A drug-free approach to relieve chronic pain

Using light to help relieve chronic pain

Optogenetics is a technique that uses light to overcome the poor selectivity of electrical stimulation in mixed nerve bundles.

Nerves do not naturally respond to light, so we must modify the target nerve using gene therapy so that it can respond to a pulse of light.

Other nerve fibres will be completely unaffected.

The ability to safely and selectively control nerve fibre activity is critical to developing effective treatments for a range of conditions, including chronic pain.

Why are new treatments needed for chronic pain?

Damage to a nerve from disease, injury, or infection can lead to chronic pain, a debilitating condition that affects everyday life, work, mood, and sleep.

A drug-free therapy or treatment device would have a profound impact on the quality of life of individuals and their families, avoiding the serious side-effects and addiction that accompany chronic use of opioids, and reducing the burden on health services.

Use of the device would be on-demand and localised to the site of pain, giving extraordinary control to the recipient.

Our research addresses a fundamental limitation of electrical stimulation techniques which do not discriminate between the many different types of nerve fibers in mixed nerve bundles.

We will apply optogenetics techniques to the nerve to enable highly selective control of nerve activity using light, combining this with electrical stimulation to reduce overall power usage.

This research could revolutionise the way we interact with the nervous system.

Our research

We first developed optogenetic techniques for improving the clarity of sound for cochlear implant users.

Following highly successful outcomes, we tested optogenetic methods for controlling activity in the sciatic nerve, a nerve that contains a mixture of nerve types.

We showed selective and prescise activation of a group of nerves responsible for the sensation of touch, whereas electrical stimulation was far less precise.

However, compared to electrical stimulation, controlling nerve activity with light uses more power which could hinder development of a device for clinical use.

To overcome this, we developed a combined protocol of optogenetic and electrical stimulation methods.

In world-first studies, we used low intensity light to prime the modified nerve fibres to be more ready to fire, while simultaneously using a tiny amount of electricity to activate the selective nerve population.

Using this approach, we were able to achieve selective control of nerve activity using less electricity and less light than either of these methods alone.

By using less electrical current than electrical-only methods, there were fewer side-effects resulting from activation of unintended nerves.

Also, by using less light for activation, our technology is safer and uses less power than optical-only methods.

Since the nerve fibers responsible for touch sensation are potential targets for chronic pain conditions, these findings could be used to develop effective strategies to selectively manipulate pain transmission pathways around the body.

Next steps for our research

Using optogenetics techniques, we can selectively activate or suppress nerve activity, both of which could have a role in the treatment of chronic pain.

Following the success of optogenetics techniques for selective activation in the sciatic nerve, our researchers are now investigating selective suppression of nerve activity in damaged nerves that are causing chronic pain.

We will determine the safety and efficacy of employing optogenetics for unprecedented control over pain signalling pathways. 

The research team

Dr Mary Ardren, Dr Sophie Payne, Jerico Matarazzo, Elise Ajay, Associate Professor Andrew Wise, Professor James Fallon, Associate Professor Rachael Richardson

Key publications

JV Matarazzo, EA Ajay, SC Payne, E Trang, AC Thompson, AK Wise, JB Fallon, RT Richardson (2023) Combined optogenetic and electrical stimulation of the sciatic nerve for selective control of sensory fibers Frontiers in Neuroscience 17:1190662 https://doi.org/10.3389/fnins.2023.1190662