MODELLING LIGHT-CONTROLLABLE HUMAN BRAIN ORGANOIDS TO STUDY NEURAL CONNECTIVITY WITH MICROFLUIDICS DEVICES

Animal models and conventional 2D cultures fail to fully capture the structural and functional complexity of human brain circuits, limiting translational research in neurodegenerative diseases. To address this gap, we developed connectoids, a human in vitro platform enabling controlled, long-range communication between region-specific brain organoids. Connectoids are generated using custom microfluidic devices that guide directional axonal bundling while maintaining anatomical separation between organoids, allowing reproducible reconstruction of human-like neural pathways.
Human dorsal forebrain and striatal organoids were derived from hiPSCs and genetically modified to express channelrhodopsin-2 (ChR2) and/or halorhodopsin (NpHR). Multimodal data acquisition included immunohistochemistry, RT-qPCR, Western blot, live calcium imaging, and optogenetic stimulation. Preliminary results show that optogenetic transduction does not alter pluripotency or regional specification and yields mature glutamatergic and GABAergic neurons. Light stimulation reliably elicited calcium influx, confirming functional opsin expression and preserved neuronal excitability.
Importantly, region-specific organoids formed stable axonal bundles within microfluidic channels, generating structurally organized connectoids on day 80 of maturation. Early functional assays reveal propagating calcium activity along axonal tracts, indicating emerging inter-organoid signal transmission. Ongoing experiments focus on dissecting cortico-striatal circuit dynamics and on modulating excitation–inhibition balance through bidirectional optogenetic control.
This human, multi-regional, and light-controllable connectoid platform provides a powerful experimental framework to study neural circuit dynamics and neurodegenerative diseases such as Parkinson’s disease, opening new avenues for mechanistic studies and preclinical research.

Figure 1. Connectoid generated by the dorsal forebrain-striatal connection developed within the PDMS microfluidic system