The Effects of Laser Moxibustion on Knee Osteoarthritis Pain in Rats

Abstract

Background: Although chronic pain affects the quality of life of patients with osteoarthritis, current medical treatments are either ineffective or have long-term side effects. Recently, low-intensity laser irradiation of corresponding acupoints was demonstrated to alleviate pain. Objective: The aim of the present study was to investigate the effects of 10.6 μm laser moxibustion on a monosodium iodoacetate (MIA)-induced knee osteoarthritis pain model. Methods: Thirty-two rats were randomly assigned to four groups: Saline, MIA, MIA+Laser, and MIA+Sham Laser. The 10.6 μm laser was used to irradiate the ST35 for 10 min once a day for a total of seven applications. The paw withdrawal mechanical threshold and weight-bearing difference were performed to evaluate the analgesic effects of laser moxibustion. At the end of the experiment on days 28, the joint histology, the levels of metalloproteinases-13 (MMP-13) in the cartilage, and TNF-α, IL-1β, and IL-6 in the synovial membrane were measured to determine the chondroprotection and anti-inflammatory effect of laser moxibustion. Results: Early laser moxibustion significantly reversed the MIA-induced mechanical hyperalgesia and weight-bearing difference, especially on the 28th day (p < 0.001). Moreover, laser moxibustion prevented the articular pathological lesions and cartilage destruction on days 28 (p < 0.01). Remarkably, the levels of cartilage MMP-13, and synovial TNF-α, IL-1β, and IL-6 also decreased on day 28 (p < 0.05) after the early treatment of laser moxibustion. Conclusions: 10.6 μm laser moxibustion may have long-lasting analgesic, anti-inflammatory, and chondroprotection effects, suggesting that it may emerge as a potential therapeutic strategy for the chronic pain treatment of osteoarthritis.

Keywords: chronic pain; knee osteoarthritis; laser moxibustion.

FIG. 1.

Effects of laser moxibustion (a) on MIA-induced mechanical hyperalgesia and (b) weight-bearing asymmetry. Data are presented as mean ± SD (n = 8) and analyzed using two-way ANOVA for repeated measurement. *p < 0.05 and **p < 0.001 compared to MIA group; ^#p < 0.05 and ^##p < 0.001 compared to MIA+Sham Laser group. MIA, monosodium iodoacetate; SD, standard deviation.

FIG. 2.

Effects of laser moxibustion on MIA-induced articular pathological degeneration. (a) The joint histology image of HE and SO staining (40 × ). (b) Histopathologic assessment of cartilage classified using the OARSI scoring system. Data are presented as mean ± SD (n = 4) and analyzed using Kruskal–Wallis test. *p < 0.01 and **p < 0.001 compared to saline group; ^##p < 0.001 compared to MIA group; ^&&p < 0.001 compared to MIA+Sham Laser group. HE, hematoxylin and eosin; OARSI, Osteoarthritis Research Society International; SO, Safranin O.

FIG. 3.

Effects of laser moxibustion on the expression of MMP-13 in MIA-induced KOA rats. (a) Immunohistochemical staining was used to identify the expression of MMP-13 in the articular cartilage (200 × ). (b) Histogram of the AOD value of MMP-13 expression among the four groups. Data are presented as mean ± SD (n = 4) and analyzed using one-way ANOVA. *p < 0.01 compared to saline group; ^#p < 0.01 compared to MIA group; ^&p < 0.01 compared to MIA+Sham Laser group. AOD, average optical density; KOA, knee osteoarthritis; MMP-13, metalloproteinases-13.

FIG. 4.

Effects of laser moxibustion on the level of TNF-α, IL-1β, and IL-6 in the synovium of MIA-induced KOA rats. The concentrations of (a) TNF-α, (b) IL-1β, and (c) IL-6 in the synovium were measured in four groups. Data are presented as mean ± SD (n = 4) and analyzed using one-way ANOVA. *p < 0.05 compared to saline group; ^#p < 0.05 compared to MIA group; ^&p < 0.05 compared to MIA+Sham Laser group.