Content area
Abstract
Over the past decade, differentiation protocols of pluripotent stem cells in monolayers have led to the generation of a variety of neural cell types5, but these two-dimensional (2D) methods are unlikely to recapitulate the cytoarchitecture of the developing three-dimensional (3D) nervous system or the complexity and functionality of in vivo neural circuits. These needs have spawned 3D approaches for generating organoid cultures containing mixed ectodermal derivatives68. Although these methods recapitulate many aspects of corticogenesis and display a level of self-organization beyond what is possible in 2D cultures, there remain obstacles, including the need for (i) controlled specification of cell types, (ii) cortical lamination comprising equal proportions of superficial- and deep-layer neurons, (iii) concomitant generation of nonreactive astrocytes, (iv) robust synaptogenesis and spontaneous synaptic activity, (v) organization of a functional neural network that can be perturbed and probed in intact preparations and (vi) reproducibility between hiPSC clones within and across differentiations.