Cartilage degeneration of bilateral knee joint induced by unilateral articular injection of exogenous urokinase-type plasminogen activator in rabbits

AIM: To observe the effects of intra-articular injection of exogenous urokinase-type plasminogen activator (UPA) on cartilage. METHODS: The experiment was conducted in the Animal Experiment Center, Xinjiang Shihezi University from January 2005 to June 2006. The 48 rabbits were divided into experimental group (n =24) and blank control 4-week group (n =6) and saline control group (n =18) according to body mass and the sex. Rabbits in the experimental group were injected intraarticularly with 0.4 μg/0.2 mL UPA. Animals in the blank control group did not receive any treatment. Animals in the saline control group received 0.2 mL saline in right knee joint. 4, 8 and 12 weeks after establishing models, the rabbits were respectively sacrificed to obtain cartilage of both knee joints for histology observation and electron microscopy. RESULTS: A total of 48 rabbits were involved in the result analysis, and no infection occurred during experiment. ① The surface of the right and left kneel joint cartilage in experimental group showed irregularity, defection and structural breakage, the number of cartilage cell reduced and collagen fiber hyperplasia and tide line of complete break. ② Mankin's score showed that there was no change of cartilage in saline control group and blank control 4-week group (0.83±0.75,0.80±0.74,P 0.05). There were significant differences as compared with the experimental group at weeks 4, 8 and 12 (0.83±0.75,5.38±0.92;1.00±0.63,8.25±1.39;0.83±0.75,11.75±0.89;P 0.01). At the same time, there were significant differences in the experimental group at different time points (5.38±0.92,5.35±0.90;8.25±1.39,8.51±0.94;11.75±0.89,12.03±0.91;P 0.05). CONCLUSION: ① Findings of the trial showed pathological phenomenon of cartilage injury appeared in both knee joints of rabbits. ② UPA may be the initiation factor of cartilage degradation, and plays important pathological effects for degradation, and accelerates the severity of articular cartilage degradation.