跑步运动对大鼠不稳定膝关节软骨的影响

Effects of running exercise on cartilage in rats with an unstable knee joint

目的研究跑步运动对大鼠不稳定膝关节软骨的影响。方法将20只切断膝关节前交叉韧带的8周龄SD大鼠按随机数字表法分为自由活动组（对照组）和跑步训练组（实验组），每组10只大鼠，2组再根据处死取材时间分为造模成功3周和6周各2个亚组，每个亚组5只大鼠。实验组按15m／min强度进行跑步训练，每天训练1h；对照组自由活动，不接受任何干预。于造模成功3周和6周后采用苏木精一伊红（HE）、甲苯胺蓝及免疫组化染色、透射电镜等方法分别观察和比较2组大鼠膝关节的软骨厚度、Mankin评分、蛋白多糖含量、软骨基质Ⅱ型胶原含量及软骨形态结构。结果造模成功6周后，2组大鼠关节软骨的厚度和Mankin评分与组内造模成功3周后比较，差异均有统计学意义（P〈0．05）；造模成功3周和6周后，实验组软骨厚度分别为（154±13）μm和（131±15）μm，Mankin评分分别为（9．93±1．36）分和（11．23．±1．57）分，分别与对照组同时间点比较，差异均有统计学意义（P〈0．05）。造模成功6周后，2组大鼠膝关节软骨甲苯胺蓝染色阳性光密度与组内造模成功3周后比较，差异有统计学意义（P〈0．05）；造模成功3周和6周后，实验组甲苯胺蓝染色阳性光密度分别与对照组同时间点比较，差异均有统计学意义（P〈0．05）。造模成功6周后，2组大鼠膝关节软骨Ⅱ型胶原纤维免疫组化染色阳性光密度与组内造模成功3周后比较，差异有统计学意义（P〈0．05）；造模成功3周和6周后，实验组Ⅱ型胶原纤维免疫组化染色阳性光密度分别与对照组同时间点比较，差异均有统计学意义（P〈0．05）。造模成功3周后，实验组透射电镜显示软骨细胞减少，软骨表面有部分断裂；造模成功6周后，实验组透射电镜可见软骨表面多处有破损，软骨细胞坏死。结论跑步运动对不稳定膝关节软骨具有破坏效应，可加重关节损伤和软骨基质的破坏，加速软骨细胞的退行性变。

Objective To investigate the effect of running exercise on cartilage in rats with an unstable knee joint. Methods Twenty 8-week-old Sprague-Dawley rats had their left anterior cruciate ligament cut to model an unstable knee. They were randomly divided into a control group and an experimental group, 10 rats in each group. The control group was given no intervention, while the experimental group accepted running exercise training on na animal treadmill at a velocity of 15 m/min for an hour every day. After 3 and 6 weeks of training, 5 rats were sacri- ficed and cartilage from the medial condyle of the femur was sampled, decalcificated, embedded and sliced on the sagittal plane. After hematoxylin-eosin staining, tolnidine blue staining and immunohistochemical staining, the carti- lage thickness, Mankin＇ score, the content of matrix collagen and the proteoglycan content of the cartilage matrix were assessed, and the shape and structure of the unstable knee joints were observed under a transmission electron micro- scope. Results The cartilage thicknesses and Mankin＇s scores at 6 weeks were significantly different from those at 3 weeks in both groups. In the experimental group the average thickness of cartilage was 154 ± 13 μm at 3 weeks and 131 ± 15 μm at 6 weeks. The corresponding Mankin＇s scores were 9.93± 1.36 and 11.23 ± 1.57, respectively. Both were significantly different from the control group averages at the same time points. There was also a significant difference in the positive rate of toluidine blue and collagen type Ⅱ staining between the experimental group and the control group at both time points, and in the experimental group between 3 and 6 weeks of training. After 3 weeks of training, fewer chondrocytes were observed under the transmission electron microscope in the experimental group, and fissures were seen on the surface of the cartilages. However, 3 weeks later, quite a few ruptures and a lot of necrotic ceils could be seen. Conclusions Running exercise can damage the cartilage of unstable knee joints and speed up the development of osteoarthritis. Even moderate exercise could aggravate damage to unstable joints and the cartilage matrix, and accelerate chondrocyte degeneration.