Citation:

Boyd, S., J. Conley, AND T. Shafer. New Approach Methodology (NAM) using 3D Human iPSC-Derived Neural Organoids to Screen for Developmental Neurotoxicity Hazard. Microphysiological Systems (MPS) World Summit 2024, Seattle, WA, June 10 - 14, 2024. https://doi.org/10.23645/epacomptox.26103607

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Presentation to Microphysiological Systems (MPS) World Summit 2024

Description:

The developing brain is particularly vulnerable to neurotoxicity, and exposures to environmental neurotoxicants during this period can result in altered brain development. To investigate the effects of chemical exposures on neurodevelopment, human induced-pluripotent stem cell (iPSC)-derived neural organoid models have been utilized due to their ability to form mature neuronal populations and exhibit spontaneous electrical fields. Initial time-course experiments were done to characterize the organoids’ development of electrical activity using a high-density microelectrode array (hdMEA) and demonstrated formation of a complex interconnected network. Of the timepoints tested, neuronal activity peaked in organoids plated on the hdMEAs at 3-weeks post-initiation of differentiation, indicating neurodevelopmental network formation.   To model neurodevelopment for toxicological screening, organoids differentiated for 3-weeks were plated on hdMEAs for 29 days. Starting at two-days post-plating, organoids were treated with loperamide (0.03-100µM), glyphosate (0.3-30 µM), dieldrin (1-100µM), and deltamethrin (1-100µM) three times per week. Throughout the 29 days on the hdMEA, electrical activity from the organoids was recorded to measure network formation, general activity, and features of action potential propagation and axonal morphology via axon tracking software. Preliminary results show that organoid exposure to dieldrin, deltamethrin, loperamide, but not glyphosate result in a concentration-dependent disruption in the formation of the network characterized by a reduction in percent of active electrodes, burst peaks, and spikes per burst. Dieldrin increased burst frequency and inter-burst interval while deltamethrin only increased burst frequency. Axon tracking in deltamethrin-exposed organoids shows a concentration-dependent decrease in action potential propagation features including neuron firing rate, conduction velocity, and the total number of spikes per neuron. Meanwhile, dieldrin exposure decreased the peak spike amplitude at the initiation site of action potentials. A chemical washout did not appear to impact the electrical activity of the organoids, suggesting an irreversible disruption to the development and formation of neural networks rather than an acute pharmacological response. Furthermore, only high doses of dieldrin (100µM) and loperamide (10µM) induced cytotoxicity by decreasing viability and LDH. These data indicate that this approach could be a valuable addition to the existing in vitro approaches for developmental neurotoxicity screening. (This abstract does not reflect EPA policy).   

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