Periodic Reporting for period 1 - RIIBS (Role of membrane potential Instabilities in Irritable Bowel Dysease)
Reporting period: 2023-10-01 to 2025-09-30
Chronic visceral pain, such as that experienced by people with Irritable Bowel Syndrome (IBS), represents one of the most prevalent yet least understood forms of long-term pain. Despite affecting millions of Europeans and generating substantial healthcare and socioeconomic burden, the biological mechanisms that initiate and maintain visceral pain are still unclear. Current treatments often provide limited relief, and the lack of mechanistic understanding slows the development of new, effective therapies.
This project set out to uncover how sensory neurons—the cells that detect signals from the body—become abnormally excitable in IBS. A particular focus was placed on a recently discovered phenomenon called membrane potential instabilities (MPIs). These small, spontaneous voltage fluctuations may help explain why some neurons fire excessively, contributing to chronic pain. Understanding when and why these instabilities appear, and how they are altered in IBS, could reveal new therapeutic targets and improve how visceral pain is managed.
The project pursued three integrated objectives:
1. Determine how IBS-like conditions modify electrical activity in mouse sensory neurons, with special attention to MPIs.
2. Develop a new optical technique that allows fast, high-resolution measurements of neuronal electrical activity, enabling the study of MPIs at subcellular levels.
3. Evaluate whether similar mechanisms occur in human sensory neurons, supporting the translation of findings into human biology.
Together, these objectives aim to generate fundamental knowledge that can guide the development of new analgesic strategies, reduce the burden of chronic visceral pain, and support European leadership in neuroscience research and innovation.
This project set out to uncover how sensory neurons—the cells that detect signals from the body—become abnormally excitable in IBS. A particular focus was placed on a recently discovered phenomenon called membrane potential instabilities (MPIs). These small, spontaneous voltage fluctuations may help explain why some neurons fire excessively, contributing to chronic pain. Understanding when and why these instabilities appear, and how they are altered in IBS, could reveal new therapeutic targets and improve how visceral pain is managed.
The project pursued three integrated objectives:
1. Determine how IBS-like conditions modify electrical activity in mouse sensory neurons, with special attention to MPIs.
2. Develop a new optical technique that allows fast, high-resolution measurements of neuronal electrical activity, enabling the study of MPIs at subcellular levels.
3. Evaluate whether similar mechanisms occur in human sensory neurons, supporting the translation of findings into human biology.
Together, these objectives aim to generate fundamental knowledge that can guide the development of new analgesic strategies, reduce the burden of chronic visceral pain, and support European leadership in neuroscience research and innovation.
During the project, significant scientific progress was made across all planned research lines.
First, the project investigated how IBS-like conditions alter the excitability of sensory neurons. A conventional mouse model of IBS could not be implemented due to genetic incompatibility with the specialised strains required for the project. As an alternative, the project used a newly identified molecule found to be strongly increased in tissue samples from IBS patients. Applying this molecule to mice reproduced key features of IBS-related pain. In laboratory experiments, this molecule was shown to make sensory neurons more excitable, lowering their activation threshold and dramatically increasing MPIs. These findings provide a novel mechanistic link between patient-derived molecular changes and neuronal hyperexcitability.
Second, the project developed a new experimental model based on fast voltage-sensitive dyes. This high-speed optical approach makes it possible to capture electrical events across the entire neuronal cell body with single–action potential resolution. Using this technique, the project demonstrated that MPIs might be implied in the generation of spontaneous neuronal activity. The system also enabled a screening strategy that identified the specific receptor through which the IBS-associated molecule acts.
Third, the project attempted to translate these discoveries to human sensory neurons. Commercially sourced human cells could not be obtained for regulatory and technical reasons, and an initial in-house stem-cell approach did not yield functional neurons. Recordings were ultimately obtained through a collaborating laboratory, allowing the project to show that MPIs are also generated by human neurons. A new differentiation protocol is currently being implemented to complete the final part of this objective.
Together, these activities significantly advance our understanding of the electrical mechanisms that may drive visceral pain, and they establish new tools that will continue to support research in this field.
First, the project investigated how IBS-like conditions alter the excitability of sensory neurons. A conventional mouse model of IBS could not be implemented due to genetic incompatibility with the specialised strains required for the project. As an alternative, the project used a newly identified molecule found to be strongly increased in tissue samples from IBS patients. Applying this molecule to mice reproduced key features of IBS-related pain. In laboratory experiments, this molecule was shown to make sensory neurons more excitable, lowering their activation threshold and dramatically increasing MPIs. These findings provide a novel mechanistic link between patient-derived molecular changes and neuronal hyperexcitability.
Second, the project developed a new experimental model based on fast voltage-sensitive dyes. This high-speed optical approach makes it possible to capture electrical events across the entire neuronal cell body with single–action potential resolution. Using this technique, the project demonstrated that MPIs might be implied in the generation of spontaneous neuronal activity. The system also enabled a screening strategy that identified the specific receptor through which the IBS-associated molecule acts.
Third, the project attempted to translate these discoveries to human sensory neurons. Commercially sourced human cells could not be obtained for regulatory and technical reasons, and an initial in-house stem-cell approach did not yield functional neurons. Recordings were ultimately obtained through a collaborating laboratory, allowing the project to show that MPIs are also generated by human neurons. A new differentiation protocol is currently being implemented to complete the final part of this objective.
Together, these activities significantly advance our understanding of the electrical mechanisms that may drive visceral pain, and they establish new tools that will continue to support research in this field.
The project generated several advances that move well beyond the current state of the art in pain neurobiology.
A major scientific contribution is the identification of a patient-derived molecule as a potent modulator of excitability and MPIs in sensory neurons. Demonstrating that this molecule can induce IBS-like hypersensitivity in vivo and robust hyperexcitability in vitro strengthens the connection between human molecular findings and neuronal mechanisms. This opens new possibilities for developing targeted therapies that address upstream drivers of visceral pain.
Another major breakthrough is the establishment of a new optical approach allowing fast, whole-cell voltage imaging with millisecond precision. This technique is rarely applied to peripheral sensory neurons and provides an unprecedented view of how action potentials and MPIs are generated. It represents a valuable platform for future mechanistic studies, drug screening, and translational research. The project also provides new evidence that MPIs are relevant in human nociceptors.
Looking forward, additional work is needed to:
• Test the molecule and receptor mechanisms directly in human neurons.
• Investigate whether MPIs can serve as biomarkers or therapeutic targets.
• Explore the potential of the optical imaging model for pharmacological screening.
These developments could facilitate the emergence of innovative treatments for visceral pain and strengthen Europe’s capacity for translational neuroscience research.
A major scientific contribution is the identification of a patient-derived molecule as a potent modulator of excitability and MPIs in sensory neurons. Demonstrating that this molecule can induce IBS-like hypersensitivity in vivo and robust hyperexcitability in vitro strengthens the connection between human molecular findings and neuronal mechanisms. This opens new possibilities for developing targeted therapies that address upstream drivers of visceral pain.
Another major breakthrough is the establishment of a new optical approach allowing fast, whole-cell voltage imaging with millisecond precision. This technique is rarely applied to peripheral sensory neurons and provides an unprecedented view of how action potentials and MPIs are generated. It represents a valuable platform for future mechanistic studies, drug screening, and translational research. The project also provides new evidence that MPIs are relevant in human nociceptors.
Looking forward, additional work is needed to:
• Test the molecule and receptor mechanisms directly in human neurons.
• Investigate whether MPIs can serve as biomarkers or therapeutic targets.
• Explore the potential of the optical imaging model for pharmacological screening.
These developments could facilitate the emergence of innovative treatments for visceral pain and strengthen Europe’s capacity for translational neuroscience research.