Exercise effects on pain relief and extracellular matrix production in a rat model of intervertebral disc degeneration / 中国组织工程研究

ABSTRACT

BACKGROUND: Exercise has been proved to accelerate the proliferation of intervertebral disc cells and extracellular matrix production in healthy rats. For the degenerative intervertebral disc, whether exercise also has positive effects on its cell proliferation, extracellular matrix production or pain relief remains unclear. OBJECTIVE: To investigate the effect of exercise on the extracellular matrix production in a rat model of intervertebral disc degeneration.METHODS: A rat model of intervertebral disc degeneration was prepared by Freund's complete adjuvant injection into the intervertebral disc at L5-6 levels. Then, the model rats were allowed to have a rest for 2 weeks. All rats were then randomly divided into exercise and control groups. Rats in the exercise group were forced to run every day, while the controls allowed free activities in the cage. The behavioral tests were performed at 7, 14, 28, 42, 56 and 70 days after modeling; meanwhile, the intervertebral disc samples were collected used for alcian blue staining and immunohistochemical staining to detect the levels of proteoglycan, aggrecan and collagen type Ⅱ in the intervertebral disc cells, respectively.RESULTS AND CONCLUSION: Vocalization threshold on the rat back of punctured disc was significantly decreased, while grooming and wet-dog shaking were significantly increased at 7 days after modeling compared with the baseline (P < 0.05), suggesting that Freund's complete adjuvant injection successfully induces disc degeneration, hyperalgesia and abnormal behaviors. Further, the vocalization threshold and wet-dog shaking in the exercise group showed significant improvement compared with the control group after 14 days of exercise (P < 0.05), while the grooming was significantly reduced until the 28th day (P < 0.01), indicating that exercise can alleviate pain caused by disc degeneration in model rats. At 21 days after modeling, the levels of proteoglycan, aggrecan and collagen type Ⅱ in the nucleus pulposus and annulus fibrosus were significantly decreased compared with the baseline (P < 0.01), indicating the occurrence of disc degeneration. After 14 days of training, the levels of proteoglycan, aggrecan, and collagen type Ⅱ in the nucleus pulposus and annulus fibrosus in the exercise group were significantly increased compared with the control group (P < 0.01). Moreover, after 8-week exercise, the level of proteoglycan in the nucleus pulposus and annulus fibrosus in the exercise group was increased by 4-5 times compared with the control group, and levels of aggrecan and collagen type Ⅱ in the nucleus pulposus in the exercise group also was increased by 3-4 times compared with the control group. To conclude, exercise can promote extracellular matrix increased by production by increasing the levels of proteoglycan, aggrecan, and collagen type II in the degenerative intervertebral disc.