The Optical Parameter Optimization And Evaluation Of Low-level Laser Therapy In Spinal Cord Injury Rat Models

Posttraumatic nerve repair continues to be a major challenge of rehabilitationmedicine. Although enormous progress has been made in surgical techniques over the pastthree decades, functional recovery after a severe lesion of a peripheral nerve. but thecentral nervous system curative effect is not satisfactory after injury while oppressionfactors can be surgically remove such as fracture, spinal canal stenosis, intracranialhematoma, etc. LLLT has also been shown to biomodulate processes in the nervoussystem, which caused a significant improvement of animals’ nerve regeneration andneurological function. As a promising treatment, Lower-Lever power laser therapy waslittle research in the repair of spinal cord injury (SCI). Thus to establish the Allen’s spinalcord injury rat model and screen the appropriate light wavelength which can penetratedeep into the body reach to the surface of spinal cord. Then the appropriate parameters ofLLLT was screened by measuring the penetrating power and tissues temperature change.Objective:(1) Select the appropriate light wavelength which is screened using awide spectrum spectrum analyzer and penetrates to the depth of the spinal cord to radiate. To establish the Allen’s spinal cord injury rat model and measure power penetration thatwas transmitted through all of the layers of tissue between the dorsal skin surface and theventral side of the spinal cord, then to measure the temperature change of the skin andspinal cord tissue of irradiated site. Preliminary screening of irradiation parametersthrough the above.(2) Screening of irradiation parameters were performed to the spinalcord injury rat which were performed to the dorsal surface and observe its curative effect,to determine if application of the proposed parameters is effective.Methods:(1)24Sprague-Dawley rats were randomly divided into3groups:Transmission spectrum analysis group (n=6), Power penetration analysis group (n=6), andTemperature analysis group (n=12). In addition to transmission spectrum group, all rat’swas employed to Allen’s spinal cord injury model，Then measured from penetrating powerfrom the skin to spinal cord were measured after suturing the wounds and then1mwpower were selected as the irradiation treatment power. Secondly, temperature analysisdevices were respectively placed in rat irradiated site subcutaneously and spinal cordinjury sit, the changes of tissue temperature were tested and then to determine the time fortherapy.(2)92Sprague-Dawley rats were randomly divided into3groups：normal controlgroup (n=6), spinal cord injury without treatment group(Control group, n=43) and withirradiation treatment group (n=43). Low-level laser light was applied directly to the lesionsite for14days consecutively according to the irradiation parameters selection after spinalcord injury. then hindlimb motor function BBB scales and footprint analysis wereperformed on1、3、7、14、21day and Hematoxylin and Eosin staining were used toevaluate the syringomyelia area after infusion. Then determine the quantity of the neuronnear the injury area. The expression of IL-1β and IL-6was detected by ELISA method at3h,6h,24h,3d and7d post-injury.Results:810nm light reach to the surface of spinal cord with the most penetratingpower, the1mw penetration power can be detected by the power meter at spot area of0.2cm2, output power of100mw that output is1%approximately when reaching to thesurface of spinal cord. While the rise of temperature in subcutaneous does not exceed4℃and spinal cord tissue does not exceed2℃during irradiation1020s.(2) The selected parameters were irradiated treatment group after spinal cord injury. At7d,14dand21days of spinal cord injury, the motor function recovery in irradiated group wassignificantly better than the control (P <0.05), and syringomyelia area in irradiated groupwas also obviously smaller than the control group (P <0.05). We found that IL-1β and IL-6which have maximum expression at3hours post-injury or earlier were not found to bealtered by LLLT at3,6,12,24hours post-injury. The statistically altered of IL-6wasfound of at the time of3d,7d (P<0.05) and IL-1β was found of at the time of3d (P<0.05)compared with SCI group. There was no significant difference between control and LLLTgroups in expression of IL-1β post injury7d.Conclusion:810nm,100mw, spot area of0.2cm2,510J/cm2（500mw/cm2×1020s）were effective parameter through screening, which can significantly reduce thesyringomyelia area after spinal cord injury and significantly promote motor functionrecovery.