The CRR and the UNIGE united against pain

Many people experience chronic pain that can last for months or even years. But how can this pain be treated in the best possible way? In order to do this, it is necessary to categorise it so that the right treatment can be prescribed. The challenge is that it is very difficult for patients to define their pain, its degree of intensity or even its location using questionnaires. To overcome this difficulty, scientists from the University of Geneva (UNIGE) have joined forces with the research department of the Clinique romande de réadaptation (CRR) in Sion to carry out a full epigenomic analysis of patients, making it possible to find the epigenetic signatures specific to each pain category. Thus, a simple blood test could be used to define which pain the person suffers from and, in the future, to prescribe treatment accordingly and to observe whether the biomarkers modified by the pain return to normal. These results can be consulted in the Journal of Pain.

Chronic pain is classified into two main categories: nociceptive pain - defined by the activation of receptors at the end of nerve fibres and found in osteoarthritis, burns or infections - and neuropathic pain, which is caused by damage to nerve structures, such as the pain caused by shingles. In order to classify which pain the patient suffers from, he or she is asked to fill in several questionnaires and to quantify the intensity of his or her pain using assessment scales. However, this is very subjective and time-consuming.

Blind genome analysis

«At the CRR, we treat many people suffering from chronic diseases, explains Bertrand Léger, researcher at the CRR and author of the study. We then asked ourselves if we couldn't join forces with scientists at the UNIGE, so that we could carry out a full epigenomic study and define specific biomarkers for each type of pain, in order to be able to categorise them quickly and reliably.» 

To do this, the Geneva team analysed the entire genomes of 57 patients: 20 with no pain, 18 with nociceptive pain and 19 with neuropathic pain. «The aim was to start without any prior hypothesis, in order to probe the genome as a whole and identify all the biomarkers involved in pain», explains Ariane Giacobino, the study's coauthor and a professor in the Department of Genetic and Developmental Medicine at the UNIGE Faculty of Medicine.

Specific and potentially reversible biomarkers

Unexpectedly, not only did the scientists identify very striking epigenetic signatures signalling pain, but also there was no overlap between nociceptive and neuropathic pain. «This total lack of similarity between the two categories of pain is very surprising, because intuitively we might think that the difficulty in defining one's pain comes from a similarity in the epigenetic signature, which is in fact absolutely not the case», reports Ariane Giacobino. 

Indeed, the biomarkers specific to nociceptive pain are the genes of the opioid system - involved in emotion, reward and pain - and the genes of inflammation, specific to irritative phenomena. Biomarkers for neuropathic pain are linked only to genes of the GABA system, the neurotransmitters of the central nervous system.

«Now that these epigenetic signatures are clearly defined, a simple blood test can be used to research these biomarkers and determine the type of pain the person is suffering from, and prescribe the appropriate treatment», rejoices Bertrand lé­ger. This means that treatment will no longer be directed at the symptoms, but at the root of the problem. Finally, since epigenetics is characterised by the fact that the expression of a gene is durably modified, it might be possible, by applying the right treatment, to return to normal. «We could imagine monitoring the reversion of pain by observing, from an epigenetic point of view, whether the biomarkers return to normal and adapt the treatment accordingly», concludes Ariane Giacobino. 

Contact person if you have any questions : 

Bertrand Léger 

Head of the Research Department
Clinique romande de réadaptation 
+41 27 603 20 75 

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