Developmental GABA polarity switch and neuronal plasticity in Bioengineered Neuronal Organoids

Brain organoids are promising tools for disease modelling and drug development. For proper neuronal network formation excitatory and inhibitory neurons as well as glia need to co-develop. Here we report the directed differentiation and self-organization of induced pluripotent stem cells in a collagen hydrogel towards a highly interconnected neuronal network in a macroscale tissue format. Bioengineered Neuronal Organoids (BENOs) comprise interconnected excitatory and inhibitory neurons as well as supportive astrocytes and oligodendrocytes. Giant depolarizing potential (GDP)-like events observed within 20-40 days of BENO culture mimic early network activity of the fetal brain. The switch from excitatory to inhibitory GABA activity, and reduced GDPs at >40 day BENO cultures indicate progressive neuronal network maturation. BENOs demonstrate expedited complex network burst development after two months of culture and provide the first evidence for long-term potentiation and plasticity in brain organoids. BENOs exhibit structural and functional properties similar to the fetal brain and thus may be explored as a model to study the development of neuronal plasticity. Overall design: Bioengineered neuronal organoid RNA was analyzed at different time points of directed cortical differentiation in a collagen hydrogel. 3-6 organoids were used as biological replicates for each time point. Organoids derived from 2 independent differentiation experiments.