University of Birmingham red light therapy assists spinal cord repair

07 May 2024

... and University of Barcelona low light treatment fights effects of chronic stress.

A project at the University of Birmingham has quantified how illumination with red light wavelengths can help the healing of traumatic spinal cord injury (SCI).

As reported in Bioengineering & Translational Medicine, the findings could help the design of implantable devices delivering phototherapy directly to the site of the spinal damage.

Photobiomodulation (PBM), the application of light for therapeutic benefit, is thought to act at a mitrochondrial level, with photon absorption reducing production of reactive oxygen species and triggering multiple favorable downstream pathways, according to the team's paper. How best to deliver the therapeutic photons has remained a topic of discussion, however.

"The translational potential of PBM is limited by the challenge of delivering effective and reliable doses transcutaneously to the injured central nervous system in humans, primarily due to the thickness of the overlying superficial tissue," noted the project in its paper.

The Birmingham project set about determining what those effective dosage levels for treatment of SCI might be, in order to clarify what future clinical or implanted devices should be aiming to deliver for maximum therapeutic benefit.

In trials using mouse cell cultures, the project found that delivery of red light at 660 nanometers for one minute per day increased cell viability by 45 percent over five days of treatment. "Excitingly, this aspect of the study showed the effect of 660 nm light was both neuroprotective, meaning it improved survival of nerve cells, and neuroregenerative, meaning it stimulated nerve cell growth," commented Birmingham'a Zubair Ahmed.

The project then designed a pair of bespoke devices delivering 660 nm light to the site of a spinal injury in mice, one as an implantable light source and the other to deliver transcutaneous irradiation. Results showed comparable results for both delivery methods, with a one-minute dose of 660 nm light daily for seven days reducing tissue scarring and promoting significant functional recovery.

This is the first time transcutaneous and direct delivery of light have been compared in SCI, and the researchers now envisage an implantable device for use in humans, where there are currently no approaches that preserve cells or improve neurological function.

"Surgery after spinal cord injury is common, but these operations are only aimed at stabilizing injuries to the bones of the spine that have been damaged by the trauma," said study lead author Andrew Stevens. "This concept is incredibly exciting, as it could offer surgeons the opportunity during the same operation to implant a device which could help protect and repair the spinal cord itself."

Rediscovery of the gut-brain axis

Another advance in PBM comes from the University of Barcelona, where a project has investigated how low-level illumination in different areas of the same animal can co-stimulate the brain and the belly at the same time, acting on "the gut-brain axis." The work was published in Journal of Affective Disorders.

"Research into the gut-brain axis is generating great scientific interest for the possible treatment of diseases of the nervous system," said Barcelona's Albert Giralt. "The new therapeutic approach focuses on this now rediscovered scenario of intervention and manipulation of the gut-brain axis to address neurological and psychiatric disorders."

The team used rigs based on those from commercial developer REGEnLIFE and first designed for studies in Alzheimer’s patients to deliver light from three sources - a near-IR laser diode and LED emitting 850 nm and a red LED providing 660 nm - to both the head and abdomen of a mouse subject. Results showed the treatment was beneficial for cognitive deficits, hippocampal spine density alterations and increased neuroinflammation induced by chronic stress.

"PBM is likely to be particularly suitable for specific forms of treatment-resistant depression," commented the Barcelona team. "We also want to explore the relationship with neuroinflammatory processes. This is one of the best-rescued parameters after PBM, and treatment-resistant depression is strongly associated with neuroinflammation."