Photobiomodulation (PBM) therapy for functional recovery using an experimental model of spinal cord injury in rats

Traumatic spinal cord injury (SCI) is characterized by damage in the spinal cord, which can result in a permanent or temporary disability and different degrees of paralysis, sensory loss, and bladder/bowel dysfunction. It represents an important cause of morbidity and mortality in the affected individuals. Based on the need to develop more effective treatments for SCI, authors have been investigating the effects of photobiomodulation (PBM) therapy on this injury.

In this context, the present study aimed to evaluate the long-term effect (follow-up) of PBM using a model of SCI in rats.

For this, 33 rats were randomly divided into two experimental groups: the control group and the laser group, and sub-divided into two sub-groups (with two different periods of euthanasia post-injury, 4 and 8 weeks). PBM treatment was performed for 14 days (daily, 808 nm, continuous output, 30 mW, 0.028 cm², 1.07 W/cm², 1000 J/cm², 4 min and 42 secs). Animals were euthanized 4 and 8 weeks after the surgical procedure. For analysis, motor function and tactile sensitivity analysis were performed on days 1 and 7 post-surgery. Moreover, after euthanasia, samples were retrieved for histological and immunohistochemistry analysis. The results of the present study demonstrated that PBM improved function and motor behavior. Furthermore, irradiated animals demonstrated a decreased injury volume and decreased GFAP immunolabelling. These results suggest that PBM presented a long-term positive effect on the morphological aspects at the site of the injury and in the modulation of GFAP immunoexpression, which culminates in the improvement of the function behavior.

It may be suggested that PBM therapy in the parameters used, was able to modulate the inflammatory process, regulate the secondary lesion, decreasing cell apoptosis and edema in the earlier phases of recovery, which resulted in long-term positive effects (4 and 8 weeks). Further investigations are necessary to investigate the possible mechanisms that may explain the positive effects of PBM irradiation in SCI, which may contribute to a better understanding of the efficacy of PBM therapy and the development of more effective and safer treatments.