Lasers Med Science, . 2017 Feb;32(2):343-349., doi: 10.1007/s10103-016-2120-7. Epub 2016 Dec 1.
Effects of different fluences of low-level laser therapy in an experimental model of spinal cord injury in rats
- PMID: 27909916 DOI: 10.1007/s10103-016-2120-7
The aim of this study was to evaluate the in vivo response of different fluences of low-level laser therapy (LLLT) on the area of the injury, inflammatory markers, and functional recovery using an experimental model of traumatic spinal cord injury (SCI). 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). SCI was performed by an impactor equipment (between the ninth and tenth thoracic vertebrae), with a pressure of 150 kdyn. Afterwards, the injured region was irradiated daily for seven consecutive sessions, using an 808-nm laser, at the respective fluence of each experimental groups. Motor function and tactile sensitivity were performed on days 1 and 7 post-surgery. Animals were euthanized on the eighth day after injury, and the samples were retrieved for histological and immunohistochemistry analyses. Functional evaluation and tactile sensitivity were improved after LLLT, at the higher fluence. Additionally, LLLT, at 750 and 1000 J/cm2, reduces the lesion volume and modulates the inflammatory process with decrease of CD-68 protein expression. These results suggest that LLLT at higher doses was effective in promoting functional recovery and modulating inflammatory process in the spinal cord of rats after SCI.
Keywords: Low-level laser therapy; Neuronal plasticity; Spinal cord injury; Wistar.
Lasers Med Science, 2014 Nov;29(6):1849-59., doi: 10.1007/s10103-014-1586-4. Epub 2014 May 24.
"Low-intensity laser therapy effect on the recovery of traumatic spinal cord injury"
- PMID: 24858233 DOI: 10.1007/s10103-014-1586-4
Scientific advances have been made to optimize the healing process in spinal cord injury. Studies have been developed to obtain effective treatments in controlling the secondary injury that occurs after spinal cord injury, which substantially changes the prognosis. Low-intensity laser therapy (LILT) has been applied in neuroscience due to its anti-inflammatory effects on biological tissue in the repairing process. Few studies have been made associating LILT to the spinal cord injury. The objective of this study was to investigate the effect of the LILT (GaAlAs laser-780 nm) on the locomotor functional recovery, histomorphometric, and histopathological changes of the spinal cord after moderate traumatic injury in rats (spinal cord injury at T9 and T10). Thirty-one adult Wistar rats were used, which were divided into seven groups: control without surgery (n = 3), control surgery (n = 3), laser 6 h after surgery (n = 5), laser 48 h after surgery (n = 5), medullar lesion (n = 5) without phototherapy, medullar lesion + laser 6 h after surgery (n = 5), and medullar lesion + laser 48 h after surgery (n = 5). The assessment of the motor function was performed using Basso, Beattie, and Bresnahan (BBB) scale and adapted Sciatic Functional Index (aSFI). The assessment of urinary dysfunction was clinically performed. After 21 days postoperative, the animals were euthanized for histological and histomorphometric analysis of the spinal cord. The results showed faster motor evolution in rats with spinal contusion treated with LILT, maintenance of the effectiveness of the urinary system, and preservation of nerve tissue in the lesion area, with a notorious inflammation control and increased number of nerve cells and connections. In conclusion, positive effects on spinal cord recovery after moderate traumatic spinal cord injury were shown after LILT.
Low-level laser therapy for spinal cord injury in rats: effects of polarization
The effects of laser polarization on the efficacy of near-infrared low-level laser therapy for spinal cord injury (SCI) are presented. Rat spinal cords were injured with a weight-drop device, and the lesion sites were directly irradiated with a linearly polarized 808-nm diode laser positioned either perpendicular or parallel to the spine immediately after the injury and daily for five consecutive days. Functional recovery was assessed daily by an open-field test. Regardless of the polarization direction, functional scores of SCI rats that were treated with the 808-nm laser irradiation were significantly higher than those of SCI alone group (Group 1) from day 5 after injury. The locomotive function of SCI rats irradiated parallel to the spinal column (Group 3) was significantly improved from day 10 after injury, compared to SCI rats treated with the linear polarization perpendicular to the spinal column (Group 2). There were no significant differences in ATP contents in the injured tissue among the three groups. We speculate that the higher efficacy with parallel irradiation is attributable to the deeper light penetration into tissue with anisotropic scattering.
Keywords: low-level laser therapy, photobiomodulation, polarization, spinal cord injury, functional evaluation
In spinal cord injury (SCI), complete or partial loss of autonomic, sensory, and motor functions is caused by interruption of neural signal conduction along the axonal tracts. There is generally poor recovery of these functions because of the difficulty of tissue regeneration in the central nervous system. Thus, SCI patients are left with serious residual disabilities, such as paralysis, respiratory difficulty, chronic pain, urinary problems, and neurologic decline, leading to considerable decrease in quality of life. Various strategies have been examined for repair of SCI in animal models, including blockage of the endogenous growth inhibitory factors,1,2 infusion of neurotrophic factors,3,4 and transplantation of growth promoting cells.5–7 However, no effective treatment for SCI has yet been established.
Low-level laser therapy (LLLT) is a promising approach to treat SCI. LLLT has been clinically applied to the treatment of rheumatoid arthritis and periodontal disease, pain management, and healing of wounds and burns.8–10 LLLT is also currently used for the treatment of various neurological diseases such as stroke, neurodegenerative diseases, and brain injury.11–16 Several studies have shown that near-infrared LLLT has the potential to be an effective noninvasive therapy for SCI.17–20 Rochkind et al. demonstrated that transplantation of embryonal spinal cord nerve cells followed by 780-nm laser irradiation enhanced axonal sprouting and spinal cord repair in a completely transected rat SCI model.17 In two different rat models of hemisection SCI and contusion SCI, Anders et al. transcutaneously applied an 810-nm laser, which penetrated to the depth of the injured spinal cord and promoted axonal regeneration and functional recovery.18,19 Their study demonstrated that near-infrared laser irradiation significantly suppressed immune cell activation and cytokine/chemokine expression, suggesting that a decrease in the inflammatory response is one of the recovery mechanisms in LLLT for spinal cord repair.
The detailed mechanisms of LLLT are still under investigation. However, the therapeutic efficacy relies fundamentally on the initial photochemical event, i.e., absorption of photons by photoacceptors or chromophores such as cytochrome c oxidase in the tissue.21,22 Karu et al. showed in an in vitro study that the basic processes of LLLT occurring in HeLa cells were light absorption and photochemistry but that the incident characteristics of photons, such as degree of light polarization, did not affect the biological reactions in LLLT.23 However, scattering of photons in vivo depends on the microstructure of tissue, and light propagation into biological tissue would therefore change the healing property. For instance, Ribeiro et al. investigated the repair of skin burns in rats with a linearly polarized He–Ne laser beam, which was parallel or perpendicular to the direction of the spinal column, at the same laser dose.24,25 Their results showed that the healing process was dependent on the polarization orientation; lesions irradiated with parallel polarization were completely repaired 17 days after wound creation, while those with perpendicularly polarized irradiation showed a moderate degree of healing in the same period. They attributed these results to the fact that the parallel polarization was aligned with the predominant orientation of collagen fibers in the dermis, which was confirmed by histological analysis. This alignment would reduce photon scattering and thus increase optical penetration depth in the tissue, leading to the acceleration and improvement of cutaneous wound repair.24
It is widely known that photon scattering by aligned cylindrical structures, such as myofibrils, axons, and collagen fibers, results in anisotropic light reflection and propagation in the tissue.26–30 These characteristics are often used for diagnosis of the tissue abnormalities and for mapping of specific structures in the tissue.31–33 Since the spinal cord has a fibrous structure, photon migration should be affected by polarization of incident light in the tissue. However, the effect of polarization on efficacy of LLLT for SCI has not been elucidated. In the present study, we examined the effect of relative orientation of laser polarization on efficacy of near-infrared LLLT for contused spinal cords in rats.