Abstract: BACKGROUND: Both in vivo and in vitro studies have shown that platelet-rich plasma plays an important role in promoting chondrocyte proliferation and tissue regeneration and repair. However, little is reported on the repair of cartilage defects with different concentrations of platelet-rich plasma in rabbits with knee osteoarthritis.
OBJECTIVE: To compare the different concentrations of platelet rich plasma in the repair of cartilage defects in rabbits with knee osteoarthritis, so as to provide theoretical basis and options for the clinical treatment of cartilage defects in knee osteoarthritis.
METHODS: A total of 50 healthy New Zealand white rabbits were randomly divided into blank group, model group, low concentration, medium concentration and high concentration groups of platelet-rich plasma with 10 rabbits in each group. Platelet-rich plasma was prepared by secondary centrifugation. An osteoarthritis model of rabbit knee was made by improved Hulth method in each group except for the blank group. In the model group, 0.3 mL of normal saline was injected into the articular cavity, while in the low, medium and high concentration groups, (1.0-1.2)×1012/L, (1.5-1.7)×1012/L, and (2.0-2.2)×1012/L platelet-rich plasma was injected respectively. The expression of tumor necrosis factor-α, interleukin-1β and interleukin-6 in the synovial fluid was detected by ELISA, and the histological changes of different concentrations of platelet-rich plasma were evaluated by hematoxylin-eosin staining, toluidine blue staining and Mankin’s pathological score. Western blot and RT-PCR were used to detect the protein and mRNA levels of type II collagen and aggrecan. The study protocol was approved by the Experimental Animal Ethics Committee of China Medical University.
RESULTS AND CONCLUSION: Compared with the model group, the levels of tumor necrosis factor-α, interleukin-1β and interleukin-6 in the low, middle and high concentration groups decreased to some extent (P < 0.05), the expression levels of these indicators in the middle concentration group were lower than those in the low concentration group and high concentration group (P < 0.05). Hematoxylin-eosin and toluidine blue staining results showed that chondrocytes in the low and high concentration groups were relatively regular in shape and the cell number increased. Chondrocytes in the medium concentration group were arranged neatly, with formation of cartilage-like cells, and a remarkable effect was found in the repair of chondrocytes. Mankin’s pathological scores were highest in the model group, followed by the low and high concentration groups, and lowest in the middle concentration group. Western blot and RT-PCR results showed that compared with the model group, the expression of type II collagen and aggrecan protein and mRNA in cartilage tissues were significantly increased in low, medium, and high concentration groups (P < 0.05). To conclude, different concentrations of platelet-rich plasma can effectively resist the expression of inflammatory factors involved in the process of knee osteoarthritis and has a significant effect on the repair of cartilage defects in knee osteoarthritis, and (1.5-1.7)×1012/L platelet-rich plasma has better effects.

Key words: platelet-rich plasma, osteoarthritis, cartilage defect, inflammatory factor, type II collagen, aggrecan