Abstract
Human cell types differentiated from induced pluripotent stem cells (iPSC) offer a unique access to human cellular material for toxicity screening. Such access is valuable for tissues such as those of neuronal origin that have been traditionally impossible to obtain. An additional key advantage to iPSC systems is contextual relevance for mechanistic studies that overcome many limitations of rodent primary cells and immortalized cell lines. Here we provide examples of using iPSC-derived cortical GABAergic, glutamatergic, and midbrain dopaminergic neurons in structural and electrical toxicity investigations. Interrogations focus on unique neuronal activity including Ca2+ oscillations, excitotoxicity, and seizurogenic activity. The utility of the various models is demonstrated by; 1) sub-type specific behavior 2) differential responses to toxicants, and 3) multiplexing experiments to move from phenotypic to mechanistic interpretations. The highly-excitatory iPSC-glutamatergic neurons display synchronized network-level bursting behaviors on the MEA, while cortical GABAergic neurons also display electrical activity but lack network synchronization. iPSC-neurons are susceptible to neurotoxicants with both the broad-spectrum kinase inhibitor staurosporine as well as glutamate inducing cell death. The effects of glutamate are inhibited by the antagonists DNQX and D-AP5 indicating excitotoxicity as the underlying mechanism for glutamate. Further, multiplexed experiments enable easy movement from phenotypic responses such as LDH release and ATP production to specific aspects of cell death such as apoptosis via caspase activation. Overall, iPSC-derived neurons exhibit functional glutamate pathways that respond appropriately to known agonists and antagonists, thus providing biologically relevant models for identifying emerging targets for neuro-based toxicity research and beyond.
