| Objective:To study the effects of low intensity pulsed ultrasound (LIPUS) on chondrocytes proliferation and MMP-13 and typeâ…¡collagen of chondrocytes of rabbit's knee in vitro and discuss the effect and Mechanism of LIPUS to chondrocytes activity.Methods: The chondrocytes were obtained from knee joints of six one-month old rabbits. Each rabbit's chondrocytes were divided into 5 groups: control group and four LIPUS groups with the intensity of LIPUS is 20 mW /cm2, 30 mW /cm2, 40 mW /cm2, 50 mW /cm2 respectively. During the second cultured generation, the chondrocytes were irradiated by LIPUS for 20 minutes and cells were counted each day for 10 days. On the 0, 5th and 10th day, chondrocytes were collected and their protein and RNA were extracted for test of MMP-13 and typeâ…¡collagen content with Western-blot and qRT-PCR technique.Result: 1.Contrasting with control groups, the chondrocytes number were higher in each LIPUS groups(p<0.05) and the numbers were significantly higher in the 40 mW /cm2 group (p<0.05). 2. MMP-13 contents were higher in the 5th day and 10th day than in the 0 day(p<0.05). After irradiated 5 days and 10 days, the contents of MMP-13 in each LIPUS group were remarkable lower than control group(p<0.05) and 40 mW /cm2 group was the lowest (p<0.05). 3. After cultured 5 days and 10 days, typeâ…¡collagen contents were lower than the 0 day(p<0.05). The contents of typeâ…¡collagen in each LIPUS groups were remarkable higher than control groups(p<0.05) and 40 mW /cm2 group was the highest (p<0.05). 4. There was significantly negative correlation between MMP-13 and typeâ…¡collagen (r=-0.757,p<0.05).Conclusion: The 4 kinds of intensity of LIPUS could promote the chondrocyte activities of rabbit's knee and the effect is related to the chondrocyte proliferation and changes of MMP-13 and typeâ…¡collagen content in chondrocytes. Objective: This study was designed to establish rabbit knee OA models by Anterior Cruciate Ligament Transection (ACLT) surgery, and observed the effect of LIPUS irradiation on articular cartilage repair, chondrocytes proliferation and PI3K signal transduction pathway.Method: Thirty-six healthy New Zealand rabbits were divided into six groups: early control group (EC group), early OA group (EO group), early treatment group (ET group), medium-term control group (MC group), medium-term OA group (MO group) and medium-term treatment group (MT group). ACLT was performed in EO, ET, MO and MT groups. Animals in ET group received LIPUS irradiation 3 days after surgery, while the fifth week after surgery in MT group. Six weeks after irradiation, the rabbits were sacrificed respectively and observed for knee gross microscopy with Modified Mankin score, proliferating cell nuclear antigen (PCNA) and phosphatidylinositol-3-kinase (PI3K) with Western-blot technique.Result: Toluidine blue stain showed in ET group, the surface of articular cartilage were regular, normally stained and chondrocytes proliferation were observed. While in MT group, the surface of articular cartilage were irregular, TBS was reduced significantly, and the number of chondrocytes was decreased. Total Mankin score was significantly increased in EO group (EO vs. EC group, P <0.01) and reduced in ET group (ET vs. EO group, P <0.01). Total Mankin score in MO group was significantly higher than that in MC group (P <0.01). However, total Mankin score in MT group didn't significantly decrease compared with that in MO group (P >0.05). Western blot analysis showed that PCNA in EO group was significantly increased as compared with EC group (P <0.01), PCNA in ET group was significantly higher than that in EO group (P <0.01). PCNA in MO group and MT group was not significantly increased compared with that in MC group (P >0.05). PCNA in ET group was significantly increased as compared with that in MT group (P <0.01). Western blot analysis showed that phosphorylation of PI3K (p-PI3K) in EO group didn't significantly increase as compared with EC group (P >0.05). Phosphorylation of PI3K in ET group was significantly higher than that in EO group (P <0.01). There was no significant difference in PI3K phosphorylation between MT group and MO group (P >0.05).Conclusion: Early LIPUS intervention is beneficial to articular cartilage repair through promotion of chondrocytes proliferation in OA. The mechanism of action is closely associated with the effect of LIPUS in PI3K signal transduction pathway. Objective: This study was designed to observed the effect of LIPUS irradiation on typeâ…¡collagen, matrix metalloproteinase-13(MMP-13), mitogen-activated protein kinases(MAPKs) signal transduction pathway and articular cartilage repair on rabbits models in early stage of OA progression.Method: 18 healthy New Zealand rabbits were divided randomly into three groups: treat group (O+L group), control group (O+L group) and sham operation group (SO group), 6 in each group. In O+L group and O-L group, Surgical ACLT was performed in the right knee of rabbits. 3 days after surgery, all of the rabbits were received LIPUS irradiation, and sacrificed respectively 6 week later. Modified Mankin score, typeâ…¡collagen, MMP-13 and MAPKs were observed.Result: Modified Mankin score: compared with SO group, O+L group, O-L group were significant high (P<0.05,P<0.01); and compared with O+L group score in O-L group was also significant high (P<0.05). Western-blot analysis: typeâ…¡c ollagen in O+L group and O-L group were significant lower than that in SO group (P<0.05), but no difference between O+L group and O-L group. Compared with SO group, MMP -13 in both O+L and O-L group were significant high and compared with O+L group, MMP-13 in O-L was significant high (P<0.05). Compared with SO group, p-ERK1/2 and p-p38 in both O+L and O-L group were significant high, and higher in O-L group (P<0.01); compared with O+L group, p-ERK1/2, p-p38 in O-L group was significant high (P<0.05); p-JNK showed no difference in all three groups.Conclusion: Early LIPUS intervention relieved damage in articular cartilage of OA. The mechanism may closely associate with the effect of LIPUS reducing MMP-13, p38 and ERK1/2 contents of articular cartilage.
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