Abstract
Dorsal root ganglia (DRG) are vulnerable to physical injury of the intervertebral foramen, and chronic compression of the DRG (CCD) an result in nerve root damage with persistent morbidity. The purpose of this study was to evaluate the effects of low level laser therapy (LLLT) on the DRG in a CCD model and to determine the mechanisms underlying these effects. CCD rats had L-shaped stainless-steel rods inserted into the fourth and fifth lumbar intervertebral foramen, and the rats were then subjected to 0 or 8 J/cm2 LLLT for 8 consecutive days following CCD surgery. Pain and heat stimuli were applied to test for hyperalgesia following CCD. The levels of TNF-α, IL-1β and growth-associated protein-43 (GAP-43) messenger RNA (mRNA) expression were measured via real-time PCR, and protein expression levels were analyzed through immunohistochemical analyses. Our data indicate that LLLT significantly decreased the tolerable sensitivity to pain and heat stimuli in the CCD groups. The expression levels of the pro-inflammatory cytokines TNF-α and IL-1β were increased following CCD, and we found that these increases could be reduced by the application of LLLT. Furthermore, the expression of GAP-43 was enhanced by LLLT. In conclusion, LLLT was able to enhance neural regeneration in rats following CCD and improve rat ambulatory behavior. The therapeutic effects of LLLT on the DRG during CCD may be exerted through suppression of the inflammatory response and induction of neuronal repair genes. These results suggest potential clinical applications for LLLT in the treatment of compression-induced neuronal disorders.
Highlights
Lower back pain with sciatica is a common symptom associated with many diseases of the lumbosacral spine, such as herniated intervertebral disc and degenerative disc diseases, and can result in functional disability
level laser therapy (LLLT) suppresses the chronic compression of the DRG (CCD)-induced expression of inflammatory cytokines The inflammatory response is important for CCD-mediated hyperalgesia, and previous studies by our group and others have shown that LLLT may reduce this response [22,24]
Following dorsal root ganglion (DRG) compression for 8 days, the levels of tumor necrosis factor alpha (TNF-a) and interleukin-1 beta (IL-1b) messenger RNA (mRNA) of the CCD group were significantly increased within the DRG compared with the Control group (p,0.05)
Summary
Lower back pain with sciatica is a common symptom associated with many diseases of the lumbosacral spine, such as herniated intervertebral disc and degenerative disc diseases, and can result in functional disability. One of the major causes of this symptom is a narrowing of the intervertebral foramen accompanied by compression of the dorsal root ganglion (DRG) [1]. One of the major causes of pain in degenerative lumbar spinal disease is mechanical compression of the DRG, which can lead to molecular-based irritation involving the localized release of inflammatory cytokines [3]. It has been demonstrated that herniated disc tissues release IL-1b, which affects the somatosensory neural response at the dorsal root level [5]. Previous studies have shown that TNF-a in the nucleus pulposus plays an important role in radicular pain and that sensory neurons display increased sensitivity to TNF-a in a rat CCD model [6,7]
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