Electroacupuncture for chronic pain in a model of knee arthritis / 中国组织工程研究

ABSTRACT

BACKGROUND:Acupuncture has been found to be effective for alleviating low back pain and acute pain due to knee arthritis, but its effect on chronic pain is under discussion. OBJECTIVE:To investigate the mechanism underlying electroacupuncture (EA) alleviating chronic pain in a New Zealand rabbit model of knee arthritis. METHODS:(1) Thirty-two New Zealand rabbits were selected, and the knee osteoarthritis model was established by injecting 4% papain into the knee articular cavity of rabbit's bilateral hind limbs. The model rabbits were randomly divided into four groups (n=8 per group) normal saline plus EA, normal saline plus sham EA, nor-Binaltorphimine (nor-BNI) plus EA, and nor-BNI plus sham EA groups. The dosage of nor-BNI was 1 mg/kg, once daily, for consecutive 3 days. 30-minute EA was given at 2 hours after administration, once daily, until the day the rabbits were killed. Sham EA indicated no given electric current. The behaviors of the lower limbs were evaluated by Basso, Beattie, Bresnahan scores. The rabbits were respectively killed at 1, 3, 5 and 7 days after administration, the spinal cord was separated, and then fixed with formaldehyde. The expression levels of interleukin-17, interleukin-17 receptor A and NR1 in the spinal cord tissues were detected by immunofluorescence. (2) The other 24 New Zealand rabbits were randomly divided into model and control groups (n=12 per group), and the knee osteoarthritis model was established in the former group. Afterwards, the two groups were randomized into two subgroups, followed by given the intrathecal administration of normal saline, or 2 μg interleukin-17 antibody serum dissolvedin 10 μL normal saline, once daily, for consecutive 3 days. The behaviors of the lower limbs were evaluated by Basso, Beattie, Bresnahan scores, and the expression levels of p-NR1 and interleukin-17 receptor were detected by western blot assy. RESULTS AND CONCLUSION:The Basso, Beattie, Bresnahan scores in the nor-BNI plus EA group were significantly increased, while the expression levels of interleukin-17, interleukin-17 receptor A and NR1 in the spinal cord tissues were significantly decreased (P 0.05). After administration of interleukin-17 antibody serum, the Basso, Beattie, Bresnahan scores in the model group was significantly increased, and the expression levels of interleukin-17 and NR1 in the spinal cord tissues were significantly decreased, but still significantly higher than those in the control subgroups (P< 0.05). These results suggest that chronic pain in knee arthritis is the result of an increase in the expression level of NRI induced by interleukin-17. EA can remarkably improve the pain in the model rabbits of knee arthritis by downregulating interleukin-17 in the spinal cord tissues, rather than interleukin-17 receptor.