Generation of hES/iPS cell-derived sensory neurons: a new approach to study mechanosensation
Final Report Abstract
My initial aims, when receiving the grant, centered around the question wether the recently identified mechanosensitive ion channel PIEZO2 is involved in the detection and transduction of noxious mechanical stimuli in pain-sensing nociceptive neurons of the peripheral nervous system and what accessory proteins could be involved in the transduction process. To that end I had established a procedure to generate sensory neurons, showing molecular and functional characteristics of nociceptor-like cells from human pluripotent stem cells by timely induced expression of the transcription factor NEUROGENIN1. We found that mechanical stimulation of the cell bodies resulted in electrical responses, defining the neurons as polymodal mechano-nociceptors. Absence of PIEZO2 diminished the response to mechanical stimulation and suggested indeed a role for PIEZO2 in sensation of noxious stimuli. Despite some supporting data generated from dispersed mouse DRG neurons, our finding contradicted studies performed with patients lacking PIEZO2 expression, that did not show any impairment regarding their ability to sense painful stimuli. As we could not convince the scientific community of our findings, I decided to refocus my research interests and investigate aspects of sensory neuron development in vitro. I investigated how changes in the external environment of the differentiating neurons, for example addition of serum or retinoic acid, would influence the generation of nociceptor-like cells. Thereby we found that retinoic acid can change the functionality of the derived sensory neurons from all responding to the TRPV1 agonist Capsaicin (no retinoic acid) to none responding to Capsaicin (plus retinoic acid). A whole project emerged from this finding, resulting in a collaboration with the Karolinska Institute in order to find out if retinoic acid also plays a role during the in vivo development of specific sensory neuron subtypes. This project is still ongoing. Another project that emanated from the work of the previous years is the question which transcription factors besides NGN1 could influence the generation of nociceptor-like cells and if additional factors could help to gain more mature neurons. Based on a publication from our collaborators at Karolinska, we investigated the transcription factor Neurod2. First experiments could show, that Neurod2 is sufficient to generate nociceptor-like cells, which express different and more defined markers compared to our initial differentiation procedure using NGN1. We will soon start some single cell sequencing experiments to compare the derived nociceptorlike cells from both approaches. In an attempt to use the human stem cell derived neurons in a more translational context, I started a third project that investigates the synaptic transmission between induced nociceptor-like cells and induced glutamatergic-like cells under normal and sensitized conditions, including pluripotent stem cells derived from patients suffering from pain. This project is part of the Heidelberg pain consortium (SFB1158).
Publications
- HESC-derived sensory neurons reveal an unexpected role for PIEZO2 in nociceptor mechanotransduction
Katrin Schrenk-Siemens, Jörg Pohle, Charlotte Rostock, Muad Abd El Hay, Ruby M. Lam, Marcin Szczot, Shiying Lu, Alexander T. Chesler, Jan Siemens
(See online at https://doi.org/10.1101/741660)
