Recent research has significantly advanced the understanding of brain mechanisms involved in chronic pain and the development of non-addictive therapeutic strategies. A study by the University of Colorado Boulder identified a specific neural circuit, the caudal granular insular cortex (CGIC), as instrumental in the transition of acute pain to chronic pain.
Concurrently, a preclinical study conducted by teams from the University of Pennsylvania, Carnegie Mellon University, and Stanford University developed a gene therapy designed to target pain centers in the brain, aiming to mitigate addiction risks associated with opioid treatments. Both studies, published in The Journal of Neuroscience and Nature respectively, contribute to the development of non-addictive approaches to chronic pain management.
Identifying Brain Circuits in Chronic Pain Development
Researchers at the University of Colorado Boulder, in a study published in The Journal of Neuroscience, identified the caudal granular insular cortex (CGIC) as a neural circuit instrumental in the development of chronic pain. The research, primarily using animal models, indicated that deactivating this specific brain pathway could prevent the onset or alleviate existing chronic pain.
Linda Watkins, senior author of the study and distinguished professor of behavioral neuroscience, stated that the research utilized methods to define the brain circuit responsible for pain chronification and its communication with the spinal cord.
"Silencing this circuit could prevent chronic pain from occurring or resolve existing conditions."
The study observed that the CGIC plays a minor role in acute pain processing but is significant for the persistence of pain. The circuit is implicated in signaling the brain's somatosensory cortex, which subsequently directs the spinal cord to maintain pain signals. Activation of this pathway was observed to excite the spinal cord region that relays touch and pain, contributing to allodynia, a condition where light touch is perceived as painful.
Jayson Ball, the first author, highlighted that chronic pain affects approximately one in four adults, with many experiencing interference with daily life. When CGIC cells were deactivated immediately following a sciatic nerve injury in rats, the animals experienced short-lived pain. In models already exhibiting chronic allodynia, disabling this pathway led to a cessation of pain.
Developing a Non-Addictive Gene Therapy for Pain Management
A separate preclinical study, detailed in Nature, explored a new gene therapy designed to target specific pain centers in the brain. This therapy aims to reduce pain signals without impacting other brain functions or activating the reward pathways linked to addiction. The research was a collaborative effort involving teams from the University of Pennsylvania Perelman School of Medicine and School of Nursing, Carnegie Mellon University, and Stanford University.
Gregory Corder, co-senior author and assistant professor of Psychiatry and Neuroscience at Penn, stated that the objective was to reduce pain while minimizing the risk of addiction and dangerous side effects.
"The objective was to reduce pain while minimizing the risk of addiction and dangerous side effects."
The methodology involved investigating how morphine reduces suffering by imaging brain cells involved in pain tracking. This insight informed the design of an artificial intelligence (AI)-driven mouse model behavioral platform, which tracked natural behaviors to assess pain levels and the required treatment.
The developed gene therapy is designed to mimic morphine's pain-reducing effects but without its addictive properties. It delivers an "off switch" specifically for pain felt in the brain, aiming to provide durable pain relief without affecting normal sensation or triggering addiction pathways.
"This development as the first central nervous system (CNS)-targeted gene therapy for pain."
Public Health Context and Future Outlook
Chronic pain affects an estimated 50 million Americans, incurring annual costs exceeding $635 million in direct medical expenses and lost productivity. The studies address a public health concern also related to the opioid crisis, which was linked to 80 percent of drug-related deaths in 2019.
Researchers from both studies anticipate further work to translate these findings into human therapies. The University of Colorado Boulder team plans to investigate triggers for the CGIC to initiate chronic pain signals and explore human applications, potentially through targeted injections, infusions, or brain-machine interfaces. The University of Pennsylvania team, working with Professor Michael Platt, intends to proceed with the next phase of work to facilitate future clinical trials for the gene therapy.
The University of Pennsylvania study received funding from the National Institutes of Health, the Howard Hughes Medical Institute, the Whitehall Foundation, and the Tito's Love Research Fund. Provisional patent applications related to synthetic opioid promoters have been filed through the University of Pennsylvania and Stanford University.