Chronic pain may persist because cells carry “memories” of injuries—ie, molecular footprints that add up to more lasting damage—a recent study suggests.

In the study, published in Cell Reports, researchers from King’s College London examined immune cells in the nervous system of mice that are reportedly known to be important for the generation of chronic pain.

The research team found that nerve damage changes the epigenetic marks on some of the genes in these immune cells. The cells examined in the study still behaved normally, but the existence of these epigenetic marks may mean that they carry a ‘memory’ of the initial injury, explains a media release from King’s College London.

“We are ultimately trying to reveal why pain can turn into a chronic condition. We already knew that chronic pain patients have nerves that are more active, and we think this is probably due to various proteins and channels in those nerves having different properties,” says Dr Franziska Denk, the study’s first author, in the release.

“However, it is unclear why these nerves should remain in this overactive, highly sensitive state, even when the initial injury or disease has gone: the back pain from two years ago that never quite went away or the joints that are still painful despite your rheumatoid arthritis being in remission,” continues Denk, from the Wolfson Centre for Age Related Diseases at the Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King’s College London.

The study was partly funded by the Wellcome Trust.

Dr Giovanna Lalli, Neuroscience & Mental Health Senior Portfolio Developer at the Wellcome Trust, states in the release that, “The clues from this study, suggesting epigenetic changes may be involved in pain persisting, will hopefully lead us to better understand the mechanisms underlying chronic pain.”

[Source(s): King’s College London, EurekAlert]