Human inducible pluripotent stem cell-derived sensory neurons express multiple functional ion channels and GPCRs.

Aims Aim of the study was to characterize functional ion channel and GPCR responses by using selective pharmacological tools and intracellular calcium imaging from human inducible pluripotent stem cell-derived sensory neurons. Methods Sensory neurons were generated from human keratinocytes that were reprogrammed to inducible pluripotent stem cells by using standard Yamanaka factors. Inducible pluripotent stem cells were differentiated into sensory neurons by using 2 differentiation protocols (small molecule and PA6 co-culture). Sensory neurons were loaded with intracellular calcium dye Fluo-4. Single-cell calcium imaging was performed with Photometrics Evolve EM-CCD camera at physiological temperature. Cells were perfused with a Ringer solution at 2-3 ml/min into which pharmacological compounds were dissolved. Data was analyzed with Till Photonics Offline Analysis program. Results Most of the results were obtained from PA6 differentiated neurons. 50 s application of 50 mM KCl solution was used as diagnostic tool to activate voltage-gated calcium channels and thereby evoke intracellular calcium elevation. Functional ASIC, NMDA, kainate and TRPA1 ion channels were present in a subset of sensory neurons. Majority of sensory neurons showed robust responses to purinergic stimulation with ATP and histaminergic stimulation with histamine, but not to subtype selective histamine H1, H2 or H4 stimulation suggesting the presence of H3 receptor subtype All cells responded strongly to protease-activated receptor stimulation with a low dose of trypsin. Interestingly, at single-cell level notable heterogeneity of ion channel and GPCR responses was observed. Conclusions Our results suggest that iPS-derived sensory neurons will be valuable in further pharmacological studies as well as sensory neuropathy disease modeling.