Highly efficient generation of human Cerebral Organoids bypassing embryoid body stage

Abstract

Human cerebral organoids (hCOs) are a promising in vitro model that may overcome some of the limitations that currently exist when studying human brain development and disease. Since Lancaster et al. first generated hCOs, efforts have been made to better recapitulate the physiology of the human brain and improve the efficiency and reproducibility of protocols. Different groups employed dual-SMAD inhibition (double inhibition of the transforming growth factor-β (TGF-β) and bone morphogenetic proteins (BMPs) pathways) to achieve rapid neural induction. The method developed here, outlines the generation of homogeneous organoids by rapid neuroepithelial induction, avoiding the Embryoid Body (EB) stage. The efficiency of this protocol to form neuroepithelial structures and subsequently organoids is almost 100% due to the use of dual-SMAD inhibition in combination with CHIR99021 (a GSK3β inhibitor/Wnt activator) at the neural induction stage. This is a simple and reproducible protocol as we do not need to use Matrigel or bioreactors which standardizes the methodology. It is also a robust protocol as we have successfully performed it on human embryonic stem cells (hESCs) and human induced pluripotent stem cells (iPSCs). We performed IHC and Q-RT-PCR assays for cell cycle, neural precursors, neuronal and synaptic vesicle markers. The generated hCOs are highly homogeneous and show ventricular zones (VZs) with radial glia in the center that differentiate to give rise to neurons located around these VZs. These neurons acquire a mature state and are able to form synapses. In addition, we also performed IHC and Q-RT-PCR assays for different markers of oligodendrocytes, astrocytes, microglial cells and vasculature obtaining promising results. We believe that this protocol will be a breakthrough in the generation of organoids for use as a model for the study of neurodevelopmental and neurological diseases, as well as for drug testing.