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

Neuropathic pain is characterized by aberrant activity of specific nociceptor populations, as demonstrated through functional assessments such as microneurography. 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. Tools that can recapitulate aspects of microneurography in vitro 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 individual axons. Human induced pluripotent stem cell-derived (hiPSC) sensory neurons were cultured in a way that allowed axons to be distributed through parallel 4 ×10μm 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. Sensory neurons 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 individual axon responses, making the platform a promising tool for testing therapeutic candidates targeting particular sensory neuron subtypes.