Robust and reproducible neuronal differentiation of human embryonic stem cells for neurotoxicology

Neuronal differentiation from pluripotent cells is commonly used to recapitulate events in early brain development. Neuronal precursors and developing neurons cultured in vivo, rely on attachment, density and cell-to-cell communication, and cell-passaging steps should be minimised to avert disruption of network cross-connectivity. This is crucial both for viability and maturation, and the former also applies to human embryonic stem cells (hESCs). Neuronal differentiation protocols from hESCs for neurotoxicology assessment studies should therefore provide standardized cell density requirements, and optimised coating matrix conditions. The effect of drug treatments may be masked by compound instability and degradation in cell culture medium but performing daily media changes can circumvent these issues. Here, we describe a robust neuronal differentiation protocol using dual SMAD/WNT signalling inhibitors LDN193189, SB431542 and XAV939 (LSX) for neural induction of hESCs, followed by self-patterning and cell maturation stages, for the generation of ventral telencephalic progenitors and neurons. We provide critical information on the optimized cell culture parameters and standardized methods of stage-specific validation. Using cell counts, immunofluorescence, qRT-PCR, and a proof of principle treatment with valproic acid to showcase issues with drug-induced cell toxicity, we facilitate reproducibility of the protocol. Graphical abstract