Non-Invasive Light Therapy for Chronic Pain


Chronic pain sufferers may benefit from a non-invasive light therapy, a new study has found.

Researchers from the Montreal Neurological Institute and Hospital of McGill University were able to provide pain relief in mice using optogenetics – a highly specific, non-invasive method of light therapy.

Once neurons were subjected to yellow light, the pain response to light and heat was inhibited. The researchers said that pain relief was seen to last for more than 24 hours in mice with 1 hour of inhibition.

The experiment crossed two transgenic mice to develop a mouse with peripheral neurons that are sensitive to light therapy. To achieve this, one mouse was modified to express the Cre recombinase in Nav1.8+ neurons, while the other mouse was made to carry the gene coding for opsins.

Senior author and professor of neurology and neurosurgery at McGill University Philippe Seguela explained that the opsins, which respond to light, can only be expressed if Cre recombinase is present.

“When we transfer these to neurons, we can control their responses simply by illuminating the skin with innocuous yellow light,” said Seguela.

About 25 million American adults complain of pain that lasts for three months, according to the 2012 National Health Institute Survey.

The most commonly prescribed treatment for chronic pain includes opiates that make pain sufferers develop tolerance to the drug. A few weeks ago, the Obama administration proposed rules to curb the growing opioid abuse. In the United States alone, about 2 million individuals are dependent on painkillers, which kill more than 40 people every single day because of overdose.

Since systemic drugs can diffuse to unwanted areas, it lacks spatial specificity and molecular selectivity that can even worsen pain. Seguela said that optogenetics hurdles that problem by modifying, through genetic restriction and local light delivery, the specific cellular subpopulations involved in pain. He added that optogenetics has an advantage over drugs used to treat chronic pain because of its high temporal and spatial control on neuronal activity.

The study can be translated to humans through viral expression.

“Opsins can be packaged in viruses and viral expression can be genetically restricted to specific neuronal populations allowing a higher cellular selectivity,” said Seguela. “This will allow chronic pain patients to benefit from a non-invasive and highly precise analgesic method to modulate their pain.”

The study aims to understand the physiology of chronic pain and provide groundwork for alternative pain management.

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