Abstract: BACKGROUND: There are many treatment methods for knee osteoarthritis, among which electroacupuncture, as an important non-drug treatment, is effective in the treatment of knee osteoarthritis, but its exact mechanism is not clear.
OBJECTIVE: Effect of electroacupuncture on the expression of p53 and P21 in articular cartilage and subchondral bone of aged rats with knee osteoarthritis.
METHODS: Eight 6-month-old male Sprague-Dawley rats were included in the young group and sixteen 24-month-old male Sprague-Dawley rats were randomly divided into old group (n=8) and electroacupuncture group (n=8). The rats in the electroacupuncture group received electroacupuncture stimulation once a day, 5 days a week, for 8 continuous weeks, and the other two groups did not do any treatment. Eight weeks later, the level of type II collagen C-terminal peptide in peripheral blood was detected by ELISA, the morphology of left knee cartilage and subchondral bone was observed by safranin O-fast green staining, the degree of knee cartilage degeneration was evaluated by modified Mankin’s score, the microstructure of left knee cartilage and subchondral bone was detected by micro-CT, and the expression levels of matrix metalloproteinase 13, P53, P21 mRNA and protein were detected by RT-PCR and western blot respectively.
RESULTS AND CONCLUSION: Compared with the young group, the level of C-terminal peptide of type II collagen in the peripheral blood was increased in the old group (P < 0.05). The micro-CT results showed that the bone volume fraction, bone mineral density and the number of bone trabeculae were decreased in the old group compared with the young group (P < 0.05), while the trabecular separation increased (P < 0.05). Safranin O-fast green staining showed that in the old group, the surface layer of cartilage was uneven with fissures, the morphology of chondrocytes was irregular and stained unevenly, the boundary between the cartilage and subchondral bone was blurred, and the matrix loss was serious. The Mankin’s score was higher in the old group than the young group (P < 0.05). The expression of matrix metalloproteinase 13, P53, P21 at mRNA and protein levels increased in the old group compared with the young group (P < 0.05). Compared with the old group, electroacupuncture decreased the level of C-terminal peptide of type II collagen (P < 0.05), increased the bone volume fraction, bone mineral density and the number of bone trabeculae (P < 0.05), and decreased the trabecular separation (P < 0.05). Safranin O-fast green staining showed that in the electroacupuncture group, the surface of cartilage was smooth and red staining was uniform, and the cell morphology and structure were between the young group and the old group. Following electroacupuncture treatment, the Mankin’s score (P < 0.05), matrix metalloproteinase 13 and P21 mRNA expression (P < 0.05), and matrix metalloproteinase 13 and P53 protein expression decreased (P < 0.05), while there was a decreasing trend of P53 mRNA and P21 protein expression, but with no statistical significance (P > 0.05). To conclude, electroacupuncture may delay articular cartilage degeneration and subchondral osteoporosis in aged rats by inhibiting the expression of P53 and P21, so as to protect joints and delay joint aging.

Key words: electroacupuncture, knee osteoarthritis, cartilage, subchondral bone, P53 protein, P21 protein