In Vitro Pain Assay Using Human iPSC-Derived Sensory Neurons and Microelectrode Array.

Drug-induced peripheral neuropathy occurs as an adverse reaction of chemotherapy. However, a highly accurate method for assessing peripheral neuropathy and pain caused by compounds has not been established. The use of human-induced pluripotent stem cell (hiPSC)-derived sensory neurons does not require animal experiments, and it is considered an effective method that can approach extrapolation to humans. In this study, we evaluated the response to pain-related compounds based on neural activities using in vitro microelectrode array (MEA) measurements in hiPSC-derived sensory neurons. Cultured sensory neurons exhibited gene expression of the Nav1.7, TRPV1, TRPA1, and TRPM8 channels, which are typical pain-related channels. Channel-dependent evoked responses were detected using the TRPV1 agonist capsaicin, a TRPA1 agonist, allyl isothiocyanate (AITC), and TRPM8 agonist menthol. In addition, the firing frequency increased with an increase in temperature from 37°C to 46°C, and temperature sensitivity was observed. In addition, the temperature of the peak firing rate differed among individual neurons. Next, we focused on the increase in cold sensitivity, which is a side effect of the anticancer drug oxaliplatin, and evaluated the response to AITC in the presence and absence of oxaliplatin. The response to AITC increased in the presence of oxaliplatin in a concentration-dependent manner, suggesting that the increased cold sensitivity in humans can be reproduced in cultured hiPSC-derived sensory neurons. The in vitro MEA system using hiPSC-derived sensory neurons is an alternative method to animal experiments, and it is anticipated as a method for evaluating peripheral neuropathy and pain induced by compounds.