[Dynamic changes of matrix metalloproteinase 9 in heterotopic ossification of rat model].

OBJECTIVE

To explore the value of matrix metalloproteinase 9 (MMP-9) in predicting the occurrence of heterotopic ossification by observing the expression of MMP-9 in heterotopic ossification of the early trauma rat model.

METHODS

A total of 132 male Sprague Dawley rats, aged 4-5 weeks, weighing (135.0 ± 6.5) g, were randomly divided into experimental group and control group (n = 66). In experimental group, the Achilles tendon was cut off and clamped to prepare heterotopic ossification model; in control group, only Achilles tendon was exposed by making a incision. The general condition of the rats was observed after operation; at 2, 3, 4, 5, 6, 7, and 8 days after operation, the Achilles tendon tissue was harvested for gross observation, histological observation, and immunohistochemical staining observation; the serum and Achilles tendon tissue were harvested to detect the expressions of MMP-9 protein and mRNA by ELISA and RT-PCR. The X-ray films at 5 and 10 weeks and histological examination at 10 weeks after operation were used to observe heterotopic ossification.

RESULTS

All rats survived to the end of the experiment. The Achilles tendon had no significant change in control group at each time point, showing normal tendon structure. In experimental group, the hardness of Achilles tendon tissue gradually increased with the time; there were a large number of irregular connective tissue and cartilage cells; and immunohistochemical staining for MMP-9 was positive results. The MMP-9 protein and mRNA expression levels of experimental group were significantly higher than those of the control group at each time point (P < 0.05). MMP-9 protein and mRNA expression levels of experimental group showed an increasing tendency (P < 0.05). According to the results of X-ray films and histological observation, heterotopic ossification occurred at 10 weeks after operation in experimental group, but no heterotopic ossification was observed in control group.

CONCLUSION

In early heterotopic ossification of rat Achilles tendon, the expression of MMP-9 increases significantly, indicating that it has reference significance in predicting heterotopic ossification.