Low-Level Laser Therapy and Spinal Cord Injury: Effects of 3 Different Fluences in the Intermediate Period of Repair in an Experimental Model in Rats

Abstract The aim of this study was to evaluate the effectiveness of 3 different fluences of low-level laser therapy (LLLT) in intermediate period of spinal cord repair using an experimental model in rats. Thirty two rats were randomly divided into four experimental groups: Control Group (CG); Laser treated group 500 J/cm² (L-500); Laser treated group 750 J/cm² (L-750) and Laser treated group 1000 J/cm² (L-1000). Spinal cord injury (SCI) was performed by an impactor equipment (between 9th and 10th thoracic vertebrae), with a pressure of 150 kdyn. Afterwards, the injured region was irradiated daily for 14 consecutive sessions, using an 808 nm laser, at the respective fluence of each experimental groups. Locomotor function and tactile sensitivity were performed on days 1 and 15 post-surgery. Animals were euthanized 15 days post-surgery and samples were retrieved for histological and immunohistochemistry analysis. Functional behavior and tactile sensitivity were improved after laser irradiation. Moreover, higher fluencies of LLLT reduced the volume of injury. Additionally, LLLT produced a decreased CD-68 expression. These results demonstrated that, for an intermediate period of SCI repair, LLLT at higher fluences, was effective in promoting functional recovery and modulating the inflammatory process in the spinal cord of rats after traumatic SCI.

Low-level laser therapy modulates demyelination in mice.

There are no effective therapies for remyelination. Low-level laser therapy (LLLT) has been found advantageous in neurogenesis promotion, cell death prevention, and modulation of inflammation in central and peripheral nervous system models. The purpose of this study was to analyse LLLT effects on cuprizone-induced demyelination. Mice were randomly distributed into three groups: Control Laser (CTL), Cuprizone (CPZ), and Cuprizone Laser (CPZL). Mice from CPZ and CPZL groups were exposed to a 0.2% cuprizone oral diet for four complete weeks. Six sessions of transcranial laser irradiation were applied on three consecutive days, during the third and fourth weeks, with parameters of 36 J/cm2, 50 mW, 0.028 cm2 spot area, continuous wave, 1 J, 20 s, 1.78 W/cm2 in a single point equidistant between the eyes and ears of CTL and CPZL mice. Motor coordination was assessed by the rotarod test. Twenty-four hours after the last laser session, all animals were euthanized, and brains were extracted. Serum was obtained for lactate dehydrogenase toxicity testing. Histomorphological analyses consisted of Luxol Fast Blue staining and immunohistochemistry. The results showed that laser-treated animals presented motor performance improvement, attenuation of demyelination, increased number of oligodendrocyte precursor cells, modulated microglial and astrocytes activation, and a milder toxicity by cuprizone. Although further studies are required, it is suggested that LLLT represents a feasible therapy for demyelinating diseases.