Functional cortical neurons and astrocytes from human pluripotent stem cells in 3D culture

Abstract

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.

Translational potential of human brain organoids

“…Consistent with that notion, improved uniformity is seen in the region‐specific organoid models which employ soluble neural inductive factors, but still there exist considerable variabilities 30, 31, 35. At least three reasons could account for them.…”

“…Building on these earlier works, a recent flurry of papers described the generation of various neural organoids (Table 1), ranging from the whole‐brain organoids,27, 28, 29 to large sub‐brain regions such as cortical organoids,30, 31 to specific regions, including cerebellum,32 midbrain,33 adenohypophysis,34 hypothalamus,35 and hippocampus 36. Comparing with the classical neurospheres, these organoids are generally much larger.…”

“…Nevertheless, among all published organoids reports only a handful described the presence of functional astrocytes and oligodendrocytes, and they emerge late in culture 30, 56, 57, 58. The inadequate presence of functional astrocytes and oligodendrocytes thus limits organoids’ use to study glial‐related aspects of neuropathology.…”

“…Current brain organoids closely resemble fetal brains,28, 30, 66 and can only partially represent the diverse functional cell types of the brain, making them less ideal for studying complex network activities and circuit formations. It also raises the question as in to what extent can brain organoids effectively model neuropsychiatric or neurodegenerative diseases.…”

Modeling Williams syndrome with induced pluripotent stem cells

“…Thus, 2D neuronal cultures could possibly recapitulate only cellular defects occurring during early stages of brain development and the findings obtained from such models must be cautiously interpreted. Recently, the development of 3D culture system resulting in brain organoids has been reported, [36][37][38] offering more closely relevant in vitro models for mature brain organization and cellular network. Different differentiation protocols have been developed and fine-tuned to generate organoids with different particular brain region identity, 37,39 potentially allowing study of pathological effects focusing on specific yet complex 3D brain-like structures.…”