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Updated: Apr 19, 2026
Direct Mouse Trauma/Burn Model of Heterotopic Ossification
Published on: August 6, 2015
[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.
Insights
Matrix metalloproteinase 9 (MMP-9) expression significantly increases in early heterotopic ossification of rat Achilles tendons. This finding suggests MMP-9 is a valuable predictor for developing heterotopic ossification.
Area of Science:
- Biomedical research
- Orthopedics
- Tissue engineering
Background:
- Heterotopic ossification (HO) is the abnormal formation of bone in soft tissues, often occurring after trauma.
- Matrix metalloproteinase 9 (MMP-9) is an enzyme involved in tissue remodeling, but its role in early HO is not fully understood.
Purpose of the Study:
- To investigate the expression of MMP-9 in an early-stage rat model of Achilles tendon injury.
- To determine if MMP-9 expression can predict the development of heterotopic ossification.
Main Methods:
- A heterotopic ossification model was created in Sprague Dawley rats by surgically inducing Achilles tendon injury.
- MMP-9 protein and mRNA levels were measured using ELISA and RT-PCR at various time points post-operation.
- Histological analysis and X-rays were used to confirm the presence of heterotopic ossification.
Main Results:
- Rats in the experimental group showed increased Achilles tendon hardness and histological signs of early bone formation.
- Significantly elevated MMP-9 protein and mRNA levels were observed in the experimental group compared to controls.
- Heterotopic ossification was confirmed in the experimental group by 10 weeks post-operation.
Conclusions:
- Early-stage heterotopic ossification in rat Achilles tendons is associated with a significant increase in MMP-9 expression.
- MMP-9 shows potential as a predictive biomarker for the occurrence of heterotopic ossification.
