Modelling inflammation-induced peripheral sensitization in a dish – more complex than expected?

Peripheral sensitization of nociceptors is believed to be a key driver of chronic pain states. Here, we sought to study the effects of a modified version of inflammatory soup on the excitability of human stem-cell derived sensory neurons. For this, we used a pre-existing and a novel stem cell line, modified to stably express the calcium sensor GCamP6f. Upon treatment with inflammatory soup, we observed no changes in neuronal transcription or functional responses upon calcium imaging, and only a very minor increase in resting membrane potential via whole cell patch clamping. Similarly small changes were observed when treating mouse primary sensory neurons with inflammatory soup. A semi-systematic re-examination of past literature further indicated that observed effects of inflammatory mediators on dissociated sensory neuron cultures are generally very small. We conclude that modelling inflammation-induced peripheral sensitization in vitro is non-trivial and will require careful selection of mediators and/or more complex, multi-cellular setups. Especially in the latter, our novel GCamP6f induced-pluripotent stem cell line may be of value. Overall design: To investigate changes in gene expression across maturation of day 29-30 (D30), day 50-53 (D50) and day 69-70 (D70) iPSC-derived sensory neurons. To investigate changes in gene expression of day 60 iPSC-derived sensory neurons when cultured with a modified inflammatory soup (IS) of mediators (TNF, NGF, bradykinin, serotonin, histamine, PGE2) for 24 hours. Conditions were replicated across four differentiations, from two iPSC lines (N=4).