direct differentiation of neurons and astrocytes from human pluripotent stem cells combined with genetically encoded tools for dual cell-selective activation. This strategy revealed that Gq-GPCR activation via chemogenetics in astrocytes promotes a rise in intracellular calcium followed by induction of immediate early genes and thrombospondin 1. However, astrocytes also undergo NF-κB nuclear translocation and secretion of inflammatory proteins, correlating with a decreased evoked firing rate of cocultured optogenetic neurons in suboptimal conditions, without overt neurotoxicity. Altogether, this study clarifies the intrinsic reactivity of human astrocytes in response to targeting GPCRs and delivers a bioengineered approach for organoid-based disease modeling and preclinical drug testing.

Mapping Astrocyte Transcriptional Signatures in Response to Neuroactive Compounds

Astrocytes play central roles in normal brain function and are critical components of synaptic networks that oversee behavioral outputs. Despite their close affiliation with neurons, how neuronal-derived signals influence astrocyte function at the gene expression level remains poorly characterized, largely due to difficulties associated with dissecting neuron- versus astrocyte-specific effects. Here, we use an in vitro system of stem cell-derived astrocytes to identify gene expression profiles in astrocytes that are influenced by neurons and regulate astrocyte development. Furthermore, we show that neurotransmitters and neuromodulators induce distinct transcriptomic and chromatin accessibility changes in astrocytes that are unique to each of these neuroactive compounds. These findings are highlighted by the observation that noradrenaline has a more profound effect on transcriptional profiles of astrocytes compared to glutamate, gamma-aminobutyric acid (GABA), acetylcholine, and serotonin. This is demonstrated through enhanced noradrenaline-induced transcriptomic and chromatin accessibility changes in vitro and through enhanced calcium signaling in vivo. Taken together, our study reveals distinct transcriptomic and chromatin architecture signatures in astrocytes in response to neuronal-derived neuroactive compounds. Since astrocyte function is affected in all neurological disorders, this study provides a new entry point for exploring genetic mechanisms of astrocyte-neuron communication that may be dysregulated in disease.

Rapid and efficient induction of functional astrocytes from human pluripotent stem cells

The derivation of astrocytes from human pluripotent stem cells is currently slow and inefficient. We demonstrate that overexpression of the transcription factors SOX9 and NFIB in human pluripotent stem cells rapidly and efficiently yields homogeneous populations of induced astrocytes. In our study these cells exhibited molecular and functional properties resembling those of adult human astrocytes and were deemed suitable for disease modeling. Our method provides new possibilities for the study of human astrocytes in health and disease.