In vitro identification of kainic acid-induced, concentration-dependent responses in human cortical neuronal networks

Neuronal networks derived from human induced pluripotent stem cells (hiPSCs) have gained attention for their potential use in studying cellular electrophysiology. Similar to in vivo animal models of seizures and epilepsy, neuronal activity can be altered in vitro using kainic acid (KA), a direct agonist of KA glutamate receptors. However, to utilize KA in developing more relevant in vitro seizure models, a better understanding of acute and long-term KA-mediated effects on human neurons is needed. Here, we investigated the acute (0-60 min) and long-term (≤48 h) KA concentration-dependent effects on the viability and functional activity of hiPSC-derived cortical neuronal networks via microelectrode arrays. Furthermore, in association with the long-term effects, the recovery and behavior of the networks after KA washout were assessed. The results revealed distinct acute and long-term concentration-dependent effects on neuronal functionality, where KA concentrations greater than 5 µM significantly decreased the firing and bursting rates. The effects were maintained at high KA concentrations (>15 µM) under long-term exposure. However, the KA concentrations used (5-50 µM) did not permanently compromise neuronal functionality or viability, as the firing and bursting rates recovered after KA washout in a concentration-dependent manner. High KA concentrations also increased the secretion of transfer RNA-derived small RNA fragments, highlighting their role as potential biomarkers for seizures and cellular stress. This study depicts detailed KA-mediated effects on neuronal functionality and further supports the utilization of KA in developing relevant human in vitro models in combination with in vivo epilepsy models.