TRP Channel Function in iPSC-Derived Sensory Neurons

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Using somatic cells to generate induced pluripotent stem cells (iPSC) is an established method in research and has multiple applications and advantages. An increasing amount of cell types have been successfully differentiated from iPSCs, including hematopoietic cells, cardiomyocytes, smooth muscle cells, pancreas, liver and renal tissue. Directing differentiation into neuronal cells has the great benefit of bypassing the problematic isolation of human neuronal cells. Recently, a protocol using dual SMAD inhibition was shown to drive differentiation into sensory neuron-like cells. While expression of canonical markers of sensory neurons has already been validated, an in-depth characterization of sensory TRP channels in these induced neurons is still lacking. In this study, we use qPCR, Fura-2-based microfluorimetry and patch-clamp experiments to evaluate the expression and function of the sensory TRP channels at different time points during the differentiation toward a sensory neuron phenotype. We not only confirm expression of the sensory channels TRPV1, TRPM8 and TRPA1, but also demonstrate for the first time strong molecular and functional expression of TRPM3 in iPSC-derived sensory neurons. Interestingly, we found a temporarily increase of TRPM3 responses at an early time point in differentiation, which might indicate a role for this channel in the development of sensory neurons. To conclude, we were able to produce sensory neurons using iPSCs, and validated functional expression of TRP channels important in somatosensation. This approach has the potential to investigate the development of sensory neurons in vitro, and to explore the cellular physiology and pharmacology of TRPM3 and other sensory TRP channels in a human context. Moreover, it may open the door to generate patient-derived neurons for disease modeling and target validation.