Abstract: BACKGROUND: Studies have reported that the combined use of ginger extract to reduce the levels of serum pro-inflammatory cytokines, including interleukin-1β, interleukin-6, tumor necrosis factor-α,  is related to the reduction of cartilage injury in knee osteoarthritis.
OBJECTIVE: To observe the protective effect of red ginger extract on articular cartilage and the expression of serum interleukin-1β, interleukin-6, tumor necrosis factor-α and cartilage tissue type II collagen α1 mRNA in rats with early knee osteoarthritis, and to explore the protective effect of red ginger extract on articular cartilage of rats with early knee osteoarthritis and its possible mechanism.
METHODS: Fifty SPF Sprague-Dawley rats were randomly divided into blank group, model group, low-dose red ginger, high-dose red ginger and positive control group (n=10 per group). Except for the blank group, the rats in the other four groups were used to prepare knee osteoarthritis models by intraarticular injection of 4% papain 0.2 mL+0.03 mol/L L-cysteine mixed solution. The rats in the blank and model groups were fed routinely, and the low-dose red ginger, high-dose red ginger and positive control groups were given 50 mg/kg red ginger extract aqueous solution, 100 mg/kg red ginger extract aqueous solution and 18 mg/kg celecoxib capsule aqueous solution respectively. All the interventions were conducted once a day, for 4 continuous weeks. Four weeks after treatment, the rats in each group were killed and the knee joints were stained with safranin O-fast green. The articular cartilage was scored by Mankin scoring. The expression levels of interleukin-1β, interleukin-6, tumor necrosis factor-α in serum and type II collagen α1 mRNA in cartilage were detected. The study protocol was approved by the Animal Ethics Committee of Guangzhou University of Chinese Medicine, with an approval No. 20190917002.
RESULTS AND CONCLUSION: The pathological section of knee cartilage showed that there was cartilage matrix loss in the model and each treatment group, and the Mankin score of each treatment group was significantly higher than that of the blank group (P < 0.05) and lower than that of the model group (P < 0.05). There was no significant difference between the high-dose group and the positive control group (P > 0.05), but the scores of the two groups were lower than that of the low-dose group. The levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α were upregulated in the positive control group, high-dose red ginger group and low-dose red ginger group compared with the blank group and down-regulated compared with the model group (P < 0.05). Moreover, and the levels of these cytokines were ranked as follows: positive control group < high-dose red ginger group < low-dose red ginger group (P < 0.05). The level of type II collagen α1 mRNA in cartilage showed no significant difference between the blank group and the high-dose red ginger group and the positive control group (P > 0.05), whereas the expression of type II collagen α1 mRNA was significantly increased in the model group and low-dose red ginger group compared with the other three groups (P < 0.05). To conclude, red ginger extract may protect the articular cartilage of knee osteoarthritis by inhibiting interleukin-1β, interleukin-6, and tumor necrosis factor-α, thereby delaying the development of knee osteoarthritis. Compared with the low-dose group, high-dose red ginger extract has better anti-inflammatory effect.

Key words: knee osteoarthritis, red ginger, inflammatory cytokine, cartilage, rat, model, animal