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There is significant need to develop physiologically relevant models for investigating human astrocytes in health and disease. Here, we present an approach for generating astrocyte lineage cells in a three-dimensional (3D) cytoarchitecture using human cerebral cortical spheroids (hCSs) derived from pluripotent stem cells. We acutely purified astrocyte-lineage cells from hCSs at varying stages up to 20 months in vitro using immunopanning and cell sorting and performed high-depth bulk and single-cell RNA sequencing to directly compare them to purified primary human brain cells. We found that hCS-derived glia closely resemble primary human fetal astrocytes and that, over time in vitro, they transition from a predominantly fetal to an increasingly mature astrocyte state. Transcriptional changes in astrocytes are accompanied by alterations in phagocytic capacity and effects on neuronal calcium signaling. These findings suggest that hCS-derived astrocytes closely resemble primary human astrocytes and can be used for studying development and modeling disease., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The human cerebral cortex develops through an elaborate succession of cellular events that, when disrupted, can lead to neuropsychiatric disease. The ability to reprogram somatic cells into pluripotent cells that can be differentiated in vitro provides a unique opportunity to study normal and abnormal corticogenesis. Here, we present a simple and reproducible 3D culture approach for generating a laminated cerebral cortex-like structure, named human cortical spheroids (hCSs), from pluripotent stem cells. hCSs contain neurons from both deep and superficial cortical layers and map transcriptionally to in vivo fetal development. These neurons are electrophysiologically mature, display spontaneous activity, are surrounded by nonreactive astrocytes and form functional synapses. Experiments in acute hCS slices demonstrate that cortical neurons participate in network activity and produce complex synaptic events. These 3D cultures should allow a detailed interrogation of human cortical development, function and disease, and may prove a versatile platform for generating other neuronal and glial subtypes in vitro.

Neuropsychiatric research has been impeded by limited access to human brain tissue, especially from early stages of neurodevelopment when the pathophysiology of many childhood-onset disorders is initiated. Neural organoids are 3-dimensional, self-organizing, multicellular structures generated from pluripotent stem cells that recapitulate some of the cell diversity, cytoarchitecture, and functional features of domains of the developing nervous system. Assembloids are 3-dimensional, self-organizing cultures created by the combination of two or more distinctly patterned organoids or an organoid plus additional cell or tissue type(s) that are used to model cell migration and connectivity. Here we review recent advances in neuropsychiatric disorder research using organoid and assembloid models to study the role of disease-relevant genes and mutations, as well as the impact of environmental risk factors on neural development. We also highlight some of the advantages and limitations of these model systems in bringing insights into the pathophysiology of neuropsychiatric disorders. [ABSTRACT FROM AUTHOR]

Deconstructing and then reconstructing developmental processes ex vivo is crucial to understanding how organs assemble and how physiology can be disrupted in disease. Human 3D stem cell-derived systems, such as organoids, have facilitated this pursuit; however, they often do not capture inter-tissue or inter-lineage cellular interactions that give rise to emergent tissue properties during development. Assembloids are self-organizing 3D cellular systems that result from the integration of multiple organoids or the combination of organoids with missing cell types or primary tissue explants. Here, we outline the concept and types of assembloids and present their applications for studying the nervous system and other tissues. We describe tools that are used to probe and manipulate assembloids and delineate current challenges and the potential for this new approach to interrogate development and disease. [ABSTRACT FROM AUTHOR]

Dravet Syndrome is an intractable form of childhood epilepsy associated with deleterious mutations in SCN1A, the gene encoding neuronal sodium channel Nav1.1. Earlier studies using human induced pluripotent stem cells (iPSCs) have produced mixed results regarding the importance of Nav1.1 in human inhibitory versus excitatory neurons. We studied a Nav1.1 mutation (p.S1328P) identified in a pair of twins with Dravet Syndrome and generated iPSC-derived neurons from these patients. Characterization of the mutant channel revealed a decrease in current amplitude and hypersensitivity to steady-state inactivation. We then differentiated Dravet-Syndrome and control iPSCs into telencephalic excitatory neurons or medial ganglionic eminence (MGE)-like inhibitory neurons. Dravet inhibitory neurons showed deficits in sodium currents and action potential firing, which were rescued by a Nav1.1 transgene, whereas Dravet excitatory neurons were normal. Our study identifies biophysical impairments underlying a deleterious Nav1.1 mutation and supports the hypothesis that Dravet Syndrome arises from defective inhibitory neurons. [ABSTRACT FROM AUTHOR]

Recent advances in cell reprogramming enable investigators to generate pluripotent stem cells from somatic cells. These induced pluripotent cells can subsequently be differentiated into any cell type, making it possible for the first time to obtain functional human neurons in the lab from control subjects and patients with psychiatric disorders. In this review, we survey the progress made in generating various neuronal subtypes in vitro, with special emphasis on the characterization of these neurons and the identification of unique features of human brain development in a dish. We also discuss efforts to uncover neuronal phenotypes from patients with psychiatric disease and prospects for the use of this platform for drug development. [ABSTRACT FROM AUTHOR]