Effect of low intensity pulsed ultrasound on expression of TIMP-2 in serum and expression of mmp-13 in articular cartilage of rabbits with knee osteoarthritis

Objective: To study the effect of low intensity pulsed ultrasound (LIPUS) on the expression of tissue inhibitor of metalloproteinase-2 (TIMP-2) in the serum and expression of matrix metallopeptidase 13 MMP-13) in the articular cartilage cells of rabbits with knee osteoarthritis (OA). Methods: Inner patellar ligament defect method was used to establish the model of knee OA. Four weeks after the modeling, the arterial blood was drawn from the ear of each rabbit, while ELISA was employed to detect the expression of TIMP-2 in the serum. The chondrocytes were separated from animals in each group and then cultured in vitro. All rabbits were divided into control group, OA model group and OA + LIPUS group. Cells in the control and OA groups were not treated, while cells in the OA+ LIPUS group were treated with LIPUS (40 mW/cm(2), 1 time/day). Cells were collected 7 d later and the RNA and total protein were extracted respectively. Real-time PCR and Western blotting were employed to analyze the expression of MMP-13 in chondrocytes at the mRNA and protein level, respectively. Results: The success rate of establishment of OA model was 83%. The results of ELISA showed that the content of TIMP-2 in the serum of animals with OA was 22.3%, lower than the one in the control group (P<0.05). Compared with the normal control group, the expression of TIMP-2 in the OA model group was significantly increased, while the expression of MMP-13 was significantly increased (P<0.05). After the stimulation of LIPUS, the expression of TIMP-2 and MMP-13 was close to the one in the normal control group. Conclusions: The inner patellar ligament defect method is a mature method to establish the rabbit OA model, with high success rate. The expression of serum TIMP-2 in the OA model group is significantly decreased. LIPUS can up-regulate TIMP-2 and down-regulate MMP-13.