| Spinal cord injury is a serious trauma of the central nervous system,and ramains an unsolved medical problem.With the progress of the research,it is found that the early high dosage of glucocorticoid delivery after spinal cord injury could not make the patient’s long-term benefit.Besides,the treatment also brings many complications,so it is no longer recommended as a routine treatment.Decompression followed by internal fixation is widely used in the clinical treatment of spinal cord injury for attenuating the compression of the spinal cord,but there are still many controversies in the time schedule of decompression and the benefit of treatment.Therefore,there is a lack of effective clinical treatment,and researchers have been trying to develop new methods for the management of spinal cord injury.As a non-invasive method,low-level laser has been widely used in the medical cosmetology and the joint disease management,because of its significant effect of inhibiting inflammation,analgesia and promoting tissue repair.Low-level laser has been shown to promote the recovery of stroke,peripheral nerve injury and neurodegenerative diseases.810 nm laser therapy was confirmed to accelerate the motor functional recovery of spinal cord injury animals,has a significant modulation effect of immunoinflammation after spinal cord injury.The treatment significantly reduced the expression levels of iNOS,IL-6 and also had the beneficial effect of promoting axonal regeneration.However,the detailed mechanism of the promoting effect is not clear.Inflammatory response is an important component of the secondary spinal cord injury.The peripheral blood derived macrophages and spinal cord resident microglia are considered to be the most important players involved in the inflammatory response after spinal cord injury.Recent studies have shown that the polarization of macrophages and microglia is critical for the repair of spinal cord injury.The microglia / macrophages polarization is regulated by the inflammatory microenvironment of the injured spinal cord.Since the low-level laser has a significant regulatory role of inflammation,so can low-level laser also modulate the macrophage polarization after spinal cord injury? To answer this question,the following two parts of the experimental studies were performed.Experiment 1: Effects of low level laser therapy on the polarization of macrophages / microglia after acute spinal cord injury in ratsObjective: To study the effects of low level laser therapy on the polarization of macrophages / microglia in rats after acute spinal cord injuryMethods: 48 rats were randomly assigned to the spinal cord injury group and the spinal cord injury combined with the laser treatment group.Rats in the low-level laser treatment group were received a 810 nm wavelength laser beam on the spinal cord injury lesion site with percutaneous method.The therapy paremeters were as follows: outpower of 150 mW,irradiation spot size of 0.3cm2.Single irradiation time was 50 min,1 time per day.Laser therapy was applied for consecutively 1 days,3 days,7 days or 14 days.At the above time points after irradiation,rat spinal cord tissue of the two groups was collected.To evaluate the polarization of macrophages / microglia at different time points after spinal cord injury,immunofluorescence staining and immunoblot assay were performed.Enzyme linked immunosorbent assay was used to detect the expression of interleukin-4 and interleukin-13 in the injured spinal cord.Results: The low-level laser therapy can significantly reduce the number of activated microglia / macrophages at day 3 and day 7.The therapy also decreased the expression of M1 macrophage and its biomarker iNOS in spinal cord injury at day 3 and day 7.Low-level laser therapy up regulated the expression of M2 macrophage and its biomarker Arg1 at day 7.Compared with the control group,the expression of IL-4 in the spinal cord was greater by day 3,day 7 and day 14 after laser therapy.The expression of IL-13 was up regulated at day 7.Conclusion: Low lever laser therapy can regulate the polarization of macrophages / microglia after spinal cord injury,which can decrease the expression of M1 macrophages,and up regulate the expression of M2 macrophages.This regulatory effect may be related to the up-regulation of IL-4 and IL-13 expression by laser therapy.Experiment 2: Effect of low-level laser therapy on the rehabilitation of acute spinal cord injury in ratsObjective: To investigate the effects of low level laser on the lesion size,survival of the neurons and locomotor functional recovery after spinal cord injury in ratsMethods: 62 rats were randomly assigned to the spinal cord injury group and the spinal cord injury combined with the laser treatment group.Rats in the low-level laser treatment group were received a 810 nm wavelength laser beam on the spinal cord injury lesion site with percutaneous method.The therapy paremeters were as follows: outpower of 150 mW,irradiation spot size of 0.3cm2.Single irradiation time was 50 min,1 time per day.Laser therapy was applied for consecutively 1 days,3 days,7 days or 14 days.At the above time points,BBB locomotor rating scale was used to evaluate the hindlimb motor function of the rats.Foot print test was carried out at 21 days after injury.At 3 days,7 days and 14 days post injury,injured spinal cord segement of rats were obtained for observing the gross appearance.Spinal cord slices were cut and HE staining was performed to evaluate the lesion length.The number of the survived neurons at the para injury site was measured with immunofluorescence staining.Lesion area was determined with Nissl staining.Results: The BBB scores of rats in the laser therapy group were significantly greater at 7 days and 14 day post injury.21 days post njury,the foot print analysis showed that the step length of the laser therapy group was greater than that of the control group.The step width and the rotation angle was smaller than that of the control group.HE staining showed that the lesion length in the laser therapy group was significantly shorter than that in the control at 7 days and 14 day post injury.Nissl staining showed that the lesion area in the laser therapy group was significantly lower than that of the control at 7 days and 14 days post injury.Immunofluorescence staining showed that the number of survived neurons in the para injury site was significantly greater at 3day,7 days and 14 days post injury.Conclusion: Low level laser therapy can reduce the lesion length and lesion area of spinal cord,increase the number of survived neurons in the pare injury site,and improve the locomotor functional recovery of the rats. |
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