Gel injections could soothe lower back pain

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A treatment based on a natural anti-inflammatory substance found in bodily tissues may ease the pain of disc degeneration in the lower back

Sufferers of chronic lower-back pain are all too aware of the challenges and frustrations it can bring to daily life. Now, researchers in Ireland and Japan have shown that a pain therapy similar to one used for osteoarthritis could help treat it.

Around a third of patients with lower-back pain suffer from deterioration of the intervertebral disc. Situated between vertebrae in the back, the discs absorb shock associated with movement and loading, but they can gradually degrade with age or injury. This happens because a substance in the disc called hyaluronic acid, which is responsible for maintaining cellular structure and inflammatory responses, begins to break down. The degraded form of hyaluronic acid allows degrading enzymes to become established, and this increases pain sensitivity in the area.

“Previous research in this field has never bridged the disciplines of biomaterial-mediated regeneration and neuroscience (pain signalling),” says Abhay Pandit from the Science Foundation Ireland−funded Centre for Research in Medical Devices (CÚRAM), National University of Ireland in Galway, who led the team. “An existing therapy for osteoarthritis and other inflammatory conditions involves giving patients a boost of hyaluronic acid, which replaces degraded forms of the acid and reduces pain. We wondered if a therapy based on hyaluronic acid could also work for back pain.”

Since no appropriate pain models were available for examining disc degeneration, Pandit’s team established a rat model to characterize lower back pain on the molecular and behavioural levels. Rats are often used as models for injury and drug testing because they respond in specific ways to pain, allowing researchers to judge treatment success.

Pandit’s team developed a hyaluronic acid hydrogel that could be directly injected at the injury site. They divided the rats into two groups — one received hyaluronic acid injections, the other did not — and monitored them for a month, conducting stimuli tests for pain. The rats treated with hyaluronic acid gel had lower levels of inflammatory markers and appeared to be in far less pain than those without treatment.

“Hyaluronic acid silences pain-generating sites at a cellular level, meaning the signal is blocked from reaching the brain,” says Pandit. “The hyaluronic acid itself also has anti-inflammatory properties, so the gel has a dual effect.”

It will be at least three to four years before gel injections reach human clinical trials, however, as Pandit explains: “Rats are non-loadbearing animals whereas human intervertebral discs carry substantial weight, so further investigations are needed. We’re also looking into less invasive ways of delivering this formulation.”

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  1. Science Advances 4, eaaq0597 (2018). doi: 10.1126/sciadv.aaq0597