Developing a functional non-animal CNS stress model utilizing long-term potentiation with human iPSC-cortical neurons to evaluate therapeutics

Cortisol, the main stress hormone of the hypothalamic-pituitary-adrenal (HPA) axis, has been hypothesized to cause considerable detriment to cognitive function in both a time and concentration-dependent manner. However, there is a current lack of functional in vitro models available to evaluate the stress condition. Long-term potentiation (LTP) has served as a quantitative correlate for memory and learning through in vitro neuronal network responses to electrical stimuli, where a high-frequency stimulation (HFS) protocol on microelectrode arrays (MEAs) evaluates synaptic integrity related to higher-order cognition. As a novel alternative to animal studies, this study has employed a human iPSC-cortical neuron organ-on-a-chip (HoaC) system to establish a stress phenotype for synaptic dysfunction and evaluate the effects of therapeutic compounds to ameliorate stress-induced cognitive dysfunction. In our HoaC system, cortisol exposure was found to alter cortical neuron LTP, synaptic integrity, cellular morphology, and electrophysiology, confirming a cortisol-induced stress phenotype consistent with previous findings. Using this novel system, we investigated the ability of Echinacea purpurea and its active ingredient, dodeca-2E,4E,8Z,10Z-tetraenoic acid N-isobutyl amide (dodeca), to mitigate stress-induced functional decline. Following exposure to chronic stress (1 µM cortisol dosing for 7 days), both Echinacea purpurea and dodeca were found to significantly alleviate cortisol-induced cortical neuron stress in a time-dependent rescue of LTP. Together, these results characterize a novel, biologically-relevant model of neurological stress, and highlight its utility in identifying new therapeutic compounds capable of restoring stress-induced cortical neuron network deficits.