An in vitro platform for characterizing axonal electrophysiology of individual human iPSC-derived nociceptors

Current treatments against severe forms of neuropathic pain demonstrate insufficient efficacy or lead to unwanted side effects as they fail to specifically target the affected nociceptors - a specialized subclass of sensory neurons conveying potentially damaging stimuli information to the central nervous system. Neuropathic pain may involve different nociceptor subtypes in different patients. Tools that can distinguish nociceptive axons would enable a more targeted compound screening. Therefore, we developed an in vitro platform combining a CMOS-based high-density microelectrode array with a polydimethylsiloxane (PDMS) guiding microstructure that captures the electrophysiological responses of nociceptors. Human induced pluripotent stem cell-derived (iPSC) nociceptors were cultured at low density with axons distributed through parallel 4 x 10 {micro}m microchannels exiting the seeding well before converging to a bigger axon-collecting channel. This configuration allowed the measurement of stimulation-induced responses of individual axons. Nociceptors were found to exhibit a great diversity of electrophysiological response profiles that can be classified into different functional archetypes. Moreover, we show that some responses are affected by applying the TRPV1 agonist capsaicin. Overall, results using our platform demonstrate that we were able to distinguish nociceptive axons from different subtypes. The platform provides a promising tool for screening potential candidates for nociceptor-specific drugs.