Dynamic expression of matrix metalloproteinases 2, 9 and 13 in ovariectomy-induced osteoporosis rats

Abstract

The aim of the present study was to examine the dynamic expression of matrix metalloproteinase (MMP)-2, MMP-9 and MMP-13 in an ovariectomy (OVX)-induced osteoporosis rat model. A total of 80 Sprague-Dawley female rats (age, 3 months) were randomly divided into the OVX and sham groups, with 40 rats in each group. Rats in the sham group received sham surgery, while the remaining rats were ovariectomized. After 12, 16, 20 and 24 weeks, 10 rats from each group were randomly sacrificed, respectively. It was observed that the bone mineral density (BMD) and the trabecular bone area in the OVX group were significantly lower as compared with those in the sham group (P<0.01). The expression levels of MMP-2 and MMP-9 were negatively correlated with the BMD, while MMP-13 was positively correlated with the BMD. The expression levels of MMP-2 and MMP-9 increased more abruptly and were significant higher in the OVX group in comparison with those in the sham group between 12 and 24 weeks after surgery (P<0.01). More specifically, the MMP-9 mRNA expression level in the OVX group increased abruptly between 12 and 24 weeks after surgery. By contrast, in the sham group, the MMP-9 mRNA level was undetectable between 12 and 16 weeks, and increased steadily between 16 and 24 weeks. Furthermore, the mRNA and protein expression levels of MMP-13 initially increased and then decreased in the OVX group (P<0.01 vs. the sham group), whereas they continuously increased in the sham group between 12 and 24 weeks after surgery. In conclusion, MMP-2, MMP-9 and MMP-13 regulated the development of osteoporosis, and MMP-9 may be used as an important marker in the early diagnosis of osteoporosis.

Keywords: MMP-13; MMP-2; MMP-9; bone resorption; osteoporosis.

Figure 1.

Trabecular bone morphology examined by hematoxylin and eosin staining. Sham group at (A) 12, (B) 16, (C) 20 and (D) 24 weeks after surgery. OVX group at (E) 12, (F) 16, (G) 20 and (H) 24 weeks after surgery. Magnification, ×200. OVX, ovariectomy.

Figure 2.

BMD in the right femur of the sham and OVX groups, examined by dual-energy X-ray absorptiometry. (A) Bar graphs and (B) line chart with error bars representing the mean ± standard deviation. **P<0.01 vs. sham group. OVX, ovariectomy; BMD, bone mineral density.

Figure 3.

Relative mRNA expression levels of (A) MMP-2, (B) MMP-9 and (C) MMP-13 in the sham and OVX groups were investigated by reverse transcription-quantitative polymerase chain reaction. Bar graphs and line charts are shown, with error bars representing the mean ± standard deviation. *P<0.05, **P<0.01 vs. sham group. MMP, matrix metalloproteinase; OVX, ovariectomy.

Figure 4.

Relative protein expression levels of MMP-2, MMP-9 and MMP-13 in the two groups were investigated by western blotting. (A) Representative protein bands of the MMP proteins are shown. (B) MMP-2, (C) MMP-9 and (D) MMP-13 protein levels demonstrated as bar graphs, with error bars representing the mean ± standard deviation. **P<0.01 vs. sham group. MMP, matrix metalloproteinase; OVX, ovariectomy.