Background & Aims

Sensory neurons differentiated from human induced pluripotent stem cells (hiPSC-SNs) are a promising tool to bridge the gap between basic pain research and clinical findings in patients with neuropathic pain. However, the composition of neuronal subtypes in this model has not been completely understood. Recently we identified functional subgroups within iPSC-SNs according to their firing properties. Their link to functional sensory neuron C-fiber types determined in humans using microneurography (MNG) remains to be investigated. Here, we aim to assess subtypes of hiPSC-SNs by their responsiveness to protocols derived from MNG. We are especially interested in a subgroup of neurons corresponding to silent nociceptors that are described to be spontaneously active in neuropathic pain or inflammation. We aim to assess whether this clinically-relevant subtype is present in hiPSC-SNs by assessing their unique electrophysiological fingerprint derived from MNG recordings.

Methods

HiPSC-SNs of two healthy donors were differentiated into hiPSC-SNs using a previously described protocol [1,2] and excitability was assessed using the patch-clamp technique in current-clamp mode. HiPSC-SNs were grouped according to their response to applied current injection protocols that partly resemble those used in MNG recordings to distinguish between classes of human C-fibers and to find putative silent nociceptor-like neurons.

Results

In this study we confirm that most hiPSC-SNs can be classified into three main functional subgroups: phasic, tonic and intermediate firing hiPSC-SNs. Silent nociceptors in humans are usually characterized by distinct MNG signatures including sensitivity to sine wave stimulation and the lack of the ability to follow high stimulation frequencies [3]. When applying sine wave stimulations compared to square current injections of the same duration, we found that one population among the tonically active hiPSC-SNs was especially sensitive to sine wave pulses. Interestingly this subpopulation was also not able to respond well to high frequency current injections, another hall mark of silent nociceptor biophysics. The majority of sinus preferring tonically active neurons were spontaneously active (80%) compared to other tonically active hiPSC-SNs (0%).

Conclusions

According to electrophysiological signatures in hiPSC-SNs, one part of tonically active neurons was sensitive to sine wave stimulations and did not follow high frequency stimulation well. In MNG recordings both features are a characteristic of silent nociceptors which are believed to be responsible for neuropathic pain. Therefore, tonically active hiPSC-SNs are likely to comprise more than one functional subgroup and to contain a silent nociceptor like phenotype.

References

[1] Chambers SM, Qi Y, Mica Y, Lee G, Zhang XJ, Niu L, et al. (2012) Nat. Biotechnol. 30(7): 715-720
[2] Neureiter A, Eberhardt E and Lampert A (2022) Methods Mol. Biol. 2429: 175-188
[3] Jonas R, Namer B, Stockinger L, Chisholm K, Schnakenberg M, et al. (2018) Ann Neurol. 83(5): 945-957

Presenting Author

Esther Eberhardt

Poster Authors

Esther Eberhardt

Dr. med.

University Hospital RWTH Aachen

Lead Author

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Jannis Körner MD

Insitute of Neurophysiology, Department of Anaesthesiology Uniklinik RWTH Aachen, Germany

Lead Author

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Barbara Namer

Institute of Neurophysiology/ IZKF research group neuroscience, Uniklinik RWTH Aachen, Germany

Lead Author

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Angelika Lampert Professor MD

Institute of Neurophysiology, University Hospital RWTH Aachen; Scientific Center for Neuropathic Pai

Lead Author

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Topics

  • Mechanisms: Biological-Molecular and Cell Biology